Moving through mountains at Jinping II power station

16 April 2007

A Robbins Main Beam TBM will bore through a steep mountainside on the Jinping-II hydro power station in Sichuan Province, China

Once completed in 2010, Jinping-II will be the largest power station in an ambitious 21-station project for Ertan Hydropower Development Co. Ltd. The project will harness up to 25,000GW per year from the Yalong river for China's West-East Electricity Transmission Project. Power from these stations and other resources in the west will be transmitted to Guangdong, Jiangsu, and Zhejiang Provinces, as well as the cities of Shanghai, Beijing, Tianjin, and other eastern locations in short supply.

The Jinping-II station will use a 150km long natural drop in a bend of the Yalong river to generate 4800MW of electricity per year. Jinping-II is located 17km downstream from the Jinping-I station, which is slated for completion in 2014 and will have a generating capacity of 3600MW.

On 1 March 2007, Robbins signed a contract with Ertan Hydropower Development Co for delivery of the 12.43m diameter TBM, backup, conveyors, cutters, and related components for the project.

The Jinping-II station will use four parallel 16.7km headrace tunnels to generate electricity. Robbins will bore headrace tunnel 1, while headraces 2 and 4 will be excavated by drill and blast. All four tunnels are located in a complex geology of marble, shale, and limestone with up to 80MPa (11,600 psi) UCS. The high overburden, up to 2500m in height, creates a risk of squeezing ground, while faults and fractures as well as karst patterns revealed in the adjacent access tunnel and probe tests indicate the potential for high water inflows.

Robbins and Ertan Hydropower Development Co plan to begin boring on the 16.7km long headrace tunnel in March 2008 after an onsite assembly. Engineering and fabrication of key components will take place in Robbins' US locations, while much of the steel structure will be coordinated for fabrication at the Robbins China manufacturing facility in Shanghai. Assembly will take place in January 2008 in an underground launch chamber pre-excavated by drill and blast.

In order to bore successfully in the challenging ground conditions, Robbins designed the machine for a variety of situations. The entire TBM, backup, and continuous conveyor setup in the tunnel will be raised in order to allow the expected large water inflow of 5m3/sec to pass under the back up. In addition, a water discharge pump will relay water from the cutterhead support to the end of the backup. Reserve saddles located under the gage area on the TBM cutterhead will allow for overboring if squeezing ground is encountered.

Although Ertan's entire hydro power scheme will not be finished until 2030, the construction of the Jinping-II station is a feat in its own right. 'This is one of the biggest TBM-driven tunnelling projects in Chinese history,' said Biyue Li, Chief Operational Officer-Far East for Robbins. 'This is one of many ongoing projects for the country. China is currently one of the leading TBM markets, and will be for at least the next 5-10 years.'

Excavation of headrace tunnel #1 will begin on a mountainside with up to 2500m overburden headrace tunnel The Jinping-II hydropower station will utilize a natural drop in the Yalong River to generate 4800 MW annually. Yalong River The mountainous region required specific design modifications to the TBM in case of squeezing ground and water inflows mountainous region Author Info:

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mountainous region mountainous region
Yalong River Yalong River
headrace tunnel headrace tunnel

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