Abstract: The fractures of rock significantly affect the efficiency and safety of rock breaking caused by tunnel boring machine (TBM) disc cutters. The present study established a discrete element model of randomly fractured rock using the Monte Carlo method, and investigated the correlation between random fractures geometry parameters (dip angle, fracture diameters and fracture density) and rock mechanical properties (strength and elastic modulus) through uniaxial compression simulation. Subsequently, the randomly fractured rock breaking by disc cutter was simulated using the discrete element method (DEM). The results demonstrated a clear linear correlation between the dip angle, diameter and density of random fractures with the strength and elastic modulus of rock, and a multiple linear regression prediction model for the mechanical properties of randomly fractured rocks was established. During construction simulation, the rock-breaking specific energy increased with an increase in fracture dip angle, while it initially decreases and then increases with increasing fracture diameter and density. Based on numerical simulation results, a correction factor for rock-breaking force was introduced into the Northeastern University rock-breaking force prediction model, thereby establishing a prediction formula that accounts for the influence of random fractures.

Key words: random fractures, rock breaking, discrete element method, rock-breaking force, tunnel boring machine