Theory and simulation investigations on stability control of gob-side entry retaining with coal pillar-backfill body system

Abstract

Gob- side entry retaining (GER) is widely applied in China. Nevertheless, the stability mechanism of the GER with coal pillar-backfill body (CPBB) under dynamic overburden load remains unexplored. A voussoir beam structure (VBS) model is established to analyze roof structure stability during panel advancement, introducing a VBS stability criterion. Reducing block B length l and immediate roof damage variable D, and increasing coal pillar width x_c, lowers the GER structure instability risk. Reducing l and the GER width w leads to a CPBB system stability upswing. A UDEC model was established to systematically reveal how the l, backfill body width x_b, and strength affect the stability and coupling performance of the CPPB system by monitoring the crack damage D_C. Simulation results indicate that at l=14 m, x_b=2.0 m, water-cement ratio 1.5:1, the coal pillar and backfill body have similar D_C but maintain stability, resulting in CPPB system coupling degree Ϗ better. A novel GER method supported by the CPBB was implemented on-site. Monitoring results indicated that the coal pillar peak stresses were 19.17 MPa (ahead), 16.14 MPa (behind), and the backfill body peak stress was 12.27 MPa (maximum). The floor heave was 380 mm, with a 103 mm backfill body rib.

Keywords

Roof structure stability / Gob-side entry retaining / Coal pillar-backfill body system / Coupled bearing

Acknowledgments

The authors are grateful for the financial support provided by the National Natural Science Foundation of China (Nos. 52574126 and 52574144), the Xinjiang Uygur Autonomous Region Key R&D Project Task Special-Department and Department Linkage Project (No. 2022B01051), the Major Project of Regional Joint Foundation of China (No. U21A20107), the Xinjiang Uygur Autonomous Region Tianchi Introduction Plan (No. 2024XGYTCYC03), the Scientific Research Fund of Hunan Provincial Education Department (No. 24A0359), the Urumqi City Hongshan Sci-Tech Innvoation Elite Talents Youth Top Talents Program (No. B241013004), and the National Key Research and Development Program Young Scien-tists Project (No. 2024YFC2910600).

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