Study On Shallow Landslide Stability Of Residual Soil Under Rainfall Condition

Landslide disaster is one of the most serious geological disasters in China.Soil slope is easy to cause landslides under the influence of major factors such as rainfall,thus causing a certain degree of economic losses,casualties and ecological damage.Taking a residual soil landslide in Xingguo County as an example,through field investigation,model test and numerical simulation,the stability influencing factors and mechanical characteristics of soil slope are studied.The main conclusions are as follows:（1）Landslides in Xingguo County are mainly small soil landslides with the thickness of landslide bodies less than 10m,belonging to shallow landslides,and the probability of landslide occurring in rainfall season is high.The natural density of shallow residual soil in the study area is 1.91g/cm³,the optimal water content is17.8%,and the saturation permeability coefficient is 4.42×10^-6m/s.（2）The changes of soil pressure,pore water pressure and slope deformation and failure of slope model test soil under the condition of rainfall intensity of 21mm/h and45mm/h were compared.With the increase of rainfall intensity,rainwater infiltration increased and soil weight increased,which led to greater changes in soil pressure,and the maximum variation amplitude during the test was 5.51k Pa.The response time of pore water pressure of slope with rainfall intensity of 45mm/h was 20～30min earlier than that with rainfall intensity of 21mm/h,and the fluctuation range of pore water pressure was larger,with the maximum variation amplitude of 6.66k Pa during the test.Under the condition of rainfall intensity of 21mm/h,the partial shallow sliding failure occurred,while under the condition of rainfall intensity of 45mm/h,the whole shallow sliding failure occurred.（3）During rainfall,the pore water pressure,volume water content,maximum shear stress,displacement and slope stability coefficient of shallow residual soil are easily affected by different rainfall conditions（rainfall intensity,rainfall duration and rainfall later period）.With the increase of rainfall duration or intensity,the pore water pressure,volume water content,maximum shear stress and displacement of shallow soil increased gradually,but the stability coefficient decreased gradually.（4）The pore water pressure and volume water content of the slope gradually recovered to the initial state after the continuous rainfall of 190mm/d for 5 days and10 days after the rain stopped,and the stability coefficient gradually slowly rose to1.047;The influence of cohesion on the stability coefficient of slope is less than that of internal friction Angle.The greater the cohesion and internal friction Angle,the better the slope stability.The higher the saturation permeability coefficient is,the stronger the permeability of shallow soil is and the worse the stability is.With the increase of rainfall duration,compared with the monitoring points with the same slope depth,the pore water pressure changes first in the monitoring points at the foot of the slope which are close to the groundwater level,followed by the monitoring points in the middle of the slope and the top of the slope.