Cracking characteristics of granite under different laser powers

This article explores the crack characteristics and crack propagation laws of granite under different laser power conditions. Research has shown that high energy lasers induce the generation and propagation of cracks in granite by generating local thermal stress. The experimental research object is granite, and the evolution of crack characteristics is observed by irradiating with five laser powers of 250 W, 500 W, 750 W, 1000 W, and 1250 W for 30 seconds. Research has found that as the laser power increases, the crack opening on the granite end face and the diameter of the central melt hole gradually increase. Cracks are distributed radially symmetrically, and transverse through cracks appear when the power is greater than or equal to 750 W, forming small fragments. The side cracks are distributed in a "human" shape, and the depth of the cracks is basically not affected by the laser power, but the opening increases with the increase of power, and the transverse branching cracks gradually appear. The local heating caused by laser irradiation leads to uneven thermal expansion, resulting in significant thermal stress. When the stress exceeds the strength of the rock, cracks are induced. This study provides a theoretical basis and scientific foundation for the application of laser assisted rock breaking technology in deep resource exploitation and complex engineering.