The Wirth gripper TBM driving the 3.9km inclined headrace for the Limberg II hydro project, in Austria, has holed through on schedule.
The 7.03m diameter open TBM was refurbished and overhauled for the contract, which required it to bore through basalt and gneiss at a 45° (degree) incline. The rock was of average UCS 100MPa but was locally higher, reaching 150MPa.
Much of the length of the tunnel was unlined, having a minimum excavated diameter of 7m, but shotcrete was used in parts.
An excavation period of nine to 10 months was planned for the drive, which began in August last year following some delays due to weather conditions at the high altitude site. The TBM holed through in April.
Prior to the project the TBM was used on the Ermenek hydro project, in Turkey, and the North Side Storage sewer scheme in Sydney, Australia – where it has a smaller, 6.7m diameter for both projects.
