Abstract:  The waterproof mechanism of elastic gaskets under water pressure is not clear. Hence, Based on the analysis of the process of water pressure action from segment assembly to tunnel leakage, the fluid structure coupling calculation model is built by the finite element analysis software, the dynamic process of water seeping into joint elastic gasket is simulated, combined with the waterproof performance of joint seal gasket test, the process and mechanism of waterproof performance of gasket are explained, the reason for the increased reliability of double elastic seal gaskets is discussed. The results show that the process of water breaking through elastic gasket could be simulated by finite element model intuitively; during the process from segment assembly to tunnel leakage, the elastic gasket experiences four stages: segment extrusion, external water pushing, water wedge and water breakthrough; when the water pressure P_w<P=α(P₀+P₁), water acts on the outside of the face of the gasket, the waterproof capacity of gasket still has large redundancy; when the water pressure α(P₀+P₁)<P_w<α(P₀+P₁+P₂), the seal gasket is not broken through by the water which wedges in and still has waterproof capability ; when the water pressure P_w>α(P₀+P₁+P_2max) the seal gasket is broken through by the water and the leakage happens; the first seal gasket can self-recover because of the contact stress increment caused by the water in the cavity between the seal gaskets, which increases the waterproof reliability.

Key words:

shield tunnel, gasket; waterproof joint, fluid-solid coupling, contact stress