PENNINE VIBROPILING, the new licensee for the BSP/Amec developed rapid impact compaction, has used the method for an extension to an Ikea store in West Thurrock, Essex.
The system, designed with consultant Rolton Group, was chosen because of low levels of contamination on the site. Rapid impact compaction produces no spoil but conventional ground treatment methods would have involved spoil disposal at 'prohibitive' cost.
The 2,700m2 site is underlain by up to 5m of generally compact but locally loose mixed granular and cohesive fill, overlaying chalk.
Pennine used three different piling techniques on the 10-day contract. The rapid impact compaction was carried out inside a perimeter of driven precast concrete piles and vibro-compacted stone columns were used to treat the 12m wide 'vibration exclusion zone' between the site and the existing store.
Geophone monitoring stations were used to monitor vibrations. Peak particle velocity 10m from the rig was between 8mm/s to 9mm/s, lower than traditional dynamic compaction.