Major tunnel boring on the Glendoe hydropower project in Scotland was completed early this month when the 5m diameter TBM holed through to complete the headrace drive.
The unshielded TBM was originally a Robbins build but was refurbished by Herrenknecht for Hochtief-Glendoe JV to excavate a 6.2km long headrace. The tunnel runs at 0.5% grade and then rises to a 11.7% incline. The contractor’s designer is Poyry.
Geology along the alignment comprised schist and quartzite rocks with strengths ranging from 30MPa-150MPa. The TBM started its drive in September 2006. Excavation support included rockbolts, shotcrete, mesh and steel liner ribs.
Other key excavations on the project undertaken by drill and blast included a 1159m long access bore, a 1780m tailrace tunnel, a water transfer tunnel, and a 47m long by 33m high by 19m wide powerhouse cavern (T&TI, April 2007, p21).
Work on the design and construct project started in early 2006, and tunnel excavation for the access tunnel started in May that year.
The 100MW scheme is being developed by the utility Scottish & Southern Energy (SSE). It said in a statement that the development requires an investment of more than US$280M, though the contract value was earlier stated as US$260M. The scheme is near Fort Augustus at Loch Ness, and is the first major hydropower project in the UK for decades.
