Studies on contaminated mine soil and its remediation using soil washing technique : a case study on soil at Kolar gold fields

Uncontrolled mining and the tailings produced can cause significant environmental impacts such as water, air, and soil pollution. In the present study, a contaminated soil of gold mines located in the Karnataka state of India was studied to know the geotechnical behavior of this soil as a foundation material and to suggest a suitable soil remediation technique to avoid contamination of surrounding water bodies. The in-situ dry unit weight of soil at the selected locations varied from 15.71 to 18.75 kN/m3. The effective shear strength parameters determined from Triaxial test results were in the range of 4.8 - 8.2 kN/m2 and 19.40 - 29.80, respectively, for the cohesion and angle of internal friction. The soil samples were analyzed for bearing capacity and settlement using GEO5 software tool, and the economical dimensions of the footings were estimated. It was observed that the soil has sufficient bearing capacity, and the settlements are within the allowable range. The chemical analysis of the soil samples showed that there are considerable amounts of heavy metals present in the mine soil. Though the strength of the soil is good, the contaminants in the soil may cause groundwater contamination and damages to the footings. Hence, the soil washing technique as a remediation technique was also studied through column leaching tests using different leaching solutions and found that diluted hydrochloric acid (HCl) with Ethylenediamine-tetraacetic acid (EDTA) can effectively remove the heavy metals from the soil.