Study On The Relationship Between Paleosol Microstructure And The Stability Of Qiansuoya Landslide In Baota District,Yan’an

Loess landslide is very common along the weak paleosol layer,which is very serious.The study of the relationship between the microstructure of the soil and the stability of the slope is significant in view of the changes in the microscopic structure of the sliding surface of the paleosol.In this paper,the soil soil mass in the middle lock slope landslide in front of pagoda District of Yanan city is studied.The cyclic shear and scanning electron microscope tests are carried out to analyze the shear strength characteristics of the paleosol and the change of the microstructure parameters under different test conditions and the relationship between them,and explore the stability of the different failure modes of the paleosol microstructure to the stability of the slope.The influence.The main conclusions are as follows:(1)The range of peak intensity difference under different shear rates is 3kPa～5kPa,and the difference range of residual strength at different shear rates is 2kPa～7kPa.The effect of shear rate on shear strength of ancient soil is small,and the effect of effective normal stress and water content on the shear strength of ancient soil is significant,and the effect is opposite.When the stress increases,the peak strength and residual strength increase,while the peak strength and residual strength decrease with increasing moisture content.(2)The pore morphology and arrangement characteristics after shearing are more regular and orderly,and the orientation is more significant.With the increase of the effective normal stress,the directional frequency of the pores increases,the average diameter,abundance,the mean shape coefficient,the fractal dimension of the shape distribution,the directional probability entropy and the directional fractal dimension decrease,and when the water content increases,the average value increases.The diameter,the average shape coefficient and the directional frequency increase.The fractal dimension,the directional probability entropy and the directional fractal dimension decrease,and the abundance is irregular.(3)In the microstructure parameters of the paleosol,the cohesion and the directional frequency are the best,the correlation degree is 0.685,the correlation of the average shape coefficient is the worst,the correlation degree is 0.607,the correlation of the internal friction angle and the morphological distribution is the best,the correlation degree is 0.716,the correlation of the average straight diameter is the worst,and the correlation degree is 0.566.The cohesive force and internal friction angle are negatively correlated with the average shape coefficient,the average abundance,the average diameter and the directional frequency,which are positively related to the fractal dimension,the directional probability entropy and the directional fractal dimension.(4)Through the analysis of the conventional failure mode and the ultimate failure mode of the microstructure of the paleosol,the microstructure of the paleosol is lower in the stability of the slope,which is more favorable to the sliding of the slope,and has a greater impact on the stability of the slope.