Since the 1980s, Malaysia’s capitol Kuala Lumpur and surrounding areas have experienced rapid economic growth. The area sources most of its water from a network of local rivers, and is forecast to run short of supply in the near future.
To address forecasted needs, the Ministry of Energy, Green Technology and Water has commissioned the 44.6-m Pahang-Selangor Raw Water Tunnel. The alignment will transfer water from the Semantan River in Pahang State to the Selangor/Kuala Lumpur region, traveling as far as 1,200 m beneath the Titiwangsa mountain range. Excavation is scheduled to begin in late 2010 using three Robbins Main Beam TBMs.
The 5.2-m 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.
In addition to the machines, three continuous conveyor systems will be provided for muck removal. The fabric belt conveyors will extend the length of each tunnel section and will be capable of transporting 400 metric tons of muck per hour. Each system will be driven using a 370-kW main drive, plus a 370-kW booster drive.
TBMs 1, 2, and 3 will be used to excavate sections of tunnel 11.6 km, 11.6 km, and 11.2 km in length, respectively. The three machines will be assembled outside their particular adits, then ‘walked’ down a 12 percent 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 toward TBM 3. Conventional drill-and-blast headings will complete the remaining tunnel sections.
The back-loading cutterheads are the smallest ever designed using 19-in. disc cutters — a disc size that will allow for longer cutter life in hard rock. Geologic conditions are expected to consist of 200 MPa 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 cubic meters of water per second for use in domestic and industrial applications. Untreated water will be pumped from the Semantan River and will then flow via gravity from the intake structure to an outlet connecting basin and planned water treatment facility near Kuala Lumpur.
Desiree Willis is a technical writer for The Robbins Co., based in Solon, Ohio.