Permeability of compacted colliery spoil — a parametric study

Parametric studies were undertaken into the key factors affecting the hydraulic conductivity of a South Wales colliery spoil i.e. moulding moisture content, material properties, compactive effort, and confining stress. The studies were carried out in the context of the construction of a colliery spoil landfill liner. The moulding moisture content of the compacted colliery spoil was found to give the lowest permeability at approximately 1% wetter than optimum, a trend similar to that reported for compacted clays, while increased compactive effort led to reduced permeability. The particle size distribution from weathered samples of the spoil was typically found to be close to the idealised Fuller’s curve, with sufficient fines to generate an adequately low permeability; adjusting the maximum particle size (up to 50 mm) was not found to produce large variations in permeability. Finally, confining stress was found to have a significant impact on permeability particularly at low stress levels.