Modeling rock bolt behavior by using the interface model of DEM

Rock bolt is one of the major support systems of tunnel engineering. It is used to stabilize suspended rock blocks around an excavation section, reinforce rock mass, and reduce displacement along rock joints. This study proposed a rock bolt model, which includes two parts: a bolt body and interface. The bolt body is made of raw bonded ball elements, and interfaces between the rock bolt and surrounding rock mass are simulated using a smooth-joint model The proposed model was first verified using laboratory pull-out and shear tests. Simulation results were consistent with experimental results in terms of a force–displacement curve and failure morphology. A series of tunnel cases were further simulated. The results showed that the proposed model can simulate rock bolt functions on tunnel excavation. Furthermore, the results showed that increasing the length and number of rock bolts increases the reinforced effect; however, as the length and number of rock bolts increased to an upper bound value, a limited increment was observed in the reinforced effect. The proposed model provides a useful tool to simulate the rock bolt system for tunnel engineering.