SMART tunnel breaks through

The first tunnel breakthrough has taken place on the US$500M Stormwater Management and Road Tunnel (SMART) project in Malaysia.

On 11 December, the 13.2m diameter Mixshield TBM, "Tuah", completed a 737m section after 24 weeks of excavation.

Supplied by German TBM manufacturer, Herrenknecht (T&TI, February 2004, p7), Tuah is claimed to be one of the world's largest mixshield slurry machines. The TBM started tunnelling through karstic limestone beneath Kuala Lumpur in July 2004 after a commissioning period, following delivery in February 2004.

An MMC-Gamuda joint venture holds the 40 year concession to design, build and operate the tunnels from the Malaysian government. Both the Department of Irrigation and Drainage and the Highway Authority are jointly supervising the works due to the project's dual intent, which incorporates a stormwater channel and a motorway passage in a single large diameter tunnel.

The primary aim of the project is to mitigate floods in the city centre, with a secondary purpose of easing traffic congestion from the south of the city to the centre.

Under normal conditions, the central 3km section of tunnel will act as a two deck motorway tunnel. Moderate storms will see the motorway section remaining open to traffic, but with stormwater diverted into a bypass tunnel in the lower section of the motorway tunnel.

Severe storms, expected to be encountered once or twice a year, will trigger the closure of the motorway and the full tunnel section will be utilised to divert storm flows, (T&TI, May 2004, p16). This system of primary and secondary function saves an expensive piece of infrastructure from effectively sitting idle for much of the year.

By the end of January Tuah will start a second drive covering a distance of 4.5km. A second TBM, "Gemilang", has bored 350m since getting underway in August 2004. Operated by Wayss & Freytag, this second Herrenknecht TBM will drive 5.3km in the south of the city.

As at 30 November, overall construction progress for the SMART project stands at 37%. The highway section of the tunnel is due for completion later this year, with the bypass tunnel and associated works scheduled for completion a year later.