The earth-rockfill dam is one of the primary dam types in the selection of high dams to be constructed in Western China, since it is characterized by favorable adaptability of the dam foundation; full utilization of l...The earth-rockfill dam is one of the primary dam types in the selection of high dams to be constructed in Western China, since it is characterized by favorable adaptability of the dam foundation; full utilization of local earth, rock, and building-excavated materials; low construction cost; and low cement consumption. Many major technical issues regarding earth-rockfill dams with a height of over 250 m were studied and solved successfully in the construction of the 261.5 m Nuozhadu earth core rockfill dam. This paper describes research achievements and basic conclusions; systematically summarizes the accumulated experiences from the construction of the Nuozhadu Dam and other high earth-rockfill dams; and discusses major technical issues, such as deformation control, seepage control, dam slope stability, safety and control of flood discharging, safety and quality control of dam construction, safety assessments, early warning, and other key technical difficulties. This study also provides a reference and technological support for the future construction of 300 m high earth-rockfill dams.展开更多
In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis c...In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis curve is also considered when the earth is under cyclic load. The research work can make the calculation results of plastic collapse more accurate by including the effect of the post-earthquake degree of plastic deformation on the stability of the earth-rock dam, and the dam safety factor decreases from 2.50 to 1.90 after the magnitude-8 earthquake. Moreover, the research work will also improve the design of the earth-rock dam under abnormal operating conditions.展开更多
During the construction of earth-rock dam,mutual exclusive construction goals such as quality,safety,progress and cost all have influences on each other,with risk factors being everchanging as the construction progres...During the construction of earth-rock dam,mutual exclusive construction goals such as quality,safety,progress and cost all have influences on each other,with risk factors being everchanging as the construction progresses.Accurate identification of the risk factors,as well as clearing any possible effect that any risk factors might have on the construction project is the key and foundation to our cooperative control of the construction goals.According to the construction planning of earth-rock dam,the hall3 D structure was used to identify the potential changes of risk factors,and the possible means of any risk factors to interfere with the construction goals.The dynamic risk assessment index system is established by deploying the WBS-RBS(work breakdown structurerisk breakdown structure)method,aiming at the construction goals of earth-rock dam.The case study shows that the index system is very effective at risk management of earth-rock dam during construction,and relatively practicable.展开更多
In order to accurately predict and control the aging process of dams, new information should be collected continuously to renew the quantitative evaluation of dam safety levels. Owing to the complex structural charact...In order to accurately predict and control the aging process of dams, new information should be collected continuously to renew the quantitative evaluation of dam safety levels. Owing to the complex structural characteristics of dams, it is quite difficult to predict the time-varying factors affecting their safety levels. It is not feasible to employ dynamic reliability indices to evaluate the actual safety levels of dams. Based on the relevant regulations for dam safety classification in China, a dynamic probability description of dam safety levels was developed. Using the Bayesian approach and effective information mining, as well as real-time information, this study achieved more rational evaluation and prediction of dam safety levels. With the Bayesian expression of discrete stochastic variables, the a priori probabilities of the dam safety levels determined by experts were combined wfth the likelihood probability of the real-time check information, and the probability information for the evaluation of dam safety levels was renewed. The probability index was then applied to dam rehabilitation decision-making. This method helps reduce the difficulty and uncertainty of the evaluation of dam safety levels and complies with the current safe decision-making regulations for dams in China. It also enhances the application of current risk analysis methods for dam safety levels.展开更多
Based on advanced computer technology, internet of things （lOT） technology, project management con- cept and professional technology and combined with the innovative theories, methods and techniques in earlier hy- d...Based on advanced computer technology, internet of things （lOT） technology, project management con- cept and professional technology and combined with the innovative theories, methods and techniques in earlier hy- dropower projects, the life-cycle risk management system of high earth-rock dam project for Nuozhadu project was developed. The system mainly includes digital dam, three-dimensional design, construction quality monito- ring, safety assessment and warning, etc, to integrally manage and analyze the dam design, constructional quality and safety monitoring information. It realized the dynamic updates of the comprehensive information and the safe- ty quality monitoring in the project life cycle, and provided the basic platform for the scientific management of the construction and operation safety of high earth-rock dam. Application in Nuozhadu earth-rock dam showed that construction safety monitoring and warning greatly helped accelerate the construction progress and improve project quality, and provided a new way for the quality safety control of high earth-rock dam.展开更多
