Three Robbins Main Beam TBMs completed excavation of Southeast Asia’s longest tunnel in 2014.
Malaysia’s capital Kuala Lumpur is a humid tropical metropolis with millions of inhabitants, but fresh water is still in demand. A new tunnel was commissioned by the Malaysian Ministry of Energy, Green Technology, and Water (KeTTHA), drawing water from the rainforest river Semantan and into the capital to address projected shortages for domestic and industrial use. In 2014, three 5.23 m (17.16 ft) Robbins Main Beam TBMs successfully completed excavation of the Pahang Selangor Raw Water Tunnel, also the longest tunnel in Southeast Asia. The massive 44.6 km (27.7 mi) long tunnel passes through the Titiwangsa mountain range under cover as high as 1,246 m (4,087 ft) and below geothermal features including hot springs.
Given the highly variable conditions including hard granite up to 200 MPa UCS, multiple fault zones, and quartz dykes, three separate TBM drives were proposed. Sections of NATM near the inlet and outlet portals were also utilized in sedimentary rock and granite. KeTTHA selected Shimizu Corporation and Nishimatsu Construction of Japan, along with local companies IJM Corp. and UEM Builders Bhd. (SNUI JV), as the contractor. The decision to use Robbins TBMs for the majority of tunneling was a clear one for the JV: “The open-type Main Beam TBM is number one in the world. I have used other machines, but this design is simpler and easier to use, and more powerful,” said Mr. Nakano, Deputy Project Manager for the SNUI JV.
All TBMs recently completed tunneling for this extensive project. The first TBM excavated 11.2 km (7.0 mi), and broke through in March 2013. The other two machines excavated 11.3 km (7.0 mi) and 12.0 km (7.5 mi) and met in the tunnel in mid-February 2014. “This is something we all look forward to in the tunneling industry,” said Robbins Field Service Manager, Andy Birch. “We get through all of the hard work and eventually we break through. It’s a great feeling, and I’m very happy for this joint venture and for Robbins.”
The machines maintained excellent advance rates throughout the project despite many challenges including fault zones, variable rock conditions, high rock temperatures, and frequent electrical storms that required machine stoppage. Due to the hot springs, water ingress at temperatures up to 56 degrees Celsius (133ºF) was recorded. Maximum rates of 49 m (161 ft) in one day, 198 m (650 ft) in one week, and 657 m (2,156 ft) in one month were nonetheless achieved — good rates that were at least partially attributed to the early installation of fiber mortar shotcrete as primary ground support. The near-zero rebound system, with its quick set time of 30 minutes, saved a significant amount of time compared to conventional ground support methods. Developed by Japan-based Denka and MCM, the project is the first time the material has been used outside of Japan and was able to successfully stabilize tunnel walls even in loose and collapsing ground.
High-tech design was also a factor in project accomplishment. To tackle the high cover and tough geology, all machines were equipped with custom back-loading cutterheads and durable large diameter cutters – the smallest diameter cutterheads to ever be outfitted with 19-inch cutters. The machines also had streamlined operator’s cabs with touch screens and wireless operation, able to stream data to site offices and to a project website for worldwide analysis. Behind each machine, Robbins continuous conveyor systems moved muck efficiently from the machine face.
Along with custom design and innovative ground support, the assistance provided by Robbins was integral to the project’s success. “The Field Service team was good and supported us on our project,” said Mr. Ohashi, Mechanical Engineer for SNUI JV at the breakthrough of the first TBM, “I am pretty happy [with the result]”.
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