Non-explosive directional fracturing blasting using coal-based solid waste expanding agent

Aiming at mitigating the high risks associated with conventional explosive blasting, this study developed a safe directional fracturing technique, i.e. instantaneous expansion with a single fracture (IESF), using a coal-based solid waste expanding agent. First, the mechanism of directional fracturing blasting by the IESF was analyzed, and the criterion of directional crack initiation was established. On this basis, laboratory experiments and numerical simulations were conducted to systematically evaluate the directional fracturing blasting performance of the IESF. The results indicate that the IESF presents an excellent directional fracturing effect, with average surface undulation differences ranging from 8.1 mm to 22.7 mm on the fracture surfaces. Moreover, during concrete fracturing tests, the stresses and strains in the fracturing direction are measured to be 2.16–3.71 times and 8 times larger than those in the non-fracturing direction, respectively. Finally, the IESF technique was implemented for no-pillar mining with gob-side entry retaining through roof cutting and pressure relief in an underground coal mine. The IESF technique effectively created directional cracks in the roof without causing severe roadway deformation, achieving an average cutting rate and maximum roadway deformation of 94% and 197 mm, respectively. These on-site test results verified its excellent directional rock fracturing performance. The IESF technique, which is safe, efficient, and green, has considerable application prospects in the field of rock mechanics and engineering.