Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environment...Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.展开更多
The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-...The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-debris flow events, it is imperative to quantitatively assess the volume of sediment volume captured by the cascade check dams and to monitor their impact on sediment dynamics. This study investigates the cascade check dams in Guanmenzi Gully, Beichuan County, Sichuan Province in Southwest China, surveying the reservoir topography of the dams on two occasions over a fiveyear period. The #3 closed-type dam, located in the upper upstream, the #2 closed-type dam, located in the middle stream(which was manually cleaned), and the beam dam, located in the downstream were all surveyed. A simplified yet accurate method was developed to estimate sediment volume within check dam reservoirs under complex topographic conditions. A combination of terrestrial surveys and Unmanned Aerial Vehicle(UAV) based surveys was employed, resulting in the acquisition of two high-resolution Digital Elevation Models(DEMs) at different temporal intervals. The utilization of DEMs of Difference(DoD) facilitated the quantification of terrain variations and the sediment transport. The following conclusions were obtained: firstly, it was found that the volume of sediment trapped in the reservoirs of #2 closed-type dam and #1 beam dam were almost the same, with #3 closed-type dam being the smallest. The validation of the results in conjunction with the geometric method demonstrated that the percentage error was less than 7%, proving the reliability of the results. In addition, an analysis of changes in the detailed topography of the reservoirs revealed that the sediment deposit occurred in areas distant from the structures, while erosion exhibited concentration in specific areas close to the dams. The percentage volume of sediment deposit was found to be significantly higher than that of erosion(all higher than 85%). Furthermore, the excessive sediment deposition reduces the storage capacity of closed-type check dams, whereas in the case of beam dams, the maximum erosion amount in the reservoir is 35.8 m^(3) and the percentage of the maximum erosion amount is 14.00%. This suggests that the self-cleaning of beam dam can effectively slow down the sediment deposition process. Finally, the current study proposes an expression for storage capacity composition and suggests that, in engineering practice, emphasis should be placed on maintenance programs that synergize manual cleaning and self-cleaning of open-type check dams. The conclusions may facilitate the refinement of maintenance strategies of cascade check dams, thereby effectively preventing and mitigating debris flows.展开更多
Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study i...Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.展开更多
The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Lon...The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.展开更多
Many concrete dams seriously suffer from long-term seepage dissolution,and the induced mechanical property deterioration of concrete may significantly affect the structural performance,especially the seismic safety.An...Many concrete dams seriously suffer from long-term seepage dissolution,and the induced mechanical property deterioration of concrete may significantly affect the structural performance,especially the seismic safety.An approach is presented in this paper to quantify the influence of seepage dissolution on seismic performance of concrete dams.To connect laboratory test with numerical simulation,dissolution tests are conducted for concrete specimens and using the cumulative relative leached calcium as an aging index,a deterioration model is established to predict the mechanical property of leached concrete in the first step.A coupled seepage-calcium dissolutionmigrationmodel containing two calculation modes is proposed to simulate the spatially non-uniformdeterioration of concrete dams.Based on the simulated state of a roller compacted concrete dam subjected to 100 years of seepage dissolution,seismic responses of the damare subsequently analyzed.During which the nonlinear cracking of concrete,the radiation damping of the far-field foundation is considered.Research results show that seepage dissolution will seriously weaken the seismic safety of concrete dams because of the dissolution-induced decrease of effective thickness of the dam body.The upstream surface,dam toe and gallery wall suffer from a large degree of dissolution,whereas it is minimal and basically the same inside the dam body,at a degree of 0.19%within 100 years.The horizontal displacements of dam crest under the design static load and fortification against earthquake increase by 6.9%and 21.9%,respectively,and the dissolution-induced seismic cracking leads to the failure of dam anti-seepage system.This study can provide engineers with a reference basis for reinforcement decision of old concrete dams.展开更多
