Desiree Willis, Technical Writer, The Robbins Company

Robbins main beam TBM

An extensive hydroelectric project in northeast Turkey will employ a Robbins main beam TBM at two different tunnel diameters. Launched in winter 2008/2009, the 4.8m (15.8ft) diameter TBM and back-up is excavating a series of headrace tunnels for contractor Kolin Construction Co Inc.

The TBM, for the Akköy II Hydroelectric Project, is utilizing 19in cutters to bore a series of three tunnels in sub-volcanic rock, granite, and rhyolite. The initial 6.7km (4.2 mile) tunnel, at 4.8m (15.8ft) diameter, will be followed by two additional tunnels at 4m (13ft) diameter and measuring 4.8km and 4km long.

Diameter change will require removal of the outer cutterhead sections, bottom and side supports, roof shield, dust shield, and gripper shoes. The components will then be replaced with 4m (13ft) diameter adaptations before the machine is transported to the smaller tunnel sections.

Differing tunnel diameters were designed into the massive Akköy II hydropower scheme. One of the 4m (13ft) diameter tunnels will transfer water from several sources to the main Gökçebel Reservoir, which is capable of holding over 100 million m³ (3 billion ft³) of water. The 4.8m (15.8ft) diameter tunnel will transfer water from the reservoir to the Yaşmaklı Dam site, a concrete gravity dam 100m (328ft) high. From there, water is sent through the second 4m (13ft) diameter tunnel to a surge chamber at the Akköy II power plant located on Harşit River.

Kolin is undertaking the construction works for Akköy Energy AS, which owns the license for the project according to the Electricity Market Law in Turkey. Once complete, the Akköy II Hydroelectric Project will supply 898 million kWh annually to the national grid at a 154kV voltage level. The new project will add to the current 315 million kWh supplied by the Akköy I Hydroelectric Project. The Akköy I project has been completed and is in operation, also generating energy by diverting water from the nearby Harşit River.

www.RobbinsTBM.com
Kolin Construction Co Inc.