Bearing capacity of double-lining considering the stiffness degradation

Abstract: The double lining of external segmental lining and inner reinforced concrete lining are usually used for tunnels with high internal water pressure. However, the reinforced concrete is easily cracked under high internal water pressure, the optimal reinforced steel fiber concrete (R/FRC) can be a helpful option for the inner lining. The internal water pressure bearing capacity depends on the relative stiffness of the linings, so far, the stiffness degradation of R/FRC lining under high inter water pressure is not well understood. An analytical model focused on the stiffness degradation of R/FRC lining after cracking was proposed, which considered the variation of bond slip between concrete and reinforcing bar and the debonding process of fibers at cracks. The proposed model is verified by the results of a 1:1 model test based the prototype of a water conveyance tunnels.