Experimental investigation on waterproofing performance of segmental joint with double gaskets for shield tunnel

The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels. The segmental joints with double gaskets have been adopted to improve the waterproof performance for certain tunnels with high water pressure, especially water-conveyance tunnels. This paper presents a series of waterproofing tests on joints with different settings of double gaskets via an improved test apparatus. Four cases are investigated, including (i) double gaskets with equal high/low waterproof capacity, (ii) the outer gasket with higher waterproof capacity, and (iii) the outer gasket with lower waterproof capacity. Different joint openings are also considered. Moreover, the water pressures at two cavities are continuously monitored to highlight the waterproofing mechanism and failure pattern of double gaskets. The results demonstrate that the gasket with the higher waterproofing capacity dominates the overall waterproofing capacity of joint with double gaskets; only a little enhancement of the waterproofing capacity is found for the joint with the same double gaskets. The waterproofing capacity of joints with double gaskets decreases with the increase of the joint opening. The failure pattern depends on the arrangement of double gaskets, and four stages can be identified during the whole failure process. The advantages of double gaskets in case of joint rotation are also discussed.