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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: 10.12170/20230509002
Abstract:
The source area of the Yellow River plays a vital role in water yield and conservation within the Yellow River Basin, impacting socio-economic development along the river's upper, middle, and lower reaches. This study employs the InVEST model to analyze the water yield and conservation capacity of the Yellow River source area from 2000 to 2020. The findings indicate an average annual water yield of 198.8×108 m3 and a water conservation capacity of 35.3×108 m3. Spatially, both water yield and conservation capacity exhibit similar patterns, gradually decreasing from east to west and south to north. Over the study period, both metrics display a significant increasing trend, with growth rates of 3.8 mm/a and 0.7 mm/a, respectively. Notably, the increase varies across regions, ranging from highly significant to no significant change as one moves from the southeast to the northwest. The land use types with the highest to lowest total water conservation capacities are grassland (3.1×109 m3), cropland (3.1×108 m3), wetland (4.9×107 m3), forest (1.6×107 m3), bareland (1.0×107 m3), and urban land (3.1×105 m3). Precipitation serves as the primary driver of water conservation changes, followed by evapotranspiration and land use. Furthermore, the study reveals that an increase in wetland area yields the greatest improvement in water conservation within the Yellow River source area, followed by grassland, while an increase in urban land area provides the least improvement.
The source area of the Yellow River plays a vital role in water yield and conservation within the Yellow River Basin, impacting socio-economic development along the river's upper, middle, and lower reaches. This study employs the InVEST model to analyze the water yield and conservation capacity of the Yellow River source area from 2000 to 2020. The findings indicate an average annual water yield of 198.8×108 m3 and a water conservation capacity of 35.3×108 m3. Spatially, both water yield and conservation capacity exhibit similar patterns, gradually decreasing from east to west and south to north. Over the study period, both metrics display a significant increasing trend, with growth rates of 3.8 mm/a and 0.7 mm/a, respectively. Notably, the increase varies across regions, ranging from highly significant to no significant change as one moves from the southeast to the northwest. The land use types with the highest to lowest total water conservation capacities are grassland (3.1×109 m3), cropland (3.1×108 m3), wetland (4.9×107 m3), forest (1.6×107 m3), bareland (1.0×107 m3), and urban land (3.1×105 m3). Precipitation serves as the primary driver of water conservation changes, followed by evapotranspiration and land use. Furthermore, the study reveals that an increase in wetland area yields the greatest improvement in water conservation within the Yellow River source area, followed by grassland, while an increase in urban land area provides the least improvement.
, Available online ,
doi: 10.12170/20220627001
Abstract:
Structural crack change is one of the important bases to measure the safety state of concrete dams. In view of the problem that the measurement accuracy of traditional vision measurement methods is significantly reduced under the condition of small angle tilt shooting, Based on the equivalent physical model of structural joint change, a new target which can adapt to small angle shooting is designed, and a two-dimensional plane change detection algorithm of structural joint is proposed in this paper. This method uses the cross ratio invariance and the property of vanishing point in projective geometry to correct the perspective deviation of the concentric center of the target, so as to obtain the accurate coordinates of the target feature points, and deduce the change detection algorithm of the structural seam in the x and y directions. In this study, the target is placed on the slide to simulate the changes of structural joints, and the method is tested from many aspects. The indoor verification test results show that the measurement errors of this method in x and y directions are within 0.1 mm under different shooting angles, even small angle shooting conditions. In the field test, the errors in x and y directions are within 0.25 mm, which meets the accuracy requirements of the specification. It can realize the accurate detection of two-dimensional plane changes of structural joints under the condition of small angle shooting, and has engineering application value.
Structural crack change is one of the important bases to measure the safety state of concrete dams. In view of the problem that the measurement accuracy of traditional vision measurement methods is significantly reduced under the condition of small angle tilt shooting, Based on the equivalent physical model of structural joint change, a new target which can adapt to small angle shooting is designed, and a two-dimensional plane change detection algorithm of structural joint is proposed in this paper. This method uses the cross ratio invariance and the property of vanishing point in projective geometry to correct the perspective deviation of the concentric center of the target, so as to obtain the accurate coordinates of the target feature points, and deduce the change detection algorithm of the structural seam in the x and y directions. In this study, the target is placed on the slide to simulate the changes of structural joints, and the method is tested from many aspects. The indoor verification test results show that the measurement errors of this method in x and y directions are within 0.1 mm under different shooting angles, even small angle shooting conditions. In the field test, the errors in x and y directions are within 0.25 mm, which meets the accuracy requirements of the specification. It can realize the accurate detection of two-dimensional plane changes of structural joints under the condition of small angle shooting, and has engineering application value.
, Available online ,
doi: 10.12170/20221026001
Abstract:
With the rapid development of economics and urban integration in coastal areas, the amounts of wading constructions such as sea-crossing bridges and natural disasters-prevention sea-walls increase faster. However, in tidal race waters, severe sectional scour induced by tidal flows often appears around marine structures and has been the main threat to those marine structures. Hence, the real-time monitoring and the study of sectional scouring of bridge piers and seawalls become the key to solve the difficulties. We analyzed the applications as well as the strengths and shortcomings of former technologies of scouring monitoring, so then studied and developed the fixed-point multi-beam echo sounder monitoring system of real-time. The system offers underwater topographic data of real-time time serials and full coverage, and also supports the study of scouring as well as the prevention and reduction of disasters in wading constructions through those data. We also proposed a fitting formula from the data observed by the system that provides with a method for calculating the scour depth, so as to support the study of souring mechanism and the forecast of scouring process with key basic scouring data and a calculating method.
With the rapid development of economics and urban integration in coastal areas, the amounts of wading constructions such as sea-crossing bridges and natural disasters-prevention sea-walls increase faster. However, in tidal race waters, severe sectional scour induced by tidal flows often appears around marine structures and has been the main threat to those marine structures. Hence, the real-time monitoring and the study of sectional scouring of bridge piers and seawalls become the key to solve the difficulties. We analyzed the applications as well as the strengths and shortcomings of former technologies of scouring monitoring, so then studied and developed the fixed-point multi-beam echo sounder monitoring system of real-time. The system offers underwater topographic data of real-time time serials and full coverage, and also supports the study of scouring as well as the prevention and reduction of disasters in wading constructions through those data. We also proposed a fitting formula from the data observed by the system that provides with a method for calculating the scour depth, so as to support the study of souring mechanism and the forecast of scouring process with key basic scouring data and a calculating method.
, Available online ,
doi: 10.12170/20220923001
Abstract:
In order to investigate the mechanism of seepage failure of landslide dam, the development mechanism of the whole process from seepage failure to overtopping is studied from three aspects: material gradation, initial seepage channel location and dam compactness, by carrying out physical simulation of seepage failure of landslide dam. The research results show that: the expansion of the seepage channel is slow in the early stage of seepage failure, which prolongs the dam failure time to a certain extent; as the seepage channel continues to expand, the scouring effect of the infiltration flow on the soil of the seepage channel is gradually strong, resulting in cracks and intermittent collapse of the soil above the channel; the collapsed soil is easy to be scoured downstream by the flow because it is loose, and the development of the seepage channel is fast at this stage, and during this stage, the development of seepage channels is fast, mainly intermittent expansion, and in a relatively short period of time, the mode of dam failure changes from seepage failure to overtopping, the flow rate reaches a rapid peak and then gradually decreases, and there is a small increase in the flow rate caused by intermittent collapse of the slope of the breach during the process of gradual reduction of the flow rate; the location of the initial seepage channel has a significant impact on the peak flow rate of the dam breach, where the horizontal location (the middle of the dam or the shoulder) has a more obvious impact than the vertical location. The closer the initial seepage channel is to the shoulder of the dam, the slower the development of the breach and the smaller the residual breach width. The research findings can serve as a guide for creating a mathematical model for seepage failures of barrier dams. Additionally, the results can be used to select appropriate risk prevention and treatment plans for seepage failures in barrier dams.
In order to investigate the mechanism of seepage failure of landslide dam, the development mechanism of the whole process from seepage failure to overtopping is studied from three aspects: material gradation, initial seepage channel location and dam compactness, by carrying out physical simulation of seepage failure of landslide dam. The research results show that: the expansion of the seepage channel is slow in the early stage of seepage failure, which prolongs the dam failure time to a certain extent; as the seepage channel continues to expand, the scouring effect of the infiltration flow on the soil of the seepage channel is gradually strong, resulting in cracks and intermittent collapse of the soil above the channel; the collapsed soil is easy to be scoured downstream by the flow because it is loose, and the development of the seepage channel is fast at this stage, and during this stage, the development of seepage channels is fast, mainly intermittent expansion, and in a relatively short period of time, the mode of dam failure changes from seepage failure to overtopping, the flow rate reaches a rapid peak and then gradually decreases, and there is a small increase in the flow rate caused by intermittent collapse of the slope of the breach during the process of gradual reduction of the flow rate; the location of the initial seepage channel has a significant impact on the peak flow rate of the dam breach, where the horizontal location (the middle of the dam or the shoulder) has a more obvious impact than the vertical location. The closer the initial seepage channel is to the shoulder of the dam, the slower the development of the breach and the smaller the residual breach width. The research findings can serve as a guide for creating a mathematical model for seepage failures of barrier dams. Additionally, the results can be used to select appropriate risk prevention and treatment plans for seepage failures in barrier dams.
, Available online ,
doi: 10.12170/20220609001
Abstract:
In order to study the fracture performance of cement soil, the notched semi-circular bending (NSCB) specimens were used, and the mode I fracture test was carried out. The effects of crack length, cement content and curing age on the fracture toughness and fracture energy of cement-soil were studied. The results show that: (1) When the diameter of the cement-soil NSCB specimen is D=150 mm, the crack length-diameter ratio a/R=0.4 and 0.5 are reasonable; with the increase of a/R, the peak displacement and peak load will gradually decrease, and the fracture toughness shows a trend of decrease. The fracture energy has a quadratic function relationship with a/R; (2) With the increase of cement content, the peak displacement gradually decreases, and finally tends to be horizontal, while the peak load will gradually increase, and at the same time, the sample shows typical brittle failure when it fails; fracture energy and content increase as a quadratic function. Fracture toughness and dosage increase linearly; (3) With the increase of curing age, the peak load and peak displacement gradually increase; fracture energy and fracture toughness increase with curing time as quadratic function. Compared with pure clay, the fracture performance of cement-soil is significantly enhanced.
In order to study the fracture performance of cement soil, the notched semi-circular bending (NSCB) specimens were used, and the mode I fracture test was carried out. The effects of crack length, cement content and curing age on the fracture toughness and fracture energy of cement-soil were studied. The results show that: (1) When the diameter of the cement-soil NSCB specimen is D=150 mm, the crack length-diameter ratio a/R=0.4 and 0.5 are reasonable; with the increase of a/R, the peak displacement and peak load will gradually decrease, and the fracture toughness shows a trend of decrease. The fracture energy has a quadratic function relationship with a/R; (2) With the increase of cement content, the peak displacement gradually decreases, and finally tends to be horizontal, while the peak load will gradually increase, and at the same time, the sample shows typical brittle failure when it fails; fracture energy and content increase as a quadratic function. Fracture toughness and dosage increase linearly; (3) With the increase of curing age, the peak load and peak displacement gradually increase; fracture energy and fracture toughness increase with curing time as quadratic function. Compared with pure clay, the fracture performance of cement-soil is significantly enhanced.
, Available online ,
doi: 10.12170/20220601002
Abstract:
The nonlinear characteristics of the distribution and propagation of initial microcracks in reinforced concrete structures are obvious. It is of great significance to reasonably estimate the damage range and crack width in the process of concrete deterioration to reduce the economic loss of the project and ensure the safe operation of the structure. On the basis of establishing four-parameter equivalent strain and four-parameter failure criterion of strain space, the damage variable of concrete structure under complex multiaxial stress state is solved. After the relevant information of discontinuous cracking part of concrete is obtained through the strain decomposition method, the expression of crack width in the whole process of structural damage and cracking is deduced according to damage mechanics and smeared crack theory. Taking a four-point bending beam as an example, the finite element calculation is carried out. The research results show that the above method can describe the deformation characteristics and cracking rules of the reinforced concrete beam during the whole stress process from loading to failure in detail. The numerical simulation results are in good agreement with the test data, which verifies the rationality and accuracy of the calculation model. The research results can provide decision-making support for the maintenance and reinforcement of reinforced concrete structures in practical projects.
The nonlinear characteristics of the distribution and propagation of initial microcracks in reinforced concrete structures are obvious. It is of great significance to reasonably estimate the damage range and crack width in the process of concrete deterioration to reduce the economic loss of the project and ensure the safe operation of the structure. On the basis of establishing four-parameter equivalent strain and four-parameter failure criterion of strain space, the damage variable of concrete structure under complex multiaxial stress state is solved. After the relevant information of discontinuous cracking part of concrete is obtained through the strain decomposition method, the expression of crack width in the whole process of structural damage and cracking is deduced according to damage mechanics and smeared crack theory. Taking a four-point bending beam as an example, the finite element calculation is carried out. The research results show that the above method can describe the deformation characteristics and cracking rules of the reinforced concrete beam during the whole stress process from loading to failure in detail. The numerical simulation results are in good agreement with the test data, which verifies the rationality and accuracy of the calculation model. The research results can provide decision-making support for the maintenance and reinforcement of reinforced concrete structures in practical projects.
, Available online ,
doi: 10.12170/20220905003
Abstract:
In order to better reflect the trend of water resources carrying capacity and its grade, this paper applies the principle of partial relation number and subtraction set to deal with the difference items in the five-element relation number twice from the general relation point of view. The method of double partial subtraction set pair potential is constructed, which reduces the remaining amount of difference term in five-element subtraction set pair potential and avoids the artificially set coefficient 0.5 in calculation. The application of this method in Huaibei Plain shows that: from 2015 to 2019, most of the water resources carrying capacities of the six cities in the Huaibei Plain were between levels 3 and 4, and only those of Suzhou, Bengbu and Huainan cities in 2018 were between level 2 and level 3, and the water resources carrying capacity of the six cities in the Huaibei Plain did not show partial homogeneity or homogeneity during 2015-2019, indicating that the overall water resources carrying capacity of the Huaibei Plain was weak. The method of double semi-partial subtraction set pair potential broadens the thinking of analyzing and evaluating the carrying capacity of water resources.
In order to better reflect the trend of water resources carrying capacity and its grade, this paper applies the principle of partial relation number and subtraction set to deal with the difference items in the five-element relation number twice from the general relation point of view. The method of double partial subtraction set pair potential is constructed, which reduces the remaining amount of difference term in five-element subtraction set pair potential and avoids the artificially set coefficient 0.5 in calculation. The application of this method in Huaibei Plain shows that: from 2015 to 2019, most of the water resources carrying capacities of the six cities in the Huaibei Plain were between levels 3 and 4, and only those of Suzhou, Bengbu and Huainan cities in 2018 were between level 2 and level 3, and the water resources carrying capacity of the six cities in the Huaibei Plain did not show partial homogeneity or homogeneity during 2015-2019, indicating that the overall water resources carrying capacity of the Huaibei Plain was weak. The method of double semi-partial subtraction set pair potential broadens the thinking of analyzing and evaluating the carrying capacity of water resources.
, Available online ,
doi: 10.12170/20220225002
Abstract:
A nested tidal model for the East China Sea-Zhejiang coastal waters is built by use of MIKE21, to simulate the storm surge generated by typhoon “Chan-hom” based on Holland wind field model. The comparison of the numerical results and the field measurements shows that the simulated values are reasonable and reliable. Based on the verified model, two typhoons with extreme moving speeds (typhoon “Mary” and “Kai-tak” with low and high moving speeds, respectively) from 1949 to 2020 are simulated and analyzed. To investigate the influence of the moving speed, three different moving speeds (2.0, 1.0 and 0.5 times of the actual moving speed) are studied based on the typhoon case “Chan-hom”. The results show that (1) for the two typhoons with extreme moving speeds, although the landing intensity of low moving speed typhoon is lower than that of high moving speed typhoon, the former has a longer impact on the storm surge in the coastal waters of Zhejiang Province for low moving speed typhoon. The duration of 0.5 m or above water level increase is only 4 h for “Kai-tak”, while for “Mary” the duration of the same water level increase is 12 h. (2) for the three different moving speeds, when the moving speed is slower, the wind direction points to the shore for a longer time, which makes the water level in the area from the west of Zhoushan sea area to the Qiantang River increase due to the decrease of the moving speed. (3) The field data from Zhujiajian observing point shows that the maximum increase of the water level appears as the wind speed reaches the maximum value before landing. There is little difference in the water level increase under the three different moving speeds. At the Zhoushan offshore observing point, the water level changes periodically with the tide level. The water increase is larger at the low tide level, while it is smaller at the high tide level.
