Addressing the issue of large rock block detachment during TBM (Tunnel Boring Machine) construction in unfavorable geological conditions at a metal mine in Jiangxi Province, China, the horizontal thrust force of the gripper shoes was systematically analyzed for the first time to reveal its mechanism of inducing tensile failure in surrounding rock, based on the PLAXIS 3D finite element simulation platform and field observations. An optimized support scheme combining "pre-grouting reinforcement and rock bolt-mesh-shotcrete support" was proposed. The study reveales that during TBM construction in Class V rock mass conditions, tensile failure zones developes on the tunnel roof and progressively expandes as the TBM advanced, leading to roof collapse phenomena observed in the project. The support optimization analysis compared three scenarios, such as no support, "rock bolt + mesh + shotcrete" (referred to as bolt-mesh-shotcrete support), and "pre-grouting reinforcement + bolt-mesh-shotcrete support." Results show that the pre-grouting reinforcement scheme significantly enhances the stability of the surrounding rock, reducing the maximum roof deformation by 21.83% and the final deformation by 36.72%. While bolt-mesh-shotcrete support alone has limited effectiveness, it effectively restraines further deformation of the surrounding rock and prevents the detachment of loose rock masses. It is recommended that in similar TBM tunnel construction scenarios in metal mines encountering unfavorable geological conditions, the combined use of pre-grouting reinforcement and bolt-mesh-shotcrete support should be adopted to improve construction safety and efficiency.