When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by curre...When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines.However,these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability.Although their influence in a sliding plane has been thoroughly studied for direct shear,their influence under eccentric loading,as in the case of dams,is unknown.This paper presents the results of a parametric study that used finite element analysis(FEA)to investigate the influence of large-scale asperities on the load capacity of small buttress dams.By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material,transitions between different failure modes and correlations between the load capacity and the varied parameters were observed.The results indicated that the inclination of the asperity had a significant impact on the failure mode.When the inclinationwas 30and greater,interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity.When the asperity inclination was significant enough to provide interlocking,the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity.The location of the asperity along the concrete-rock interface did not affect the failure mode,except for when the asperity was located at the toe of the dam,but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding.By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam,a horizontal load capacity increase of 30%e160%was obtained,depending on the inclination and location of the asperity and the strength of the foundation material.展开更多
This study investigates the long-term performance of laboratory dam concrete in different curing environments over ten years and the microstructure of 17-year-old laboratory concrete and actual concrete cores drilled ...This study investigates the long-term performance of laboratory dam concrete in different curing environments over ten years and the microstructure of 17-year-old laboratory concrete and actual concrete cores drilled from the Three Gorges Dam.The mechanical properties of the laboratory dam concrete,whether cured in natural or standard environments,continued to improve over time.Furthermore,the laboratory dam concrete exhibited good resistance to diffusion and a refined microstructure after 17 years.However,curing and long-term exposure to the local natural environment reduced the frost resistance.Microstructural analyses of the laboratory concrete samples demonstrated that moderate-heat cement and fine fly ash(FA)particles were almost fully hydrated to form compact micro structures consisting of large quantities of homogeneous calcium(alumino)silicate hydrate(C-(A)-S-H)gels and a few crystals.No obvious interfacial transition zones were observed in the microstructure owing to the longterm pozzolanic reaction.This dense and homogenous microstructure was the crucial reason for the excellent long-term performance of the dam concrete.A high FA volume also played a significant role in the microstructural densification and performance growth of dam concrete at a later age.The concrete drilled from the dam surface exhibited a loose microstructure with higher microporosity,indicating that concrete directly exposed to the actual service environment suffered degradation caused by water and wind attacks.In this study,both macro-performance and microstructural analyses revealed that the application of moderate-heat cement and FA resulted in a dense and homogenous microstructure,which ensured the excellent long-term performance of concrete from the Three Gorges Dam after 17 years.Long-term exposure to an actual service environment may lead to microstructural degradation of the concrete surface.Therefore,the retained long-term dam concrete samples need to be further researched to better understand its microstructural evolution and development of its properties.展开更多
Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and ...Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams.A comprehensive analysis was conducted,focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China.Subsequently,the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored,including periodicity,convergence,and time-effect characteristics.These findings revealed the governing mechanism of main factors.Furthermore,a heterogeneous spatial panel vector model was developed,considering both common factors and specific factors affecting the safety and performance of arch dams.This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions,introducing a specific effect quantity to characterize local deformation differences.Ultimately,the proposed model was applied to the Xiaowan arch dam,accurately quantifying the spatiotemporal heterogeneity of dam performance.Additionally,the spatiotemporal distri-bution characteristics of environmental load effects on different parts of the dam were reasonably interpreted.Validation of the model prediction enhances its credibility,leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam.The findings not only enhance the predictive ability and timely control of ultrahigh arch dams'performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.展开更多
