Study on the Effect of the Arrangement of Double Waterproof Sealing Gaskets on the Mechanical Properties of Segment Structures

To meet the development trend of large diameters and high water pressures in shield tunnels, the double-gasket waterproofing system has become the mainstream design scheme for segmental joints in large underwater shield tunnels. The existing double sealing gasket waterproof system can be divided into two types: double sealing gaskets arranged on both sides of the joint (inner and outer double) and double sealing gaskets arranged on the outer side of the joint (outer double), but the influence of these two kinds of waterproof gaskets arrangement on the mechanical properties of segment structures has not been revealed. Based on Jiangyin-Jingjiang Yangtze River Tunnel, the influence of the arrangement of double waterproof sealing gaskets on the mechanical properties of the through joint assembly and staggered joint assembly segment structures is compared by a three-dimensional refined numerical calculation model for the whole segmental ring structure. The results show that: When the arrangement of double waterproof sealing gaskets changes from inner and outer double to outer double, the deformation of the segment structures slightly increases, the axial force of the segment structures changes less, the maximum positive bending moment decreases, and the maximum negative bending moment increases. The safety factor of the segment structures with the outer double sealing gasket arrangement is slightly lower than that with the inner and outer double channel sealing gasket arrangement, but both have higher safety factors and a larger safety margin. Overall, the arrangement of double sealing gaskets on the outer side significantly improves the waterproof ability of the segmental joint, but does not cause excessive deformation of the segment structures. The overall structural system still maintains a considerable safety margin and is currently the most effective option for resisting high water pressure and enhancing the durability of the shield tunnel waterproofing system.