Research on rock breaking mechanism of laser-assisted TBM cutter based on continuous-discrete coupling method
Yukun Chen, Zhiqiang Huang, Kai Fu, Meng Yin, Long Li
Abstract
In extreme geological formations such as high stress, high rock strength and high quartz content, the frequent replacement of cutters due to failure during TBM tunneling leads to a sharp increase in construction costs. Laser-assisted TBM cutter rock breaking technology is a novel high-efficiency approach to rock breaking, which reduces rock strength through laser irradiation, whereby enhancing the efficiency of TBM excavation. Nevertheless, the dearth of research on its intricate rock breaking mechanism and rock-breaking characteristics impedes its further application and development. In this work, a numerical simulation model that couples continuous element laser thermo-mechanical analysis with a discrete element model of heterogeneous granite was established. The accuracy and applicability of the proposed model were rigorously validated through experimental tests. The research was conducted on rock breaking by TBM cutter under laser assistance at different power levels. The study revealed the temperature field and crack characteristics of the granite under different laser power levels, as well as the features of newly generated cracks caused by cutter and the variation patterns of the normal force of cutter. The research results indicate that laser irradiation of granite can elevate the internal temperature of the granite to as high as 2000 °C. As the laser power increases, the number of microcracks cracks generated by the laser irradiation of granite also increase. Except for the case of 400 W laser power, the number of tensile cracks exceeds that of shear cracks. Similarly, as the laser power increases, the number of newly generated microcracks under laser-assisted cutter cutting gradually decreases. When the laser power increases from 600 W to 800 W, the maximum rate of decrease in the peak normal force of the cutter is 0.0894 × 10 6 N/W. This suggests that increasing laser power does not always result in better rock breaking performance, instead the optimal rock breaking effect is achieved within a certain range of laser power. This study reveals the rock breaking mechanisms of laser-assisted TBM cutters, filling a research gap in this field. The findings provide valuable insights for advancing the development and engineering applications of laser-assisted TBM cutting technology.