Study On The Reactivation Law Of Landslide Induced By Rainfall In Weathered Mudstone Residual Soil

Rainfall is one of the important causes of landslide reactivation.In reality,many landslides are directly related to rainfall.Nowadays,how to reduce the influence of rainfall on the slope has been an important topic for scholars both at home and abroad,and the understanding of the mechanism of rainfall triggering slope instability will be of great help to slope protection.In this study,variation rule of pore water pressure,soil pressure and displacement in slope with weak interlayer under rainfall condition are investigated through both of laboratory model tests and numerical simulation.First of all,the formation of weathered mudstone residual soil is discussed,and the soil mechanics parameters are obtained by direct shear test,compaction test and liquid plastic limit test.Through the experiments,we can get that the cohesion of soil sample is 8.13 kPa and the internal friction angle is 9 degrees,the optimum moisture content of soil sample is18.3%and the maximum dry density is 1.65 g/cm~3,the liquid limit of soil sample is 0.313and the plastic limit is 0.203.Secondly,the laboratory model test shows that the horizontal soil pressure in the sliding zone will experience a process of first decreasing and then increasing,and the horizontal soil pressure under the sliding zone changes smaller.In the process of rainfall,the soil gets saturated gradually,and the pore water pressure in slope increases gradually and tends to be stable.The slope displacement increases gradually along with the rainfall,and tensile cracks are occurred in the slope and the slope failure happens when the tensile cracks increase.Finally,the numerical simulation results show that the slope failure process in numerical simulation is in good agreement with that in laboratory model test.With the rainfall continues,the factor of slope safety decreases gradually and tends to a stable value,and the soil on the surface of slope gets saturated first and then the saturated zone gradually extends to the interior.In the process of rainfall,the horizontal soil pressure in slope changes greatly,and the state of soil near the soft interlayer gradually changes from compression to tension failure.Weak interlayer inclination angle and interlayer soil strength have a great influence on slope stability,and when interlayer inclination angle is bigger and the strength of interlayer soil is smaller,the slope stability will be worse and the failure from surface damage to deep damage will develop more quickly.