Mechanism and prevention of rockburst in deep asymmetric goaf areas coal seam main roadway

With the increasing frequency of coal seam roadway usage, the occurrence of rockburst disasters has shown a rising trend. Research on the mechanisms of rockburst and differentiated prevention measures for coal seam roadways under specific conditions holds significant importance for the safe extraction of deep coal resources. Taking the panel roadways of a mine in Inner Mongolia as the study site, this work combines on-site measurement, theoretical calculations and FLAC^3D numerical modelling to examine the evolution of both the surrounding rock stress field and the overburden structure during the progressive formation of asymmetric goafs on either side of a coal main seam roadway. An index for identifying rockburst risk in the roadway is established, the instability mechanism governing roadway rockburst is revealed, and the targeted prevention strategy is formulated. The research results indicate that the goaf area and the evolution of overburden structure are the primary factors influencing rockburst risk in coal seam roadway areas, and the formation of an asymmetric goaf structure further increases this risk. During the structural evolution of asymmetric goaf areas, the vertical stress progressively becomes the maximum principal stress and exhibits a “twin-peak” distribution within the coal pillar zone adjacent to the main roadway. The vertical stress acting on the surrounding rock of the existing roadways continues to rise, with the stress increment first increasing and then decreasing; the return airway remains within the western stress-peak zone, where the maximum stress reaches 38.7 MPa. In the transverse profile, the overburden structure above the coal pillar zone evolves from an “asymmetric T” shape into a “symmetric T” shape, intensifying the mutual feedback of strata movement on both sides of the roadway. Owing to the structural changes in the goaf areas on either side, the roadway’s surrounding rock experiences intensified stress concentration and increased damage; once the localized stress exceeds its critical failure load, the rock displaces instantaneously toward the opening, triggering rockburst. The critical loads for rockburst failure of the roadway roof and floor are 32.8 MPa and 24.7 MPa, respectively. As the asymmetric goaf evolves, both the potential rockburst risk and the extent of its manifestation continue to expand. A coordinated prevention and control scheme integrating “load reduction – pressure relief – support” at both regional and local levels was formulated, focusing on measures such as optimizing the location of the ventilation roadway and implementing deep-hole roof blasting. Field validation has demonstrated that this approach effectively reduces rockburst risk. The findings can provide a valuable reference for preventing rockburst in coal seam roadways under similar mining conditions.