Study on the influence laws of hole distribution parameters on guided groove-static expansion synergistic fracturing effect

To further enhance the weakening capability of the roof by static expansion fracturing technology, the study explores the influence of construction parameters on the stress distribution around boreholes. Based on the principles of elasticity and fracture mechanics, the synergistic fracturing mechanism between guided groove and static expansion was revealed. Adopting the PFC^2D discrete element method, a corresponding numerical model for static expansion fracturing was established and biaxial confinement and static expansion interaction simulations were conducted by setting different construction parameters. The results indicate that: compared to the conventional single-hole unconfined static expansion fracturing, the guided groove can effectively enhance the effect of static expansion fracturing, and the further the distance from the hole center, the more obvious the lifting effect; the discrete element method can effectively simulate the stress distribution during the static expansion-induced cracking process. There is a positive correlation between the static expansion force, borehole diameter, and the length of the guided groove, and the circumferential stress. Conversely, the angle of the guided groove, the stress coefficient, and the burial depth are negatively correlated with the circumferential stress; the sensitivity ranking of hole parameters is as follows: borehole diameter > groove angle > groove length. In practical applications, the aperture and slot length should be increased as much as possible and the groove angle should be reduced; the groove alters the characteristics of circumferential stress distribution; however, the guiding effect of the groove has its limitations. There exists competitive crack initiation and propagation behavior between the tip of the groove and the surrounding area of the borehole.