Pennine Vibropiling used its Rapid Impact compaction system to improve ground for the new National Skating Arena being built at Attercliffe, near Sheffield.
Structural engineer Building Design Partnership decided that fused slag, mass concrete and relic slab obstructions in the 1.5-3m thick fill could be left in place and dynamic compaction used.
The tight programme meant main contractor HBG needed a foundation system that could be finished in 10 days. Pennine's system involves a hydraulic piling hammer applying between 10 and 30 blows to a 1.5m foot to form compacted columns. Surface depressions are topped up with granular material before a second pass. The number of impacts and depth of the resultant depressions are recorded by on-board instrumentation. Validation of the bearing pressure is carried out using small diameter plate and zone load testing.
At Sheffield, further savings were gained because compacted ground stood open, allowing simpler base slab construction.