From the study of the particle size boundary

rock distribution and particle frequency

a three-dimensional（3D） stochastic model of soil-rock mixture is generated by using the direct method.A set of relatively complete and easily operational method is developed for building the 3D stochastic model.Moreover

a finite-difference model is established with the same distribution as natural soil-rock mixture by combining the newly developed building method and FLAC

3D

random modeling method.Then

direct shear tests and its numerical simulations are performed to obtain shear stress-displacement curves under different vertical pressures

which is f

urther applied to explore shear failure characteristics of soil-rock mixture and the interaction mechanism between soil and rock.Due to different levels of shear deformation of soil and the horizontal or rotational motion of stone under the friction action

the shear band of soil-rock mixture shows obviously irregular and discontinuous features in the shear process

and the shear stress-displacement curve exhibits significant strain hardening behavior.This study shows that the 3D stochastic model can be used to well represent macroscopic mechanical properties and microscopic failure mechanisms of soil-rock mixture

which can be served as a model to explore the mechanical property.