Study on Deformation and Failure Characteristics of Roadway Surrounding Rock in Coal Seams with Hydraulic Flushing Cavity Groups and Corresponding Filling−Based Stabilization Control Technology

Aiming at the rib spalling and large deformation occurring in coal roadway during excavation after hydraulic flushing−induced cavity formation in the soft coal seam of Liangbei Coal Mine, this paper takes the excavation of the 21091 machine roadway as the engineering background. This study conducted numerical simulations and field tests to: investigate the influence of hydraulic flushing cavity groups on the stress, deformation, and failure behavior of the surrounding rock under excavation disturbance; analyze the regulatory mechanism of cavity filling extent, filling ratio, and grouting material properties on the surrounding rock of roadway; and verify the engineering effectiveness of cavity grouting filling. The results indicate that: (1) hydraulic flushing disrupts the original stress equilibrium of the coal seam, inducing stress concentration in the coal pillars between adjacent cavities, with a stress concentration factor of 1.3; (2) the superposition of excavation−induced disturbance stress and the pre−existing stress concentration in the coal seam increases the deformation of the roadway ribs and roof−floor by 21.3% and 29.6%, respectively, compared with the non−flushed condition, and the plastic zones of the roadway and adjacent cavities become interconnected; (3) pre−filling of the two rows of cavities adjacent to the excavation face effectively controls surrounding rock deformation, with the control effect improving as the filling ratio and elastic modulus of the fill material increase; (4) based on the above findings, regional grouting of the coal seam cavities renders the deformation of the 21091 machine roadway controllable during excavation with no instability risk, and all borehole gas validation indices meet the outburst prevention safety requirements. The research findings can provide a theoretical basis and engineering reference for the stability control of surrounding rock and regional outburst prevention in similar coal seam roadways containing hydraulic flushing−induced cavity groups.