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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
, Available online ,
doi: 10.12170/20220424003
Abstract:
Geotechnical centrifuge model test is an advanced technology to study the key issues of composite foundation. The centrifugal modelling of rigid pile composite foundation under saturated clay condition is complex and has numbers of influencing factors, which should be paid enough attention to. Based on the analysis of the preparation process of centrifuge model of several groups of rigid pile composite foundation, this paper discusses the influence of 1g pile insertion modelling on the shear strength of the foundation model. It shows that the disturbance of sample preparation of centrifugal model foundation is related to the way of pile insertion, and it is beneficial to reduce the disturbance of sample preparation to guide a hole before inserting the pile. The undrained shear strength of the clay model foundation will be weakened during the molding process under 1g. The comparative analysis shows that the disturbance of pile insertion and the model preparation under 1g are the main reasons for the strength loss of the saturated foundation model. The reduction of shear strength of upper soft soil of composite foundation is greater than that of the lower bearing layer. The similarity of stress history of the soil samples should be fully considered in the centrifugal model comparison test. An ideal centrifuge modelling procedure of rigid pile composite foundation is proposed, which provides an important reference for improving the refinement level of geotechnical centrifugal model test.
Geotechnical centrifuge model test is an advanced technology to study the key issues of composite foundation. The centrifugal modelling of rigid pile composite foundation under saturated clay condition is complex and has numbers of influencing factors, which should be paid enough attention to. Based on the analysis of the preparation process of centrifuge model of several groups of rigid pile composite foundation, this paper discusses the influence of 1g pile insertion modelling on the shear strength of the foundation model. It shows that the disturbance of sample preparation of centrifugal model foundation is related to the way of pile insertion, and it is beneficial to reduce the disturbance of sample preparation to guide a hole before inserting the pile. The undrained shear strength of the clay model foundation will be weakened during the molding process under 1g. The comparative analysis shows that the disturbance of pile insertion and the model preparation under 1g are the main reasons for the strength loss of the saturated foundation model. The reduction of shear strength of upper soft soil of composite foundation is greater than that of the lower bearing layer. The similarity of stress history of the soil samples should be fully considered in the centrifugal model comparison test. An ideal centrifuge modelling procedure of rigid pile composite foundation is proposed, which provides an important reference for improving the refinement level of geotechnical centrifugal model test.
, Available online ,
doi: 10.12170/20220419001
Abstract:
Scour is one of the key factors that should be considered in the design process of offshore wind turbine (OWT) monopile foundations. However, the geometry of local scour pit and embedded length-to-diameter ratio of pile (L/D) are always ignored in practice, which leads to a conservative design. A three-dimensional finite element model for OWT monopile considering the geometry of local scour pit and L/D was utilized to study its lateral bearing behaviors under the existence of local scour pit. Furthermore, a simplified beam-spring model for monopile with small L/D was proposed to predict the lateral responses of monopile under local scour and validation is also made. The results show that the lateral behaviors of monopile with low L/D are sensitive to the scour pit’s depth. With the increment of scour depth, the contribution of soil resistance components such as base reaction force and vertical shaft shear force to the pile foundation's horizontal bearing capacity also increases. The typical API p-y curve method that only considers lateral soil resistance will no longer apply to the analysis of scoured monopile foundation, and the influence of pile base effect shall be taken into account. The research results could be provided for reference in practice of OWT foundation design and analysis.
Scour is one of the key factors that should be considered in the design process of offshore wind turbine (OWT) monopile foundations. However, the geometry of local scour pit and embedded length-to-diameter ratio of pile (L/D) are always ignored in practice, which leads to a conservative design. A three-dimensional finite element model for OWT monopile considering the geometry of local scour pit and L/D was utilized to study its lateral bearing behaviors under the existence of local scour pit. Furthermore, a simplified beam-spring model for monopile with small L/D was proposed to predict the lateral responses of monopile under local scour and validation is also made. The results show that the lateral behaviors of monopile with low L/D are sensitive to the scour pit’s depth. With the increment of scour depth, the contribution of soil resistance components such as base reaction force and vertical shaft shear force to the pile foundation's horizontal bearing capacity also increases. The typical API p-y curve method that only considers lateral soil resistance will no longer apply to the analysis of scoured monopile foundation, and the influence of pile base effect shall be taken into account. The research results could be provided for reference in practice of OWT foundation design and analysis.
, Available online ,
doi: 10.12170/20221108001
Abstract:
Pinglu Canal is the largest river sea connecting canal in China for hundreds of years. The construction of Pinglu Canal will have a positive and far-reaching impact on regional social and economic development. Based on the construction and operation management practice of Xijiang Golden Waterway, as well as the enlightenment brought by Lingqu Canal and Beijing Hangzhou Grand Canal, this paper analyzes the core issues and key technical issues that need to be highlighted in the construction of the Pinglu Canal, and puts forward the overall plan for the overall construction of the Pinglu Canal Project, starting with the construction goals, construction guidelines, construction concepts, functional planning, and the principal dimensions of the waterway and ship lock levels. The analysis and research results can provide technical reference for the final determination of Pinglu Canal construction scheme, and can also provide reference for the planning and construction of similar canal projects in China in the future.
Pinglu Canal is the largest river sea connecting canal in China for hundreds of years. The construction of Pinglu Canal will have a positive and far-reaching impact on regional social and economic development. Based on the construction and operation management practice of Xijiang Golden Waterway, as well as the enlightenment brought by Lingqu Canal and Beijing Hangzhou Grand Canal, this paper analyzes the core issues and key technical issues that need to be highlighted in the construction of the Pinglu Canal, and puts forward the overall plan for the overall construction of the Pinglu Canal Project, starting with the construction goals, construction guidelines, construction concepts, functional planning, and the principal dimensions of the waterway and ship lock levels. The analysis and research results can provide technical reference for the final determination of Pinglu Canal construction scheme, and can also provide reference for the planning and construction of similar canal projects in China in the future.
, Available online ,
doi: 10.12170/20211115001
Abstract:
In order to discuss the mechanical properties and fracture characteristics of dam concrete, three-point bending test of concrete beam was carried out based on two different concrete mix ratios (named C0.48 and C0.43 respectively according to different moisture content) provided by a hydraulic complex project and on-site coarse and fine aggregates. The relevant mechanical properties such as slump, compressive strength and splitting strength were determined, and the effects of different mixing ratios on fracture parameters such as fracture surface, cracking load and instability load, critical effective crack length and double K fracture toughness were analyzed. The test results show that, the collapse of C0.48 concrete is greater than that of C0.43 concrete. The compressive strength and splitting strength of C0.48 concrete are lower than that of C0.43 concrete. The coarse aggregate of C0.48 concrete fracture surface is not obvious as that of C0.43 concrete. The cracking load, destabilization load, critical effective crack length and fracture toughness of C0.43 concrete are higher than those of C0.48 concrete, which indicates that C0.43 concrete has high strength, good ductility and good toughness.
In order to discuss the mechanical properties and fracture characteristics of dam concrete, three-point bending test of concrete beam was carried out based on two different concrete mix ratios (named C0.48 and C0.43 respectively according to different moisture content) provided by a hydraulic complex project and on-site coarse and fine aggregates. The relevant mechanical properties such as slump, compressive strength and splitting strength were determined, and the effects of different mixing ratios on fracture parameters such as fracture surface, cracking load and instability load, critical effective crack length and double K fracture toughness were analyzed. The test results show that, the collapse of C0.48 concrete is greater than that of C0.43 concrete. The compressive strength and splitting strength of C0.48 concrete are lower than that of C0.43 concrete. The coarse aggregate of C0.48 concrete fracture surface is not obvious as that of C0.43 concrete. The cracking load, destabilization load, critical effective crack length and fracture toughness of C0.43 concrete are higher than those of C0.48 concrete, which indicates that C0.43 concrete has high strength, good ductility and good toughness.
, Available online ,
doi: 10.12170/20220217001
Abstract:
Reservoir bank collapse is a geological environmental disaster phenomenon with time-space boundary attributes. Time boundary refers to the time span, including long-term and short-term bank collapse. Space boundary refers to different reservoir sections. Differences in bank collapse patterns and prediction parameters are caused by differences in geological environmental conditions. At present, the short-term prediction time span of reservoir bank collapse commonly used is 2 to 10 years, but for engineering applications, there is a lack of sufficient decision-making basis, which brings difficulties to practical applications. Based on the characteristics of the reservoir water storage process, this paper proves that the selection of the short-term prediction time for bank collapse can be defined according to the time period of the reservoir water storage process. From the perspective of large-scale reservoir projects such as the Three Gorges and Xiaolangdi, the definition method is scientific and reasonable. And a decision-making flow chart for the time-space boundary of bank collapse prediction is designed. The decision-making theory of time-space boundary is applied to the short-term bank collapse prediction of Malianhe Reservoir in Gansu, and the decision-making process of its time-space boundary is expounded in detail. And from the perspective of engineering geology, suggestions are provided for the application of short-term bank collapse prediction results.
Reservoir bank collapse is a geological environmental disaster phenomenon with time-space boundary attributes. Time boundary refers to the time span, including long-term and short-term bank collapse. Space boundary refers to different reservoir sections. Differences in bank collapse patterns and prediction parameters are caused by differences in geological environmental conditions. At present, the short-term prediction time span of reservoir bank collapse commonly used is 2 to 10 years, but for engineering applications, there is a lack of sufficient decision-making basis, which brings difficulties to practical applications. Based on the characteristics of the reservoir water storage process, this paper proves that the selection of the short-term prediction time for bank collapse can be defined according to the time period of the reservoir water storage process. From the perspective of large-scale reservoir projects such as the Three Gorges and Xiaolangdi, the definition method is scientific and reasonable. And a decision-making flow chart for the time-space boundary of bank collapse prediction is designed. The decision-making theory of time-space boundary is applied to the short-term bank collapse prediction of Malianhe Reservoir in Gansu, and the decision-making process of its time-space boundary is expounded in detail. And from the perspective of engineering geology, suggestions are provided for the application of short-term bank collapse prediction results.
, Available online ,
doi: 10.12170/20220527002
Abstract:
Axial zoned concrete-faced rockfill dam (CFRD) divides the dam shell along the dam axis into bank slope area, transition area and central area. By filling different modulus materials in turn to form gradient modulus along the axis of the dam, the three-dimensional centralization deformation and the axial displacement of the dam shell can be reduced, which can improve the deformation compatibility of dam body and the extrusion failure problem of high CFRD can be solved. According to the principle of face slab rupture of high CFRD, several reference indexes of face slab rupture problem (F-indexes) during the impoundment period are selected, including the deflection and the axial displacement of the face slab, the compressive stress of the elevation near the maximum deflection of the face slab, the settlement and axial displacement of the dam body. Based on a 200 m level CFRD project, the F-index of axial zoned CFRD with 36 kinds of modulus gradient combination were studied by numerical simulation. The effects of axial zoned CFRD design and modulus influence of axial zoned CFRD were analyzed. The results show that in 50% gradient scheme, the axial displacement of dam body decreases 12.76% to the left bank and 14.73% to the right bank, the settlement decreases 14.42%. The deflection of the face slab decreases 15.28%, the extreme value of axial compressive stress of the face slab is reduced by 11.35%. The study provides a new idea for solving the problem of slab rupture of high CFRDs.
Axial zoned concrete-faced rockfill dam (CFRD) divides the dam shell along the dam axis into bank slope area, transition area and central area. By filling different modulus materials in turn to form gradient modulus along the axis of the dam, the three-dimensional centralization deformation and the axial displacement of the dam shell can be reduced, which can improve the deformation compatibility of dam body and the extrusion failure problem of high CFRD can be solved. According to the principle of face slab rupture of high CFRD, several reference indexes of face slab rupture problem (F-indexes) during the impoundment period are selected, including the deflection and the axial displacement of the face slab, the compressive stress of the elevation near the maximum deflection of the face slab, the settlement and axial displacement of the dam body. Based on a 200 m level CFRD project, the F-index of axial zoned CFRD with 36 kinds of modulus gradient combination were studied by numerical simulation. The effects of axial zoned CFRD design and modulus influence of axial zoned CFRD were analyzed. The results show that in 50% gradient scheme, the axial displacement of dam body decreases 12.76% to the left bank and 14.73% to the right bank, the settlement decreases 14.42%. The deflection of the face slab decreases 15.28%, the extreme value of axial compressive stress of the face slab is reduced by 11.35%. The study provides a new idea for solving the problem of slab rupture of high CFRDs.
, Available online ,
doi: 10.12170/20220405002
Abstract:
Scientifically assessing the efficiency of industrial green water resources and identifying its driving factors is one of the important ways to resolve the contradiction between supply and demand of water resources, promote industrial green transformation, and promote ecological protection and high-quality development in the Yellow River Basin. Based on the super efficiency EBM model of undesirable output, this paper takes nine provinces (regions) in the Yellow River Basin as the research object to calculate the industrial green water resources efficiency in the Yellow River Basin from 2010 to 2019. Secondly, GML index was used to analyze the dynamic change of industrial green water efficiency. Finally, the driving factors of industrial green water resources efficiency are explored through the geographical detector model. The results show that the overall mean value of industrial green water resources efficiency in the Yellow River Basin from 2010 to 2019 is only 0.585, which does not reach the effective state, but shows a steady upward trend. There are obvious differences in the efficiency values among provinces, with Shaanxi province having the highest efficiency and Ningxia province having the lowest efficiency, and showing a pattern of “the east is greater than the west”. The improvement of GML index of industrial green water efficiency in the Yellow River Basin is driven by both the technical progress index and the technical efficiency index. Nature, society, economy and environment are the primary driving factors of industrial green water resources efficiency in the Yellow River Basin, and the level of scientific and technological innovation, industrial water intensity and population quality are the strongest secondary driving factors.
Scientifically assessing the efficiency of industrial green water resources and identifying its driving factors is one of the important ways to resolve the contradiction between supply and demand of water resources, promote industrial green transformation, and promote ecological protection and high-quality development in the Yellow River Basin. Based on the super efficiency EBM model of undesirable output, this paper takes nine provinces (regions) in the Yellow River Basin as the research object to calculate the industrial green water resources efficiency in the Yellow River Basin from 2010 to 2019. Secondly, GML index was used to analyze the dynamic change of industrial green water efficiency. Finally, the driving factors of industrial green water resources efficiency are explored through the geographical detector model. The results show that the overall mean value of industrial green water resources efficiency in the Yellow River Basin from 2010 to 2019 is only 0.585, which does not reach the effective state, but shows a steady upward trend. There are obvious differences in the efficiency values among provinces, with Shaanxi province having the highest efficiency and Ningxia province having the lowest efficiency, and showing a pattern of “the east is greater than the west”. The improvement of GML index of industrial green water efficiency in the Yellow River Basin is driven by both the technical progress index and the technical efficiency index. Nature, society, economy and environment are the primary driving factors of industrial green water resources efficiency in the Yellow River Basin, and the level of scientific and technological innovation, industrial water intensity and population quality are the strongest secondary driving factors.
, Available online ,
doi: 10.12170/20220406001
Abstract:
The complex coupling relationship exists between water resources, economic society and ecological environment, and promoting the coupling and coordination of the three is an important prerequisite for achieving sustainable regional development. Based on the coupling coordination degree model, this paper measures the coupling coordination degree of water resources-economic society-ecological environment system in 14 cities and states of Gansu Province from 2010 to 2019, and analyzes the evolution characteristics of the coupling coordination degree by combining with the evolution model of center of gravity. The results show that (1) the overall water resources-economic society-ecological environment comprehensive evaluation index of Gansu Province showed a slight upward trend during 2010-2019, and its spatial distribution was consistent with the distribution pattern of water resources endowment, economic and social development and ecological environment management in each city and state; (2) the coupling coordination degree of the three systems in Gansu Province is between [0.52,0.54], which belonged to the basic coordination type, the spatial dimension of the coupling coordination type of each city (state) was either stable or improving; (3) the trajectory of the center of gravity of the coupling coordination degree from 2010 to 2019 was mainly in Lanzhou City, with an average annual distance of 7.19 km. A differentiated strategy should be adopted to promote the evolution of water resources-economic society-ecological environment towards advanced coupling coordination.
The complex coupling relationship exists between water resources, economic society and ecological environment, and promoting the coupling and coordination of the three is an important prerequisite for achieving sustainable regional development. Based on the coupling coordination degree model, this paper measures the coupling coordination degree of water resources-economic society-ecological environment system in 14 cities and states of Gansu Province from 2010 to 2019, and analyzes the evolution characteristics of the coupling coordination degree by combining with the evolution model of center of gravity. The results show that (1) the overall water resources-economic society-ecological environment comprehensive evaluation index of Gansu Province showed a slight upward trend during 2010-2019, and its spatial distribution was consistent with the distribution pattern of water resources endowment, economic and social development and ecological environment management in each city and state; (2) the coupling coordination degree of the three systems in Gansu Province is between [0.52,0.54], which belonged to the basic coordination type, the spatial dimension of the coupling coordination type of each city (state) was either stable or improving; (3) the trajectory of the center of gravity of the coupling coordination degree from 2010 to 2019 was mainly in Lanzhou City, with an average annual distance of 7.19 km. A differentiated strategy should be adopted to promote the evolution of water resources-economic society-ecological environment towards advanced coupling coordination.
, Available online ,
doi: 10.12170/20220103003
Abstract:
During the operation period, the aqueduct experiences the cyclic fatigue effect of temperature variation for long term, which may cause the deterioration of the concrete of the aqueduct, such as micro-crack, and gradually reduce the safety degree of the aqueduct. There is no specific design-code for aqueduct design, and other relevant design-codes don’t provide clear guidance on whether to consider thermal effects for aqueduct. Taking a rectangle aqueduct in Xinjiang as an example and through the finite element software, the aqueduct temperature field is obtained and its distribution law is analyzed. Furthermore, the applicability of vertical temperature gradient pattern recommended by bridge codes in aqueduct design is discussed. The results show that the maximum vertical positive temperature difference in summer is 35.8 ℃ when the aqueduct is running, and 24.5 ℃ when the aqueduct is not running. In winter, the maximum vertical negative temperature difference is −15.1 ℃ when running water, and −7.8 ℃ when not running. The maximum transverse positive temperature difference of the aqueduct is 18.5 ℃ and the maximum transverse negative temperature difference is 11.2 ℃. Large vertical and transverse temperature gradient will produce large temperature stress, which should be taken into account in design. The vertical temperature gradient of the example is similar to the vertical temperature gradient modes recommended by various bridge codes, but there are large differences in the characteristic values, indicating that the recommended values of the bridge codes may not be directly applied to the temperature stress analysis of the aqueduct. The temperature field of aqueduct should be calculated and determined according to the structural form and operation conditions of the aqueduct.
During the operation period, the aqueduct experiences the cyclic fatigue effect of temperature variation for long term, which may cause the deterioration of the concrete of the aqueduct, such as micro-crack, and gradually reduce the safety degree of the aqueduct. There is no specific design-code for aqueduct design, and other relevant design-codes don’t provide clear guidance on whether to consider thermal effects for aqueduct. Taking a rectangle aqueduct in Xinjiang as an example and through the finite element software, the aqueduct temperature field is obtained and its distribution law is analyzed. Furthermore, the applicability of vertical temperature gradient pattern recommended by bridge codes in aqueduct design is discussed. The results show that the maximum vertical positive temperature difference in summer is 35.8 ℃ when the aqueduct is running, and 24.5 ℃ when the aqueduct is not running. In winter, the maximum vertical negative temperature difference is −15.1 ℃ when running water, and −7.8 ℃ when not running. The maximum transverse positive temperature difference of the aqueduct is 18.5 ℃ and the maximum transverse negative temperature difference is 11.2 ℃. Large vertical and transverse temperature gradient will produce large temperature stress, which should be taken into account in design. The vertical temperature gradient of the example is similar to the vertical temperature gradient modes recommended by various bridge codes, but there are large differences in the characteristic values, indicating that the recommended values of the bridge codes may not be directly applied to the temperature stress analysis of the aqueduct. The temperature field of aqueduct should be calculated and determined according to the structural form and operation conditions of the aqueduct.
, Available online ,
doi: 10.12170/20220426003
Abstract:
To reveal the horizontal bearing characteristics of composite bucket foundation in silty sand, the finite element software is used in this paper, and the numerical model is verified by the results of centrifugal model test. Main conclusions are as follows: on the front side the distribution of earth pressure is arched and earth pressure at the bottom is reduced, on the rear side the earth pressure distribution is roughly triangular, and the earth pressure on the bucket wall in vertical load direction is close to the static earth pressure. There is a linear relationship between the bucket wall earth pressure and cosθ (the angle between the calculation point and the load direction). With the increment of load level, the rotation center of composite bucket foundation moves up and to the load direction, and as the load reaches bearing capacity, the rotation center is located at bucket tip. The aspect ratio of composite bucket foundation does not affect the motion law of the rotation center, and the effect of rotation center on the vertical position of rotation center is obviously greater than that on the horizontal position. Results provide a reference for optimal structural design of the foundation.
