Experimental study on wedge-shaped crack propagation in moulded coal with pre-existing cracks induced by CO₂ gas fracturing

CO₂ blasting faces challenges in practical applications, including significant energy dissipation during borehole initiation and difficulty in controlling the initiation direction. Crack-inducing technology can effectively address these issues. Accordingly, based on a self-developed CO₂ gas fracturing experimental platform, tests were conducted on moulded coal with prefabricated wedge-shaped cracks under combined dynamic and static loading conditions to systematically investigate the effects of various dynamic-static load combinations on crack morphology, crack opening displacement, and displacement field evolution. The experimental results indicate that increases in dynamic and static loading pressures are positively correlated with the propagation length and extent of surface cracks on the specimen. When the gas fracturing pressure increases from 1.2 MPa to 2.4 MPa, the opening displacement of the tensile crack induced by the explosion increases from 1.084 mm to 4.130 mm. Furthermore, the prefabricated crack exhibits a significant guiding effect on the propagation direction of the explosion-induced crack.