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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).
doi: 10.12170/20220218001
Abstract:
In recent years, floods occur frequently in China, which poses a serious threat to the safety of people’s lives and property. To study and judge the flood situation in advance and reduce flood losses, according to the operational characteristics of flood and drought prevention and following the concepts of “four forecasts”, this paper puts forward an overall architecture of flood forecasting and control system based on “digital convergence - data backplane - twin platform - four pre-system”, and combs the business function and logic of the system. Based on the present situation of river system and flood control project in the Yongding River Basin, key technologies such as coupling simulation of hydrological hydrodynamic model and flood control operation model, real-time interaction between nested model and system data, and dynamic display of two- and three-dimensional geographic information are adopted, and a flood forecasting and control system of the Yongding River based on “four forecasts” is constructed to provide support for the flood dispatching decision-making of the Yongding River.
doi: 10.12170/20220704001
Abstract:
At present, the flood evacuation path in emergency plan for reservoir dam safety management was based on short time and short distance et.al principles, which are usually static paths and cannot be dynamic with the dam-break flood routing. The BREACH-MIKE21 coupling model was used to simulate the dam-break flood routing to obtain the dam-break flood submergement information, and combination the road network model to built environmental scenario model. The ant colony algorithm was used to optimize the flood evacuation path, and through adding backtracking, introducing the maximum and minimum ant colony system, improving the heuristic function to improve the optimization ability and convergence speed. By analyzing flood submergence elements frame by frame, the dam-break flood information is integrated into the algorithm, and the optimal flood evacuation path is finally obtained. The simulation results show that: (1) Under the same inundation scenario, compared with the basic ant colony algorithm, the average running time of the improved ant colony algorithm is increased by 1.6‰, the accuracy is increased by 32%, the average convergence times is reduced by 10.13 times, the convergence speed is faster and the optimization ability is stronger. (2) The optimal dynamic flood avoidance path obtained by the improved ant colony algorithm based on the evolution of dam-break flood is safer than the static path. The results of this study is suit for the requirements of emergency plan for reservoir dam safety management on dynamic process of flood avoidance transfer path, improve the efficiency of emergency transfer and reduce the impact of dam-break flood
doi: 10.12170/20220111003
Abstract:
Urban waterlogging has become an important disaster that threatens people’s lives and property. As China enters the era of "stock planning", urban renewal has become an important way to optimize spatial layout and solve urban problems. Existing studies have shown that land expansion and land use layout are important causes of urban waterlogging. The optimization of urban space layout has positive significance for alleviating waterlogging. Aiming at the innovation of the application mode of urban layout optimization in urban renewal planning under waterlogging prevention, we proposed an urban renewal planning path for alleviating waterlogging by constructing an urban spatial layout optimization model. Taking Foshan, China as an example, the model reduce the impact of urban building layout on surface runoff by 18.11% on average. The optimization process did not change the surface space on a large scale. An urban renewal planning model for alleviating waterlogging was proposed. The above work is expected to be realized through the control of total building density and the adjustment of urban surface layout in urban renewal planning work.
doi: 10.12170/20220303003
Abstract:
In the actual working conditions, the concrete of the ship lock is affected by the friction and collision of the ship's hull and the erosion and wear of the ship's traveling wave during the rising water period, and is damaged by CO2 in the air during the falling water period. In order to study the performance degradation law of the ship lock concrete under this working condition, the underwater steel ball method was used to approximate the physical wear of the ship lock concrete in the rising water period, and the rapid carbonation test was used to simulate the CO2 erosion in the falling water period. The duration of abrasion and carbonization, as well as the alternate cycle mechanism, are determined according to the design service index of the lock and the characteristics of navigability. The engineering performance degradation law of the ship lock concrete is reflected by the carbonation depth and anti-abrasion strength, and the composition and pore structure evolution of the ship lock concrete is characterized based on the thermalgravimetric analysis and mercury intrusion porosimetry. The simulation test and analysis show that the concrete of the inland ship lock exhibits a more obvious deterioration trend under the action of surface physical wear and carbonization cycle, and the abrasion accelerates the carbonization reaction to a certain extent.
doi: 10.12170/20211008001
[Abstract](23) [FullText HTML](0) [PDF 1631KB](4)
Abstract:
The sluice built on the soft soil foundation is prone to problems such as uneven foundation settlement and seepage deformation, which will induce disasters such as the sluice floor void. The existing soft foundation sluice floor vacancy dynamics diagnosis method can identify the void range. However, the sensitivity of the basic modal parameters (natural frequency and mode coefficient of the measuring point) to the sluice floor vacancy needs to be further improved. Therefore, the effect of different model parameters and their derivatives on the sluice floor vacancy needs to be further improved. To explore the influencing laws of different model parameters and their derivative quantities on the sluice floor vacancy, it is of great significance to determine the more sensitive characteristic quantities of venting dynamics of the sluice floor. The modal flexibility, which is more sensitive to structural damage, is taken as the sensitive characteristic of sluice floor void dynamics, and the mathematic model of sluice floor void description is established. The mathematical proxy model of response surface between sluice floor void control parameters and modal parameters (modal flexibility) is improved based on the change rate of the first two order modal flexibility of each measuring point. The relative deviation between the modal parameters (modal flexibility) of the sluice finite element model under corresponding working conditions and the modal parameters (modal flexibility) of the response surface mathematical model is taken as the objective function, and the sluice floor void parameter inversion is transformed into the solution of the objective function. The results show that the relative error between the inversion results and the actual void range is significantly reduced by taking three typical void conditions as examples. The model improves the accuracy of the inversion of sluice floor void and provides a reliable method for the detection and diagnosis of sluice floor void on soft foundation.
doi: 10.12170/20211031001
[Abstract](20) [FullText HTML](8) [PDF 2991KB](0)
Abstract:
The river scouring caused by air jet is important to engineering safety. In this paper, the diffusion law of jet flow in downstream water cushion is deduced based on momentum equation, the influence of water cushion velocity on jet diffusion is analyzed, and the calculation method of bottom velocity under moving water cushion is proposed. It is shown that the moving water cushion increases the jet diffusion distance, promotes the jet diffusion and the jet velocity attenuation, and reduces the bottom velocity. The results of the research are applied to the prediction of the depth of the flushing pit downstream of the spillway tunnel of Baihetan project. It is shown that the scour depth under the condition of moving water cushion is about 10% less than that under the condition of still water, and the depth of the scour pit formed by the flow on the downstream side of the channel is smaller than that formed by the flow on the upstream side of the river. The method proposed in this paper can well predict the depth of the scour pit at different locations, and the experimental results are in good agreement with the calculated results. The research results can provide a basis for the energy dissipation and anti-scour design of the downstream channel of flood discharge facilities.
doi: 10.12170/20220103003
Abstract:
During the operation period, the aqueduct experiences the cyclic fatigue effect of temperature variation for long term, which may cause the deterioration of the concrete of the aqueduct, such as micro-crack, and gradually reduce the safety degree of the aqueduct. There is no specific design-code for aqueduct design, and other relevant design-codes don’t provide clear guidance on whether to consider thermal effects for aqueduct. Taking a rectangle aqueduct in Xinjiang as an example and through the finite element software, the aqueduct temperature field is obtained and its distribution law are analyzed. Furthermore, the applicability of vertical temperature gradient pattern recommended by bridge codes in aqueduct design is discussed. The results show that the maximum vertical positive temperature difference in summer is 35.8 ℃ when the aqueduct is running, and 24.5 ℃ when the aqueduct is not running. In winter, the maximum vertical negative temperature difference is −15.1 ℃ when running water, and −7.8 ℃ when not running. The maximum transverse positive temperature difference of the aqueduct is 18.5 ℃ and the maximum transverse negative temperature difference is 11.2 ℃. Large vertical and transverse temperature gradient will produce large temperature stress, which should be taken into account in design. The vertical temperature gradient of the example is similar to the vertical temperature gradient modes recommended by various bridge codes, but there are large differences in the characteristic values, indicating that the recommended values of the bridge codes may not be directly applied to the temperature stress analysis of the aqueduct. The temperature field of aqueduct should be calculated and determined according to the structural form and operation conditions of the aqueduct.
doi: 10.12170/20211022002
[Abstract](91) [FullText HTML](42) [PDF 3170KB](21)
Abstract:
There is uncertainty for the cause of the abnormal seepage flow in the entry and outlet sections of the water-conveyance crossing structures. A comprehensive analysis method was proposed to explore the leakage cause in the outlet section of a cross-river aqueduct in a long-distance water transfer project in this research. First, the operation management data such as patrol inspection and reinforcement measure were analyzed. A statistical model was constructed to quantitatively analyze the relationship between the seepage pressure in the transition section and the uplift pressure beneath the sluice chamber, and the cannel water level, temperature, rainfall and other environmental variables. The main influencing factors of the seepage variables were preliminarily judged by the above-mentioned qualitative and quantitative analysis. Second, considering the engineering geology and hydrogeological conditions, the leakage cause of the protective structure could be further judged through the analysis of the surface deformation monitoring data. Then the leakage entrance and leakage channel was revealed based on several geophysical detection methods such as flow field method, ground penetrating radar and high-density resistivity method. Finally, according to the comprehensive analysis, it was found concluded that the leakage entered from the structural joints at the end of the transition section, and leaked out to the protective structure through the sand and gravel layer foundation of the transition section, the sluice chamber section and the connecting section. Considering the long-term operation of the water transfer project, it was difficult to stop water transfer for the aqueduct maintenance. Therefore, the anti-seepage reinforcement treatment plan, namely adding a grouting curtain to block the seepage channel beneath the sluice chamber, was proposed. The adopted comprehensive analysis method can provide reference for the analysis and treatment of similar engineering problems.
doi: 10.12170/20210801002
[Abstract](0) [FullText HTML](4) [PDF 998KB](1)
Abstract:
To study the durability of polypropylene fiber concrete (PFC) buildings in the northwest dry and cold region under the coupling effect of dry-wet and freeze-thaw cycles environment, the indoor accelerated test was designed to simulate the deterioration process of the PFC in the region under the action of dry-wet and freeze-thaw cycles environment. The mass loss rate and compressive strength loss rate were taken as the deterioration indexes. The full order time power grey prediction model was used to model the change process of the compressive strength loss rate, and the optimal structure of the model under the corresponding test conditions was determined. The results show that the mass loss rate of the specimen decreases first, then increases and then decreases until the end of the test, and the compressive strength loss rate of the specimen decreases first, then increases until the failure. In the range of fiber content taken in the test, the fiber content of 0.9 kg/m3 has the most obvious improvement effect on the resistance of the specimen under the coupling effect of dry-wet and freeze-thaw cycles. At the end of the test, the specimen with the fiber content of 0.9 kg/m3 reaches the failure standard, while the specimen under other contents is destroyed early. When the time power order h=3, the fitting degree between the full order time power grey prediction model and the original data of the deterioration process of PFC reaches 98%, and the relative error between the predicted value and the actual value is less than 0.15. The combination of indoor accelerated test and full order time power grey prediction model provides theoretical support for durability design and life prediction of concrete structures.
