Decomposition and settlement in landfilled waste and other soil-like materials

The term ‘soil-like materials’ is used to refer to particulate materials that contain organic or other non-inert solids. When these materials decompose, there is a reduction in solid phase volume and an induced change in void phase volume, the combination of which has consequences for subsequent mechanical behaviour. Through a review of two laboratory investigations into decomposition in clay–fibre mixtures and three recent landfill settlement monitoring projects, this note seeks to elucidate a more fundamental mechanism of decomposition induced settlement.