Abstract：Combined with the 3D FEM，the end-anchored bolts are simulated by implicit bolt element. The stiffness contribution of bolt and prestress is deduced，and the strength of anchor end is also simulated. The implicit bolt elements are combined in the elements of rock mass，so the mesh generation is extremely simplified. However，the calculated stress of bolt is always greater than the measured value. This paper analyzes the interaction of rock bolt and rock mass，and presents the analytical expression of elastoplastic deformation of rock mass and bolt stress. The results indicate that it is essential to revise the bolt stress by using the formulas when rock mass is in plastic state. Finally，a case study indicates that the implicit bolt element can simulate well the supporting effect. And the calculated results agree with the observed ones. This paper offers some beneficial methods for more accurately simulating the support effect of bolts.
