The SNUI JV, consisting of Shimizu Corporation/Nishimatsu Construction/UEM Builders Bhd/IJM Construction has launched the second of its three 5.2m diameter Robbins Main Beam TBMs being used to bore the three tunnels that make up the 44.6km long Pahang Selangor Raw Water Tunnel near Malaysia’s capital Kuala Lumpur.
The project’s first TBM was launched on November 10, 2010, and is advancing as scheduled while the total back up is being installed. A third machine will begin boring in March 2011. Tunneling is taking place with overburden of up to 1,200m, below the Titiwangsa mountain range. The three tunnels, measuring 11.8km, 11.8km, and 11.3km 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 utilized to avoid gripping against the tunnel walls. The precast concrete invert segments are being manufactured onsite.
All of the machines are being assembled outside their particular adits, then ‘walked’ down a 6-10% 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 100m, the remaining back-up decks and permanent Robbins continuous conveyor are being installed, due to the adit configurations.
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During the initial stages of advance, the machines have achieved rates of up to 3.5m per hour in hard, abrasive granitic rock up to 200MPa UCS. Each TBM is fitted with 19-inch back-loading cutters for excavating 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-inch 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.
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 cubic meters of water per second to a new treatment plant. The drinking water will supply about 7.2M people by 2013.