Storage tanks were installed below ground and formed part of the hangar's fire suppression system, storing the waste foam pumped from the hangar area. Due to high groundwater, the design of the tanks needed to consider the potential for uplift when the tanks were empty. Thus the design incorporated a 400mm thick reinforced concrete base slab to remove the flotation risk with each of the tanks tied to it with restraint straps. The open cut excavation depth approximated 6.5m and our geotechnics team carried out stability checks and temporary works design to support this phase.
The bearing pile arrangement included 600mm and 450mm diameter piles which used Continuous Flight Auger (CFA) methods into the weald clay underlying the site. The loads on the piles varied significantly, with many being subjected to high horizontal loading. Using our extensive experience of pile design, we provided a cost-effective design, which met the tight settlement criteria required for each pile. The project team also undertook a range of temporary works design, including working platforms for piling rigs and mobile cranes.