Granite fracturing under multipoint sequential and mobile laser irradiation using a grain model

Laser-assisted rock-breaking offers a non-contact, energy-efficient alternative approach for hard-rock tunneling. However, the macroscopic strength decay and micro-damage evolution under multipoint sequential and mobile laser irradiation, especially the numerical simulations, remain inadequately investigated. This study integrates experiments and simulations to address this gap. A laser rock-breaking test bench was established for granite irradiation, supplemented by macroscopic and microscopic analyses to characterize granite fracturing. A coupled grain-based model (GBM), cohesive zone model (CZM), and thermal-mechanical damage (TMD) numerical framework (integrating mineral heterogeneity, cohesive zones, and thermal-mechanical damage) was adopted to simulate full laser rock-breaking (thermal craters, damage zones, and crack propagation) for both modes. Experiments demonstrated that multipoint irradiation’s mass-specific energy decreased initially and then increased, with 51 % strength and 72.93 % elastic modulus reduction (brittle-to-ductile transition); mobile irradiation’s thermal damage zone exhibited a positive correlation with power, and a negative correlation with velocity. Simulations attained high accuracy (crater errors < 10 %, and R 2 > 0.9 for mass removal), with multipoint damage rate exhibiting an S-shaped growth pattern and mobile irradiation exhibiting a linear growth pattern. The findings elucidate distinct fracturing mechanisms and offer validated parameters for optimizing laser rock-breaking in tunneling applications.