Abstract：A brief analysis is made on the selection of geometric and physical parameters for the computation of geomechanics. By comparison of several different DEM contact relationships，the physical meaning of joint stiffness in different computational models is discussed. In rigid block model，the joint stiffness is an equivalent stiffness reflecting the stiffness of rock block and joint. As for the deformable block model，the spring stiffness between blocks should be large enough to reflect the real characteristics of rock mass. In general，oversized contact stiffness may influence the computational reliability，and a simple treatment to get rid of the influence is proposed. The damping expression of structural vibration for rock mass is given by dimensional analysis，and the damping ratio can be obtained through vibration test. The characteristic time obtained from dimensional analysis offers a reference value for computational time step. In the end，the criteria of computing control，slide and failure in DEM are introduced.
