The surface roughness of particles may have a strong influence on the mechanical properties of granular assemblies. The assumption made in the classic discrete element method(DEM) that the particle surface is smooth makes it difficult to describe the contact behavior of real granular materials accurately. It is necessary therefore to develop the stochastic discrete element method (SDEM) which could quantitatively consider the surface roughness of particles. To this end

the most popular statistical treatment of rough surface—the Greenwood-Williamson(G-W) model is introduced. Then the defects of incorporating the G-W model into DEM simulation are fully addressed. An extended model which treats the rough surface as the combination of two parts is proposed and the corresponding non-dimensional form for subsequent DEM simulations is presented. The pressure distribution

deformation distribution and total contact force obtained by the G-W model and the extended version are compared. It shows that the extended model can better reflect the influence of the surface roughness on contact between rough particles. Based on the extended model

a new normal interaction law ready to be incorporated into DEM is derived by the curve-fitted empirical formula. A user defined contact model of the new normal interaction law is incorporated into (the particle flow code)PFC3D. Numerical simulations are first conducted to compare the influence of the surface roughness on mechanical properties of particulate system under different loading conditions.