Study On Direct Shear Characteristics And Particle Crushing Characteristics Of Soil-Rock Mixture

Due to the vast territory and complicated geological conditions in China,naturally formed or artificially backfilled soil-rock-mixture slope can be seen with the occurrence of landslide,debris flow and other disasters under natural environment or human influence,which brings serious impact on national economic development and people's life and property safety.Therefore,it is of great theoretical and practical significance to study the stability of soil-rock mixture.Based on indoor physical experiments and the discrete element software PFC2 D in xuzhou region of earth-rock aggregate materials for research,get normal stress,content of stone,stone shape and particle size of the largest stone in xuzhou region shear properties and the effects of particle breakage characteristics of the soil,so as to provide important reference for earth-rock aggregate slope stability analysis.The research results are as follows:(1)Firstly,the shear characteristics and particle breakage characteristics of soil-rock mixtures with different normal pressures and different stone contents were obtained through large direct shear tests and numerical simulation tests.The results show that the normal pressure and rock content have important effects on the shear stress and shear displacement curves of the soil-rock mixture.When the normal pressure is constant and the stone content is 50%,the shear strength,cohesion and internal friction Angle of the soil-stone mixture are maximized.Compared with that before shear,the content of small particle in the sample increased,the content of large particle decreased,and the fluctuation of the content of medium particle changed.With the increase of the stone content,the particle breakage rate increased gradually,and the power function relationship was found between the two.With the increase of normal pressure,the particle breakage rate increases gradually.The movement and crushing state of particles can be directly observed in the numerical simulation.Therefore,according to the crushing characteristics and movement characteristics of particles,the influence law of normal pressure and stone content on shear zone in the direct shear test is obtained.With the increase of stone content,the shear fracture zone increases and the shear displacement zone decreases.With the increase of normal pressure,the shear fracture zone decreases and the shear displacement zone increases.(2)A multi-scale numerical model was established to study the influence of the shape and maximum particle size of block stone on the shear characteristics andparticle breakage characteristics of soil-rock mixture.The shape of block stone has little influence on the shear strength of soil-stone mixture.With the increase of the shape coefficient of block stone,the particle breakage rate decreased gradually.When the normal pressure is constant,the thickness of shear fracture zone decreases with the increase of shape coefficient.When the normal pressure is constant,when the shape coefficient of rock decreases from 0.829 to 0.546,the shear displacement zone of soil-rock mixture particles gradually increases,but when the shape coefficient of rock decreases from 0.546 to 0.437,the thickness of the shear displacement zone decreases.With the increase of the maximum particle size,the shear strength of the soil-rock mixture and the crushing rate of the particles increase gradually.When the maximum particle size of block stone was 70 mm,no obvious shear fracture zone appeared near the shear plane.When the maximum particle size of block stone was50 mm and 30 mm,the shear fracture zone appeared near the shear plane,which was more significant compared with that when the maximum particle size of block stone was 50 mm and the maximum particle size of block stone was 30 mm.When the normal pressure is constant,the thickness of shear displacement zone increases with the increase of the maximum particle size.There are 46 pictures,18 tables and 88 references in this paper.