The growth in computer processing power has made it possible to use time-consuming analysis methods such as incremental dynamic analysis（IDA） with higher accuracy in less time.In an IDA study,a series of earthquake ...The growth in computer processing power has made it possible to use time-consuming analysis methods such as incremental dynamic analysis（IDA） with higher accuracy in less time.In an IDA study,a series of earthquake records are applied to a structure at successively increasing intensity levels,which causes the structure to shift from the elastic state into the inelastic state and finally into collapse.In this way,the limit-states and capacity of a structure can be determined.In the present research,the IDA of a concrete gravity dam considering a nonlinear concrete behavior,and sliding planes within the dam body and at the dam-foundation interface,is performed.The influence of the friction angle and lift joint slope on the response parameters are investigated and the various limit-states of the dam are recognized.It is observed that by introducing a lift joint,the tensile damage can be avoided for the dam structure.The lift joint sliding is essentially independent of the base joint friction angle and the upper ligament over the inclined lift joint slides into the upstream direction in strong earthquakes.展开更多
A new technique of combining accretion by cyclone separator and scattertube for tailings dams was developed according to laboratory experiment, model experiment and spot experiment technology. Three tailings dams were...A new technique of combining accretion by cyclone separator and scattertube for tailings dams was developed according to laboratory experiment, model experiment and spot experiment technology. Three tailings dams were successfully constructed by the new technique. The results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailings dams prove that the new technique improves structure and stability of the dams and working conditions compared with the traditional technique. The thin layers of fine-grained soils are greatly reduced, fine tailings sand is solid to make the dam stable and seepage conditions are well improved; the immersing line of the dam descends. In addition, the stability and liquefaction resistance of tailings dams are strengthened remarkably. The interior stress is compressive stress, stress level of every element is less than 1.0 and safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailings dams is greater than 1.5 according to the analysis of seismic response by finite element method.展开更多
A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the t...A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the three-dimensional Reynoldsaveraged Navier-Stokes equations(RANS),the renormalization group(RNG)k-εturbulence model,suspended and bed load transport equations,and the instability discriminant formula of dam breach side slope,and the explicit finite volume method(FVM),a detailed numerical simulation model for calculating the hydro-morphodynamic characteristics of cascading dam breach process has been developed.The developed numerical model can simulate the breach hydrograph and the dam breach morphology evolution during the cascading failure process of landslide dams.A model test of the breaches of two cascading landslide dams has been used as the validation case.The comparison of the calculated and measured results indicates that the breach hydrograph and the breach morphology evolution process of the upstream and downstream dams are generally consistent with each other,and the relative errors of the key breaching parameters,i.e.,the peak breach flow and the time to peak of each dam,are less than±5%.Further,the comparison of the breach hydrographs of the upstream and downstream dams shows that there is an amplification effect of the breach flood on the cascading landslide dam failures.Three key parameters,i.e.,the distance between the upstream and the downstream dams,the river channel slope,and the downstream dam height,have been used to study the flood amplification effect.The parameter sensitivity analyses show that the peak breach flow at the downstream dam decreases with increasing distance between the upstream and the downstream dams,and the downstream dam height.Further,the peak breach flow at the downstream dam first increases and then decreases with steepening of the river channel slope.When the flood caused by the upstream dam failure flows to the downstream dam,it can produce a surge wave that overtops and erodes the dam crest,resulting in a lowering of the dam crest elevation.This has an impact on the failure occurrence time and the peak breach flow of the downstream dam.The influence of the surge wave on the downstream dam failure process is related to the volume of water that overtops the dam crest and the erosion characteristics of dam material.Moreover,the cascading failure case of the Xiaogangjian and Lower Xiaogangjian landslide dams has also been used as the representative case for validating the model.In comparisons of the calculated and measured breach hydrographs and final breach morphologies,the relative errors of the key dam breaching parameters are all within±10%,which verify the rationality of the model is applicable to real-world cases.Overall,the numerical model developed in this study can provide important technical support for the risk assessment and emergency treatment of failures of cascading landslide dams.展开更多
Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of t...Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of the contraction joint opening between the dam monoliths.For modeling of rock canyon,the discrete parameters are obtained based on a curve fitting, thus allowing the nonlinear dam system to be solved in the time domain.The earthquake uniform tree-field input at the dam-canyon interface is used.An engineering example is given to demonstrate the significant effects of the radiation damping on the structure response.展开更多
