A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed ma...A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed material, and variations in the dimension of bed forms. The model predicts the changes in the grain size distribution with the time and space during degradation process. The numerical model proposes that the armoring process in degrading channels does not depend only on hydraulic characteristics of the flow but also on variation in the grain size distribution of sediments on the bed. The model was applied and compared with the results obtained from experiments conducted in 24 m recirculating flume for two sizes of sand; a good agreement was found between observed and calculated values.展开更多
Clogging effect,as a new concept in geological engineering,is a phenomenon of permeability decreasing under seeping in reservoir dam foundation of the alluvial and diluvial deposits with deep and thick layer,coarse pa...Clogging effect,as a new concept in geological engineering,is a phenomenon of permeability decreasing under seeping in reservoir dam foundation of the alluvial and diluvial deposits with deep and thick layer,coarse particle and high permeability in mountains-gully rivers of Tibetan Plateau.A clogging infiltration instrument has been designed successfully and a series of simulation tests have been done.Based on large amounts of data,it is confirmed that the existence of the clogging effect and the law of infiltration clogging is found out.Three indexes are proposed such as "optimal size of particle","optimal size range of particle" and "characteristic pore",which are closely related with effect of infiltration clogging.The concept and results can offer a new idea to solve problems on anti-seepage of dam foundation in mountains-gully rivers environment and to study artificial clogging,meanwhile supplement of the concept of seepage deformation.展开更多
Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transp...Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transport equation that defines the movement of pollutants adsorbed on the bed materials in the active bed layer is established,on the basis of mass conservation law and continuum theory.The transport equation is coupled into the 1-D mathematical model to numerically investigate water pollution process due to the scour of the bed sediment adsorbing pollutants.Comparisons with the situation in which the dynamics of the active bed layer is not considered indicate that the periodical evolution of the bed layer plays an innegligible role in the pollution process due to sediment re-suspension.Furthermore,comparisons of the results with available experimental observations are presented,and fairly good agreement is obtained.展开更多
文摘A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed material, and variations in the dimension of bed forms. The model predicts the changes in the grain size distribution with the time and space during degradation process. The numerical model proposes that the armoring process in degrading channels does not depend only on hydraulic characteristics of the flow but also on variation in the grain size distribution of sediments on the bed. The model was applied and compared with the results obtained from experiments conducted in 24 m recirculating flume for two sizes of sand; a good agreement was found between observed and calculated values.
文摘Clogging effect,as a new concept in geological engineering,is a phenomenon of permeability decreasing under seeping in reservoir dam foundation of the alluvial and diluvial deposits with deep and thick layer,coarse particle and high permeability in mountains-gully rivers of Tibetan Plateau.A clogging infiltration instrument has been designed successfully and a series of simulation tests have been done.Based on large amounts of data,it is confirmed that the existence of the clogging effect and the law of infiltration clogging is found out.Three indexes are proposed such as "optimal size of particle","optimal size range of particle" and "characteristic pore",which are closely related with effect of infiltration clogging.The concept and results can offer a new idea to solve problems on anti-seepage of dam foundation in mountains-gully rivers environment and to study artificial clogging,meanwhile supplement of the concept of seepage deformation.
基金supported by the National Natural Science Foundation of China(Grant No.51109064)the State Key Program of National Science Foundation of China(Grant No.51239003)the National Basic Research Program of China("973"Project)(Grant No.2011CB403303)
文摘Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transport equation that defines the movement of pollutants adsorbed on the bed materials in the active bed layer is established,on the basis of mass conservation law and continuum theory.The transport equation is coupled into the 1-D mathematical model to numerically investigate water pollution process due to the scour of the bed sediment adsorbing pollutants.Comparisons with the situation in which the dynamics of the active bed layer is not considered indicate that the periodical evolution of the bed layer plays an innegligible role in the pollution process due to sediment re-suspension.Furthermore,comparisons of the results with available experimental observations are presented,and fairly good agreement is obtained.
