Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the m...Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the mechanical and hydraulic behavior and the susceptibility to cause dam failure.However,limited by longevity shortages and special geographic environments,the material distribution characteristics and their formation mechanisms are difficult to observe in the field.Therefore,an experimental apparatus modeling a landslide dam was developed in this paper,designing three sampling methods with two valley states.The internal deposit characteristics,void ratio variation and relative content of the particle size range(PSR)were analyzed,and the mechanics of deposit structure were also delicately ascertained.The results indicate that granular material deposited in valley shows a structure of inverse grain size accumulation in both vertical and horizontal directions,exhibiting spatial variability of particle gradation and void ratio.The characteristic PSR decreases from 22-30 mm in the two-dimensional state to 10-14 mm in the threedimensional state.Vibration excitation and vibration sieve are the intrinsic mechanisms of granular flow segregation,intrinsically inducing the formation of inverse grading deposit structures.Consequently,spatial variability in size is mainly trig gered by segregation,whereas coarse particle content and deposition boundaries merely exacerbate the difference degree.展开更多
The hydropower sector is currently experiencing several technological developments.New technologies and practices are emerging to make hydropower more flexible and more sustainable.Novel materials have also been recen...The hydropower sector is currently experiencing several technological developments.New technologies and practices are emerging to make hydropower more flexible and more sustainable.Novel materials have also been recently developed to increase performance,durability,and reliability;however,no systematic discussions can be found in the literature.Therefore,in this paper,novel materials for hydropower applications are presented,and their performance,advantages,and limitations are discussed.For example,composites can reduce the weight of steel equipment by 50%to 80%,polymers and superhydrophobic materials can reduce head losses by 4%to 20%,and novel bearing materials can reduce bearing wear by 6%.These improvements determine higher efficiencies,longer life span,waste reduction,and maintenance needs,although the initial cost of some materials is not yet competitive with respect to the costs of traditional materials.The novel materials are described here based on the following categories:novel materials for turbines,dams and waterways,bearings,seals,and ocean hydropower.展开更多
In rockfill dam engineering,particle breakage of rockfill materials is one of the major factors resulting in dam settlement.In this study,one-dimensional compression tests on a series of coarse granular materials with...In rockfill dam engineering,particle breakage of rockfill materials is one of the major factors resulting in dam settlement.In this study,one-dimensional compression tests on a series of coarse granular materials with artificially-graded particle size distributions(PSDs)were carried out.The tests focused on understanding the role of initial PSDs in the dense packing density,compressibility and crushability of coarse granular materials.The effects of fractal dimension(D)and size polydispersity(θ)of PSDs were quantitatively analyzed.Two different loading stages were identified from the logarithms of the stress-strain relationships,with the turning point marked as the yield stress.A similar effect of initial PSDs was observed on the packing density and low-pressure modulus of coarse granular materials.The packing density and low-pressure modulus increased monotonically withθ,and their peak values were attained at a D value of approximately 2.2.However,there was no unique correspondence between the dense packing density and low-pressure modulus.The particle breakage was influenced differently by the initial PSDs,and it decreased with the values of D andθ.The emergence of the unique ultimate state was also identified from both the compression curves and PSDs of the samples after the tests.The potential implications of the test results in the design of both low and high rockfill dams were also demonstrated.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
Water samples from Daan Viljoen dam, Avis dam and Goreangab dam were collected and filtered with burlap, cotton and polyester. The water samples were analyzed for the presence of total coliform, Escherichia coli, hete...Water samples from Daan Viljoen dam, Avis dam and Goreangab dam were collected and filtered with burlap, cotton and polyester. The water samples were analyzed for the presence of total coliform, Escherichia coli, heterotrophic plate count (HPC), somatic coliphage, Clostridium perfringens, turbidity and conductivity. The bacteriological analysis was carried out by membrane filtration and pour plate techniques. The water from the three dams was found to contain high levels of microorganisms which indicated that it was not safe for human consumption. Turbidity was improved after filtration. Cotton filtered out the most microorganisms (p < 0.05) in all dams compared with the other two types of cloths.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
