Abstract:

When the tunnel boring machine(TBM) excavates difficult rocks with high pressure, high strength, and high quartz content, the comprehensive rock-breaking performance is low due to the severe wearing of the disc cutters. In this paper, laser-drilling holes are proposed to improve the rock-breaking efficiency of the cutters; a group of experimenting specimens (granite with holes drilled by means of laser) and a group of comparing specimens (granite without holes drilled by means of laser) are prepared, and the penetration of the reduced-scale cutters into the experimenting specimens are tested, with the spacing of the holes drilled by means of laser being 2 mm and the cutter-hole distances varying; subsequently, the macroscopic fragmentation of the rock specimens, the load needed to fragment the rock specimens and the specific energy consumption(E_SE) are compared between the two specimen groups, and the amount of the rock debris, the vertical forces on the cutters during rock breaking, and the energy consumption are analyzed, in order to investigate the feasibility and effectiveness of the mode of rock-breaking assisted with laser-drilling holes. Conclusions drawn are as follows: (1) The rock-breaking amount first increases and then decreases with increasing cutter-hole distance, with the maximum rock-breaking amount occurring when the cutter-hole distance is 5 mm. (2) With a penetration of 3 mm, generally the vertical force on the cutter first decreases and then increases with increasing cutter-hole distance, with little change when the cutter-hole distance exceeds 5 mm. (3) E_SE first decreases and then increases with increasing cutter-hole distance, with the lowest occurring when the cutter-hole distance is 5 mm.

Key words: tunnel boring machine, laser-drilling hole, disc cutter, rock penetration test