A nested tidal model for the East China Sea-Zhejiang coastal waters is built by use of MIKE21, to simulate the storm surge generated by typhoon “Chan-hom” based on Holland wind field model. The comparison of the numerical results and the field measurements shows that the simulated values are reasonable and reliable. Based on the verified model, two typhoons with extreme moving speeds (typhoon “Mary” and “Kai-tak” with low and high moving speeds, respectively) from 1949 to 2020 are simulated and analyzed. To investigate the influence of the moving speed, three different moving speeds (2.0, 1.0 and 0.5 times of the actual moving speed) are studied based on the typhoon case “Chan-hom”. The results show that (1) for the two typhoons with extreme moving speeds, although the landing intensity of low moving speed typhoon is lower than that of high moving speed typhoon, the former has a longer impact on the storm surge in the coastal waters of Zhejiang Province for low moving speed typhoon. The duration of 0.5 m or above water level increase is only 4 h for “Kai-tak”, while for “Mary” the duration of the same water level increase is 12 h. (2) for the three different moving speeds, when the moving speed is slower, the wind direction points to the shore for a longer time, which makes the water level in the area from the west of Zhoushan sea area to the Qiantang River increase due to the decrease of the moving speed. (3) The field data from Zhujiajian observing point shows that the maximum increase of the water level appears as the wind speed reaches the maximum value before landing. There is little difference in the water level increase under the three different moving speeds. At the Zhoushan offshore observing point, the water level changes periodically with the tide level. The water increase is larger at the low tide level, while it is smaller at the high tide level.
, Available online ,
doi: 10.12170/20221010002
Abstract:
The water and sediment movement in the Qiantang River estuary is extremely complex. The problems of the sediment transport has always been concerned by scholars. However, it is very difficult to observe the sediment concentration in the tidal reaches of the estuary, and there is a relative lack of systematic measurement analysis and research on the law of sediment concentration. In order to improve the understanding of water and sediment characteristics in the Qiantang River estuary, the measured sediment concentration at Yanguan tidal gauge station for several consecutive days from April to June 2022 was analyzed and studied based on the background of the cofferdam project to be built in Haining section on the north bank of the Qiantang River before the main flood season. Firstly, the data of sediment concentration were divided and analyzed according to the tidal range level (spring tide, middle tide, neap tide) and tidal time (before flood tide, flood tide, slack tide, ebb tide). Secondly, the measured sediment concentration was fitted with the turbidity data obtained from Yanguan tidal gauge station in the same period. Two groups of fitting curves were obtained according to the level of tidal range and turbidity interval, and the correlation degree was around 0.9. The fitted curve was verified and then applied in the analysis of relationship between the tidal level and the sediment concentration in July. The results showed that the dispersion degree of sediment concentration during spring tide was the largest, followed by middle tide and neap tide. There was little change in sediment concentration during neap tides. The sediment concentration increased obviously during middle tide and spring tide, and decreased during slack tide at high level before returning to the original sediment concentration during ebb tide. Overall, sediment concentration curve and tidal curve had similar periodic process. It was noted that the sediment concentration showed a small rise during ebb tide period, which might be because the flow velocity increased after the slack tide period and some settled sediment moved again with flow. This study will enhance the understanding of sediment transport in the Qiantang River estuary, which helps to solve the sediment problems in the estuary engineering.
The water and sediment movement in the Qiantang River estuary is extremely complex. The problems of the sediment transport has always been concerned by scholars. However, it is very difficult to observe the sediment concentration in the tidal reaches of the estuary, and there is a relative lack of systematic measurement analysis and research on the law of sediment concentration. In order to improve the understanding of water and sediment characteristics in the Qiantang River estuary, the measured sediment concentration at Yanguan tidal gauge station for several consecutive days from April to June 2022 was analyzed and studied based on the background of the cofferdam project to be built in Haining section on the north bank of the Qiantang River before the main flood season. Firstly, the data of sediment concentration were divided and analyzed according to the tidal range level (spring tide, middle tide, neap tide) and tidal time (before flood tide, flood tide, slack tide, ebb tide). Secondly, the measured sediment concentration was fitted with the turbidity data obtained from Yanguan tidal gauge station in the same period. Two groups of fitting curves were obtained according to the level of tidal range and turbidity interval, and the correlation degree was around 0.9. The fitted curve was verified and then applied in the analysis of relationship between the tidal level and the sediment concentration in July. The results showed that the dispersion degree of sediment concentration during spring tide was the largest, followed by middle tide and neap tide. There was little change in sediment concentration during neap tides. The sediment concentration increased obviously during middle tide and spring tide, and decreased during slack tide at high level before returning to the original sediment concentration during ebb tide. Overall, sediment concentration curve and tidal curve had similar periodic process. It was noted that the sediment concentration showed a small rise during ebb tide period, which might be because the flow velocity increased after the slack tide period and some settled sediment moved again with flow. This study will enhance the understanding of sediment transport in the Qiantang River estuary, which helps to solve the sediment problems in the estuary engineering.
, Available online ,
doi: 10.12170/20230215001
Abstract:
It is essential to evaluate the performance of global climate models in simulating precipitation and temperature in the water conservation region of the Yellow River Basin, which serves as a vital ecological barrier. This study employs 20 global climate models from the sixth phase of the International Coupled Model Comparison Program (CMIP6) to comprehensively assess the simulation accuracy of precipitation and temperature in the Yellow River Basin water conservation region from 1985 to 2014. Evaluation metrics such as relative error, correlation coefficient, deterministic coefficient, and Taylor diagram are utilized, and spatial analysis is conducted on the selected models. The findings reveal that the majority of climate models perform better in simulating temperature than precipitation, with temperature exhibiting a correlation coefficient above 0.95. On the other hand, precipitation tends to be overestimated, and the deterministic coefficient is low. Within the Yellow River Basin water conservation region, the accuracy of most models in all three subareas—the Yellow River source area, the Tangnaihai-Lanzhou basin, and the Weihe-Yiluo River basin—requires further improvement. Additionally, different climate models exhibit varying simulation abilities across different subareas. Generally, the 20 models exhibit the most accurate simulation of precipitation and temperature in the Yellow River source area, followed by the Tangnaihai-Lanzhou basin, and the least accurate in the Weihe-Yiluo River basin. Notably, the EC-Earth3-Veg model demonstrates relatively superior simulation capabilities in all three regions and can effectively reproduce the annual variation characteristics of precipitation and temperature. Spatial distribution of the simulated values and multi-year average observed values exhibit some variability. Precipitation deviates most significantly in the Yellow River source area, followed by the Tangnaihai-Lanzhou basin, while the Weihe-Yiluo River basin shows the best agreement. Regarding temperature deviation, the Tangnaihai-Lanzhou basin exhibits the highest deviation, followed by the Weihe-Yiluo River basin, while the Yellow River source area shows the best agreement. The outcomes of this study can provide valuable insights for water resources management and climate change research in the Yellow River Basin.
It is essential to evaluate the performance of global climate models in simulating precipitation and temperature in the water conservation region of the Yellow River Basin, which serves as a vital ecological barrier. This study employs 20 global climate models from the sixth phase of the International Coupled Model Comparison Program (CMIP6) to comprehensively assess the simulation accuracy of precipitation and temperature in the Yellow River Basin water conservation region from 1985 to 2014. Evaluation metrics such as relative error, correlation coefficient, deterministic coefficient, and Taylor diagram are utilized, and spatial analysis is conducted on the selected models. The findings reveal that the majority of climate models perform better in simulating temperature than precipitation, with temperature exhibiting a correlation coefficient above 0.95. On the other hand, precipitation tends to be overestimated, and the deterministic coefficient is low. Within the Yellow River Basin water conservation region, the accuracy of most models in all three subareas—the Yellow River source area, the Tangnaihai-Lanzhou basin, and the Weihe-Yiluo River basin—requires further improvement. Additionally, different climate models exhibit varying simulation abilities across different subareas. Generally, the 20 models exhibit the most accurate simulation of precipitation and temperature in the Yellow River source area, followed by the Tangnaihai-Lanzhou basin, and the least accurate in the Weihe-Yiluo River basin. Notably, the EC-Earth3-Veg model demonstrates relatively superior simulation capabilities in all three regions and can effectively reproduce the annual variation characteristics of precipitation and temperature. Spatial distribution of the simulated values and multi-year average observed values exhibit some variability. Precipitation deviates most significantly in the Yellow River source area, followed by the Tangnaihai-Lanzhou basin, while the Weihe-Yiluo River basin shows the best agreement. Regarding temperature deviation, the Tangnaihai-Lanzhou basin exhibits the highest deviation, followed by the Weihe-Yiluo River basin, while the Yellow River source area shows the best agreement. The outcomes of this study can provide valuable insights for water resources management and climate change research in the Yellow River Basin.
, Available online ,
doi: 10.12170/20221011004
Abstract:
This paper introduces a new heuristic intelligent optimization algorithm called the ripple algorithm (RA), inspired by the ripple phenomenon in nature. The algorithm mimics the structure of ripples and utilizes a three-layer ripple random point search starting from the central point. The search center group is determined based on the comparative information between the current fitness and the global optimal fitness. The expansion and contraction of ripples are controlled by the ripple radius function and contraction function, respectively, allowing the algorithm to converge towards the best point in the solution space independently. Through comparisons with other commonly used heuristic algorithms such as particle swarm optimization algorithm, standard genetic algorithm, and gravity search algorithm using test functions, the results demonstrate that the ripple algorithm exhibits strong competitiveness in lower dimensions. Moreover, when applied to parameter optimization of the Muskingum model, the ripple algorithm demonstrates excellent optimization ability, high accuracy, and practicality. The paper also discusses the ripple radius function, contraction function, and other parameters that impact the optimization process of the ripple algorithm, and proposes several ideas and directions for further improving the algorithm.
This paper introduces a new heuristic intelligent optimization algorithm called the ripple algorithm (RA), inspired by the ripple phenomenon in nature. The algorithm mimics the structure of ripples and utilizes a three-layer ripple random point search starting from the central point. The search center group is determined based on the comparative information between the current fitness and the global optimal fitness. The expansion and contraction of ripples are controlled by the ripple radius function and contraction function, respectively, allowing the algorithm to converge towards the best point in the solution space independently. Through comparisons with other commonly used heuristic algorithms such as particle swarm optimization algorithm, standard genetic algorithm, and gravity search algorithm using test functions, the results demonstrate that the ripple algorithm exhibits strong competitiveness in lower dimensions. Moreover, when applied to parameter optimization of the Muskingum model, the ripple algorithm demonstrates excellent optimization ability, high accuracy, and practicality. The paper also discusses the ripple radius function, contraction function, and other parameters that impact the optimization process of the ripple algorithm, and proposes several ideas and directions for further improving the algorithm.
, Available online ,
doi: 10.12170/20230323002
Abstract:
Emergency drills for reservoir dams are essential for familiarizing personnel with emergency plans, improving response capabilities, and enhancing overall emergency management. However, current emergency drills primarily focus on the engineering aspects of emergency response, neglecting crucial components such as flood forecasting, incident reporting, information flow, decision-making, on-site operations, and evacuation procedures. Moreover, the evaluation methods for drill effectiveness are lacking. Therefore, there is a need to explore new technologies for emergency drills. This paper systematically reviews the research and practices of emergency drill technology for reservoir dams, both domestically and internationally. It proposes a technical framework considering the discrete nature of emergency response and disposal, based on an analysis of reservoir emergency characteristics. The proposed framework analyzes the emergency response and disposal mechanisms based on factors such as roles, types of disasters, response levels, early warning time, and disposal methods. It establishes an emergency drill framework system with time as the main axis, roles as the central focus, and event development as the driving force. Additionally, the paper constructs an evaluation method and technical standards for emergency drills, aiming to establish a standardized model for conducting and evaluating emergency drills. Leveraging BPMN technology and visualization techniques, an information platform is developed to simulate key aspects of emergency management and provide comprehensive quantitative evaluation results for roles and emergency drills. The ultimate goal is to achieve effective emergency drills and enhance preparedness.
Emergency drills for reservoir dams are essential for familiarizing personnel with emergency plans, improving response capabilities, and enhancing overall emergency management. However, current emergency drills primarily focus on the engineering aspects of emergency response, neglecting crucial components such as flood forecasting, incident reporting, information flow, decision-making, on-site operations, and evacuation procedures. Moreover, the evaluation methods for drill effectiveness are lacking. Therefore, there is a need to explore new technologies for emergency drills. This paper systematically reviews the research and practices of emergency drill technology for reservoir dams, both domestically and internationally. It proposes a technical framework considering the discrete nature of emergency response and disposal, based on an analysis of reservoir emergency characteristics. The proposed framework analyzes the emergency response and disposal mechanisms based on factors such as roles, types of disasters, response levels, early warning time, and disposal methods. It establishes an emergency drill framework system with time as the main axis, roles as the central focus, and event development as the driving force. Additionally, the paper constructs an evaluation method and technical standards for emergency drills, aiming to establish a standardized model for conducting and evaluating emergency drills. Leveraging BPMN technology and visualization techniques, an information platform is developed to simulate key aspects of emergency management and provide comprehensive quantitative evaluation results for roles and emergency drills. The ultimate goal is to achieve effective emergency drills and enhance preparedness.
Temporal variation of hydrological regime and water quality status between 2014-2020 in Gucheng Lake
, Available online ,
doi: 10.12170/20220929004
Abstract:
As an essential Yangtze river-connected lake regulated by the sluice and pump station, Gucheng Lake played a vital role in water resources regulation, drinking water supply, irrigation, aquaculture, and ecosystem balance maintenance. Temporal variation of hydrology regime and water quality between 2014 and 2020 in Gucheng Lake were investigated, and the effects of hydrological regime on water quality were also explored. Results show that: (1) The hydrological regime of Gucheng Lake was affected by inflow from Shuiyang River, local precipitation, sluice regulation and artificial replenishment. Compared with multi-years mean water stage, water stage in winter and spring increased by about 2 m. The period of annual lowest water stage was postponed from winter and spring to early summer. Natural hydrological regime was changed. (2) Multi-annual mean of TN, TP, NH3-N and CODMn concentrations were 0.90 mg/L, 0.04 mg/L, 0.16 mg/L and 4.00 mg/L respectively. Concentrations of Chlorophyll a fluctuated around 0.01 mg/L. Seasonal Kendall trend test showed that nitrogen and phosphorus nutrients and CODMn witnessed a remarkable decreasing trend, while Chlorophyll a and nutrient index increased. Nutrient index shifted from mesotrophic status to eutrophication. (3) The water inflow of Gucheng Lake was significantly negatively correlated with transparency, and significantly positively correlated with TP, chlorophyll a and nutritional index. Monthly average water level was significantly positively correlated with CODMn, NH3-N and TP. Hydrological regime was the main driving force for the variation of water quality in Gucheng Lake. The capacity of water resources control and regulation was suggested to enhance further to meet water use for daily life, production and ecology during the nonrainy season and extremely drought condition. Strengthening watershed water pollution control and prevention was suggested to improve water quality in the rivers entering Gucheng Lake.
As an essential Yangtze river-connected lake regulated by the sluice and pump station, Gucheng Lake played a vital role in water resources regulation, drinking water supply, irrigation, aquaculture, and ecosystem balance maintenance. Temporal variation of hydrology regime and water quality between 2014 and 2020 in Gucheng Lake were investigated, and the effects of hydrological regime on water quality were also explored. Results show that: (1) The hydrological regime of Gucheng Lake was affected by inflow from Shuiyang River, local precipitation, sluice regulation and artificial replenishment. Compared with multi-years mean water stage, water stage in winter and spring increased by about 2 m. The period of annual lowest water stage was postponed from winter and spring to early summer. Natural hydrological regime was changed. (2) Multi-annual mean of TN, TP, NH3-N and CODMn concentrations were 0.90 mg/L, 0.04 mg/L, 0.16 mg/L and 4.00 mg/L respectively. Concentrations of Chlorophyll a fluctuated around 0.01 mg/L. Seasonal Kendall trend test showed that nitrogen and phosphorus nutrients and CODMn witnessed a remarkable decreasing trend, while Chlorophyll a and nutrient index increased. Nutrient index shifted from mesotrophic status to eutrophication. (3) The water inflow of Gucheng Lake was significantly negatively correlated with transparency, and significantly positively correlated with TP, chlorophyll a and nutritional index. Monthly average water level was significantly positively correlated with CODMn, NH3-N and TP. Hydrological regime was the main driving force for the variation of water quality in Gucheng Lake. The capacity of water resources control and regulation was suggested to enhance further to meet water use for daily life, production and ecology during the nonrainy season and extremely drought condition. Strengthening watershed water pollution control and prevention was suggested to improve water quality in the rivers entering Gucheng Lake.
