The contractor joint venture of Shimizu Corporation, Nishimatsu Construction, UEM Builders, and IJM Construction (SNUI) broke through the first of three 5.23m diameter Main Beam Robbins TBMs at the Pahang Selangor Raw Water Tunnel last month to a large ceremony of cheering onlookers. It was a moment worthy of celebration; the breakthrough is a significant step towards the completion of the longest tunnel in Southeast Asia, a 44.6km water transfer route from the states of Pahang to Selangor.
“This is a day we all look forward to in the tunnelling industry…it’s a good feeling when you get through all of the hard work and eventually break through,” said Andy Birch, Robbins Field Service Manager.
The breakthrough was attended by dignitaries, contractors and honored guests, with everyone very enthusiastic about the machine’s success.
Many challenges were overcome by the TBM and its continuous conveyor system on the 11km run, including blocky rock, over-break, power outages, extremely high rock temperature and water inflows.
Despite the variable conditions, the TBM maintained strong advance rates of 475m per month on average. “Advance rates at maximum were over 650m per month, that is 30m per day advance,” said Mr. Ohashi, Sr. Mechanical & Electrical Engineer for SNUI JV.
Various methods of support were used during boring, the primary being near-zero rebound fiber mortar (sprayed shotcrete). The Pahang Selangor project marks the first time that this innovative method has been used outside of Japan, and it has been very successful so far. Sprayed shotcrete can be applied during excavation directly behind the cutterhead support, which greatly reduces project downtime. The method also boasts the benefits of dust reduction and good bonding.
The two remaining 5.23m machines are currently boring respective 11km runs, and are on schedule to meet inside the tunnel in autumn 2013. Upon completion, the tunnel will transfer 27.6 cubic meters of water per second to a new treatment plant. The drinking water will supply about 7.2 million people for project owner KeTTHA (Malaysian Ministry of Energy, Green Technology, and Water).