Getting equipment to a project 1700m above sea level is no mean feat and requires significant planning, not least the sourcing of equipment capable of being easily transported up a mountainside.
That's what German construction company Züblin Spezialtiefbau found when it was contracted to work on Fragant‘s hydro plant on the Wurten reservoir in Carinthia, a sparsely populated Austrian state in the Eastern Alps, noted for its mountains and lakes. Thankfully, Liebherr had a drill rig fit for the task.
The expansion of the reservoir, a central storage facility for one of Fragant's ten run-of-river, storage, and pumped-storage hydro power plants in the Möll Valley, will see operator Kelag increase water storage volume from 2.7m3 to 5m3, requiring an 8.5m increase in the reservoir's water level and a widening of the Wurten dam.
The reservoir has been drained and emptied but the alpine location and narrow access roads make the jobsite logistically challenging.
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For Züblin, one particular feature of Liebherr's LB 45 drill rig proved to be a deal maker: the folding leader, which allows the overall length of the machine to be shortened for easier transportation. enabled the company to navigate the tight bends and limited space when transporting the rig to Wurten. Züblin is deploying the rig to install pile foundations using the Kelly drilling method. Depending on the soil layer, the drilling depth could be between 2.7 and 22.5m with 1200mm diamater.
Bored piles
Over the course of the project, Züblin will install 2800m of bored piles. The secant pile wall, which will seal the subsoil of the dam, consists of 167 piles and binds completely into the bedrock along the entire area, making it necessary to adjust the length of the reinforcement.
Geological conditions make the job particularly problematic, given the highly abrasive material in the drill channel and the high strength of the rock. This means Züblin has to work to a reduced drilling tolerance and a maximum one per cent deviation of the bored pile wall.
With a maximum torque of 450kNm, the contractor found the LB 45 suitable for all common piling methods in deep foundation work, including continuous flight auger drilling and double rotary drilling.
Overload
The rig's new overload protection of the Kelly winch ensures that the locked Kelly bar automatically stops the crowd winch if the maximum permissible load of the Kelly winch is exceeded. The rope length measurement of the auxiliary winch measures the length of the unwound rope, which is helpful when inserting reinforcement cages, for example.
Züblin is using a Liebherr HS 8070 HD duty cycle crawler crane for lifting work on the jobsite.
The deep foundation work on Wurten began in 2025 and will be completed this year, despite tight time frames due to the Alpine weather.
"Maintaining these highly versatile [hydro power] plants and improving their efficiency during upgrades is one of our core tasks," said Christian Rupp, Kelag's Head of Generation and Technical Services, in March last year, at the start of the maintenance project.
Kelag is monitoring the area to ensure ecological impact is kept to a a minimum. Two probes will continuously monitor the water quality in the Fraganter Bach and the Möll river.
