Abstract:As mining progresses, a certain phosphate mine needs to excavate tunnels in the filling body. How to maintain the stability of the tunnels in the filling body has become an important challenge faced by the phosphate mine. In response to the above issues, research was conducted using methods such as on-site investigation, theoretical analysis, and on-site experiments. Firstly, the deformation and failure characteristics and causes of the roadway were analyzed, and it was believed that the failure modes of the mine roadway were mainly tensile fracture failure, local shear failure, and local collapse failure, which were influenced by the properties of the surrounding rock of the filling body and the geostress. Secondly, based on the characteristics of the filling body, the cross-sectional shape of the tunnel inside the filling body is determined to be rectangular. Based on the unified strength theory, the optimized cross-sectional size of the tunnel is 4m × 4m; Once again, an optimized rectangular roadway support scheme was proposed, using pipe seam anchor support with a length of 1.5m and a support angle of 45 °~50 °; Finally, the obtained rectangular tunnel scheme was applied to the engineering practice of the mine, and the results showed that there was no significant deformation or damage to the surrounding rock after tunnel construction, achieving good construction results and ensuring the stability of the tunnel.