After the existing buildings had been demolished, the site was initially filled with sand, gravel and rubble. Below this layer lie older foundations and foundation remnants in various states of repair. In addition, the soil underneath the old foundations was likely to be contaminated, which is why the Fundex piles were used as a DIN EN 12699 displacement pile. Fundex piles are particularly suitable for contaminated soils, as they displace the contaminated material instead of excavating it. This saves on additional costs for transport and landfill disposal. The cramped building conditions caused by existing buildings and hydrogen pipelines also meant that the work had to be carried out with a high degree of sensitivity and forward planning. At the north end of the construction site, piles had to be installed in the immediate vicinity of the existing buildings in a gap between pipeline bridges and hydrogen tanks.
Extensive exploratory drilling to investigate and prepare the old foundations.
Before the piling work began, 197 exploratory holes were drilled to determine the exact location of the old foundations. The pile layout was then modified accordingly and the precise pile insertion points were defined. Drillings were then carried out at these points in order to break through the existing foundations.
A type BG28 rotary drilling rig with a drilling diameter of 880mm was used to locate the remains of the old building, sometimes down to a depth of 7m and through 5m of reinforced concrete, thus creating sufficient space for the construction of the Fundex piles.
The subsoil also proved to be extremely abrasive and heterogeneous. Very high torques over several metres were repeatedly observed in the drilling drive. A repair workshop was set up on site to prevent the work from being delayed due to the high wear and tear on the drilling rig. The drilling equipment was reconditioned on the spot, thus ensuring continuous use without any downtime.
Perfectly coordinated work flows
The piling work began while the pilot holes were being drilled. The work routes, storage areas and stake-out work had to be closely coordinated in order to allocate the available space on the construction site in such a way as to avoid downtimes for the machinery. This necessitated a parallel workflow for follow-up work on the spoil removal boreholes and preparation of the pile boreholes. A total of 182 Fundex piles with a diameter of 44/56cm were installed for this contract.