To reveal the horizontal bearing characteristics of composite bucket foundation in silty sand, the finite element software is used in this paper, and the numerical model is verified by the results of centrifugal model test. Main conclusions are as follows: on the front side the distribution of earth pressure is arched and earth pressure at the bottom is reduced, on the rear side the earth pressure distribution is roughly triangular, and the earth pressure on the bucket wall in vertical load direction is close to the static earth pressure. There is a linear relationship between the bucket wall earth pressure and cosθ (the angle between the calculation point and the load direction). With the increment of load level, the rotation center of composite bucket foundation moves up and to the load direction, and as the load reaches bearing capacity, the rotation center is located at bucket tip. The aspect ratio of composite bucket foundation does not affect the motion law of the rotation center, and the effect of rotation center on the vertical position of rotation center is obviously greater than that on the horizontal position. Results provide a reference for optimal structural design of the foundation.
, Available online ,
doi: 10.12170/20220704001
Abstract:
At present, the flood evacuation path in emergency plan for reservoir dam safety management was based on short time and short distance principles, which are usually static paths and cannot be dynamic with the dam-break flood routing. The BREACH-MIKE21 coupling model was used to simulate the dam-break flood routing to obtain the dam-break flood submergement information, and combine the road network model to built environmental scenario model. The ant colony algorithm was used to optimize the flood evacuation path, and through adding backtracking, introducing the maximum and minimum ant colony system, improving the heuristic function to improve the optimization ability and convergence speed. By analyzing flood submergence elements frame by frame, the dam-break flood information is integrated into the algorithm, and the optimal flood evacuation path is finally obtained. The simulation results show that: (1) Under the same inundation scenario, compared with the basic ant colony algorithm, the average running time of the improved ant colony algorithm is increased by 1.6‰, the accuracy is increased by 32%, the average convergence times is reduced by 10.13 times, the convergence speed is faster and the optimization ability is stronger. (2) The optimal dynamic flood avoidance path obtained by the improved ant colony algorithm based on the evolution of dam-break flood is safer than the static path. The results of this study is suit for the requirements of emergency plan for reservoir dam safety management on dynamic process of flood avoidance transfer path, improving the efficiency of emergency transfer and reducing the impact of dam-break flood
At present, the flood evacuation path in emergency plan for reservoir dam safety management was based on short time and short distance principles, which are usually static paths and cannot be dynamic with the dam-break flood routing. The BREACH-MIKE21 coupling model was used to simulate the dam-break flood routing to obtain the dam-break flood submergement information, and combine the road network model to built environmental scenario model. The ant colony algorithm was used to optimize the flood evacuation path, and through adding backtracking, introducing the maximum and minimum ant colony system, improving the heuristic function to improve the optimization ability and convergence speed. By analyzing flood submergence elements frame by frame, the dam-break flood information is integrated into the algorithm, and the optimal flood evacuation path is finally obtained. The simulation results show that: (1) Under the same inundation scenario, compared with the basic ant colony algorithm, the average running time of the improved ant colony algorithm is increased by 1.6‰, the accuracy is increased by 32%, the average convergence times is reduced by 10.13 times, the convergence speed is faster and the optimization ability is stronger. (2) The optimal dynamic flood avoidance path obtained by the improved ant colony algorithm based on the evolution of dam-break flood is safer than the static path. The results of this study is suit for the requirements of emergency plan for reservoir dam safety management on dynamic process of flood avoidance transfer path, improving the efficiency of emergency transfer and reducing the impact of dam-break flood
, Available online ,
doi: 10.12170/20211029002
Abstract:
Dongting Lake area is one of the areas with frequent flood disasters in China. With the increasing frequency of extreme weather in recent years, it is of great practical significance to study the flood control situation of Dongting Lake area under historical extreme floods. Taking the floods of the Yangtze River in 1870, 1935 and 1954 as the research object, by establishing a one-dimensional and two-dimensional coupled hydrodynamic model of the Yangtze River, Dongting Lake and flood storage and detention area, the water level and excess flood in Dongting Lake area are simulated under the conditions of existing topography and engineering measures. The results show that under the condition of compensation operation of the Three Gorges and upstream reservoirs, if the floods in 1870, 1935 and 1954 occur, the excess flood volume near Jingjiang River and Chenglingji decreases significantly. Combined with the application of flood storage and detention areas in Jingjiang area and Chenglingji area, Dongting Lake area can safely spend the flood. The regulation and storage of the Three Gorges reservoir has greatly reduced the peak discharge of Zhicheng, the peak discharge of the the three rivers in Southern Jingjiang has also decreased, and the water level of each station in Dongting Lake area has decreased. The application of flood diversion in the flood storage and detention area has reduced the water level of Lianhuatang, increased the water surface gradient of Jingjiang River, and further reduced the peak flow of the three rivers in Southern Jingjiang. Due to the reduction of upstream water and downstream water level, the water level in the lake area has further decreased. By quantitatively predicting the flood control situation of the middle reaches of the Yangtze River and Dongting Lake area, it provides a scientific basis for the governance of Dongting Lake and lays a foundation for improving the management ability of flood control and disaster reduction in the lake area.
Dongting Lake area is one of the areas with frequent flood disasters in China. With the increasing frequency of extreme weather in recent years, it is of great practical significance to study the flood control situation of Dongting Lake area under historical extreme floods. Taking the floods of the Yangtze River in 1870, 1935 and 1954 as the research object, by establishing a one-dimensional and two-dimensional coupled hydrodynamic model of the Yangtze River, Dongting Lake and flood storage and detention area, the water level and excess flood in Dongting Lake area are simulated under the conditions of existing topography and engineering measures. The results show that under the condition of compensation operation of the Three Gorges and upstream reservoirs, if the floods in 1870, 1935 and 1954 occur, the excess flood volume near Jingjiang River and Chenglingji decreases significantly. Combined with the application of flood storage and detention areas in Jingjiang area and Chenglingji area, Dongting Lake area can safely spend the flood. The regulation and storage of the Three Gorges reservoir has greatly reduced the peak discharge of Zhicheng, the peak discharge of the the three rivers in Southern Jingjiang has also decreased, and the water level of each station in Dongting Lake area has decreased. The application of flood diversion in the flood storage and detention area has reduced the water level of Lianhuatang, increased the water surface gradient of Jingjiang River, and further reduced the peak flow of the three rivers in Southern Jingjiang. Due to the reduction of upstream water and downstream water level, the water level in the lake area has further decreased. By quantitatively predicting the flood control situation of the middle reaches of the Yangtze River and Dongting Lake area, it provides a scientific basis for the governance of Dongting Lake and lays a foundation for improving the management ability of flood control and disaster reduction in the lake area.
, Available online ,
doi: 10.12170/20211224001
Abstract:
In the waterway regulation and river regulation projects, in order to promote the deposition of the beach and protect the beach, combined with the characteristics of guide plate structure and permeable structure, a new beach protection structure-perforated deposit-plate is proposed in this study. In order to further analyze the siltation promoting and sediment retaining effect of perforated silt promoting plate, its flow characteristics are deeply studied. Based on the RNG k- ε turbulence model, a three-dimensional numerical model of perforated deposit-promoting plate is established, and the numerical model is verified by the physical model test data of perforated plate under the action of water flow. The effects of different flow velocity, percentage of opening area and relative single hole area on the flow velocity and deceleration rate around the perforated deposit-promoting plate are calculated and analyzed, and the prediction empirical formulas of the optimal percentage of opening area and the optimal single hole area are fitted. The results show that the relative single hole area has little effect on the flow pattern in front of the plate, but has an effect on the velocity flow pattern behind the plate and the formation of deceleration zone. The larger the percentage of opening area, the worse the deceleration effect behind the plate. When the percentage of opening area is 30%, the deceleration effect near the bottom is the strongest. The inflow velocity will affect the deceleration effect of the perforated deposit-promoting plate, and the deceleration effect is the best when the inflow velocity is 0.2 m/s.
In the waterway regulation and river regulation projects, in order to promote the deposition of the beach and protect the beach, combined with the characteristics of guide plate structure and permeable structure, a new beach protection structure-perforated deposit-plate is proposed in this study. In order to further analyze the siltation promoting and sediment retaining effect of perforated silt promoting plate, its flow characteristics are deeply studied. Based on the RNG k- ε turbulence model, a three-dimensional numerical model of perforated deposit-promoting plate is established, and the numerical model is verified by the physical model test data of perforated plate under the action of water flow. The effects of different flow velocity, percentage of opening area and relative single hole area on the flow velocity and deceleration rate around the perforated deposit-promoting plate are calculated and analyzed, and the prediction empirical formulas of the optimal percentage of opening area and the optimal single hole area are fitted. The results show that the relative single hole area has little effect on the flow pattern in front of the plate, but has an effect on the velocity flow pattern behind the plate and the formation of deceleration zone. The larger the percentage of opening area, the worse the deceleration effect behind the plate. When the percentage of opening area is 30%, the deceleration effect near the bottom is the strongest. The inflow velocity will affect the deceleration effect of the perforated deposit-promoting plate, and the deceleration effect is the best when the inflow velocity is 0.2 m/s.
, Available online ,
doi: 10.12170/20220614002
Abstract:
In recent years, the phenomenon of clogging of drainage board and sharp reduction of drainage performance due to clumping of fine soil particles around the drainage board has been found in vacuum pre-pressing projects, which is called “soil column effect”. Currently this phenomenon mostly occurs in soft foundation treatment projects dealing with newly dredged and blow-filled silt, and it is not common to see in naturally deposited soft soils. Based on the slow consolidation of deep soft soils encountered in a soft foundation treatment project in the Songnen Plain, this paper carries out a numerical analysis based on the “soil column effect” and gives the attenuation coefficient through the inverse analysis of the permeability coefficient in the soil column area, and concludes that the “soil column effect” can also occur in naturally deposited soft soils when specific conditions are met, which is due to the influence of comprehensive factors such as the high water content of soft soils, strong mobility, and the unsuitability of the particle size gradation and the aperture of the drainage board.
In recent years, the phenomenon of clogging of drainage board and sharp reduction of drainage performance due to clumping of fine soil particles around the drainage board has been found in vacuum pre-pressing projects, which is called “soil column effect”. Currently this phenomenon mostly occurs in soft foundation treatment projects dealing with newly dredged and blow-filled silt, and it is not common to see in naturally deposited soft soils. Based on the slow consolidation of deep soft soils encountered in a soft foundation treatment project in the Songnen Plain, this paper carries out a numerical analysis based on the “soil column effect” and gives the attenuation coefficient through the inverse analysis of the permeability coefficient in the soil column area, and concludes that the “soil column effect” can also occur in naturally deposited soft soils when specific conditions are met, which is due to the influence of comprehensive factors such as the high water content of soft soils, strong mobility, and the unsuitability of the particle size gradation and the aperture of the drainage board.
, Available online ,
doi: 10.12170/20220111001
Abstract:
Concrete is the most widely-used structure materials, and modern concrete is produced with a low water to binder ratio and high binder materials content to obtain high performances, leading to a significant increase in autogenous shrinkage (AS), and thus triggering a large tensile stress under restraint and further a serious early-age cracking, which deteriorates the concrete durability, shortens the service life and causes an incalculable loss, especially in hydraulic mass concrete and thin-walled concrete structures. This paper reviewed the literatures on the latest achievements and progress home and abroad for AS and its regulation in recent years, summarizing and comparatively analyzing the latest achievements and progress upon methods and devices for AS "time-zero" and deformation measurement, AS prediction models and AS regulation techniques, pointing out the flaws in current research and giving the further research direction on some key problems, and setting a reference for practical engineering and further AS study.
Concrete is the most widely-used structure materials, and modern concrete is produced with a low water to binder ratio and high binder materials content to obtain high performances, leading to a significant increase in autogenous shrinkage (AS), and thus triggering a large tensile stress under restraint and further a serious early-age cracking, which deteriorates the concrete durability, shortens the service life and causes an incalculable loss, especially in hydraulic mass concrete and thin-walled concrete structures. This paper reviewed the literatures on the latest achievements and progress home and abroad for AS and its regulation in recent years, summarizing and comparatively analyzing the latest achievements and progress upon methods and devices for AS "time-zero" and deformation measurement, AS prediction models and AS regulation techniques, pointing out the flaws in current research and giving the further research direction on some key problems, and setting a reference for practical engineering and further AS study.
, Available online ,
doi: 10.12170/20221023002
Abstract:
After the arch dam is built and impounded, the change of water environment will change the mechanical properties of rock mass in the dam site area, and then cause valley shrinkage, affecting the safety of the dam. Aiming at the abnormal deformation of the foundation of Jinping Ⅰ arch dam at the initial stage of impoundment, based on the law of rock mass deterioration in water and the basic theory of unsaturated seepage stress coupling, this paper establishes a model of rock mass deterioration in water, uses nonlinear finite element numerical analysis method to study the valley deformation law under the rock mass deterioration in the reservoir area at the initial stage of impoundment, and further analyzes the impact of valley contraction on the dam structure. The study shows that the deterioration of rock mass on the reservoir bank has a direct impact on valley deformation. The higher the deterioration degree of rock mass, the more obvious the valley width shrinkage, and the valley deformation in the upstream fluctuation zone of the dam body is the most prominent. With the increase of water level, the deterioration range of reservoir bank rock mass expands, and the maximum displacement along the river, the maximum principal tensile stress and the maximum principal compressive stress of the dam body slightly decrease. Therefore, valley deformation caused by rock mass deterioration after impoundment of Jinping Arch Dam will not affect the overall safety of the dam.
After the arch dam is built and impounded, the change of water environment will change the mechanical properties of rock mass in the dam site area, and then cause valley shrinkage, affecting the safety of the dam. Aiming at the abnormal deformation of the foundation of Jinping Ⅰ arch dam at the initial stage of impoundment, based on the law of rock mass deterioration in water and the basic theory of unsaturated seepage stress coupling, this paper establishes a model of rock mass deterioration in water, uses nonlinear finite element numerical analysis method to study the valley deformation law under the rock mass deterioration in the reservoir area at the initial stage of impoundment, and further analyzes the impact of valley contraction on the dam structure. The study shows that the deterioration of rock mass on the reservoir bank has a direct impact on valley deformation. The higher the deterioration degree of rock mass, the more obvious the valley width shrinkage, and the valley deformation in the upstream fluctuation zone of the dam body is the most prominent. With the increase of water level, the deterioration range of reservoir bank rock mass expands, and the maximum displacement along the river, the maximum principal tensile stress and the maximum principal compressive stress of the dam body slightly decrease. Therefore, valley deformation caused by rock mass deterioration after impoundment of Jinping Arch Dam will not affect the overall safety of the dam.
, Available online ,
doi: 10.12170/20211007002
Abstract:
The maximum particle size of earth-rockfill dam soil in engineering is between 200~1 000 mm, whereas the maximum particle size for laboratory test is usually 60 mm. Therefore, the original gradation needs to be scaled to meet the requirement of laboratory test. Based on this, this research investigates the applicable conditions of different scale methods, so that the compactness of test material is closest to original gradation. Firstly, the three characteristics of maximum dry density (ρmax) are investigated by test: (1) The ρmax has maximum value, ρmax and gradation area (S) approximately satisfy parabolic relationship. (2) The optimal gradation under different maximum particle size (dmax) remains unchanged. (3) The ρmax increases with the increases of dmax, and they satisfy linear relationship on ρmax-lgd coordinate. Secondly, the gradation of conventional earth-rockfill dam soil is divided into an internal, and the upper and lower envelope line is defined according to its boundary. Thirdly, the influence of different scale methods on gradation is investigated. Except that the similar gradation method retains the particle filling relationship of original gradation, the other scale methods increase the content of coarse particles. Based on the above understanding, the changes of ρmax under different scale methods are compared. It is found that only similar gradation method is applicable between the lower envelope line and optimal gradation. Different scale methods are applicable under different dmax between the upper envelope line and optimal gradation, and the corresponding scale method selection diagram are drawn. When analyzing the mechanical properties of coarse-grained soils in engineering, the scale selection method summarized in this paper can be directly used. Scale down according to the recommended scaling method, so that the results obtained in laboratory are close to the original gradation.
The maximum particle size of earth-rockfill dam soil in engineering is between 200~1 000 mm, whereas the maximum particle size for laboratory test is usually 60 mm. Therefore, the original gradation needs to be scaled to meet the requirement of laboratory test. Based on this, this research investigates the applicable conditions of different scale methods, so that the compactness of test material is closest to original gradation. Firstly, the three characteristics of maximum dry density (ρmax) are investigated by test: (1) The ρmax has maximum value, ρmax and gradation area (S) approximately satisfy parabolic relationship. (2) The optimal gradation under different maximum particle size (dmax) remains unchanged. (3) The ρmax increases with the increases of dmax, and they satisfy linear relationship on ρmax-lgd coordinate. Secondly, the gradation of conventional earth-rockfill dam soil is divided into an internal, and the upper and lower envelope line is defined according to its boundary. Thirdly, the influence of different scale methods on gradation is investigated. Except that the similar gradation method retains the particle filling relationship of original gradation, the other scale methods increase the content of coarse particles. Based on the above understanding, the changes of ρmax under different scale methods are compared. It is found that only similar gradation method is applicable between the lower envelope line and optimal gradation. Different scale methods are applicable under different dmax between the upper envelope line and optimal gradation, and the corresponding scale method selection diagram are drawn. When analyzing the mechanical properties of coarse-grained soils in engineering, the scale selection method summarized in this paper can be directly used. Scale down according to the recommended scaling method, so that the results obtained in laboratory are close to the original gradation.
, Available online ,
doi: 10.12170/20210722004
Abstract:
Due to the size limitation of the laboratory test equipment, the maximum particle size of the dam material had to be scaled down to the allowable size of the laboratory test equipment, and the particle size scaling led to changes in the test parameters. The results of the dry density, permeability coefficient, and triaxial shear tests for a barrier dam material with different maximum particle sizes show that the reduction in size leads to an increase in the content of fine particles less than 5 mm and affects the degree of compactness; as the maximum particle size decreases, the permeability coefficient of the specimen gradually decreases, and the direct use of the reduced size test results will overestimate the impermeability of the barrier dam material. Contraction rule has little effect on the strength index\begin{document}$ \varphi $\end{document} ![]()
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Due to the size limitation of the laboratory test equipment, the maximum particle size of the dam material had to be scaled down to the allowable size of the laboratory test equipment, and the particle size scaling led to changes in the test parameters. The results of the dry density, permeability coefficient, and triaxial shear tests for a barrier dam material with different maximum particle sizes show that the reduction in size leads to an increase in the content of fine particles less than 5 mm and affects the degree of compactness; as the maximum particle size decreases, the permeability coefficient of the specimen gradually decreases, and the direct use of the reduced size test results will overestimate the impermeability of the barrier dam material. Contraction rule has little effect on the strength index
, Available online ,
doi: 10.12170/20211230004
Abstract:
In view of the problems of high cost, high maintenance cost, difficult construction, long construction period, high self-weight and limited scope of coastal erosion protection, the use of inexpensive, easy construction, low self-weight, high corrosion resistance and low maintenance cost geogrid cage protect coastal erosion is proposed. The shape of the grating cage will influence the effect of coastal erosion stability. Based on the numerical analysis method of explicit dynamics, for the three shapes of grating cages with square section, circular section and wave-shaped section, the wave load is simulated by piston wave making and the hydrodynamic method of SPH smooth particles to simulate the water body. The contact between the water body and the geogrid cage and between the water body and the soil body is simulated by using the global property-assigned generic contact, and the tangential contact force between the geogrid cage and the coastal soil body is determined by using the penalty function. The force and displacement of geogrid cage and coastal soil body under wave load with and without geogrid cage and three shapes are analyzed with wave time history and peak value characteristics. The area with the greatest overall force of the geogrid cage is near the sea level. The use of the geogrid cage can reduce the influence of the wave on the bottom eddy current in the vertical cliff surface, and the wavy geogrid cage has a remarkable effect on the protection of coastal erosion.
In view of the problems of high cost, high maintenance cost, difficult construction, long construction period, high self-weight and limited scope of coastal erosion protection, the use of inexpensive, easy construction, low self-weight, high corrosion resistance and low maintenance cost geogrid cage protect coastal erosion is proposed. The shape of the grating cage will influence the effect of coastal erosion stability. Based on the numerical analysis method of explicit dynamics, for the three shapes of grating cages with square section, circular section and wave-shaped section, the wave load is simulated by piston wave making and the hydrodynamic method of SPH smooth particles to simulate the water body. The contact between the water body and the geogrid cage and between the water body and the soil body is simulated by using the global property-assigned generic contact, and the tangential contact force between the geogrid cage and the coastal soil body is determined by using the penalty function. The force and displacement of geogrid cage and coastal soil body under wave load with and without geogrid cage and three shapes are analyzed with wave time history and peak value characteristics. The area with the greatest overall force of the geogrid cage is near the sea level. The use of the geogrid cage can reduce the influence of the wave on the bottom eddy current in the vertical cliff surface, and the wavy geogrid cage has a remarkable effect on the protection of coastal erosion.
