Numerical and experimental investigation of rock breaking method under free surface by TBM disc cutter

To study the rock breaking method under the free surface induced by disc cutter, the rock breaking simulations were first conducted based on the discrete element method, and the dynamic process of rock breaking under the free surface was studied including stressed zone, crush zone, crack initiation and propagation. Then the crack propagation conditions, specific energy, etc. under different free surface distance (S) were also investigated combined with linear cutting experiments. The results show that the rock breaking process under the free surface induced by disc cutter is dominated by tension failure mode. There exists a critical S to promote crack propagation to free surface effectively. And this rock breaking method can improve the rock breaking force and breaking efficiency significantly when proper.