Influence Factor Study Of Internal Stability Of Silty Clay Containing Rock Fragments Under Rainfall Infiltration

Distribution region feature investigation of one loose deposit negectling the effect of water table in Li Ping village Kangle town Fengjie county after heavy rainfall on 31 August 2015 point out that,there is large difference between deformation orientation of cracks and principal direction of landslide and distinct splayed crack on some wall of buildings.While researching discipline of deforemation of loose deposit under rainfall,it is necessary to consider not only slip induced by coupled deformation of solid-fluid filed under rainfall,but also settlement deformation induced by fine grain erosion because of its strong permeability and high porosity.In order to investigate influence factor of internal stability of loose deposit under rainfall,a new seepage erosion expertimental device has been developed,a experimental scheme separating solid grain and fluid from mixing erosion fluid has been made.Experimental material gotten from landslide site has been used to reconstruct specimens whose propertities including porosity,gradation,and soil-rock mixture ratio are different,with the new developed experimental device and experimental scheme these specimens are suffered seepage erosion,conclusions are summuarized as follows:(1)New developed simple seepage erosion apparatus can effectively simulate potential erosion process of soil under rainfall,experimental scheme separating soil grain and fluid from mixing effluent can reveal change of hydraulic gradient,rate of erosion clayey grain,rate of erosion solid grain,rate of outflow.(2)Intact erosion destruction can be segmented as 4 period,that is initiation period of erosion,stably developing period,acceleratlely destructing period,and there are distinct features among these periods.There are 3 critical hydraulic gradient during the development of hydraulic gradient,that is erosion initiation critical hydraulic gradient,skeleton deformation hydraulic gradient and erosion halt hydraulic gradient.(3)Two critical factor triggering loose deposit internal erosion are hydraulic shear stress and size of pore construction,only when hydraulic shear stress actted on grains exceed critical hydraulic shear stress and size of eroded grains is smaller than size of pore construction,internal erosion will be triggered;compared with critical hydraulic gradient critical hydraulic shear stress taking porosity and permeability of soil into account could be deemed as more appropriate index.(4)Compared with gap gradation specimens,continuous gradation specimens have higher degree of internal stability;Compared with Kenney&Lau criteria and Burenkova criteria,Kezdi criteria which is proposed based on Terzaghi filter ration could evaluate internal stability of loose deposit more reasonably.(5)30% and 70% could be acted as threshold percentage by weight of fine particles to classify mixtures as coarse grain supported structure,coarse-fine grain supported structure and fine grain supported structure,basic framework structure of soil determines shear strength,shear strength parameter,and hydraulic parameters of mixture.Compared with other types of basic framework structure,degree of internal stability of coarse-fine grain supported structure is lowest.