, Available online ,
doi: 10.12170/20220311001
Abstract:
A bulk cargo wharf yard foundation contains a weak layer of muddy clay layer, although two side foundations of yard were reinforced by cement mixing pile. However, a sliding failure as well as lateral translation collapse occurred where the thickest muddy clay is during the fill of ore heap on trial. In order to find the real reason for sliding failure and lateral translation collapse and to provide the design basis and reference for repair, a large centrifugal model was conducted. The filling process of the ore heap was simulated, and the vertical and horizontal displacement deformation of the surface of the ore heap and the yard foundation was measured. Firstly, the turning points of these displacement and deformation development was identified which is related to the critical point of stability and the ultimate bearing capacity of yard foundation are obtained. Secondly, based on the displacement field on the cross section of yard ground under the load of the ore heap, the failure mode and the development process of the sliding and translation failure of the bulk cargo wharf foundation were analyzed and discussed. The results showed that in the filling of the ore heap, its shallow subsoil subsidence and sliding failure first appeared due to its insufficient bearing capacity. Secondly, the subsidence of shallow subsoil occupied the space of underlying soft muddy clay layer, forcing it to lateral translate towards the side of the Nanliu River, resulting in a wider range of collapse.
A bulk cargo wharf yard foundation contains a weak layer of muddy clay layer, although two side foundations of yard were reinforced by cement mixing pile. However, a sliding failure as well as lateral translation collapse occurred where the thickest muddy clay is during the fill of ore heap on trial. In order to find the real reason for sliding failure and lateral translation collapse and to provide the design basis and reference for repair, a large centrifugal model was conducted. The filling process of the ore heap was simulated, and the vertical and horizontal displacement deformation of the surface of the ore heap and the yard foundation was measured. Firstly, the turning points of these displacement and deformation development was identified which is related to the critical point of stability and the ultimate bearing capacity of yard foundation are obtained. Secondly, based on the displacement field on the cross section of yard ground under the load of the ore heap, the failure mode and the development process of the sliding and translation failure of the bulk cargo wharf foundation were analyzed and discussed. The results showed that in the filling of the ore heap, its shallow subsoil subsidence and sliding failure first appeared due to its insufficient bearing capacity. Secondly, the subsidence of shallow subsoil occupied the space of underlying soft muddy clay layer, forcing it to lateral translate towards the side of the Nanliu River, resulting in a wider range of collapse.
, Available online ,
doi: 10.12170/20220624001
Abstract:
The distribution of meteorological stations in China is sparse and uneven, which can bring some difficulty for flood simulation of many small and medium-sized watersheds, where station-based precipitation information is usually insufficient. Merging satellite and ground-measured datasets is an effective method to obtain high spatiotemporal precipitation datasets, but the adaptability of the merged precipitation in flood simulation needs further studied. In this paper, Tunxi Basin is taken as an example to evaluate the capacity of these merged precipitation in flood simulation. Two important near-real-time satellite precipitation products in GPM era, IMERG_Early and GSMaP_NRT, are applied in this study. BP neural network model is adopted to merge them with ground measurements separately and then the two merged precipitation datasets are employed into Xin’anjiang model for flood simulation. Furthermore, in order to represent potential application of merged precipitation in the poor-gauged catchment, the number of meteorological stations in this area is reduced gradually to explore whether merged precipitation is still appliable when fusing only a little measured information. The results shows that the merged precipitation is reliable no matter how much the in-situ information is available. Specifically, the averaged DC was above 0.8 and the qualification rate of Qm and ΔH was larger than 70% and 90%, respectively. When there are limited meteorological stations within the watershed, the merged precipitation can provide more reliable simulation results compared with gauged observations. Moreover, the simulation results in Qianyang basin showed that merged precipitation based on 4 stations could present as reliable performance as 12 meteorological stations did in forecasting flood events. Therefore, merging satellite precipitation and station-based information can provide reliable precipitation dataset for flood forecasting, especially for small and medium-sized watersheds with limited in-situ information.
The distribution of meteorological stations in China is sparse and uneven, which can bring some difficulty for flood simulation of many small and medium-sized watersheds, where station-based precipitation information is usually insufficient. Merging satellite and ground-measured datasets is an effective method to obtain high spatiotemporal precipitation datasets, but the adaptability of the merged precipitation in flood simulation needs further studied. In this paper, Tunxi Basin is taken as an example to evaluate the capacity of these merged precipitation in flood simulation. Two important near-real-time satellite precipitation products in GPM era, IMERG_Early and GSMaP_NRT, are applied in this study. BP neural network model is adopted to merge them with ground measurements separately and then the two merged precipitation datasets are employed into Xin’anjiang model for flood simulation. Furthermore, in order to represent potential application of merged precipitation in the poor-gauged catchment, the number of meteorological stations in this area is reduced gradually to explore whether merged precipitation is still appliable when fusing only a little measured information. The results shows that the merged precipitation is reliable no matter how much the in-situ information is available. Specifically, the averaged DC was above 0.8 and the qualification rate of Qm and ΔH was larger than 70% and 90%, respectively. When there are limited meteorological stations within the watershed, the merged precipitation can provide more reliable simulation results compared with gauged observations. Moreover, the simulation results in Qianyang basin showed that merged precipitation based on 4 stations could present as reliable performance as 12 meteorological stations did in forecasting flood events. Therefore, merging satellite precipitation and station-based information can provide reliable precipitation dataset for flood forecasting, especially for small and medium-sized watersheds with limited in-situ information.
, Available online ,
doi: 10.12170/20220617004
Abstract:
Hydrological similarity theory is the core research topic of comparative hydrology and an important theoretical basis for obtaining hydrological model parameters in ungauged basins. Based on the analysis of the origin and development of the concept of hydrological similarity, two basic problems of discriminant condition and applicable condition in the theory of hydrological similarity are put forward. This paper reviews the progress of hydrological similarity theory from three aspects: classification framework, hydrological similarity index and hydrological similarity evaluation, and summarizes the application of hydrological similarity theory. Finally, based on the current progress and shortcomings, three key issues are pointed out: the definition of hydrological similarity, the discriminant basis and applicable conditions of hydrological similarity, and the influence of the hydrological similarity index and hydrological similarity degree on the selection of similar basin. This research can provide a theoretical basis for hydrological forecast of ungauged basins, exploration of hydrological physical law and improvement of hydrologic similarity theory.
Hydrological similarity theory is the core research topic of comparative hydrology and an important theoretical basis for obtaining hydrological model parameters in ungauged basins. Based on the analysis of the origin and development of the concept of hydrological similarity, two basic problems of discriminant condition and applicable condition in the theory of hydrological similarity are put forward. This paper reviews the progress of hydrological similarity theory from three aspects: classification framework, hydrological similarity index and hydrological similarity evaluation, and summarizes the application of hydrological similarity theory. Finally, based on the current progress and shortcomings, three key issues are pointed out: the definition of hydrological similarity, the discriminant basis and applicable conditions of hydrological similarity, and the influence of the hydrological similarity index and hydrological similarity degree on the selection of similar basin. This research can provide a theoretical basis for hydrological forecast of ungauged basins, exploration of hydrological physical law and improvement of hydrologic similarity theory.
, Available online ,
doi: 10.12170/20220326001
Abstract:
According to theTable 1 and Table 2 of Maximum Rainfall Data of Different Period over the history years and the "7·11" rainfall in 2021 in the Qinhe River basin, the rainfall frequency curve of three representative periods of fourteen long series stations are established by using P-Ⅲ distribution, and the rainfall return period of "7·11" with maximum 24 h greater than 100 mm, maximum 6 h greater than 100 mm and maximum 1 h greater than 50 mm are calculated. According to the historical survey flood and the maximum peak discharge over the years, the frequency curves are established, and the return period of peak discharge of Wulongkou, Shanluping and Wuzhi hydrology station are calculated. The results show that: (1) The return period of the largest 24 h rainfall 351 mm in Yaotou station is about 3,000 years, of the largest 6 h rainfall 328.5 mm in Yaotou station is about 10,000 years, of the largest 1 h rainfall rank the former three is 200~300 years. (2) The return periods of flood peak discharge of Wulongkou, Shanluping and Wuzhi station are equivalent to 30 years, 10~15 years and 10 years, respectively. The results can provide technical support for flood control operation in the Qinhe River Basin and the lower Yellow River.
According to the
, Available online ,
doi: 10.12170/20220208001
Abstract:
In order to weaken the nonlinearity and non-stationarity of the runoff time series and improve the accuracy of daily runoff forecasts in different forecast periods, a new VMD-PSO-LSTM multi-step forecasting combined model is proposed. First, the variational modal decomposition (VMD) method is used to decompose the original daily runoff sequence into a set of sub-sequences, and the long and short-term memory (LSTM) model parameters are optimized by the particle swarm optimization algorithm (PSO), and each sub-sequence is established In the PSO-LSTM model, the prediction results of each component are reconstructed to integrate the prediction results. The VMD-PSO-LSTM model is applied to the multi-step prediction of daily runoff at Huayuankou and Lijin Stations on the lower reaches of the Yellow River. Nash sutcliffe efficiency coefficient, correlation coefficient and root mean square error are used to evaluate the prediction results of the model. The results show that the ENS and R of the two stations are above 0.90 when the forecast period is 1 d, 2 d and 3 d. The comparison with the prediction results of CEEMD-PSO-LSTM and PSO-LSTM models shows that this model can effectively improve the accuracy of multi-step daily runoff prediction. It is an efficient and stable runoff prediction model, and provides a new method for multi-step daily runoff.
In order to weaken the nonlinearity and non-stationarity of the runoff time series and improve the accuracy of daily runoff forecasts in different forecast periods, a new VMD-PSO-LSTM multi-step forecasting combined model is proposed. First, the variational modal decomposition (VMD) method is used to decompose the original daily runoff sequence into a set of sub-sequences, and the long and short-term memory (LSTM) model parameters are optimized by the particle swarm optimization algorithm (PSO), and each sub-sequence is established In the PSO-LSTM model, the prediction results of each component are reconstructed to integrate the prediction results. The VMD-PSO-LSTM model is applied to the multi-step prediction of daily runoff at Huayuankou and Lijin Stations on the lower reaches of the Yellow River. Nash sutcliffe efficiency coefficient, correlation coefficient and root mean square error are used to evaluate the prediction results of the model. The results show that the ENS and R of the two stations are above 0.90 when the forecast period is 1 d, 2 d and 3 d. The comparison with the prediction results of CEEMD-PSO-LSTM and PSO-LSTM models shows that this model can effectively improve the accuracy of multi-step daily runoff prediction. It is an efficient and stable runoff prediction model, and provides a new method for multi-step daily runoff.
, Available online ,
doi: 10.12170/20221007001
Abstract:
Wind load is the main environmental loads of the floating array. For large-scale floating PV power stations, the wind-induced interference effect is significant. There are no mature methods to assess the wind load. Based on multi-scale analysis, a new numerical prediction method is proposed to forecast the wind load of a floating photovoltaic power station. The geometric model of the array is simplified through numerical simulations. The feasibility of using the simplified models to calculate wind load of the square array is verified. The load distribution rules of 30 (row)×28(column) array and 100 (row)×12(column) array at the maximum load wind direction are calculated using 145 million and 236 million grid cells, respectively. The changing rules of the environmental load of each component are analyzed with the rows and columns of the array. The prediction of the environmental load of the 195 (row)×98(column) array is given based on the analysis. The results show that the solar panels are the main wind components, which bears more than 80% of the wind load. The upstream components have interference effects on the downstream components and the wind load secondary peak is formed in the fifth row of windward. The internal loads of the array basically tend to be stable. The study solves the problem that the overall wind load of large-scale floating arrays cannot be directly calculated, and provides a reference for the wind resistance design of floating photovoltaic power stations.
Wind load is the main environmental loads of the floating array. For large-scale floating PV power stations, the wind-induced interference effect is significant. There are no mature methods to assess the wind load. Based on multi-scale analysis, a new numerical prediction method is proposed to forecast the wind load of a floating photovoltaic power station. The geometric model of the array is simplified through numerical simulations. The feasibility of using the simplified models to calculate wind load of the square array is verified. The load distribution rules of 30 (row)×28(column) array and 100 (row)×12(column) array at the maximum load wind direction are calculated using 145 million and 236 million grid cells, respectively. The changing rules of the environmental load of each component are analyzed with the rows and columns of the array. The prediction of the environmental load of the 195 (row)×98(column) array is given based on the analysis. The results show that the solar panels are the main wind components, which bears more than 80% of the wind load. The upstream components have interference effects on the downstream components and the wind load secondary peak is formed in the fifth row of windward. The internal loads of the array basically tend to be stable. The study solves the problem that the overall wind load of large-scale floating arrays cannot be directly calculated, and provides a reference for the wind resistance design of floating photovoltaic power stations.
, Available online ,
doi: 10.12170/20221014002
Abstract:
Coupling pressure is a key factor affecting the detection effect of ultrasonic excitation infrared thermography, and the coupling pressure loading device indirectly controls the excitation effect by influencing the coupling pressure in ultrasonic excitation. In this paper, the ultrasonic thermal excitation test of concrete microcracks under different loading methods of coupling pressure was carried out, and the temperature field of microcracks under the action of 900 N, 1200 N and 1500 N initial coupling pressure was analyzed through the comparative study of direct loading and aluminum alloy limiting device loading, and it was concluded that the temperature rise effect of directly loaded concrete was better than that of aluminum alloy limiting device under different loading methods of the same initial coupling pressure. This is due to the fact that the aluminum alloy loading device acts on the transducer by more than 50% of the additional force disturbance increment during the excitation process, and the equivalent resistance of the transducer changes drastically, resulting in the deterioration of the working stability of the ultrasonic excitation system, and then weakening the ultrasonic thermal excitation effect. Subsequently, the force disturbance of the loading device on the excitation transducer should be weakened, and the coupling pressure low disturbance loading device with the stiffness of the system adapted to the high-frequency excitation behavior of the transducer should be studied to achieve the efficient output of sound energy of the ultrasonic excitation system.
Coupling pressure is a key factor affecting the detection effect of ultrasonic excitation infrared thermography, and the coupling pressure loading device indirectly controls the excitation effect by influencing the coupling pressure in ultrasonic excitation. In this paper, the ultrasonic thermal excitation test of concrete microcracks under different loading methods of coupling pressure was carried out, and the temperature field of microcracks under the action of 900 N, 1200 N and 1500 N initial coupling pressure was analyzed through the comparative study of direct loading and aluminum alloy limiting device loading, and it was concluded that the temperature rise effect of directly loaded concrete was better than that of aluminum alloy limiting device under different loading methods of the same initial coupling pressure. This is due to the fact that the aluminum alloy loading device acts on the transducer by more than 50% of the additional force disturbance increment during the excitation process, and the equivalent resistance of the transducer changes drastically, resulting in the deterioration of the working stability of the ultrasonic excitation system, and then weakening the ultrasonic thermal excitation effect. Subsequently, the force disturbance of the loading device on the excitation transducer should be weakened, and the coupling pressure low disturbance loading device with the stiffness of the system adapted to the high-frequency excitation behavior of the transducer should be studied to achieve the efficient output of sound energy of the ultrasonic excitation system.
, Available online ,
doi: 10.12170/20220322003
Abstract:
Due to its special physical and mechanical characteristics, the destabilization failure process of sandy soil bank slope is significantly different from that of general clay soil bank slope. In this experiment, the deformation and failure process of thick sandy soil type river bank slope under different rainfall intensity and bank slope ratio was studied. A total of five sets of indoor physical model tests were designed, and each set of tests was conducted with buried moisture meter, micro pore pressure meter and lead thermometer for measurement, and the whole process of bank deformation and damage was recorded by high precision camera. The test results show that the cohesive force of unsaturated sandy soil tends to increase and then decrease with increasing water content, and has obvious peak value, and the angle of internal friction tends to decrease. The deformation and damage of sandy soil bank slope under different rainfall intensity and slope ratio show two different mechanisms. The short-duration rainfall will form a saturation zone on the surface layer of the slope, which prevents the infiltration of rainwater, and the water transport varies at different depths of the sandy soil layer, so the infiltration path of rainwater is not a single vertical infiltration. The bank erosion failure occurs under the coupling effect of rainfall scouring, rainfall infiltration and gravity erosion. This study can truly reflect the scour characteristics and collapse failure process of sandy slopes under complex conditions, and provide a reliable reference for establishing the theory and method of slope stability analysis under the joint action of multiple factors.
Due to its special physical and mechanical characteristics, the destabilization failure process of sandy soil bank slope is significantly different from that of general clay soil bank slope. In this experiment, the deformation and failure process of thick sandy soil type river bank slope under different rainfall intensity and bank slope ratio was studied. A total of five sets of indoor physical model tests were designed, and each set of tests was conducted with buried moisture meter, micro pore pressure meter and lead thermometer for measurement, and the whole process of bank deformation and damage was recorded by high precision camera. The test results show that the cohesive force of unsaturated sandy soil tends to increase and then decrease with increasing water content, and has obvious peak value, and the angle of internal friction tends to decrease. The deformation and damage of sandy soil bank slope under different rainfall intensity and slope ratio show two different mechanisms. The short-duration rainfall will form a saturation zone on the surface layer of the slope, which prevents the infiltration of rainwater, and the water transport varies at different depths of the sandy soil layer, so the infiltration path of rainwater is not a single vertical infiltration. The bank erosion failure occurs under the coupling effect of rainfall scouring, rainfall infiltration and gravity erosion. This study can truly reflect the scour characteristics and collapse failure process of sandy slopes under complex conditions, and provide a reliable reference for establishing the theory and method of slope stability analysis under the joint action of multiple factors.
, Available online ,
doi: 10.12170/20220505002
Abstract:
For the problem that the detection process of inner surface damage of tunnel based on acoustic reflection mechanism is susceptible to the interference of water environment noise, multipath noise and the noise of detection equipment, a denoising method of acoustic point cloud on the inner surface of water conveyance tunnel based on acoustic echo characteristics is proposed in this paper. The method utilizes the multi-echo data points formed by the inherent width characteristics of acoustic waves and the high-intensity values of data points formed by the superposition characteristics of acoustic waves, and combines the spatial position information of the point cloud to realize the noise filtering of the acoustic point cloud on the inner surface of the tunnel. Moreover, a series of experiments are constructed to verify the influence of different sensitive parameters on the denoising effect of the proposed method, and the results are compared with other classical point cloud filtering algorithms. The experimental results show that the proposed method is superior to the traditional laser point cloud filtering algorithm in the smoothing, denoising and reconstruction accuracy of the acoustic point cloud model on the inner surface of the tunnel. This method has practical research value for the detection of inner surface damage of water conveyance tunnel and the prevention of disasters in major water resources allocation projects.
For the problem that the detection process of inner surface damage of tunnel based on acoustic reflection mechanism is susceptible to the interference of water environment noise, multipath noise and the noise of detection equipment, a denoising method of acoustic point cloud on the inner surface of water conveyance tunnel based on acoustic echo characteristics is proposed in this paper. The method utilizes the multi-echo data points formed by the inherent width characteristics of acoustic waves and the high-intensity values of data points formed by the superposition characteristics of acoustic waves, and combines the spatial position information of the point cloud to realize the noise filtering of the acoustic point cloud on the inner surface of the tunnel. Moreover, a series of experiments are constructed to verify the influence of different sensitive parameters on the denoising effect of the proposed method, and the results are compared with other classical point cloud filtering algorithms. The experimental results show that the proposed method is superior to the traditional laser point cloud filtering algorithm in the smoothing, denoising and reconstruction accuracy of the acoustic point cloud model on the inner surface of the tunnel. This method has practical research value for the detection of inner surface damage of water conveyance tunnel and the prevention of disasters in major water resources allocation projects.
Statistical characteristics of spanwise vortex in open-channel turbulence with step-shaped spur dike
, Available online ,
doi: 10.12170/20220406004
Abstract:
The step-shaped spur dike is a common waterway regulation structure. Based on the PIV （Particle Image Velocimetry）open-channel experiment, the distribution laws of turbulence lateral vortex density, vortex area, vortex shape parameters, vortex rotation intensity along the longitudinal direction and the transverse direction in the step-shaped spur dike area are studied. The results show that the distribution of vortex density along the water depth direction appears fluctuating peaks near the top and the bottom of the spur dike, and the farther away from the spur dike along the flow direction, the smaller the fluctuation of vortex density. The area of the prograde vortex at the same location near the spur dike is generally larger than that of the retrograde vortex. The peak of the vortex area on the vertical distribution appears at the top of the spur dike and decreases with the distance from the central axis of open-channel. The spanwise vortex near the spur dike are mostly elliptical in shape, and the retrograde vortex at the bottom of the open-channel in the spur dike area and the prograde vortex at the water surface are both flat. The rotation intensity of the retrograde vortex at the same location near the spur dike is much larger than that of the prograde vortex. From the upstream of the spur dam to the spur dam area, the spanwise vortex rotation intensity shows a sharp decrease along the path. From the spur dam area to the downstream, the spanwise vortex rotation intensity gradually stabilizes along the path.
