Robbins TBM rises above water inflows in China

Jun 06, 2008

Deep in a sheer-walled canyon at the foot of China's Jinping Mountain, crews are working 24 hours a day to assemble a giant. The 12.4 m (40.1 ft) diameter behemoth, a Main Beam TBM manufactured by The Robbins Company, will excavate one of the country's largest hydropower projects to date.

Assembly of the Main Beam TBM and back-up system began in mid-April 2008 at the Jinping-II headrace tunnel #1.  A total of four headrace tunnels, two of them excavated by drill and blast and two by TBM, are needed for the Jinping-II Hydropower Station.  The tunnels will draw water from the nearby Yalong River, a tributary of the Yangtze.

The TBM is being built using a proven Robbins assembly process, known as Onsite First Time Assembly (OFTA). OFTA, without pre-erection in a manufacturing facility, will result in an earlier machine launch and reduced shipping risk and cost.  The benefits are particularly great because all of the heavy TBM structures have already been shipped from the manufacturing facility in Dalian, ahead of the low water season on the Yangtze River when such shipments are not possible.

The Robbins machine is currently being assembled onsite in an underground launch chamber for a startup later in 2008.  Most of the machine components are being staged in the town of Manshuwan, approximately 80 km (50 mi) away, due to limited space at the jobsite. As of May 2008, assembly of the machine is more than 40% complete. Crews have erected the cutterhead support and Main Beam, and are welding the 6 piece cutterhead.   Back-up construction will begin in a chamber behind the TBM later in May.

Special features on the TBM and back-up will accommodate a high expected water inflow of 4,000 liters per second (1,000 gallons per second).  The top of the back-up is arched over its entire length to allow for installation of water shields if high-pressure inflows are encountered.  A water discharge pump will relay any inflow from the cutterhead support to the end of the back-up.  Two TBM conveyors between the cutterhead and the tunnel conveyor were also designed for wet conditions. The conveyors are completely flat, rather than inclined, in order to prevent spillage of muck with high water content.

Another Robbins Main Beam TBM, at 7.2 m (23.7 ft) diameter, is currently being assembled for a water drainage tunnel at the site.  The ancillary tunnel will provide drainage to the main tunnel ahead of the 12.4 m (40.1 ft) machine.

Due to go online in 2010, the Jinping-II Hydropower Station will utilize the elevation drop in the  150 km (93 mi) long Yalong River to generate 4800 MW of electricity per year for owner Ertan.  Jinping-II is located 17 km (10.5 mi) downstream from the Jinping-I Hydropower station, which is slated for completion in 2014 and will have an annual generating capacity of 3600 MW.

Contact Information:
Brianna Home
Marketing Director
Direct: +1 253.872.4484

Desiree Willis
Technical Writer
Direct:+1  253.872.4490

The Robbins Company
29100 Hall Street
Solon, OH 44139

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