On Asymmetric Failure Characteristics of Tunnels and Surrounding Rock Control Techniques Under Close-Distance Repeated Coal Mining

Abstract

In response to the problem of significant deformation and obvious strata pressure in tunnel caused by close-distance repeated mining, along with difficult control of surrounding rocks, theoretical analysis, and numerical simulation methods were employed to study the asymmetric failure characteristics of tunnels under the influence of close-distance repeated mining. The research provided insights into the mechanism of asymmetric failure of tunnels affected by close-distance repeated mining, revealed the impact of residual coal pillars in the upper coal seam on the tunnel in the lower coal seam, analyzed the stress distribution of surrounding rocks before and after tunnel excavation under the influence of repeated mining, and proposed asymmetric surrounding rock control techniques for tunnels affected by close-distance repeated mining. The study results indicate that the protection of coal pillars in the upper coal seam and the adjacent working face mining in the same coal seam are the main reasons for significant stress concentration on one side of the tunnel and the appearance of asymmetric failure characteristics. After tunnel excavation, the stress of surrounding rocks is released into the tunnel, resulting in a significant reduction in stress environment. However, the stress on the left side of the tunnel is significantly higher than that on the right side, showing an asymmetric distribution. The application of active support with anchor net cables and U-shaped steel frames effectively reduces tunnel deformation, with good on-site application results.