With the upgrading of modern mining technology, for the construction of water conservancy projects, the mining planning of the comprehensive material yard has a certain impact on the investment benefit of earth and ro...With the upgrading of modern mining technology, for the construction of water conservancy projects, the mining planning of the comprehensive material yard has a certain impact on the investment benefit of earth and rock dam. The relevant technical personnel need to plan the project scientifically and reasonably, and the project investment and project quality will be designed to require strict control. Based on this, this paper first expounds the selection principle of comprehensive material site, secondly, the comprehensive material site verification and mining planning are analyzed, and finally, from three aspects of investment mining planning, mining mode and operation scheme to explore the impact of comprehensive material site mining planning on earth-rock dam investment, for the reference of relevant personnel.展开更多
For a long time, our country has attached great importance to the construction of water conservancy projects and has built large, medium and small water conservancy reservoirs on a large scale throughout the country t...For a long time, our country has attached great importance to the construction of water conservancy projects and has built large, medium and small water conservancy reservoirs on a large scale throughout the country to solve the problems of flood control and drainage, agricultural irrigation and drinking water for people and livestock. In recent years, the party and government authorities at all levels have paid more attention to the operation safety of reservoirs. However, due to the gradual increase in the number of dangerous reservoirs and the limited investment of governments at all levels, how to effectively reinforce and remove the dangerous reservoirs and prevent seepage with limited resources has become an urgent problem to be solved. Based on this, it is necessary to study the management, reinforcement and anti-seepage schemes of small and medium-sized reservoir earth-rock dams, in order to provide some reference for the related work.展开更多
Proliferation of microalgae is the result of a complex interaction between hydrological and physico-chemical variables influenced by climatic and anthropogenic factors. This study assessed algal communities in the Sam...Proliferation of microalgae is the result of a complex interaction between hydrological and physico-chemical variables influenced by climatic and anthropogenic factors. This study assessed algal communities in the Samendeni Dam Lake to serve as indicators of water quality for sustainable management of hydro-agricultural water resources. Therefore, physico-chemical parameters and microalgae were monitored in three sampling zones from November 2021 to October 2022. A comparison of physico-chemical parameters was realized between sampling zones and between seasons. CCA and RDA were used to establish the relationship between parameters and microalgae. The results show 96 species belonging to 46 genera, 30 families, 19 orders, 9 classes, and 7 phyla. Charophyta dominated microalgal communities in both dry and rainy seasons. Phytoplankton species reached 34 in the dry season and 41 in the rainy season, whereas periphyton revealed 41 species in both seasons. Phytoplankton abundances ranged from 213 to 5440 cells·mL−1 and 3 to 110 cells·cm−2 for periphyton. At p < 0.05, significant correlation of Charophyta with pH (r = 0.39, p-value = 0.04), EC (r = −0.41 - 0.91, p-value = 0.00 - 0.03), Transp (r = 0.73, p-value = 0.03), Ammo (r = 0.48, p-value = 0.01), Nitra (r = 0.81, p-value = 0.01), Nitri (r = 0.91, p-value = 0.00) was observed. Bacillariophyta significantly correlated to pH (r = 0.70, p-value = 0.04), EC (r = −0.51 - 0.94, p-value = 0.00 - 0.04), DO (r = −0.70 - 0.81, p-value = 0.01 - 0.04), Transp (r = −0.71 - 0.73, p-value = 0.02 - 0.03), Nitra (r = 0.84, p-value = 0.00) and OrthoP (r = 0.44 - 0.73, p-value = 0.02 - 0.03). Chlorophyta was significantly correlated to EC (r = −0.41 - 0.95, p-value = 0.00 - 0.03), Transp (r = −0.52, p-value = 0.01), Nitra (r = 0.71, p-value = 0.03), Ammo (r = 0.42, p-value = 0.03). Cyanophyta showed significant correlation with pH (r = 0.43, p-value = 0.02);EC (r = 0.68, p-value = 0.04), Transp (r = −0.44, p-value = 0.02), OrthoP (r = 0.44 - 0.54, p-value = 0.00 - 0.02) and Ammo (r = 0.43, p-value = 0.02). Ochrophyta significantly correlated to Nitra (r = 0.42, p-value = 0.03). While Charophyta and Chlorophyta species in the dam lake indicate relatively good water quality, recorded harmful Cyanophyta species show a possible deterioration of the habitat. Therefore, continuous water quality monitoring since the construction of dam lakes should be performed for careful water management.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
