Numerical study on roadway stress control of surrounding rock through hydraulic fracturing-induced cracks in gob-side roof based on phase-field theory

<title>Abstract</title> <p>Hydraulic fracturing is an effective stress-relief technique for coal mine roadways, yet the coupling mechanism between fracture network evolution and surrounding rock stress relief remains unclear. This study develops a phase-field model incorporating a linear piecewise stress function at boundaries to simulate mining-induced stress redistribution, enabling systematic evaluation of segmented roof Hydraulic fracture (HF) in gob-side roadways. Four quantitative indices—fracturing range, fracture density, fractal dimension, and fracture connectivity—are introduced to characterize fracture networks and assess pressure-relief performance. Results reveal that the proposed phase-field model can effectively capture the segmented roof hydraulic fracturing behavior in gob-side roadway. Fracture propagation is jointly governed by in-situ stress, pre-existing fractures, and stress interference from adjacent boreholes. Stress-reduction zones from multiple fracturing stages synergistically improve the surrounding rock stress environment. As stress concentration intensifies, fractures on the coal pillar side transition from horizontal to vertical propagation, causing the pressure-relief effect to stabilize initially then decline, while peak pillar stress first decreases then increases. Fracturing range, density, and fractal dimension correlate negatively with stress reduction effectiveness, whereas connectivity shows positive correlation. Optimal fracturing parameters should prioritize well-connected fracture networks under site-specific stress conditions to maximize surrounding rock control. These findings provide practical guidance for hydraulic fracturing design.</p>