doi: 10.12170/20210910005
[Abstract](48) [FullText HTML](56) [PDF 1156KB](6)
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The research on advanced anticorrosion materials and technologies has always been a hot spot. This paper summarizes the application status of domestic non-metallic materials for aids to navigation (ATON) technology in marine environment, analyzes the cost and performance differences of each material for aids to navigation. The results show that reinforced concrete light beacons shall be gradually sifted out. Steel and FRP (Fiber Reinforced Plastic)-polyurea composites material and UHMWPE (Ultra High Molecular Wight Polyethylene) ATONs are still the main structural forms of light beacons. Steel buoys are still the main structural form of buoys by now. The application of UHMWPE buoys is gradually expanding, and the application scale of FRP buoys is shrinking. Finally this paper puts forward the development trend of non-metallic materials for aids to navigation. The future development trend of ATON is: improving the performance of non-metallic materials, optimizing the structure design of non-metallic material ATONs, increasing the research and development investment of non-metallic material ATONs, especially non-metallic material ATONs with light weight, high impact resistance property, low cost, anticorrosion, anti bio-foul and low water absorption rate, and formulating relevant technical specifications and standards in time.
doi: 10.12170/20211220006
[Abstract](58) [FullText HTML](53) [PDF 2471KB](5)
Abstract:
The first water supply project of north Xinjiang in expansive soil area has encountered multiple sliding failures since running. Our primary aim is to explore the sliding failure mechanism. Therefore, the indoor direct shear test, compression test, seepage test and electron microscope scanning test of soil are carried out separately, the results of mechanical properties of soil are investigated and their affecting mechanism is discussed. The cohesion decreases with the increase of water content. The internal friction angle decreases slowly when it is less than the optimal water content, and then decreases significantly. Due to dry density increasing, the cohesion increases significantly and the internal friction angle increases more slowly. According to the analysis result, the stable void ratio decreases with increasing water content, and the compressibility of soil increases. With increasing dry density, the initial void ratio decreases, and the stable void ratio tends to be constant. With increasing consolidation pressure, the structure type of soil gradually evolves from flocculation structure to turbulence and laminar flow structure, the effect of particle aggregation is obvious, the number and size of pores decrease, and the compressibility of expansive soil decreases. All the above results are obtained based on the result of scanning electron microscopy experimental test (SEM). The permeability of expansive soil is strong under low consolidation pressure, and it is small under high pressure (200~1 600 kPa), with an order of 10−6~10−8. The permeability coefficient is positively correlated with the void ratio, which can be expressed in the form of power function. The results of scanning electron microscopy (SEM) show that the loose accumulation structure changes into a closely combined laminar flow structure with increasing consolidation pressure, and the area of pores decreases, which provides the conditions for the permeability coefficient to decrease significantly.
doi: 10.12170/20220110003
[Abstract](53) [FullText HTML](52) [PDF 1727KB](9)
Abstract:
The cracks in the heel of gravity dam usually bear the action of high water head during the operation of the dam, which is prone to hydraulic fracturing failure. In this paper, the crack hydraulic fracturing coupling numerical model of gravity dam under the framework of extended finite element method is established, and the crack propagation process of gravity dam heel under the coupling of hydraulic fracturing is simulated by extended finite element method. The calculation results show that the heel of the gravity dam initially gradually extends to the dam base, and the crack propagation direction is towards the downstream. The crack angle without hydraulic fracturing is larger than that under hydraulic fracturing, and the crack angle without hydraulic fracturing coupling is smaller than that under hydraulic fracturing coupling. Before the crack propagation in the heel of gravity dam, the water pressure in the crack is basically the same as the boundary water pressure. When the crack begins to expand, the water pressure in the crack will drop, and then the crack opening width will continue to increase, and the water pressure in the crack will become the boundary full head. Hydraulic fracturing of cracks leads to the increase of type I stress intensity factor at the crack tip and reduces the stability of cracks in gravity dam. The research results provide an important theoretical basis for the hydraulic fracturing prevention of cracks in the heel of gravity dam.
doi: 10.12170/20220221001
[Abstract](13) [FullText HTML](0) [PDF 2968KB](2)
Abstract:
In response to the problem of poor effect of conventional single-method modification of expansive soil, this research team selected soil stabilizer and polypropylene fibers to improve the physical and mechanical properties of expansive soil and inhibit the expansion of internal fissures. The optimal dilution ratio of single-doped soil stabilizer and the optimal fiber dose of single-doped polypropylene fibers were obtained based on the free swelling rate, water stability test and unconfined compressive strength test. Meanwhile, the effect of soil stabilizer-polypropylene fibers composite improvement of expansive soil was analyzed under wet-dry cycling conditions based on macroscopic mechanical strength experiments and fine fracture and microscopic pore observation. From the experimental results, it can be obtained that the soil stabilizer can effectively reduce the free swelling rate of the expansive soil and enhance the water stability of the expansive soil, and the optimal dilution ratio (volume ratio) of the modified expansive soil is 1∶150. The reinforcing effect of polypropylene fibers can effectively improve the lateral limitless compressive strength of expanded soil, and the optimal fiber admixture is 0.20% (mass ratio). Polypropylene fibers and soil stabilizer can work together, and the unconfined compressive strength of the composite soil is effectively increased and the rate of strength decay is suppressed, and the expansion rate of fine and microscopic fractures of expanded soil is also effectively controlled. This study can provide reference for engineering application of soil stabilizer and polypropylene fiber composite to improve expansive soil.
doi: 10.12170/20211103004
[Abstract](32) [FullText HTML](2) [PDF 1228KB](2)
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In order to reduce the influence of large variation of lake bottom elevation sampling points on interpolation calculation and obtain high precision lake bottom topography, the influence of variation degree of elevation sampling points on interpolation is introduced into the ordinary Inverse Distance Weight (IDW) interpolation, and a lake terrain partition interpolation method considering the variation degree of elevation sampling points is proposed. By introducing the optimization method of orthogonal test optimization, the optimal power value of inverse distance in each partition is obtained. Taking Taihu Lake as an example, the interpolation effects of several interpolation methods on the bottom topography of Taihu Lake are compared. The results suggest that the regional inverse distance weighted interpolation method keeps good adaptability, it is verified by the measured elevation value, and the root mean square error is the smallest. Considering the terms of storage capacity error, comparing with Kriging method, inverse distance weighted interpolation method as well as natural neighborhood method, the average relative error is decreased by 0.97%, 0.90% and 1.37%, respectively. The interpolation effect is obviously superior to these interpolation methods. Therefore, when it comes to large topographic relief of the lake, the subregional inverse distance weighted interpolation method can obtain a high-precision lake bottom shape, and is of high application value for different types of lake bottom topography interpolation calculation.
doi: 10.12170/20210509001
[Abstract](32) [FullText HTML](44) [PDF 1746KB](4)
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In order to improve the utilization rate of surface water in small watersheds and solve the problem of irrigation water in mountainous areas, We have carried out the technical research of anti-seepage modification of Juershang silt dam in Pianguan County, Shanxi Province. Aiming at the upstream slope of the silt dam, five reconstruction schemes were put forward including original soil thickening, clay inclined wall and composite geomembrane. The seepage and slope stability of the original dam and various modification schemes were numerically simulated considering the coupling effects of seepage field and stress field. The results show that the original dam is greatly affected by the seepage water and cannot store water safely; only the original soil thickening of the upstream slope of the dam cannot make the dam meet the requirements for seepage prevention; laying a clay inclined wall or geomembrane anti-seepage body on the upstream slope can effectively reduce the infiltration line and the seepage flow, and improve the stability of the downstream slope of dam; the geomembrane scheme has better safety and feasibility than other schemes, and can be given priority if conditions permit. The research results have certain guiding significance for the anti-seepage transformation projects of similar silt dams.
doi: 10.12170/20211111001
[Abstract](54) [FullText HTML](55) [PDF 1159KB](6)
Abstract:
In recent years, the problem of insufficient discharge capacity of the existing hydraulic projects has become more and more serious due to the frequent occurrence of extreme floods. The piano key weir has a high-efficiency discharge capacity when the water head on the weir is properly low. The calculation analysis of its discharge capacity has great practical value. The discharge capacity is related to the main structural parameters of the piano key weir and the water head on the weir. In this study, the influencing structural parameters of discharge capacity of the piano key weir was summarized, and the optimal values were suggested. Different overflow patterns formed on the piano key weir under different hydraulic conditions. Low water head behavior happened when the water head flowing on the piano key weir was low. Based on the existing experimental data, the hydraulic condition and structural parameters when low water head behavior happened were statistically analyzed. A comparative analysis on the existing discharge capacity estimation formulas of the piano key weir was performed. Then, based on the existing experimental data, a new discharge coefficient formula including L, W, B, P, Wi/Wo and Bo/Bi was proposed using the least squares method and genetic algorithm, and the predicted results were in good agreement with the experimental data of a large number of different piano key weirs with the average error less than 6%. Among the estimation formulas, Machiels’ formula is suitable for the detailed analysis of the discharge of the piano key weir. The new formula in this study and Guo Xinlei’s formula are both simple in calculation and can be used to estimate the overall discharge capacity of the piano key weir, and the suitable formula can be selected according to the practical requirement.
doi: 10.12170/20211111003
Abstract:
In recent years, the research of microbial induced calcium carbonate precipitation (MICP) technology in the field of rock fracture repair has become more and more in-depth, and is gradually applied to the practical engineering field. In order to deeply study the effects of different treatment conditions and different cement concentrations on the effect of rock crack reinforcement by MICP technology, two different processes of peristaltic pump grouting and immersion grouting were used to carry out indoor tests on rock cracks, and determine the optimal process of rock crack reinforcement by microorganisms. Based on the above test results, the optimal treatment process parameters were obtained. On this basis, the test of rock crack reinforcement by microbial immersion grouting under different cement solution concentrations (0.5 mol/L, 0.7 mol/L and 1.0 mol/L) was carried out, and the quantitative analysis of the influence of cement solution concentration on the reinforcement effect was carried out. The results show that under the same cement concentration, the interfacial shear strength of rock cracks strengthened by peristaltic pump grouting process is about 0.28 kPa, the interfacial shear strength of rock cracks strengthened by immersion grouting process is about 0.89 kPa, and the interfacial shear strength of rock samples strengthened by immersion grouting is about 3.2 times that of rock samples repaired by peristaltic pump grouting. Under the condition of immersion grouting, the concentration of cement solution has a significant effect on the interfacial shear strength of reinforced rock samples. The ratio of interface cohesion between reinforced fracture and unreinforced rock sample increases linearly with the increase of cement solution concentration. For different shapes of rock samples, the results show that the growth rate of fracture interface cohesion of cylinder rock samples is significantly higher than that of cuboid rock samples.
