Stress and Displacement of Deep-Buried Composite Lining Tunnel under Different Contact Conditions

Stress and displacement of the composite lining are important factors to be considered during tunnel design. By the complex variable method, analytical solutions for stress and displacement of surrounding rock, primary support and secondary lining satisfying the interface continuity and boundary conditions under far-field stresses are derived. Taking the railway composite lining tunnel as an example, the analytical distributions of stress and displacement along boundaries are given, which was in good agreement with the numerical solution calculated by finite element software. The results show that the maximum normal stress ratio (load sharing ratio) of the outer boundary between the secondary lining and the primary support is 0.74. The radial displacement of the inner boundary of surrounding rock, primary support, and secondary lining change consistently. The maximum settlement and uplift occur at the vault and bottom, respectively. The tangential stress of secondary lining is compressive stress, while the tangential stress of primary support is tensile stress and compressive stress. The maximum tangential stress of primary support and secondary lining is smaller than the allowable stress of concrete.