An Extended 3D Discontinuous Deformation Analysis Method Considering Bolt Supports and Its Application in Tunnels

Implementing bolt supports is the main means of controlling block instability. However, the original three-dimensional discontinuous deformation analysis method (3D ODDA) is still unable to simulate bolt supports, making it difficult to study the control effect of bolt supports on block instabilities. Therefore, an extended three-dimensional discontinuous deformation analysis method (3D EDDA) that can simulate the effect of bolt supports is proposed in this article. Based on the 3D ODDA method, we proposed a simulation algorithm for bolt supports, which improves the constitutive model of the bolt in the original DDA method. Then, we analysed the failure process of a bolt between two blocks and compared the numerical simulation results with the theoretical analysis results to verify the accuracy of the bolt support algorithm in the 3D EDDA method. With the 3D EDDA method, we simulated the failure process of the surrounding rock in a jointed rock mass tunnel at the engineering scale under conditions with bolt supports and without bolt supports. By comparing the results of these two conditions, we deduced the evolution law of the block displacement and bolt axial force around the tunnel and determined the anisotropic characteristics of these items. Specifically, the axial force of the local bolts is relatively small and has a small control effect on the stability of the block in the area. During actual construction, the length or strength of these bolts can be reduced, which can provide a theoretical basis for the design of tunnel bolt support parameters.