PENNINE VIBROPILING has carried out three major ground improvement schemes for distribution centres next to the East Coast Main Line at Doncaster in northern England.
More than 11,000 vibro stone columns have been installed using top feed HD150 vibroflots for the buildings. Two are for shipping firm P&O (built by main contractor Tolent) and one is for Power Europe (built by Simons).
Pennine's work was worth £0. 4M.
Site geology is up to 2m of engineered sand fill overlying a band of cobbles. This is underlain by soft to firm clays grading into loose to medium dense silt and clay sands. SPT 'N' values of the sands range from 8 to 15 increasing to more than 30 at depth.
As the warehouse units will be used for high bay racking, a very tight settlement specification was imposed by consultants Bullen and White Young Green.
Pennine's vibro schemes were designed to limit settlements to less than 25mm with floor slab loads locally up to 100kN/m 2. Pad foundations were designed to carry 200kN/m 2and tight angular distortion constraints of 1 in 1000 were also required.
Pennine technical manager Marc Evans said the vibroflots were powerful enough to penetrate the compact upper fill without preboring and successfully densified the sand.
'Zone test results showed settlements as low as 6mm at one and a half times the design bearing pressure, ' he said.