A quantitative analysis of the effect of end plate of fully-grouted bolts on the global stability of tunnel

Abstract

Among the analyses of fully-grouted rock bolt in the rock mass, the effect of the end plate on the global stability of the tunnel has not been comprehensively reported. In this paper, a simplified numerical procedure for the interaction between the fully-grouted bolt and rock mass with consideration of the end plate is proposed. The rock-bolt interaction is considered at the initial and final states. At the initial state, immediately after the bolt is installed, a finite difference solution of the stresses and strains in the rock mass is proposed. At the final state, when the fictitious support pressure is negligible, another finite difference solution of the stresses along bolt as well as displacements in the rock mass is presented. To obtain the final results, a simplified iterative process is performed by repeating the finite difference solution at the final stage. The proposed procedure is verified by comparing with the commercially available finite difference software and field results. In the parametric studies, the effects of the end plate for the geological conditions with variation in rock mass quality, in-situ stress, shearing stiffness at the bolt-grout interface, and end plate stiffness are simultaneously investigated. The results indicate that, under the squeezing conditions, the failure mode of the bolt is influenced by the end plate stiffness; an optimum design for the shearing stiffness and end plate stiffness can be implemented in order to achieve an excellent supporting performance of the rock bolt.