doi: 10.12170/20211116001
[Abstract](13) [FullText HTML](3) [PDF 1914KB](3)
Abstract:
In order to investigate the seismic performance of railway gravity pier reinforced by steel plate and concrete composite after earthquake, a scale model of pier with reinforcement ratio of 0.5% was made for quasi-static test. The damaged area at the bottom of the model pier was reinforced with steel plate concrete composite. The failure mode of the reinforced pier model was studied by periodic reciprocating load test. The seismic performance was analyzed from hysteresis curve, skeleton curve, energy dissipation capacity, stiffness degradation and displacement ductility, and the finite element model was established for verification. The test results show that: (1) The pier body of the steel plate reinforced pier model is used as the transition zone to avoid the failure surface transfer caused by the concentrated force; (2) The steel plate concrete composite reinforcement can effectively improve the stiffness, energy consumption and bearing capacity of the model specimens, and significantly improve the seismic capacity of the bridge pier. The reinforcement scheme can be used for the restoration of gravity bridge pier after earthquake.
doi: 10.12170/20211002004
[Abstract](13) [FullText HTML](8) [PDF 1126KB](3)
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Accurate and effective evaluation of drought risk plays an important role in improving regional drought resistance capacity and reducing disaster risk. Based on the uncertainty characteristics of drought risk system and the chain transfer mechanism of drought risk, a regional drought risk evaluation method based on fuzzy risk matrix and connection number was proposed by introducing connection number to synthesize pessimistic matrix and optimistic matrix in fuzzy risk matrix and calculate risk grade value. The results of risk evaluation in 1999—2005 showed that the comprehensive risk level of drought in Jinan City improved from more than level 3 in 1999 to close to level 1 in 2005, and fluctuated slightly from 2001 to 2002, and the overall risk of drought tended to decrease. The evaluation method considers the interaction between subsystems, and synthesizes grades according to the change characteristics of sample indexes, so as to reflect the dynamic changes of drought risk state in each year. Compared with the traditional risk evaluation methods, the new method can distinguish the drought risk evaluation level of each sub-system and provides a new way for regional drought risk evaluation.
doi: 10.12170/20220217001
Abstract:
Reservoir bank collapse is a geological environmental disaster phenomenon with time-space boundary attributes. Time boundary refers to the time span, including long-term and short-term bank collapse. Space boundary refers to different reservoir sections. Differences in bank collapse patterns and prediction parameters are caused by differences in geological environmental conditions. At present, the short-term prediction time span of reservoir bank collapse commonly used is 2 to 10 years, but for engineering applications, there is a lack of sufficient decision-making basis, which brings difficulties to practical applications. Based on the characteristics of the reservoir water storage process, this paper proves that the selection of the short-term prediction time for bank collapse can be defined according to the time period of the reservoir water storage process. From the perspective of large-scale reservoir projects such as the Three Gorges and Xiaolangdi, the definition method is scientific and reasonable. And a decision-making flow chart for the time-space boundary of bank collapse prediction is designed. The decision-making theory of time-space boundary is applied to the short-term bank collapse prediction of Malianhe Reservoir in Gansu, and the decision-making process of its time-space boundary is expounded in detail. And from the perspective of engineering geology, suggestions are provided for the application of short-term bank collapse prediction results.
doi: 10.12170/20220826001
Abstract:
The analysis of crack initiation and instability propagation of dam concrete needs to simulate the weak discontinuity between aggregate and mortar as accurately as possible. The micron thickness of the interface transition zone makes the finite element mesh have the problems of poor mesh generation quality and large number of meshes. Zero-thickness cohesive interface elements were preset between the solid elements of different material interface. Reassembling subdomain interface configurations after presetting zero-thickness interface elements. Then the aggregate-mortar-interface multi-scale domain decomposition finite element mesh were established. Meanwhile, the gradient-enhanced continuum damage model and the cohesion model were combined to simulate the failure of aggregate and mortar matrix, also the weak link between the aggregate and cement matrix in one model. A macro-meso concurrent multi-scale domain decomposition model for discontinuous deformation of dam concrete was constructed. The model was applied to the direct tensile test simulation of a dam concrete. Both of the random aggregate models could capture the whole process from weak connection to disconnection of the interface between aggregate and mortar. The failure modes reproduced of concrete specimen were in agreement with the result of reference paper, proving that the model is reasonable, which can provide numerical test technical support for the study of damage and fracture mechanical properties of dam concrete.
doi: 10.12170/20211230004
Abstract:
In view of the problems of high cost, high maintenance cost, difficult construction, long construction period, high self-weight and limited scope of coastal erosion protection, it is proposes the use of inexpensive, easy construction, low self-weight, high corrosion resistance and low maintenance cost geogrid cage protect coastal erosion. The shape of the grating cage will influence the effect of coastal erosion stability. Based on the numerical analysis method of explicit dynamics, for the three shapes of grating cages with square section, circular section and wave-shaped section, the wave load is simulated by piston wave making and the hydrodynamic method of SPH smooth particles to simulate the water body. The contact between the water body and the geogrid cage and between the water body and the soil body is simulated by using the global property-assigned generic contact, and the tangential contact force between the geogrid cage and the coastal soil body is determined by using the penalty function. The force and displacement of geogrid cage and coastal soil body under wave load with and without geogrid cage and three shapes are analyzed with wave time history and peak value characteristics. The area with the greatest overall force of the geogrid cage is near the sea level. The use of the geogrid cage can reduce the influence of the wave on the bottom eddy current in the vertical cliff surface, and the wavy geogrid cage has a remarkable effect on the protection of coastal erosion.
doi: 10.12170/20220311001
Abstract:
A bulk cargo wharf yard foundation contains a weak layer of muddy clay layer, although two side foundations of yard were reinforced by cement mixing pile. However, a sliding failure as well as lateral translation collapse occurred where the thickest muddy clay is during the fill of ore heap on trial. In order to find the real reason for sliding failure and lateral translation collapse and to provide the design basis and reference for repair, a large centrifugal model was conducted. The filling process of the ore heap was simulated, and the vertical and horizontal displacement deformation of the surface of the ore heap and the yard foundation was measured. Firstly, the turning points of these displacement and deformation development was identified which is related to the critical point of stability and the ultimate bearing capacity of yard foundation are obtained. Secondly, based on the displacement field on the cross section of yard ground under the load of the ore heap, the failure mode and the development process of the sliding and translation failure of the bulk cargo wharf foundation were analyzed and discussed. The results showed that in the filling of the ore heap, its shallow subsoil subsidence and sliding failure first appeared due to its insufficient bearing capacity. Secondly, the subsidence of shallow subsoil occupied the space of underlying soft muddy clay layer, forcing it to lateral translate towards the side of the Nanliu River, resulting in a wider range of collapse.
doi: 10.12170/20220319001
[Abstract](21) [FullText HTML](13) [PDF 2053KB](4)
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Prestressed grouting between double-layer concrete linings of water conveyance tunnel can improve the bearing capacity of the structure, but the bearing mechanism of this kind of grouting prestressed lining structure has not been systematically explained. Based on the elastic theory, the mechanical analysis model of grouted prestressed lining considering the deformation coordination relationship is established by using the load structure method. Through the stress analysis of lining structure, the mechanism of prestressed grouting to improve the bearing capacity of lining structure is revealed, and the judgment formula of circumferential tensile stress of lining structure and the relationship between circumferential tensile strength and grouting prestress are deduced. The rationality of the theoretical method is verified by finite element numerical simulation, and the quantitative influence law of grouting prestress on lining structure is analyzed according to engineering cases. It is found that the maximum internal water pressure that the structure can bear is approximately linearly positively correlated with the grouting prestress and external water and soil pressure. The radial deformation and circumferential stress of the inner lining structure decrease with the increase of grouting prestress, while the radial deformation and circumferential stress of the outer lining structure significantly increase with the increase of grouting prestress. This analysis and calculation method considering critical conditions reveals the bearing mechanism of grouting prestressed lining structure, which can provide a theoretical basis for the mechanical analysis and structural design of this type of water conveyance tunnel.
doi: 10.12170/20220615001
Abstract:
The research on the characteristics of water increase along the sea crossing transportation facilities under the action of storm surge is of great significance to the disaster prevention and mitigation and structural safety assessment during the operation and maintenance period of transportation projects. Based on the measured typhoon data from 1951 to 2020, the variation characteristics of typhoon parameters in different ranges centered on Hong Kong-Zhuhai-Macao Bridge are statistically analyzed. It is found that the annual average number of typhoons, the maximum wind speed of typhoons and the minimum pressure in the center of typhoons in the waters near the Pearl River Estuary have not changed significantly since 1951. The storm surge mathematical model in the Western Pacific is established, and the characteristic values of storm surge in different areas along the Hong Kong-Zhuhai-Macao Bridge are calculated. The research shows that the storm surge of the Hong Kong-Zhuhai-Macao Bridge gradually decreases from west to East. The 200 years storm surge at the Zhuhai-Macao artificial island on the west side of the bridge is 3.17 m, the 50 years is 2.31 m, and the 200 years storm surge at the East-West artificial island is about 2.30 m, the 50 years is about 1.70 m. The research results can provide technical support for the safety assessment of Hong Kong Zhuhai Macao Bridge during operation and maintenance period.
doi: 10.12170/20210609001
[Abstract](172) [FullText HTML](109) [PDF 2979KB](38)
Abstract:
Compared with the general spillway, the open spillway with a wide single chute is prone to complicated flow pattern and poor aeration effect. Taking the Baleh Hydropower Project in Malaysia as an example, this study uses the VOF method and the RNG k-ε two-equation turbulence model to carry out a three-dimensional numerical simulation of the spillway flow field. The calculation and analysis of the distribution law of the hydraulic characteristics of the spillway were made under different working conditions, such as flow pattern, velocity, and pressure along the way. At the same time, a 1∶50 physical model test was carried out. After comparative analysis, the model test results were basically consistent with the numerical simulation results, which verified the accuracy and feasibility of the numerical simulation of the hydraulic characteristics of the spillway with an open-wide single chute. Then the turbulence model was used to calculate and analyze the optimized layout of the spillway aeration sill in detail. The results show that: after the 1# aeration sill is raised by 20 cm, the length of the aeration cavity behind the sill increases from 11.03 m to 19.84 m, Energy dissipation rate increased by 6.11%; after 3# aeration sill moves up 15 m along the steep slope of the chute, the impact position of the tipping water tongue moves upward, reducing the impact on the flow pattern of the tipping nose sill section. The research results have a certain reference for the optimization design of similar projects.
doi: 10.12170/20210722004
Abstract:
Due to the size limitation of the laboratory test equipment, the maximum particle size of the dam material had to be scaled down to the allowable size of the laboratory test equipment, and the particle size scaling led to changes in the test parameters. The results of the dry density, permeability coefficient, and triaxial shear tests for a barrier dam material with different maximum particle sizes show that the reduction in size leads to an increase in the content of fine particles less than 5 mm and affects the degree of compactness; as the maximum particle size decreases, the permeability coefficient of the specimen gradually decreases, and the direct use of the reduced size test results will overestimate the impermeability of the barrier dam material. Contraction rule has little effect on the strength index \begin{document}$\varphi$\end{document} value, but with the sample of maximum particle size decreases, the Duncan-Chang model parameters \begin{document}$K$\end{document} and \begin{document}${K_b}$\end{document} increase, the \begin{document}$n$\end{document} and \begin{document}$m$\end{document} decrease, the test results of the scaled size overestimate the strength of the barrier dam material and the ability of the dam to resist deformation, and the actual deformation of the dam is underestimated. The results of the study can provide an important reference for dam stability analysis and deformation analysis.