The step-shaped spur dike is a common waterway regulation structure. Based on the PIV （Particle Image Velocimetry）open-channel experiment, the distribution laws of turbulence lateral vortex density, vortex area, vortex shape parameters, vortex rotation intensity along the longitudinal direction and the transverse direction in the step-shaped spur dike area are studied. The results show that the distribution of vortex density along the water depth direction appears fluctuating peaks near the top and the bottom of the spur dike, and the farther away from the spur dike along the flow direction, the smaller the fluctuation of vortex density. The area of the prograde vortex at the same location near the spur dike is generally larger than that of the retrograde vortex. The peak of the vortex area on the vertical distribution appears at the top of the spur dike and decreases with the distance from the central axis of open-channel. The spanwise vortex near the spur dike are mostly elliptical in shape, and the retrograde vortex at the bottom of the open-channel in the spur dike area and the prograde vortex at the water surface are both flat. The rotation intensity of the retrograde vortex at the same location near the spur dike is much larger than that of the prograde vortex. From the upstream of the spur dam to the spur dam area, the spanwise vortex rotation intensity shows a sharp decrease along the path. From the spur dam area to the downstream, the spanwise vortex rotation intensity gradually stabilizes along the path.
, Available online ,
doi: 10.12170/20220216001
Abstract:
Some sections of mountain rivers have interlocking rapids and troughs, multiple beaches coexist, up and down linkage, and complex beaches, which have been the key problems of navigation development in southwest China. To address the problem of unclear ideas and principles for the management of serial rapids in mountain rivers, this paper analyzes the navigation-obstructing characteristics, water and sediment condition, and evolution of river bed of complex serial rapids based on the Xinkaihe serial rapids in the lower reaches of Minjiang River. In addition, this paper carries out calculation analysis and optimization research by combining physical model and two-dimensional flow and sediment mathematical model. The results of the study show that for the up-down problems of “sharp, curved, dangerous and shallow”, Regulation scheme should be targeted for each rapid. First, for the problems of “shallow” downstream, a combination of “dredging and remediation” should be used to enhance the hydro-sand dynamics of the shallow section. Secondly, for the problem of “curved and dangerous”, regulating structure should be used to adjust the flow path and improve the flow pattern. Finality, for the problem of “sharp” upstream, the focus should be placed on widening the channel and slowing down the flow speed. At the same time, on the basis of avoiding the remediation measures downstream from worsening the “rapid and dangerous” of the upstream rapid, it is also necessary to comprehensively coordinate the sand transport balance of the whole serial rapids. The research results of this paper can enrich the regulation technology of complex serial rapids in mountain rivers, and can also provide reference for other serial rapids management in China.
Some sections of mountain rivers have interlocking rapids and troughs, multiple beaches coexist, up and down linkage, and complex beaches, which have been the key problems of navigation development in southwest China. To address the problem of unclear ideas and principles for the management of serial rapids in mountain rivers, this paper analyzes the navigation-obstructing characteristics, water and sediment condition, and evolution of river bed of complex serial rapids based on the Xinkaihe serial rapids in the lower reaches of Minjiang River. In addition, this paper carries out calculation analysis and optimization research by combining physical model and two-dimensional flow and sediment mathematical model. The results of the study show that for the up-down problems of “sharp, curved, dangerous and shallow”, Regulation scheme should be targeted for each rapid. First, for the problems of “shallow” downstream, a combination of “dredging and remediation” should be used to enhance the hydro-sand dynamics of the shallow section. Secondly, for the problem of “curved and dangerous”, regulating structure should be used to adjust the flow path and improve the flow pattern. Finality, for the problem of “sharp” upstream, the focus should be placed on widening the channel and slowing down the flow speed. At the same time, on the basis of avoiding the remediation measures downstream from worsening the “rapid and dangerous” of the upstream rapid, it is also necessary to comprehensively coordinate the sand transport balance of the whole serial rapids. The research results of this paper can enrich the regulation technology of complex serial rapids in mountain rivers, and can also provide reference for other serial rapids management in China.
, Available online ,
doi: 10.12170/20220224002
Abstract:
Based on the latest CMIP6 global climate model, the climate and runoff changes in the Poyang Lake Basin in the middle of the 21st century (2050—2062) under various model scenarios were assessed. The SWAT model was constructed based on the hydrometeorological and underlying surface data in the Poyang Lake Basin from 2001 to 2019, and four climate models of CMIP6 were used to construct future climate scenarios using Delta downscaling method and simulate hydrological processes. The results show that compared with the reference period (2002—2014), the precipitation and temperature of the basin under various model scenarios have increasing trend, and the simulated evapotranspiration and runoff also increase, while the increase of runoff in the downstream areas of the basin is greater than that in other regions. The temperature increase under the SSP585 scenario is greater than that under the SSP126 scenario, and the runoff under the SSP585 scenario is less than that under the SSP126 scenario. Although the climate gets warmer still in the future, which lead to the increasing evapotranspiration in the basin, the variation of runoff (−11.93%—49.73%) is larger than that of evapotranspiration (1.06%—11.71%), which result in the more occurrence of extreme hydrologic events. The results of climate change and hydrological processes could guide water resources management and decision in Poyang Lake basin.
Based on the latest CMIP6 global climate model, the climate and runoff changes in the Poyang Lake Basin in the middle of the 21st century (2050—2062) under various model scenarios were assessed. The SWAT model was constructed based on the hydrometeorological and underlying surface data in the Poyang Lake Basin from 2001 to 2019, and four climate models of CMIP6 were used to construct future climate scenarios using Delta downscaling method and simulate hydrological processes. The results show that compared with the reference period (2002—2014), the precipitation and temperature of the basin under various model scenarios have increasing trend, and the simulated evapotranspiration and runoff also increase, while the increase of runoff in the downstream areas of the basin is greater than that in other regions. The temperature increase under the SSP585 scenario is greater than that under the SSP126 scenario, and the runoff under the SSP585 scenario is less than that under the SSP126 scenario. Although the climate gets warmer still in the future, which lead to the increasing evapotranspiration in the basin, the variation of runoff (−11.93%—49.73%) is larger than that of evapotranspiration (1.06%—11.71%), which result in the more occurrence of extreme hydrologic events. The results of climate change and hydrological processes could guide water resources management and decision in Poyang Lake basin.
, Available online ,
doi: 10.12170/20220310002
Abstract:
In order to study the size effect law of mechanical properties of hydraulic asphalt concrete under dynamic load, uniaxial dynamic compressive tests were carried out on hydraulic asphalt concrete samples with diameter of 100 mm and height diameter ratio of 0.5, 1.0, 1.5 and 2.0 respectively under the conditions of ambient temperature of 5 ℃ and strain rate of 10−5/s~10−2/s. The effects of strain rate effect and size effect on the dynamic compressive strength, elastic modulus and failure mode of asphalt concrete are analyzed. The results show that: (1) the greater the strain rate or the smaller the height diameter ratio of the sample, the more obvious the failure mode of the sample is; (2)with the increase of height diameter ratio, the compressive strength decreases and the elastic modulus increases; (3)with the increase of strain rate, the dynamic enhancement factors of compressive strength and elastic modulus increase nonlinearly. Finally, based on the experimental research, considering the synergistic effect of strain rate effect and size effect, and introducing the strain rate influence coefficient, the calculation model of dynamic compressive size effect of hydraulic asphalt concrete is established, and the rationality of the model is verified. The research results can be used as a reference for scientific research and engineering application of water supply asphalt concrete.
In order to study the size effect law of mechanical properties of hydraulic asphalt concrete under dynamic load, uniaxial dynamic compressive tests were carried out on hydraulic asphalt concrete samples with diameter of 100 mm and height diameter ratio of 0.5, 1.0, 1.5 and 2.0 respectively under the conditions of ambient temperature of 5 ℃ and strain rate of 10−5/s~10−2/s. The effects of strain rate effect and size effect on the dynamic compressive strength, elastic modulus and failure mode of asphalt concrete are analyzed. The results show that: (1) the greater the strain rate or the smaller the height diameter ratio of the sample, the more obvious the failure mode of the sample is; (2)with the increase of height diameter ratio, the compressive strength decreases and the elastic modulus increases; (3)with the increase of strain rate, the dynamic enhancement factors of compressive strength and elastic modulus increase nonlinearly. Finally, based on the experimental research, considering the synergistic effect of strain rate effect and size effect, and introducing the strain rate influence coefficient, the calculation model of dynamic compressive size effect of hydraulic asphalt concrete is established, and the rationality of the model is verified. The research results can be used as a reference for scientific research and engineering application of water supply asphalt concrete.
, Available online ,
doi: 10.12170/20220308002
Abstract:
Aiming at the problems of low efficiency of traditional manual reading of water level gauge, poor environmental adaptability and short range of water level gauge obtained by image processing based on water level gauge, a ruler free water level measurement technology based on image recognition is proposed. This technology only needs to calibrate the water level without the help of water level gauge, and input the collected water level image into U-net neural network for training, The image semantic segmentation models of water area and non water area are obtained, and the water level coordinates are obtained by image recognition. Finally, according to the mathematical model of water level calibration, the water level value is calculated by linear interpolation and coordinate fitting. The test results show that the technology has strong environmental adaptability, and the water level measurement errors in day and night are less than 1 cm, this technology can realize the real-time measurement of water level in a large range of rivers and reservoirs.
Aiming at the problems of low efficiency of traditional manual reading of water level gauge, poor environmental adaptability and short range of water level gauge obtained by image processing based on water level gauge, a ruler free water level measurement technology based on image recognition is proposed. This technology only needs to calibrate the water level without the help of water level gauge, and input the collected water level image into U-net neural network for training, The image semantic segmentation models of water area and non water area are obtained, and the water level coordinates are obtained by image recognition. Finally, according to the mathematical model of water level calibration, the water level value is calculated by linear interpolation and coordinate fitting. The test results show that the technology has strong environmental adaptability, and the water level measurement errors in day and night are less than 1 cm, this technology can realize the real-time measurement of water level in a large range of rivers and reservoirs.
, Available online ,
doi: 10.12170/20220221004
Abstract:
Risk compensation for joint operation of cascade reservoirs is an important measure to balance the risk level of each reservoir and ensure the objective and reasonable distribution of benefits. First of all, the relative risk model is introduced, and the conceptual model of "risk source-risk event-risk receptor-end point" is established to analyze the interaction of various factors in the joint operation of cascade reservoirs. The difference of reservoir construction scale and operation level will lead to the difference; Secondly, with the help of catastrophe theory and multi criteria evaluation method, the relative risk of each layer of the conceptual model is objectively deduced, and the risk level that each reservoir should bear is quantified. Finally, based on the coupled relative risk model and the risk compensation model of catastrophe multi criteria evaluation, the relative risk of the compensation benefit sharing scheme is reduced, and the risk compensation scheme for the joint operation of cascade reservoirs is determined. The proposed risk compensation method for joint operation of cascade reservoirs based on the risk compensation model is applied to the joint operation of Xiluodu, Xiangjiaba and the Three Gorges reservoir, and makes a comparative analysis based on the compensation benefit sharing scheme. The results show that: (1) the risk compensation method overcomes the subjectivity of coefficient quantification in the relative risk model and effectively reflects the mutual feed and equilibrium relationship between the benefits and risks of joint operation of cascade reservoirs. (2) The risk compensation scheme is consistent with the actual operation mode of the reservoir group. (3) The risk compensation method realizes multi-party cooperation and win-win, which is conducive to improving the enthusiasm of the reservoir to participate in the joint operation. By discussing the joint operation risk compensation scheme of Xiluodu, Xiangjiaba and Three Gorges reservoirs, it can provide reference for the joint operation risk analysis and benefit distribution of cascade reservoirs.
Risk compensation for joint operation of cascade reservoirs is an important measure to balance the risk level of each reservoir and ensure the objective and reasonable distribution of benefits. First of all, the relative risk model is introduced, and the conceptual model of "risk source-risk event-risk receptor-end point" is established to analyze the interaction of various factors in the joint operation of cascade reservoirs. The difference of reservoir construction scale and operation level will lead to the difference; Secondly, with the help of catastrophe theory and multi criteria evaluation method, the relative risk of each layer of the conceptual model is objectively deduced, and the risk level that each reservoir should bear is quantified. Finally, based on the coupled relative risk model and the risk compensation model of catastrophe multi criteria evaluation, the relative risk of the compensation benefit sharing scheme is reduced, and the risk compensation scheme for the joint operation of cascade reservoirs is determined. The proposed risk compensation method for joint operation of cascade reservoirs based on the risk compensation model is applied to the joint operation of Xiluodu, Xiangjiaba and the Three Gorges reservoir, and makes a comparative analysis based on the compensation benefit sharing scheme. The results show that: (1) the risk compensation method overcomes the subjectivity of coefficient quantification in the relative risk model and effectively reflects the mutual feed and equilibrium relationship between the benefits and risks of joint operation of cascade reservoirs. (2) The risk compensation scheme is consistent with the actual operation mode of the reservoir group. (3) The risk compensation method realizes multi-party cooperation and win-win, which is conducive to improving the enthusiasm of the reservoir to participate in the joint operation. By discussing the joint operation risk compensation scheme of Xiluodu, Xiangjiaba and Three Gorges reservoirs, it can provide reference for the joint operation risk analysis and benefit distribution of cascade reservoirs.
, Available online ,
doi: 10.12170/20220112001
Abstract:
To study the mechanism of different fissure parameters on rock deformation and failure and law of energy evolution, the X-ray diffraction and uniaxial compression tests were conducted on Jinping marble. Firstly, three-dimensional GBM was generated based on the X-ray diffraction results and particle flow code. Then, the mesoscopic parameters was calibrated according to the results of uniaxial compression tests of intact marble sample, and the numerical model containing various fissure parameters was constructed. Finally, the process of the deformation and failure along with the energy evolution of numerical samples was simulated and analyzed. The results show that the strength of sample increases first and then decreases with the increasing fissure dip angle. The strength of sample is intensified with the increase of the axial offset and fissure length. With an increase in the radial offset of fissure, the strength of sample decreases first and then increases. In addition, the influence degree of dip and spatial position of fissure on the strength of sample is related to the fissure length. When the fracture length is large, the dip angle inhibits the deterioration of axial offset and even changes the influence mode of radial offset. The hardening effect of dip angle on the sample strength is more obvious as fissure length is larger. It is also found that the length, dip and spatial position of fissure significantly change the failure mode of sample.
To study the mechanism of different fissure parameters on rock deformation and failure and law of energy evolution, the X-ray diffraction and uniaxial compression tests were conducted on Jinping marble. Firstly, three-dimensional GBM was generated based on the X-ray diffraction results and particle flow code. Then, the mesoscopic parameters was calibrated according to the results of uniaxial compression tests of intact marble sample, and the numerical model containing various fissure parameters was constructed. Finally, the process of the deformation and failure along with the energy evolution of numerical samples was simulated and analyzed. The results show that the strength of sample increases first and then decreases with the increasing fissure dip angle. The strength of sample is intensified with the increase of the axial offset and fissure length. With an increase in the radial offset of fissure, the strength of sample decreases first and then increases. In addition, the influence degree of dip and spatial position of fissure on the strength of sample is related to the fissure length. When the fracture length is large, the dip angle inhibits the deterioration of axial offset and even changes the influence mode of radial offset. The hardening effect of dip angle on the sample strength is more obvious as fissure length is larger. It is also found that the length, dip and spatial position of fissure significantly change the failure mode of sample.
, Available online ,
doi: 10.12170/20211220004
Abstract:
To solve the problem of water level prediction at ungauged sections, the coupled BP neural network and MIKE11 model was proposed in this study. First, the water level, precipitation and antecedent influencing factors were collected for correlation analysis according to the hourly flood events data. Second, the input factors with the highest correlation degree of water level in Lanjiang River Basin in the prediction period of 12 h and 24 h were selected, the water level predictions at Lanxi station were built by MLR and BPNN models for different forecasting lead times. Then, the BPNN-based water level prediction at ungauged sections in Lanjiang basin was constructed through the synthetic water level data generated by MIKE NAM-HD model. The results indicated that (1) The performance of BPNN is better than MLR model for water level predictions of long lead times. (2) The NSE obtained from BPNN gradually decreases as the increasing of forecasting lead time. (3) After input variable selection, the improvements of BPNN at lead times of 12 h and 24 h are about 9.0% and 34.7% in terms of NSE. (4) The proposed BPNN coupled with MIKE11 model is able to apply to ungauged section water level predictions.
To solve the problem of water level prediction at ungauged sections, the coupled BP neural network and MIKE11 model was proposed in this study. First, the water level, precipitation and antecedent influencing factors were collected for correlation analysis according to the hourly flood events data. Second, the input factors with the highest correlation degree of water level in Lanjiang River Basin in the prediction period of 12 h and 24 h were selected, the water level predictions at Lanxi station were built by MLR and BPNN models for different forecasting lead times. Then, the BPNN-based water level prediction at ungauged sections in Lanjiang basin was constructed through the synthetic water level data generated by MIKE NAM-HD model. The results indicated that (1) The performance of BPNN is better than MLR model for water level predictions of long lead times. (2) The NSE obtained from BPNN gradually decreases as the increasing of forecasting lead time. (3) After input variable selection, the improvements of BPNN at lead times of 12 h and 24 h are about 9.0% and 34.7% in terms of NSE. (4) The proposed BPNN coupled with MIKE11 model is able to apply to ungauged section water level predictions.
, Available online ,
doi: 10.12170/20220421001
Abstract:
For comprehensive understanding about the formation causes and mechanical mechanisms of various types of pit-collapses in the lower reaches of the Yangtze River, taking the pit-collapse occurred in the Hechangzhou head as an example, deep analysis was done, and then the soil mass instability model and displacement estimation method are proposed by the results of soil mechanics. The results show that the pit-collapse occurred in the Hechangzhou head belongs to lateral slide type. Its formation cause is that there is the silt layer easy to liquefy in the beach soil. When there is a certain external vibration disturbance factor, once the liquefaction condition is mature, the silt layer becomes a sliding layer, the liquefaction layer and the overlying soil layer would occur several times of large lateral slide. The slide soil mass would skid out of the collapse pond mouth into the deep channel groove, and then was quickly dispersed and transported to the downstream by the main rive current. The empirical formula of power function between the distance of sliding soil mass and the thickness of liquefied layer and dip angle of sliding layer can be obtained by using mathematical statistics method. According to these results, it can provide a reference for the early warning and managing of such collapse in the lower reaches of the Yangtze River.
For comprehensive understanding about the formation causes and mechanical mechanisms of various types of pit-collapses in the lower reaches of the Yangtze River, taking the pit-collapse occurred in the Hechangzhou head as an example, deep analysis was done, and then the soil mass instability model and displacement estimation method are proposed by the results of soil mechanics. The results show that the pit-collapse occurred in the Hechangzhou head belongs to lateral slide type. Its formation cause is that there is the silt layer easy to liquefy in the beach soil. When there is a certain external vibration disturbance factor, once the liquefaction condition is mature, the silt layer becomes a sliding layer, the liquefaction layer and the overlying soil layer would occur several times of large lateral slide. The slide soil mass would skid out of the collapse pond mouth into the deep channel groove, and then was quickly dispersed and transported to the downstream by the main rive current. The empirical formula of power function between the distance of sliding soil mass and the thickness of liquefied layer and dip angle of sliding layer can be obtained by using mathematical statistics method. According to these results, it can provide a reference for the early warning and managing of such collapse in the lower reaches of the Yangtze River.
, Available online ,
doi: 10.12170/20220719003
Abstract:
Revealing the main influencing factors of coupled water resources-economic society-ecological environment coordination is important for strengthening the macro management of natural resources and economic society systems as well as promoting regional sustainable development. With the selection of indicators based on two dimensions of endogenous and outward dynamics, this study introduces a fixed-effects model to measure the coupled water resources-economic society-ecological environment coordination drivers in Gansu Province from 2010 to 2019 by analyzing the evolution of regional water resources-economic society-ecological environment coupling. The results show that: ① The level of economic development and technological development have a positive effect on the improvement of the level of coupled water resources-economic society-ecological environment coordination in Gansu Province, with regression coefficients of 0.029 and 0.021 respectively, and passing the 1% significance test. ② The factors influencing the zoning areas differ significantly, the improvement of the level of environmental protection and economic development has a catalytic effect on the improvement of the coupling coordination of the sub-regions. In the context of accelerating economic society development in Gansu Province, policies and incentives of relevant drivers should be coordinated to promote the coupled evolution of water resources-economic society-ecological environment system.
Revealing the main influencing factors of coupled water resources-economic society-ecological environment coordination is important for strengthening the macro management of natural resources and economic society systems as well as promoting regional sustainable development. With the selection of indicators based on two dimensions of endogenous and outward dynamics, this study introduces a fixed-effects model to measure the coupled water resources-economic society-ecological environment coordination drivers in Gansu Province from 2010 to 2019 by analyzing the evolution of regional water resources-economic society-ecological environment coupling. The results show that: ① The level of economic development and technological development have a positive effect on the improvement of the level of coupled water resources-economic society-ecological environment coordination in Gansu Province, with regression coefficients of 0.029 and 0.021 respectively, and passing the 1% significance test. ② The factors influencing the zoning areas differ significantly, the improvement of the level of environmental protection and economic development has a catalytic effect on the improvement of the coupling coordination of the sub-regions. In the context of accelerating economic society development in Gansu Province, policies and incentives of relevant drivers should be coordinated to promote the coupled evolution of water resources-economic society-ecological environment system.
