German TBM manufacturer, Herrenknecht, has won a lucrative deal to supply two 13.2m diameter slurry TBMs to the 9.7km long Stormwater Management and Road Tunnel (SMART) project in Malaysia’s capital city, Kuala Lumpur.

The approx. US$650M tunnel will be constructed in two drives, north and south, from a single shaft near the city centre. Client, Gamuda, has awarded the 5.5km long northern drive to Wayss & Freytag and has opted to tunnel the 4.2km long southern drive itself. The Wayss & Freytag machine is scheduled for delivery in Jan/Feb next year ready to hopefully start boring in June. Gamuda’s machine will arrive some three months later and is scheduled to go to face in September 2004.

The tunnel alignment runs through the upper horizon of the area’s karstic limestone, explaining the need for slurry machines, as the drive will switch between a full face of 50MPa-80MPa limestone and alluvial sediments. The TBMs will erect a concrete lining comprising eight segments and a key with an 11.3m i.d.

The main purpose of the tunnel is to divert storm overflows from a major river in the city’s north, to the south. An innovative feature of the design is the central 2.7km long section that will double up as a toll road tunnel during dry periods. The road deck will be roughly two-thirds down the tunnel section with the bottom third still acting as an overflow tunnel. During the once-twice yearly heavy storms, the road tunnel will be closed and the full tunnel section will be used to divert the dramatically increased flows.