doi: 10.12170/20220406001
[Abstract](63) [FullText HTML](41) [PDF 1735KB](3)
Abstract:
The complex coupling relationship exists between water resources, economic society and ecological environment, and promoting the coupling and coordination of the three is an important prerequisite for achieving sustainable regional development. Based on the coupling coordination degree model, this paper measures the coupling coordination degree of water resources-economic society-ecological environment system in 14 cities and states of Gansu Province from 2010 to 2019, and analyzes the evolution characteristics of the coupling coordination degree by combining with the evolution model of center of gravity. The results show that (1) the overall water resources-economic society-ecological environment comprehensive evaluation index of Gansu Province showed a slight upward trend during 2010-2019, and its spatial distribution was consistent with the distribution pattern of water resources endowment, economic and social development and ecological environment management in each city and state; (2) the coupling coordination degree of the three systems in Gansu Province is between [0.52,0.54], which belonged to the basic coordination type, the spatial dimension of the coupling coordination type of each city (state) was either stable or improving; (3) the trajectory of the center of gravity of the coupling coordination degree from 2010 to 2019 was mainly in Lanzhou City, with an average annual distance of 7.19 km. A differentiated strategy should be adopted to promote the evolution of water resources-economic society-ecological environment towards advanced coupling coordination.
doi: 10.12170/20211024002
[Abstract](134) [FullText HTML](122) [PDF 1006KB](29)
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Affected by extreme weather, dam failure and accidents have occurred in recent years, and some regularity trend is gradually clear. Some new phenomenon and new directions such as the excessive flood impact, earth-rock dam overtop but not collapse, emergency response mechanism and so on should set to be studied deeply. It is necessary to analyze and study the latest dam-break and escape cases. This paper summarizes experience and draws lessons from flood control standards, monitoring and early warning, emergency response and emergency treatment, studies and puts forward enlightenments in reservoir dam safety management and flood control, and further puts forward thoughts and suggestions on strengthening dam failure risk prevention and control. Conclusion: quick lowering water level is the key to deal with the excessive flood measures; earth dam can be done and not collapse; earth and rockfill dam structure design should give full consideration to the extreme working condition of strong rainfall; it is necessary to strengthen the flood control capacity for river cascade reservoirs; management facilities had a great influence on emergency response ability; lower management influences the flood control safety significantly.
doi: 10.12170/20211203005
[Abstract](69) [FullText HTML](36) [PDF 1019KB](19)
Abstract:
Several superhigh arch dams have been built or are under construction in China. These projects are often located in special service environments with high water head, high slope and complex geological conditions. Their technical indicators have broken through the applicable scope of current codes and previous engineering cognition, including design, construction, safety monitoring, etc. Compared with ordinary arch dams, the engineering complexity of superhigh arch dams increases sharply with the dam height, and the structural mechanical behavior has more unique characteristics, leading to stringent requirements of safety control during construction and operation. The key technologies of structural behavior diagnosis of superhigh arch dams have been explored systematically, such as engineering empirical evaluation parameters, geomechanical model tests, numerical simulation analysis. Furthermore, safety control technologies have been deeply investigated, including construction quality control, temperature control and crack prevention, monitoring feedback analysis. On the basis, hot issues of health diagnosis and safety control of superhigh arch dams during future long-term operation are expounded, which are mining methods of space-time evolution characteristics, real-time diagnosis model of operation risk probability, dynamic control model of structural safety, intelligent perception and early warning technology. The aforementioned research aspects are critical for improving the future intelligent construction and management of superhigh arch dams.
doi: 10.12170/20220421001
Abstract:
For comprehensive understanding about the formation causes and mechanical mechanisms of various types of pit-collapses in the lower reaches of the Yangtze River, taking the pit-collapse occurred in the Hechangzhou head as an example, deep analysis was done, and then the soil mass instability model and displacement estimation method are proposed by the results of soil mechanics. The results show that the pit-collapse occurred in the Hechangzhou head belongs to lateral slide type. Its formation cause is that there is the silt layer easy to liquefy in the beach soil. When there is a certain external vibration disturbance factor, once the liquefaction condition is mature, the silt layer becomes a sliding layer, the liquefaction layer and the overlying soil layer would occur several times of large lateral slide. The slide soil mass would skid out of the collapse pond mouth into the deep channel groove, and then was quickly dispersed and transported to the downstream by the main rive current. The empirical formula of power function between the distance of sliding soil mass and the thickness of liquefied layer and dip Angle of sliding layer can be obtained by using mathematical statistics method. According to these results, it can provide a reference for the early warning and managing of such collapse in the lower reaches of the Yangtze River.
doi: 10.12170/20210921001
[Abstract](41) [FullText HTML](21) [PDF 1531KB](3)
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The intermediate channel between two decentralized cascade locks is an impounded navigation channel. The filling and emptying of lock chambers during lock operation leads to oscillations of the free-surface elevation in the channel, which can increase the degree of difficulty encountered maneuvering a ship and even produce ship accident in some instances. In previous works, most of the research effort has been devoted to the propagation of long waves in intermediate navigation channels. In contrast, the study of secondary waves in the channels has received less attention so far. In the present study the development of secondary waves under the layout of decentralized cascade locks for the new waterway in Three Gorges project was fully considered. A coupled model based on the basic equations of ship locking and Boussinesq equations was first established. Subsequently, the development length of secondary waves and its response to related hydraulic parameters were investigated. The results demonstrated that during lock emptying, the development length of secondary waves was solely related to the maximum discharge per unit width in a form of power function. In contrast, the relationship between the development length and the maximum discharge per unit width was not unique but depended on the initial head of lock chambers during lock filling. Based on the numerical results, two empirical formulas were proposed to predict development length under different locking operations. The present finding can provide theoretical guidance and technical support for the hydraulic design and operation of decentralized cascade locks.
doi: 10.12170/20211007002
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doi: 10.12170/20220720002
Abstract:
The wetting of rockfill material can easily lead to the uncoordinated deformation between it and the core wall, thus causing longitudinal cracks at the top of the dam and endangering the safety of the dam. Through the large-scale triaxial compression test and triaxial wetting test of rockfill materials of a hydropower station, the relationship between dilatancy ratio and stress ratio during loading and wetting process, and the relationship between wetting strain and confining pressure and stress level were studied respectively. The results show that the peak strength of the wetting specimen is basically the same as that of the initial saturated specimen, that is, the stress level of the specimen during wetting has little effect on its peak strength, but the final volume change of the specimen is obviously affected by the stress level during wetting. Therefore, the calculation of the wetting deformation of the earth-rock dam should be based on the single-line test. The consolidation of confining pressure and stress level during the triaxial wetting test has a significant effect on the wetting strain value. The higher the confining pressure, the larger the wetting volume strain, the higher the wetting stress level, and the larger the axial wetting strain. Based on this, a wetting strain calculation model considering the influence of confining pressure and stress level is proposed. In the process of loading and wetting, rockfill materials obey different stress dilatancy equations. When constructing the elastoplastic model of wetting deformation, different plastic potential functions should be used to describe the loading strain direction and wetting strain direction of rockfill materials respectively. The research results have certain guiding significance and engineering application value for the simulation of wetting deformation and crack prediction of earth-rock dam.
doi: 10.12170/20220613004
Abstract:
The sand gravel has more fine particles and is easy to be compacted. Especially under the action of heavy roller, the pore structure and permeability characteristics of the sand gravel may change after compaction, which will affect the seepage safety of the high concrete face gravel dam. In this esearch, the permeability test of sand gravel after compaction was carried out to analyze the relationship between the characteristic particle size and the equivalent pore diameter of sand gravel, as well as the influence of different porosity on the permeability of sand gravel, and verify the commonly used empirical calculation formula of permeability coefficient The research shows that, the reduction of the porosity of the sand gravel has a great impact on its permeability characteristics. Due to the large content of fine particles in the sand gravel, and the particles are tightly packed after compaction, the permeability coefficient of the sand gravel obtained from the permeability test is 1~2 orders of magnitude smaller than the calculated value of the conventional empirical formula, resulting in a large deviation. As the porosity decreases to a certain extent, the sand gravel shows certain viscous characteristics, the internal void increases, and the permeability coefficient decreases significantly. Based on the formula of China Institute of Water Resources and Hydropower Research, the effective pore reduction coefficient is introduced to modify the formula, and the results calculated from the modified formula are more accurate. This study can provide a basis for the drainage design of high concrete face gravel dam.
doi: 10.12170/20220614002
Abstract:
In recent years, the phenomenon of clogging of drainage board and sharp reduction of drainage performance due to clumping of fine soil particles around the drainage board has been found in vacuum pre-pressing projects, which is called “soil column effect”. Currently this phenomenon mostly occurs in soft foundation treatment projects dealing with newly dredged and blow-filled silt, and it is not common to see whether this phenomenon occurs in naturally deposited soft soils. Based on the slow consolidation of deep soft soils encountered in a soft foundation treatment project in the Songnen Plain, this paper carries out a numerical analysis based on the “soil column effect” and gives the attenuation coefficient through the inverse analysis of the permeability coefficient in the soil column area, and concludes that the “soil column effect” can also occur in naturally deposited soft soils when specific conditions are met, which is due to the influence of comprehensive factors such as the high water content of soft soils, strong mobility, and the unsuitability of the particle size gradation and the aperture of the drainage board.
doi: 10.12170/20220326001
Abstract:
According to the Table 1 and Table 2 of Maximum Rainfall Data of Different Period over the history years and the "7·11" rainfall in 2021 in the Qinhe River basin, the rainfall frequency curve of three representative periods of fourteen long series stations are established by using P-Ⅲ distribution, and the rainfall return period of "7·11" with maximum 24 h greater than 100 mm, maximum 6 h greater than 100 mm and maximum 1 h greater than 50 mm are calculated. According to the historical survey flood and the maximum peak discharge over the years, the frequency curves are established, and the return period of peak discharge of Wulongkou, Shanluping and Wuzhi hydrology station are calculated. The results show that: (1) The return period of the largest 24 h rainfall 351 mm in Yaotou station is about 3,000 years, of the largest 6 h rainfall 328.5 mm in Yaotou station is about 10,000 years, of the largest 1 h rainfall rank the former three is 200~300 years. (2) The return periods of flood peak discharge of Wulongkou, Shanluping and Wuzhi station are equivalent to 30 years, 10~15 years and 10 years respectively. The results can provide technical support for flood control operation in the Qinhe River Basin and the lower Yellow River.
doi: 10.12170/20220617004
[Abstract](11) [FullText HTML](1) [PDF 768KB](4)
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Hydrological similarity theory is the core research topic of comparative hydrology and an important theoretical basis for obtaining hydrological model parameters in ungauged basins. Based on the analysis of the origin and development of the concept of hydrological similarity, two basic problems of discriminant condition and applicable condition in the theory of hydrological similarity are put forward. This paper reviews the progress of hydrological similarity theory from three aspects: classification framework, hydrological similarity index and hydrological similarity evaluation, and summarizes the application of hydrological similarity theory. Finally, based on the current progress and shortcomings, three key issues are pointed out: the definition of hydrological similarity, the discriminant basis and applicable conditions of hydrological similarity, and the influence of the hydrological similarity index and hydrological similarity degree on the selection of similar basin. This research can provide a theoretical basis for hydrological forecast of ungauged basins, exploration of hydrological physical law and improvement of hydrologic similarity theory.
