Research on deformation and failure mechanism and grouting reinforcement technology of surrounding rock control in soft-rock cross-cut mining roadway

To address the challenge of surrounding rock control in floor soft-rock roadways affected by the mining of an overlying working face, this study takes the cross-cut mining over the south-wing main haulage rise in the floor of the 263 mining area in a coal mine as its research background, through a combination of field monitoring, theoretical analysis and numerical simulation, the stress characteristics of the floor strata and the deformation characteristics of the roadway surrounding rock during mining of the overlying working face were analyzed. The research results indicate that under the influence of dynamic pressure from the cross-mining face, the surrounding rock of the south-wing main haulage rise has been severely damaged. The measured fracture range in the roof is 3.55 m, and that in the sidewalls is 2.91 m. As the extent of surrounding rock failure exceeds the length of the anchor bolts, the original support scheme fails to effectively anchor the surrounding rock, making reinforcement support imperative. Based on limit equilibrium theory calculations, the failure depth of the floor rock mass in the 263 mining area reaches 22.4 m, placing the majority of the south-wing main haulage rise within the floor failure zone induced by the mining activities in the overlying 263 mining area. Furthermore, numerical simulations were conducted to analyze the deformation and failure of the roadway surrounding rock under different advance distances of the cross-cut mining face, thereby revealing the deformation and failure mechanism as well as the spatiotemporal evolution law of the surrounding rock in the cross-mined soft rock roadway. Considering the exceptionally soft and fractured nature of the surrounding rock in the south-wing main haulage rise, a novel UFJC grouting material characterized by excellent fluidity, rapid initial setting and high expansibility was developed. The optimal mixing ratio was determined through experimental testing, and its performance was systematically evaluated. In response to the actual site conditions, a reinforcement support method combining deep and shallow hole grouting with supplementary anchor bolts (cables) was proposed. Following the reinforcement of the south-wing main haulage rise, the deformation of the surrounding rock tended to stabilize within 20 to 40 days, the average convergence of the roof and floor was only 134 mm and the average convergence of the two sidewalls was only 114 mm after stabilization, indicating minimal overall deformation of the roadway surrounding rock, and the reinforcement support scheme achieved satisfactory control effects.