Stability Analysis Of Expansive Soil Slope In Northern Hebei Province

This thesis takes expansive soil slope in northern Hebei as the research object to study the slope stability under the condition of rainfall.Firstly,the thesis investigates the bad geological condition of slope in the study area and compares and analyzes the advantages and disadvantages of common methods of slope stability analysis.Secondly,laboratory tests such as soil-water characteristic curve test,permeability test,shear strength test and anchor bolt drawing test are carried out to analyze the characteristics of expansive soil.Combined with the above experimental research data,based on the field support scheme,Midas GTS NX finite element analysis software was used to establish the numerical simulation model of expansive soil slope support in the northern Hebei region,and the slope stability analysis was carried out under the conditions of dead weight and rainfall.Through the above research,the following conclusions can be drawn:(1)Soil-water characteristic curve test shows that the soil-water characteristic curve of expansive soil in the northern Hebei region is a standard "S" shape,the intake value of the sample is about 100 k Pa,and the residual water content of the sample is about 13.4%.(2)The shear strength test shows that with the increase of initial water content,the shear strength increases first and then decreases,and reaches the peak value when the water content is 21%.When the overlying load is large,the friction between soil particles is increased due to the increase of load,so the shear strength of expansive soil is greatly improved.(3)The results of bolt drawing test show that the bolt drawing stress in soil layer increases with the increase of anchor solid axial strain,and the curve trend of the relationship is roughly the same under different confining pressures.There are two obvious inflection points in the stress-strain curve of the drawing test,and the stressstrain relationship curve can be divided into three stages: elastic stage,elastic-plastic stage and failure stage.(4)Midas GTS NX finite element analysis software was used to establish the numerical simulation model of expansive soil slope before and after support in northern Hebei Province.The slope stability of the slope before and after support was analyzed under the condition of self-weight.The settlement deformation and lateral deformation of anti-slide pile in the analysis results were compared with the test results,which showed that the model was accurate and reliable.Under the condition of continuous rainfall,rainfall infiltration analysis was conducted on the slope model.The results showed that,due to the low permeability coefficient of expansive soil,only part of the precipitation would penetrate into the expansive soil layer under the condition of continuous rainfall,affecting the moisture content and intensity of the soil,and most of the precipitation would be lost along the surface.Considering that the soil in the study area is unsaturated soil,The influence of matric suction and water content on soil strength should not be ignored.Therefore,based on the rainfall infiltration analysis results of 5d rainfall,the expansive soil layer of the two models before and after the support is divided into different areas according to different water content.Then,the slope model is established again,the strength parameters of expansive soil with different water content are set up,and the slope stability is analyzed before and after the support.