Coal Bottom Ash as an Anthropogenic Soil to Prevent Soil Erosion during Post Mine Rehabilitation in Sri Lanka

The clay mines are abandoned due to the higher cost and non-availability of suitable fill material creating severe environmental issues. Coal bottom ash (CBA) is an industrial waste by-product generated in coal power plants and open dumped which causes soil and water pollution. Hence, CBA is a potential anthropogenic soil for post mine rehabilitation. Soil erosion is one of the major environmental problems in post mine land with the change in soil conditions, mainly in the tropical countries like Sri Lanka. Therefore, main objective of this study is to evaluate the potential of CBA to prevent soil erosion in the post mine land. The engineering properties of the samples were evaluated, and annual soil loss due to rainfall was measured by artificial rainfall test for six different CBA and soil mixtures. CBA exhibits high potential to prevent soil erosion with higher permeability and water holding capacity values. The annual soil loss is very low when the fine fraction of the CBA-soil mixture is lesser than 20%. Further, soil erosion can be significantly reduced when CBA fraction of the CBA-soil mixture is greater than 75%. Interestingly, the micropore structure of CBA is significantly influential on the soil erodibility.