Experimental Study On The Bank Collapses Character Of The High Fiood Plain In Side Of The Intake Towers Of Xiaolangdi Multipurpose Project

Reservoirs in sediment-laden rivers have some problems in sedimentation.Reservoirs in the Yellow River have serious problems in sedimentation.Under the condition that the reservoir runs throughout the years and the flow and sediment come from the upstream,sedimentation in longitudinal along stream direction have formed in reservoir,and the bed morphology of high flood plain with deep channel have formed in front of dam.When it happened to front of discharge structure,once sliding,it is faster and more rapid and more dangerous than sedimentation along upstream direction.It is obviously critical to prevent sliding in front of discharge structure.It is significant for us to select the appropriate methods and to research the slope stability of high flood plain with deep channel in front of discharge structure.The slope stability of the high flood plain with deep channel,it has an important influence on safe operation of discharge structure for hydro-junction.In this study,Xiaolangdi Multipurpose Project have been taken as an example,research on the slope stability of the high flood plain with deep channel in front of the intake towers、The status slope of the high flood plain with deep channel collapses under special condition of rapid drawdown and may take some measures for clean silt plug away.The study of such problems would have great significance for practical application and the river dynamics of theoretical development.Firstly,do experimental study on the physical properties of model sand of the anion exchange resins and the selection of model sand.Secondly,do the verification test that it use the physical modeling of the Xiaolangdi Reservoir.Thirdly,do experimental study on shedding and sand sluicing at different precipitation rate,on the basis of the bed morphology of high flood plain with deep channel,according to scheduling rules of Xiaolangdi Multipurpose Project in later sediment impoundment period application,and observe the slope stability of the high flood plain with deep channel in front of the intake towers and the condition of slipe slope,and would use application measure to prevente of silt plug.The study shows that under condition of rapid drawdown at the maximum rate of three meters an day in scope of the reservoir operation,the bank failure in front of the intake towers has occurred,especially in the left bank.The mean elevation of the siltation is 189 meters,Local siltation height is up to 8 meters.Then,do experimental study on the major cause of bank-collapsed(the bank failure)in front of the intake towers.The finding shows that the major cause is the drop of water level.Then,do experimental study on scouring after the silt plug.The finding shows that Most of the sand has been washed away,when the elevation of the siltation exceed the acceptable limits in Xiaolangdi Reservoir,a method is adopted that open the free flow tunnel firstly,and then open the orifice tunnel secondly,and then open the desilting tunnel finally.In order to further fine research the relationship between the slope stability of the high flood plain with deep channel and precipitation rate and sediment grain size.The author use large-scale flume which is 0.8 meters in width and1.0 meters in height,Therefore,to build a partial probability model of the high flood plain with deep channel.Do experimental study on the impact on the high flood plain stability under the condition of different failling rate of water level(0.3m/d、1m/d、4m/d and 7m/d)and median grain size(fine sediment、middle sediment and coarse sediment).The study shows that angle of repose of sediment and the balance angle of accumulation sand body under the water,and the bigger the particle size,and the bigger the balance angle of accumulation sand body under the water;Sliding process showed the same trends for accumulation sand body under condition of rapid drawdown,water slope and undersea slope of accumulation sand body distribute inconformity over time;The change of slope of middle sediment and coarse sediment under condition of rapid drawdown are not more obvious than fine sediment’s.Relatively speaking,fine sediment is the most unstable;Transversal sedimentation patterns finally after,it can be divided into three parts that climbed part,slope part and reverse slope part.its every part of relative length and relative angle have a piecewise functional relationship.The test results can not only enrich the content of model sand,and can put forward the law of slope collapse and its formation mechanism.Meanwhile,aiming at engineering problems,answers the relationship between the slope stability and precipitation rate and sediment grain size,and measures for clean silt plug away.