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Raft rescue

FOUNDATION CONTRACTOR Roger Bullivant is in the middle of an underpinning contract for a Victorian house in Seagrove Bay on the Isle of Wight .

Working for project manager Cunningham Ellis & Buckle, which designed the remedial works, the firm is using a Klemm 701 rig to install 80,250mm diameter auger bored piles to 12m depth through difficult and varied ground conditions.

These will support a concrete raft in tended to remedy the structure's subsidence-related instability.

The three-storey house, built in 1890, sits immediately behind the esplanade and sea wall.It is underlain by disturbed variable soil and an 'extremely variable sequence'of sand, sandstone and fissured clay of the Osbourne and Headon Beds.

Temporary casing is being used to provide stability in the saturated sand above the stiff clay to depths of 10m.Substantial bands of sandstone also have to be penetrated at some locations .

Roger Bullivant says that while the Klemm rig is able to cope with the variable ground, the restricted access has made for an interesting challenge.The rig can auger up to 450mm diameter piles down to 22m, in headroom of just over 3m.

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