Abstract In this paper, a 2D discrete element model was established for jointed rock to study its breaking modes under a TBM cutter. Two groups of cutting simulation tests were designed under the confining pressure of 0~15 MPa, one of which was taken for the horizontal jointed rocks under double cutters (joint spacing js: 80 mm, 100 mm, 150 mm and 200 mm) and the other of which was taken for the inclined jointed rocks under a single cutter (joint angle α: 15°, 30°, 45° and 60°). The results show that: 1) 8 typical breaking modes were observed during the cutting due to the obvious controlling effect of the confining pressure and joint on crack development; 2) the rock-breaking efficiency of a TBM cutter under confining pressure is poorer than that without confining pressure based on a quantitative analysis of the breaking critical stress, standard penetration rate and crack expansion capacity, and the rock-breaking efficiency of a TBM cutter first increases and then decreases with an increase of joint spacing, but increases on the whole with the increase of joint inclination; 3) the rock-breaking efficiency is relatively high in the case of 150 mm joint spacing and a 45°~60° joint angle; 4) most rock breaking modes obtained by the simulation agree well with the ones given by the experimental observation in the literature.
Abstract：
In this paper, a 2D discrete element model was established for jointed rock to study its breaking modes under a TBM cutter. Two groups of cutting simulation tests were designed under the confining pressure of 0~15 MPa, one of which was taken for the horizontal jointed rocks under double cutters (joint spacing js: 80 mm, 100 mm, 150 mm and 200 mm) and the other of which was taken for the inclined jointed rocks under a single cutter (joint angle α: 15°, 30°, 45° and 60°). The results show that: 1) 8 typical breaking modes were observed during the cutting due to the obvious controlling effect of the confining pressure and joint on crack development; 2) the rock-breaking efficiency of a TBM cutter under confining pressure is poorer than that without confining pressure based on a quantitative analysis of the breaking critical stress, standard penetration rate and crack expansion capacity, and the rock-breaking efficiency of a TBM cutter first increases and then decreases with an increase of joint spacing, but increases on the whole with the increase of joint inclination; 3) the rock-breaking efficiency is relatively high in the case of 150 mm joint spacing and a 45°~60° joint angle; 4) most rock breaking modes obtained by the simulation agree well with the ones given by the experimental observation in the literature.
2016, Vol. 53 