Study On The Stability Of Sand Sliding Slope Under Rainfall Infiltration

With the national attention to the traffic facilities in the western mountainous areas,various slope disasters are inevitable along the highway.As a common geological hazard in Tibet,sand sliding slope often collapses in rainy season,which seriously threatens traffic safety.Rainfall infiltration is one of the main factors inducing the movement of sand sliding slope.Rainfall changes the material composition and seepage field of sand sliding slope,and then affects the stability of sand sliding slope.It is of great significance to study the stability of sand sliding slope under rainfall infiltration for disaster prevention and control.In this paper,the sand sliding slope in Tibet is taken as the research object,and the change of material composition of sand slope under rainfall and the influence of rainfall intensity and rainfall duration on the seepage and stability of sand slope are analyzed.This paper mainly includes the following aspects.(1)Analysis and summary of related concepts of sand sliding slope.Based on the collection of relevant data and documents,this paper summarizes the components,formation conditions,physical characteristics,instability characteristics and formation factors of the sliding slope in Tibet.The sand sliding slope in Tibet is mainly a slope formed by the accumulation of sand particles formed by physicalweathering of granite.It mainly relies on internal friction to maintain self critical stability,with poor stability and large permeability coefficient.(2)The basic theory of rainfall infiltration and the derivation of stability model.The mechanical action and saturated unsaturated seepage field in the process of rainfall infiltration are analyzed,and the slope stability model under rainfall infiltration is deduced.Rainfall will change the shear strength parameters of the slope.In the process of rainfall,the change of matrix suction in the slope will lead to the change of shear strength,and then the change of safety factor.At last,Morgentern-price limit equilibrium method and calculation process are derived to solve the slope safety factor.(3)Analysis of material composition of sand slope under rainfall.Through the indoor rainfall simulation test,the seepage parameters and landslide characteristics of sand slopes with different grain groups during rainfall are analyzed.In the process of rainfall,sand slope adapts to the supply of rainwater by increasing drainage capacity,while the improvement of drainage capacity depends on the loss of sand slope particles and the change of slope shape.(4)Analysis of the change of seepage field under rainfall infiltration.Seep/w was used to analyze the variation of pore water pressure and volume water content in the downhill surface of rainfall intensity and rainfall duration.The rainfall intensity is the infiltration pressure ofrainwater,and the rainfall duration is the supply of rainwater.The larger the rainfall intensity is,the greater the seepage change of the slope surface is,and the longer the rainfall duration is,the greater the seepage change in the slope is.(5)Stability analysis of sand slope under rainfall infiltration.Slope /W is used to analyze the change of sand slope safety coefficient under rainfall intensity and rainfall duration.The greater the rainfall intensity is,the lower the safety factor of sand slope is.In a certain rainfall duration,the longer the rainfall duration is,the lower the safety factor is after the rain stops.If the rainfall duration is exceeded,the safety factor is basically unchanged after the rain stops.