Search

This paper reviews the material properties of the seal gaskets of shield tunnels. In order to understand the function of sealing gaskets, the significance and structure of gaskets in tunnel segments are briefly introduced. Then, the material types of gasket are presented. Gasket materials include two categories: (i) the traditional elastic gasket and (ii) the hydrophilic composite elastic gasket. The traditional elastic gasket is composed of chloroprene rubber (CR) and ethylene propylene diene rubber (EPDM), in which the sealing function is implemented as a result of the elastic properties of the materials. The hydrophilic composite elastic gasket includes vulcanized water swelling rubber (WSR) and water swelling polyurethane (WSP), in which the sealing function is obtained from both the elastic properties and the water absorption ability of the gasket material. CR and EPDM were the earliest materials used in engineering practice; however, EPDM is the main material of the gasket today. The sealing mechanism of both CR and EPDM is presented at the molecule level. After that, the water absorption process for both WSR and WSP in hydrophilic composite is reviewed. Methods to improve the sealing behavior of WSR are also summarized. Furthermore, the aging of the gasket material is discussed. Finally, perspectives for future developments of new materials or ways to improve the performance of seal gaskets are proposed.

The impacts of composition and mixture ratio of backfill grouts on the anti-floating ability and workability cannot be ignored in the submarine tunnel engineering. The orthogonal tests were adopted to design a new hardened cement-lime grouting material (HCLGM) and its physical properties were examined. The results show that the shear strength, density, consistency and bleeding rate of HCLGM are largely influenced by the water-binder ratio while the setting time is mainly affected by the cement-fly ash ratio. The recommended mixture ratio for grouting material was determined by linear regression analysis method which is sand of 16.3%, cement of 6.6%, slaked lime of 13.4%, fly ash of 26.5%, bentonite of 4.8% and water of 32.4%. The proposed HCLGM was used in a practical engineering case and contributed to the anti-floating capacity of tunnels.