STABILISATION OF OLD MINE WORKINGS – A CASE STUDY OF THE USE OF FOAMED CONCRETE IN COMBE DOWN STONE MINES

Stabilisation of old mine workings in the UK has become an issue in recent years due to deterioration of old mine workings and the pressure on available land for construction. The Combe Down Stone Mines, near Bath, are a major mining complex which are in need of stabilisation. About 600 properties and 1300 residents are affected and funding under the Land Stabilisation Programme has been granted. Foamed concrete has been selected as the prime material for infilling the mines for the current Emergency Works and for the future Main Scheme. The paper sets out some of the technical characteristics and justification procedures of foamed concrete as a stabilisation solution. It also describes the stabilisation process and discusses the challenges involved in development of an underground construction specification for foamed concrete, believed to be the first of its kind. The paper also seeks to look forward by drawing on the lessons learned to date in placing around 30,000 m3 of foamed concrete and the development of the material and specifications in the remaining works, which are expected to entail placement of some 400,000 m3 of foamed concrete over a four year period.