Permanent anchor for the load transfer of the crane runway support
Since fall 2023, PORR Tunnelbau has been constructing a cavern and tunnel system on behalf of EnBW Energie Baden-Württemberg AG for the conversion of the Rudolf Fettweis plant in Forbach into a pumped storage power plant. A crane runway is being installed in the underground power plant cavern, which will be used to transport materials both during construction and later during operation. This has to be anchored back into the rock for permanent load transfer. For this purpose, PORR Spezialtiefbau produced 50 four-strand permanent anchors with double corrosion protection and a grout body length of 3 meters for a total length of 18 meters. They were drilled into the rock with a 27-degree incline at a starting height of approx. 5.5 meters.
Drilling with a water hammer reduces dust exposure and wear
The Klemm 806 GS drilling rig, which is specially adapted for upward drilling, and a water hammer were used. This hydraulic hammer drill uses clear water instead of compressed air as the drive medium. Although the process requires more effort in terms of water logistics, the advantages over dry drilling methods far outweigh the disadvantages. On the one hand, emissions are very low as no dust is produced, and on the other hand, drilling can be carried out more efficiently. Last but not least, wear on the drilling tool is significantly lower due to permanent cooling and constant flushing with water. To ensure the water supply, there are two fresh water reservoirs in the cavern that are permanently filled with water. The river water is pumped into a storage tank via a settling basin and filtered before being fed into the drilling rig.
Benedikt Lohoff, site manager at PORR Spezialtiefbau, is pleased with how the team overcame the challenges of working underground: “The available space was extremely limited and the noise levels were also high in some places, despite the use of hearing protection. In addition, the changing operation of the large equipment and transport vehicles required the full attention of everyone involved at all times. Thanks to the close coordination between the trades and a sophisticated occupational safety concept, we were able to complete the work safely and on time.”
