Development of Reinforced Concrete Segmental Lining Design for MRT Bored Tunnels in Singapore

Abstract

Reinforced concrete segments are commonly used as tunnel linings for bored tunnels constructed by tunnel boring machines (TBM). They have been used from 1980s till today for the majority of the Singapore Mass Rapid Transit (MRT) bored tunnels constructed by TBM as permanent supports. This paper describes the development and evolution of the segmental lining design from the Phases I/II of the MRT construction in the 1980s to the current design for the MRT lines under construction. The topics include the general arrangement of the segmental linings, structural design requirements, durability requirements, fire resistance and selection of waterproofing materials of the linings. The design and construction of bored tunnels in close proximity is presented with the experience gained in the past projects. Fire tests conducted by the Land Transport Authority are also presented. The rational, experience and challenges of adopting steel fibre reinforced concrete segments in recent MRT projects are discussed in the paper. The paper also presents in detail the experience gained in Singapore MRT projects in selecting the gaskets for waterproofing of the joints between segments to achieve the durability requirements for the bored tunnels.