Review: September 2023
In Grafenbrück, a road bridge crosses the lock chamber. This will remain in place during the construction work. It was therefore necessary to divide the excavation pit with a bulkhead wall in order to separate the lock area below the bridge and carry out the demolition in stages, starting with the lock chamber. In the bridge area, so-called HDI columns(high pressureinjection) were inserted into the ground prior to demolition. These serve to consolidate the subsoil and prevent the existing bridge from subsiding.
In the production of HDI columns, the injection material (cement suspension) is injected into the ground at high pressure through nozzles at the lower end of the boom. By rotating and simultaneously pulling the rods, uniform columns are produced in the ground.