The 2280 km long Jinsha River has been blocked at least four times in the past 30 years.A landslide dam-ming hazard chain can endanger communities and infrastructures hundreds of kilometers downstream from the damming...The 2280 km long Jinsha River has been blocked at least four times in the past 30 years.A landslide dam-ming hazard chain can endanger communities and infrastructures hundreds of kilometers downstream from the damming site in alpine gorges.Past damming events have resulted in severe consequences,demanding a thorough assessment of damming threats along the entire Jinsha River.This study digitizes the Jinsha River and visualizes its topographic,tectonic,hydrologic,and climate characteristics in detail.A two-stage full-probability method is proposed for assessing the damming threats along this river,mak-ing it possible to identify potential damming hotspots and high-priority zones for hazard mitigation.It is found that the upper reach of the Jinsha River poses the greatest damming threat,and the threat level gradually decreases downstream.Approximately 33.4%,36.7%,20.5%,and 9.4%of the entire length of the Jinsha River are classified as low,moderate,high,and very high threat levels,respectively.Compared with existing hydropower projects,future projects in the upper reach are more likely to be exposed to landslide damming.We highlight the value of basin-scale spatial threat analysis and envisage that our findings will promote more targeted local-scale risk assessments for potential damming hot-spots.These outcomes provide the basis for managing the risks of river damming and hydropower infras-tructure along the Jinsha River.展开更多
A physically-based numerical three-dimensional earthen dam piping failure model is developed for homogeneous and zoned soil dams.This model is an erosion model,coupled with force/moment equilibrium analyses.Orifice fl...A physically-based numerical three-dimensional earthen dam piping failure model is developed for homogeneous and zoned soil dams.This model is an erosion model,coupled with force/moment equilibrium analyses.Orifice flow and two-dimensional(2D)shallow water equations(SWE)are solved to simulate dam break flows at different breaching stages.Erosion rates of different soils with different construction compaction efforts are calculated using corresponding erosion formulae.The dam's real shape,soil properties,and surrounding area are programmed.Large outer 2D-SWE grids are used to control upstream and downstream hydraulic conditions and control the boundary conditions of orifice flow,and inner 2D-SWE flow is used to scour soil and perform force/moment equilibrium analyses.This model is validated using the European Commission IMPACT(Investigation of Extreme Flood Processes and Uncertainty)Test#5 in Norway,Teton Dam failure in Idaho,USA,and Quail Creek Dike failure in Utah,USA.All calculated peak outflows are within 10%errors of observed values.Simulation results show that,for a V-shaped dam like Teton Dam,a piping breach location at the abutment tends to result in a smaller peak breach outflow than the piping breach location at the dam's center;and if Teton Dam had broken from its center for internal erosion,a peak outflow of 117851 m'/s,which is 81%larger than the peak outflow of 65120 m3/s released from its right abutment,would have been released from Teton Dam.A lower piping inlet elevation tends to cause a faster/earlier piping breach than a higher piping inlet elevation.展开更多
文摘The earth-rockfill dam is one of the primary dam types in the selection of high dams to be constructed in Western China, since it is characterized by favorable adaptability of the dam foundation; full utilization of local earth, rock, and building-excavated materials; low construction cost; and low cement consumption. Many major technical issues regarding earth-rockfill dams with a height of over 250 m were studied and solved successfully in the construction of the 261.5 m Nuozhadu earth core rockfill dam. This paper describes research achievements and basic conclusions; systematically summarizes the accumulated experiences from the construction of the Nuozhadu Dam and other high earth-rockfill dams; and discusses major technical issues, such as deformation control, seepage control, dam slope stability, safety and control of flood discharging, safety and quality control of dam construction, safety assessments, early warning, and other key technical difficulties. This study also provides a reference and technological support for the future construction of 300 m high earth-rockfill dams.
文摘In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis curve is also considered when the earth is under cyclic load. The research work can make the calculation results of plastic collapse more accurate by including the effect of the post-earthquake degree of plastic deformation on the stability of the earth-rock dam, and the dam safety factor decreases from 2.50 to 1.90 after the magnitude-8 earthquake. Moreover, the research work will also improve the design of the earth-rock dam under abnormal operating conditions.
基金National Natural Science Foundation of China(No.51379192)
文摘During the construction of earth-rock dam,mutual exclusive construction goals such as quality,safety,progress and cost all have influences on each other,with risk factors being everchanging as the construction progresses.Accurate identification of the risk factors,as well as clearing any possible effect that any risk factors might have on the construction project is the key and foundation to our cooperative control of the construction goals.According to the construction planning of earth-rock dam,the hall3 D structure was used to identify the potential changes of risk factors,and the possible means of any risk factors to interfere with the construction goals.The dynamic risk assessment index system is established by deploying the WBS-RBS(work breakdown structurerisk breakdown structure)method,aiming at the construction goals of earth-rock dam.The case study shows that the index system is very effective at risk management of earth-rock dam during construction,and relatively practicable.
