Mott MacDonald was engineering designer for three of the six MCE construction contracts, including a 3.5km tunnel. Singapore is famous for large cut-and-cover tunnels in soft ground but, at 60m wide, MCE was bigger and more challenging than anything previously attempted.
We worked closely with contractors Samsung and Ssangyong to deliver safety, cost and time benefits, including:
- 40% reduction in steel reinforcement
- 36% saving on concrete
- US$70 million saving on retaining strut layers
- 60% cut in lifting and manual handling operations
Singapore’s construction safety culture has been shaped by the catastrophic collapse of a cut-and-cover tunnel in similar ground conditions at Nicoll Highway in 2004. The indicative design for MCE was devised to maximise safety. But by applying ingenuity to our review of the proposed design and construction methods, we were able to deliver more efficient alternative solutions that still met the client’s stringent safety requirements.
These solutions reduced use of concrete and steel by thousands of tonnes, so also reducing the level of embodied carbon. The pipe pile walls and steel struts used for retaining were fully recovered following completion of the tunnel. The large volume of excavated material – 4.3 million cu m – will be used for ongoing reclamation work in Singapore.
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