A tunnel boring machine has broken through 7.8 km of rock in preparation for construction of Turkey’s 104-MW Kargi hydroelectric plant, manufacture Robbins Co. said.
The double-shield machine has a diameter of 10 meters and was launched with contractor Gulermak in Spring 2012. The plant was originally scheduled to open by the end of this past year, though difficult geological conditions forced Robbins’ engineers to make major in-tunnel modifications throughout the tunneling process.
“In the first two kilometers of boring, a total of seven bypass tunnels were needed to free the tunnel boring machine (TBM) from collapsed ground,” the company said in a release. “The cutterhead stalled on numerous occasions as the conditions varied widely from sold rock to running ground.
“Small and wide faults along the alignment added another level of complexity, as the excavation was located very close to the North Anatolian fault line in Turkey’s relatively recent rock formations.”
Modifications to the TBM include a custom-built canopy drill and positioner, which allowed pipet tube support installation through the machine’s forward shield. 90-millimeter-diameter pipe tubes drilled a distance of up to 10 meters ahead of the cutterhead provided extra support across the tunnel crown, while resins and grout were injected at the crown to prevent collapse.
Gulermak said the modifications allowed for the measurement and back-fill of cavities above the cutterhead, and the detection of loose soil seams and fractured rock in front of the face.
HydroWorld.com reported in November 2010 that the Kargi plant will be operated by Norwegian power company Statkraft A.S., with Voith Hydro contracted to supply complete electromechanical equipment.
The plant is located in the Corum province and will utilize water from the Kizilirmak River.
For more new development news, visit here.