doi: 10.12170/20220919001
[Abstract](50) [FullText HTML](75) [PDF 1500KB](14)
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This paper introduces the basic information of dam failures in China and analyzes representative major dam failure events in different eras. Systematic statistic analysis are carried out for 3558 dams that failed in history ever since dam failure record was first available in 1954, as well as the life loss data, according to the era, dam scale, dam type, dam height, season, construction and operation period, and geographic region. It reveales the spatiotemporal distribution characteristics and social attributes of dam failures and their loss of lives, summarizes and analyzes the main reasons of dam failures. Based on statistical analysis, dam failure lessons have been summed up, countermeasures to prevent dam failure have been proposed. The results of this paper have reference significance for further improving the prevention and control system of reservoir dam failure in China and strictly preventing dam failure accidents.
doi: 10.12170/20211014001
[Abstract](78) [FullText HTML](44) [PDF 1892KB](9)
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Piping is one of the main reasons of dike and dam break in defective reservoir. Traditional seepage theories focus on piping mechanism, developing process and controlling measures, yet seldom shed light on quantitative discrimination and nonlinear characteristics of overall piping process. Groups of laboratory tests of piping process in different grading sandy gravels were conducted, and the judging method of overall piping process was proposed by the analysis of fluid regime changes based on the Reynolds number, which shows that fines content and uniformity are main influence factors of piping failure. The whole process of piping in sandy gravels can be quantitatively divided into four stages, that is, incubation (Re<0.85), formation (0.85≤Re≤5.00), evolution (5.00<Re≤50.00) and destruction (Re>50.00). During incubation and formation stages, removable fine particles are started up and adjusted, and the relationship between hydraulic gradient and seepage velocity is linear. Viscous drag force plays an important role, and seepage flow conforms to the Darcy’s law. However, during evolution and destruction stages, seepage pathway is gradually formed and developed, and removable fine particles run off rapidly. Meanwhile, the seepage velocity changes increasingly, and the relationship between hydraulic gradient and seepage velocity is nonlinear, which shows the inertial force plays a leading role. Laminar flow gradually transfers into turbulent flow, which can be described by a quadratic equation. The research findings can provide the base for piping scientific forecast and emergency disposal.
doi: 10.12170/20220719003
[Abstract](13) [FullText HTML](2) [PDF 855KB](8)
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Revealing the main influencing factors of coupled water resources-economic society-ecological environment coordination is important for strengthening the macro management of natural resources and economic society systems as well as promoting regional sustainable development. With the selection of indicators based on two dimensions of endogenous and outward dynamics, this study introduces a fixed-effects model to measure the coupled water resources-economic society-ecological environment coordination drivers in Gansu Province from 2010 to 2019 by analyzing the evolution of regional water resources-economic society-ecological environment coupling. The results show that: ① The level of economic development and technological development have a positive effect on the improvement of the level of coupled water resources-economic society-ecological environment coordination in Gansu Province, with regression coefficients of 0.029 and 0.021 respectively, and passing the 1% significance test. ② The factors influencing the zoning areas differ significantly, the improvement of the level of environmental protection and economic development has a catalytic effect on the improvement of the coupling coordination of the sub-regions. In the context of accelerating economic society development in Gansu Province, policies and incentives of relevant drivers should be coordinated to promote the coupled evolution of water resources-economic society-ecological environment system.
doi: 10.12170/20211207002
Abstract:
In order to enrich the theory on development and utilization of landslide dam and explore the feasibility of its improvement and reinforcement, the residual landslide dam caused by Yigong landslide was sampled, the indoor vibroflotation model tests with different frequencies were designed, and the reinforcement effect and compaction mechanism of vibroflotation method on landslide dam material were studied. The sand rain method was used for the sample placement in the model tests to comprehensively test the cumulative dissipation law of pore pressure, the development law of earth pressure, reinforcement effect and repeating vibration effect of the foundation after vibroflotation. The test results indicated that the earth pressure and excess pore pressure in the loose landslide dam material rise rapidly during the penetration of the vibrator. Under the pull-up and segmental vibration retention of the vibrator, the excess pore pressure of the landslide dam material showed a general trend of small rise, dissipation and gradual stability. With the increasing number of vibroflotation (after 2-3 repeating vibrations), the soil pressure of the foundation gradually stabilized, and the peak value of excess pore water pressure gradually decreased and tended to be stable. Therefore, the reinforcement effect of vibroflotation on loose landslide dam material was obvious. After vibroflotation, the cone resistance of landslide dam material was greatly increased. However, after the densification of landslide dam material, the increasing number of repeating vibration was unable to further improve the reinforcement effect effectively. The vibroflotation reinforcement mechanism of landslide dam material mainly included vibrator squeezing, consolidation drainage, and vibroflotation compaction. The vibroflotation design scheme meeting the requirements of Yigong landslide dam material was: vibroflotation with 125 Hz frequency for 4-5 times or vibroflotation with 150 Hz frequency for 2-3 times.
doi: 10.12170/20211021002
Abstract:
The anti-sliding stability is the most basic requirement for one gravity dam. It can be regarded as the abnormal deformation behavior. The traditional ways to determine the early-warning value of dam deformation safety are commonly based on deterministic structure parameters and mathematical models. The uncertainty characteristics of the relevant influencing factors are lack of consideration. In order to solve the above problem, the theory of uncertainty analysis is applied. In this paper, the response surface method is introduced to fit the functional relation between the water pressure component of gravity dam deformation and anti-sliding stability reliability based on the analysis of the correlation between dam deformation, anti-sliding stability reliability and water depth before the dam. According to the current reliability design specification, an anti-sliding stability reliability-based approach determining the early-warning value of deformation safety for gravity dam is proposed and verified in the actual engineering case. The rationality of the conclusion is proved by comparing with the result of the typical small probability method. The proposed method can be regarded as useful complements and mutual verification means for the traditional methods.
doi: 10.12170/20210309004
Abstract:
During the implementation of water conservancy and flood control and disaster mitigation, such as river closure and quick closuring earth-rock dike breaches, a strong local scour occurs at the gap or mouth. A 3D numerical model of local scour was verified by the experiments of previous studies, and this model was applied to simulate the local scour around the dike and the Riverbed under the one-way and two-way advancement patterns at the gap width B/H = 4.3 and 5.8. The influence of advancement patterns on the development of local scour around dike was analyzed. The results show that in the case of one-way advancement pattern, the gap flow was deflected by the dike to the other side. The local scour of the upstream dike head is always intense in the whole process. Due to the deflection of the dike, the locations of intense scouring downstream are different. The intense scouring area is located at the bottom of the upstream end of the dike at B/H=5.8, and this area was located at the wrapping head downstream at B/H = 4.3. In the case of two-way advancement pattern, the flow is distributed symmetrically along the gap axis. The gap width only affects the intensity of local scouring on the dike. The diving flow and eddy are the main reasons for local scour around the dike.
doi: 10.12170/20211128001
Abstract:
The area of yellow tide soil (YTS) and lime concretion black soil (LCBS) accounted for 87% of the total area of the Northern Anhui Plain, and the LCBS contained calcareous nodules inside, which seriously affected the soil properties and thus reduced the yield. Therefore, the differences between the two soils were investigated in terms of soil physical and chemical properties, soil hydraulics parameters and soil moisture, and the driving factors affecting the variability of soil moisture in YTS and LCBS were analyzed together with hydro-meteorological factors. The results showed that the pH and bulk weight of YTS and LCBS were significantly different, and the contents of total nitrogen, total phosphorus and alkaline solution nitrogen were not significantly different; the effective water holding capacity of YTS from 0 to 50 cm was significantly larger than that of LCBS, and the water retention was better. Soil water of YTS gradually decreased with increasing depth; soil water of LCBS gradually increased with increasing depth. The drivers affecting soil water variation in YTS are groundwater depth of burial and rainfall; the drivers affecting soil water variation in LCBS are ground temperature, groundwater depth of burial and relative humidity. This study can provide a reference for improving the soil properties of LCBS and enhancing crop yield.
doi: 10.12170/20211206001
Abstract:
Based on the combined analysis of soil arching effect and reinforcement effect between piles, an improved Hewlett model for load sharing calculation of geosynthetic-reinforced and pile-supported embankments (GRPSE) is established. Firstly, the governing equations of spherical arch and plane arch are solved respectively, according to whether the soil arch is in a plastic state and combined with the vertical force balance condition of pile-soil, then the load sharing of embankment filling is initially determined. Secondly, the differential equation for controlling the stress balance of the geosynthetic reinforcement can be built and solved without presetting the deflection form, the overlying load of the reinforcement belt is assumed to be an inverted triangle distribution in line with the actual working conditions, and the Winkler foundation model is applied to consider the soil reaction between piles within the influence range of one reinforcement belt. Thereafter, the embankment loading can be redistributed according to the calculated reinforcement effect. It proves that the improved model can reasonably predict the load sharing and the stress results of reinforcement according to the verification and discussion of case studies and the comparative analysis of several models. Parameter analysis shows that the improved model can reasonably predict the influence of geometric and material parameters on load sharing of GRPSE.
doi: 10.12170/20220410003
[Abstract](11) [FullText HTML](8) [PDF 1539KB](0)
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In order to further study the external characteristics of axial flow pump device with volute outlet channel, ensuring the safe and stable operation of Jiangou pump station after construction, the hydraulic performance of Jiangou pump station was studied based on the model test and its operation scheme of was optimized. The result shows that when the pump station works with the blade angle of −2 °, the pump device could operate with the highest efficiency of 71.4% in which case the flow and head are similar to the designed condition, indicating that it can be used as the designed angle for the future operation of the pump station. With the gradual increase of head, the flow decreases gently which has satisfied the economic requirements of long-time and large flow drainage of the pumping station. Additionally, the cavitation performance of the pump device has met the design requirements and when the blade angle is −4 °, the runaway speed reaches the highest value which is less than twice the rated speed in which case the runaway characteristics are excellent. In conclusion, the performance of the pump device tested is relatively excellent as a drainage pump device which has the great value of in-depth research and development. This study can provide some reference for the design of drainage engineerings with similar heads and large flow rates.
doi: 10.12170/20211124003
[Abstract](10) [FullText HTML](0) [PDF 2003KB](0)
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doi: 10.12170/20220112001
[Abstract](10) [FullText HTML](0) [PDF 2699KB](1)
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To study 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. First, three-dimensional GBM was generated based on the X-ray diffraction results and particle flow code. Then, the mesoscopic parameters was calibrated according to results of uniaxial compression tests of intact marble sample, and numerical model containing various fissure parameters was constructed. Finally, the process of the deformation and failure along with the energy evolution of numerical samples were simulated and analyzed. The results show that the strength of sample increases first and then decreases with increasing the 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 are 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. The results provide certain reference value for analyzing the influence of fracture spatial distribution on rock deformation and failure.
