Full-scale linear cutting tests to study the influence of pre-groove depth on rock-cutting performance by TBM disc cutter

Abstract

To improve the tunnelling performance of tunnel boring machines in hard rock and extremely hard rock environments, abrasive water jet assisted rock breaking is a possible solution that has currently attracted considerable attention. In this approach, the depth of the pre-cut groove is a key factor affecting the performance of assisted rock breaking. To study the influence of the pre-groove depth on assisted rock breaking performance, a full-scale linear cutting test of pre-grooved rock was conducted with a disc cutter. The influence of the pre-groove depth on the rock breaking effect under the same-trajectory mode (SM) and different-trajectory mode (DM) of assisted cutting was explored, and the mechanism of assisted rock breaking with different groove depths was revealed. Compared with the complete cutting mode (CM), the results showed that the normal force (FN), rolling force (FR), side force (Fs), and specific energy (SE) under SM decrease as the groove depth increase. Under DM, the FN, FR, and SE decrease as the average groove depth on both sides increase, and the Fs decreases as the minimum groove depth increases. In SM and DM, the cutting SE first decreased rapidly and then tended to decrease slowly as the groove depth increased, indicating the existence of an optimal groove depth. The rock fracture patterns under SM and DM are more prone to tensile failure, which significantly reduces the rock cutting force and SE of the disc cutter. These results can provide inspiration for the design and construction of new types of tunnel boring machines that are assisted by abrasive water jet pre-grooving.