基金supported by the National Science and Technology Support Program of China (Program for the Eleventh Five-Year Plan, Grant No. 2006BAC14B03 and 2006BAC05B03)the National Natural Science Foundation of China (Grant No. 50679043)
文摘In order to accurately predict and control the aging process of dams, new information should be collected continuously to renew the quantitative evaluation of dam safety levels. Owing to the complex structural characteristics of dams, it is quite difficult to predict the time-varying factors affecting their safety levels. It is not feasible to employ dynamic reliability indices to evaluate the actual safety levels of dams. Based on the relevant regulations for dam safety classification in China, a dynamic probability description of dam safety levels was developed. Using the Bayesian approach and effective information mining, as well as real-time information, this study achieved more rational evaluation and prediction of dam safety levels. With the Bayesian expression of discrete stochastic variables, the a priori probabilities of the dam safety levels determined by experts were combined wfth the likelihood probability of the real-time check information, and the probability information for the evaluation of dam safety levels was renewed. The probability index was then applied to dam rehabilitation decision-making. This method helps reduce the difficulty and uncertainty of the evaluation of dam safety levels and complies with the current safe decision-making regulations for dams in China. It also enhances the application of current risk analysis methods for dam safety levels.
文摘Based on advanced computer technology, internet of things （lOT） technology, project management con- cept and professional technology and combined with the innovative theories, methods and techniques in earlier hy- dropower projects, the life-cycle risk management system of high earth-rock dam project for Nuozhadu project was developed. The system mainly includes digital dam, three-dimensional design, construction quality monito- ring, safety assessment and warning, etc, to integrally manage and analyze the dam design, constructional quality and safety monitoring information. It realized the dynamic updates of the comprehensive information and the safe- ty quality monitoring in the project life cycle, and provided the basic platform for the scientific management of the construction and operation safety of high earth-rock dam. Application in Nuozhadu earth-rock dam showed that construction safety monitoring and warning greatly helped accelerate the construction progress and improve project quality, and provided a new way for the quality safety control of high earth-rock dam.
基金the Research Council of Norway(Grant No.244029)the project‘Stable dams’,FORMAS(Grant No.2019e01236)+1 种基金the project‘Improved safety assessment of concrete dams’,and SVC(Grant No.VKU32019)the project‘Safe dams’,that supported the development of the research presented in this article.
文摘When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines.However,these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability.Although their influence in a sliding plane has been thoroughly studied for direct shear,their influence under eccentric loading,as in the case of dams,is unknown.This paper presents the results of a parametric study that used finite element analysis(FEA)to investigate the influence of large-scale asperities on the load capacity of small buttress dams.By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material,transitions between different failure modes and correlations between the load capacity and the varied parameters were observed.The results indicated that the inclination of the asperity had a significant impact on the failure mode.When the inclinationwas 30and greater,interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity.When the asperity inclination was significant enough to provide interlocking,the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity.The location of the asperity along the concrete-rock interface did not affect the failure mode,except for when the asperity was located at the toe of the dam,but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding.By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam,a horizontal load capacity increase of 30%e160%was obtained,depending on the inclination and location of the asperity and the strength of the foundation material.
基金the financial supports provided by the National Natural Science Foundation of China(U2040222,52293431,and 52278259)。
文摘This study investigates the long-term performance of laboratory dam concrete in different curing environments over ten years and the microstructure of 17-year-old laboratory concrete and actual concrete cores drilled from the Three Gorges Dam.The mechanical properties of the laboratory dam concrete,whether cured in natural or standard environments,continued to improve over time.Furthermore,the laboratory dam concrete exhibited good resistance to diffusion and a refined microstructure after 17 years.However,curing and long-term exposure to the local natural environment reduced the frost resistance.Microstructural analyses of the laboratory concrete samples demonstrated that moderate-heat cement and fine fly ash(FA)particles were almost fully hydrated to form compact micro structures consisting of large quantities of homogeneous calcium(alumino)silicate hydrate(C-(A)-S-H)gels and a few crystals.No obvious interfacial transition zones were observed in the microstructure owing to the longterm pozzolanic reaction.This dense and homogenous microstructure was the crucial reason for the excellent long-term performance of the dam concrete.A high FA volume also played a significant role in the microstructural densification and performance growth of dam concrete at a later age.The concrete drilled from the dam surface exhibited a loose microstructure with higher microporosity,indicating that concrete directly exposed to the actual service environment suffered degradation caused by water and wind attacks.In this study,both macro-performance and microstructural analyses revealed that the application of moderate-heat cement and FA resulted in a dense and homogenous microstructure,which ensured the excellent long-term performance of concrete from the Three Gorges Dam after 17 years.Long-term exposure to an actual service environment may lead to microstructural degradation of the concrete surface.Therefore,the retained long-term dam concrete samples need to be further researched to better understand its microstructural evolution and development of its properties.
