Research On Fluid-solid Coupling Analysis Of Granite Residual Soil Slope Stability

Granite residual soil is widely developed in southern China,especially in Guangzhou,and its physical and mechanical properties deteriorate obviously when it meets with water,so it is prone to landslide and other disasters under rainfall.In recent years,slope engineering has developed rapidly,it is generally faced with the problem of scientific and safe construction and economic and reasonable construction in granite residual soil slope.Granite residual soil is a special regional soil,which is mainly composed of granite residual soil.The engineering properties of granite residual soil are special.It has the characteristics of "two high and two low",high strength,high void ratio,low compressibility and low density.Because this type of soil slope is rich in weathering cracks,it also has bad mechanical properties such as easy to disturb,soften and collapse in water.This paper studies the stability of granite residual soil high and steep slope under rainfall,taking a landslide accident in Zhongshan City as an example.Based on COMSOL multiphysics,a numerical model of granite residual soil slope failure under fluid structure interaction is established to study the deformation and failure mechanism of granite residual soil slope under rainfall.In order to study the long-term stability of granite residual soil slope,COMSOL multi field coupling numerical model and Lizheng finite element model are established.The main research contents and conclusions are as follows:(1)The stability analysis of granite residual soil slope under natural conditions is analyzed.When the slope is not penetrated by rainfall,the stress field and deformation state of the slope are analyzed.After modeling,the analysis shows that: under natural conditions,without rainwater infiltration,the slope can still maintain its own stability,without large-area landslide;granite residual soil itself has a certain strength before meeting water,and the internal friction angle and cohesion are enough,so that the slope has a certain stability.(2)Under natural conditions,the center of the most disadvantageous slip surface is approximately 8M and 60 m in front of the foot of the slope,and the slip radius is about 59 m,and the slip surface passes through four layers of soil,the slip radius is about 45 m,the slip surface passes through three layers of soil,and the tangential force,tangential stress,normal force and normal stress of the most disadvantageous slip surface reach the maximum near the middle of the potential slip surface.(3)According to the simulation results,the shape of the landslide is arc,and the height of the sliding range measured in the model is about 8m to 32m;the sliding position of the model is close to the actual situation;The simulation results show that the width of the landslide accumulation is about 5m and the height is about 13m;the thickness of the landslide is about 4m;the sliding duration of the landslide is about 2.8s,and then the whole slope is basically stable;the sliding time is about 2.8s After completion,only part of the area is still unstable,and the specific location is at the edge of the slope top.Therefore,attention must be paid to prevent secondary sliding(or collapse)at the edge of the slope top when supporting.(4)The results of multi field physical field coupling numerical simulation in the analysis of the stability of granite residual soil slope,the main influence area of rainfall factors,slope sliding and other aspects are basically consistent with the actual situation of the project,which can better simulate the occurrence process of granite residual soil slope sliding under rainfall.