Optimization of Tunnel Boring Machine (TBM) Disc Cutter Spacing in Jointed Hard Rock Using a Distinct Element Numerical Simulation

The Tunnel Boring Machine (TBM) tunneling process in hard rock is actually breakage of a rock mass that is not necessarily intact. Thus, undoubtedly, joints and discontinuities play a role in TBM performance. In addition, this performance depends on the rock breakage efficiency induced by the TBM cutterhead. Both the rock mass and the TBM specifications affect the rock breakage and chipping process and thus in the machine efficiency. In this paper, the chipping process in a type of jointed hard rock under indentation by two TBM disc cutters has been numerically simulated using the Discrete Element Method (DEM) in two dimensions. The spacing of the cutters has been optimized regarding optimization of some defined criteria such as chip thickness, chipping area and also significantly the penetration rate. The optimum cutter spacings on the selected hard and jointed rock were identified to be in the range about 110 to 140 mm for different joints frequencies. According to the simulation results, it is believed that the numerical simulation will contribute to an improved knowledge of rock fragmentation, which will in turn help to enhance mining, drilling and tunneling efficiency through the improved design of mining tools and equipment