基金supported by the National Natural Science Foundation of China(Grant No.52079046).
文摘Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams.A comprehensive analysis was conducted,focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China.Subsequently,the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored,including periodicity,convergence,and time-effect characteristics.These findings revealed the governing mechanism of main factors.Furthermore,a heterogeneous spatial panel vector model was developed,considering both common factors and specific factors affecting the safety and performance of arch dams.This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions,introducing a specific effect quantity to characterize local deformation differences.Ultimately,the proposed model was applied to the Xiaowan arch dam,accurately quantifying the spatiotemporal heterogeneity of dam performance.Additionally,the spatiotemporal distri-bution characteristics of environmental load effects on different parts of the dam were reasonably interpreted.Validation of the model prediction enhances its credibility,leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam.The findings not only enhance the predictive ability and timely control of ultrahigh arch dams'performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.
文摘With the upgrading of modern mining technology, for the construction of water conservancy projects, the mining planning of the comprehensive material yard has a certain impact on the investment benefit of earth and rock dam. The relevant technical personnel need to plan the project scientifically and reasonably, and the project investment and project quality will be designed to require strict control. Based on this, this paper first expounds the selection principle of comprehensive material site, secondly, the comprehensive material site verification and mining planning are analyzed, and finally, from three aspects of investment mining planning, mining mode and operation scheme to explore the impact of comprehensive material site mining planning on earth-rock dam investment, for the reference of relevant personnel.
文摘For a long time, our country has attached great importance to the construction of water conservancy projects and has built large, medium and small water conservancy reservoirs on a large scale throughout the country to solve the problems of flood control and drainage, agricultural irrigation and drinking water for people and livestock. In recent years, the party and government authorities at all levels have paid more attention to the operation safety of reservoirs. However, due to the gradual increase in the number of dangerous reservoirs and the limited investment of governments at all levels, how to effectively reinforce and remove the dangerous reservoirs and prevent seepage with limited resources has become an urgent problem to be solved. Based on this, it is necessary to study the management, reinforcement and anti-seepage schemes of small and medium-sized reservoir earth-rock dams, in order to provide some reference for the related work.
文摘Proliferation of microalgae is the result of a complex interaction between hydrological and physico-chemical variables influenced by climatic and anthropogenic factors. This study assessed algal communities in the Samendeni Dam Lake to serve as indicators of water quality for sustainable management of hydro-agricultural water resources. Therefore, physico-chemical parameters and microalgae were monitored in three sampling zones from November 2021 to October 2022. A comparison of physico-chemical parameters was realized between sampling zones and between seasons. CCA and RDA were used to establish the relationship between parameters and microalgae. The results show 96 species belonging to 46 genera, 30 families, 19 orders, 9 classes, and 7 phyla. Charophyta dominated microalgal communities in both dry and rainy seasons. Phytoplankton species reached 34 in the dry season and 41 in the rainy season, whereas periphyton revealed 41 species in both seasons. Phytoplankton abundances ranged from 213 to 5440 cells·mL−1 and 3 to 110 cells·cm−2 for periphyton. At p < 0.05, significant correlation of Charophyta with pH (r = 0.39, p-value = 0.04), EC (r = −0.41 - 0.91, p-value = 0.00 - 0.03), Transp (r = 0.73, p-value = 0.03), Ammo (r = 0.48, p-value = 0.01), Nitra (r = 0.81, p-value = 0.01), Nitri (r = 0.91, p-value = 0.00) was observed. Bacillariophyta significantly