FOUNDATION CONTRACTOR Abbey Pynford had to cope with difficult ground, restricted headroom and a fast-track programme for a piled basement wall at a satellite manufacturing facility in Hatfield, Hertfordshire.
Astrium builds satellites for the Arianne space project. New equipment meant it needed a larger floor to ceiling space. The solution was to build a huge basement pit beneath the building to give the headroom required. The site is underlain by boulder clays with water-bearing sand lenses and it was decided to temporarily support the excavation with a 6.9m deep contiguous bored pile wall.
Fast-track construction was required to meet the deadline, so the wall was designed with minimum propping.The capping beam acted as the top support with a single prop at depth.
Tolerance specification for the wall was high and Abbey Pynford had to use down-the-hole hammers and coring to penetrate the boulders locally. The sand lenses also posed difficulties, with excess grout migrating through them and obstructing the path of adjacent piles. In places it was necessary to core through the grout to install piles.