Comparative analysis and application of a new stability model for the tunnel face with Mogi-coulomb criterion

Tunnel face stability is a fundamental concern in underground construction, essential for safe and efficient project completion. Traditional models offer various approaches to tunnel face stability analysis; however, they often lack integrating of complex geological factors, particularly intermediate principal stress, which significantly influences rock strength. This paper proposes a computational model for assessing tunnel face stability, incorporating the effects of intermediate principal stress and round length. Building on classical wedge-prism models and previous physical model tests, the proposed model simulates a wedge-shaped failure zone at the tunnel face and a prismatic failure surface above it. The model’s reliability is validated through comparison with four established models, demonstrating its robustness. Key findings reveal that the overburden ratio impacts the limit support pressure, initially increasing and then stabilizing, and that tunnel face stability exhibits a non-linear decrease as round length increases. Intermediate principal stress has a notable effect on stability, especially when its coefficient reaches 0.5. The proposed model’s alignment with established models across diverse conditions underscores its reliability and practical applicability in preliminary tunnel design and safety assessments. The model further enhances current analysis by providing insights into how intermediate principal stress and round length interact to influence tunnel stability under true triaxial conditions, offering practical guidance for underground engineering. Article Highligts A new stability model for the tunnel face, considering the intermediate principal stress, is proposed. Unsupported span could largely affect the stability of tunnel face. Material and geometric parameters are analyzed in detail.