To ensure that the supply of drinking water in the Greater Strasbourg area (France) is guaranteed in future too, the supply line of a new well is connected to the pipeline network of the city of Plobsheim. The construction project "Champ captant d'alimentation en eau potable au sud de l'aglomération Strasbourgeoise" ("Drinking water production in the south of the metropolitan area of Strasbourg") includes four underground pipe jacking drives. In Plobsheim, these sections are between 50 and 215 meters long and run under the groundwater level.
Due to the water-bearing ground conditions in coarse gravel and sand, typical of the plains in the upper Rhine valley, the contractors opt for a slurry-supported AVN machine from Herrenknecht. The AVN M-1188M has already been used in several projects. For the pipe jacking drives in Plobsheim, the machine is comprehensively refurbished and adapted to the requirements of the project at Herrenknecht's Schwanau headquarters. Amongst others, the TBM modifications include a larger diameter of 1.740 mm and a new mixed-soil cutterhead.
The longest drive at 215 m runs directly under a busy highway. In order to avoid damage to the infrastructure, pipe jacking operations have to be constant. Otherwise, if the TBM stands still for longer periods, minor heaves or settlements can occur on the surface. In 2-shift operation, the drive under the highway is carried out without interruptions. After less than a month, the machine reaches the target shaft. By the end of October 2017, the experienced tunnelling crew masters the three other drives with a total of 255 meters of tunnel. Since the beginning of 2018, the new well is connected to the pipeline network and supplies the inhabitants with drinking water.