, Available online ,
doi: 10.12170/20211218001
Abstract:
Through single pile static load field tests and finite element analysis, the distribution law of pile side friction in vertically layered foundation was studied. It was found that there is a sudden change in side friction at the soil interface. The pile side friction near the soil interface is about 2-6 times that of a single soil layer, and the sudden change range is 1-2 meters on both sides of the interface. The accumulation of lateral friction stress is mainly on the "hard" soil layer side, and the elastic modulus of the soil on both sides of the soil interface has a certain impact on the accumulation of lateral friction stress. As the difference in elastic modulus of the soil on both sides increases, this influence gradually decreases.
Through single pile static load field tests and finite element analysis, the distribution law of pile side friction in vertically layered foundation was studied. It was found that there is a sudden change in side friction at the soil interface. The pile side friction near the soil interface is about 2-6 times that of a single soil layer, and the sudden change range is 1-2 meters on both sides of the interface. The accumulation of lateral friction stress is mainly on the "hard" soil layer side, and the elastic modulus of the soil on both sides of the soil interface has a certain impact on the accumulation of lateral friction stress. As the difference in elastic modulus of the soil on both sides increases, this influence gradually decreases.
, Available online ,
doi: 10.12170/20220625002
Abstract:
Accurately determining the unit friction in pile driving is very important for improving the accuracy of pile driveability analysis. Based on the in-situ cone penetration test data and high strain dynamic test results of an interlayered soil site, the change of unit friction during pile driving is studied. The results show that during the pile driving, although the total friction of pile keeps increasing with increment of penetration depth, and the total friction at the same penetration depth decreases, which is the same as that in ordinary site, the interlayered soil has a significant effect on the change of unit friction with depth. The results of analysis shows that the unit friction also decreases significantly in sand layer and silt layer in the interlayered site, which could not be described correctly with the existing semi theoretical method. In view of this, a calculation method of reduction factor in clay based on sensitivity is proposed. At the same time, it is pointed out that the same reduction factor as that of clay should be used for sandy layer and silt layer for the interlayered soil. The unit friction obtained by the proposed method is basically consistent with the measured value. The proposed method could be used in practice to improve accuracy of pile driveability analysis in an interbedded soil site.
Accurately determining the unit friction in pile driving is very important for improving the accuracy of pile driveability analysis. Based on the in-situ cone penetration test data and high strain dynamic test results of an interlayered soil site, the change of unit friction during pile driving is studied. The results show that during the pile driving, although the total friction of pile keeps increasing with increment of penetration depth, and the total friction at the same penetration depth decreases, which is the same as that in ordinary site, the interlayered soil has a significant effect on the change of unit friction with depth. The results of analysis shows that the unit friction also decreases significantly in sand layer and silt layer in the interlayered site, which could not be described correctly with the existing semi theoretical method. In view of this, a calculation method of reduction factor in clay based on sensitivity is proposed. At the same time, it is pointed out that the same reduction factor as that of clay should be used for sandy layer and silt layer for the interlayered soil. The unit friction obtained by the proposed method is basically consistent with the measured value. The proposed method could be used in practice to improve accuracy of pile driveability analysis in an interbedded soil site.
, Available online ,
doi: 10.12170/20230202001
Abstract:
Dam safety evaluation systems for reservoirs and hydropower stations currently differ in their approaches. To identify shortcomings in the dam safety appraisal of reservoirs and learn from the experience of periodic dam safety inspection at hydropower stations, a comparative analysis of the dam safety evaluation systems for reservoirs and hydropower stations was conducted. The analysis focused on two main aspects: organizational systems and technical systems. The organizational systems for dam safety evaluation in reservoirs and hydropower stations exhibit significant differences, but they align with the actual situation and the respective characteristics of dams in the water conservancy and energy sectors. The technical systems of both systems are based on site inspections and analysis of monitoring data. Safety evaluations are conducted separately for different types of hidden dangers and project sections. To improve the safety appraisal of reservoir dams, it is recommended to revise the "Measures for Safety Appraisal of Reservoir Dams", standardize dam safety monitoring practices, and enhance technical specifications for dam safety evaluation.
Dam safety evaluation systems for reservoirs and hydropower stations currently differ in their approaches. To identify shortcomings in the dam safety appraisal of reservoirs and learn from the experience of periodic dam safety inspection at hydropower stations, a comparative analysis of the dam safety evaluation systems for reservoirs and hydropower stations was conducted. The analysis focused on two main aspects: organizational systems and technical systems. The organizational systems for dam safety evaluation in reservoirs and hydropower stations exhibit significant differences, but they align with the actual situation and the respective characteristics of dams in the water conservancy and energy sectors. The technical systems of both systems are based on site inspections and analysis of monitoring data. Safety evaluations are conducted separately for different types of hidden dangers and project sections. To improve the safety appraisal of reservoir dams, it is recommended to revise the "Measures for Safety Appraisal of Reservoir Dams", standardize dam safety monitoring practices, and enhance technical specifications for dam safety evaluation.
, Available online ,
doi: 10.12170/20220825001
Abstract:
Three-dimensional refinement modeling is carried out for the dam body, dam foundation, face plate and impervious curtain of Daigusi concrete face rockfill dam (CFRD). Self-developed three-dimensional seepage calculation and analysis software DUT-SEEPAGE is used to calculate the seepage situation, emphasizing on the study of the characteristics of seepage field distribution and the anti-seepage effect by the joint action of face plate and impervious curtain, and the variation of dam leakage with permeability coefficient of dam base. Finally, the effect of the permeability coefficient on the infiltration line of the dam when there is a fracture zone in the dam foundation is analyzed. The results suggest that the anti-seepage effectively blocks the infiltration of the upstream water flow and plays a very good impermeable effect, which can ensure the safe operation of the dam. The change of permeability coefficient of the extrusion fracture zone has little influence on the position of the dam infiltration line, but the distribution of pore water pressure and total head changes greatly. Moreover, when the permeability coefficient of the fracture zone is large, the hydraulic gradient will also increase, resulting in the potential risk of seepage damage around the fracture zone.
Three-dimensional refinement modeling is carried out for the dam body, dam foundation, face plate and impervious curtain of Daigusi concrete face rockfill dam (CFRD). Self-developed three-dimensional seepage calculation and analysis software DUT-SEEPAGE is used to calculate the seepage situation, emphasizing on the study of the characteristics of seepage field distribution and the anti-seepage effect by the joint action of face plate and impervious curtain, and the variation of dam leakage with permeability coefficient of dam base. Finally, the effect of the permeability coefficient on the infiltration line of the dam when there is a fracture zone in the dam foundation is analyzed. The results suggest that the anti-seepage effectively blocks the infiltration of the upstream water flow and plays a very good impermeable effect, which can ensure the safe operation of the dam. The change of permeability coefficient of the extrusion fracture zone has little influence on the position of the dam infiltration line, but the distribution of pore water pressure and total head changes greatly. Moreover, when the permeability coefficient of the fracture zone is large, the hydraulic gradient will also increase, resulting in the potential risk of seepage damage around the fracture zone.
, Available online ,
doi: 10.12170/20220813005
Abstract:
With the development of Chinese economy, the demand for natural resources in coastal cities is growing day by day, and it is of great significance to use superlong pipeline to transport natural resources across the sea to support economic development and construction of coastal cities. However, the design and laying of super long cross-sea pipeline mainly rely on experience and engineering analogy method. In order to provide sufficient scientific basis and measured data support for the floating process of offshore ultra-long pipeline, this paper carried out a fluid-structure coupling numerical simulation study on the floating process of offshore ultra-long pipeline based on the pipeline floating construction project in Tongan Bay, Xiamen, to obtain the deformation characteristics of the pipeline floating and apply them. The results show that the strain and displacement of floating pipelines are directly proportional to the slenderness ratio of pipelines and the relative velocity, and inversely proportional to the number of tugboats and the bending angle of pipelines. The maximum displacement of tugboat decreases by about half with each additional tugboat. Changing the number of tugboats or the towing force can effectively control the deformation of the pipeline. The calculation and analysis of the resistance and deformation of pipeline floating transportation is conducive to the reasonable arrangement of tugboats and the safety of pipeline floating transportation. When the wave and current are combined, the pipeline deformation is large and the floating transportation should be carried out when the sea wave is small.
With the development of Chinese economy, the demand for natural resources in coastal cities is growing day by day, and it is of great significance to use superlong pipeline to transport natural resources across the sea to support economic development and construction of coastal cities. However, the design and laying of super long cross-sea pipeline mainly rely on experience and engineering analogy method. In order to provide sufficient scientific basis and measured data support for the floating process of offshore ultra-long pipeline, this paper carried out a fluid-structure coupling numerical simulation study on the floating process of offshore ultra-long pipeline based on the pipeline floating construction project in Tongan Bay, Xiamen, to obtain the deformation characteristics of the pipeline floating and apply them. The results show that the strain and displacement of floating pipelines are directly proportional to the slenderness ratio of pipelines and the relative velocity, and inversely proportional to the number of tugboats and the bending angle of pipelines. The maximum displacement of tugboat decreases by about half with each additional tugboat. Changing the number of tugboats or the towing force can effectively control the deformation of the pipeline. The calculation and analysis of the resistance and deformation of pipeline floating transportation is conducive to the reasonable arrangement of tugboats and the safety of pipeline floating transportation. When the wave and current are combined, the pipeline deformation is large and the floating transportation should be carried out when the sea wave is small.
, Available online ,
doi: 10.12170/20221013002
Abstract:
According to the settling velocity characteristics of cohesive sediment composed of cohesive minerals in the Yellow River Basin, the physical graph of energy dissipation at the water sediment interface of sediment particles is constructed with the force analysis and energy conservation of sediment particles. The explicit expression of sediment group settling velocity is established with the kinematic viscosity coefficient and turbulent viscosity coefficient of sediment laden flow, which could show the influence of flow viscosity and wake separation on sediment particle settling resistance reasonably. The settling velocity tests of typical cohesive sediment (red arsenic sandstone particles) in the Yellow River are carried out. The results show that the group settling velocity of red arsenic sandstone in the sediment laden flow decreases monotonously with the sediment concentration and tends to a constant value. For the vertical averaged sediment concentration 0.34~0.45 kg/m3, the group settling velocity monotonously increases with the sediment concentration. The theoretical analysis is carried out around the experimental phenomena, and the established formula is verified by the experimental data. This study can provide important references for the deposition and transport of cohesive suspended sediments in the Yellow River Basin.
According to the settling velocity characteristics of cohesive sediment composed of cohesive minerals in the Yellow River Basin, the physical graph of energy dissipation at the water sediment interface of sediment particles is constructed with the force analysis and energy conservation of sediment particles. The explicit expression of sediment group settling velocity is established with the kinematic viscosity coefficient and turbulent viscosity coefficient of sediment laden flow, which could show the influence of flow viscosity and wake separation on sediment particle settling resistance reasonably. The settling velocity tests of typical cohesive sediment (red arsenic sandstone particles) in the Yellow River are carried out. The results show that the group settling velocity of red arsenic sandstone in the sediment laden flow decreases monotonously with the sediment concentration and tends to a constant value. For the vertical averaged sediment concentration 0.34~0.45 kg/m3, the group settling velocity monotonously increases with the sediment concentration. The theoretical analysis is carried out around the experimental phenomena, and the established formula is verified by the experimental data. This study can provide important references for the deposition and transport of cohesive suspended sediments in the Yellow River Basin.
, Available online ,
doi: 10.12170/20230223005
Abstract:
The confluence of rivers plays a pivotal role in managing river basin systems. This study focuses on the hydrodynamic characteristics of the Huangshui River and Yellow River confluence in Northwest China, utilizing a 2D hydrodynamic mathematical model of turbulent flow. The findings reveal a distinct high-velocity region at the confluence, the location and size of which are influenced by the flow ratio. Despite various hydrological scenarios, no significant water flow separation zones form at the confluence. The presence of a main stream causes a flowback area on the left and right banks of the tributary inlet, adopting a wing-shaped distribution along the flow direction. The shape of this area varies with the flow ratio. Turbulent energy concentrates in the shear layer and downstream right bank of the confluence. As the flow ratio increases, turbulent energy diminishes in the shear layer but increases in the downstream right bank. These findings offer a theoretical foundation for river management, water environmental protection, and flood control at river confluences and downstream areas.
The confluence of rivers plays a pivotal role in managing river basin systems. This study focuses on the hydrodynamic characteristics of the Huangshui River and Yellow River confluence in Northwest China, utilizing a 2D hydrodynamic mathematical model of turbulent flow. The findings reveal a distinct high-velocity region at the confluence, the location and size of which are influenced by the flow ratio. Despite various hydrological scenarios, no significant water flow separation zones form at the confluence. The presence of a main stream causes a flowback area on the left and right banks of the tributary inlet, adopting a wing-shaped distribution along the flow direction. The shape of this area varies with the flow ratio. Turbulent energy concentrates in the shear layer and downstream right bank of the confluence. As the flow ratio increases, turbulent energy diminishes in the shear layer but increases in the downstream right bank. These findings offer a theoretical foundation for river management, water environmental protection, and flood control at river confluences and downstream areas.
, Available online ,
doi: 10.12170/20230418001
Abstract:
The current machine learning-based safety monitoring models for hydraulic structures lack interpretability in their results. To address this issue, we propose a prediction and interpretation method for dependent variables based on ensemble learning algorithms. We provide a brief description of an improved statistical model and two commonly used ensemble learning algorithms, namely random forest (RF) and extreme gradient boosting tree (XGBoost). Additionally, we introduce the Shapley additive explanation method (SHAP) to achieve interpretability in the results of ensemble learning algorithm models. We explain the principles and derivation process of the SHAP method. To verify the effectiveness and practicality of our approach, we utilize deformation data from a super high arch dam during its initial operation period as an example. The results demonstrate that the XGBoost model exhibits high prediction accuracy, with a decision coefficient greater than 0.982 in the prediction set. It is followed by the improved statistical model, while the RF model shows relatively poorer accuracy. The SHAP method effectively isolates the influence of different independent variables on the dependent variable, providing an impact mechanism and enhancing the interpretability of the fitting and prediction results. Our proposed method combines the strengths of both “mechanism driven” and “data driven” approaches, offering valuable insights for the operation and management of major hydraulic structures.
The current machine learning-based safety monitoring models for hydraulic structures lack interpretability in their results. To address this issue, we propose a prediction and interpretation method for dependent variables based on ensemble learning algorithms. We provide a brief description of an improved statistical model and two commonly used ensemble learning algorithms, namely random forest (RF) and extreme gradient boosting tree (XGBoost). Additionally, we introduce the Shapley additive explanation method (SHAP) to achieve interpretability in the results of ensemble learning algorithm models. We explain the principles and derivation process of the SHAP method. To verify the effectiveness and practicality of our approach, we utilize deformation data from a super high arch dam during its initial operation period as an example. The results demonstrate that the XGBoost model exhibits high prediction accuracy, with a decision coefficient greater than 0.982 in the prediction set. It is followed by the improved statistical model, while the RF model shows relatively poorer accuracy. The SHAP method effectively isolates the influence of different independent variables on the dependent variable, providing an impact mechanism and enhancing the interpretability of the fitting and prediction results. Our proposed method combines the strengths of both “mechanism driven” and “data driven” approaches, offering valuable insights for the operation and management of major hydraulic structures.
, Available online ,
doi: 10.12170/20221231002
Abstract:
The construction of a three-level navigation lock at Longtoushan Junction was completed in April 2019. However, it has been found that the design standard was not met, posing a significant safety risk. This study aims to address this issue by analyzing data and conducting physical model tests to understand the navigation flow conditions and identify the underlying reasons. A novel measure was implemented, resulting in a substantial enhancement of the safe discharge. The optimized scheme not only helps meet the design requirements but also provides valuable technical support for engineering design and operation. Furthermore, the newly implemented measures have the potential to be widely adopted and applied in similar scenarios.
The construction of a three-level navigation lock at Longtoushan Junction was completed in April 2019. However, it has been found that the design standard was not met, posing a significant safety risk. This study aims to address this issue by analyzing data and conducting physical model tests to understand the navigation flow conditions and identify the underlying reasons. A novel measure was implemented, resulting in a substantial enhancement of the safe discharge. The optimized scheme not only helps meet the design requirements but also provides valuable technical support for engineering design and operation. Furthermore, the newly implemented measures have the potential to be widely adopted and applied in similar scenarios.
