Liebherr rig tackles challenging Austrian dam expansion

Züblin is using the LB 45 drilling rig to install pile foundations using the Kelly drilling method on the alpine jobsite. Image: Liebherr

The expansion of the Wurtenspeicher reservoir aims to optimise the energy management of the Fragant power plant group. Increasing the storage volume from 2.7 to 5 million cubic metres of water means that the operator can act more flexibly and efficiently.

The project includes an 8.5m increase in the reservoir’s water level and a widening of the dam body. To carry out these measures, the reservoir must be completely emptied.

The company Züblin is carrying out the project, with the alpine location of the dam and the narrow access road said to be making jobsite logistics particularly challenging. The total height of the dam is 1,700m.

Züblin is using the LB 45 drilling rig to install pile foundations using the Kelly drilling method on the alpine jobsite. Depending on the soil layer, the drilling depth is between 2.7 and 22.5m and the diameter is 1,200mm.

In the course of the project, the company will install a total of 2,800 metres of bored piles. The secant pile wall, which is sealing 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 at short notice.

Geological conditions are said to be challenging and the work is subject to a reduced drilling tolerance and a maximum deviation of the bored pile wall of just 1%.

The LB 45 has a maximum torque of 450 kilonewton metres and is designed for all common piling methods in deep foundation work. For applications with full or partial displacement, the machine can reach drilling depths of 37m thanks to the optional lattice mast extension, which corresponds to an increase of 6m.

The deep foundation work on Wurtenspeicher began in 2025 and will be completed this year. The planned time frame must be adhered to, as the alpine jobsite is subject to more intensive weather conditions and winter can arrive early at 1,700m, making work impossible.