Numerical simulation and experimental studies of rock-breaking methods for pre-grooving-assisted disc cutter

To improve the efficiency of tunnel boring machines (TBMs) in hard rock environment, the technology of pre-grooving-assisted disc cutters for rock breaking was studied. Firstly, considering the relative position of the pre-grooving and the disc cutter, the same trajectory (SM) and different trajectory (DM) pre-grooving-assisted rock-breaking modes were proposed. Secondly, the discrete element method was used to simulate the crushing process of the pre-grooved rock by the cutter, and the rock-breaking mechanism and laws of different pre-grooving-assisted modes were revealed. Thirdly, a full-scale linear cutting experiment was conducted, which proved the correctness of the research results. Finally, suggestions for the use of the assisted rock-breaking mode were provided. Results show that the DM and SM modes achieve the effect of assisted the disc cutter in breaking the rock by promoting the tensile failure of the rock. Groove has the effect of inducing crack propagation. The groove in DM induces the crack to develop to both sides, and that in SM induces the crack to develop vertically. Compared with the complete cutting mode (CM), the SM and DM modes exhibit improved rock-breaking performance. Specifically, DM and SM are more helpful in reducing specific energy and cutting force, respectively. For the DM mode, with an increase in groove spacing, rock-breaking specific energy decreases and cutting force increases. This study provides ideas and guidance for the application of water jet pre-grooving-assisted TBM rock-breaking technology.