Effect of acid rain on geotechnical properties of composite fine-grained soil

Generally the atmospheric releasing gaseous pollutants like sulfur dioxide and oxides of nitrogen travels very far away from their sources. These gaseous pollutants combined with moisture in the atmosphere to form sulfuric acid and nitric acid solutions that fall to earth in rain is termed as acid rain. Though there is no significant record of acid rain in Bangladesh but it may be a happen due to the increasing urbanization, heavy industrialization, climate change and global warming. The main objectives in this study is to pridict the probable effect of acid rain on geotechnical properties of soil inorder to increase our understanding and taking proper consideration during construction of substructure. At first, the collected soil samples were treated with two different acid of varying concentration through three setups. After that, the geotechnical properties of original and treated samples were determined. These test result shows that the physico-chemical behaviours, free swell index and consistency of soil were strongly affected by acid treatment due to rapid leaching of cations and the diminution of inter-particle repulsion. Besides that the unconfined compressive strength (UCS) and shear strength parameters decrease with the addition of acid rain and their increasing concentration because of the changing of internal structural of soil and reduction of the electric forces as concentration of exchangeable cations reduced on acid treatment.