doi: 10.12170/20211118003
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Controlling the blast-induced damage is of significance for the stability of division pier in the excavation of the large-scale navigation lock. Based on the on-site experiment, the peak particle velocity (PPV) induced by production boreholes were compared, and the damage evolution characteristics were analyzed with the help of the software LS-DYNA. Moreover, through the analysis of the on-site experiment results and numerical results, the blasting excavation scheme of large-scale navigation lock were optimized. The research results indicated that the rock mass damage induced by production blast-holes will strength the pre-crack vibration isolating effect. With the increase of the width of the blast-induced damage zone, the vibration isolating effect is gradually increased, and finally stabilized at 50%. The attenuation rate of PPV increases with the width of blast-induced damage zone, when the width of the damage zone reaches 4cm, the attenuation rate gradually slows down. The damage cumulative characteristics induced by production and pre-splitting crack vibration isolation effect should be taken into consideration in the excavation of the large-scale navigation lock. Therefore, the optimizations of blasting excavation, which including the cutting blasting and construction presplitting blasting were put forward to reduce the blast-induced damage to reserved rock mass and optimize the blasting effect.
doi: 10.12170/20210903001
[Abstract](11) [FullText HTML](0) [PDF 2020KB](0)
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In order to study the infiltration law of unsaturated loess, the infiltration model test of remolded loess is carried out, the change of volume moisture content at different positions and the development process of wetting front are analyzed, the development and change law of infiltration water content in horizontal and radial direction is studied, and the infiltration depth at different time is calculated by Green-Ampt model considering air pressure, which is com Pared with the measured value. The research shows that the change trend of volume moisture content at different measuring points is basically the same, and it would go through six stages: stability-rapid growth-reaching peak-rapid decrease-re-growth-maintaining stability; The immersion infiltration process is affected by infiltration depth, infiltration path, viscous resistance and air pressure. The deeper the infiltration depth and the farther away from the central axis, the more delayed the development of wetting front and the smaller the infiltration rate. As the depth increased from 0cm to 100 cm, the infiltration rate decreased from 14.93 cm/h to 1.67 cm/h. The relationship between vertical infiltration rate and infiltration depth at different positions is fitted, it is found that the vertical infiltration rate and the infiltration depth have a quadratic relationship, and the fitting degree is above 0.9. Radial water migration is the result of the combined action of radial water diffusion and vertical water infiltration in the upper part of the depth, so it is faster than vertical water infiltration. The development trend of wetting front in the model is consistent with the measured vertical infiltration, however, the calculated value of infiltration depth is larger than the measured value at the late infiltration stage. The research results can provide a reference for the study of loess foundation infiltration.
doi: 10.12170/20211118005
[Abstract](26) [FullText HTML](18) [PDF 2774KB](7)
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In order to study the effect of freeze-thaw cycles and loading strain rate on the compressive behavior of hydraulic roller compacted concrete, actual mix design and construction technology of hydraulic concrete dam project was referred to prepare specimens, and the freeze-thaw tests with various cycles (0, 25, 50, 75) and dynamic uniaxial compressive tests with different loading strain rates (10−5/s, 10−4/s, 10−3/s, 10−2/s) were conducted for roller compacted concrete. The freeze-thaw appearance and failure mode subjected to dynamic uniaxial compressive loading and freeze-thaw cycles were analyzed. The effect of freeze-thaw cycles and strain rates on uniaxial compressive strength, peak strain and stress-strain curves were studied, and the corresponding relationship were established based on multiple regression analysis method. The results show that the compressive strength increases linearly with the increasing strain rates and reduces with the increasing freeze-thaw cycles in accordance with two-polynomial relation. The peak strain reduces with the increasing strain rates in accordance with two-polynomial relation, and increases with the increasing strain rates in accordance with two-polynomial relation. By comparing the theoretical stress-strain curves obtained from the constitutive model with the experimental curves, it reveals that they are in good agreement within the studied range of strain rates and freeze-thaw cycles.
doi: 10.12170/20211129001
[Abstract](22) [FullText HTML](21) [PDF 1732KB](1)
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It is the sand particle gradation and the sediment mineral composition which affect most the measurement of the suspended sediment concentration with the turbidity method. The field non-cohesive sediment of the Yellow River were used to prepare sandy water with different particle sizes and suspended sediment concentration. Based on the group of experiments including fixed size particle of sediment, coarse and fine particle of sediment, and mixed particle of sediment, the influence of the sediment gradation on the measured turbidity of OBS was quantitatively analyzed, and the influencing mechanism was preliminarily discussed. The results show that under the condition of fixed size particle of sediment, the influence characteristic of non-cohesive sediment particle size on the water turbidity conforms to the Mie scattering law. The magnitude of the impact of the suspended sediment concentration on OBS output turbidity is in the order of 101~102, while the impact of the sediment particle size is in the order of 10−1~100. The relationship of the specific surface area of the suspended sediment and the measured turbidity of OBS accords with linear distribution in the same sediment concentration condition. A formula between the sediment concentration and the OBS output turbidity is established considering the influence of non-cohesive sediment gradation, which can accurately reflect the impact of non-cohesive sediment particle size differences and sediment concentration changes on water turbidity. This work can provide reliable evidence not only for the accuracy of the calculation of the sediment concentration and water turbidity but also for the calibration of the measurements results.
doi: 10.12170/20220216004
[Abstract](24) [FullText HTML](17) [PDF 887KB](5)
Abstract:
Rain and flood are valuable natural resources. Rain and flood resources utilization both have a long history and are vital water resources utilization ways. In recent years, practical technologies of rain and flood resources utilization have advanced greatly, but there are still remarkable misunderstandings on their basic conceptions. Extensive use of some nonstandard terms brought confusion to scientific research and practice. Therefore, in light of the relevant history and reality and according to the basic theory of hydrology, a discussion on rain and flood resources utilization is drawn and preunderstanding was obtained in this paper. The natural resources and water resources properties of rain and flood were clarified. Then, the basic connotation and definition of rain and flood resources utilization were summarized. Also, the relationship between rain resources utilization and flood resources utilization was analyzed. In addition, the normalization of some technical terms including so called rainwater reuse and flood reuse were clarified. This paper is helpful to eliminate the misunderstandings about rain and flood resources utilization and consolidate the theoretical basis of the safe and efficient utilization of rain and flood resources. Our understanding create good prerequirements for the scientific evaluation, planning and technology innovation of rain and flood resources utilization.
doi: 10.12170/20220111001
[Abstract](31) [FullText HTML](45) [PDF 3126KB](4)
Abstract:
Concrete is the most widely-used structure materials, and modern concrete is produced with a low water to binder ratio and high binder materials content to obtain high performances, leading to a significant increase in autogenous shrinkage (AS), and thus triggering a large tensile stress under restraint and further a serious early-age cracking, which deteriorates the concrete durability, shortens the service life and causes an incalculable loss, especially in hydraulic mass concrete and thin-walled concrete structures. This paper reviewed the literatures on the latest achievements and progress home and abroad for AS and its regulation in recent years, summarizing and comparatively analyzing the latest achievements and progress upon methods and devices for AS “time-zero” and deformation measurement, AS prediction models and AS regulation techniques, pointing out the flaws in current research and giving the further research direction on some key problems, and setting a reference for practical engineering and further AS study.
doi: 10.12170/20210805001
[Abstract](73) [FullText HTML](48) [PDF 2244KB](6)
Abstract:
Alkali-aggregate reaction is called the "cancer" of concrete and is one of the important factors affecting the durability of concrete. For the concrete structure with active aggregate, how to predict the long-term deformation of concrete caused by alkali-aggregate reaction and reasonably evaluate the overall safety of the structure is a problem of close concern to the project. In this paper, the research progress of long term deformation prediction models for alkali-aggregate reaction of concrete is reviewed. The existing models are classified into 5 categories: mathematical modeling of macroscopic expansion, phenomenological model of macroscopical deformation of structures, models based on aggregate expansion, models based on ASR gel and models based on material migration. The advantages, disadvantages and application scope of various models are analyzed. It is proposed that the prediction model of ASR long-term expansion needs to consider the effect of alkali ion diffusion into the aggregate, SiO2 dissolution and the composition of ASR gel, and the reaction ring model or gel pocket model should be selected according to the petrographic analysis.
doi: 10.12170/20211115001
[Abstract](77) [FullText HTML](42) [PDF 2205KB](5)
Abstract:
In order to discuss the mechanical properties and fracture characteristics of dam concrete, three-point bending test of concrete beam was carried out based on two different concrete mix ratios (named C0.48 and C0.43 respectively according to different moisture content) provided by a hydraulic complex project and on-site coarse and fine aggregates. The relevant mechanical properties such as slump, compressive strength and splitting strength were determined, and the effects of different mixing ratios on fracture parameters such as fracture surface, cracking load and instability load, critical effective crack length and double K fracture toughness were analyzed. The test results show that, the collapse of C0.48 concrete is greater than that of C0.43 concrete. The compressive strength and splitting strength of C0.48 concrete are lower than that of C0.43 concrete. The coarse aggregate of C0.48 concrete fracture surface is not obvious as that of C0.43 concrete. The cracking load, destabilization load, critical effective crack length and fracture toughness of C0.43 concrete are higher than those of C0.48 concrete, which indicates that C0.43 concrete has high strength, good ductility and good toughness.
doi: 10.12170/20211029002
[Abstract](48) [FullText HTML](70) [PDF 1088KB](5)
Abstract:
Dongting Lake area is one of the areas with frequent flood disasters in China. With the increasing frequency of extreme weather in recent years, it is of great practical significance to study the flood control situation of Dongting Lake area under historical extreme floods. Taking the floods of the Yangtze River in 1870, 1935 and 1954 as the research object, by establishing a one-dimensional and two-dimensional coupled hydrodynamic model of the Yangtze River, Dongting Lake and flood storage and detention area, the water level and excess flood in Dongting Lake area are simulated under the conditions of existing topography and engineering measures. The results show that under the condition of compensation operation of the Three Gorges and upstream reservoirs, if the floods in 1870, 1935 and 1954 occur, the excess flood volume near Jingjiang River and Chenglingji decreases significantly. Combined with the application of flood storage and detention areas in Jingjiang area and Chenglingji area, Dongting Lake area can safely spend the flood. The regulation and storage of the Three Gorges reservoir has greatly reduced the peak discharge of Zhicheng, the peak discharge of the the three rivers in Southern Jingjiang has also decreased, and the water level of each station in Dongting Lake area has decreased; The application of flood diversion in the flood storage and detention area has reduced the water level of Lianhuatang, increased the water surface gradient of Jingjiang River, and further reduced the peak flow of the three rivers in Southern Jingjiang. Due to the reduction of upstream water and downstream water level, the water level in the lake area has further decreased. By quantitatively predicting the flood control situation of the middle reaches of the Yangtze River and Dongting Lake area, it provides a scientific basis for the governance of Dongting Lake and lays a foundation for improving the management ability of flood control and disaster reduction in the lake area.
doi: 10.12170/20210114001
[Abstract](65) [FullText HTML](67) [PDF 2174KB](6)
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.
doi: 10.12170/20190322001
[Abstract](557) [FullText HTML](273) [PDF 764KB](19)
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.
