DURING PILING for the Environment Agency's Burton-upon-Trent flood alleviation scheme in Staffordshire, Taylor Woodrow Construction's spec- ialist geotechnical operation, Foundation Engineering, had to overcome a number of logistical and conceptual problems.
Work was divided into three sections, the biggest challenge being the middle section, which involved building a new river wall. Two pile types were initially proposed, 900mm diameter rotary bored king piles extending down into weak to moderately strong mudstone and 600mm diameter CFA piles, only 2.5m long, protect- ing the river bank in-between.
However, work was complicated by an existing low-level river wall. For stability reasons, the mast foot on a CFA rig needs to be placed immediately beside the pile position, which meant the rig would have had to straddle the low wall.
And while rotary piling rigs, which are more stable on their base carriers, could work over the barrier, they were not economic for the shorter, 2.5m long protection piles which made up the majority of the job.
Instead Taylor Woodrow pumped concrete down the centre of the kelly bar so that it could form 'hybrid CFA' piles using modified rotary equipment mounted on a Casagrande C50 base carrier.
Taylor Woodrow estimating manager Mike Tate said: 'Working in close liaison with main contractor May Gurney (Construction) and consultant Sir William Halcrow & Partners, positional tolerances were resolved on a revised config- uration that satisfied both build- ability and design requirements.'
The most southerly and final section is due to finish next month. Here piling is being carried out from a berm pushed out into the river to avoid the river wall.