Effect of sand mixing on the geotechnical properties of black cotton soil

Abstract

Black cotton soils exhibit high swelling and shrinkage characteristics, causing several challenges in civil engineering applications involving such soils. Stabilizing black cotton (BC) soil with sand as a sustainable engineering approach offers several advantages for soil improvement and environmental conservation. This study aimed to investigate the effect of mixing sand on some of the geotechnical properties of a BC soil. The soil samples were mixed with 10%, 20%, and 30% sand by weight and tested for sieve analysis, specific gravity, Atterberg limits, compaction, permeability, and swelling characteristics. The results showed that with increasing sand content, the specific gravity, liquid limit, and plasticity index of the soil decreased significantly. The plastic limit also decreased but to a lesser extent. The maximum dry density increased and optimum moisture content decreased with increasing sand percentage. The sand mixing improves the workability and strength characteristics of the expansive BC soil. Up to 30% sand mixing caused over 50% reduction in liquid limit and plasticity index. Around 70% reduction in swelling pressure was noticed with a noticeable increment in the permeability. The study demonstrates that sand mixing can be an effective ground improvement technique for BC soil.