Abstract: To investigate the evolution of thermal fracture cracks in granite under varying pressure conditions, numerical methods were employed in conjunction with microscopic damage theory to establish a rock thermal elastic constitutive model. A mineral particle morphology extraction technique tailored for Comsol Multiphysics software was introduced, facilitating numerical simulations on thermal fractures in granite under static water and uniaxial pressures. The dynamic progression of tensile and shear cracks was analyzed. Findings suggest that the sequence of thermal fractures in granite minerals is contingent upon their individual mechanical properties and strength, with the rupture sequence of the three minerals is mica, feldspar and quartz. The thermal fracture network comprises both tensile and shear fractures, with tensile fractures predominantly shaping the network. Fracture evolution unfolds in three stages: micro-fracture initiation, fracture eruption, and stable growth. The thermal fracture threshold is governed by the minimum principal stress, with uniaxial pressure exerting a minor influence compared to hydrostatic pressure. Fracture development under hydrostatic pressure lacks clear directionality. Uniaxial pressure propagates perpendicular to the minimum principal stress, with directionality becoming more pronounced as pressure increases.

Key words: granite, thermal cracking, numerical calculation, crack propagation