At the end of March 2008, the open-type hard rock tunnel boring machine of WIRTH – boring diameter 7.03m – successfully finished construction of the 3.7m long pressure gallery near Kaprun. The last 500m with a slope of 100% will be constructed by conventional method. With a peak performance of 40m/day, the TBM ate through the very demanding geology over a period of eight months, a geology requiring comprehensive securing measures, beyond.
The pressure gallery is part of the race for the new pumped-storage scheme Limberg II near to the existing power plant Glockner/Kaprun. This project is not only one of the largest jobsites of Salzburg, but also located in the alpine area at 2,000m level. Snow and the danger of avalanches affect the work. Access to the jobsite is only possible in the summer time. These special criteria required a TBM that could be transported in smallest units, at low weights and dimensions to its destination in the alpine area; conditions the hard rock tunneling machine of WIRTH fulfilled perfectly. It was assembled within three months on the site and started working.
After its disassembly within time schedule, directly in the tunnel, the TBM now waits for its next job. Before boring Limberg II, the machine was already operative in several other projects. The first job was in the Lohberg mine (Germany) in 1988 where it bored three sections of 3,800m, 1,700m and 2,600m, at a diameter of 6.80m. In 1999, the machine bored a sewage tunnel of 9,000m length, in Sydney, Australia, at diameter 6.56m. After its refurbishment when a new main bearing assy. including driving pinions were installed, the TBM bored a distance of 8,500m at 6.70m diameter for a water tunnel at Ermenek, Turkey.