Robbins Single Shield will Carve Laos Headrace Tunnel

May 11, 2009

Powering up neighboring nations will get a bit easier with a new hydroelectric project in Laos. The station, on the Nam Theun River, will include a 5.5 km (3.4 mi) long headrace tunnel constructed using a Robbins Single Shield TBM. The 7.6 m (25.1 ft) diameter machine, for contractor CMC di Ravenna, is being assembled at Robbins’ Solon, Ohio, USA manufacturing facility. The Single Shield will be ready for shipment in July 2009.

The Theun Hinboun Expansion Project will double generating capacity of the current scheme from 220 MW to 440 MW. The station will draw water from the Nam Theun River, the largest tributary of the Mekong, in conjunction with the existing Theun Hinboun power station built by CMC di Ravenna in 1998. Electricity from the plants will be sold to neighboring Thailand, where current power supplies are struggling to meet demands.

The Robbins TBM has been designed for squeezing ground conditions and will feature an articulating cutterhead with overcutters capable of cutting 100 mm beyond nominal tunnel diameter. Ground along the tunnel alignment consists of alternating strata of sandstone, siltstone, and mudstone. Continuous tunnel lining will support the ground conditions, using 280 mm (11 in) thick, pre-cast concrete segments in a 5+1 arrangement for a finished tunnel diameter of 6.9 m (22.6 ft).

CMC di Ravenna will construct multiple structures on the project for owner Theun Hinboun Power Company, Ltd.--a joint venture of the Laos Government, Norwegian contractor Statkraft, and GMS Power of Thailand. CMC will build a 1,000 m (3,280 ft) long starter tunnel and a 45 m (148 ft) deep shaft for TBM retrieval. Other construction works include a 65 m (213 ft) high regulating dam about 20 km (12 mi) upstream of the existing Theun Hinboun station, a new water intake, and a 1 km (0.6 mi) steel penstock. The new station is scheduled for completion in 2012.

The Robbins Company
Brianna Home
29100 Hall Street
Solon, OH 44139, USA
PH.: +1 253.872.4484

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