The most interesting section is currently the tunnel construction work for the construction of the 400 m long and approx. 20 m deep connecting channel between the inlet collecting shaft and the inlet pumping station. The channel has an inner diameter of 2.80 m and consists of GRP pipes (glass fiber reinforced plastics) with 0, 10 m wall thickness.
The tunnel drilling begins at the inlet collecting shaft and ends at the main pumping station with an excavation depth of 26.20 m. The horizontal dimensions of the construction pit are approximately 29.20 m x 38.30 m.
The Herrenknecht drilling machine has an outside diameter of 3 m. The first 100 m of the tunnel have already been drilled and 13 pieces of pipes (3.75 m each) have been laid. The drilling progress was last about 10 m per day and the work is proceeding rapidly.
The shaft depth is 22.10 m, the inner diameter of the construction pit, which is enclosed in a ring by a bored pile wall, is 14 m (pile diameter 0.90 m, pile length 24.5 m). At the beginning of the drilling work, after drilling through the bored pile wall, the drilling machine hit sandy soil. According to the geotechnical report and existing drill profiles, it is expected to advance into rocky limestone shortly. The groundwater level is approx. 4 m below ground level. The drilling work must therefore be carried out under the appropriate water pressure.
A period of 6 weeks was planned for the drilling work.
The dimension of the construction work is impressive, behind it is a strong and competent team!