Liebherr HD crawlers excavate Singapore transport link

Contractor Soletanche Bachy is using seven heavy duty cycle crawler cranes from Liebherr to help excavate deep slurry wall trenches at part of Singapore's new downtown uinderground Mass Rapid Transit Line (DTL).

The work is taking place at Bugis district interchangebale station, a heavily populated part of the city.

The 40 km DTL is being built in three phases to include 33 stations connecting the northwestern and eastern areas of the island to the central business district and Marina Bay. For Bugis station and its tunnels, part of phase one, Soletanche Bachy is working with local contractor Koh Brothers.

The vertical alignment dictates that the new downtown line travels below the existing Bugis Station. This means the line is considerably deeper than usual. The soft ground, means deep and substantial slurry walls must be contructed. Cross-walls are being used to add support to the slurry walls below formation level.

Towards the northern end of the site, the cut and cover tunnels will be constructed in a very tight working area, between commercial and residential buildings.

A total of 11 Liebherr excavator rigs, including the seven Liebherr HS 855 HD machines, are in use at the site. Four of the Liebherr HS 855 HD machines excavating the slurry wall trenches are each fitted with KS3000 hydraulic grabs.

"The combination gives us very accurate control of the digging, which is important on a site with restricted space. The sound level is also significantly lower than it would be with a rope-operated grab, which is an important factor on a city-centre project such as this," said Alistair Sim, Soletanche Bachy regional director.

Much of the slurry wall is 1.5m thick and up to 65 m deep. With such soft ground, the slurry wall contains heavy reinforcement cages weighing up to 100 tonnes per panel and constructed in concrete pours greater than 600m³. In total, Soletanche Bachy is constructing about 140,000 m² of slurry walls, cross walls and barrette foundations on the contract.

Work on site began in January 2009 and will be completed by 2013, says Liebherr.