In this study,the behavior of Gavoshan dam was evaluated during construction and the first impounding.A two-dimensional（2D） numerical analysis was conducted based on a finite difference method on the largest cross-s...In this study,the behavior of Gavoshan dam was evaluated during construction and the first impounding.A two-dimensional（2D） numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back analysis.These evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical model.Following that,by comparing the results of the numerical analysis with the measured values,it is indicated that there is a proper consistency between these two values.Moreover,it was observed that the dam performance was suitable regarding the induced pore water pressure,the pore water pressure ratio r;,settlement,induced stresses,arching degree,and hydraulic fracturing probability during the construction and initial impounding periods.The results demonstrated that the maximum settlement of the core was 238 cm at the end of construction.In the following 6 years after construction（initial impounding and exploitation period）,the accumulative settlement of the dam was 270 cm.It is clear that 88% of the total settlement of the dam took place during dam construction.The reason is that the clay core was smashed in the wet side,i.e.the optimum moisture content.Whereas the average curving ratio was 0.64 during dam construction; at the end of the initial impounding,the maximum amount of curving ratio in the upstream was 0.81,and the minimum（critical） amount in the downstream was 0.52.It was also concluded that this dam is safe in comparison with the behaviors of other similar dams in the world.展开更多
In the present study a Genetic Programing model (GP) proposed for the prediction of relative crest settlement of concrete faced rock fill dams. To this end information of 30 large dams constructed in seven countries a...In the present study a Genetic Programing model (GP) proposed for the prediction of relative crest settlement of concrete faced rock fill dams. To this end information of 30 large dams constructed in seven countries across the world is gathered with their reported settlements. The results showed that the GP model is able to estimate the dam settlement properly based on four properties, void ratio of dam’s body (e), height (H), vertical deformation modulus (Ev) and shape factor (Sc) of the dam. For verification of the model applicability, obtained results compared with other research methods such as Clements’s formula and the finite element model. The comparison showed that in all cases the GP model led to be more accurate than those of performed in literature. Also a proper compatibility between the GP model and the finite element model was perceived.展开更多
The regional distribution of landslide dams can provide valuable insights into the interactions among various factors,including lithology,topography,climate,and fluvial landforms in tectonically active mountains.Himal...The regional distribution of landslide dams can provide valuable insights into the interactions among various factors,including lithology,topography,climate,and fluvial landforms in tectonically active mountains.Himalayan rivers are frequently impacted by large-scale landslide damming,which profoundly influence fluvial geomorphology.In this study,we identified 1652 landslide dams in four major rivers of Bhutan and its surrounding area by remote sensing interpretation.Notably,approximately 71%of these landslide dams are found in regions composed of quartzite or gneiss.Fault-related tectonic activity plays a significant role in governing the distribution of these landslide dams,as approximately 83%of the mapped landslide dams are found within a 10 km radius of the nearest fault.The majority of the identified landslide dams are situated in areas with relatively modest local relief,ranging from 227 m to 327 m.These dams tend to cluster in the tributaries,and the stream power of almost 95%of them is typically below 1×10^(6) kg m^(2) s^(-3).Our data,combining the erosion rate and kernel density map of the landslide dams,reveals that regions with high erosion rates do not consistently align with the major high-density distribution of landslide dams.It is shown that the distribution of landslide dams is strongly influenced by the valley form.In comparison to U-shaped valleys,V-shaped valleys exhibit a higher density of landslide dams.Intriguingly,we also find a positive correlation between the landslide-dam distribution density and the erosion rate only in relatively arid regions with mean annual rainfall less than 500 mm.Moreover,the length of the upstream reach protected by the knickpoint associated with both lithology and landslide damming is about three times longer than that protected by the knickpoint associated only with landslide damming.展开更多
A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation,...A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.展开更多
The construction of dams for intercepting and storing water has altered surface water distributions, landsea water exchanges, and the load response of the solid Earth. The lack of accurate estimation of reservoir prop...The construction of dams for intercepting and storing water has altered surface water distributions, landsea water exchanges, and the load response of the solid Earth. The lack of accurate estimation of reservoir properties through the land surface and hydrological models can lead to water storage simulation and extraction errors. This impact is particularly evident in many artificial reservoirs in China. The study aims to comprehensively assess the spatiotemporal distribution and trends of water storage in medium and large reservoirs(MLRs) in Chinese mainland during 1950-2016, and to investigate the gravity,displacement, and strain effects induced by the reservoir mass concentration using the load elasticity theory. In addition, the impoundment contributions of MLRs to the relative