, Available online ,
doi: 10.12170/20220527001
Abstract:
The level of economic and social development, water resource endowment, water use efficiency and water saving of 13 cities in Jiangsu Province are quite different, the mode and promotion path of water saving differs from each other. Based on the existing indicators, this study constructed a water saving zoning index system with Jiangsu characteristics from six aspects: water supply, water saving, water use, drainage, water resources and socio-economic conditions. Then, the “principal component analysis + systematic clustering” method was introduced and divided into three water-saving zones: zone Ⅰ includes Nanjing, Changzhou, Wuxi and Suzhou; Zone Ⅱ includes Huai’an, Yancheng, Yangzhou, Taizhou, Nantong and Zhenjiang; Zone Ⅲ includes Xuzhou, Lianyungang and Suqian. Finally, based on the analysis of current water saving status in each zone, the key emphasis in water saving work was proposed. The water-saving divisions of Jiangsu Province in this study can provide important support for exploring water-saving priority approaches in regions with abundant water.
The level of economic and social development, water resource endowment, water use efficiency and water saving of 13 cities in Jiangsu Province are quite different, the mode and promotion path of water saving differs from each other. Based on the existing indicators, this study constructed a water saving zoning index system with Jiangsu characteristics from six aspects: water supply, water saving, water use, drainage, water resources and socio-economic conditions. Then, the “principal component analysis + systematic clustering” method was introduced and divided into three water-saving zones: zone Ⅰ includes Nanjing, Changzhou, Wuxi and Suzhou; Zone Ⅱ includes Huai’an, Yancheng, Yangzhou, Taizhou, Nantong and Zhenjiang; Zone Ⅲ includes Xuzhou, Lianyungang and Suqian. Finally, based on the analysis of current water saving status in each zone, the key emphasis in water saving work was proposed. The water-saving divisions of Jiangsu Province in this study can provide important support for exploring water-saving priority approaches in regions with abundant water.
, Available online ,
doi: 10.12170/20220925001
Abstract:
Dam seismic safety is a key technical problem related to national water resources safety and even social public safety. Seismic safety evaluation and dynamic interaction analysis of dams is an important research work in practical engineering. In this paper, the overall analysis model of gravity dams considering dam-foundation-reservoir interaction is established, the reservoir is simulated by acoustic elements, and the feasibility of this simulation method is verified by several examples. Then, the crack propagation process of the dam is simulated by the extended finite element method, and the contact model considering the opening and closing of the crack surface is established. Taking Jin'anqiao RCC gravity dam as an example, the gravity dam-foundation-reservoir-dynamic interaction model is established. The effects of the additional mass method, the fluid-structure coupling model without considering the compressibility of the reservoir and the compressibility of the reservoir water on the seismic cracking process of the gravity dam are discussed. The overload potential of the gravity dam with cracks and the influence of the initial crack position on the crack propagation are analyzed. The results show that the additional mass method and fluid-structure coupling model without considering the compressibility of reservoir water exaggerate the earthquake action. and a longer crack propagation and larger crack can be observed. With the increasing of the seismic peak acceleration, the initial position of the downward deflection of the crack propagation path of the gravity dam continues to extend to the interior of the dam, and the dam will produce long cracks under the seismic load with the seismic load of 1.3 times of the design seismic acceleration. The initial crack at the slope break point propagates more obviously under seismic load.
Dam seismic safety is a key technical problem related to national water resources safety and even social public safety. Seismic safety evaluation and dynamic interaction analysis of dams is an important research work in practical engineering. In this paper, the overall analysis model of gravity dams considering dam-foundation-reservoir interaction is established, the reservoir is simulated by acoustic elements, and the feasibility of this simulation method is verified by several examples. Then, the crack propagation process of the dam is simulated by the extended finite element method, and the contact model considering the opening and closing of the crack surface is established. Taking Jin'anqiao RCC gravity dam as an example, the gravity dam-foundation-reservoir-dynamic interaction model is established. The effects of the additional mass method, the fluid-structure coupling model without considering the compressibility of the reservoir and the compressibility of the reservoir water on the seismic cracking process of the gravity dam are discussed. The overload potential of the gravity dam with cracks and the influence of the initial crack position on the crack propagation are analyzed. The results show that the additional mass method and fluid-structure coupling model without considering the compressibility of reservoir water exaggerate the earthquake action. and a longer crack propagation and larger crack can be observed. With the increasing of the seismic peak acceleration, the initial position of the downward deflection of the crack propagation path of the gravity dam continues to extend to the interior of the dam, and the dam will produce long cracks under the seismic load with the seismic load of 1.3 times of the design seismic acceleration. The initial crack at the slope break point propagates more obviously under seismic load.
, Available online ,
doi: 10.12170/20220224001
Abstract:
In order to enrich the development and utilization theory of landslide dam, explore the densification method and design parameters suitable for landslide material, and study the densification effect and mechanism of rolling dynamic compaction on landslide material. Based on the similarity law, the laboratory model test of rolling dynamic compaction on natural landslide material with different impact roller weight and traction speed was designed. The macroscopic and meso-method was comprehensively used to test the development and propagation law of dynamic stress, deformation characteristics, particle movement and reinforcement effect after rolling dynamic compaction. The test results showed that the impact load caused by the roller was a triangular pulse load, the contact stress increased with the increasing traction speed and impact roller weight, and the dynamic soil stress of foundation increased with the increasing roller passes. Rolling dynamic compaction had a good reinforcement effect on the surface layer of landslide dam material foundation. The dynamic soil stress and displacement inside the foundation decreased rapidly with the depth, and the strength within the depth of 3.6 m increased significantly. The increasing speed of the impact roller had a greater improvement on the reinforcement effect, which can effectively improve the impact dynamic stress, and then transfer the reinforcement effect of roller to the deep layer. The rolling dynamic compaction parameters that were suitable for the Yigong landslide dam material are: the impact roller weight of 13.5 t, the traction speed of 3.46 m/s, and the number of passes of 12.
In order to enrich the development and utilization theory of landslide dam, explore the densification method and design parameters suitable for landslide material, and study the densification effect and mechanism of rolling dynamic compaction on landslide material. Based on the similarity law, the laboratory model test of rolling dynamic compaction on natural landslide material with different impact roller weight and traction speed was designed. The macroscopic and meso-method was comprehensively used to test the development and propagation law of dynamic stress, deformation characteristics, particle movement and reinforcement effect after rolling dynamic compaction. The test results showed that the impact load caused by the roller was a triangular pulse load, the contact stress increased with the increasing traction speed and impact roller weight, and the dynamic soil stress of foundation increased with the increasing roller passes. Rolling dynamic compaction had a good reinforcement effect on the surface layer of landslide dam material foundation. The dynamic soil stress and displacement inside the foundation decreased rapidly with the depth, and the strength within the depth of 3.6 m increased significantly. The increasing speed of the impact roller had a greater improvement on the reinforcement effect, which can effectively improve the impact dynamic stress, and then transfer the reinforcement effect of roller to the deep layer. The rolling dynamic compaction parameters that were suitable for the Yigong landslide dam material are: the impact roller weight of 13.5 t, the traction speed of 3.46 m/s, and the number of passes of 12.
, Available online ,
doi: 10.12170/20220613004
Abstract:
The sand gravel has more fine particles and is easy to be compacted. Especially under the action of heavy roller, the pore structure and permeability characteristics of the sand gravel may change after compaction, which will affect the seepage safety of the high concrete face gravel dam. In this research, the permeability test of sand gravel after compaction was carried out to analyze the relationship between the characteristic particle size and the equivalent pore diameter of sand gravel, as well as the influence of different porosity on the permeability of sand gravel, and verify the commonly used empirical calculation formula of permeability coefficient. The research shows that, the reduction of the porosity of the sand gravel has a great impact on its permeability characteristics. Due to the large content of fine particles in the sand gravel, and the particles are tightly packed after compaction, the permeability coefficient of the sand gravel obtained from the permeability test is 1~2 orders of magnitude smaller than the calculated value of the conventional empirical formula, resulting in a large deviation. As the porosity decreases to a certain extent, the sand gravel shows certain viscous characteristics, the internal void increases, and the permeability coefficient decreases significantly. Based on the formula of China Institute of Water Resources and Hydropower Research, the effective pore reduction coefficient is introduced to modify the formula, and the results calculated from the modified formula are more accurate. This study can provide a basis for the drainage design of high concrete face gravel dam.
The sand gravel has more fine particles and is easy to be compacted. Especially under the action of heavy roller, the pore structure and permeability characteristics of the sand gravel may change after compaction, which will affect the seepage safety of the high concrete face gravel dam. In this research, the permeability test of sand gravel after compaction was carried out to analyze the relationship between the characteristic particle size and the equivalent pore diameter of sand gravel, as well as the influence of different porosity on the permeability of sand gravel, and verify the commonly used empirical calculation formula of permeability coefficient. The research shows that, the reduction of the porosity of the sand gravel has a great impact on its permeability characteristics. Due to the large content of fine particles in the sand gravel, and the particles are tightly packed after compaction, the permeability coefficient of the sand gravel obtained from the permeability test is 1~2 orders of magnitude smaller than the calculated value of the conventional empirical formula, resulting in a large deviation. As the porosity decreases to a certain extent, the sand gravel shows certain viscous characteristics, the internal void increases, and the permeability coefficient decreases significantly. Based on the formula of China Institute of Water Resources and Hydropower Research, the effective pore reduction coefficient is introduced to modify the formula, and the results calculated from the modified formula are more accurate. This study can provide a basis for the drainage design of high concrete face gravel dam.
, Available online ,
doi: 10.12170/20220120001
Abstract:
Digital twin is a necessary technology for the smart upgrading and transformation of the water conservancy industry, that is also the key to build a digital twin basin of seven rivers. This paper summarized various digital twin water-related technologies which were stratified according to different purposes of technical means, and described the corresponding relationship between perception layer, facility layer, data processing layer, model layer, platform service layer, application layer and smart water conservancy. In order to build a smart water conservancy framework system with the functions of "multi data integration and visualization, operation situation awareness, comprehensive analysis and judgment, emergency linkage disposal", a smart water conservancy dynamic modeling process was proposed by referring to the workshop dynamic modeling theory, which based on real-time data perception, dynamic modeling and dynamic iteration of inverse model. Taking the digital twin project of a sluice in the river basin as an example, the six levels of smart water conservancy system were combined with the cutting-edge technology of digital twin. A model platform of related facilities was built to realize the purpose of monitoring sluice related data, quickly perceiving sluice security boundary and timely analyzing sluice operation situation. The relevant work is expected to provide reference for promoting the construction of smart water conservancy and building digital twin river basin.
Digital twin is a necessary technology for the smart upgrading and transformation of the water conservancy industry, that is also the key to build a digital twin basin of seven rivers. This paper summarized various digital twin water-related technologies which were stratified according to different purposes of technical means, and described the corresponding relationship between perception layer, facility layer, data processing layer, model layer, platform service layer, application layer and smart water conservancy. In order to build a smart water conservancy framework system with the functions of "multi data integration and visualization, operation situation awareness, comprehensive analysis and judgment, emergency linkage disposal", a smart water conservancy dynamic modeling process was proposed by referring to the workshop dynamic modeling theory, which based on real-time data perception, dynamic modeling and dynamic iteration of inverse model. Taking the digital twin project of a sluice in the river basin as an example, the six levels of smart water conservancy system were combined with the cutting-edge technology of digital twin. A model platform of related facilities was built to realize the purpose of monitoring sluice related data, quickly perceiving sluice security boundary and timely analyzing sluice operation situation. The relevant work is expected to provide reference for promoting the construction of smart water conservancy and building digital twin river basin.
, Available online ,
doi: 10.12170/20220531001
Abstract:
The monitoring system of pump station buildings becomes increasingly perfect, with a large number of monitoring points. Currently, the monitoring sequence of single point was mainly used in the safety monitoring of pump station building, which cannot reflect the overall state. In view of that, the vertical displacement of pump station was taken as the research object, and a similarity index and corresponding measurement method were put forward to analyze the similarity of monitoring sequences of deformation for pump station quantitatively based on panel data theory and dynamic time warping algorithm; By introducing the spatial incidence matrix, the zoning method of pump station considering the position of measuring points was proposed. Finally, the cluster analysis model of deformation of pump station based on panel data analysis method was established. Then the validity of the proposed model was verified through a case study of a pump station project of South-to-North Water Diversion Project. The results show the measuring points can be divided into four zones by using the model proposed, and the characteristics of deformation and load are clarified effectively, which provide a novel method for the safety monitoring of the pump station buildings.
The monitoring system of pump station buildings becomes increasingly perfect, with a large number of monitoring points. Currently, the monitoring sequence of single point was mainly used in the safety monitoring of pump station building, which cannot reflect the overall state. In view of that, the vertical displacement of pump station was taken as the research object, and a similarity index and corresponding measurement method were put forward to analyze the similarity of monitoring sequences of deformation for pump station quantitatively based on panel data theory and dynamic time warping algorithm; By introducing the spatial incidence matrix, the zoning method of pump station considering the position of measuring points was proposed. Finally, the cluster analysis model of deformation of pump station based on panel data analysis method was established. Then the validity of the proposed model was verified through a case study of a pump station project of South-to-North Water Diversion Project. The results show the measuring points can be divided into four zones by using the model proposed, and the characteristics of deformation and load are clarified effectively, which provide a novel method for the safety monitoring of the pump station buildings.
, Available online ,
doi: 10.12170/20220720002
Abstract:
The wetting of rockfill material can easily lead to the uncoordinated deformation between it and the core wall, thus causing longitudinal cracks at the top of the dam and endangering the safety of the dam. Through the large-scale triaxial compression test and triaxial wetting test of rockfill materials of a hydropower station, the relationship between dilatancy ratio and stress ratio during loading and wetting process, and the relationship between wetting strain and confining pressure and stress level were studied respectively. The results show that the peak strength of the wetting specimen is basically the same as that of the initial saturated specimen, that is, the stress level of the specimen during wetting has little effect on its peak strength, but the final volume change of the specimen is obviously affected by the stress level during wetting. Therefore, the calculation of the wetting deformation of the earth-rock dam should be based on the single-line test. The consolidation of confining pressure and stress level during the triaxial wetting test has a significant effect on the wetting strain value. The higher the confining pressure, the larger the wetting volume strain, the higher the wetting stress level, and the larger the axial wetting strain. Based on this, a wetting strain calculation model considering the influence of confining pressure and stress level is proposed. In the process of loading and wetting, rockfill materials obey different stress dilatancy equations. When constructing the elastoplastic model of wetting deformation, different plastic potential functions should be used to describe the loading strain direction and wetting strain direction of rockfill materials respectively. The research results have certain guiding significance and engineering application value for the simulation of wetting deformation and crack prediction of earth-rock dam.
The wetting of rockfill material can easily lead to the uncoordinated deformation between it and the core wall, thus causing longitudinal cracks at the top of the dam and endangering the safety of the dam. Through the large-scale triaxial compression test and triaxial wetting test of rockfill materials of a hydropower station, the relationship between dilatancy ratio and stress ratio during loading and wetting process, and the relationship between wetting strain and confining pressure and stress level were studied respectively. The results show that the peak strength of the wetting specimen is basically the same as that of the initial saturated specimen, that is, the stress level of the specimen during wetting has little effect on its peak strength, but the final volume change of the specimen is obviously affected by the stress level during wetting. Therefore, the calculation of the wetting deformation of the earth-rock dam should be based on the single-line test. The consolidation of confining pressure and stress level during the triaxial wetting test has a significant effect on the wetting strain value. The higher the confining pressure, the larger the wetting volume strain, the higher the wetting stress level, and the larger the axial wetting strain. Based on this, a wetting strain calculation model considering the influence of confining pressure and stress level is proposed. In the process of loading and wetting, rockfill materials obey different stress dilatancy equations. When constructing the elastoplastic model of wetting deformation, different plastic potential functions should be used to describe the loading strain direction and wetting strain direction of rockfill materials respectively. The research results have certain guiding significance and engineering application value for the simulation of wetting deformation and crack prediction of earth-rock dam.
, Available online ,
doi: 10.12170/20220330003
Abstract:
This paper summarizes the influencing factors of scour and abrasion damage and the types of abrasion resistance materials of hydropower engineering structures, and focuses on the test methods and the influencing factors of abrasion resistance property, the types and the application of abrasion resistance coatings, and states the performance difference and cost performance of the epoxy resin wear-resistant coatings and polyurea wear-resistant coating and wear-resistant concrete. The results show that: the main influencing factors of abrasion damage of hydraulic structures are the abrasion angle of water, the current speed of water, the particle size and the content of suspended materials; the epoxy resin coatings and polyurea coatings are applied on hydraulic structures mainly; the influencing factors of wear resistance property of the abrasion coatings are the elasticity and hardness of the resin, the type of filler, the hardness and content of micron filler, etc; abrasion resistant coatings are mainly used on sand discharge tunnels, flood discharge tunnels and overflow surfaces of hydropower projects.
This paper summarizes the influencing factors of scour and abrasion damage and the types of abrasion resistance materials of hydropower engineering structures, and focuses on the test methods and the influencing factors of abrasion resistance property, the types and the application of abrasion resistance coatings, and states the performance difference and cost performance of the epoxy resin wear-resistant coatings and polyurea wear-resistant coating and wear-resistant concrete. The results show that: the main influencing factors of abrasion damage of hydraulic structures are the abrasion angle of water, the current speed of water, the particle size and the content of suspended materials; the epoxy resin coatings and polyurea coatings are applied on hydraulic structures mainly; the influencing factors of wear resistance property of the abrasion coatings are the elasticity and hardness of the resin, the type of filler, the hardness and content of micron filler, etc; abrasion resistant coatings are mainly used on sand discharge tunnels, flood discharge tunnels and overflow surfaces of hydropower projects.
, Available online ,
doi: 10.12170/20220225001
Abstract:
The stiff clay widely distributed on the bank slope of the project of "Diversion of water from Changjiang River to Huaihe River" is bound to cause a series of engineering problems under the continuous soaking of river water, which will have a great impact on the stability of the bank slope. In order to explore the stiff clay under continuous soaking strength degradation mechanism, taking the stiff clay of the bank slope of Hefei section of the "River Diversion and Huaihe River" as the research object, design for continuous soaking test, triaxial compression test, the mineral composition analysis test, microstructure test and ion concentration of soaking solution test, on the strength of stiff clay under continuous soaking degradation mechanism were studied. The results show that the strength of stiff clay will deteriorate under continuous soaking, and the deterioration is obvious within 30 days, and the deterioration is weak and tends to be gentle after 30 days. The mass fraction of calcite in stiff clay decreased exponentially with the increase of continuous soaking time, and the Ca2+ concentration in soaking solution increased logarithmically. With the increase of continuous soaking time, the number and size of micropores on the sample surface increased, and the increase rate was fast within 30 days. After 30 days, the increase rate slowed down and gradually stabilized. The strength deterioration of stiff clay after continuous soaking is caused by water absorption and expansion of hydrophilic clay minerals and dissolution of calcite, which acts as the "skeleton" in the soil.
The stiff clay widely distributed on the bank slope of the project of "Diversion of water from Changjiang River to Huaihe River" is bound to cause a series of engineering problems under the continuous soaking of river water, which will have a great impact on the stability of the bank slope. In order to explore the stiff clay under continuous soaking strength degradation mechanism, taking the stiff clay of the bank slope of Hefei section of the "River Diversion and Huaihe River" as the research object, design for continuous soaking test, triaxial compression test, the mineral composition analysis test, microstructure test and ion concentration of soaking solution test, on the strength of stiff clay under continuous soaking degradation mechanism were studied. The results show that the strength of stiff clay will deteriorate under continuous soaking, and the deterioration is obvious within 30 days, and the deterioration is weak and tends to be gentle after 30 days. The mass fraction of calcite in stiff clay decreased exponentially with the increase of continuous soaking time, and the Ca2+ concentration in soaking solution increased logarithmically. With the increase of continuous soaking time, the number and size of micropores on the sample surface increased, and the increase rate was fast within 30 days. After 30 days, the increase rate slowed down and gradually stabilized. The strength deterioration of stiff clay after continuous soaking is caused by water absorption and expansion of hydrophilic clay minerals and dissolution of calcite, which acts as the "skeleton" in the soil.
, Available online ,
doi: 10.12170/20220307001
Abstract:
Compared with inland areas, the urban tidal river network faces greater pressure in terms of flood and waterlog control and water environment protection. The use of tidal range for inland river diversion and drainage by the sluices along outer river is an effective way to enhance the flood control and drainage capacity of tidal river network and improve its water environment quality. However, the development of riverside industries along outer river is in contradiction with the water diversion and drainage of tidal river network. For arguing the new construction of Huisheng Heavy Industry 3# Outfitting Wharf near the gate of Nantong Farm Sluice, in this paper, mathematical models were used to investigate the influence of the outfitting wharf project on the diversion and drainage of tidal river network, and a generalization of ship into movable gate was proposed. The equivalent treatment method for the analysis of the water blocking effect of the ship and its rationality have been verified; it is concluded that the widening of the dredging measures at the entrance of the outfitting wharf project are beneficial to the drainage of the tidal river network, but are not good for the water diversion of the tidal river network; ship mooring at the entrance has little effect on the diversion and drainage of the tidal river network.
