Abstract:
China's tunnel engineering is undergoing a transition from large-scale construction to high-quality development. In order to address the issues of bearing performance and long-term service safety of single-layer lining structures under complex geological conditions such as deep burial and weak surrounding rock, this paper proposes a novel mesh-formwork single-layer lining support structure for tunnel surrounding rock. Based on elastoplastic mechanics and the convergence-confinement method, the support strength and surrounding rock-support interaction characteristics of the proposed structure are compared with those of the conventional NATM lining structure. Furthermore, 1:100 scale model tests are conducted to compare the failure modes and bearing performance of the two structures under biaxial compression and biaxial shear conditions. The results indicate that, compared with the conventional NATM structure, the mesh-formwork support structure has a smaller plastic zone radius in the surrounding rock, and exhibits a higher pressure as well as a smaller displacement at the equilibrium state of the rock-support system. Under both biaxial compression and biaxial shear, the mesh-formwork structure demonstrates failure characteristics of integral load-bearing and progressive yielding, with higher ultimate bearing capacity than that of the conventional NATM structure and significantly enhanced overall deformation compatibility.