Research For Loess Shear Surface Characteristics And Influencing Factors Of Shear Strength

Malan loess has a large deposition thickness due to its loose and porous texture,unique hydrological properties,and strong water sensitivity,and its overlapping sedimentary structure makes it more widely distributed and most closely related to various human engineering activities.This paper takes Q3 Malan loess under different initial conditions as the research object,and takes the influence factors of shear strength parameters,the characteristics of the stress-strain curve,the shear deformation characteristics of the loess specimen,the microevolution mechanism of the shear surface formation,and the contribution of the matrix suction to the shear strength For the research goals,the research is carried out with the help of a variety of test methods and test methods,the results are as follows:(1)By analyzing the shear strength parameters of Malan loess in different initial states,it was found that the cohesion decreased significantly with increasing initial water content and increased with increasing initial dry density.Further research found that at the initial dry density,with the change of the moisture content,the change of the internal friction angle is smaller;while at the same moisture content,the internal friction angle increases with the increase of the dry density.(2)With the help of scanning electron microscope,the evolution mechanism of the formation of the shear surface of loess was analyzed from different scales such as fine,microscopic and granular scales.On the fine scale,when the water content is small,the shear surface roughness is high,and the undulation frequency along the direction of shear displacement is more but the undulation amplitude is smaller,and the shear surface is more "steep";as the water content increases,the undulation frequency gradually becomes less but the undulation amplitude gradually increases,and the transition form of the alternating concave and convex is gradually changed from the abrupt change to the "steep".The transition form at the alternating concave and convex areas gradually transitioned from a "steep hill" to a convex "gentle slope" with a slow transition.On the micro particle scale,the viscous particle content of the shear surface increased before and after shearing,while the skeletal particles of the powder grade became more significantly oriented.(3)On the basis of the rapid determination method of the loess soil-water characteristic curve,by analyzing the function relationship between the moisture content in the soil-water characteristic curve and the matrix suction,combining the moisture content obtained by the direct shear test and the unsaturated loess shear strength parameters For the functional relationship between the two,an attempt was made to propose a formula for predicting the shear strength of the loess in the Lvliang area with the matrix suction as a variable.