, Available online ,
doi: 10.12170/20220809002
Abstract:
Accurate prediction of water level in waterway is of great significance for ensuring ships’ navigational safety. The lower Jingjiang waterway under the Yangtze River was took as the research area, the hydrological data from 2019 to 2020 and from 2021 were adopted as the train set and test set, respectively. A temporal convolution network (TCN) model was developed for water level prediction of Lower Jingjiang waterway. Then long short-term memory network (LSTM) and support vector machine (SVM) were constructed for accuracy comparing with TCN. The results showed that there are differences of optimal input time windows of TCN in different stations. Jianli station, Tiaoxiankou station and Shishou station’s optimal input time windows were 2 days, 2 days and 3 days, respectively. In 2021, the Nash-Sutcliffe efficiency coefficient and determination coefficient of the water level prediction of TCN at each station in lower Jingjiang River were higher than 0.995, and the RMSE was basically below 0.21 m. The overall performance of TCN was better than LSTM, both of them can accurately predict the water level process and perform better than SVM. However, with the increase of prediction time scale, the prediction accuracy of water level showed a downward trend. In terms of different period, the absolute error of TCN water level prediction in dry season was basically below 0.2 m, indicating that TCN has a great potential in the field of water level prediction. By analyzing the applicability and superiority of the TCN model, this study can provide technical support for improving the accuracy of water level prediction in the Yangtze River channel and the safe navigation of ships.
Accurate prediction of water level in waterway is of great significance for ensuring ships’ navigational safety. The lower Jingjiang waterway under the Yangtze River was took as the research area, the hydrological data from 2019 to 2020 and from 2021 were adopted as the train set and test set, respectively. A temporal convolution network (TCN) model was developed for water level prediction of Lower Jingjiang waterway. Then long short-term memory network (LSTM) and support vector machine (SVM) were constructed for accuracy comparing with TCN. The results showed that there are differences of optimal input time windows of TCN in different stations. Jianli station, Tiaoxiankou station and Shishou station’s optimal input time windows were 2 days, 2 days and 3 days, respectively. In 2021, the Nash-Sutcliffe efficiency coefficient and determination coefficient of the water level prediction of TCN at each station in lower Jingjiang River were higher than 0.995, and the RMSE was basically below 0.21 m. The overall performance of TCN was better than LSTM, both of them can accurately predict the water level process and perform better than SVM. However, with the increase of prediction time scale, the prediction accuracy of water level showed a downward trend. In terms of different period, the absolute error of TCN water level prediction in dry season was basically below 0.2 m, indicating that TCN has a great potential in the field of water level prediction. By analyzing the applicability and superiority of the TCN model, this study can provide technical support for improving the accuracy of water level prediction in the Yangtze River channel and the safe navigation of ships.
, Available online ,
doi: 10.12170/20220813003
Abstract:
Effective control of deformation is an important guarantee for the urban levee road combination works to play the dual role of flood control and transportation. Based on the typical section of the levee road combination project along the Yangtze River in Nanjing, a plane strain finite element numerical model is established, and the deformation distribution and development laws of four conditions, namely, natural surcharge, step-reinforcement, deep cement mixing (DCM) and pervious concrete pile (PCP), are analyzed in depth. The research results show that the overall deformation law of the step-reinforcement condition is basically consistent with the natural surcharge condition, and the settlement and horizontal displacement of the new and old levees and foundation can not be effectively reduced without soft foundation treatment. Both DCM and PCP conditions can effectively control the settlement, uplift and horizontal displacement of the upper embankment and the lower foundation, and the post construction settlement is less than 100 mm. The PCP composite foundation can reduce the post construction settlement of the pavement to 43 mm under the condition of low replacement rate of 3.6%, and shorten the time to reach 99% consolidation degree from 1 year to 155 d, the deformation control ability of PCP condition is better than that under DCM condition. PCP composite foundation technology has a good application prospect in levee road combination project in soft foundation area with high deformation control standard and short construction period.
Effective control of deformation is an important guarantee for the urban levee road combination works to play the dual role of flood control and transportation. Based on the typical section of the levee road combination project along the Yangtze River in Nanjing, a plane strain finite element numerical model is established, and the deformation distribution and development laws of four conditions, namely, natural surcharge, step-reinforcement, deep cement mixing (DCM) and pervious concrete pile (PCP), are analyzed in depth. The research results show that the overall deformation law of the step-reinforcement condition is basically consistent with the natural surcharge condition, and the settlement and horizontal displacement of the new and old levees and foundation can not be effectively reduced without soft foundation treatment. Both DCM and PCP conditions can effectively control the settlement, uplift and horizontal displacement of the upper embankment and the lower foundation, and the post construction settlement is less than 100 mm. The PCP composite foundation can reduce the post construction settlement of the pavement to 43 mm under the condition of low replacement rate of 3.6%, and shorten the time to reach 99% consolidation degree from 1 year to 155 d, the deformation control ability of PCP condition is better than that under DCM condition. PCP composite foundation technology has a good application prospect in levee road combination project in soft foundation area with high deformation control standard and short construction period.
, Available online ,
doi: 10.12170/20230413001
Abstract:
Quantitative assessment of drought risk is of great significance for economic and social prevention and control management. In response to the problem of the wide peak distribution characteristics of the difference coefficient value and its dynamic characteristics as it changes with the evaluation sample value, based on the micro level migration of the connection components in the semi partial subtraction set pair potential, the trapezoidal fuzzy number dynamic value is used to characterize the uncertainty and continuous change process of the difference coefficient. The trapezoidal fuzzy number is simulated using random simulation method to quantitatively describe the evaluation results in the form of confidence intervals, a drought risk assessment model based on subtractive set pairwise potential trapezoidal fuzzy number random simulation is constructed, and an empirical study on dynamic drought risk assessment is conducted in Suzhou City, comparing and analyzing with existing methods. The results show that the negative development trend of drought risk in Suzhou City increased in intensity from 2007 to 2010, and decreased in intensity from 2011 to 2017. The risk level remained above level 2 for a long time and was in a state of partial drought. 2010 was the most dangerous year; the overall fluctuation range is relatively small and there is a trend towards positive development. It is identified that the risk subsystem and drought resistance subsystem are the main reasons for the drought risk in Suzhou City. This method has strong explanatory principles, reasonable and accurate results, and the evaluation results are expressed in the form of confidence intervals, providing a new and effective approach for dynamic analysis and quantitative assessment of drought risk.
Quantitative assessment of drought risk is of great significance for economic and social prevention and control management. In response to the problem of the wide peak distribution characteristics of the difference coefficient value and its dynamic characteristics as it changes with the evaluation sample value, based on the micro level migration of the connection components in the semi partial subtraction set pair potential, the trapezoidal fuzzy number dynamic value is used to characterize the uncertainty and continuous change process of the difference coefficient. The trapezoidal fuzzy number is simulated using random simulation method to quantitatively describe the evaluation results in the form of confidence intervals, a drought risk assessment model based on subtractive set pairwise potential trapezoidal fuzzy number random simulation is constructed, and an empirical study on dynamic drought risk assessment is conducted in Suzhou City, comparing and analyzing with existing methods. The results show that the negative development trend of drought risk in Suzhou City increased in intensity from 2007 to 2010, and decreased in intensity from 2011 to 2017. The risk level remained above level 2 for a long time and was in a state of partial drought. 2010 was the most dangerous year; the overall fluctuation range is relatively small and there is a trend towards positive development. It is identified that the risk subsystem and drought resistance subsystem are the main reasons for the drought risk in Suzhou City. This method has strong explanatory principles, reasonable and accurate results, and the evaluation results are expressed in the form of confidence intervals, providing a new and effective approach for dynamic analysis and quantitative assessment of drought risk.
, Available online ,
doi: 10.12170/20221229002
Abstract:
To investigate the patterns of snow change in the Third Pole region, this study examines the temporal and spatial characteristics of snow depth on the Qinghai-Tibet Plateau over the past 40 years. Additionally, it conducts a partial correlation analysis to assess the relationship between snow depth and near-surface temperature, as well as average precipitation. The analysis utilizes long-term datasets of daily snow depth in China (1979—2021) and the China meteorological forcing dataset (1979—2018). The results of the spatiotemporal variation analysis reveal a decreasing trend in snow depth across the Qinghai-Tibet Plateau, particularly in its three interior regions. This trend is more pronounced on a monthly scale, particularly during autumn and winter. However, the eastern part of the plateau experiences a significant increase in snow depth. The partial correlation analysis demonstrates a strong negative correlation between snow depth and temperature across all scales, with a maximum negative partial correlation coefficient of approximately −0.8. On the other hand, snow depth and precipitation exhibit similar spatial distribution but have distinct correlation patterns on an annual and monthly basis. Overall, the correlation between snow depth and precipitation follows a “positive in east and negative in west” distribution pattern during spring and summer, while autumn exhibits a more widespread positive correlation, with most areas showing a positive correlation above 0.4. On a daily scale, temperature exhibits the strongest negative partial correlation (−0.733) with snow depth, with a 10-day delay, while precipitation demonstrates the highest positive correlation (0.064) with snow depth, with a 3-day delay. The variation characteristics of snow depth and its correlation with meteorological factors on the Qinghai-Tibet Plateau exhibit significant spatiotemporal heterogeneity. This heterogeneity can be attributed to factors such as topography, ablation and accumulation time, and the influence of monsoons and westerlies around the plateau.
To investigate the patterns of snow change in the Third Pole region, this study examines the temporal and spatial characteristics of snow depth on the Qinghai-Tibet Plateau over the past 40 years. Additionally, it conducts a partial correlation analysis to assess the relationship between snow depth and near-surface temperature, as well as average precipitation. The analysis utilizes long-term datasets of daily snow depth in China (1979—2021) and the China meteorological forcing dataset (1979—2018). The results of the spatiotemporal variation analysis reveal a decreasing trend in snow depth across the Qinghai-Tibet Plateau, particularly in its three interior regions. This trend is more pronounced on a monthly scale, particularly during autumn and winter. However, the eastern part of the plateau experiences a significant increase in snow depth. The partial correlation analysis demonstrates a strong negative correlation between snow depth and temperature across all scales, with a maximum negative partial correlation coefficient of approximately −0.8. On the other hand, snow depth and precipitation exhibit similar spatial distribution but have distinct correlation patterns on an annual and monthly basis. Overall, the correlation between snow depth and precipitation follows a “positive in east and negative in west” distribution pattern during spring and summer, while autumn exhibits a more widespread positive correlation, with most areas showing a positive correlation above 0.4. On a daily scale, temperature exhibits the strongest negative partial correlation (−0.733) with snow depth, with a 10-day delay, while precipitation demonstrates the highest positive correlation (0.064) with snow depth, with a 3-day delay. The variation characteristics of snow depth and its correlation with meteorological factors on the Qinghai-Tibet Plateau exhibit significant spatiotemporal heterogeneity. This heterogeneity can be attributed to factors such as topography, ablation and accumulation time, and the influence of monsoons and westerlies around the plateau.
, Available online ,
doi: 10.12170/20230213002
Abstract:
The river-reservoir connection project in the “Meng-Kai-Ge Area” consists of the Nandong primary pump station, Nandong secondary pump station, and Changqiaohai pump station. Investigating the impact of different operation modes on the energy consumption of pump stations can enhance the project’s operational efficiency. This study establishes an optimal unit commitment model for the three pumping stations, considering both constant speed throttling operation mode and variable frequency regulation operation mode. The model is solved using the standard genetic algorithm (SGA) and the elite reservation genetic algorithm (EGA). The economic efficiency of the transformation is analyzed, taking into account the cost of the variable frequency regulation device. The research findings demonstrate that EGA exhibits similar accuracy to SGA but surpasses it significantly in terms of efficiency when solving the optimal unit commitment model for the river-reservoir connection project’s pump stations in the “Meng-Kai-Ge Area”. The energy-saving effect of frequency conversion regulation is particularly notable, with all pump stations having a relatively high-efficiency and energy-saving section within the middle range of flow. When the daily water lifting flow of the pump stations at all levels is less than 0.7 m3/s or close to full belt flow, frequency conversion transformation is unnecessary. However, in other cases, the pump stations can quickly realize positive benefits through transformation, highlighting the transformation’s significant advantages. These findings provide valuable insights for energy-saving transformations of pump stations in river-reservoir connection projects in the “Meng-Kai-Ge Area”.
The river-reservoir connection project in the “Meng-Kai-Ge Area” consists of the Nandong primary pump station, Nandong secondary pump station, and Changqiaohai pump station. Investigating the impact of different operation modes on the energy consumption of pump stations can enhance the project’s operational efficiency. This study establishes an optimal unit commitment model for the three pumping stations, considering both constant speed throttling operation mode and variable frequency regulation operation mode. The model is solved using the standard genetic algorithm (SGA) and the elite reservation genetic algorithm (EGA). The economic efficiency of the transformation is analyzed, taking into account the cost of the variable frequency regulation device. The research findings demonstrate that EGA exhibits similar accuracy to SGA but surpasses it significantly in terms of efficiency when solving the optimal unit commitment model for the river-reservoir connection project’s pump stations in the “Meng-Kai-Ge Area”. The energy-saving effect of frequency conversion regulation is particularly notable, with all pump stations having a relatively high-efficiency and energy-saving section within the middle range of flow. When the daily water lifting flow of the pump stations at all levels is less than 0.7 m3/s or close to full belt flow, frequency conversion transformation is unnecessary. However, in other cases, the pump stations can quickly realize positive benefits through transformation, highlighting the transformation’s significant advantages. These findings provide valuable insights for energy-saving transformations of pump stations in river-reservoir connection projects in the “Meng-Kai-Ge Area”.
, Available online ,
doi: 10.12170/20230613003
Abstract:
The Huang-Huai-Hai region in China faces severe water shortages, with excessive groundwater consumption posing a significant obstacle to its economic and social development. This study utilizes GRACE gravity satellite data and GLDAS land surface assimilation data from 2003 to 2021 to analyze and evaluate variations in groundwater storage in the Huang-Huai-Hai region. Statistical methods are employed to examine the spatiotemporal characteristics of these variations, and the factors contributing to changes in groundwater storage, including precipitation, evapotranspiration, groundwater supply, and inter-basin water diversion, are investigated. The results reveal that 94.2% of the Huang-Huai-Hai region experiences a decline in groundwater storage, with an average rate of −1.22 cm/a. The Haihe River Basin exhibits a decline rate of −1.75 cm/a, the Huaihe River Basin experiences a decline rate of −0.57 cm/a, and the below Huayuanko area of the Yellow River Basin has a decline rate of −2.11 cm/a. The spatial pattern of groundwater storage indicates increasing decline rates from south to north. The dominant factors influencing groundwater storage variations differ among the three basins. Precipitation has a greater impact on groundwater storage in the Huaihe River Basin compared to the Haihe River Basin, while long-term groundwater supply reduction contributes to the decline in groundwater storage in the Haihe River Basin and below Huayuankou area of the Yellow River Basin. The increasing inter-basin water diversion in recent years has led to a reduction in groundwater supply in the Haihe River Basin, alleviating the declining trend of groundwater storage. Additionally, groundwater storage in the below Huayuankou area of the Yellow River Basin has experienced rapid growth since 2020.
The Huang-Huai-Hai region in China faces severe water shortages, with excessive groundwater consumption posing a significant obstacle to its economic and social development. This study utilizes GRACE gravity satellite data and GLDAS land surface assimilation data from 2003 to 2021 to analyze and evaluate variations in groundwater storage in the Huang-Huai-Hai region. Statistical methods are employed to examine the spatiotemporal characteristics of these variations, and the factors contributing to changes in groundwater storage, including precipitation, evapotranspiration, groundwater supply, and inter-basin water diversion, are investigated. The results reveal that 94.2% of the Huang-Huai-Hai region experiences a decline in groundwater storage, with an average rate of −1.22 cm/a. The Haihe River Basin exhibits a decline rate of −1.75 cm/a, the Huaihe River Basin experiences a decline rate of −0.57 cm/a, and the below Huayuanko area of the Yellow River Basin has a decline rate of −2.11 cm/a. The spatial pattern of groundwater storage indicates increasing decline rates from south to north. The dominant factors influencing groundwater storage variations differ among the three basins. Precipitation has a greater impact on groundwater storage in the Huaihe River Basin compared to the Haihe River Basin, while long-term groundwater supply reduction contributes to the decline in groundwater storage in the Haihe River Basin and below Huayuankou area of the Yellow River Basin. The increasing inter-basin water diversion in recent years has led to a reduction in groundwater supply in the Haihe River Basin, alleviating the declining trend of groundwater storage. Additionally, groundwater storage in the below Huayuankou area of the Yellow River Basin has experienced rapid growth since 2020.
