Numerical Investigation of Deformation and Reinforcement in an Alkaline Water-Affected Coal-Seam Roadway Section Within Inclined Strata

Mine-water exposure can alter the mechanical properties of coal and adversely affect roadway stability. However, the relationship between time-dependent coal degradation under weakly alkaline water exposure and deformation at the roadway scale remains insufficiently understood. This study investigates a coal-seam roadway within inclined strata at Sanxin Coal Industry Co., Ltd., Xinjiang, China. Coal specimens were subjected to exposure durations of 0, 5, 10, 20, and 45 d in a laboratory-prepared solution maintained at pH 9, followed by uniaxial compression, Brazilian splitting, and variable-angle shear tests. The experimentally determined degradation trends were incorporated into a three-dimensional 3DEC roadway model using a parameter-retention-coefficient approach. After 45 d of exposure, the uniaxial compressive strength and elastic modulus decreased by 39.8% and 28.6%, respectively. Under the corresponding numerical conditions, roof-to-floor convergence and two-rib convergence increased by 143.3% and 160.0%, respectively. Two-rib convergence remained greater than roof-to-floor convergence, whereas the maximum plastic-zone depth was consistently greater in the roof than in the ribs. Under the most severely degraded condition tested, the proposed bolt–cable reinforcement scheme reduced roof subsidence and two-rib convergence by 35.0% and 33.0%, respectively, while reducing the maximum plastic-zone depth by 12.0%. These findings indicate that coal-property degradation can amplify roadway deformation under the modeled conditions and highlight the importance of considering both deformation and plastic-zone development when evaluating reinforcement measures.