Display Method:
2022, (5).
[Abstract](34) [FullText HTML](35) [PDF 9288KB](33)
Abstract:
2022, (5): 0-0.
[Abstract](33) [FullText HTML](19) [PDF 372KB](11)
Abstract:
2022, (5): 1-11.   doi: 10.12170/20211015001
[Abstract](124) [FullText HTML](77) [PDF 1665KB](25)
Abstract:
Water resources vulnerability is an important measurement of water security and the basis of regional sustainable development. Taking Henan Province and its 18 cities as evaluation unit, the index system of water resources vulnerability evaluation was established by considering three subsystems of natural condition, social economy as well as water supply and consumption. Entropy Weight Method and Linear Weighting Method were used to calculate water resources vulnerability of typical dry year. The water resources subsystem index and vulnerability index were investigated from city, region to the entire province. The Contribution Model was applied to identify the principal contribution factors of water resources vulnerability in order to provide a scientific basis for water resources management in Henan Province. The results show that the subsystem indexes range from water resources natural condition index, water resources supply and consumption index, to water resources socio-economic index. And there exists a certain difference in water resources subsystem index and vulnerability index at different levels of urban cities, regions, and province with the both indexes increasing from southwest to northeast. The water resources vulnerability for the entire Henan Province is classified as Grade Ⅲ, which is medium vulnerability. The contribution of the three sub-systems to water resources, vulnerability for the main cities and the whole province follows a same rank order from natural condition, water supply and consumption condition, to social economic condition. The four indicators of the natural condition sub-system are principal contribution factors to water vulnerability. The per-mu chemical fertilizer conversion scalar in the socio-economic subsystem and the per-capita comprehensive water consumption and per-mu irrigation water consumption in the water-supply-consumption subsystem are also major contribution factors to water resources vulnerability. The three subsystems should take “multi-channel water supply, improving the capacity of water supply”,“rationally expanding cities and towns, optimizing population and economic structure, improving urban living and production level”,“improving water utilization efficiency, saving water”as the breakthrough points to achieve accurate “vulnerability reduction”, so as to guide the sustainable development of water resources.
2022, (5): 12-20.   doi: 10.12170/20210923001
[Abstract](190) [FullText HTML](74) [PDF 4162KB](45)
Abstract:
The Yellow River Basin involves a vast area, complex and diverse issues, and the corresponding research contents are relatively rich. There is a problem of inconsistency in the scope and partition of spatial research. Based on the Yellow River’s major national strategic objectives, tasks and different research needs, considering the relevance of the river basin and administrative regions in terms of resources utilization, economic development and ecological protection, the defined spatial research scope of the Yellow River Basin covers the Yellow River Basin, the administrative regions that the Yellow River mainstream flows through, prefectural regions involved in the Yellow River Basin, and the entire provincial regions that the Yellow River flows through, and other research scopes and divisions are also expounded. Then, four regional definition schemes are compared and analyzed from multiple aspects (i.e., spatial scope, research object and content, administrative management), and the relationship between different schemes is further clarified. According to the principles of pertinence and purpose, we systematically sort out the selection of different research contents on the spatial scale, and solve the problem of under what circumstances a spatial scale can or should be selected. The research results can provide a unified standard and reference basis for subsequent studies in the Yellow River Basin.
2022, (5): 21-30.   doi: 10.12170/20210926003
[Abstract](48) [FullText HTML](40) [PDF 3782KB](11)
Abstract:
Analyzing the sensitivity of water supply and demand balance in different regions to changes in precipitation, based on the spatial distribution of cloud water resources and precipitation efficiency, is helpful to determining the location of normalized artificial precipitation enhancement, and is of great significance to the realization of the coordinated use of air and land water resources. We take the Beisanhe River Basin as the research area, analyze the response of the study area’s incoming water demand to precipitation changes based on the Xin’anjiang Model and Penman-Montes formula, and discuss the sensitivity of the water supply and demand balance of different computing units to precipitation changes. The results show that when precipitation increases, the rate of increase in annual water production in the basin is greater than that in dry years and extreme dry years, and the water demand for farmland irrigation is roughly linear. Without considering external water transfer and groundwater overexploitation, the resource water shortage of the basin under the natural precipitation scenario is 3.546 billion cubic meters (precipitation frequency p=50%), 4.317 billion billion cubic meters (p=75%) and 4.630 billion cubic meters (p=95%), and the peak of water shortage appears in May, July and August, respectively. The sensitivity of each unit’s water shortage to changes in precipitation is mainly dominated by changes in water production, and shows a gradual decrease in space from north to south. When the average annual precipitation increases by 20%, water shortage in the north region will reach 150% or more, the central region will be between 30% and 50%, and the southern region will decrease by less than 15%.
2022, (5): 31-39.   doi: 10.12170/20210906002
[Abstract](50) [FullText HTML](51) [PDF 1091KB](10)
Abstract:
The comprehensive evaluation index system of water resources and industrial upgrading of the Yellow River Basin was constructed. Based on the indices from index calculation, a spatio-temporal analysis was performed. Using PVAR model, with Granger causality test, impulse response and variance decomposition, the interaction between water resources and industrial upgrading of the eight provinces in the Yellow River Basin over the years 2010 to 2019 was empirically analyzed. According to the analysis results, the corresponding countermeasures and suggestions were proposed. The results indicated that: (1) It was difficult for the eight provinces in the Yellow River Basin to promote the industrial structure adjustment by optimizing the water resources utilization pattern. It was necessary to find new driving forces of development, enhance the added value of the industrial chain, and establish a modern industrial system; (2) The optimization of water resources utilization of the eight provinces in the Yellow River Basin had a promoting effect on enhancing the industrial environmental friendliness. Great efforts should be made to promote the sustainability of water resources utilization in the Yellow River Basin, and ecological compensation mechanism should be established; (3) The improvement of industrial environmental friendliness of the eight provinces in the Yellow River Basin played a positive role in improving the condition of water resources. Vigorous efforts should be made to develop renewable energy, promote the green level of industry, and restore the status of water resources.
2022, (5): 40-49.   doi: 10.12170/20210914001
[Abstract](66) [FullText HTML](38) [PDF 1560KB](15)
Abstract:
In this study, we comprehensively compared the flood in 2020 with three historical floods in 2016, 1999 and 1991 in the Taihu Lake Basin, and analyzed the similarities and differences of the precipitation and water level elements corresponding to the four floods. It was found that in terms of the time distribution, the flood-causing precipitation processes in 1991, 1999 and 2016 were relatively concentrated but with intermittent periods, while the flood-causing precipitation in 2020 could be regarded as a continuous precipitation process, with a larger cumulative rainfall but a more uniform time distribution. In terms of the spatial distribution, the flood-causing precipitation in 1991 and 2016 were “Northern Type”, with precipitation in the northern sub-areas in the Taihu Lake Basin significantly higher than other sub-areas. However, the flood-causing precipitation in 1999 was “Southern Type”, with precipitation in the southern sub-areas higher than other sub-areas. However, in 2020, the flood-causing precipitation had different spatial distribution, with relatively small gaps among all the sub-areas. Influenced by the precipitation process, the water level of the Taihu Lake for the floods in 1991, 1999 and 2016 had a remarkable fall or a stable period. However, for the flood in 2020, it showed a continuous increasing process. During the flood period in 2020, the highest water level at the representative gauges in the southern sub area of Zhexi obviously exceeded that in 1991 and 2016, but the water level situation in the northern sub-areas of Huxi and Wuchengxiyu was less severe than in 1991, 1999 and 2016. In general, the intensity of floods in the Taihu Lake Basin in 2020 was lower than that in 1999 and other two years, and its disaster losses were also significantly smaller. However, the flood in 2020 was still of important value to the rainstorm and flood design and operation in the Taihu Lake Basin and its sub-areas.
2022, (5): 50-60.   doi: 10.12170/20210714002
[Abstract](76) [FullText HTML](55) [PDF 8911KB](15)
Abstract:
It is of great significance to study the evolution of regional extreme precipitation for scientific response to regional water resources utilization and disaster prevention and reduction under the changing environment. In this work, six extreme precipitation indices defined by the ETCCDI (Expert Team on Climate Change Detection Monitoring and Indices) are selected to analyze the temporal and spatial evolution of extreme precipitation in the Pearl River Delta region by using the linear trend, Kriging interpolation and cross wavelet methods. Besides, the correlation between atmospheric circulation anomalies and extreme precipitation is identified. The results show that: (1) Except for CWD, all the indices have increased by various magnitudes during the period of 1961—2017. It indicates that extreme precipitation is increasing in the Pearl River Delta, but the change is not significant. (2) The stations with increasing trends are mainly located in the central and northern parts of the region, and the stations with a significant change are in the northern part of the Pearl River Estuary and the northern part of the region. (3) The spatial distribution of each index is similar but slightly different for various climate states. The spatial patterns of trends for the four states are significantly different, with the change magnitudes increased from State 1 to State 4. (4) The CDD index is significantly affected by IOD, while the ENSO significantly influences the other indices.
2022, (5): 61-68.   doi: 10.12170/20210728006
[Abstract](55) [FullText HTML](25) [PDF 1565KB](3)
Abstract:
Underwater track vehicle will compress and shear the soil as it walks over a soft clay seabed. The compression reflects the depth of penetration and the strength of clay, and the shearing decides the traction that clay could provide. Traditional bevameter technique comprises two separate sets of tests, one is a plate penetration test and the other is a shear test, to simulate this process, ignoring the interaction effect between compression and shearing. In this paper, a new work method of torsional penetrometer is proposed, unifying the compression and shearing of seabed into the sequential penetration and torsion of the penetrometer. The validity and feasibility of the torsional penetrometer concept are verified by comparisons with the previous indoor model tests. In view of the normal solidified soft clay common in the deep sea, by means of finite element method connected with Modified Cam-clay Model, the sensitivity analysis of grouser height and pitch is conducted based on the torsional penetrometer. Finally, the influence of track parameters on the mobilized strength of soft clay seabed is explored. The results show that the grouser height and pitch have a significant effect on the strength of soft clay, and appropriately increasing the tooth height and reducing the pitch will help to give full play to the strength of soft clay.
2022, (5): 69-77.   doi: 10.12170/20210805008
[Abstract](91) [FullText HTML](66) [PDF 2239KB](7)
Abstract:
In order to study the energy dissipation characteristics of open ditch combined with the side ports located in an in-chamber culvert designed for a large-scale lock chamber with an extreme high water head, in case of the water head 60 m and the useful dimension of the lock chamber 280 m×40 m (length×width), the three-dimensional turbulent numerical simulation method was used to analyze the parameters such as velocity, turbulent energy distribution, remaining specific energy and flow velocity distribution uniformity, and present the energy dissipation characteristics of the single open ditch with double-layer side ports and the double open ditches with single-layer side ports. Moreover, the corresponding energy dissipation results between them were compared. The results show that for the case of the single open ditch with the double-layer side ports, when the ratio of vertical spacing d between ports to square root of side ports area D, d/D, increases from 2.29 to 5.71, the energy dissipation results become better firstly and then worse. When d/D reaches 3.43, the corresponding energy dissipation results become the best. In addition, the widening type of the double open ditches (the ratio of one open ditch width b to square root of side ports area D, b/D=2.71) has better energy dissipation effect than that of the type of the single open ditch with the double-layer side ports. The research results can provide a technical support for the design of energy dissipators in similar ship locks.
