NATM for Singapore

摘要

Singapore has some experience in the application of NATM for tunnel construction. To date, tunnels of smaller size have been constructed using this technique. The Fort Canning Tunnel is a three-lane vehicular tunnel with a span of approximately 48 feet and is the first wide span tunnel in Singapore constructed by NATM. Its location in soft ground combined with a high groundwater elevation and shallow cover of about 12 feet called for special design considerations in particular in the use of systematic pre-support techniques. A special pre-support umbrella (AGF) consisting of steel pipes and synthetic grouts for ground improvement is utilized. The tunnel design has been developed in close cooperation with the contractor Sato Kogyo in a design-build framework. As a result of the tunnel collapse that occurred on a cut-and-cover construction for Land Transit Authority's subway system the design development was subjected to a rigorous review and checking process.