Investigation of rock-breaking mechanism by disc cutter and particle size characteristics of rock fragments based on PFC-FLAC coupled simulation

This paper aims to address the issue of three-dimensional modeling in the study of the rock-breaking process. The PFC-FLAC coupled method was used to construct the graded rock assembly that accurately represents the macroscopic fracture behavior of the rock. Based on the models of rock-breaking by disc cutters, the influence of particle radius, cutting parameters, and cutter installation position on the rock-breaking performance, the crack propagation law, and the rock fragment geometry were systematically examined. The results indicate that the coarse-grained model (average particle radius=1.56 mm) exhibits significant inaccuracies in evaluating peak normal force, rock-breaking volume, and specific energy, with errors of 33%, 73%, and 165%, respectively. Furthermore, analysis demonstrates that the particle size and shape characteristics of the rock fragments serve as effective indicators for evaluating the rock-breaking efficiency. Specific energy exhibits a negative correlation with both the coarseness index and absolute particle size of rock fragments. Compared to the center and edge cutters, the adjacent lateral cracks produced by the face cutters exhibit a higher propensity for coalescence. Muck sieving data from field penetration tests were analyzed to investigate particle size distribution, demonstrating that the parameter n in the Rosin-Rammler particle size distribution equation is exclusively related to rock properties. The research findings provide a critical theoretical foundation for the design of tunnel boring machines (TBMs) host and the selection of operating parameters.