Model testing and numerical study on directional fracture induced by arc-shaped charge hydraulic blasting

Directional fracture-controlled blasting technology is widely applied in rock excavation projects; however, traditional pre-splitting blasting and smooth blasting are increasingly struggling to fulfill the engineering demands posed by complex geological conditions, prompting the emergence of various directional fracturing blasting techniques. An arc-shaped charge hydraulic blasting technology integrating slit-cutting, shaped charge, and water-pressure blasting mechanisms is proposed. Pre-split directional notches are formed along the borehole wall using shaped charge blasting, while water medium is employed to enhance detonation energy utilization and promote crack propagation along the predetermined notch direction. A two-dimensional blasting model test apparatus was developed in this study, which fully incorporates the quasi-static effects of detonation gases. Directional fracture mechanisms of arc-shaped charge hydraulic blasting were investigated through scaled model tests, with experimental results validated and supplemented by dynamic finite element numerical analysis. Experimental results demonstrate that the quasi-static effect of detonation gases plays a crucial role in crack propagation. During two-dimensional blasting tests, it is essential to constrain the venting of detonation gases along the outward normal direction of the specimen surface. Compared with the air medium, the peak strain under the condition of complete water medium is increased by 37.6%, and the crushing area is increased by 60 %; However, water is uniformly distributed when transmitting explosion load, so it has no directional crack effect. Compared to air medium, when water was placed on the non-shaped-charge side of the liner charge while maintaining a jet slit in the shaped-charge direction, the peak borehole wall pressure in the shaped-charge direction increased by 47%, with 20% greater main crack length. The borehole wall on the non-shaped charge side remained intact, and fracture length on this side decreased by 45%. The study elucidates the directional fracturing mechanism of arc-shaped charge hydraulic blasting and experimentally validates its effectiveness, providing a novel strategy for contour control in underground engineering blasting excavation.