sea level changes were assessed using a sea-level equation. The results show impoundment increases in the MLRs during1950-2016, particularly in the Yangtze River(Changjiang) and southern basins, causing significant elastic load effects in the surrounding areas of the reservoirs and increasing the relative sea level in China's offshore. However, long-term groundwater estimation trends are overestimated and underestimated in the Yangtze River and southwestern basins, respectively, due to the neglect of the MLRs impacts or the uncertainty of the hydrological model's output(e.g., soil moisture, etc.). The construction of MLRs may reduce the water mass input from land to the ocean, thus slowing global sea level rise. The results of the impact of human activities on the regional water cycle provide important references and data support for improving the integration of hydrological models, evaluating Earth's viscoelastic responses under longterm reservoir storage, enhancing in-situ and satellite geodetic measurements, and identifying the main factors driving sea level changes.展开更多
The strict definition and logical description of the concept of structure stability and failure are presented. The criterion of structure stability is developed based on plastic complementary energy and its variation....The strict definition and logical description of the concept of structure stability and failure are presented. The criterion of structure stability is developed based on plastic complementary energy and its variation. It is presented that the principle of minimum plastic complementary energy is the combination of structure equilibrium, coordination condition of deformation and constitutive relationship. Based on the above arguments, the deformation reinforcement theory is developed. The structure global stability can be described by the relationship between the global degree of safety of structure and the plastic complementary energy. Correspondingly, the new idea is used in the evaluations of global stability, anchorage force of dam-toe, fracture of dam-heel and treatment of faults of high arch dams in China. The results show that the deformation reinforcement theory provides a uniform and practical theoretical framework and a valuable solution for the analysis of global stability, dam-heel cracking, dam-toe anchorage and reinforcement of faults of high arch dams and their foundations.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:42330719National Natural Science Foundation of China,Grant/Award Number:U2443228+1 种基金Power Construction Corporation of China,Grant/Award Number:DJ-ZDXM-2021-51China Institute of Water Resources and Hydropower Research,Grant/Award Number:GE121003A0042022。
文摘Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.
基金jointly funded by the National Key R&D Program of China (2024YFC3012705)the CAS Light of West China Program (Grant Recipient:Wanyu Zhao)+1 种基金the National Natural Science Foundation of China (Grant No.42201095)the Postdoctoral Research Project Special Funding of Sichuan (Grant No.TB2023028)。
文摘The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-debris flow events, it is imperative to quantitatively assess the volume of sediment volume captured by the cascade check dams and to monitor their impact on sediment dynamics. This study investigates the cascade check dams in Guanmenzi Gully, Beichuan County, Sichuan Province in Southwest China, surveying the reservoir topography of the dams on two occasions over a fiveyear period. The #3 closed-type dam, located in the upper upstream, the #2 closed-type dam, located in the middle stream(which was manually cleaned), and the beam dam, located in the downstream were all surveyed. A simplified yet accurate method was developed to estimate sediment volume within check dam reservoirs under complex topographic conditions. A combination of terrestrial surveys and Unmanned Aerial Vehicle(UAV) based surveys was employed, resulting in the acquisition of two high-resolution Digital Elevation Models(DEMs) at different temporal intervals. The utilization of DEMs of Difference(DoD) facilitated the quantification of terrain variations and the sediment transport. The following conclusions were obtained: firstly, it was found that the volume of sediment trapped in the reservoirs of #2 closed-type dam and #1 beam dam were almost the same, with #3 closed-type dam being the smallest. The validation of the results in conjunction with the geometric method demonstrated that the percentage error was less than 7%, proving the reliability of the results. In addition, an analysis of changes in the detailed topography of the reservoirs revealed that the sediment deposit occurred in areas distant from the structures, while erosion exhibited concentration in specific areas close to the dams. The percentage volume of sediment deposit was found to be significantly higher than that of erosion(all higher than 85%). Furthermore, the excessive sediment deposition reduces the storage capacity of closed-type check dams, whereas in the case of beam dams, the maximum erosion amount in the reservoir is 35.8 m^(3) and the percentage of the maximum erosion amount is 14.00%. This suggests that the self-cleaning of beam dam can effectively slow down the sediment deposition process. Finally, the current study proposes an expression for storage capacity composition and suggests that, in engineering practice, emphasis should be placed on maintenance programs that synergize manual cleaning and self-cleaning of open-type check dams. The conclusions may facilitate the refinement of maintenance strategies of cascade check dams, thereby effectively preventing and mitigating debris flows.
