Mechanisms and control of rock bursts in goaf-side roadways under the condition of thick and hard roofs in the Xinjie mining area, Inner Mongolia

Objective and Methods Rock bursts in mining roadways in deep coal mines under the condition of thick and hard roofs severely threaten the safe coal mining of the mining face. To meet this threat, this study, focusing on the No. 3^-1103 auxiliary transport roadway, a goaf-side roadway, in a typical deep mine of the Xinjie mining area, Inner Mongolia, analyzed the external dominant factors and internal driving sources for frequent rock bursts in the goaf-side roadway. Assuming the mechanical characteristics of the rock beam-foundation system, this study constructed mechanical models under loading before roof fracturing based on soft and elastic foundations. Using these models, this study determined the evolutionary patterns of the rock beam energy in the thick and hard roof during the structural evolution of overburden in the stope, as well as their dominant factors. Based on FLAC^3D simulation results, this study investigated the locations and characteristics of high-risk zones of rock burst-induced instability in the goaf-side roadway. Finally, this study developed a scheme for optimizing overburden structures and controlling the stress energy of surrounding rocks in the stope, along with a method for controlling rock bursts in the goaf-side roadway induced by the fracturing of the thick and hard roof. Results and Conclusions The results indicate that zones with frequent rock bursts in the goaf-side roadway are susceptible to instability failures caused primarily by high static loads or high static loads with superimposed dynamic loads. The primary influencing factors of such failures include the thick and hard roof, the adjacent goaf, and section coal pillars. The total energy storage capacity of the roof is related to factors like overburden load, soft foundation coefficient, the elastic modulus and moment of inertia of rock beams in the roof, the limit span of the goaf roof, and the support parameters of the mining face. Specifically, the strain energy density of the rock beams is positively correlated with the overburden load, soft foundation coefficient, and limit span of the goaf roof but negatively correlated with the elastic modulus and moment of inertia of rock beams in the roof and the support parameters of the mining face. During the coal mining along the No. 3^-1103 mining face, section coal pillars and coals in the mining roadway within the advance support pressure zone and its influencing zones are affected by superimposed multiple factors, which lead to stress concentration and energy accumulation. Therefore, these zones face high risks of rock burst-induced instability. Compared to the No. 3^-1101 fully mechanized mining face, these zones exhibit significantly intensified surrounding rock stress and energy concentration. The peak values of stress and strain energy densities in front of the mining face increase by 6.61% and 12.04% at most, respectively. In contrast, the peak values of stress and strain energy densities of section coal pillars increase by 29.2% and 65.1% at most, respectively. Finally, this study developed a comprehensive scheme involving the blasting and pressure relief of high static load zones, the pre-fracturing of the thick and hard roof through deep-hole blasting or hydraulic fracturing, reinforcing energy-absorbing and anti-rock burst supports in the roadway, with significant effects having been achieved in the field application of this scheme.