Waterproofing enhancement mechanism of the double sealing gaskets: Experimental test and theoretical analysis

The waterproofing system of the double gaskets has been employed in shield tunnels with large diameters (>10 m) and high water pressures (>1.5 MPa), but the waterproof enhancement mechanism of this system has not been clarified. In this study, the enhancement in waterproof performance under the equal and unequal joint openings was analyzed through the waterproofing test. A fluid–solid coupled numerical model of the double gaskets was established to reveal the waterproof failure pattern and analyze the variations of the contact stress. On this basis, a velocity-seepage coupled analytical model of the double gaskets was derived to quantify the difference of the water pressure and seepage velocity during the entire failure process. The waterproofing enhancement mechanism of the double gaskets was revealed via the proposed model. The results indicate that compared to the single gasket, the waterproof performances of the double gaskets are enhanced by 15 % to 280 %. The waterproof failure pattern of the double gaskets can be divided into four stages during the whole failure process. The waterproofing enhancement mechanism of the double gaskets is attributed to the difference of the water pressure between the inner and outer cavities due to the presence of the outer gasket so that a higher external water pressure is required to cause the failure of the waterproof system of the double gaskets. The results of this study can be a great benefit for the waterproof design of the double gaskets.