Abstract:The failure progress of geological material is a key scientific problem in the engineering of geological hazard and control,and is also a frontal problem in mechanics. The continuum-based discrete element method (CDEM) is a numerical method to research this problem. According to the method to solve eigenvalues of matrix,the analytical expressions of the spring stiffness in the discrete element from the stiffness matrix of the three-dimensional finite element is deduced;and the rules how to choose the spring in the discrete element under different conditions are presented. The spring properties of the discrete element in the 8-node solid isoparametric element is investigated;the expressions of the stiffness and directions of the spring between common edge particles,between common diagonal of face particles and between common diagonal of cubic particles are deduced;and the figures about the relation between the stiffness and directions of spring and Poisson ratio are given. Finally,the CDEM is compared with both Gusev model and two-dimensional nets model. When the Poisson′s ratio is 0.25,the CDEM model is consistent with two-dimensional nets model in plane stress problem. And when the Poisson′s ratio is 1/3,the CDEM model is consistent with two-dimensional nets model in plane strain problem. In block interior,the CDEM model is consistent with Gusev model. The CDEM model can simulate boundary element which Gusev model and two-dimensional can′t,and is proved to be more universal than the other models.