, Available online ,
doi: 10.12170/20220920001
Abstract:
To ensure the safety of towing an immersed tube tunnel, it is crucial to thoroughly investigate the motion behavior and factors that influence the process. This study employs numerical simulation to examine the towing behavior of an immersed tube tunnel under specific working conditions in a practical project. The investigation focuses on pitch angle, heave, towing speed, and towing force. The findings reveal that the immersed tube structure demonstrates excellent stability and minimal motion response during the floating process. By altering variables such as cable arrangement angle, cable length, tugboat speed, and wave direction, the study explores the impact of different factors on the towing behavior. Utilizing the Apriori algorithm, a correlation analysis of the influencing factors is conducted. The results indicate that the cable arrangement angle and cable length have a negligible effect on the towing motion response but do influence the towing force. Specifically, a cable arrangement angle of 45° and a cable length of 100 m are deemed favorable for the safety of immersed tube towing. The motion response of the immersed tube structure is most sensitive to speed, followed by wave direction angle. Therefore, it is advisable to avoid excessive towing speeds, with a recommended maximum tugboat speed of 0.77 m/s, considering the project's towing force requirements. Additionally, towing against head waves should be avoided, and whenever possible, a 45° angle relative to the wave direction should be adopted to ensure the safety and stability of the immersed tube.
To ensure the safety of towing an immersed tube tunnel, it is crucial to thoroughly investigate the motion behavior and factors that influence the process. This study employs numerical simulation to examine the towing behavior of an immersed tube tunnel under specific working conditions in a practical project. The investigation focuses on pitch angle, heave, towing speed, and towing force. The findings reveal that the immersed tube structure demonstrates excellent stability and minimal motion response during the floating process. By altering variables such as cable arrangement angle, cable length, tugboat speed, and wave direction, the study explores the impact of different factors on the towing behavior. Utilizing the Apriori algorithm, a correlation analysis of the influencing factors is conducted. The results indicate that the cable arrangement angle and cable length have a negligible effect on the towing motion response but do influence the towing force. Specifically, a cable arrangement angle of 45° and a cable length of 100 m are deemed favorable for the safety of immersed tube towing. The motion response of the immersed tube structure is most sensitive to speed, followed by wave direction angle. Therefore, it is advisable to avoid excessive towing speeds, with a recommended maximum tugboat speed of 0.77 m/s, considering the project's towing force requirements. Additionally, towing against head waves should be avoided, and whenever possible, a 45° angle relative to the wave direction should be adopted to ensure the safety and stability of the immersed tube.
, Available online ,
doi: 10.12170/20220815001
Abstract:
Vacuum combined surcharge preloading method is a commonly used foundation treatment method in coastal areas of China. However, there is a lack of engineering cases and construction experience on dam construction projects in the northern regions. Specifically, the adaptability of the conventional PVD installation process and sealing wall process to complex stratum is not clear, the sealing effect of the sealing membrane after large volume dam loading is unknown, and in winter the freezing force may damage the saturated sealing and drainage system. For this purpose, based on an earth dam project in northern China, a pilot test section was selected and installation test of prefabricated vertical drains, formation test of the sealing wall, protection test of sealing membrane and anti-freezing test of the dam foundation were carried out. The test results showed that the crawler type vibratory installation process could effectively penetrate the overlying hard soil layer, and its construction efficiency was better than “pilot hole + vibratory installation process”. The 1.2 m double-row mud mixing wall could play a good sealing effect. Non-woven cloth and woven cloth were laid on the surface of the sealing membrane, and the lightly compacted transition layer can effectively protect the sealing membrane. A 2 m anti-freezing layer on the upper layer and the foot of the earth dam can effectively protect the foundation soil layer and drainage system from freezing, and the drainage system can operate normally after the winter period.
Vacuum combined surcharge preloading method is a commonly used foundation treatment method in coastal areas of China. However, there is a lack of engineering cases and construction experience on dam construction projects in the northern regions. Specifically, the adaptability of the conventional PVD installation process and sealing wall process to complex stratum is not clear, the sealing effect of the sealing membrane after large volume dam loading is unknown, and in winter the freezing force may damage the saturated sealing and drainage system. For this purpose, based on an earth dam project in northern China, a pilot test section was selected and installation test of prefabricated vertical drains, formation test of the sealing wall, protection test of sealing membrane and anti-freezing test of the dam foundation were carried out. The test results showed that the crawler type vibratory installation process could effectively penetrate the overlying hard soil layer, and its construction efficiency was better than “pilot hole + vibratory installation process”. The 1.2 m double-row mud mixing wall could play a good sealing effect. Non-woven cloth and woven cloth were laid on the surface of the sealing membrane, and the lightly compacted transition layer can effectively protect the sealing membrane. A 2 m anti-freezing layer on the upper layer and the foot of the earth dam can effectively protect the foundation soil layer and drainage system from freezing, and the drainage system can operate normally after the winter period.
, Available online ,
doi: 10.12170/20221028003
Abstract:
Hydrological zoning is an important basis for water resources planning and an effective method for hydrologic research in data scarce areas. In China, the preliminary hydrological zoning was mainly to meet the needs of water resources planning. The national hydrological zoning mainly appeared in 1950s, and the more refined and perfect provincial hydrological zoning was centralized in the end of the 20th century. Hydrological zoning is the core content of hydrological zoning work. The hydrological zoning method mainly includes two aspects: determining the zoning indicators and determining the zoning method, which should be flexibly applied according to the needs in practical work. The current hydrological zoning indicators mainly include climate, hydrology and underlying surface, and the hydrological zoning method is mainly based on clustering method. It is mainly used to solve of the problem lack of hydrological data, as well as the ecohydrological zoning method has been developed to improve the rationality of ecological assessment. Based on the current research progress, the following points are proposed for future research: (1) to incorporate hydrological similarity theory into hydrological zoning; (2) research on regional hydrological mechanism and its application in water resources, environment, ecology and other fields; (3) test and scientific interpretation of hydrological zoning results. This study can provide theoretical basis for regional water resources planning, parameter transplantation and ecological environment protection.
Hydrological zoning is an important basis for water resources planning and an effective method for hydrologic research in data scarce areas. In China, the preliminary hydrological zoning was mainly to meet the needs of water resources planning. The national hydrological zoning mainly appeared in 1950s, and the more refined and perfect provincial hydrological zoning was centralized in the end of the 20th century. Hydrological zoning is the core content of hydrological zoning work. The hydrological zoning method mainly includes two aspects: determining the zoning indicators and determining the zoning method, which should be flexibly applied according to the needs in practical work. The current hydrological zoning indicators mainly include climate, hydrology and underlying surface, and the hydrological zoning method is mainly based on clustering method. It is mainly used to solve of the problem lack of hydrological data, as well as the ecohydrological zoning method has been developed to improve the rationality of ecological assessment. Based on the current research progress, the following points are proposed for future research: (1) to incorporate hydrological similarity theory into hydrological zoning; (2) research on regional hydrological mechanism and its application in water resources, environment, ecology and other fields; (3) test and scientific interpretation of hydrological zoning results. This study can provide theoretical basis for regional water resources planning, parameter transplantation and ecological environment protection.
, Available online ,
doi: 10.12170/20221027001
Abstract:
This study examines vertical density stratification of salt and sediment in estuaries. Data were analyzed from the south side of a 12.5 m deep channel along the north channel of the Yangtze Estuary, including water, salt and sediment measurements. The overall distribution characteristics of salt and sediment content in the north channel waters were analyzed. The vertical turbulent diffusion coefficient was calculated using the Richardson number method and PP81 zero-equation model. This investigated the effect of vertical salt and sediment density stratification on vertical turbulent diffusion in the north channel waters. Results show the diffusion coefficient increases from near-bottom to near-surface layers with stratification. Stratification has a more pronounced inhibitory effect in the middle and lower reaches. Salt stratification results in less inhibition during spring than neap tides, and less during flood than ebb tides. Sediment stratification causes more inhibition during spring than neap tides, and more during flood than ebb tides. Salt stratification is the primary inhibitory factor, with coefficients up to 5 times lower under salt versus clear water. Inhibition by sediment is weaker, with coefficients up to 2 times lower under mud versus clear water, and strongest inhibition in near-bottom layers. Combined salt and sediment stratification more markedly inhibits material diffusion, with maximum coefficients of around 22 times lower in near-bottom mid-channel areas.
This study examines vertical density stratification of salt and sediment in estuaries. Data were analyzed from the south side of a 12.5 m deep channel along the north channel of the Yangtze Estuary, including water, salt and sediment measurements. The overall distribution characteristics of salt and sediment content in the north channel waters were analyzed. The vertical turbulent diffusion coefficient was calculated using the Richardson number method and PP81 zero-equation model. This investigated the effect of vertical salt and sediment density stratification on vertical turbulent diffusion in the north channel waters. Results show the diffusion coefficient increases from near-bottom to near-surface layers with stratification. Stratification has a more pronounced inhibitory effect in the middle and lower reaches. Salt stratification results in less inhibition during spring than neap tides, and less during flood than ebb tides. Sediment stratification causes more inhibition during spring than neap tides, and more during flood than ebb tides. Salt stratification is the primary inhibitory factor, with coefficients up to 5 times lower under salt versus clear water. Inhibition by sediment is weaker, with coefficients up to 2 times lower under mud versus clear water, and strongest inhibition in near-bottom layers. Combined salt and sediment stratification more markedly inhibits material diffusion, with maximum coefficients of around 22 times lower in near-bottom mid-channel areas.
, Available online ,
doi: 10.12170/20220622001
Abstract:
The existing solution for undrained cylindrical cavity expansion, based on the modified Cam clay model, is limited in its applicability to saturated, normally consolidated, and slightly over-consolidated clays, excluding heavily over-consolidated soils and granular materials. To address this limitation, a general solution is proposed for the expansion of a cylindrical cavity in saturated soil under undrained conditions. The solution utilizes a Unified State Parameter Model (CASM) incorporating Rowe's stress-dilatancy relation to derive the elastoplastic stress-strain relationship of saturated soil. By employing the large deformation theory and introducing an auxiliary variable, expressions for the effective stress and excess pore water pressure of the soil in the elastoplastic zone are derived using the Lagrangian analysis method. A semi-analytical solution for undrained cylindrical cavity expansion is obtained under the elastic-plastic boundary conditions. The results demonstrate that the present solution yields consistent calculations with the modified Cam clay model when appropriate spacing ratio and stress-state parameters are selected, and it provides more reasonable results for heavily over-consolidated soils. Furthermore, the proposed solution can be applied to calculate undrained cylindrical cavity expansion in various types of saturated soils by adjusting the parameter values.
The existing solution for undrained cylindrical cavity expansion, based on the modified Cam clay model, is limited in its applicability to saturated, normally consolidated, and slightly over-consolidated clays, excluding heavily over-consolidated soils and granular materials. To address this limitation, a general solution is proposed for the expansion of a cylindrical cavity in saturated soil under undrained conditions. The solution utilizes a Unified State Parameter Model (CASM) incorporating Rowe's stress-dilatancy relation to derive the elastoplastic stress-strain relationship of saturated soil. By employing the large deformation theory and introducing an auxiliary variable, expressions for the effective stress and excess pore water pressure of the soil in the elastoplastic zone are derived using the Lagrangian analysis method. A semi-analytical solution for undrained cylindrical cavity expansion is obtained under the elastic-plastic boundary conditions. The results demonstrate that the present solution yields consistent calculations with the modified Cam clay model when appropriate spacing ratio and stress-state parameters are selected, and it provides more reasonable results for heavily over-consolidated soils. Furthermore, the proposed solution can be applied to calculate undrained cylindrical cavity expansion in various types of saturated soils by adjusting the parameter values.
, Available online ,
doi: 10.12170/20221116001
Abstract:
In recent years, due to super-standard flood caused by heavy rainfall, the overtopping-induced dam breach events of small-sized reservoirs often occurred in China. The failure of Sheyuegou Reservoir in Xinjiang on July 31, 2018 is a typical case. Because detailed field investigation data is available, the back analysis of this case has important theoretical significance and engineering value. Based on the dam-break video and post-failure investigation, the dam breach process of Sheyuegou Reservoir has been clarified, and the erosion characteristics of dam-break flow has been summarized. A numerical calculation method for dam breach process has been established, and can consider the evolution rule of breach morphology in the longitudinal and cross sections. By comparing the numerical and measured results, it is found that the relative errors of important dam breach parameters (i.e., peak breach flow, final breach top and bottom widths, final breach depth, and time to peak) are all within ±15%. For a numerical model of dam breaching, the numerical results have high accuracy. The parameter sensitivity analysis shows that soil erodibility coefficient has an important effect on the dam breach process, especially on the peak breach flow and time to peak. The headcut migration coefficient also has a certain influence on the dam breach process, which determines the time to peak.
In recent years, due to super-standard flood caused by heavy rainfall, the overtopping-induced dam breach events of small-sized reservoirs often occurred in China. The failure of Sheyuegou Reservoir in Xinjiang on July 31, 2018 is a typical case. Because detailed field investigation data is available, the back analysis of this case has important theoretical significance and engineering value. Based on the dam-break video and post-failure investigation, the dam breach process of Sheyuegou Reservoir has been clarified, and the erosion characteristics of dam-break flow has been summarized. A numerical calculation method for dam breach process has been established, and can consider the evolution rule of breach morphology in the longitudinal and cross sections. By comparing the numerical and measured results, it is found that the relative errors of important dam breach parameters (i.e., peak breach flow, final breach top and bottom widths, final breach depth, and time to peak) are all within ±15%. For a numerical model of dam breaching, the numerical results have high accuracy. The parameter sensitivity analysis shows that soil erodibility coefficient has an important effect on the dam breach process, especially on the peak breach flow and time to peak. The headcut migration coefficient also has a certain influence on the dam breach process, which determines the time to peak.
, Available online ,
doi: 10.12170/20221224001
Abstract:
Epoxy-coated reinforcement often exhibits inadequate adhesion to the concrete’s protective layer, compromising the overall structural stability. In contrast, polymer cementitious coatings demonstrate superior bonding to rebar compared to epoxy coatings. By employing polyacrylate latex (PA) and P·O 52.5 cement, this study explores the influence of different mass ratios of polymer cement-based coatings on engineering performance. Various tests, including crosslinking degree assessment, coating pull-out test, chloride ion permeability test, and Machu test, are conducted to investigate the impact mechanism of polymer-cement mass ratio (poly-ash ratio) on coating properties. Scanning electron microscopy-energy spectroscopy (SEM-EDS) is utilized to analyze the interaction mechanism between the polymer and cement hydration products. The comparative tests reveal that the polymer-cement ratio significantly affects the engineering performance of the coating, with an optimum range observed at 22% to 27%. Deviating from this range, either by exceeding or falling below it, diminishes the film’s strength and compactness, thereby weakening its engineering performance. Scanning electron microscopy demonstrates that the mechanism by which propylene latex cementitious coatings enhance corrosion resistance and engineering performance of steel bars lies in the polymer’s ability to fully crosslink into a film and gradually envelop the cement hydration product, forming a continuous film. This process improves the coating’s compactness and overall engineering performance. In conclusion, by adjusting the poly-ash ratio of polymer cementitious coatings, it is possible to produce superior rust-inhibiting coatings for steel reinforcement.
Epoxy-coated reinforcement often exhibits inadequate adhesion to the concrete’s protective layer, compromising the overall structural stability. In contrast, polymer cementitious coatings demonstrate superior bonding to rebar compared to epoxy coatings. By employing polyacrylate latex (PA) and P·O 52.5 cement, this study explores the influence of different mass ratios of polymer cement-based coatings on engineering performance. Various tests, including crosslinking degree assessment, coating pull-out test, chloride ion permeability test, and Machu test, are conducted to investigate the impact mechanism of polymer-cement mass ratio (poly-ash ratio) on coating properties. Scanning electron microscopy-energy spectroscopy (SEM-EDS) is utilized to analyze the interaction mechanism between the polymer and cement hydration products. The comparative tests reveal that the polymer-cement ratio significantly affects the engineering performance of the coating, with an optimum range observed at 22% to 27%. Deviating from this range, either by exceeding or falling below it, diminishes the film’s strength and compactness, thereby weakening its engineering performance. Scanning electron microscopy demonstrates that the mechanism by which propylene latex cementitious coatings enhance corrosion resistance and engineering performance of steel bars lies in the polymer’s ability to fully crosslink into a film and gradually envelop the cement hydration product, forming a continuous film. This process improves the coating’s compactness and overall engineering performance. In conclusion, by adjusting the poly-ash ratio of polymer cementitious coatings, it is possible to produce superior rust-inhibiting coatings for steel reinforcement.
