Experimental Study On Mechanism Of Infiltration Of Superficial Soil-rock Mixture In Qinba Mountains

Qinba Mountain area is located in the border area between the southern region and the northern region of China.As one of the most active areas of the Chinese crust movement,in the long-term development and evolution process,Qinba Mountain has formed a large number of metamorphic rock residual slopes with shallow soil depth.In addition,Zhenba County is located in the middle of the Mountain area with abundant rainfall and heavy rains for many years.Under the combined effect of these two factors,a large number of shallow landslides are caused,which seriously threatens seriously threatening people's life and property safety.Therefore,it is urgent to study the rainfall law patterns,soil properties and infiltration laws.Based on the shallow surface soil-rock mixture landslide in Qinba Mountain Area under rainfall condition of the National Natural Science Foundation Project,In this paper,we choose Zhenba County in Qinba Mountain Area as the research area.Based on the geological investigation of Zhenba County,the systematical analysis of rainfall,and the foundation of the saturated and unsaturated permeation tests,this paper analyses the rainfall infiltration process and slope stability though the numerical simulation method.The main results of the paper are as follows:(1)According to the field investigation results and a large number of geological data,the geography and engineering geology of the study area are described.Through wavelet and MK verification,the rainfall patterns and mutation characteristics of the study area at different time scales are summarized,and the trend of the rainfall is predicted.Meanwhile,the paper provides a realistic rainfall environment for the simulation.(2)The physical and mechanical characteristics of the soil and characteristics of the large-size permeability were studied by indoor experiments.The permeability coefficient and particle gradation both satisfy the exponential function relationship under different void ratios,and the corresponding parameters of three different pore ratios are obtained.The effect of void ratio on infiltration was studied under the same level.The soil gradation and pore ratio of the soil in the study area were analyzed by geotechnical test.The surface porosity of the soil in the study area was about 0.8.(3)The unsaturation characteristics of the soil are explored.Through the TRIM test,the paper studyies the difference between curve of the drying and wetting process.It is concluded that the saturated water content and residual water content of the soil will decrease by the content of gravel increase and the pores increase.In addition,the wetting process has a significant hysteresis compared with the drying process.This phenomenon was analyzed and finally provided a reliable unsaturated suction and water content and permeation data for the simulation.(4)Using Geo-studio,the process of rainfall infiltration and the variation of stability under fluid-solid coupling were obtained.During the whole process of rainfall,the slope stability decreases significantly in the early stage of rainfall.As the number of rainfall increases,the lowering speed of slope stability tends to be stable.