Three Robbins main beam TBMs are to be used on the 44.6km Pahang-Selangor Raw Water Tunnel in Malaysia. The Ministry of Energy, Green Technology and Water has commissioned the tunnel to transfer water from the Semantan River in Pahang State to the Selangor / Kuala Lumpur region, traveling as far as 1,200m (3,900ft) beneath the Titiwangsa mountain range. Excavation is scheduled to begin in late 2010.
The 5.2m (17.2ft) diameter machines and continuous conveyor systems will be provided to the SNUI JV, a consortium led by Shimizu Corporation and Nishimatsu Construction of Japan, along with local companies IJM Corp and UEM Builders Bhd.
After shop assembly, the three machines are scheduled to begin boring between October and December 2010. “Robbins’ experience in hard rock ground conditions, along with their willingness to work together and be a reliable partner with us, were the main factors in choosing the Main Beam machines,” said Mr. Kawata, Project Manager for the SNUI JV.
TBMs 1, 2, and 3 will be used to excavate sections of tunnel 11.6km, 11.6km, and 11.2km in length, respectively. The three machines will be assembled outside their particular adits, then ‘walked’ down a 12% grade for launch from NATM-excavated starter tunnels.
TBM 3 will be launched first from an intermediate adit, followed by TBM 1 boring in the same direction. TBM 2 will be launched last, boring in the opposite direction towards TBM 3. Conventional drill and blast headings will complete the remaining tunnel sections.
The back-loading cutterheads are the smallest ever designed using 19-inch disc cutters—a disc size that will allow for longer cutter life in hard rock. Geologic conditions are expected to consist of 200 MPa (29,000 psi) UCS granite, with moderate squeezing ground and fault zones.
During excavation, ring beams and rock bolts will be used in addition to shotcrete, which can be applied from working platforms directly behind the cutterhead.
If unstable ground is encountered, invert thrust systems can be utilized to avoid gripping against the tunnel walls.
Once complete in 2013, the tunnel will convey approximately 27.6 cu meters of water per second (7,300 gallons per second) for use in domestic and industrial applications.