Compared with inland areas, the urban tidal river network faces greater pressure in terms of flood and waterlog control and water environment protection. The use of tidal range for inland river diversion and drainage by the sluices along outer river is an effective way to enhance the flood control and drainage capacity of tidal river network and improve its water environment quality. However, the development of riverside industries along outer river is in contradiction with the water diversion and drainage of tidal river network. For arguing the new construction of Huisheng Heavy Industry 3# Outfitting Wharf near the gate of Nantong Farm Sluice, in this paper, mathematical models were used to investigate the influence of the outfitting wharf project on the diversion and drainage of tidal river network, and a generalization of ship into movable gate was proposed. The equivalent treatment method for the analysis of the water blocking effect of the ship and its rationality have been verified; it is concluded that the widening of the dredging measures at the entrance of the outfitting wharf project are beneficial to the drainage of the tidal river network, but are not good for the water diversion of the tidal river network; ship mooring at the entrance has little effect on the diversion and drainage of the tidal river network.
, Available online ,
doi: 10.12170/20220402003
Abstract:
In order to study the influence of interlayer of different components on rainfall infiltration, the differential movement and distribution characteristics of rainwater in the accumulation body were studied. In this paper, a detailed field investigation is carried out on two types of intercalation: clay intercalation and fragmentary stone intercalation developed in the deep deposits in Jiuxiang area of Han Yuan, Sichuan province. By designing two indoor rainfall experiments of gravel interlayer and clay interlayer to monitor the changes of moisture content, matrix suction, pore water pressure and wetting front in the accumulation, the influence of the two types of interlayers on the infiltration process of rainfall in the accumulation was deeply studied. The results show that: (1) Due to the different particle composition of the interlayer, the permeability, wetting front migration morphology, infiltration rate, and the soaking time of the entire stack are ultimately significantly different. (2) There were significant differences in rainwater infiltration between the two groups of sandwich tests. The infiltration effect of the gravel group is stronger than the lateral diffusion, and the infiltration rate at the interlayer is significantly faster than that on both sides; while the lateral diffusion of the clay group is stronger than the infiltration, and the infiltration rate at the interlayer tends to zero, which is significantly lower than that on both sides. (3)The pore pressure at the foot of the slope in the clay group increases cumulatively, while the pore pressure in the gravel group dissipates rapidly, and the water is mainly distributed in the deeper layers of the accumulation, so the overall stability of the clay interlayer accumulation is lower than that of the gravel interlayer accumulation. The research results can provide a basis for analyzing the influence of subsequent rainfall on the stability of slope with weak interlayer.
In order to study the influence of interlayer of different components on rainfall infiltration, the differential movement and distribution characteristics of rainwater in the accumulation body were studied. In this paper, a detailed field investigation is carried out on two types of intercalation: clay intercalation and fragmentary stone intercalation developed in the deep deposits in Jiuxiang area of Han Yuan, Sichuan province. By designing two indoor rainfall experiments of gravel interlayer and clay interlayer to monitor the changes of moisture content, matrix suction, pore water pressure and wetting front in the accumulation, the influence of the two types of interlayers on the infiltration process of rainfall in the accumulation was deeply studied. The results show that: (1) Due to the different particle composition of the interlayer, the permeability, wetting front migration morphology, infiltration rate, and the soaking time of the entire stack are ultimately significantly different. (2) There were significant differences in rainwater infiltration between the two groups of sandwich tests. The infiltration effect of the gravel group is stronger than the lateral diffusion, and the infiltration rate at the interlayer is significantly faster than that on both sides; while the lateral diffusion of the clay group is stronger than the infiltration, and the infiltration rate at the interlayer tends to zero, which is significantly lower than that on both sides. (3)The pore pressure at the foot of the slope in the clay group increases cumulatively, while the pore pressure in the gravel group dissipates rapidly, and the water is mainly distributed in the deeper layers of the accumulation, so the overall stability of the clay interlayer accumulation is lower than that of the gravel interlayer accumulation. The research results can provide a basis for analyzing the influence of subsequent rainfall on the stability of slope with weak interlayer.
, Available online ,
doi: 10.12170/20220106004
Abstract:
The cascade regulation of Qingjiang river based on historical runoff is difficult to adapt to the needs of climate change, which will inevitably affect the safe and stable operation of cascade reservoirs and the development of profits. The SWAT model was built based on the spatial data and observation data of qingjiang Basin, and the future meteorological data of each station in the basin under the three scenarios were simulated by using the statistical downscale model. Then the runoff was simulated, and the power generation change of Geheyan Hydropower station was analyzed. The results show that the simulated annual average runoff of Changyang station under three climate scenarios of RCP2.6, RCP4.5 and RCP8.5 in the future is on the rise, and the annual average runoff increase is 6.0%, 8.7% and 13.2%, respectively. Under the above three scenarios, the average generation capacity of Geheyan Hydropower Station increases by 3.4%~5.1%, 7.7%~10.3% and 13.4%~16.0% in the 2020s, 2050s and 2080s, respectively. This study can provide theoretical reference for water resources management and power generation operation of Geheyan Hydropower station in Qingjiang River Basin under climate change.
The cascade regulation of Qingjiang river based on historical runoff is difficult to adapt to the needs of climate change, which will inevitably affect the safe and stable operation of cascade reservoirs and the development of profits. The SWAT model was built based on the spatial data and observation data of qingjiang Basin, and the future meteorological data of each station in the basin under the three scenarios were simulated by using the statistical downscale model. Then the runoff was simulated, and the power generation change of Geheyan Hydropower station was analyzed. The results show that the simulated annual average runoff of Changyang station under three climate scenarios of RCP2.6, RCP4.5 and RCP8.5 in the future is on the rise, and the annual average runoff increase is 6.0%, 8.7% and 13.2%, respectively. Under the above three scenarios, the average generation capacity of Geheyan Hydropower Station increases by 3.4%~5.1%, 7.7%~10.3% and 13.4%~16.0% in the 2020s, 2050s and 2080s, respectively. This study can provide theoretical reference for water resources management and power generation operation of Geheyan Hydropower station in Qingjiang River Basin under climate change.
, Available online ,
doi: 10.12170/20220129002
Abstract:
As a very soft and problematic engineering material, marine soft clay is characterized by high water content, low bearing capacity, and high compressibility, and widely distributed off the coast of Hangzhou city. It is of great importance to investigate the consolidation creep behavior for the group stability analysis. A series of one-dimensional consolidation tests were carried out on Hangzhou reconstituted soft clay specimens using the GDSAOS automatic oedometer to investigate the preloading effect on the creep behavior. The results indicate that the creep deformation of the soil increases with a decelerating rate during the multi-stage loading under different preloading conditions. The vertical strain and void ratio evolve in a similar trend during the primary consolidation. Preloading can be applied to increase the degree of soil consolidation, thereby improving the stability of structures in actual projects. The study found that the secondary consolidation coefficient depends on both the loading increment ratio and preloading conditions. The smaller the loading increment ratio, the more obvious the growth of the secondary consolidation coefficient in the later loading; the larger the preloading magnitude, the smaller the value of the secondary consolidation coefficient in the early stage of multi-stage loading. The research results have reference significance for the safety of structures in the same type of soft clay area.
As a very soft and problematic engineering material, marine soft clay is characterized by high water content, low bearing capacity, and high compressibility, and widely distributed off the coast of Hangzhou city. It is of great importance to investigate the consolidation creep behavior for the group stability analysis. A series of one-dimensional consolidation tests were carried out on Hangzhou reconstituted soft clay specimens using the GDSAOS automatic oedometer to investigate the preloading effect on the creep behavior. The results indicate that the creep deformation of the soil increases with a decelerating rate during the multi-stage loading under different preloading conditions. The vertical strain and void ratio evolve in a similar trend during the primary consolidation. Preloading can be applied to increase the degree of soil consolidation, thereby improving the stability of structures in actual projects. The study found that the secondary consolidation coefficient depends on both the loading increment ratio and preloading conditions. The smaller the loading increment ratio, the more obvious the growth of the secondary consolidation coefficient in the later loading; the larger the preloading magnitude, the smaller the value of the secondary consolidation coefficient in the early stage of multi-stage loading. The research results have reference significance for the safety of structures in the same type of soft clay area.
, Available online ,
doi: 10.12170/20220330001
Abstract:
During the construction of a pumping station, the deformation monitoring of the steel template for its suction boxes is of great importance to guarantee the safe operation of pumps. Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) method is applied for the pump deformation monitoring to overcome the shortcomings of traditional methods with regard to poor adaptability to complicated shaped surfaces and the constraints of environmental factors. A temperature compensation method is proposed to solve the problem that the Brillouin frequency shift is sensitive to both temperature and strain. An improved conjugated beam method is then adopted to convert the strain after removing the temperature effect to structural deformation. The method is successfully applied to the deformation monitoring of steel templates for suction boxes of a drainage pumping station. The results show that tensile strain and deformation were occurred on the top and both sides of the steel templates, which increased during concrete pouring and stabilized after completion. The feasibility and superiority of the proposed method is validated, which provides an important reference for the research and application of structural deformation monitoring.
During the construction of a pumping station, the deformation monitoring of the steel template for its suction boxes is of great importance to guarantee the safe operation of pumps. Pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) method is applied for the pump deformation monitoring to overcome the shortcomings of traditional methods with regard to poor adaptability to complicated shaped surfaces and the constraints of environmental factors. A temperature compensation method is proposed to solve the problem that the Brillouin frequency shift is sensitive to both temperature and strain. An improved conjugated beam method is then adopted to convert the strain after removing the temperature effect to structural deformation. The method is successfully applied to the deformation monitoring of steel templates for suction boxes of a drainage pumping station. The results show that tensile strain and deformation were occurred on the top and both sides of the steel templates, which increased during concrete pouring and stabilized after completion. The feasibility and superiority of the proposed method is validated, which provides an important reference for the research and application of structural deformation monitoring.
, Available online ,
doi: 10.12170/20220111003
Abstract:
Urban waterlogging has become an important disaster that threatens people’s lives and property. As China enters the era of "stock planning", urban renewal has become an important way to optimize spatial layout and solve urban problems. Existing studies have shown that land expansion and land use layout are important causes of urban waterlogging. The optimization of urban space layout has positive significance for alleviating waterlogging. Aiming at the innovation of the application mode of urban layout optimization in urban renewal planning under waterlogging prevention, we proposed an urban renewal planning path for alleviating waterlogging by constructing an urban spatial layout optimization model. Taking Foshan, China as an example, the model reduce the impact of urban building layout on surface runoff by 18.11% on average. The optimization process did not change the surface space on a large scale. An urban renewal planning model for alleviating waterlogging was proposed. The above work is expected to be realized through the control of total building density and the adjustment of urban surface layout in urban renewal planning work.
Urban waterlogging has become an important disaster that threatens people’s lives and property. As China enters the era of "stock planning", urban renewal has become an important way to optimize spatial layout and solve urban problems. Existing studies have shown that land expansion and land use layout are important causes of urban waterlogging. The optimization of urban space layout has positive significance for alleviating waterlogging. Aiming at the innovation of the application mode of urban layout optimization in urban renewal planning under waterlogging prevention, we proposed an urban renewal planning path for alleviating waterlogging by constructing an urban spatial layout optimization model. Taking Foshan, China as an example, the model reduce the impact of urban building layout on surface runoff by 18.11% on average. The optimization process did not change the surface space on a large scale. An urban renewal planning model for alleviating waterlogging was proposed. The above work is expected to be realized through the control of total building density and the adjustment of urban surface layout in urban renewal planning work.
, Available online ,
doi: 10.12170/20220303003
Abstract:
In the actual working conditions, the concrete of the ship lock is affected by the friction and collision of the ship's hull and the erosion and wear of the ship's traveling wave during the rising water period, and is damaged by CO2 in the air during the falling water period. In order to study the performance degradation law of the ship lock concrete under this working condition, the underwater steel ball method was used to approximate the physical wear of the ship lock concrete in the rising water period, and the rapid carbonation test was used to simulate the CO2 erosion in the falling water period. The duration of abrasion and carbonization, as well as the alternate cycle mechanism, are determined according to the design service index of the lock and the characteristics of navigability. The engineering performance degradation law of the ship lock concrete is reflected by the carbonation depth and anti-abrasion strength, and the composition and pore structure evolution of the ship lock concrete is characterized based on the thermalgravimetric analysis and mercury intrusion porosimetry. The simulation test and analysis show that the concrete of the inland ship lock exhibits a more obvious deterioration trend under the action of surface physical wear and carbonization cycle, and the abrasion accelerates the carbonization reaction to a certain extent.
In the actual working conditions, the concrete of the ship lock is affected by the friction and collision of the ship's hull and the erosion and wear of the ship's traveling wave during the rising water period, and is damaged by CO2 in the air during the falling water period. In order to study the performance degradation law of the ship lock concrete under this working condition, the underwater steel ball method was used to approximate the physical wear of the ship lock concrete in the rising water period, and the rapid carbonation test was used to simulate the CO2 erosion in the falling water period. The duration of abrasion and carbonization, as well as the alternate cycle mechanism, are determined according to the design service index of the lock and the characteristics of navigability. The engineering performance degradation law of the ship lock concrete is reflected by the carbonation depth and anti-abrasion strength, and the composition and pore structure evolution of the ship lock concrete is characterized based on the thermalgravimetric analysis and mercury intrusion porosimetry. The simulation test and analysis show that the concrete of the inland ship lock exhibits a more obvious deterioration trend under the action of surface physical wear and carbonization cycle, and the abrasion accelerates the carbonization reaction to a certain extent.
, Available online ,
doi: 10.12170/20220826001
Abstract:
The analysis of crack initiation and instability propagation of dam concrete needs to simulate the weak discontinuity between aggregate and mortar as accurately as possible. The micron thickness of the interface transition zone makes the finite element mesh have the problems of poor mesh generation quality and large number of meshes. Zero-thickness cohesive interface elements were preset between the solid elements of different material interface. Reassembling subdomain interface configurations after presetting zero-thickness interface elements. Then the aggregate-mortar-interface multi-scale domain decomposition finite element mesh were established. Meanwhile, the gradient-enhanced continuum damage model and the cohesion model were combined to simulate the failure of aggregate and mortar matrix, also the weak link between the aggregate and cement matrix in one model. A macro-meso concurrent multi-scale domain decomposition model for discontinuous deformation of dam concrete was constructed. The model was applied to the direct tensile test simulation of a dam concrete. Both of the random aggregate models could capture the whole process from weak connection to disconnection of the interface between aggregate and mortar. The failure modes reproduced of concrete specimen were in agreement with the result of reference paper, proving that the model is reasonable, which can provide numerical test technical support for the study of damage and fracture mechanical properties of dam concrete.
The analysis of crack initiation and instability propagation of dam concrete needs to simulate the weak discontinuity between aggregate and mortar as accurately as possible. The micron thickness of the interface transition zone makes the finite element mesh have the problems of poor mesh generation quality and large number of meshes. Zero-thickness cohesive interface elements were preset between the solid elements of different material interface. Reassembling subdomain interface configurations after presetting zero-thickness interface elements. Then the aggregate-mortar-interface multi-scale domain decomposition finite element mesh were established. Meanwhile, the gradient-enhanced continuum damage model and the cohesion model were combined to simulate the failure of aggregate and mortar matrix, also the weak link between the aggregate and cement matrix in one model. A macro-meso concurrent multi-scale domain decomposition model for discontinuous deformation of dam concrete was constructed. The model was applied to the direct tensile test simulation of a dam concrete. Both of the random aggregate models could capture the whole process from weak connection to disconnection of the interface between aggregate and mortar. The failure modes reproduced of concrete specimen were in agreement with the result of reference paper, proving that the model is reasonable, which can provide numerical test technical support for the study of damage and fracture mechanical properties of dam concrete.
, Available online ,
doi: 10.12170/20220615001
Abstract:
The research on the characteristics of water increase along the sea crossing transportation facilities under the action of storm surge is of great significance to the disaster prevention and mitigation and structural safety assessment during the operation and maintenance period of transportation projects. Based on the measured typhoon data from 1951 to 2020, the variation characteristics of typhoon parameters in different ranges centered on Hong Kong-Zhuhai-Macao Bridge are statistically analyzed. It is found that the annual average number of typhoons, the maximum wind speed of typhoons and the minimum pressure in the center of typhoons in the waters near the Pearl River Estuary have not changed significantly since 1951. The storm surge mathematical model in the Western Pacific is established, and the characteristic values of storm surge in different areas along the Hong Kong-Zhuhai-Macao Bridge are calculated. The research shows that the storm surge of the Hong Kong-Zhuhai-Macao Bridge gradually decreases from west to East. The 200 years storm surge at the Zhuhai-Macao artificial island on the west side of the bridge is 3.17 m, the 50 years is 2.31 m, and the 200 years storm surge at the East-West artificial island is about 2.30 m, the 50 years is about 1.70 m. The research results can provide technical support for the safety assessment of Hong Kong Zhuhai Macao Bridge during operation and maintenance period.
The research on the characteristics of water increase along the sea crossing transportation facilities under the action of storm surge is of great significance to the disaster prevention and mitigation and structural safety assessment during the operation and maintenance period of transportation projects. Based on the measured typhoon data from 1951 to 2020, the variation characteristics of typhoon parameters in different ranges centered on Hong Kong-Zhuhai-Macao Bridge are statistically analyzed. It is found that the annual average number of typhoons, the maximum wind speed of typhoons and the minimum pressure in the center of typhoons in the waters near the Pearl River Estuary have not changed significantly since 1951. The storm surge mathematical model in the Western Pacific is established, and the characteristic values of storm surge in different areas along the Hong Kong-Zhuhai-Macao Bridge are calculated. The research shows that the storm surge of the Hong Kong-Zhuhai-Macao Bridge gradually decreases from west to East. The 200 years storm surge at the Zhuhai-Macao artificial island on the west side of the bridge is 3.17 m, the 50 years is 2.31 m, and the 200 years storm surge at the East-West artificial island is about 2.30 m, the 50 years is about 1.70 m. The research results can provide technical support for the safety assessment of Hong Kong Zhuhai Macao Bridge during operation and maintenance period.
, Available online ,
doi: 10.12170/20220410003
Abstract:
In order to further study the external characteristics of axial flow pump device with volute outlet channel, ensuring the safe and stable operation of Jiangou pump station after construction, the hydraulic performance of Jiangou pump station was studied based on the model test and its operation scheme of was optimized. The result shows that when the pump station works with the blade angle of −2 °, the pump device could operate with the highest efficiency of 71.4% in which case the flow and head are similar to the designed condition, indicating that it can be used as the designed angle for the future operation of the pump station. With the gradual increase of head, the flow decreases gently which has satisfied the economic requirements of long-time and large flow drainage of the pumping station. Additionally, the cavitation performance of the pump device has met the design requirements and when the blade angle is −4 °, the runaway speed reaches the highest value which is less than twice the rated speed in which case the runaway characteristics are excellent. In conclusion, the performance of the pump device tested is relatively excellent as a drainage pump device which has the great value of in-depth research and development. This study can provide some reference for the design of drainage engineerings with similar heads and large flow rates.
In order to further study the external characteristics of axial flow pump device with volute outlet channel, ensuring the safe and stable operation of Jiangou pump station after construction, the hydraulic performance of Jiangou pump station was studied based on the model test and its operation scheme of was optimized. The result shows that when the pump station works with the blade angle of −2 °, the pump device could operate with the highest efficiency of 71.4% in which case the flow and head are similar to the designed condition, indicating that it can be used as the designed angle for the future operation of the pump station. With the gradual increase of head, the flow decreases gently which has satisfied the economic requirements of long-time and large flow drainage of the pumping station. Additionally, the cavitation performance of the pump device has met the design requirements and when the blade angle is −4 °, the runaway speed reaches the highest value which is less than twice the rated speed in which case the runaway characteristics are excellent. In conclusion, the performance of the pump device tested is relatively excellent as a drainage pump device which has the great value of in-depth research and development. This study can provide some reference for the design of drainage engineerings with similar heads and large flow rates.
, Available online ,
doi: 10.12170/20210805001
Abstract:
Alkali-aggregate reaction is called the "cancer" of concrete and is one of the important factors affecting the durability of concrete. For the concrete structure with active aggregate, how to predict the long-term deformation of concrete caused by alkali-aggregate reaction and reasonably evaluate the overall safety of the structure is a problem of close concern to the project. In this paper, the research progress of long term deformation prediction models for alkali-aggregate reaction of concrete is reviewed. The existing models are classified into 5 categories: mathematical modeling of macroscopic expansion, phenomenological model of macroscopical deformation of structures, models based on aggregate expansion, models based on ASR gel and models based on material migration. The advantages, disadvantages and application scope of various models are analyzed. It is proposed that the prediction model of ASR long-term expansion needs to consider the effect of alkali ion diffusion into the aggregate, SiO2 dissolution and the composition of ASR gel, and the reaction ring model or gel pocket model should be selected according to the petrographic analysis.
Alkali-aggregate reaction is called the "cancer" of concrete and is one of the important factors affecting the durability of concrete. For the concrete structure with active aggregate, how to predict the long-term deformation of concrete caused by alkali-aggregate reaction and reasonably evaluate the overall safety of the structure is a problem of close concern to the project. In this paper, the research progress of long term deformation prediction models for alkali-aggregate reaction of concrete is reviewed. The existing models are classified into 5 categories: mathematical modeling of macroscopic expansion, phenomenological model of macroscopical deformation of structures, models based on aggregate expansion, models based on ASR gel and models based on material migration. The advantages, disadvantages and application scope of various models are analyzed. It is proposed that the prediction model of ASR long-term expansion needs to consider the effect of alkali ion diffusion into the aggregate, SiO2 dissolution and the composition of ASR gel, and the reaction ring model or gel pocket model should be selected according to the petrographic analysis.
