Stability analysis of a tunnel face reinforced with bolts considering the intermediate principal stress component

The stability of the tunnel face during excavation is a critical issue in tunnel construction. Traditional methods have offered various approaches for analyzing tunnel face stability but often neglect complex factors such as the intermediate principal stress. The mechanical behavior of rocks, however, is strongly influenced by the intermediate principal stress. This paper investigates the effectiveness of bolt reinforcement and pre-grouting techniques in enhancing tunnel face stability. A comprehensive 3D model is developed to incorporate the intermediate principal stress with Mogi Coulomb criterion to assess the impact of these reinforcement methods. Our findings suggest that the critical bolt reinforcement length ranges from \:0.3D (tunnel diameter) to \:1.0D , significantly reducing extrusion deformation and enhancing tunnel stability. Pre-grouting improves the cohesion and strength of the surrounding rock, effectively preventing seepage and collapse. The safety factor obtained from the model calculations shows that SF increases with the increase of the intermediate principal stress coefficient, reaching its maximum value when the coefficient is 0.5, and then decreases. The reliability and practical applicability of our proposed model are validated through a comparative analysis with classical models. This research could provide essential guidelines for optimizing tunnel face reinforcement strategies, ensuring safer and more efficient tunneling operations.