KELLER GROUND Engineering last month finished a 'mess-free' displacement piling contract for an extension to a 10,000m 2 industrial unit in Croydon, south London.
The work, at both ends of the building, will convert it into a vast data storage centre. Originally a landfill, the site is part of a large distribution centre in Beddington Lane. It is underlain by up to 8m of household refuse over London Clay.
To avoid spoil removal and contact with the landfill material, Keller is using what it claims is a mess-free driven displacement piling system.
This involves site workers driving to depth a heavy duty steel tube fitted with an expendable shoe. They then place full-length steel before adding concrete and vibrate out the drive tube while the concrete is tamped in place.
Keller business development manager Derek Taylor said: 'The big advantage is there is not a teaspoon of arisings created.'
The 500, 380mm diameter displace ent piles are installed through the refuse and found in the clay at depths up to 16m.
Keller said the system's heavy driving capability can hammer past any obstructions and reduces the risk of material removal by excavation.
Some of the new piles provide the foundations for a 1000t capacity mobile crane being used to load in the equipment for the data centre.
The site has been covered by a permanent concrete hard standing so 500mm square holes were needed at each pile location.
'In these contaminated soils the concrete slab makes the ideal piling platform, ' says Keller foreman, George Wagstaff. 'Even though it slopes away from the building, all we have to do is adjust the verticality of the leaders at each pile position.'
Keller also installed the piles for the original building. The subcontractor rst reduced site levels by up to a metre using dynamic compaction and then put in about 2500 driven cast-insitu piles.