Stability of surrounding rock in roadways with fractured rock mass: mechanisms and effects of layout optimization

The stability of surrounding rock in coal mine roadways remains a fundamental concern in underground engineering. Rational roadway layout is essential to prevent strength degradation from fracture coalescence and reduce instability risks. Laboratory tests on single-fracture rock specimens, integrated with UDEC Voronoi-based numerical simulations, were conducted to quantify the effects of fracture inclination and confining pressure on crack propagation and failure mechanisms. Validated numerical models of closely spaced roadways were further used to analyze the relationships among the plastic zone, fracture evolution, and roadway spacing. Results indicate that fracture propagation at 30°-60° inclinations is strongly controlled by pre-existing fracture orientation, with crack initiation angles decreasing from 95° to 70° as inclination increases. Higher confining pressures localize crack growth near closed fractures, forming a distinct V-shaped strength distribution. Maintaining roadway spacing greater than five times the roadway radius effectively enhances stability. Elevated in-situ and mining-induced stresses are identified as the main drivers of fracture propagation and plastic zone deepening in the surrounding rock. These findings provide a scientific basis for optimizing roadway layout and assessing stability in coal mines and similar underground engineering environments.