基金financial support from the National Natural Science Foundation of China(U2040221)the fund on basic scientific research project of nonprofit central research institutions(Y321001)。
文摘Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the mechanical and hydraulic behavior and the susceptibility to cause dam failure.However,limited by longevity shortages and special geographic environments,the material distribution characteristics and their formation mechanisms are difficult to observe in the field.Therefore,an experimental apparatus modeling a landslide dam was developed in this paper,designing three sampling methods with two valley states.The internal deposit characteristics,void ratio variation and relative content of the particle size range(PSR)were analyzed,and the mechanics of deposit structure were also delicately ascertained.The results indicate that granular material deposited in valley shows a structure of inverse grain size accumulation in both vertical and horizontal directions,exhibiting spatial variability of particle gradation and void ratio.The characteristic PSR decreases from 22-30 mm in the two-dimensional state to 10-14 mm in the threedimensional state.Vibration excitation and vibration sieve are the intrinsic mechanisms of granular flow segregation,intrinsically inducing the formation of inverse grading deposit structures.Consequently,spatial variability in size is mainly trig gered by segregation,whereas coarse particle content and deposition boundaries merely exacerbate the difference degree.
文摘The hydropower sector is currently experiencing several technological developments.New technologies and practices are emerging to make hydropower more flexible and more sustainable.Novel materials have also been recently developed to increase performance,durability,and reliability;however,no systematic discussions can be found in the literature.Therefore,in this paper,novel materials for hydropower applications are presented,and their performance,advantages,and limitations are discussed.For example,composites can reduce the weight of steel equipment by 50%to 80%,polymers and superhydrophobic materials can reduce head losses by 4%to 20%,and novel bearing materials can reduce bearing wear by 6%.These improvements determine higher efficiencies,longer life span,waste reduction,and maintenance needs,although the initial cost of some materials is not yet competitive with respect to the costs of traditional materials.The novel materials are described here based on the following categories:novel materials for turbines,dams and waterways,bearings,seals,and ocean hydropower.
基金supported by the National Natural Science Foundation of China(Grants No.52009036,U1765205,and 51979091)the Key Project of Water Conservancy Science and Technology in Jiangxi Province(Grant No.201921ZDKT13).
文摘In rockfill dam engineering,particle breakage of rockfill materials is one of the major factors resulting in dam settlement.In this study,one-dimensional compression tests on a series of coarse granular materials with artificially-graded particle size distributions(PSDs)were carried out.The tests focused on understanding the role of initial PSDs in the dense packing density,compressibility and crushability of coarse granular materials.The effects of fractal dimension(D)and size polydispersity(θ)of PSDs were quantitatively analyzed.Two different loading stages were identified from the logarithms of the stress-strain relationships,with the turning point marked as the yield stress.A similar effect of initial PSDs was observed on the packing density and low-pressure modulus of coarse granular materials.The packing density and low-pressure modulus increased monotonically withθ,and their peak values were attained at a D value of approximately 2.2.However,there was no unique correspondence between the dense packing density and low-pressure modulus.The particle breakage was influenced differently by the initial PSDs,and it decreased with the values of D andθ.The emergence of the unique ultimate state was also identified from both the compression curves and PSDs of the samples after the tests.The potential implications of the test results in the design of both low and high rockfill dams were also demonstrated.
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.
文摘Water samples from Daan Viljoen dam, Avis dam and Goreangab dam were collected and filtered with burlap, cotton and polyester. The water samples were analyzed for the presence of total coliform, Escherichia coli, heterotrophic plate count (HPC), somatic coliphage, Clostridium perfringens, turbidity and conductivity. The bacteriological analysis was carried out by membrane filtration and pour plate techniques. The water from the three dams was found to contain high levels of microorganisms which indicated that it was not safe for human consumption. Turbidity was improved after filtration. Cotton filtered out the most microorganisms (p < 0.05) in all dams compared with the other two types of cloths.
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.