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
Since the filling of the reservoir of the Three Gorges Project(TGP)dam in the Yangtze River in 2003,erosion downstream from the dam site has affected the finless porpoise’s habitat.In this study,a one-dimensional(1D)...Since the filling of the reservoir of the Three Gorges Project(TGP)dam in the Yangtze River in 2003,erosion downstream from the dam site has affected the finless porpoise’s habitat.In this study,a one-dimensional(1D)fluvial process mathematical model is used to calculate flow and sediment transport in the middle and lower reaches of the Yangtze River,including the finless porpoise’s habitat.By analyzing the calculation results for the water resources,suspended load,and bed materials in the finless porpoise’s habitat after the riverbed deformation,we evaluated the possible impact on this rare Yangtze River aquatic animal.The results show that,with the erosion of riverbed over the next 20 years,the water quantity comprising the habitat will decrease to half of its present amount,and the bed materials will be eroded to coarse grading,such that the reserve will become a gradually disappearing stream.Effective engineering measures should be used to decrease the erosion in the main channel,in case the overall erosion cannot be stemmed and controlled,to ensure an adequate water volume flows into the finless porpoise’s habitat.展开更多
River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects （TGP） has started to become apparent： （1） reduction in f...River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects （TGP） has started to become apparent： （1） reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average; （2） in 2003-2014 the d 〉 0.125 mm （coarse sand） load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008-2014 was less than during 2003-2007; （3） after TGP im- poundment, there was some restoration in d 〈 0.125 mm （fine sand） sediment load, however, it was {ower than the pre-impoundment average; （4） due to riverbed compensation, the d 〉 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400x104 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d 〈 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened; （5） during 2003-2007 and 2008-2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion,lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003-2007, and coarse and fine erosion in 2008-2014. This difference was controlled by flood duration and number at Luoshan Station.展开更多
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.51139003)
文摘Since the filling of the reservoir of the Three Gorges Project(TGP)dam in the Yangtze River in 2003,erosion downstream from the dam site has affected the finless porpoise’s habitat.In this study,a one-dimensional(1D)fluvial process mathematical model is used to calculate flow and sediment transport in the middle and lower reaches of the Yangtze River,including the finless porpoise’s habitat.By analyzing the calculation results for the water resources,suspended load,and bed materials in the finless porpoise’s habitat after the riverbed deformation,we evaluated the possible impact on this rare Yangtze River aquatic animal.The results show that,with the erosion of riverbed over the next 20 years,the water quantity comprising the habitat will decrease to half of its present amount,and the bed materials will be eroded to coarse grading,such that the reserve will become a gradually disappearing stream.Effective engineering measures should be used to decrease the erosion in the main channel,in case the overall erosion cannot be stemmed and controlled,to ensure an adequate water volume flows into the finless porpoise’s habitat.
基金National Natural Science Foundation of China,No.51479146,No.51579123,No.51509012Fundamental Research Funds for Central Welfare Research Institutes,No.TKS160103+2 种基金No.TKS150102The National Key Research&Development Programs,No.2013BAB12B01National Key Research Program of China,No.2016YFC0402106
文摘River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects （TGP） has started to become apparent： （1） reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average; （2） in 2003-2014 the d 〉 0.125 mm （coarse sand） load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008-2014 was less than during 2003-2007; （3） after TGP im- poundment, there was some restoration in d 〈 0.125 mm （fine sand） sediment load, however, it was {ower than the pre-impoundment average; （4） due to riverbed compensation, the d 〉 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400x104 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d 〈 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened; （5） during 2003-2007 and 2008-2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion,lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003-2007, and coarse and fine erosion in 2008-2014. This difference was controlled by flood duration and number at Luoshan Station.
