Directional projection in stereographic representation of three-dimensional stress redistribution during tunnelling

Abstract The three-dimensional principal stress mutation of surrounding tunnel roof rocks can cause devastating disaster during excavation process. The mechanism of stress redistribution thus becomes critically important to implement the rock bolt support and enhance the safety and stability. This research focuses on the effect of rock bolt installation relative to the optimal orientation alternatives. There are deficiencies in contemporary analytical literature for that purpose. This shortcoming not only increases the construction expenditure unnecessarily but also impacts the engineering stability. The problem with 3D principal stress rotation is that uncertainty in finding the optimal bolt rock implementation during tunnelling. The stereographic projection technique that 3D is transformed to the 2D chart with the benefits of simplicity and brevity. This algorithm allows tunnelling practitioner better understanding and firmer grasp of complexity affiliated with the 3D principal stress rotation process. First we use FLAC3D to simulate the unsupported tunnelling excavation process, to produce the stress redistribution and orientation mutational data of surrounding tunnel roof rocks. We then take the modeling result to generate Stereographical Projection. The result clearly shows the progressive principal stress rotation during tunnelling, and renders the optimal rock bolt orientation.