Alpine drilling: Liebherr machines heighten reservoir dam

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 8.5-metre 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 alpine location of the dam and the narrow access road make the jobsite logistics particularly challenging. For Züblin, one feature of the LB 45 in particular was decisive for using the Liebherr drilling rig for deep foundation work: the folding leader, which allows the overall length of the machine to be shortened for transport. This enables the company to master even tight bends and limited space in the tunnel area when transporting to the Wurtenspeicher.

Precision for demanding drilling work

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 22.5 metres and the diameter is 1,200 millimetres. 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 make the completion particularly challenging: highly abrasive material in the drill channel and the high strength of the rock. Züblin has to work very precisely, the work is subject to a reduced drilling tolerance and a maximum deviation of the bored pile wall of just 1 per cent.

The LB 45 has a maximum torque of 450 kilonewton metres and is designed for all common piling methods in deep foundation work. These include Kelly drilling, continuous flight auger drilling and double rotary drilling. For applications with full or partial displacement, the machine can reach drilling depths of 37 metres thanks to the optional lattice mast extension. This corresponds to an increase of 6 metres. The advantage of this is that customers can use a compact device for greater depths, even for geologically challenging drilling, and are therefore very flexible on the jobsite. The 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 extremely 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 Wurtenspeicher began in 2025 and will be completed this year. The planned time frames for the work must be precisely adhered to, as the alpine jobsite is subject to more intensive weather conditions and winter can arrive early at 1,700 metres.