2022, (5): 78-85.   doi: 10.12170/20210816001
[Abstract](30) [FullText HTML](62) [PDF 2537KB](7)
Abstract:
The measured data of fracture comprehensively reflect the influence of complex factors on macroscopic crack behavior of hydraulic concrete structure. The aging component is an important basis for evaluating crack working behavior. In this research, the crack working behavior is diagnosed based on the velocity and acceleration criteria. Considing the actual situation, the typical crack location of hydraulic concrete structure is selected to install a crack meter group, and the measured data of cracks experiencing adverse load conditions are monitored and obtained. Then, the crack statistical model reflecting the nonlinear effect of temperature is established, and the aging component is separated and obtained. Finally, the velocity and acceleration criteria are used to diagnose the aging component. The application analysis of measured fracture data shows that the fitting effect of the crack statistical model considering the effect of nonlinear temperature is good. Although the aging components of some measuring points of the cracks in a gate storehouse of a flood diversion sluice at the Wangfuzhou Water Conservancy Project do not converge, they tend to close. Thus, it is diagnosed that the cracks of the sluice are currently in a stable state. This method can reflect the time-varying law of cracks simply and reliably, and provide a reference for the diagnosis of working behavior of cracks in hydraulic concrete structures.
2022, (5): 86-93.   doi: 10.12170/20210818003
[Abstract](112) [FullText HTML](52) [PDF 1409KB](8)
Abstract:
Loess has poor engineering performance and must be treated before it can be used as a roadbed filler. In order to improve the bearing capacity of the loess subgrade, and better solve the engineering disease problem of the loess subgrade, bentonite and lime are added to the loess roadbed filler, and the unconfined compressive strength test and nuclear magnetic resonance test of different combinations of bentonite-lime-loess are carried out. From the perspective of soil strength and pore structure, each content is studied. Bentonite-lime improves the strength and pore structure of loess roadbed fillers. The test results show that bentonite can effectively fill the pores of loess, lime can make the dispersed particles in the soil form a whole, and increase the unconfined compressive strength of the soil by 4.01 times; the unconfined compressive strength of the improved loess increases with the maintenance. Compared with plain loess, the porosity of modified loess decreases, and the proportion of large pores decreases significantly. Scanning through a microscopic electron microscope found that the soil particles were connected as a whole, and the large pores between the particles were basically filled. Therefore, the improvement effect of bentonite and lime on loess filler is more significant.
2022, (5): 94-101.   doi: 10.12170/20210728002
[Abstract](56) [FullText HTML](62) [PDF 1376KB](10)
Abstract:
The instability disaster of reservoir bank slope will cause huge losses to the benefit of the project and the safety of surrounding life and property, and the displacement monitoring data can directly characterize the safety status of reservoir bank slope. In view of the traditional deformation and displacement analysis, only a single monitoring point is considered, and the similarity and relevance of displacement between different monitoring points still need to be excavated. Based on the clustering method in the field of spatio-temporal data mining, considering the attribute characteristics and spatial characteristics of measuring points, K-means algorithm is used to measure the similarity between measuring points and realize the division of measuring points; based on the division of measuring points, the projection clustering algorithm optimized by genetic algorithm is used to map the high-dimensional data to the low-dimensional space. By extracting the characteristics of measuring point data, the purpose of screening the measuring points needing attention and compressing the data order is achieved. Based on practical engineering data, it is shown that the spatio-temporal clustering mining method is convenient and effective, and gradually reduces the monitoring data of slope displacement. The method can be used for monitoring data mining of similar reservoirs.
2022, (5): 102-112.   doi: 10.12170/20210826002
[Abstract](69) [FullText HTML](32) [PDF 6911KB](8)
Abstract:
Considering the heterogeneity and low permeability of the clay materials, the fracture grouting reinforcement characteristics of the clay are analyzed in view of the disease treatment of soft clay stratum in underground engineering. Based on Weibull distribution function theory, a heterogeneous clay formation model was constructed, and the clay was simulated by splitting grouting. Based on the results of grouting simulation, the influence of different uniformity and permeability coefficients on the grouting effect of clay splitting was analyzed. The results show that the difficulty of splitting grouting increases with the increase of the uniformity of soil mass, and the crack produced by splitting of soil mass with higher uniformity is relatively single and the distribution range of crack is smaller. The crack width is larger and the influence range is wider when the soil is less homogeneous. The length and growth amplitude of slurry vein expansion decrease with the increase of soil permeability coefficient. The width of slurry vein in the soil with a large permeability coefficient is larger than that in the soil with a low permeability coefficient. The length of slurry vein in the soil with a small permeability coefficient is always larger, and the farther the slurry vein is from the grouting hole, the smaller the width. The research has important guiding significance for the engineering application of fracture grouting in soft clay stratum.
2022, (5): 113-122.   doi: 10.12170/20210929002
[Abstract](34) [FullText HTML](20) [PDF 2091KB](6)
Abstract:
The arch aqueduct on pile foundation is formed by beam-column and block structure. The structure should be discretized to beam element and isoparametric element respectively in finite element method analysis. But there is a problem of how to overcome the coordination of corner displacement between beam elements and isoparametric elements. Based on the generalized displacement formula of the beam element node as the master node, the generalized displacement expression between the rotational displacement of the beam element node and the displacement of the embedded isoparametric element node is established. By setting different grid sizes and element stiffness, the applicability of master-slave or slave-master generalized displacement mode between beam element and isoparametric element for structural analysis of arch aqueduct on pile foundation is studied and discussed. The method is also applied to the analysis of an arch aqueduct project. The research results can be popularized to all the interaction problems between beam, slab, column and block structure.
2022, (5): 123-128.   doi: 10.12170/20210830001
[Abstract](72) [FullText HTML](22) [PDF 1121KB](10)
Abstract:
In order to accurately and quickly obtain the water pressure of different parts of the water-passing structure in the hydraulic model test, a method and a system for the intelligent acquisition of the water depth of the piezometric pipe group based on image recognition technology have been proposed and designed. The system adopts a non-contact (shot from a side) image acquisition method which can shoot real-time moving images of water surface buoys in a large number of pressure measuring tubes (reflecting the changing process of water depth), and then import the image data into the computer; the software recognition system adopts grayscale, binary values and opening operations to preprocess the image in preparation. When pretreatment work is finished, findContours would be used to obtain the centroid coordinates of the water surface buoys of each piezometer tube, which would be converted into actual water level data through calibration coefficients, and finally the time series of the synchronous changes of the water depth in each piezometer tube would be obtained. Compared with the traditional manual measurement method, the verification result of hydraulic model test shows that the data error obtained by this method is no more than ±1.5% compared with the traditional manual measurement method, but the acquisition method is faster, the data is richer, and the accuracy is higher.
2022, (5): 129-137.   doi: 10.12170/20210721001
[Abstract](51) [FullText HTML](45) [PDF 1245KB](5)
Abstract:
In view of the shortage of rainfall data in small and medium watersheds and the difficulty of accurate flood forecasting, we proposed to use linear cointegration and set pair analysis (SPA) to interpolate and transfer the observational rainfall data under typhoon rain and non-typhoon rain, and carried out the research on flood forecasting of Tuo Ying Reservoir. The results show that: (1) Based on the typhoon rain cointegration calculation results, it is found that there is a cointegration relationship between rainfall stations. The Nash coefficients of the cointegration simulation results and the measured rainfall are both above 0.85, and the correlation coefficient reaches 0.90. The main rain peak and the raining error are small. The calculation results are good and the integration theory can be used for data interpolation when short of rainfall data. (2) The non-typhoon rain rainfall sequence is decomposed by supplementary ensemble empirical mode (CEEMD) and SPA, and the optimal plan for data migration is drawn up according to the comprehensive connection degree, which significantly improves the effectiveness and accuracy of the migration of rainfall data, and improves flood forecasting accuracy. The method proposed in this paper provides a new idea for the interpolation and transfer of rainfall data in other regions with both typhoon storm and non-typhoon storm.
2022, (5): 138-147.   doi: 10.12170/20210715002
[Abstract](79) [FullText HTML](43) [PDF 1498KB](11)
Abstract:
The joint operation of reservoirs brings huge economic and social benefits, and also has a lot of impacts on the river ecology. In order to improve the comprehensive benefits of power generation, navigation, ecology and Qingshitan Reservoir storage of the joint operation of Lijiang parallel reservoirs, the multi-objective parallel reservoirs operation model considering ecological flow requirement of fish is developed. The model is optimized by Non-Dominated Sorted Genetic Algorithm-Ⅲ. The results show that: (1) Compared with regular operation, parallel reservoirs optimal operation can ensure the benefit of power generation, and guarantee the benefit of navigation and ecology at the same time. (2) The constructed multi-objective parallel reservoir ecological operation model maintains the rate of ecological flow requirement above 47% in dry, normal and wet years. In particular, the ecological demand of fish during the winter, spawning and breeding periods is guaranteed. (3) The implementation of joint operation of the Lijiang parallel reservoirs can alleviate the pressure of water supply of Qingshitan Reservoir, and increase the reservoir storage in dry and wet years by 22.26×106 m3 and 24.55×106 m3, respectively. This study can provide a reference for multi-objective ecological operation of parallel reservoirs.
2022, (5): 148-156.   doi: 10.12170/20210416002
[Abstract](86) [FullText HTML](79) [PDF 2361KB](11)
Abstract:
In order to improve the water environment of the main urban area of Changzhou City, through the combination of numerical simulation calculation and field test, the research on the scheme of improving the water environment of smooth flowing water was carried out. Using high-quality and abundant water from the Yangtze River as the water diversion source, the Weicun water conservancy project and the Zaogang water conservancy project were used to divert water. Five groups of simulation schemes were set for the new project of Daxi project of the Dayun River and the dispatching combination with four movable weir projects. Through the hydrodynamic mathematical model, the flow distribution of the river in the urban area under each scheme was simulated. Based on the field test, the effect of the recommended scheme was demonstrated. The results show that the recommended scheme has formed a smooth flow pattern of three-level water level difference, accurate water level regulation and reasonable flow distribution, and the water environment of the river network has improved significantly. At the same time, most of the water quality indicators are still in a good state within 16 days after the end of water diversion, but the water quality of some rivers has rebounded significantly. It is an effective way to improve the water environment of plain river network cities to carry out hydrodynamic regulation through the mathematical model. However, it is necessary to strengthen daily monitoring, reasonably determine the living water cycle according to the water quality changes, and carry out pollution source analysis for some abnormal water quality points, so as to ensure the long-term treatment of river network water environment.
2013, (6): 47-53.
[Abstract](1112) [PDF 1145KB](46)
2014, (3): 70-76.
[Abstract](3944) [PDF 1143KB](478)

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