Sentosa Gateway to Kampong Bahru Road / Keppel Road
The project (Contract ER290) stretches from Sentosa Gateway to Kampong Bahru Road. The site is generally located beneath existing roads with heavy traffic. Part of the project involves two mined tunnels, one single and another double-lane tunnel crossing under several major roads such as Sentosa Gateway, Telok Blangah Road, Keppel Road, and Kampong Bahru Road. These mined tunnels are constructed between existing bridge piers and above various underground structures including the segmentally lined MRT, within the soft marine clays of the Kallang formation. The overburden ranges from 2.5 to 8.0 meters. The temporary structure comprised Dia.813mm x 16mm thick contiguous pipes arranged in a box-like structure. These large diameter 2.7 feet (0.82 meters), heavy steel pipes will be used to pre-stabilise the ground surrounding the final tunnel. The steel pipes will be installed by micro tunnelling methods around the final structure to provide initial ground support. The interlocking pipes will be filled with concrete. The design allows for utilities and roadway traffic to be kept operational during tunnel construction.
Dr Bedi was employed as a sub-consultant to undertake detailed design of the two mined sections of the tunnel. The work involved 2D and 3D numerical analysis and closed form calculations to justify the design of the structural support members, and stability of the ground using the proposed method, and production of detailed design drawings for both the temporary and permanent works. Dr Bedi was also responsible for assessing the effects and magnitude of tunnelling induced settlements on the surface and at the location of critical adjacent structures.