基金Special Scientific Found for Seismic Industry Under Grant No.201008005
文摘Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.
文摘The basic element in any sustainable dam project is safety, which includes the following safety elements： O structural safety, dam safety monitoring, operational safety and maintenance, and emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. How- ever, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be car- ried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that darn safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.
基金supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China(No.51321065)the Foundation for Key Program of Natural Science Foundation of High Arch Dam(No.51339003)the National Basic Research Program of China(‘‘973’’Program,No.2013CB035904)
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51709021,52079120)the project funded by China Postdoctoral Science Foundation(Grant No.2020M670387)the Belt and Road Special Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2019nkzd03).
文摘Many concrete dams seriously suffer from long-term seepage dissolution,and the induced mechanical property deterioration of concrete may significantly affect the structural performance,especially the seismic safety.An approach is presented in this paper to quantify the influence of seepage dissolution on seismic performance of concrete dams.To connect laboratory test with numerical simulation,dissolution tests are conducted for concrete specimens and using the cumulative relative leached calcium as an aging index,a deterioration model is established to predict the mechanical property of leached concrete in the first step.A coupled seepage-calcium dissolutionmigrationmodel containing two calculation modes is proposed to simulate the spatially non-uniformdeterioration of concrete dams.Based on the simulated state of a roller compacted concrete dam subjected to 100 years of seepage dissolution,seismic responses of the damare subsequently analyzed.During which the nonlinear cracking of concrete,the radiation damping of the far-field foundation is considered.Research results show that seepage dissolution will seriously weaken the seismic safety of concrete dams because of the dissolution-induced decrease of effective thickness of the dam body.The upstream surface,dam toe and gallery wall suffer from a large degree of dissolution,whereas it is minimal and basically the same inside the dam body,at a degree of 0.19%within 100 years.The horizontal displacements of dam crest under the design static load and fortification against earthquake increase by 6.9%and 21.9%,respectively,and the dissolution-induced seismic cracking leads to the failure of dam anti-seepage system.This study can provide engineers with a reference basis for reinforcement decision of old concrete dams.
文摘The growth in computer processing power has made it possible to use time-consuming analysis methods such as incremental dynamic analysis（IDA） with higher accuracy in less time.In an IDA study,a series of earthquake records are applied to a structure at successively increasing intensity levels,which causes the structure to shift from the elastic state into the inelastic state and finally into collapse.In this way,the limit-states and capacity of a structure can be determined.In the present research,the IDA of a concrete gravity dam considering a nonlinear concrete behavior,and sliding planes within the dam body and at the dam-foundation interface,is performed.The influence of the friction angle and lift joint slope on the response parameters are investigated and the various limit-states of the dam are recognized.It is observed that by introducing a lift joint,the tensile damage can be avoided for the dam structure.The lift joint sliding is essentially independent of the base joint friction angle and the upper ligament over the inclined lift joint slides into the upstream direction in strong earthquakes.
文摘A new technique of combining accretion by cyclone separator and scattertube for tailings dams was developed according to laboratory experiment, model experiment and spot experiment technology. Three tailings dams were successfully constructed by the new technique. The results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailings dams prove that the new technique improves structure and stability of the dams and working conditions compared with the traditional technique. The thin layers of fine-grained soils are greatly reduced, fine tailings sand is solid to make the dam stable and seepage conditions are well improved; the immersing line of the dam descends. In addition, the stability and liquefaction resistance of tailings dams are strengthened remarkably. The interior stress is compressive stress, stress level of every element is less than 1.0 and safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailings dams is greater than 1.5 according to the analysis of seismic response by finite element method.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U22A20602,U2040221).
