Experimental And Simulation Study On Shear Characteristics Of Interface Between Soil-Rock Mixture And Structure

Soil-rock mixture is a special geological body between soil and rock mass,which is composed of high-strength block stone,low-strength fine-grained soil and pores.It is different from traditional soil mechanics and rock-soil mechanics due to its large difference in particle size and strength characteristics,and its mechanical properties are more complex.With good compaction performance,high filling density,natural pores for drainage,small subsidence deformation,and high bearing capacity,soil-rock mixture is a good filling material for high filling slope,and is widely used in engineering.With the construction of a large number of airports in the western mountain area,it is more and more common to build airports with earth-rock mixture as the filling material.However,in the construction of airports,examples of life and property safety being threatened due to slope instability are highlighted.Therefore,it is an important task to study the interaction between the soil-rock mixture filling material and the original foundation to prevent slope deformation and instability.Soil-rock-mixture by some engineering as the research object,in view of the earth-rock aggregate with the original foundation the important contact surface,which influence the stability of slope by indoor test and PFC simulation of two kinds of means,for earth-rock aggregate particle shape,surface roughness and normal stress of the three important factors in the research on the contact surface and the mechanical properties of soil-rock-mixture near the contact area of influence.The thickness of the interface layer and the position relation between the weak surface and the contact surface were explored by means of moving down the contact surface in the laboratory test.The regular shape of soil particles was simulated by PFC,and its influence on the thickness of the interface layer was studied by comparing the down-moving contact surface with the displacement method.According to the analysis of the test and simulation results,the following main results were obtained:(1)The shear strength of soil-rock mixture at the contact surface increases with the increase of the normal stress,and the stress-strain curve increases almost linearly.When the contact surface roughness is constant and the normal pressure increases from 200 kPa to 600 kPa,the shrinkage of soil-stone mixture gradually decreases,but when the normal pressure increases to 800 kPa,the shrinkage of soil-stone mixture increases.(2)The influence curve of contact surface roughness on the shear strength of soil-rock mixture is nonlinear.When the contact surface roughness changes fromsmooth to rough,the shear strength of soil-rock mixture at the contact surface gradually increases.When the roughness increases to a certain value,it has little influence on the shear strength of soil-rock mixture.When the normal stress is constant and the contact surface roughness increases,the shrinkage of soil-rock mixture will increase,but when the contact surface roughness increases and the influence on the shear strength of soil-rock mixture is small,the shrinkage will decrease.(3)There is a certain size relation between the peak and valley of the contact surface and the particle size of soil-rock mixture: when the median particle size is greater than or equal to the distance between the peak and valley of contact surface,the roughness has a strengthening effect on the shear strength of soil-rock mixture near the contact surface.When the median particle size is smaller than the peak and valley distance of the contact surface,the effect of roughness on the shear strength enhancement of the soil-rock mixture near the contact surface is weakened,and the weak surface may occur at the contact surface.(4)The shape of soil particles is an important factor affecting the thickness of interface layer.With the increase of the shape coefficient,the roundness and convulity of the soil particles increase,and the soil particles roll and climb when they break,so that their bite force decreases in the experimental simulation,and when they are pulled to a larger range of soil particles,their positions move,so that the thickness of the interface layer increases.(5)The two methods of structural plane method and displacement method are effective ways to obtain the thickness of interface layer.This paper has 34 figures,11 tables and 93 references.