Robbins is to supply a single shield TBM to bore the headrace for the Theun Hinboun enlargement project in Lao PDR.
The 7.6m diameter machine has been designed for squeezing ground conditions with an articulated cutterhead to drive the 5.5km long tunnel for the hydro project. Robbins is assembling the shield in Ohio for shipment in July to Italian contractor CMC di Ravenna.
Geology along the alignment of the headrace comprises sandstone, siltstone and mudstone in alternative strata.
Tunnel lining will have 1.6m long rings (5+1) of 7.46m o.d. formed of 280mm thick segments. The finished diameter of the tunnel is to be 6.9m i.d.
Segment moulds and the carousel for the lining is being supplied by Italian firm Euroform, which is a subsidiary of Herrenknecht.
Cavico is building a 1km long starter tunnel and shaft for TBM retrieval (T&TI, February, p14).
The developer is Theun Hinboun Power Co, and the plant is to finished by 2012.