Study on instability characteristics and water inrush mechanism of surrounding rock of roadway crossing burnt rock aquifer

Burnt rock aquifers are widely distributed in Northern Shaanxi and Xinjiang, China. During roadway excavation, burnt rock water has the risk of inrushing into the heading face in the form of sudden inflow with the help of water diversion channels. It is of great significance for disaster prevention to explore the water inrush mechanism of roadway excavation through burnt rock aquifers. Taking Yushuling Coal Mine as an example, the field measurement is used to explore the water-rich structure characteristics of burnt rock aquifer. At the same time, the numerical simulation method is used to study the instability process of burnt rock aquifer under the disturbance of large section roadway excavation, and the factors and occurrence mechanism of roadway water inrush are analyzed. The results show that the burnt rock aquifer is broken as the water-rich center. The bearing capacity of the surrounding rock in the burnt rock area of the roadway is weak and the deformation is serious, mainly shear failure. The roof subsidence reaches the maximum in the center of the burnt rock fracture core zone. The water-rich area exposed by the roadway forms a funnel-shaped seepage area centered on the vault. Advanced treatment measures should be taken at a distance of at least 20 m from the exposed burnt rock. Under the influence of excavation, the mechanical balance of broken surrounding rock and the seepage balance of groundwater are destroyed, which causes the redistribution of stress and the instantaneous release of groundwater potential energy, thus causing roadway water inrush. Taking the +1 710 m main return air cross-cut of Yushuling Coal Mine crossing the burnt rock aquifer as an engineering example, the group hole advanced curtain grouting is used to realize the sealing of the burnt rock aquifer and the reinforcement of the surrounding rock at the same time, which achieves the synergistic control effect of safe mining and water resources protection. The research results have certain theoretical value and practical significance for the prevention and control of roadway water damage in shallow buried burnt rock mines in Northern Shaanxi and Xinjiang.