, Available online ,
doi: 10.12170/20210114001
Abstract:
The research on the occurrence regularity of the drought-flood abrupt alternation in Haihe River Basin can provide scientific reference for flood control and drought relief. Based on the daily precipitation data of 159 meteorological stations in Haihe River Basin from 1961 to 2019, the Standardized Antecedent Precipitation Index (SAPI) is calculated. Based on the SAPI, according to the drought-flood grade standard and drought-flood abrupt alternation conditions, the drought-flood abrupt alternation events since 1961 are screened out, and the frequency and intensity characteristics of drought-flood abrupt alternation in Haihe River Basin are analyzed. The results show that the annual average frequency of drought-flood abrupt alternation in Haihe River Basin is 33 times, which basically increases year by year, with an average of 37 times in recent 10 years. The intensity of drought-flood abrupt alternation also showed an upward trend, and increased to above the average value after 2000; it showed a jumping increase with reaching the maximum value especially in recent 10 years. The drought-flood abrupt alternation occurred mostly in May, June and mid September, and less in midsummer. The intensity of drought-flood abrupt alternation presents a single peak distribution, and the maximum value appears from the middle of June to the first ten days of July. The corresponding frequency of drought-flood abrupt alternation is also more in this period, which increases the risk of flood disaster. From the perspective of spatial distribution, the frequency and intensity of drought-flood abrupt alternation are high value areas in the southern part of Luanhe River system, the western part of Beisanhe River system and the central part of TuhaiMajia River. That is to say, the frequency and intensity of drought-flood abrupt alternation are high in these areas, consequently, the risk of drought-flood abrupt alternation is high. These areas may become the focus of flood control.
The research on the occurrence regularity of the drought-flood abrupt alternation in Haihe River Basin can provide scientific reference for flood control and drought relief. Based on the daily precipitation data of 159 meteorological stations in Haihe River Basin from 1961 to 2019, the Standardized Antecedent Precipitation Index (SAPI) is calculated. Based on the SAPI, according to the drought-flood grade standard and drought-flood abrupt alternation conditions, the drought-flood abrupt alternation events since 1961 are screened out, and the frequency and intensity characteristics of drought-flood abrupt alternation in Haihe River Basin are analyzed. The results show that the annual average frequency of drought-flood abrupt alternation in Haihe River Basin is 33 times, which basically increases year by year, with an average of 37 times in recent 10 years. The intensity of drought-flood abrupt alternation also showed an upward trend, and increased to above the average value after 2000; it showed a jumping increase with reaching the maximum value especially in recent 10 years. The drought-flood abrupt alternation occurred mostly in May, June and mid September, and less in midsummer. The intensity of drought-flood abrupt alternation presents a single peak distribution, and the maximum value appears from the middle of June to the first ten days of July. The corresponding frequency of drought-flood abrupt alternation is also more in this period, which increases the risk of flood disaster. From the perspective of spatial distribution, the frequency and intensity of drought-flood abrupt alternation are high value areas in the southern part of Luanhe River system, the western part of Beisanhe River system and the central part of TuhaiMajia River. That is to say, the frequency and intensity of drought-flood abrupt alternation are high in these areas, consequently, the risk of drought-flood abrupt alternation is high. These areas may become the focus of flood control.
, Available online ,
doi: 10.12170/20190322001
Abstract:
In order to study the change of pore water pressure of concrete in the water pressure environment, the experiment of pore water pressure change of the concrete under different water pressure was carried out. Based on the test data, the transient inversion numerical simulation of pore water pressure variation of concrete under different water pressure is carried out by using the finite element software ANSYS, and the results are compared with the experimental results. The research results show that under the action of water pressure, the change characteristics of pore water pressure of concrete can be divided into three stages: the rapid increase stage, the slow increase stage and the stabilization stage. When the concrete is under the water pressure of 0.875 MPa, the pore water pressure of the concrete reaches the value equal to the applied water pressure for more than 9 h. The variation law of pore water pressure of concrete is in good agreement with the experimental data by using the finite element software ANSYS for numerical simulation.
In order to study the change of pore water pressure of concrete in the water pressure environment, the experiment of pore water pressure change of the concrete under different water pressure was carried out. Based on the test data, the transient inversion numerical simulation of pore water pressure variation of concrete under different water pressure is carried out by using the finite element software ANSYS, and the results are compared with the experimental results. The research results show that under the action of water pressure, the change characteristics of pore water pressure of concrete can be divided into three stages: the rapid increase stage, the slow increase stage and the stabilization stage. When the concrete is under the water pressure of 0.875 MPa, the pore water pressure of the concrete reaches the value equal to the applied water pressure for more than 9 h. The variation law of pore water pressure of concrete is in good agreement with the experimental data by using the finite element software ANSYS for numerical simulation.
Display Method:
2023, (1): 1-15.
doi: 10.12170/20220919001
Abstract:
This paper introduces the basic information of dam failures in China and analyzes representative major dam failure events in different eras. Systematic statistic analysis has been carried out for 3558 dams that failed in history ever since dam failure record was first available in 1954, as well as the life loss data, according to the era, dam scale, dam type, dam height, season, construction and operation period, and geographic region. It reveales the spatiotemporal distribution characteristics and social attributes of dam failures and their loss of lives, summarizes and analyzes the main reasons of dam failures. Based on the statistical analysis, dam failure lessons have been summed up, and countermeasures to prevent dam failure have been proposed. The results of this paper have reference significance for further improving the prevention and control system of reservoir dam failure in China and strictly preventing dam failure accidents.
This paper introduces the basic information of dam failures in China and analyzes representative major dam failure events in different eras. Systematic statistic analysis has been carried out for 3558 dams that failed in history ever since dam failure record was first available in 1954, as well as the life loss data, according to the era, dam scale, dam type, dam height, season, construction and operation period, and geographic region. It reveales the spatiotemporal distribution characteristics and social attributes of dam failures and their loss of lives, summarizes and analyzes the main reasons of dam failures. Based on the statistical analysis, dam failure lessons have been summed up, and countermeasures to prevent dam failure have been proposed. The results of this paper have reference significance for further improving the prevention and control system of reservoir dam failure in China and strictly preventing dam failure accidents.
2023, (1): 16-26.
doi: 10.12170/20211203005
Abstract:
Several superhigh arch dams have been built or are under construction in China. These projects are often located in special service environments with high water head, high slope and complex geological conditions. Their technical indicators have broken through the applicable scope of current codes and previous engineering cognition, including design, construction, safety monitoring, etc. Compared with ordinary arch dams, the engineering complexity of superhigh arch dams increases sharply with the dam height, and the structural mechanical behavior has more unique characteristics, leading to stringent requirements of safety control during construction and operation. The key technologies of structural behavior diagnosis of superhigh arch dams have been explored systematically, such as engineering empirical evaluation parameters, geomechanical model tests, numerical simulation analysis. Furthermore, safety control technologies have been deeply investigated, including construction quality control, temperature control and crack prevention, monitoring feedback analysis. On this basis, hot issues of health diagnosis and safety control of superhigh arch dams during future long-term operation are expounded, including the mining of methods of space-time evolution characteristics, real-time diagnosis model of operation risk probability, dynamic control model of structural safety, intelligent perception and early warning technology. The aforementioned research aspects are critical for improving the future intelligent construction and management of superhigh arch dams.
Several superhigh arch dams have been built or are under construction in China. These projects are often located in special service environments with high water head, high slope and complex geological conditions. Their technical indicators have broken through the applicable scope of current codes and previous engineering cognition, including design, construction, safety monitoring, etc. Compared with ordinary arch dams, the engineering complexity of superhigh arch dams increases sharply with the dam height, and the structural mechanical behavior has more unique characteristics, leading to stringent requirements of safety control during construction and operation. The key technologies of structural behavior diagnosis of superhigh arch dams have been explored systematically, such as engineering empirical evaluation parameters, geomechanical model tests, numerical simulation analysis. Furthermore, safety control technologies have been deeply investigated, including construction quality control, temperature control and crack prevention, monitoring feedback analysis. On this basis, hot issues of health diagnosis and safety control of superhigh arch dams during future long-term operation are expounded, including the mining of methods of space-time evolution characteristics, real-time diagnosis model of operation risk probability, dynamic control model of structural safety, intelligent perception and early warning technology. The aforementioned research aspects are critical for improving the future intelligent construction and management of superhigh arch dams.
2023, (1): 27-33.
doi: 10.12170/20211024002
Abstract:
Affected by extreme weathers, dam failures and accidents occurred in recent years, and some regularity trend is gradually clear. Some new phenomena and new directions such as the excessive flood impact, earth-rock dam overtopping with not collapse, emergency response mechanism and so on should be studied deeply. It is necessary to analyze and study the latest dam-break and escape cases. This paper summarizes experience and draws lessons from flood control standards, monitoring and early warning, emergency response and emergency treatment, and puts forward some enlightenments in reservoir dam safety management and flood control, and further puts forward thoughts and suggestions on strengthening dam failure risk prevention and control. Conclusion: quickly lowering water level is the key to deal with the excessive flood; earth dam can be overtopped without collapse; earth and rockfill dam structure design should give full consideration to the extreme working condition of strong rainfall; it is necessary to strengthen the flood control capacity for river cascade reservoirs; management facilities have a great influence on emergency response ability; and low-level management influences the flood control safety significantly.
Affected by extreme weathers, dam failures and accidents occurred in recent years, and some regularity trend is gradually clear. Some new phenomena and new directions such as the excessive flood impact, earth-rock dam overtopping with not collapse, emergency response mechanism and so on should be studied deeply. It is necessary to analyze and study the latest dam-break and escape cases. This paper summarizes experience and draws lessons from flood control standards, monitoring and early warning, emergency response and emergency treatment, and puts forward some enlightenments in reservoir dam safety management and flood control, and further puts forward thoughts and suggestions on strengthening dam failure risk prevention and control. Conclusion: quickly lowering water level is the key to deal with the excessive flood; earth dam can be overtopped without collapse; earth and rockfill dam structure design should give full consideration to the extreme working condition of strong rainfall; it is necessary to strengthen the flood control capacity for river cascade reservoirs; management facilities have a great influence on emergency response ability; and low-level management influences the flood control safety significantly.
2023, (1): 34-42.
doi: 10.12170/20211021002
Abstract:
The anti-sliding stability is the most basic requirement for gravity dams. It can be regarded as the abnormal deformation behavior. The traditional ways to determine the early-warning value of dam deformation safety are commonly based on deterministic structure parameters and mathematical models. The uncertainty characteristics of the relevant influencing factors lack consideration. In order to solve the above problem, the theory of uncertainty analysis is applied. In this paper, the response surface method is introduced to fit the functional relation between the water pressure component of gravity dam deformation and the anti-sliding stability reliability index based on the analysis of the correlation between dam deformation, anti-sliding stability reliability index and water depth before the dam. According to the current reliability design specification, an anti-sliding stability reliability index-based approach determining the early-warning value of deformation safety for gravity dam is proposed and verified in the actual engineering case. The rationality of the conclusion is proved by comparing with the result of the typical small probability method. The proposed method can be regarded as useful complements and mutual verification means for the traditional methods.
The anti-sliding stability is the most basic requirement for gravity dams. It can be regarded as the abnormal deformation behavior. The traditional ways to determine the early-warning value of dam deformation safety are commonly based on deterministic structure parameters and mathematical models. The uncertainty characteristics of the relevant influencing factors lack consideration. In order to solve the above problem, the theory of uncertainty analysis is applied. In this paper, the response surface method is introduced to fit the functional relation between the water pressure component of gravity dam deformation and the anti-sliding stability reliability index based on the analysis of the correlation between dam deformation, anti-sliding stability reliability index and water depth before the dam. According to the current reliability design specification, an anti-sliding stability reliability index-based approach determining the early-warning value of deformation safety for gravity dam is proposed and verified in the actual engineering case. The rationality of the conclusion is proved by comparing with the result of the typical small probability method. The proposed method can be regarded as useful complements and mutual verification means for the traditional methods.
2023, (1): 43-52.
doi: 10.12170/20220228002
Abstract:
With the global warming, the sea level is rising at an accelerated rate. The Yangtze River estuary, located in the northwest edge of the storm basin in the northwest Pacific Ocean, with a low-lying terrain, is assessed as a vulnerable area under the impact of storm surge disasters. In order to study the changes of storm tide levels in the reach below Jiangyin of the Yangtze River after sea level rise, a refined mathematical model was established for the astronomical tide-storm surge coupling in the Yangtze River estuary. The model simulated and analyzed the response law of astronomical tides and storm surge near the Yangtze River estuary after sea level rise under the action of two typical typhoons, No.9711 (Winnie) and No.1509 (Chan-hom). The study shows that in the next 100 years, the average tidal level of the Yangtze River estuary will rise by 50~80 cm after the sea level rises by 70 cm. The extreme value of water increment in the reach below Jiangyin and near the shore area of the Yangtze estuary will decrease slightly. The extreme value of water increment will first increase and then decrease from Jiangyin in the upstream to Niupi Reef in the downstream. The specific location along the way of the extreme value of water increase is closely related to the typhoon path and typhoon intensity. The study can provide a theoretical basis for flood control and waterlogging drainage of towns along the Yangtze River estuary in the medium and long term.
With the global warming, the sea level is rising at an accelerated rate. The Yangtze River estuary, located in the northwest edge of the storm basin in the northwest Pacific Ocean, with a low-lying terrain, is assessed as a vulnerable area under the impact of storm surge disasters. In order to study the changes of storm tide levels in the reach below Jiangyin of the Yangtze River after sea level rise, a refined mathematical model was established for the astronomical tide-storm surge coupling in the Yangtze River estuary. The model simulated and analyzed the response law of astronomical tides and storm surge near the Yangtze River estuary after sea level rise under the action of two typical typhoons, No.9711 (Winnie) and No.1509 (Chan-hom). The study shows that in the next 100 years, the average tidal level of the Yangtze River estuary will rise by 50~80 cm after the sea level rises by 70 cm. The extreme value of water increment in the reach below Jiangyin and near the shore area of the Yangtze estuary will decrease slightly. The extreme value of water increment will first increase and then decrease from Jiangyin in the upstream to Niupi Reef in the downstream. The specific location along the way of the extreme value of water increase is closely related to the typhoon path and typhoon intensity. The study can provide a theoretical basis for flood control and waterlogging drainage of towns along the Yangtze River estuary in the medium and long term.
2023, (1): 53-62.
doi: 10.12170/20210309004
Abstract:
During the implementation of water conservancy and flood control and disaster mitigation, such as river closure and quick closure of earth-rock dike breaches, a strong local scour would occur at the gap or mouth. A 3D numerical model of local scour was verified by the experiments of previous studies, and this model was applied to simulate the local scour around the dike and the riverbed under the one-way and two-way advancement patterns at the gap width B/H = 4.3 and 5.8. The influence of advancement patterns on the development of local scour around dike was analyzed. The results show that in the case of one-way advancement pattern, the gap flow is deflected by the dike to the other side. The local scour of the upstream dike head is always intense in the whole process. Due to the deflection of the dike, the locations of intense scouring downstream are different. The intense scouring area is located at the bottom of the upstream end of the dike at B/H=5.8, and this area is located at the wrapping head downstream at B/H = 4.3. In the case of two-way advancement pattern, the flow is distributed symmetrically along the gap axis. The gap width only affects the intensity of local scouring on the dike. The diving flow and eddy are the main reasons for local scour around the dike.
During the implementation of water conservancy and flood control and disaster mitigation, such as river closure and quick closure of earth-rock dike breaches, a strong local scour would occur at the gap or mouth. A 3D numerical model of local scour was verified by the experiments of previous studies, and this model was applied to simulate the local scour around the dike and the riverbed under the one-way and two-way advancement patterns at the gap width B/H = 4.3 and 5.8. The influence of advancement patterns on the development of local scour around dike was analyzed. The results show that in the case of one-way advancement pattern, the gap flow is deflected by the dike to the other side. The local scour of the upstream dike head is always intense in the whole process. Due to the deflection of the dike, the locations of intense scouring downstream are different. The intense scouring area is located at the bottom of the upstream end of the dike at B/H=5.8, and this area is located at the wrapping head downstream at B/H = 4.3. In the case of two-way advancement pattern, the flow is distributed symmetrically along the gap axis. The gap width only affects the intensity of local scouring on the dike. The diving flow and eddy are the main reasons for local scour around the dike.
2023, (1): 63-71.
doi: 10.12170/20211129001
Abstract:
It is the sand particle gradation and the sediment mineral composition which affect most the measurement of the suspended sediment concentration with the turbidity method. The field non-cohesive sediment of the Yellow River was used to prepare sandy water with different particle sizes and suspended sediment concentrations. Based on the group of experiments on fixed-size particles of sediment, coarse and fine particles of sediment, and mixed particles of sediment, the influence of the sediment gradation on the measured turbidity of Optical Back Scatteering (OBS) was quantitatively analyzed, and the influencing mechanism was preliminarily discussed. The results show that under the condition of fixed-size particles of sediment, the influence characteristic of non-cohesive sediment particle size on the water turbidity conforms to the Mie scattering law. The magnitude of the impact of the suspended sediment concentration on OBS output turbidity is in the order of 10-102, while the impact of the sediment particle size is in the order of 10−1-1. The relationship of the specific surface area of the suspended sediment and the measured turbidity of OBS accords with linear distribution in the same sediment concentration condition. A formula between the sediment concentration and the OBS output turbidity is established considering the influence of non-cohesive sediment gradation to accurately reflect the impact of non-cohesive sediment particle size differences and sediment concentration changes on water turbidity. This work can provide reliable evidence not only for the accuracy of the calculation of the sediment concentration and water turbidity, but also for the calibration of the measurement results.
It is the sand particle gradation and the sediment mineral composition which affect most the measurement of the suspended sediment concentration with the turbidity method. The field non-cohesive sediment of the Yellow River was used to prepare sandy water with different particle sizes and suspended sediment concentrations. Based on the group of experiments on fixed-size particles of sediment, coarse and fine particles of sediment, and mixed particles of sediment, the influence of the sediment gradation on the measured turbidity of Optical Back Scatteering (OBS) was quantitatively analyzed, and the influencing mechanism was preliminarily discussed. The results show that under the condition of fixed-size particles of sediment, the influence characteristic of non-cohesive sediment particle size on the water turbidity conforms to the Mie scattering law. The magnitude of the impact of the suspended sediment concentration on OBS output turbidity is in the order of 10-102, while the impact of the sediment particle size is in the order of 10−1-1. The relationship of the specific surface area of the suspended sediment and the measured turbidity of OBS accords with linear distribution in the same sediment concentration condition. A formula between the sediment concentration and the OBS output turbidity is established considering the influence of non-cohesive sediment gradation to accurately reflect the impact of non-cohesive sediment particle size differences and sediment concentration changes on water turbidity. This work can provide reliable evidence not only for the accuracy of the calculation of the sediment concentration and water turbidity, but also for the calibration of the measurement results.
2023, (1): 72-82.
doi: 10.12170/20211207002
Abstract:
In order to enrich the theory on development and utilization of landslide dam and explore the feasibility of its improvement and reinforcement, the residual landslide dam caused by Yigong landslide was sampled, the indoor vibroflotation model tests with different frequencies were designed, and the reinforcement effect and compaction mechanism of vibroflotation method on landslide dam material were studied. The sand rain method was used for the sample placement in the model tests to comprehensively test the cumulative dissipation law of pore pressure, the development law of earth pressure, reinforcement effect and repeating vibration effect of the foundation after vibroflotation. The test results indicate that the earth pressure and excess pore pressure in the loose landslide dam material rise rapidly during the penetration of the vibrator. Under the pull-up and segmental vibration retention of the vibrator, the excess pore pressure of the landslide dam material showed a general trend of small rise, dissipation and gradual stability. With the increasing number of vibroflotation (after 2-3 repeated vibrations), the soil pressure of the foundation gradually stabilized, and the peak value of excess pore water pressure gradually decreased and tended to be stable. Therefore, the reinforcement effect of vibroflotation on loose landslide dam material was obvious. After vibroflotation, the cone resistance of landslide dam material was greatly increased. However, after the densification of landslide dam material, the increasing number of repeated vibrations was unable to further improve the reinforcement effect effectively. The vibroflotation reinforcement mechanism of landslide dam material mainly included vibrator squeezing, consolidation drainage, and vibroflotation compaction. The vibroflotation design scheme meeting the requirements of Yigong landslide dam material was: vibroflotation with 125 Hz frequency for 4-5 times or vibroflotation with 150 Hz frequency for 2-3 times. The research results can provide a theoretical basis for vibroflotation reinforcement of landslide dam material foundation.
