CAN stabilises historic Fort Bovisand

Geotechnical engineering specialist, CAN Geotechnical Ltd, has been awarded the contract to undertake geotechnical stabilisation work at Fort Bovisand, Wembury, UK, bringing both its specialist access capability and drilling expertise to the redevelopment of the historic 170-year-old Victorian fort.
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CAN will use its in-house designed ‘A-Frame’ cliff-mounted drill rigs for a soil nailing job at Fort Bovisand in Devon

The development is a heritage structure in need of serious renovation before it can be fully restored in a sympathetic and sustainable development, which will include an events space, a bistro, a visitors' centre, and 81 apartments/houses. The development company, Fort Bovisand Developments Ltd, is chaired by Greg Dyke - former BBC TV director general - who has broad leisure and hospitality experience in the region.

The critical first element to the overall project is stabilising two gullies immediately beneath the access road leading into the Fort complex running along the top of coastal cliff faces, with each location requiring specialist equipment and work at height experience. The project's geotechnical designer, Red Rock Geoscience Ltd, has specified a soil nail and facing solution, to stabilise the gullies and prevent further erosion undermining the access road.

The Eastern gulley will have 195 R32 stainless steel soil nails installed in a grid pattern over the cliff face, while the Western gulley needs 127 of the same type of soil nails, and both gullies will be faced with steel netting and erosion matting.

CAN's approach is to use an excavator-mounted hydraulic drill rig to install the upper bolts of the netting system, and to drill the rows of soil nails in the face of the crest.

Temporary anchors will then be installed and used to suspend CAN's in-house designed ‘A-Frame' cliff-mounted drill rigs. These A-frames enable the drill crews to move the rigs to each soil nail location on the cliff face using winches, which they access by abseiling down on to the cliff face and working suspended from ropes to undertake the drilling.

On completion of CAN's works, a marine contractor will install a rock protection system at the base of the cliffs to protect from future wave action, and repair to a shoreline defensive wall. The combined stabilisation measures will allow the current temporary weight limit to be removed from the access road, enabling the main redevelopment works to begin with safe, unrestricted access to site.

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