文摘A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the three-dimensional Reynoldsaveraged Navier-Stokes equations(RANS),the renormalization group(RNG)k-εturbulence model,suspended and bed load transport equations,and the instability discriminant formula of dam breach side slope,and the explicit finite volume method(FVM),a detailed numerical simulation model for calculating the hydro-morphodynamic characteristics of cascading dam breach process has been developed.The developed numerical model can simulate the breach hydrograph and the dam breach morphology evolution during the cascading failure process of landslide dams.A model test of the breaches of two cascading landslide dams has been used as the validation case.The comparison of the calculated and measured results indicates that the breach hydrograph and the breach morphology evolution process of the upstream and downstream dams are generally consistent with each other,and the relative errors of the key breaching parameters,i.e.,the peak breach flow and the time to peak of each dam,are less than±5%.Further,the comparison of the breach hydrographs of the upstream and downstream dams shows that there is an amplification effect of the breach flood on the cascading landslide dam failures.Three key parameters,i.e.,the distance between the upstream and the downstream dams,the river channel slope,and the downstream dam height,have been used to study the flood amplification effect.The parameter sensitivity analyses show that the peak breach flow at the downstream dam decreases with increasing distance between the upstream and the downstream dams,and the downstream dam height.Further,the peak breach flow at the downstream dam first increases and then decreases with steepening of the river channel slope.When the flood caused by the upstream dam failure flows to the downstream dam,it can produce a surge wave that overtops and erodes the dam crest,resulting in a lowering of the dam crest elevation.This has an impact on the failure occurrence time and the peak breach flow of the downstream dam.The influence of the surge wave on the downstream dam failure process is related to the volume of water that overtops the dam crest and the erosion characteristics of dam material.Moreover,the cascading failure case of the Xiaogangjian and Lower Xiaogangjian landslide dams has also been used as the representative case for validating the model.In comparisons of the calculated and measured breach hydrographs and final breach morphologies,the relative errors of the key dam breaching parameters are all within±10%,which verify the rationality of the model is applicable to real-world cases.Overall,the numerical model developed in this study can provide important technical support for the risk assessment and emergency treatment of failures of cascading landslide dams.
文摘Effects of two important factors on earthquake response of high arch dams are considered and combined into one program.These tactors are:effects of radiation damping of the infinite canyon and local non-linearity of the contraction joint opening between the dam monoliths.For modeling of rock canyon,the discrete parameters are obtained based on a curve fitting, thus allowing the nonlinear dam system to be solved in the time domain.The earthquake uniform tree-field input at the dam-canyon interface is used.An engineering example is given to demonstrate the significant effects of the radiation damping on the structure response.
文摘In this study,the behavior of Gavoshan dam was evaluated during construction and the first impounding.A two-dimensional（2D） numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back analysis.These evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical model.Following that,by comparing the results of the numerical analysis with the measured values,it is indicated that there is a proper consistency between these two values.Moreover,it was observed that the dam performance was suitable regarding the induced pore water pressure,the pore water pressure ratio r;,settlement,induced stresses,arching degree,and hydraulic fracturing probability during the construction and initial impounding periods.The results demonstrated that the maximum settlement of the core was 238 cm at the end of construction.In the following 6 years after construction（initial impounding and exploitation period）,the accumulative settlement of the dam was 270 cm.It is clear that 88% of the total settlement of the dam took place during dam construction.The reason is that the clay core was smashed in the wet side,i.e.the optimum moisture content.Whereas the average curving ratio was 0.64 during dam construction; at the end of the initial impounding,the maximum amount of curving ratio in the upstream was 0.81,and the minimum（critical） amount in the downstream was 0.52.It was also concluded that this dam is safe in comparison with the behaviors of other similar dams in the world.
文摘In the present study a Genetic Programing model (GP) proposed for the prediction of relative crest settlement of concrete faced rock fill dams. To this end information of 30 large dams constructed in seven countries across the world is gathered with their reported settlements. The results showed that the GP model is able to estimate the dam settlement properly based on four properties, void ratio of dam’s body (e), height (H), vertical deformation modulus (Ev) and shape factor (Sc) of the dam. For verification of the model applicability, obtained results compared with other research methods such as Clements’s formula and the finite element model. The comparison showed that in all cases the GP model led to be more accurate than those of performed in literature. Also a proper compatibility between the GP model and the finite element model was perceived.