In order to enrich the theory on development and utilization of landslide dam and explore the feasibility of its improvement and reinforcement, the residual landslide dam caused by Yigong landslide was sampled, the indoor vibroflotation model tests with different frequencies were designed, and the reinforcement effect and compaction mechanism of vibroflotation method on landslide dam material were studied. The sand rain method was used for the sample placement in the model tests to comprehensively test the cumulative dissipation law of pore pressure, the development law of earth pressure, reinforcement effect and repeating vibration effect of the foundation after vibroflotation. The test results indicate that the earth pressure and excess pore pressure in the loose landslide dam material rise rapidly during the penetration of the vibrator. Under the pull-up and segmental vibration retention of the vibrator, the excess pore pressure of the landslide dam material showed a general trend of small rise, dissipation and gradual stability. With the increasing number of vibroflotation (after 2-3 repeated vibrations), the soil pressure of the foundation gradually stabilized, and the peak value of excess pore water pressure gradually decreased and tended to be stable. Therefore, the reinforcement effect of vibroflotation on loose landslide dam material was obvious. After vibroflotation, the cone resistance of landslide dam material was greatly increased. However, after the densification of landslide dam material, the increasing number of repeated vibrations was unable to further improve the reinforcement effect effectively. The vibroflotation reinforcement mechanism of landslide dam material mainly included vibrator squeezing, consolidation drainage, and vibroflotation compaction. The vibroflotation design scheme meeting the requirements of Yigong landslide dam material was: vibroflotation with 125 Hz frequency for 4-5 times or vibroflotation with 150 Hz frequency for 2-3 times. The research results can provide a theoretical basis for vibroflotation reinforcement of landslide dam material foundation.
2023, (1): 83-94.
doi: 10.12170/20211118005
Abstract:
In order to study the effect of freeze-thaw cycles and loading strain rate on the compressive behavior of hydraulic roller compacted concrete, actual mix design and construction technology of hydraulic concrete dam project was considered to prepare specimens, and the freeze-thaw tests with various cycles (0, 25, 50, 75) and dynamic uniaxial compressive tests with different loading strain rates (10−5/s, 10−4/s, 10−3/s, 10−2/s) were conducted for roller compacted concrete. The freeze-thaw appearance and failure mode subjected to dynamic uniaxial compressive loading and freeze-thaw cycles were analyzed. The effects of freeze-thaw cycles and strain rates on uniaxial compressive strength, peak strain and stress-strain curves were studied, and the corresponding relationship was established based on multiple regression analysis method. The results show that the compressive strength increases linearly with the increasing strain rates and reduces with the increasing freeze-thaw cycles in accordance with two-polynomial relation. The peak strain reduces with the increasing strain rates in accordance with two-polynomial relation, and increases with the increasing strain rates in accordance with two-polynomial relation. By comparing the theoretical stress-strain curves obtained from the constitutive model with the experimental curves, it is revealed that they are in good agreement with the studied range of strain rates and freeze-thaw cycles.
In order to study the effect of freeze-thaw cycles and loading strain rate on the compressive behavior of hydraulic roller compacted concrete, actual mix design and construction technology of hydraulic concrete dam project was considered to prepare specimens, and the freeze-thaw tests with various cycles (0, 25, 50, 75) and dynamic uniaxial compressive tests with different loading strain rates (10−5/s, 10−4/s, 10−3/s, 10−2/s) were conducted for roller compacted concrete. The freeze-thaw appearance and failure mode subjected to dynamic uniaxial compressive loading and freeze-thaw cycles were analyzed. The effects of freeze-thaw cycles and strain rates on uniaxial compressive strength, peak strain and stress-strain curves were studied, and the corresponding relationship was established based on multiple regression analysis method. The results show that the compressive strength increases linearly with the increasing strain rates and reduces with the increasing freeze-thaw cycles in accordance with two-polynomial relation. The peak strain reduces with the increasing strain rates in accordance with two-polynomial relation, and increases with the increasing strain rates in accordance with two-polynomial relation. By comparing the theoretical stress-strain curves obtained from the constitutive model with the experimental curves, it is revealed that they are in good agreement with the studied range of strain rates and freeze-thaw cycles.
2023, (1): 95-103.
doi: 10.12170/20211124003
Abstract:
In order to explore the dynamic characteristics of sand gravel under the action of loading ratio, through large-scale dynamic triaxial tests, the change laws of dynamic modulus and damping ratio of sand gravel under different loading ratios and confining pressures is studied, and the influence of different loading ratios and confining pressures on the dynamic parameters of sand gravel was analyzed. The results show that: (1) With the increase of loading ratio, the dynamic strain increases significantly, the pore pressure increases significantly, and the maximum damping ratio increases; (2) The test data can better reflect the variation law of damping ratio with the development of dynamic shear strain. Considering the changes of various dynamic parameters, it is suggested that the selection range of loading ratio of dynamic modulus and damping ratio test of gravel should be 1.5-2.0; (3) The test data with dynamic strain less than 0.01% and dynamic strain greater than 0.01% are fitted by the subsection fitting method. The fitting degree between the straight line and the test point is greater than 0.96, and the subsection fitting is more reasonable under different test conditions; (4) Under different test conditions, the dynamic shear modulus ratio and the reference shear strain have good normalization, and the test data are reliable. Through binary linear regression, the empirical formula of the maximum dynamic shear modulus of gravel about confining pressure and loading ratio is obtained. This method can provide a reference for dynamic triaxial test and data processing of gravel materials.
In order to explore the dynamic characteristics of sand gravel under the action of loading ratio, through large-scale dynamic triaxial tests, the change laws of dynamic modulus and damping ratio of sand gravel under different loading ratios and confining pressures is studied, and the influence of different loading ratios and confining pressures on the dynamic parameters of sand gravel was analyzed. The results show that: (1) With the increase of loading ratio, the dynamic strain increases significantly, the pore pressure increases significantly, and the maximum damping ratio increases; (2) The test data can better reflect the variation law of damping ratio with the development of dynamic shear strain. Considering the changes of various dynamic parameters, it is suggested that the selection range of loading ratio of dynamic modulus and damping ratio test of gravel should be 1.5-2.0; (3) The test data with dynamic strain less than 0.01% and dynamic strain greater than 0.01% are fitted by the subsection fitting method. The fitting degree between the straight line and the test point is greater than 0.96, and the subsection fitting is more reasonable under different test conditions; (4) Under different test conditions, the dynamic shear modulus ratio and the reference shear strain have good normalization, and the test data are reliable. Through binary linear regression, the empirical formula of the maximum dynamic shear modulus of gravel about confining pressure and loading ratio is obtained. This method can provide a reference for dynamic triaxial test and data processing of gravel materials.
2023, (1): 104-111.
doi: 10.12170/20211118003
Abstract:
Controlling the blast-induced damage is of significance for the stability of division pier in the excavation of the large-scale navigation lock. Based on the on-site experiment, the peak particle velocities (PPV) induced by production boreholes were compared, and the damage evolution characteristics were analyzed with the help of the software LS-DYNA. Moreover, through the analysis of the on-site experiment results and numerical results, the blasting excavation scheme of the large-scale navigation lock was optimized. The research results indicate that the rock mass damage induced by production blast-holes will strength the pre-crack vibration isolating effect. With the increase of the width of the blast-induced damage zone, the vibration isolating effect is gradually increased, and finally stabilized at 50%. The attenuation rate of PPV increases with the width of blast-induced damage zone, and when the width of the damage zone reaches 4 cm, the attenuation rate gradually slows down. The damage cumulative characteristics induced by production and pre-splitting crack vibration isolation effect should be taken into consideration in the excavation of the large-scale navigation lock. Therefore, the optimizations of blasting excavation, including the cutting blasting and construction presplitting blasting, were put forward to reduce the blast-induced damage to reserved rock mass and optimize the blasting effect.
Controlling the blast-induced damage is of significance for the stability of division pier in the excavation of the large-scale navigation lock. Based on the on-site experiment, the peak particle velocities (PPV) induced by production boreholes were compared, and the damage evolution characteristics were analyzed with the help of the software LS-DYNA. Moreover, through the analysis of the on-site experiment results and numerical results, the blasting excavation scheme of the large-scale navigation lock was optimized. The research results indicate that the rock mass damage induced by production blast-holes will strength the pre-crack vibration isolating effect. With the increase of the width of the blast-induced damage zone, the vibration isolating effect is gradually increased, and finally stabilized at 50%. The attenuation rate of PPV increases with the width of blast-induced damage zone, and when the width of the damage zone reaches 4 cm, the attenuation rate gradually slows down. The damage cumulative characteristics induced by production and pre-splitting crack vibration isolation effect should be taken into consideration in the excavation of the large-scale navigation lock. Therefore, the optimizations of blasting excavation, including the cutting blasting and construction presplitting blasting, were put forward to reduce the blast-induced damage to reserved rock mass and optimize the blasting effect.
2023, (1): 112-119.
doi: 10.12170/20210801001
Abstract:
To satisfy the demand of spongy city road construction in collapsible loess areas, a kind of cotton stalk fiber EPS particle light soil with light weight, high strength, and certain permeability was developed as a roadbed replacement material. This lightweight soil is a mixture of cotton straw fibers, polystyrene (EPS) granules, cement, loess, and water. In the present study, the density, strength, deformation and permeability of lightweight soil with different cotton stalk fiber contents and lengths, different EPS particle contents and particle sizes, and different cement contents were tested by a series of geotechnical tests. The mixture ratio of cotton stalk fiber EPS particle lightweight soil was designed. The results show that among the various components of lightweight soil, the content of EPS and cement content have the most significant effect on the density. Besides, there is a positive correlation between cement content and strength, and a negative correlation with the permeability coefficient. The EPS content and particle size are negatively correlated with the strength of the lightweight soil, and positively correlated with the permeability coefficient; the addition of cotton stalk fiber improves the plasticity of the lightweight soil and improves the permeability of lightweight soil to a certain extent. The order of magnitude of the effect of various factors on the strength of lightweight soil is: cement content>EPS content and particle size>cotton stalk fiber content and length. The optimal mix ratio of lightweight soil to satisfy the demand of spongy city road construction in collapsible loess areas is: loess soil∶cotton stalk fiber (length 9 mm)∶EPS particles (particle size 0.5-1.0 mm)∶cement∶water = 1,000∶4∶18∶35∶400.
To satisfy the demand of spongy city road construction in collapsible loess areas, a kind of cotton stalk fiber EPS particle light soil with light weight, high strength, and certain permeability was developed as a roadbed replacement material. This lightweight soil is a mixture of cotton straw fibers, polystyrene (EPS) granules, cement, loess, and water. In the present study, the density, strength, deformation and permeability of lightweight soil with different cotton stalk fiber contents and lengths, different EPS particle contents and particle sizes, and different cement contents were tested by a series of geotechnical tests. The mixture ratio of cotton stalk fiber EPS particle lightweight soil was designed. The results show that among the various components of lightweight soil, the content of EPS and cement content have the most significant effect on the density. Besides, there is a positive correlation between cement content and strength, and a negative correlation with the permeability coefficient. The EPS content and particle size are negatively correlated with the strength of the lightweight soil, and positively correlated with the permeability coefficient; the addition of cotton stalk fiber improves the plasticity of the lightweight soil and improves the permeability of lightweight soil to a certain extent. The order of magnitude of the effect of various factors on the strength of lightweight soil is: cement content>EPS content and particle size>cotton stalk fiber content and length. The optimal mix ratio of lightweight soil to satisfy the demand of spongy city road construction in collapsible loess areas is: loess soil∶cotton stalk fiber (length 9 mm)∶EPS particles (particle size 0.5-1.0 mm)∶cement∶water = 1,000∶4∶18∶35∶400.
2023, (1): 120-130.
doi: 10.12170/20211128001
Abstract:
The area of yellow tide soil (YTS) and lime concretion black soil (LCBS) accounts for 87% of the total area of the Northern Anhui Plain, and the LCBS contains calcareous nodules inside, which seriously affect the soil properties and thus reduce the yield. Therefore, in the study, the differences between the two soils were investigated in terms of soil physical and chemical properties, soil hydraulics parameters and soil moisture, and the driving factors affecting the variability of soil moisture in YTS and LCBS were analyzed together with hydro-meteorological factors. The results show that the pH and bulk weight of YTS and LCBS are significantly different, and the contents of total nitrogen, total phosphorus and alkaline solution nitrogen are not significantly different; the effective water holding capacity of YTS from 0 to 50 cm is significantly larger than that of LCBS, and the water retention is better. Soil water of YTS gradually decreases with increasing depth; soil water of LCBS gradually increases with increasing depth. The main drivers affecting soil water variation in YTS are groundwater depth of burial and rainfall; the main drivers affecting soil water variation in LCBS are ground temperature, groundwater depth of burial and relative humidity. This study can provide a reference for improving the soil properties of LCBS and enhancing crop yield.
The area of yellow tide soil (YTS) and lime concretion black soil (LCBS) accounts for 87% of the total area of the Northern Anhui Plain, and the LCBS contains calcareous nodules inside, which seriously affect the soil properties and thus reduce the yield. Therefore, in the study, the differences between the two soils were investigated in terms of soil physical and chemical properties, soil hydraulics parameters and soil moisture, and the driving factors affecting the variability of soil moisture in YTS and LCBS were analyzed together with hydro-meteorological factors. The results show that the pH and bulk weight of YTS and LCBS are significantly different, and the contents of total nitrogen, total phosphorus and alkaline solution nitrogen are not significantly different; the effective water holding capacity of YTS from 0 to 50 cm is significantly larger than that of LCBS, and the water retention is better. Soil water of YTS gradually decreases with increasing depth; soil water of LCBS gradually increases with increasing depth. The main drivers affecting soil water variation in YTS are groundwater depth of burial and rainfall; the main drivers affecting soil water variation in LCBS are ground temperature, groundwater depth of burial and relative humidity. This study can provide a reference for improving the soil properties of LCBS and enhancing crop yield.
2023, (1): 131-139.
doi: 10.12170/20211206001
Abstract:
Based on the combined analysis of soil arching effect and reinforcement effect between piles, an improved Hewlett model for load sharing calculation of geosynthetic-reinforced and pile-supported embankments (GRPSE) is established. Firstly, the governing equations of spherical arch and plane arch are solved respectively, according to whether the soil arch is in a plastic state and combined with the vertical force balance condition of pile-soil, then the load sharing of embankment filling is initially determined. Secondly, the differential equation for controlling the stress balance of the geosynthetic reinforcement can be built and solved without presetting the deflection form, the overlying load of the reinforcement belt is assumed to be an inverted triangle distribution in line with the actual working conditions, and the Winkler foundation model is applied to consider the soil reaction between piles within the influence range of one reinforcement belt. Thereafter, the embankment loading can be redistributed according to the calculated reinforcement effect. It proves that the improved model can reasonably predict the load sharing and the stress results of reinforcement according to the verification and discussion of case studies and the comparative analysis of several models. Parameter analysis shows that the improved model can reasonably predict the influence of geometric and material parameters on load sharing of GRPSE.
Based on the combined analysis of soil arching effect and reinforcement effect between piles, an improved Hewlett model for load sharing calculation of geosynthetic-reinforced and pile-supported embankments (GRPSE) is established. Firstly, the governing equations of spherical arch and plane arch are solved respectively, according to whether the soil arch is in a plastic state and combined with the vertical force balance condition of pile-soil, then the load sharing of embankment filling is initially determined. Secondly, the differential equation for controlling the stress balance of the geosynthetic reinforcement can be built and solved without presetting the deflection form, the overlying load of the reinforcement belt is assumed to be an inverted triangle distribution in line with the actual working conditions, and the Winkler foundation model is applied to consider the soil reaction between piles within the influence range of one reinforcement belt. Thereafter, the embankment loading can be redistributed according to the calculated reinforcement effect. It proves that the improved model can reasonably predict the load sharing and the stress results of reinforcement according to the verification and discussion of case studies and the comparative analysis of several models. Parameter analysis shows that the improved model can reasonably predict the influence of geometric and material parameters on load sharing of GRPSE.
2023, (1): 140-148.
doi: 10.12170/20210903001
Abstract:
In order to study the infiltration law of unsaturated loess, the infiltration model test of remolded loess is carried out, the change of volume moisture content at different positions and the development process of wetting front are analyzed, the development and change law of infiltration water content in horizontal and radial direction is studied, and the infiltration depth at different time is calculated by Green-Ampt model considering air pressure, which is compared with the measured value. The research shows that the change trend of volume moisture content at different measuring points is basically the same, and it would go through six stages: stability-rapid growth-reaching peak-rapid decrease-regrowth-maintaining stability; and the immersion infiltration process is affected by infiltration depth, infiltration path, viscous resistance and air pressure. The deeper the infiltration depth and the farther away from the central axis, the more delayed the development of wetting front and the smaller the infiltration rate. As the depth increases from 0 cm to 100 cm, the infiltration rate decreases from 14.93 cm/h to 1.67 cm/h. The relationship between vertical infiltration rate and infiltration depth at different positions is fitted, and it is found that the vertical infiltration rate and the infiltration depth have a quadratic relationship, and the fitting degree is above 0.9. Radial water migration is the result of the combined action of radial water diffusion and vertical water infiltration in the upper part of the depth, so it is faster than vertical water infiltration. The development trend of wetting front in the model is consistent with the measured vertical infiltration, however, the calculated value of infiltration depth is larger than the measured value at the late infiltration stage. The research results can provide reference for the study of loess foundation infiltration.
In order to study the infiltration law of unsaturated loess, the infiltration model test of remolded loess is carried out, the change of volume moisture content at different positions and the development process of wetting front are analyzed, the development and change law of infiltration water content in horizontal and radial direction is studied, and the infiltration depth at different time is calculated by Green-Ampt model considering air pressure, which is compared with the measured value. The research shows that the change trend of volume moisture content at different measuring points is basically the same, and it would go through six stages: stability-rapid growth-reaching peak-rapid decrease-regrowth-maintaining stability; and the immersion infiltration process is affected by infiltration depth, infiltration path, viscous resistance and air pressure. The deeper the infiltration depth and the farther away from the central axis, the more delayed the development of wetting front and the smaller the infiltration rate. As the depth increases from 0 cm to 100 cm, the infiltration rate decreases from 14.93 cm/h to 1.67 cm/h. The relationship between vertical infiltration rate and infiltration depth at different positions is fitted, and it is found that the vertical infiltration rate and the infiltration depth have a quadratic relationship, and the fitting degree is above 0.9. Radial water migration is the result of the combined action of radial water diffusion and vertical water infiltration in the upper part of the depth, so it is faster than vertical water infiltration. The development trend of wetting front in the model is consistent with the measured vertical infiltration, however, the calculated value of infiltration depth is larger than the measured value at the late infiltration stage. The research results can provide reference for the study of loess foundation infiltration.
2023, (1): 149-160.
doi: 10.12170/20220216004
Abstract:
Rain and flood are valuable natural resources. Utilization of both rain and flood resources has a long history and is one of vital water resources utilization ways. In recent years, practical technologies of rain and flood resources utilization have advanced greatly, but there are still remarkable misunderstandings on their basic conceptions. Extensive use of some nonstandard terms has brought confusion to scientific research and practice. Therefore, in light of the relevant history and reality, and according to the basic theory of hydrology, a discussion on rain and flood resources utilization was carried out and preunderstanding was obtained in this research. The natural resources and water resources properties of rain and flood were clarified. Then, the basic connotation and definition of rain and flood resources utilization were summarized. And finally the relationship between rain resources utilization and flood resources utilization was analyzed. In addition, the normalization of some technical terms including so called rainwater reuse and flood reuse was clarified. This paper is helpful to eliminate the misunderstandings about rain and flood resources utilization and consolidate the theoretical basis of the safe and efficient utilization of rain and flood resources. Our understanding creates good prerequirements for the scientific evaluation, planning and technology innovation of rain and flood resources utilization.
Rain and flood are valuable natural resources. Utilization of both rain and flood resources has a long history and is one of vital water resources utilization ways. In recent years, practical technologies of rain and flood resources utilization have advanced greatly, but there are still remarkable misunderstandings on their basic conceptions. Extensive use of some nonstandard terms has brought confusion to scientific research and practice. Therefore, in light of the relevant history and reality, and according to the basic theory of hydrology, a discussion on rain and flood resources utilization was carried out and preunderstanding was obtained in this research. The natural resources and water resources properties of rain and flood were clarified. Then, the basic connotation and definition of rain and flood resources utilization were summarized. And finally the relationship between rain resources utilization and flood resources utilization was analyzed. In addition, the normalization of some technical terms including so called rainwater reuse and flood reuse was clarified. This paper is helpful to eliminate the misunderstandings about rain and flood resources utilization and consolidate the theoretical basis of the safe and efficient utilization of rain and flood resources. Our understanding creates good prerequirements for the scientific evaluation, planning and technology innovation of rain and flood resources utilization.
2013, (6): 47-53.
2014, (3): 70-76.
Supervisor:Ministry of Water Resources of the People's Republic of China
Sponsor:Nanjing Academy of Water Conservancy Sciences
Editor-in-Chief:Hu Yaan
Address:No. 34 Huluoguan, Nanjing
PostCode:210024
Tel:025-85829135
Email:jnhri@nhri.cn
ISSN:1009-640X
CN:32-1613/TV
Postal Distributing Code: 28-19
Unit-Price: 30 RMB/Issue
Total-Price: 180 RMB/Year
Publication Period: Bimonthly （1979 initial issiue）
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