The Effect of Laser Irradiation on the Compressive Strength of Granite Under Uniaxial Compression

In order to improve the crushing efficiency of drilling machinery, laser-assisted mechanical rock-breaking technology has gained wide attention in the field of engineering construction. In this method, the weakening effect of the laser on the compressive strength of the rock is a key factor of the technology. To reveal the weakening effect of the laser on the compressive strength of rocks, standard uniaxial compression tests were carried out on irradiated rocks using a uniaxial compression testing machine. The weakening effect of laser power and irradiation time on rock strength and rock failure mode was investigated. The experimental results show that the laser power and irradiation time have similar effects on the mechanical properties of the rocks. With the increase of laser power and irradiation time, the peak stress of the specimens shows a tendency to decrease rapidly and then slowly. At the same time, the rock elastic modulus decreases and peak strain increases, and the behavior eventually transform from brittle damage to plastic damage. Melting pit holes and crack networks are the root cause of the weakness of the compressive strength. On one hand, the vertical melting pit hole provides a conical free surface, which reduces the rock deformation constraint and generates stress concentration at the bottom of the hole, so that it facilitates the splitting-tension damage of the specimen. On the other hand, the axial load induces symmetric tensile cracks in the thermal cracks, and adjacent tensile cracks interpenetrate to create a surface of tensile damage, leading to fragmentation of the specimen in the form of rock blocks, ultimately undermining the rock. This work provides an improved understanding of the effect of lasers on the compressive strength of rocks in engineering applications.