correlated to pH (r = 0.70, p-value = 0.04), EC (r = −0.51 - 0.94, p-value = 0.00 - 0.04), DO (r = −0.70 - 0.81, p-value = 0.01 - 0.04), Transp (r = −0.71 - 0.73, p-value = 0.02 - 0.03), Nitra (r = 0.84, p-value = 0.00) and OrthoP (r = 0.44 - 0.73, p-value = 0.02 - 0.03). Chlorophyta was significantly correlated to EC (r = −0.41 - 0.95, p-value = 0.00 - 0.03), Transp (r = −0.52, p-value = 0.01), Nitra (r = 0.71, p-value = 0.03), Ammo (r = 0.42, p-value = 0.03). Cyanophyta showed significant correlation with pH (r = 0.43, p-value = 0.02);EC (r = 0.68, p-value = 0.04), Transp (r = −0.44, p-value = 0.02), OrthoP (r = 0.44 - 0.54, p-value = 0.00 - 0.02) and Ammo (r = 0.43, p-value = 0.02). Ochrophyta significantly correlated to Nitra (r = 0.42, p-value = 0.03). While Charophyta and Chlorophyta species in the dam lake indicate relatively good water quality, recorded harmful Cyanophyta species show a possible deterioration of the habitat. Therefore, continuous water quality monitoring since the construction of dam lakes should be performed for careful water management.
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.
基金supported by the National Natural Science Foundation of China(41941017,U20A20112, 52025094)the Research Grants Council of the Hong Kong SAR Government(16203720)+1 种基金the NSFC/RGC Joint Research Scheme(N_HKUST620/20 and 42061160480)the Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone(HZQB-KCZYB-2020083).
文摘The 2280 km long Jinsha River has been blocked at least four times in the past 30 years.A landslide dam-ming hazard chain can endanger communities and infrastructures hundreds of kilometers downstream from the damming site in alpine gorges.Past damming events have resulted in severe consequences,demanding a thorough assessment of damming threats along the entire Jinsha River.This study digitizes the Jinsha River and visualizes its topographic,tectonic,hydrologic,and climate characteristics in detail.A two-stage full-probability method is proposed for assessing the damming threats along this river,mak-ing it possible to identify potential damming hotspots and high-priority zones for hazard mitigation.It is found that the upper reach of the Jinsha River poses the greatest damming threat,and the threat level gradually decreases downstream.Approximately 33.4%,36.7%,20.5%,and 9.4%of the entire length of the Jinsha River are classified as low,moderate,high,and very high threat levels,respectively.Compared with existing hydropower projects,future projects in the upper reach are more likely to be exposed to landslide damming.We highlight the value of basin-scale spatial threat analysis and envisage that our findings will promote more targeted local-scale risk assessments for potential damming hot-spots.These outcomes provide the basis for managing the risks of river damming and hydropower infras-tructure along the Jinsha River.
文摘A physically-based numerical three-dimensional earthen dam piping failure model is developed for homogeneous and zoned soil dams.This model is an erosion model,coupled with force/moment equilibrium analyses.Orifice flow and two-dimensional(2D)shallow water equations(SWE)are solved to simulate dam break flows at different breaching stages.Erosion rates of different soils with different construction compaction efforts are calculated using corresponding erosion formulae.The dam's real shape,soil properties,and surrounding area are programmed.Large outer 2D-SWE grids are used to control upstream and downstream hydraulic conditions and control the boundary conditions of orifice flow,and inner 2D-SWE flow is used to scour soil and perform force/moment equilibrium analyses.This model is validated using the European Commission IMPACT(Investigation of Extreme Flood Processes and Uncertainty)Test#5 in Norway,Teton Dam failure in Idaho,USA,and Quail Creek Dike failure in Utah,USA.All calculated peak outflows are within 10%errors of observed values.Simulation results show that,for a V-shaped dam like Teton Dam,a piping breach location at the abutment tends to result in a smaller peak breach outflow than the piping breach location at the dam's center;and if Teton Dam had broken from its center for internal erosion,a peak outflow of 117851 m'/s,which is 81%larger than the peak outflow of 65120 m3/s released from its right abutment,would have been released from Teton Dam.A lower piping inlet elevation tends to cause a faster/earlier piping breach than a higher piping inlet elevation.
