Understanding the effects of high temperature processes on the engineering properties of soils

High temperature processes such as in situ smouldering and thermal remediation techniques can achieve rapid removal of organic contaminants from soils in much shorter time periods than traditional remediation technologies. Thermal remediation processes use heat or heated water to volatilise the contaminant within the soil to enable its extraction. High temperatures affect the particle size distribution, mass loss, mineralogy and permeability of the soil. In sandy soils, the particle size decreases with increasing temperature due to a mobilisation of fines, which is likely due to the bond of fines to the sand grains being affected by temperature. In clayey soils, the overall particle size increases with increasing temperature due to aggregation and cementation of the clay fraction. Permeability seems to be affected by treatment type rather than temperature alone, comparing heat treated and smouldered samples showed an increase of sand permeability by approximately two magnitudes. This study illustrates the effects of high temperature and smouldering processes on soil characteristics and dynamic behaviour. Monitoring during and after aggressive remediation is advisable so that rehabilitation measures can be implemented before site redevelopment.