, Available online ,
doi: 10.12170/20230526001
Abstract:
The proliferation of river-crossing bridges at high densities has adverse effects on rivers. To investigate the cumulative impact of bridge clusters on the hydrodynamic characteristics of river channels, a two-dimensional hydrodynamic model is employed to analyze how the construction of bridge clusters influences various hydrodynamic characteristics, such as water height and velocity. The study aims to establish a relationship between the number of bridges, bridge spacing, and hydrodynamic characteristics of river channels. The findings reveal that bridge clusters create a backwater effect upstream of the bridges and induce a surge in water height near the piers. The surge height near the piers is significantly higher than the backwater effect near the bridges. However, the impact of the surge height diminishes when the distance between bridges is eight times the width of the piers. Furthermore, the cumulative impact on the river channel increases substantially with an increase in the number of bridge clusters. Once the distance between bridges exceeds 160 times the pier width, the cumulative impact on the river channel nearly disappears. Therefore, it is crucial to consider the number of bridges and bridge spacing in bridge construction to minimize the cumulative impact of bridge clusters.
The proliferation of river-crossing bridges at high densities has adverse effects on rivers. To investigate the cumulative impact of bridge clusters on the hydrodynamic characteristics of river channels, a two-dimensional hydrodynamic model is employed to analyze how the construction of bridge clusters influences various hydrodynamic characteristics, such as water height and velocity. The study aims to establish a relationship between the number of bridges, bridge spacing, and hydrodynamic characteristics of river channels. The findings reveal that bridge clusters create a backwater effect upstream of the bridges and induce a surge in water height near the piers. The surge height near the piers is significantly higher than the backwater effect near the bridges. However, the impact of the surge height diminishes when the distance between bridges is eight times the width of the piers. Furthermore, the cumulative impact on the river channel increases substantially with an increase in the number of bridge clusters. Once the distance between bridges exceeds 160 times the pier width, the cumulative impact on the river channel nearly disappears. Therefore, it is crucial to consider the number of bridges and bridge spacing in bridge construction to minimize the cumulative impact of bridge clusters.
, Available online ,
doi: 10.12170/20230627001
Abstract:
This study focuses on the common problem of frost heave damage to slope protection structures of earth-rock dams in cold regions. An earth-rock dam project located in a cold climate zone is selected as the research subject. A finite element model is developed considering coupled water, heat, and stress processes based on the project characteristics. The full process of slope protection frost heave damage under the influence of reservoir water level variations and soil water migration within the dam is examined. The temperature field, moisture field, and displacement field variations in the earth-rock dam are analyzed. Finite element calculation displacement field results are compared to measured frost heave deformation data, verifying the calculation results. The findings show the frost heave impact range on the dam slope is approximately 2 meters. The dam slope temperature distribution depends mainly on freezing depth. The shallow dam slope temperature from 0-2 meters varies greatly with external air temperature. The internal temperature within the dam body exhibits smaller variation amplitude than the shallow slope, with some lag. Negative temperatures cause the shallow pore water phase in the dam slope to transform to ice, shown as decreasing unfrozen water content. Soil-rock mixture pore water phase change, fill water migration to the slope, and frozen peak movement towards the dam body are key factors in slope protection frost heave damage. Calculated dam slope frost heave volume is 20-30 cm, maximum 36 cm, consistent with measured deformation. Frost heave damage primarily results from combined effects of frost heave and ice thrust in soil-rock mixtures like sand and gravel cushion and dam fill. The research provides a basis for earth-rock dam slope protection design in cold regions.
This study focuses on the common problem of frost heave damage to slope protection structures of earth-rock dams in cold regions. An earth-rock dam project located in a cold climate zone is selected as the research subject. A finite element model is developed considering coupled water, heat, and stress processes based on the project characteristics. The full process of slope protection frost heave damage under the influence of reservoir water level variations and soil water migration within the dam is examined. The temperature field, moisture field, and displacement field variations in the earth-rock dam are analyzed. Finite element calculation displacement field results are compared to measured frost heave deformation data, verifying the calculation results. The findings show the frost heave impact range on the dam slope is approximately 2 meters. The dam slope temperature distribution depends mainly on freezing depth. The shallow dam slope temperature from 0-2 meters varies greatly with external air temperature. The internal temperature within the dam body exhibits smaller variation amplitude than the shallow slope, with some lag. Negative temperatures cause the shallow pore water phase in the dam slope to transform to ice, shown as decreasing unfrozen water content. Soil-rock mixture pore water phase change, fill water migration to the slope, and frozen peak movement towards the dam body are key factors in slope protection frost heave damage. Calculated dam slope frost heave volume is 20-30 cm, maximum 36 cm, consistent with measured deformation. Frost heave damage primarily results from combined effects of frost heave and ice thrust in soil-rock mixtures like sand and gravel cushion and dam fill. The research provides a basis for earth-rock dam slope protection design in cold regions.
, Available online ,
doi: 10.12170/20220708001
Abstract:
In recent years, the increase of strong typhoon frequency has posed a serious threat to the safety of the northern coast of Hangzhou Bay. It is necessary to improve the protection ability of seawalls and investigate the combination of return periods of hydraulic elements. Based on the numerical model of astronomical tide, storm surge and typhoon wave, we simulated the tide level and wave process generated by historical typhoons landing along the real route and assumed typhoons landing along the assumed route, and constructed a sample of tide level and wave height in front of Jiaxing seawall of the north coast of Hangzhou Bay. The results show that the majority of combinations of tide levels and corresponding wave heights caused by the historical typhoon are less than the combination of tide levels once-in-10-year and wave heights of the same frequency. There is only one above the once-in-10-year among the highest storm tidal levels during the landing of historical typhoons. The combination of return periods shows a combination of “high tide and low wave” return period. During the landing of the designed typhoon on the predicted path, according to the combination of hourly tide level and its corresponding wave height, when the tide level of Jiaxing seawall in Hangzhou Bay is once in 100 to 300 years, it will appear to have three kinds of phenomena about combination of returns: “equal tide and wave”, “low tide and high wave” and “high tide and low wave”. There will be two phenomena of “equal tide and wave” and “high tide and low wave” in the middle section of the seawall. In the combination of the highest tide level and maximum significant wave height in the typhoon process in front of the seawall, when the tide level return period is once in 100 to 300 years, only the phenomena of “high tide and low wave” and “equal tide and wave” appear. Therefore, the tidal level design standard for seawalls is once in 100 to 300 years, and the wave design standard should not be lower than the tide-proof standard.
In recent years, the increase of strong typhoon frequency has posed a serious threat to the safety of the northern coast of Hangzhou Bay. It is necessary to improve the protection ability of seawalls and investigate the combination of return periods of hydraulic elements. Based on the numerical model of astronomical tide, storm surge and typhoon wave, we simulated the tide level and wave process generated by historical typhoons landing along the real route and assumed typhoons landing along the assumed route, and constructed a sample of tide level and wave height in front of Jiaxing seawall of the north coast of Hangzhou Bay. The results show that the majority of combinations of tide levels and corresponding wave heights caused by the historical typhoon are less than the combination of tide levels once-in-10-year and wave heights of the same frequency. There is only one above the once-in-10-year among the highest storm tidal levels during the landing of historical typhoons. The combination of return periods shows a combination of “high tide and low wave” return period. During the landing of the designed typhoon on the predicted path, according to the combination of hourly tide level and its corresponding wave height, when the tide level of Jiaxing seawall in Hangzhou Bay is once in 100 to 300 years, it will appear to have three kinds of phenomena about combination of returns: “equal tide and wave”, “low tide and high wave” and “high tide and low wave”. There will be two phenomena of “equal tide and wave” and “high tide and low wave” in the middle section of the seawall. In the combination of the highest tide level and maximum significant wave height in the typhoon process in front of the seawall, when the tide level return period is once in 100 to 300 years, only the phenomena of “high tide and low wave” and “equal tide and wave” appear. Therefore, the tidal level design standard for seawalls is once in 100 to 300 years, and the wave design standard should not be lower than the tide-proof standard.
, Available online ,
doi: 10.12170/20220817001
Abstract:
This study aims to determine the influence of salt-freezing conditions on the durability of basalt fiber fine stone concrete and accurately predict strength changes considering nonlinear characteristics and external factors. Hydraulic structures and their environmental conditions in the saline-alkali land of Jingdian irrigation area in Gansu, China served as a test case. Indoor material tests were conducted by varying the freezing and thawing medium (clean water, 3% NaCl solution, 5% Na2SO4 solution) and basalt fiber content (0, 0.05%, 0.10%, 0.15%, 0.20%). This provided preliminary insights into uniaxial compressive strength changes of basalt fiber fine stone concrete under different salt-freeze environments. Based on laboratory results, a basic-BP model combining BPNN and the beetle antennae search algorithm (BAS) was developed to predict compressive strength changes considering varying salt-freezing conditions. Additionally, two other BPNN models improved by intelligent algorithms were constructed for comparison. Model performance and error analysis revealed the BAS-BP model predictions agreed closely with tests, demonstrating good accuracy and stability. This can greatly improve efficiency in obtaining durability test results for basalt fiber fine stone concrete. Appropriate basalt fiber content, such as 0.15%, was found to enhance salt freezing resistance, with optimal performance across factors. NaCl exposure caused more severe damage than Na2SO4 during freezing and thawing. The error analysis revealed that the BAS-BP model's predictions most closely matched the test results, demonstrating strong predictive accuracy and stability. Using this model can significantly enhance the efficiency of obtaining durability test results for basalt fiber fine stone concrete by reducing the need for physical testing.
This study aims to determine the influence of salt-freezing conditions on the durability of basalt fiber fine stone concrete and accurately predict strength changes considering nonlinear characteristics and external factors. Hydraulic structures and their environmental conditions in the saline-alkali land of Jingdian irrigation area in Gansu, China served as a test case. Indoor material tests were conducted by varying the freezing and thawing medium (clean water, 3% NaCl solution, 5% Na2SO4 solution) and basalt fiber content (0, 0.05%, 0.10%, 0.15%, 0.20%). This provided preliminary insights into uniaxial compressive strength changes of basalt fiber fine stone concrete under different salt-freeze environments. Based on laboratory results, a basic-BP model combining BPNN and the beetle antennae search algorithm (BAS) was developed to predict compressive strength changes considering varying salt-freezing conditions. Additionally, two other BPNN models improved by intelligent algorithms were constructed for comparison. Model performance and error analysis revealed the BAS-BP model predictions agreed closely with tests, demonstrating good accuracy and stability. This can greatly improve efficiency in obtaining durability test results for basalt fiber fine stone concrete. Appropriate basalt fiber content, such as 0.15%, was found to enhance salt freezing resistance, with optimal performance across factors. NaCl exposure caused more severe damage than Na2SO4 during freezing and thawing. The error analysis revealed that the BAS-BP model's predictions most closely matched the test results, demonstrating strong predictive accuracy and stability. Using this model can significantly enhance the efficiency of obtaining durability test results for basalt fiber fine stone concrete by reducing the need for physical testing.
, Available online ,
doi: 10.12170/20221213001
Abstract:
The Yellow River Estuary channels face the challenge of balancing multiple objectives, including ensuring flood control safety, preserving ecological functions, and mitigating coastal erosion in a changing environment. This study utilizes hydrological data and field investigations to analyze the flood control situation, construction demands of the Yellow River Estuary National Park, and the condition of standby channels. The Qingshuigou channel has shown significant improvement in flood control since the implementation of sand and water regulation operations at the Xiaolangdi reservoir. However, the channel remains susceptible to large floods, which may be exacerbated by the 6‱ antislope of the current bottomland. The Qingshuigou section of the Yellow River Estuary National Park lacks downstream regulation measures following the Qing 4 river-control work, necessitating the implementation of planned scientific research platforms and infrastructure to minimize flood impacts on the main channel. The Diaokouhe section requires planned ecological water compensation of 0.055 billion m3, while the coastline suffers erosion due to insufficient sediment supply. The main channel has experienced siltation and contraction, with the bottomland facing severe encroachment from social development and construction, highlighting the urgent need for protection through regulated flow. The joint application of the channels involves normal passing flow during regular conditions, diversion of water at maximum main channel discharge, and flood release through two channels. The Diaokouhe channel accommodates a certain discharge during ordinary times and diverts a portion when the Qingshuigou channel reaches 3,500 m3/s. During large floods, the two channels serve as release passages for a flow of 5,000 m3/s.
The Yellow River Estuary channels face the challenge of balancing multiple objectives, including ensuring flood control safety, preserving ecological functions, and mitigating coastal erosion in a changing environment. This study utilizes hydrological data and field investigations to analyze the flood control situation, construction demands of the Yellow River Estuary National Park, and the condition of standby channels. The Qingshuigou channel has shown significant improvement in flood control since the implementation of sand and water regulation operations at the Xiaolangdi reservoir. However, the channel remains susceptible to large floods, which may be exacerbated by the 6‱ antislope of the current bottomland. The Qingshuigou section of the Yellow River Estuary National Park lacks downstream regulation measures following the Qing 4 river-control work, necessitating the implementation of planned scientific research platforms and infrastructure to minimize flood impacts on the main channel. The Diaokouhe section requires planned ecological water compensation of 0.055 billion m3, while the coastline suffers erosion due to insufficient sediment supply. The main channel has experienced siltation and contraction, with the bottomland facing severe encroachment from social development and construction, highlighting the urgent need for protection through regulated flow. The joint application of the channels involves normal passing flow during regular conditions, diversion of water at maximum main channel discharge, and flood release through two channels. The Diaokouhe channel accommodates a certain discharge during ordinary times and diverts a portion when the Qingshuigou channel reaches 3,500 m3/s. During large floods, the two channels serve as release passages for a flow of 5,000 m3/s.
, Available online ,
doi: 10.12170/20221222002
Abstract:
The arching phenomenon in the core of earth-rock dams plays a crucial role in ensuring their safe and stable operation. The mechanical properties of the core are influenced by various factors, including complex topographic and geological conditions. This study investigates and compares the arching behavior of vertical cores, inclined cores, and lower straight upper inclined cores. Additionally, slope gradient, valley width, and overburden thickness are selected as parameters to characterize the topographic and geological conditions of the dam. A quantitative analysis is conducted using numerical calculations to examine the influence of complex geological conditions on the arching behavior of asphalt concrete cores. The findings reveal that the stress arching in the core is predominantly concentrated near the middle 3/4 of the core height and along the bank slope. The arching effect in the inclined core is relatively small, contributing to an overall improvement in the core’s force distribution. As the bank slope steepens, the arching strength in the inclined core increases, resulting in a wider area of stress transmission extending from the middle of the core to both sides of the slope. Increasing the valley width causes the stress transfer concentration to gradually shift from the core’s bottom to its sides and upper part. The overall stress arching in the inclined core does not exhibit a monotonic relationship with the increase in valley width. When the ratio of dam axis length to dam height reaches 3 to 4, the valley effect significantly reduces deformation and arching in the inclined core. Moreover, as the overburden thickness increases, the arching at the bottom of the inclined core becomes more pronounced, leading to a concentrated and regionalized distribution of the arching coefficient that increases the likelihood of local damage.
The arching phenomenon in the core of earth-rock dams plays a crucial role in ensuring their safe and stable operation. The mechanical properties of the core are influenced by various factors, including complex topographic and geological conditions. This study investigates and compares the arching behavior of vertical cores, inclined cores, and lower straight upper inclined cores. Additionally, slope gradient, valley width, and overburden thickness are selected as parameters to characterize the topographic and geological conditions of the dam. A quantitative analysis is conducted using numerical calculations to examine the influence of complex geological conditions on the arching behavior of asphalt concrete cores. The findings reveal that the stress arching in the core is predominantly concentrated near the middle 3/4 of the core height and along the bank slope. The arching effect in the inclined core is relatively small, contributing to an overall improvement in the core’s force distribution. As the bank slope steepens, the arching strength in the inclined core increases, resulting in a wider area of stress transmission extending from the middle of the core to both sides of the slope. Increasing the valley width causes the stress transfer concentration to gradually shift from the core’s bottom to its sides and upper part. The overall stress arching in the inclined core does not exhibit a monotonic relationship with the increase in valley width. When the ratio of dam axis length to dam height reaches 3 to 4, the valley effect significantly reduces deformation and arching in the inclined core. Moreover, as the overburden thickness increases, the arching at the bottom of the inclined core becomes more pronounced, leading to a concentrated and regionalized distribution of the arching coefficient that increases the likelihood of local damage.
