Study On Physical And Mechanical Properties And Strength Parameters Of Sliding Zone Soil Of Gently Inclined Landslides In Southwest Red Bed Area

At present,most of the research contents on the slow-inclined landslides in the red bed area are concentrated on the landslide formation mechanism,starting criteria and numerical simulation.Among them,there are relatively few studies on the characteristics of the landslide soil,and the landslide is an important component of the landslide body.Obviously,the study of its material composition,mechanical strength characteristics from different perspectives enriches and develops the research contents of slow-sloping landslides in the red bed area.In addition,it also has very important practical significance for the evaluation and prevention of this type of landslide.The author takes the Meiguhe landslide and Leidashi landslide developed in the gentle dip rock layer in the southwest red bed area were taken as the research objects.Through laser particle size analysis,XRD diffraction analysis,XRF fluorescence spectrum analysis,physical property test,ring shear test and direct shear test To explore the material composition and mechanical strength characteristics of slip zone soil,back analysis of the strength parameters of slip zone soil was carried out by GEO-Studio numerical simulation software.In addition,on the basis of collecting the strength parameters of the landslide zone in the southwest red bed,the statistical analysis of the strength parameters of the landslide zone is carried out through SPSS mathematical analysis software and MATLAB numerical calculation software.The main conclusions of the paper are as follows:?1?According to the physical properties and particle gradation of the slip zone soil,the Meigu River and Leidashi landslide zone soils were named as gravel silty clay.The particle composition of the landslides in the two landslides is not different,and the gradation is good.The water content,liquid limit and plastic index of the landslides in the Leidashi landslide are significantly larger than those in the landslide in the Meigu River?2?The main mineral components of the soil in the Meigu River landslide zone are quartz,calcite,potash feldspar,plagioclase,illite,kaolinite and Yi-Mongolian mixed layer.The main mineral components of the landslide landslide soil in Leidashi are quartz,potash feldspar,plagioclase,calcite,kaolinite,dolomite,and pyrite.Two of the landslide landslide samples have higher clay mineral content than the landslide The clay mineral content on the sliding surface is the highest,and the feldspar content is the least.The clay minerals may be caused by the chemical weathering or dissolution of feldspar under the action of groundwater.The main element oxides of Meiguhe landslide and Leidashi landslide are mainly Si O₂,Al₂O₃,followed by Fe₂O₃,Ti O₂,K₂O,Mg O,Ca O,and a small amount of Na₂O,P₂O₅,Mn O.Among them,Si O₂ in the two landslides is opposite The content is lower than the sliding body,and the relative content of Si O₂ is between 40%and 50%.In addition,the total relative content of Si O₂and Al₂O₃ in the two landslides is consistent,ranging from 62.38%to 67.13%.?3?According to the results of the ring shear test,the peak shear stress and residual shear stress increase with the increase of normal stress under the same fine particle content.Under the same normal stress,the peak shear stress and residual shear stress decrease with the increase of fine particle content.Under lower normal stress,the peak shear stress and residual shear stress decrease slowly with the increase of fine particle content,which is approximately linearly related,and the decrease is only 2.32k Pa?6.98k Pa.Under high normal stress,the peak shear stress and residual shear stress decrease rapidly and then slowly with the increase of fine particle content,which is obviously non-linearly related,and the magnitude of the reduction of residual shear stress is weaker than the peak shear stress.The peak cohesive force increases first and then decreases with the increase of fine particle content.The peak internal friction angle,residual cohesive force and residual internal friction angle decrease with the increase of fine particle content.The residual cohesion and the residual internal friction angle have a good linear fitting effect with the fine particle content.The former has a linear positive correlation and the latter has a linear negative correlation.?4?According to the results of the direct shear test,the peak cohesion of the undisturbed saturated unconsolidated fast shear test is higher than that of the saturated consolidation repeated shear test,and the peak internal friction angle is lower than that of the saturated consolidation repeated shear test.The cohesive force of the undisturbed repeated shear test showed a trend of decreasing first and then increasing with the increase of the number of shears.The overall change was small and there was no obvious correlation.The cohesive force of the reshaped sample and the internal friction angle decrease with the increase of the number of shears,which is inversely related.By comparing the repeated shear test of the original sample with gravel above 2mm and the remodeled sample with gravel removed above 2mm,it is preferred to choose the reshaped sample of slip zone soil with gravel removed above 2mm to get a better residual strength.?5?It can be known from the back analysis of the soil parameters of Meiguhe landslide and Leidashi landslide that the multi-section combined with the Morgenstern-Price method in the limit equilibrium theory and the inverse calculation method based on the specific deformation signs of the landslide and the development stage can be better Find the average shear strength parameter that represents the entire sliding belt.?6?In the strength parameters of the landslide zone of the southwest red bed gentle slope landslide,the influencing factors of saturated residual cohesion are natural peak cohesion and saturated peak cohesion.The influencing factors of the saturated residual internal friction angle are the natural peak internal friction angle and the saturated peak internal friction angle.Through statistical analysis,multiple linear and nonlinear regression models of saturated residual intensity parameters and natural and saturated peak intensity parameters are established,and the calculation accuracy of multiple nonlinear regression models is higher.