Simulating the crack propagation and cracks coalescence underneath TBM disc cutters

A coupled numerical-experimental analysis of crack propagation, cracks coalescence produced during the cutting action of TBM disc cutters has been studied. A numerical code is developed based on the higher order semi-infinite displacement discontinuity method (HSDDM) for the numerical simulation of rock-cutting process. Aquadratic displacement discontinuity variation along each boundary element is assumed to evaluate the mode I and mode II stress intensity factors (SIFs). Based on the linear elastic fracture mechanics (LEFM) theory, the maximum tangential stress criterion is implemented in the HSDDM2D code for predicting the crack initiation and its direction of propagation (cracks propagation path). Some experiments were done to evaluate the final breakage path during the cutting process of disc cutters in rock-like specimens. The same experimental specimens have been numerically modeled by a higher order semi-infinite indirect boundary element method. The numerical and experimental results are in good agreement and demonstrate the accuracy and effectiveness of the proposed numerical method. Rock-cutting mechanisms under single and double type discs are simulated by HSDDM2D. Effects of some specific disc parameters, i.e., penetration depth (P-d) and S/P-d ratio (ratio of disc spacing (S) to penetration depth (P-d)) on the specific energy (E-S) are also investigated.