MAY GURNEY Technical Services last month finished piling for a new waste incinerator on the Isle of Man, south of the capital Douglas.
The facility, designed and built by Kværner Engineering for the Manx Government, will alleviate the island's waste disposal problems. It is positioned in a hillside trough to reduce its impact on the surrounding countryside.
The £750,000 piling contract was to install 488, 400mm diameter and 28, 450mm diameter bearing piles to support the structure and a further 143, 750mm diameter contiguous bored piles to form a perimeter wall for a waste pit and ash bunker.
Site geology comprises a stiff boulder clay overlying Manx Slate. While the slate is an ideal material for the load bearing piles, it can be very hard, making it difficult to penetrate and build the bored pile wall.
The waste bunker excavation was 9m deep, so the contiguous bored pile wall had to be propped or anchored. May Gurney worked closely with Kværner to develop a solution using the waste bunker walls to provide a top prop to the piles, removing the need for any intermediate support.
The original plan was to have a 2m thick floor slab for the waste bunker to resist hydrostatic upthrust, as it is several metres below the water table. Instead, May Gurney proposed using permanent tension anchors to hold the base slab down, which meant the thickness of the slab could be reduced to 1m.