, Available online ,
doi: 10.12170/20221020002
Abstract:
How to effectively detect abnormal data is of great significance in the field of dam safety monitoring, but the traditional method is very unstable in detecting the deviation size of abnormal data in terms of quantity. This paper proposes a deep learning-based algorithm for detecting abnormal data for dam safety monitoring, which simulates the process of manual identification of abnormal data and is divided into two stages of classification and identification to detect abnormal data, and is suitable for detecting data with uncertain change trends, in which labeled data sets are automatically produced with a feedback mechanism. The experimental results show that the algorithm of this paper has an average accuracy rate of 0.97 or more, a full rate of 0.97 or more, and an accuracy rate of 0.99 or more for the test data of various types of anomalous addition patterns, especially for the effective identification of small value anomalies, which has better detection stability, robustness and practicality than the traditional anomaly data detection methods.
How to effectively detect abnormal data is of great significance in the field of dam safety monitoring, but the traditional method is very unstable in detecting the deviation size of abnormal data in terms of quantity. This paper proposes a deep learning-based algorithm for detecting abnormal data for dam safety monitoring, which simulates the process of manual identification of abnormal data and is divided into two stages of classification and identification to detect abnormal data, and is suitable for detecting data with uncertain change trends, in which labeled data sets are automatically produced with a feedback mechanism. The experimental results show that the algorithm of this paper has an average accuracy rate of 0.97 or more, a full rate of 0.97 or more, and an accuracy rate of 0.99 or more for the test data of various types of anomalous addition patterns, especially for the effective identification of small value anomalies, which has better detection stability, robustness and practicality than the traditional anomaly data detection methods.
, Available online ,
doi: 10.12170/20221008005
Abstract:
In order to solve the problem that it is difficult to obtain the expansion law of the whole process of dike bend breach and the hydraulic characteristics of the breach flow, a 3D numerical model of gradual breach of dike bend breach is established based on FLOW-3D software, RNG k-ε turbulence model and sediment model, and the gradual breach process of the dike in the bend in the flume is simulated. The laboratory test verifies that the gradual breach model established has good accuracy and reliability. On this basis, the numerical model is used to simulate the gradual break process of a dike bend, taking the breach of a dike bend as an example. The results show that the first breach of the dike is located on the back slope of the induced breach, and the breach develops in a V-shape towards the toe line of the water facing slope. When the breach develops to the foundation, the breach is widened in an inverted trapezoid transverse direction; In addition, the variation laws of water depth and flow velocity near the breach are analyzed. In the vertical direction of the breach flow, the water depth at the breach is the highest on both sides of the breach, the middle of the breach is slightly lower and wavy, the flow velocity is fast in the middle and slow in both sides. In the parallel direction of the breach flow, the water depth gradually decreases along the direction of the breach flow, the water surface line gradually flattens over time, and the flow velocity in the 50-100m downstream of the dike is the largest, The location of the maximum flow velocity moves towards the flow direction with the break time.
In order to solve the problem that it is difficult to obtain the expansion law of the whole process of dike bend breach and the hydraulic characteristics of the breach flow, a 3D numerical model of gradual breach of dike bend breach is established based on FLOW-3D software, RNG k-ε turbulence model and sediment model, and the gradual breach process of the dike in the bend in the flume is simulated. The laboratory test verifies that the gradual breach model established has good accuracy and reliability. On this basis, the numerical model is used to simulate the gradual break process of a dike bend, taking the breach of a dike bend as an example. The results show that the first breach of the dike is located on the back slope of the induced breach, and the breach develops in a V-shape towards the toe line of the water facing slope. When the breach develops to the foundation, the breach is widened in an inverted trapezoid transverse direction; In addition, the variation laws of water depth and flow velocity near the breach are analyzed. In the vertical direction of the breach flow, the water depth at the breach is the highest on both sides of the breach, the middle of the breach is slightly lower and wavy, the flow velocity is fast in the middle and slow in both sides. In the parallel direction of the breach flow, the water depth gradually decreases along the direction of the breach flow, the water surface line gradually flattens over time, and the flow velocity in the 50-100m downstream of the dike is the largest, The location of the maximum flow velocity moves towards the flow direction with the break time.
, Available online ,
doi: 10.12170/20211210003
Abstract:
Bored screw pile in permafrost region is a new type of pile, and its vertical bearing characteristics have a great value for its popularization and application. The numerical method is verified based on indoor model test, and its bearing capacity composition mode is studied by numerical simulation, and compared with the widely used common bored pile. Finally, the estimation method of single-pile bearing capacity of the bored screw pile in permafrost region is put forward. The research shows that 90% of the bearing capacity of the bored screw pile in permafrost region comes from the mechanical occlusion between pile side concrete and permafrost, the shear strength of permafrost determines the bearing capacity of pile foundation, and the seasonal active layer has little influence on its bearing capacity, so the bearing capacity of pile body is stable all the year round. In permafrost regions, the equivalent friction calculated by axial force is far greater than the freezing force between conventional cast-in-place pile and frozen soil when the side threads of bored cast-in-place pile occlude with soil. When the pile reaches the ultimate bearing capacity, the plastic zone of the pile side is connected, and the soil around the pile is shearing. It can effectively estimate the design value of the bearing capacity of a single pile in engineering practice by improved formula to calculate the vertical bearing capacity of a single pile.
Bored screw pile in permafrost region is a new type of pile, and its vertical bearing characteristics have a great value for its popularization and application. The numerical method is verified based on indoor model test, and its bearing capacity composition mode is studied by numerical simulation, and compared with the widely used common bored pile. Finally, the estimation method of single-pile bearing capacity of the bored screw pile in permafrost region is put forward. The research shows that 90% of the bearing capacity of the bored screw pile in permafrost region comes from the mechanical occlusion between pile side concrete and permafrost, the shear strength of permafrost determines the bearing capacity of pile foundation, and the seasonal active layer has little influence on its bearing capacity, so the bearing capacity of pile body is stable all the year round. In permafrost regions, the equivalent friction calculated by axial force is far greater than the freezing force between conventional cast-in-place pile and frozen soil when the side threads of bored cast-in-place pile occlude with soil. When the pile reaches the ultimate bearing capacity, the plastic zone of the pile side is connected, and the soil around the pile is shearing. It can effectively estimate the design value of the bearing capacity of a single pile in engineering practice by improved formula to calculate the vertical bearing capacity of a single pile.
, Available online ,
doi: 10.12170/20220310003
Abstract:
In order to reveal the influence of different post grouting methods on the bearing characteristics of cast-in-place piles, based on the self-designed pressure grouting system, the open-end, closed-end and composite grouting tests of three model piles (S1, S2 and S3) located in homogeneous loess layer are carried out respectively, and the non grouting piles are set as the control. The vertical compressive load test is carried out 10 days after the grouting is completed. The grouting volume of S1, S2 and S3 piles is 3 L, the grouting pressure is 0.3 MPa, and the grouting duration is 33, 47 and 44 s respectively. The test results show that the bearing capacity of S3 is the largest after grouting, and the ultimate bearing capacity of the three piles is increased by 144%, 33.3% and 411% respectively; The lateral resistance of three grouting piles near the range of about 8 times of pile diameter from the pile end is enhanced, and the enhancement ratios under ultimate load are 170.7%, 39.5% and 233.2% respectively; After the static load test, dig out the model pile and observe the distribution of slurry on the pile side and pile end. It is found that the slurry of S1 and S2 piles returns up along the pile side, while for S3 pile, in addition to some slurry returning up along the pile side, some slurry forms a cement enlarged head at the pile bottom.
In order to reveal the influence of different post grouting methods on the bearing characteristics of cast-in-place piles, based on the self-designed pressure grouting system, the open-end, closed-end and composite grouting tests of three model piles (S1, S2 and S3) located in homogeneous loess layer are carried out respectively, and the non grouting piles are set as the control. The vertical compressive load test is carried out 10 days after the grouting is completed. The grouting volume of S1, S2 and S3 piles is 3 L, the grouting pressure is 0.3 MPa, and the grouting duration is 33, 47 and 44 s respectively. The test results show that the bearing capacity of S3 is the largest after grouting, and the ultimate bearing capacity of the three piles is increased by 144%, 33.3% and 411% respectively; The lateral resistance of three grouting piles near the range of about 8 times of pile diameter from the pile end is enhanced, and the enhancement ratios under ultimate load are 170.7%, 39.5% and 233.2% respectively; After the static load test, dig out the model pile and observe the distribution of slurry on the pile side and pile end. It is found that the slurry of S1 and S2 piles returns up along the pile side, while for S3 pile, in addition to some slurry returning up along the pile side, some slurry forms a cement enlarged head at the pile bottom.
, 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: 10.12170/20221007001
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: 10.12170/20220112001
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: 10.12170/20210114001
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, (5): 35-44.
doi: 10.12170/20211217001
Abstract:
Compared to dikes constructed on the river bed, floating dikes have the advantages over the spur dikes of minor influence to the riverine sediment transport, bed topography, ecosystem and good capability of adaptation to the fluvial conditions. Yet, floating dikes have not been applied to the river regulation, due to the limited understanding of the 3D flow structures around floating dikes. Our experimental studies were conducted to investigate the effects of the floating dike on the 3D flow structures around it. Results showed that after placing the floating dike, the surface water flow deflected into the other side of the flume, and circumfluence occurred right downstream of the dike, where both the vertical turbulent intensity and the absolute value of Reynolds stress were relatively large. Due to impediment effects of the dike, cross-sectional area decreased, causing the increase of flow velocity below and beside the dike and decrease of flow velocity upstream of it. Increase of the immersed depth or the dike length resulted in the increases of flow velocity beside the dike as well as the vertical or lateral scale of the circumfluence, while increasing the dike thickness led to the weakening, or even disappearing of the circumfluence.
Compared to dikes constructed on the river bed, floating dikes have the advantages over the spur dikes of minor influence to the riverine sediment transport, bed topography, ecosystem and good capability of adaptation to the fluvial conditions. Yet, floating dikes have not been applied to the river regulation, due to the limited understanding of the 3D flow structures around floating dikes. Our experimental studies were conducted to investigate the effects of the floating dike on the 3D flow structures around it. Results showed that after placing the floating dike, the surface water flow deflected into the other side of the flume, and circumfluence occurred right downstream of the dike, where both the vertical turbulent intensity and the absolute value of Reynolds stress were relatively large. Due to impediment effects of the dike, cross-sectional area decreased, causing the increase of flow velocity below and beside the dike and decrease of flow velocity upstream of it. Increase of the immersed depth or the dike length resulted in the increases of flow velocity beside the dike as well as the vertical or lateral scale of the circumfluence, while increasing the dike thickness led to the weakening, or even disappearing of the circumfluence.
Statistical characteristics of spanwise vortex in open-channel turbulence with step-shaped spur dike
2023, (5): 45-55.
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 shows 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 is 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 shows 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 is 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.
2023, (5): 56-67.
doi: 10.12170/20220119002
Abstract:
In order to study the load time history characteristics and pressure distribution law of high pile cap foundation under wave current, the pile cap composite foundation of a sea crossing bridge is numerically simulated. According to Stokes second-order wave theory, wave generation in numerical pool is carried out, and Reynolds averaged Navier stokes equation (RANS) is used to solve the fluid motion equation. The hydrodynamic time history and surface pressure distribution of each part of high pile cap foundation under three submergence coefficients in the range of 0~1 are calculated. The volume of fluid function (VOF) is used to track the liquid surface shape and simulate the wave shape time history. The results show that: (1) When the submergence coefficient is large, the horizontal force of the cushion cap is large and mainly comes from the combined action of wave and current; the diffracted waves in the wake area will produce negative horizontal force and negative buoyancy force; there is an extreme pressure fluctuation region on the upstream and downstream of the cushion cap. (2) With the decrease of submergence coefficient, the horizontal force of cushion cap decreases, and the horizontal force is mainly wave beating force; the vertical buoyancy force and the horizontal force of single pile increase accordingly; the diffraction effect in the wake region is reduced; the fluctuation area of extreme pressure of bearing platform is reduced until it disappears. (3) The maximum positive horizontal force of the pile foundation appears in the last row of piles on the side column; the maximum negative horizontal force appears in the last row of piles in the middle column. The research on the total force history and pressure distribution law can provide a reference for optimizing structural design.
In order to study the load time history characteristics and pressure distribution law of high pile cap foundation under wave current, the pile cap composite foundation of a sea crossing bridge is numerically simulated. According to Stokes second-order wave theory, wave generation in numerical pool is carried out, and Reynolds averaged Navier stokes equation (RANS) is used to solve the fluid motion equation. The hydrodynamic time history and surface pressure distribution of each part of high pile cap foundation under three submergence coefficients in the range of 0~1 are calculated. The volume of fluid function (VOF) is used to track the liquid surface shape and simulate the wave shape time history. The results show that: (1) When the submergence coefficient is large, the horizontal force of the cushion cap is large and mainly comes from the combined action of wave and current; the diffracted waves in the wake area will produce negative horizontal force and negative buoyancy force; there is an extreme pressure fluctuation region on the upstream and downstream of the cushion cap. (2) With the decrease of submergence coefficient, the horizontal force of cushion cap decreases, and the horizontal force is mainly wave beating force; the vertical buoyancy force and the horizontal force of single pile increase accordingly; the diffraction effect in the wake region is reduced; the fluctuation area of extreme pressure of bearing platform is reduced until it disappears. (3) The maximum positive horizontal force of the pile foundation appears in the last row of piles on the side column; the maximum negative horizontal force appears in the last row of piles in the middle column. The research on the total force history and pressure distribution law can provide a reference for optimizing structural design.
2023, (5): 68-77.
doi: 10.12170/20220628002
Abstract:
This study aims to address unfavorable flow conditions, such as vortexes and flow deviation, in the intake sump of a sluice-pump station. The effectiveness of cross-shaped vortex baffles in rectifying flow in the forebay and intake pipes is investigated using numerical simulation. The influence of different lengths of diversion piers on flow state is analyzed, considering flow velocity uniformity and speed-weighted average angle at two water levels: operating water level and low water level. The results are compared with a non-rectification scheme based on parameters from the Sizhihe sluice-pumping station. An orthogonal test method is employed to analyze the impact of the size of the cross-vortex eliminator at the horn mouth. The findings indicate that the optimal rectification scheme combines a diversion pier length three times the bell mouth diameter with a cross-vortex eliminator. The cross-vortex eliminator has an upper edge width of 60 mm, a lower edge width of 1200 mm, a lower base height of 60 mm, a thickness of 10 mm, and an overall height of 160 mm. This scheme significantly reduces the vortex area and improves flow velocity uniformity by 5.88% and 2.73%, respectively, while increasing the weighted average angle by 2.83° and 1.33° at the operating water level and low water level compared to the non-rectification scheme. The combined rectification scheme promotes uniform streamlines and effectively enhances water inlet conditions and vortex dynamics at the horn mouth. These research findings provide valuable insights for multi-parameter optimization and the engineering design of pump stations combined with sluice stations.
This study aims to address unfavorable flow conditions, such as vortexes and flow deviation, in the intake sump of a sluice-pump station. The effectiveness of cross-shaped vortex baffles in rectifying flow in the forebay and intake pipes is investigated using numerical simulation. The influence of different lengths of diversion piers on flow state is analyzed, considering flow velocity uniformity and speed-weighted average angle at two water levels: operating water level and low water level. The results are compared with a non-rectification scheme based on parameters from the Sizhihe sluice-pumping station. An orthogonal test method is employed to analyze the impact of the size of the cross-vortex eliminator at the horn mouth. The findings indicate that the optimal rectification scheme combines a diversion pier length three times the bell mouth diameter with a cross-vortex eliminator. The cross-vortex eliminator has an upper edge width of 60 mm, a lower edge width of 1200 mm, a lower base height of 60 mm, a thickness of 10 mm, and an overall height of 160 mm. This scheme significantly reduces the vortex area and improves flow velocity uniformity by 5.88% and 2.73%, respectively, while increasing the weighted average angle by 2.83° and 1.33° at the operating water level and low water level compared to the non-rectification scheme. The combined rectification scheme promotes uniform streamlines and effectively enhances water inlet conditions and vortex dynamics at the horn mouth. These research findings provide valuable insights for multi-parameter optimization and the engineering design of pump stations combined with sluice stations.
2023, (5): 78-84.
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 differ from each other. Based on the existing indicators, this study team constructed a water saving zoning index system with Jiangsu characteristics in 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 differ from each other. Based on the existing indicators, this study team constructed a water saving zoning index system with Jiangsu characteristics in 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.
2023, (5): 85-94.
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 enhance ecological protection and high-quality development in the Yellow River Basin. Based on the super efficiency EBM model of undesirable output, nine provinces (regions) in the Yellow River Basin were taken 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 were 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, 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 enhance ecological protection and high-quality development in the Yellow River Basin. Based on the super efficiency EBM model of undesirable output, nine provinces (regions) in the Yellow River Basin were taken 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 were 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, 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.
