Study on rockburst mechanism and layout optimization of top-coal roadway in the inclined thick coal seam

To investigate rockburst mechanism and optimize prevention measure for roadway excavated in inclined thick coal seams, the roof-type rockburst during the development of the (4–5)06W belt roadway in a Xinjiang coal mine was taken as the engineering background. The characteristics of rockburst manifestations in inclined thick coal seams with top-coal roadways were systematically analyzed with field investigation, laboratory experiment, mechanical modeling and numerical simulation. The failure zones of impacted roadways were categorized into closure areas, severe damage areas and critical deformation areas. Field investigation identified the roof coal as the primary impact carrier. Roles of key influencing factors including coal seam dip angle, thickness, and coal-rock combinations in rockburst initiation were analyzed. Numerical simulation was used to reproduce the dynamic impact phenomena under engineering conditions, followed by a mechanistic analysis of rockburst mechanism. Optimization strategies for anti-impact roadway layout and hazard mitigation measures during excavation were proposed. It is found that normal stress increases slightly with coal seam dip angle, while roof shear stress undergoes three phases: reduction, gradual growth and rapid escalation. Energy accumulation in semi-coal-rock roadways exceeds that of roadways in pure coal seams under identical conditions. Three critical mechanisms governing rockburst in inclined thick coal seams were identified: dip-induced asymmetric stress distribution in roof strata; compromised anchoring efficacy due to excessive cable length, hindering composite suspension effects; synergistic action of inclined sliding forces and horizontal stresses promoting roof coal delamination and collapse. Microseismic transition from intense energy release to high-frequency/low-energy dissipation was observed after prevention measure optimization. The optimized scheme significantly reduced rockburst risks, enabling safe drivage of the remaining (4–5)06W roadway.