Roof Cutting and Pressure Relief Surrounding Rock Control Using Pre-Placed Backfill Strip to Replace Coal Pillars: Technology and Field Application

Under green mine construction and efficient resource utilization, non-pillar mining has been increasingly applied. However, surrounding rock control remains difficult in traditional gob-side entry retaining under large mining height conditions. To address this problem, a cooperative control method combining roof cutting and pressure relief with a pre-placed backfill strip for coal pillar replacement is proposed. Taking the 15,108 and 15,110 working faces of Wangzhuang Coal Industry as the engineering background, a mechanical model and FLAC3D simulations were used to analyze the effects of roof cutting height and backfill strip width. The results show that roof cutting shortens the goaf-side suspended roof, weakens lateral abutment pressure, and improves the stress state of the strip. When the roof cutting height increases from 11 m to 13 m, the peak vertical stress of the strip decreases from 16.2 MPa to 13.9 MPa, with a reduction of 14.2%. When the strip width increases from 1.0 m to 1.5 m, the peak stress decreases by about 12.0%. Thus, the reasonable roof cutting height and strip width are determined to be 13 m and 1.5 m. Field monitoring shows maximum roof-to-floor and rib-to-rib convergences of 178.5 mm and 143.5 mm, respectively, with no obvious strip instability.