2023, (5): 95-104.
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 was 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 can provide 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 was 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 can provide reference in practice of OWT foundation design and analysis.
2023, (5): 105-112.
doi: 10.12170/20220517002
Abstract:
A new flexible hinged-frame anchoring system is developed to address the landslide risk and structural failure of traditional rigid frame anchoring structures under seismic and rainfall loads. By using the design concept of "rigid inside and flexible outside" and setting the hinge at the support connection of the traditional frame anchoring system, the new system allows for limited deformation of the slope, which can absorb some of the load through moderate energy dissipation, limit the displacement deformation of the slope, and avoid the destruction of the support itself. The calculation mechanical models of the original slope, the traditional frame anchoring slope, and the flexible hinged-frame anchoring slope are established using the Flac3D finite difference software. The safety stability of the three slopes is evaluated by comparing the shear strain increment, sliding deformation, and tensile stress, and the instability judgment and safety factor of the three different supports are determined by the strength reduction method. The results show that the flexible hinged-frame anchoring support is very effective in controlling slope sliding. In terms of improving its own stress state, the flexible support system has significant advantages over the traditional frame anchoring system, improving the overall stability and seismic performance of the slope. This study provides a new reinforcement design idea for the field of slopes and provides a basis for the application of new support systems.
A new flexible hinged-frame anchoring system is developed to address the landslide risk and structural failure of traditional rigid frame anchoring structures under seismic and rainfall loads. By using the design concept of "rigid inside and flexible outside" and setting the hinge at the support connection of the traditional frame anchoring system, the new system allows for limited deformation of the slope, which can absorb some of the load through moderate energy dissipation, limit the displacement deformation of the slope, and avoid the destruction of the support itself. The calculation mechanical models of the original slope, the traditional frame anchoring slope, and the flexible hinged-frame anchoring slope are established using the Flac3D finite difference software. The safety stability of the three slopes is evaluated by comparing the shear strain increment, sliding deformation, and tensile stress, and the instability judgment and safety factor of the three different supports are determined by the strength reduction method. The results show that the flexible hinged-frame anchoring support is very effective in controlling slope sliding. In terms of improving its own stress state, the flexible support system has significant advantages over the traditional frame anchoring system, improving the overall stability and seismic performance of the slope. This study provides a new reinforcement design idea for the field of slopes and provides a basis for the application of new support systems.
2023, (5): 113-122.
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 intensities and bank slope ratios 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 an obvious peak value, and the angle of internal friction tends to decrease. The deformation and damage of sandy soil bank slope under different rainfall intensities and slope ratios 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 intensities and bank slope ratios 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 an obvious peak value, and the angle of internal friction tends to decrease. The deformation and damage of sandy soil bank slope under different rainfall intensities and slope ratios 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.
2023, (5): 123-130.
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 is shown 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 is shown 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.
2023, (5): 131-138.
doi: 10.12170/20220411003
Abstract:
Field immersion test is an important means to study the characteristics of self-gravity collapsibility of deep loess site and evaluate its collapsibility. Based on physical and mechanical parameter tests of undisturbed loess, field immersion test was carried out in deep loess site in Lanzhou new district to test and analyze the development law of water content of soil layer and foundation settlement deformation, study the self-weight collapsible characteristics of the deep loess site, and evaluate the self-gravity collapsible subsidence of this deep loess site. Researches show that the moisture content and dry density of the undisturbed loess in Lanzhou new district increase gradually with the depth, but the porosity ratio and gravity collapsibility coefficient decrease greatly. With the increasing of water infiltration depth, the growth time of volumetric water content curve increases successively, and the time of wetting front reaching the measuring point lags more and more. The surface subsidence experiences a slow-fast-slow down-steady process, and the subsidence rate can reach 5.88 cm/d. 60% of the total subsidence is completed among 50 d. The depth range of 0~16.5 m is the soil layer with strong subsidence, and its subsidence accounts for more than 80% of the whole site. A large number of circumferential fractures developed around the test pit, with the widest width of 34 cm and the height of stage-off up to 50 cm. Based on the laboratory and field tests, 24 m can be used as the lower limit of gravity collapsibility depth and foundation treatment depth of the site. The research results can provide a reference for engineering construction in deep collapsible loess area.
Field immersion test is an important means to study the characteristics of self-gravity collapsibility of deep loess site and evaluate its collapsibility. Based on physical and mechanical parameter tests of undisturbed loess, field immersion test was carried out in deep loess site in Lanzhou new district to test and analyze the development law of water content of soil layer and foundation settlement deformation, study the self-weight collapsible characteristics of the deep loess site, and evaluate the self-gravity collapsible subsidence of this deep loess site. Researches show that the moisture content and dry density of the undisturbed loess in Lanzhou new district increase gradually with the depth, but the porosity ratio and gravity collapsibility coefficient decrease greatly. With the increasing of water infiltration depth, the growth time of volumetric water content curve increases successively, and the time of wetting front reaching the measuring point lags more and more. The surface subsidence experiences a slow-fast-slow down-steady process, and the subsidence rate can reach 5.88 cm/d. 60% of the total subsidence is completed among 50 d. The depth range of 0~16.5 m is the soil layer with strong subsidence, and its subsidence accounts for more than 80% of the whole site. A large number of circumferential fractures developed around the test pit, with the widest width of 34 cm and the height of stage-off up to 50 cm. Based on the laboratory and field tests, 24 m can be used as the lower limit of gravity collapsibility depth and foundation treatment depth of the site. The research results can provide a reference for engineering construction in deep collapsible loess area.
2023, (5): 139-148.
doi: 10.12170/20220609002
Abstract:
In order to investigate the effect of thermally activated oil shale semi-coke on the mechanical properties of concrete, oil shale semi-coke after high temperature calcination at 300 ℃, 400 ℃, 500 ℃ and 600 ℃ was selected. Semi-coke concrete was prepared by replacing cement with 5%-25% of the oil shale semi-coke. The compressive and flexural strengths of the semi-coke concrete were tested. The internal pore information of the semi-coke concrete was analyzed by nuclear magnetic resonance, while the relationship between the strength and porosity of the semi-coke concrete was studied. The results showed that with the increase of the calcination temperature for the oil shale semi-coke, the compressive and flexural strengths of the semi-coke concrete first increased and then decreased, with the optimal mechanical properties at 500 ℃. With the increase of the oil shale semi-coke content, the compressive and flexural strengths of the semi-coke concrete first increased and then decreased, where the optimal mechanical properties were achieved at a semi-coke content of 15%. The internal structure of the semi-coke concrete had many small pores. The porosity of the semi-coke concrete first decreased and then increased with the increase of the oil shale semi-coke content, where the minimum porosity was obtained at a semi-coke content of 15%.
In order to investigate the effect of thermally activated oil shale semi-coke on the mechanical properties of concrete, oil shale semi-coke after high temperature calcination at 300 ℃, 400 ℃, 500 ℃ and 600 ℃ was selected. Semi-coke concrete was prepared by replacing cement with 5%-25% of the oil shale semi-coke. The compressive and flexural strengths of the semi-coke concrete were tested. The internal pore information of the semi-coke concrete was analyzed by nuclear magnetic resonance, while the relationship between the strength and porosity of the semi-coke concrete was studied. The results showed that with the increase of the calcination temperature for the oil shale semi-coke, the compressive and flexural strengths of the semi-coke concrete first increased and then decreased, with the optimal mechanical properties at 500 ℃. With the increase of the oil shale semi-coke content, the compressive and flexural strengths of the semi-coke concrete first increased and then decreased, where the optimal mechanical properties were achieved at a semi-coke content of 15%. The internal structure of the semi-coke concrete had many small pores. The porosity of the semi-coke concrete first decreased and then increased with the increase of the oil shale semi-coke content, where the minimum porosity was obtained at a semi-coke content of 15%.
2023, (5): 149-157.
doi: 10.12170/20220512001
Abstract:
The resource utilization of the Yellow River sediment and the scarcity of boulders in the process of flood control are two important problems to be solved. In this study, artificial flood control stone was prepared by using alkali activated resource utilization of Yellow River silt, indoor compaction and on-site compaction, and the frost resistance of artificial flood control stone was studied by rapid freeze-thaw method. In addition, scanning electron microscope (SEM), X-ray diffraction (XRD) and mercury intrusion (MIP) were used to study the changes of morphology, composition and structure of artificial flood control stone, and clarify its micro mechanism. The results show that the artificial flood control stone prepared by alkali excitation has good compressive strength, which meets the requirements of flood control and emergency use; with the increase of alkali activator content, the compressive strength of artificial flood control stone firstly increases and then decreases; with the increase of freeze-thaw times, the compressive strength, mass and relative dynamic modulus of elasticity of artificial flood control stone decrease gradually; the frost resistance of alkali activated cement-based artificial flood control stone is better than that of alkali activated non cement-based artificial flood control stone, and the limit freeze-thaw cycles are 80 and 40 respectively; and the freeze-thaw cycle will not change the phase of alkali activated flood control stone, but will increase the porosity and the most probable pore size.
The resource utilization of the Yellow River sediment and the scarcity of boulders in the process of flood control are two important problems to be solved. In this study, artificial flood control stone was prepared by using alkali activated resource utilization of Yellow River silt, indoor compaction and on-site compaction, and the frost resistance of artificial flood control stone was studied by rapid freeze-thaw method. In addition, scanning electron microscope (SEM), X-ray diffraction (XRD) and mercury intrusion (MIP) were used to study the changes of morphology, composition and structure of artificial flood control stone, and clarify its micro mechanism. The results show that the artificial flood control stone prepared by alkali excitation has good compressive strength, which meets the requirements of flood control and emergency use; with the increase of alkali activator content, the compressive strength of artificial flood control stone firstly increases and then decreases; with the increase of freeze-thaw times, the compressive strength, mass and relative dynamic modulus of elasticity of artificial flood control stone decrease gradually; the frost resistance of alkali activated cement-based artificial flood control stone is better than that of alkali activated non cement-based artificial flood control stone, and the limit freeze-thaw cycles are 80 and 40 respectively; and the freeze-thaw cycle will not change the phase of alkali activated flood control stone, but will increase the porosity and the most probable pore size.
2023, (5): 158-168.
doi: 10.12170/20220330003
Abstract:
This paper summarizes the influencing factors of damage from scouring abrasion in hydropower projects and the types of abrasion resistant materials for hydropower engineering structures, focuses on the test methods of abrasion resistant property for abrasion and cavitation resistant coatings and the influencing factors involved, the types of abrasion and cavitation resistant coatings and their application, and discusses the difference in performance and the cost difference of epoxy resin wear-resistant coatings, polyurea wear-resistant coatings and wear-resistant concrete. The results show that the main influencing factors of damage from scouring abrasion in hydraulic structures are the abrasion angle of water, the current speed of water, the size of suspended particles and the content of suspended materials. The abrasion resistant coatings used for hydraulic structures are mainly epoxy resin coatings and polyurea coatings. The factors that influencing the wear-resistant property of the coatings include the elasticity and hardness of resin, the type of filler and the hardness and content of micron filler. These abrasion resistant coatings are mainly used for sand discharge tunnels, flood discharge tunnels and the overflow surfaces of hydropower projects.
This paper summarizes the influencing factors of damage from scouring abrasion in hydropower projects and the types of abrasion resistant materials for hydropower engineering structures, focuses on the test methods of abrasion resistant property for abrasion and cavitation resistant coatings and the influencing factors involved, the types of abrasion and cavitation resistant coatings and their application, and discusses the difference in performance and the cost difference of epoxy resin wear-resistant coatings, polyurea wear-resistant coatings and wear-resistant concrete. The results show that the main influencing factors of damage from scouring abrasion in hydraulic structures are the abrasion angle of water, the current speed of water, the size of suspended particles and the content of suspended materials. The abrasion resistant coatings used for hydraulic structures are mainly epoxy resin coatings and polyurea coatings. The factors that influencing the wear-resistant property of the coatings include the elasticity and hardness of resin, the type of filler and the hardness and content of micron filler. These abrasion resistant coatings are mainly used for sand discharge tunnels, flood discharge tunnels and the overflow surfaces of hydropower projects.
2023, (5): 1-8.
doi: 10.12170/20220606001
Abstract:
Large-scale irrigation area projects have long water transmission lines, a huge number of various hydraulic structures, and backbone projects, some of which are in serious disrepair. Some irrigation area projects are often in a state of illness or extended service, and the safety situation is not optimistic. On the basis of introducing the safety status of large-scale irrigation area projects in China, the research status of risk source identification, safety evaluation, reinforcement and reconstruction in large-scale irrigation area projects are emphatically discussed, and the development trend and existing problems of engineering safety management mode in large-scale irrigation area projects are summarized. It is considered that in the future, in-depth research should be made on risk identification and control technology, damage evolution of building concrete under service conditions, risk management and control mechanism, digital and intelligent management, etc., so as to ensure the safe and long-term operation of large-scale irrigation area projects.
Large-scale irrigation area projects have long water transmission lines, a huge number of various hydraulic structures, and backbone projects, some of which are in serious disrepair. Some irrigation area projects are often in a state of illness or extended service, and the safety situation is not optimistic. On the basis of introducing the safety status of large-scale irrigation area projects in China, the research status of risk source identification, safety evaluation, reinforcement and reconstruction in large-scale irrigation area projects are emphatically discussed, and the development trend and existing problems of engineering safety management mode in large-scale irrigation area projects are summarized. It is considered that in the future, in-depth research should be made on risk identification and control technology, damage evolution of building concrete under service conditions, risk management and control mechanism, digital and intelligent management, etc., so as to ensure the safe and long-term operation of large-scale irrigation area projects.
2023, (5): 9-16.
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 is mainly used in the safety monitoring of pump station building, which cannot reflect the overall state. In view of this, 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 the 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, thus providing 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 is mainly used in the safety monitoring of pump station building, which cannot reflect the overall state. In view of this, 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 the 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, thus providing a novel method for the safety monitoring of the pump station buildings.
2023, (5): 17-25.
doi: 10.12170/20220907001
Abstract:
To mitigate abnormal flow patterns, such as significant water level fluctuations, turbulence, and eddy currents in high-flow scenarios, a hydraulic model experiment and three-dimensional numerical simulation were conducted using a typical double-hole aqueduct model. The aim was to investigate the wave surge phenomenon caused by the Karman vortex street at the aqueduct’s outlet when constrained by the boundary. By employing both physical model experimentation and numerical simulation, a “spindle type” diversion pier concept was developed based on the observed mechanism. The study revealed a consistent shedding frequency between the Karman vortex street and the upstream surge wave frequency. Under boundary constraints, the Karman vortex street’s alternating shedding generated transverse alternating forces. These forces, combined with localized water blockages, induced wave transmission to the upstream region. Consequently, the upstream wave exhibited alternating patterns in response to the vortex street’s shedding. Implementing the “spindle type” diversion pier resulted in improved flow patterns at the inlet and outlet, significantly reducing the strength of the vortex street and its impact on the upstream flow pattern. Notably, the maximum amplitude reduction of the trough body exceeded 80%. Based on the results from a comparative test involving different lengths of diversion piers, the combination that offers the optimal balance between performance and cost-effectiveness is recommended. This combination consists of inlet and outlet diversion piers with an aspect ratio AR=L/W of 1.5, 2.0, respectively.
To mitigate abnormal flow patterns, such as significant water level fluctuations, turbulence, and eddy currents in high-flow scenarios, a hydraulic model experiment and three-dimensional numerical simulation were conducted using a typical double-hole aqueduct model. The aim was to investigate the wave surge phenomenon caused by the Karman vortex street at the aqueduct’s outlet when constrained by the boundary. By employing both physical model experimentation and numerical simulation, a “spindle type” diversion pier concept was developed based on the observed mechanism. The study revealed a consistent shedding frequency between the Karman vortex street and the upstream surge wave frequency. Under boundary constraints, the Karman vortex street’s alternating shedding generated transverse alternating forces. These forces, combined with localized water blockages, induced wave transmission to the upstream region. Consequently, the upstream wave exhibited alternating patterns in response to the vortex street’s shedding. Implementing the “spindle type” diversion pier resulted in improved flow patterns at the inlet and outlet, significantly reducing the strength of the vortex street and its impact on the upstream flow pattern. Notably, the maximum amplitude reduction of the trough body exceeded 80%. Based on the results from a comparative test involving different lengths of diversion piers, the combination that offers the optimal balance between performance and cost-effectiveness is recommended. This combination consists of inlet and outlet diversion piers with an aspect ratio AR=L/W of 1.5, 2.0, respectively.
2023, (5): 26-34.
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 conducted 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 conducted 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.
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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