基金supported by the National Natural Science Foundation of China(Grant No.91747207)the National Key R&D Program of China(Grant No.2018YFC1505205)the National Natural Science Foundation of China(Grant No.41790434)。
文摘The regional distribution of landslide dams can provide valuable insights into the interactions among various factors,including lithology,topography,climate,and fluvial landforms in tectonically active mountains.Himalayan rivers are frequently impacted by large-scale landslide damming,which profoundly influence fluvial geomorphology.In this study,we identified 1652 landslide dams in four major rivers of Bhutan and its surrounding area by remote sensing interpretation.Notably,approximately 71%of these landslide dams are found in regions composed of quartzite or gneiss.Fault-related tectonic activity plays a significant role in governing the distribution of these landslide dams,as approximately 83%of the mapped landslide dams are found within a 10 km radius of the nearest fault.The majority of the identified landslide dams are situated in areas with relatively modest local relief,ranging from 227 m to 327 m.These dams tend to cluster in the tributaries,and the stream power of almost 95%of them is typically below 1×10^(6) kg m^(2) s^(-3).Our data,combining the erosion rate and kernel density map of the landslide dams,reveals that regions with high erosion rates do not consistently align with the major high-density distribution of landslide dams.It is shown that the distribution of landslide dams is strongly influenced by the valley form.In comparison to U-shaped valleys,V-shaped valleys exhibit a higher density of landslide dams.Intriguingly,we also find a positive correlation between the landslide-dam distribution density and the erosion rate only in relatively arid regions with mean annual rainfall less than 500 mm.Moreover,the length of the upstream reach protected by the knickpoint associated with both lithology and landslide damming is about three times longer than that protected by the knickpoint associated only with landslide damming.
文摘A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.
基金supported by the National Natural Science Foundation of China (No.42274110 and 42374106)long-term monitoring project in the Three Gorges Reservoir area (the National Natural Science Foundation of China,No.41874090 and 41504065)。
文摘The construction of dams for intercepting and storing water has altered surface water distributions, landsea water exchanges, and the load response of the solid Earth. The lack of accurate estimation of reservoir properties through the land surface and hydrological models can lead to water storage simulation and extraction errors. This impact is particularly evident in many artificial reservoirs in China. The study aims to comprehensively assess the spatiotemporal distribution and trends of water storage in medium and large reservoirs(MLRs) in Chinese mainland during 1950-2016, and to investigate the gravity,displacement, and strain effects induced by the reservoir mass concentration using the load elasticity theory. In addition, the impoundment contributions of MLRs to the relative sea level changes were assessed using a sea-level equation. The results show impoundment increases in the MLRs during1950-2016, particularly in the Yangtze River(Changjiang) and southern basins, causing significant elastic load effects in the surrounding areas of the reservoirs and increasing the relative sea level in China's offshore. However, long-term groundwater estimation trends are overestimated and underestimated in the Yangtze River and southwestern basins, respectively, due to the neglect of the MLRs impacts or the uncertainty of the hydrological model's output(e.g., soil moisture, etc.). The construction of MLRs may reduce the water mass input from land to the ocean, thus slowing global sea level rise. The results of the impact of human activities on the regional water cycle provide important references and data support for improving the integration of hydrological models, evaluating Earth's viscoelastic responses under longterm reservoir storage, enhancing in-situ and satellite geodetic measurements, and identifying the main factors driving sea level changes.
基金Supported by the China National Funds for Distinguished Young Scientists (50925931)the Special Funds for Major State Basic Research Projects (2009CB724604)
文摘The strict definition and logical description of the concept of structure stability and failure are presented. The criterion of structure stability is developed based on plastic complementary energy and its variation. It is presented that the principle of minimum plastic complementary energy is the combination of structure equilibrium, coordination condition of deformation and constitutive relationship. Based on the above arguments, the deformation reinforcement theory is developed. The structure global stability can be described by the relationship between the global degree of safety of structure and the plastic complementary energy. Correspondingly, the new idea is used in the evaluations of global stability, anchorage force of dam-toe, fracture of dam-heel and treatment of faults of high arch dams in China. The results show that the deformation reinforcement theory provides a uniform and practical theoretical framework and a valuable solution for the analysis of global stability, dam-heel cracking, dam-toe anchorage and reinforcement of faults of high arch dams and their foundations.
