PARTICLE DISCRETE ELEMENT NUMERICAL STUDY ON FACTORS OF SHEAR STRENGTH CHARACTERISTICS FOR SOIL-ROCK MIXTURE

The shear characteristics of soil-rock mixture(S-RM)control the stability of the high fill slope. The special structure,material and particle size composition of soil-rock mixture are extremely complicated. This paper explores the influencing factors and laws of shear properties of soil-rock mixture on the basis of laboratory experiments. It constructs the particle discrete element numerical models with PFC^2D to study the influence of particle gradation,initial porosity,rock size and rock shape on the shear characteristics of soil-rock mixture. The results shows that: the shear stress-shear displacement curves of soil-rock mixture can be divided into four phases including elastic,local shear,shear failure and residual deformation. The rock shape,particle gradation and initial porosity have no significant influence on the failure mode of soil-rock mixture,and the failure mode is strain softening. When the particle gradation of soil-rock mixture is poor,the shear stress fluctuates largely with the raising of shear displacement,and the curve shows obvious"jump" phenomenon. When the rock content is constant,under the same normal stress condition,the larger the stone size,the larger the shear strength of the S-RM. As the normal stress increases,the difference in shear strength between the test groups of different rock sizes increases,and the effect of rock size on the shear strength of soil-rock mixture is more obvious.