Cracking and fragmentation in percussive drilling: Insight from FDEM simulation

Percussive drilling is gaining interest for both shallow and deep applications due to its potential for higher drilling rates in hard rocks. Therefore, for efficient rock breaking, the development of advanced percussive drilling simulation tools has the potential to be transformative. Such tools must accurately capture the rock’s response to enable an effective analysis of the fragmentation process. Traditional continuum numerical methods, such as the finite element method (FEM), do not simulate discrete cracks or the contact interaction between rock fragments. The finite-discrete element method (FDEM) is a three-dimensional hybrid method that combines FEM with the discrete element method (DEM) that addresses these limitations. New FDEM simulation results of impacts on Kuru Grey granite show good agreement with published experimental data. The interpretation focuses on two significant processes in percussive drilling: crack propagation and chipping generation. FDEM successfully simulates the evolution of cracks, including radial, side, and inclined cracks, as well as crushed and cracked zones. The simulation also reproduces the coalescence of adjacent craters to generate more chippings. Additionally, the stress state, velocity field and discrete fractures simulated by FDEM provide detailed insights into the different fracture patterns for Kuru Grey granite, enhancing understanding of the fundamental underlying mechanisms.