Robbins Rallies at Malaysian Water Tunnel
February 24, 2011The second in a trio of 5.2-m diameter Robbins Main Beam TBMs commenced boring on Dec. 30, 2010 near Malaysia’s capital Kuala Lumpur.
The machines are being delivered to the SNUI JV, consisting of Shimizu Corporation, Nishimatsu Construction, UEM Builders Bhd, and IJM Construction to begin excavation of the country’s largest infrastructure project. The 44.6-km long Pahang Selangor Raw Water Tunnel will address projected water shortages due to the area’s rapidly growing population.
The project’s first TBM was launched on Nov. 10, 2010, and is advancing as scheduled while the total back up is being installed. A third machine will begin boring in March 2011. All of the machines are being assembled outside their particular adits, then ‘walked’ down a 6 to 10 percent grade to an NATM-excavated starter tunnel. Two of the machines are being launched with a shortened back-up configuration of 10 decks and a temporary transfer conveyor, while the third machine for logistical reasons is utilizing trucks for muck removal in the preliminary boring phase. After boring ahead about 100 m, the remaining back-up decks and permanent Robbins continuous conveyor are being installed, due to the adit configurations.
During the initial stages of advance, the machines have achieved rates of up to 3.5 m per hour in hard, abrasive granitic rock up to 29,000 psi UCS. Each High Performance (HP) Main Beam TBM is fitted with 19-in. back-loading cutters for effective excavation in the hard ground.
The cutters are being carefully monitored in the hard, abrasive conditions using Robbins remote cutter monitoring systems, installed on each of the three TBMs. The wireless system allows the crew to plan cutter changes and keep track of cutter wear by recording several variables on each cutter, including cutter rotation (which is computed to percentage wear), temperature, and vibration. Each 19-in. face and gage cutter is equipped with a sensor bolted inside the cutter housing, allowing raw data to be sent to a program display in the operator’s cabin.
Tunneling is taking place in high cover conditions, up to 1,200 m below the Titiwangsa mountain range. The three tunnels, measuring 11.77, 11.80 and 11.30 km in length, will be supported with ring beams, rock bolts and shotcrete, depending on the conditions. If unstable ground is encountered, invert thrust systems can be used to avoid gripping against the tunnel walls. The precast concrete invert segments are being manufactured onsite.
The Pahang Selangor Raw Water Tunnel, for the Malaysian Ministry of Energy, Green Technology, and Water, will convey raw water from the Semantan River in Pahang to the South Klang Valley area of Selangor state. Once complete, the tunnel will transfer 27.6 cu m of water per second to a new treatment plant. The drinking water will supply about 7.2 million people by 2013.
Desiree Willis is a technical writer for The Robbins Co.