Research on extension mechanism of directional hydraulic fracture under abutment stress based on XFEM

Abstract

Directional hydraulic fracture (DHF) is a commonly used rock control technique in coal mining, with extensive applications in mitigating dynamic ground pressure, managing hard roof hanging, and depressurizing gob-side roadways. However, these fracture zones are typically located near roadways and working faces, where they are subjected to mining-induced disturbances and experience significant abutment stress. In this paper, numerical simulations using the extended finite element method (XFEM) were conducted to investigate the mechanism of DHF propagation in the presence of abutment stress. The influences of stress concentration factor, lateral pressure coefficient, vertical stress, and perforation angle on DHF were analyzed. The results demonstrate that the lateral pressure coefficient is the primary factor determining the redirection of the hydraulic fracture (HF), while the stress concentration factor and vertical stress have minimal influence on the redirection of HF. A perforation angle of 90° yields vertical HFs, but the HF influence range decreases with increasing lateral pressure coefficient. Furthermore, a comparison was made between HF effects with and without guiding boreholes. This research provides important theoretical insights for optimizing the HF technique in the presence of abutment stress in the roof strata.