Stability Analysis of the Backfill Roof with Basket Weave Drift Layout in Underhand Drift-and-Fill Mining

The stability of a backfill roof is critical to ensure safe production in underhand drift-and-fill mining. In this method, the basket weave drift layout is widely accepted. However, there is currently limited research on the displacement distribution and strength requirement of the backfill roof with this drift layout. To address the gap, a three-dimensional numerical model was established with FLAC3D, with the Maoping Lead–Zinc Mine as the engineering background, to investigate the stability of a backfill roof with the basket weave drift layout. In numerical simulations, an iterative search method was applied to determine the strength requirements of the backfill roof. The results show that the displacement of the backfill roof with the basket weave drift layout shows columnar or strip-like distribution patterns. The strength requirements (unconfined compressive strength) of the backfill roof in limited equilibrium for drift sizes of 3.5 m × 3.0 m, 4.5 m × 4.0 m, and 5.5 m × 5.0 m were determined to be 1.34 MPa, 1.57 MPa, and 2.38 MPa, respectively. A comparison was also made between the strength requirement predicted by traditional analytical solutions and those obtained from numerical simulations, which shows that traditional solutions tend to yield conservative results. The method and analysis process employed in this study can provide valuable references for backfill strength design in mines using underhand drift-and-fill mining.