Robbins single shield TBM for Laos headraceItalian company CMC (Ravenna) will use a Robbins Single Shield TBM to construct the 5.5 km-long headrace tunnel for the Theun Hinboun expansion project on the Nam Theun river, the largest tributary of the Mekong river. The 7.6 m-diameter machine is being assembled at The Robbins Company in Solon, Ohio, US for shipment in July, 2009. Electricity from the plant will supply neighbouring Thailand. The Robbins TBM is designed for squeezing ground conditions and features an articulating cutterhead with overcutters capable of cutting 100 mm beyond nominal tunnel diameter. The tunnel alignment is in alternating strata of sandstone, siltstone, and mudstone. Continuous lining will comprise 280 mm-thick precast concrete segments in a 5+1 arrangement for a finished tunnel diameter of 6.9 m. The new hydro station is scheduled for completion in 2012. For more visit tunnelbuilder archive la/11, www.robbinstbm.com and www.cmc.coop. 19/09.