Abstract: The waterproof mechanism of elastic sealing 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solid coupling calculation model is built by finite element analysis software to simulate the dynamic process of water seeping into joint elastic gasket. And then by conducting the waterproof performance test of joint sealing gasket, the process and mechanism of waterproof performance of gasket are explained, and the causes for the increased reliability of double elastic sealing gasket are discussed. The results show that: (1) The fluidsolid coupling model can directly and finely simulate the process of water breaking through elastic gasket. (2) During the process from segment assembly to tunnel leakage, the elastic gasket experiences four stages, i.e. segment extrusion, external water pushing, water wedge and water breakthrough. (3) When the water pressure pw<p=α(p0+p1), water acts on the outside of the gasket face, and the waterproof capacity of gasket still has large redundancy; when α(p0+p1)<pw<α(p0+p1+p2), the sealing gasket is not broken through by the water which wedges in and still has waterproof capability; and when the water pressure pw>α(p0+p1+p2max), the sealing gasket is broken through by the water and the leakage happens. (4) The first sealing gasket can selfrecover because of the contact stress increment caused by the water in the hollow between sealing gaskets, which increases the waterproof reliability.

Key words: shield tunnel, elastic sealing gasket, joint waterproof, fluidsolid coupling, contact stress