Experimental Study On The Bank Collapse On Account Of Slope Toe Erosion Ocurring In The Middle And Lower Reaches Of The Yangtze River

For a long time,bank collapse occurs frequently in the middle and lower reaches of the Yangtze river,which seriously threatens the safety of dikes and stability of channels.With extension of the strategy of Yangtze river economic belt,the population and resources along coasts are becoming intensive,as well as shipping.So it's particularly important to prevent frequent occurrence of bank collapse.In order to further explore the mechanism of bank collapse,studying bank collapse on account of slope toe erosion occurring in the middle and lower reaches of the Yangtze river has important meanings.After summarizing and analysing the specific features of bank collapse,which occurs frequently in some rivers in the middle and lower reaches of the Yangtze river,this rearch carries out experimental study of bank collapse under natural slope conditions,basing on theoretical analysis and physical test.This paper also describes the erosion evolution of the submerged slope and defines the slope toe areas.Then the research carries out experimental study of bank collapse with revetments.It compares and anlysis on different revetment structure(stone revetment and row body revetment),guarding width and main guarding areas(slope toe areas and slope foot areas),obtaining a kind of relatively economical,effective revetment form.The conclusions are as follows:1.The research of bank collapse under natural slope conditions shows that,crescent sand waves developes along the near surface of water during scouring,with ribbon sand waves connecting with them;Slope sediment transports from the near surface of water to the slope foot during bank collapse,along the deep trench of crescent sand wave;Slope toe areas shall be the crescent sand wave as a transport carrier with sustained longitudinal and crosswise transportation.2.The research of bank collapse with revetments indicates that under same current conditions,row body revetment becomes more suitable to protect a particular area comparing to the stone revetment;Under the same revetment structure and main guarding areas,it gets better guardian effects with the increasement of guarding width;Under the same revetment structure and guarding width,protecting the slope foot areas will get better guardian effects;Revtments are arranged since the near surface of water to the direction of slope toe with the width of two-thirds of underwater slope surface will be more economic and effective;However,slope break point occurs and movs up continuously with the row body revetment basing on the above arrangements,meanwhile it does not favor the revetment structure and threatens stability of bank slope.