LOCATION: St Agnes, Cornwall

SWG were appointed ground investigation and geotechnical design engineer for the development of 12 high specification timber lodge houses perched on a mined steep valley side overlooking Trevaunance Cove, St Agnes. The site represents one of the biggest geotechnical challenges in the south west, with major issues including:

• Ground contaminated by both natural and mining processes
• Unrecorded mining voids including adits, shafts and lode stope workings
• Rock slope instability
• Fill slope instability
• Deep foundation requirements

Following detailed investigation, solutions designed to overcome these site specific problems have included:

• Inert capping layers to isolate contaminated fill
• Filling and grouting of worked stopes
• Capping of mineshafts
• Re-profiling fill slopes with geogrid reinforcement
• Supporting new cut slopes with soil nails and shotcrete or proprietary matting
• Supporting unstable rock slopes with anchors and heavy duty meshing
• Rock-socketed piling to support new structures

Mining features identified from historical records and photographs.

Typical geotechnical works included soil nailing, shotcreting and erosion protection associated with stabilising proposed plot.

Capping of mineshaft