Smart Soil Solutions: Eco-Efficient Stabilization of Expansive Black Cotton Soil Using Geosynthetics

Whether lignite or black cotton soil, they are so expansive that they pose significant challenges to geotechnical engineers due to their high swelling capacity, poor bearing capacity, and low shear strength. This experiment aims to assess the suitability of six geosynthetic materials—namely, geotextile, geogrid, geocell, geomembrane, geomat, and geocomposite—in improving the engineering properties of black cotton soil. Laboratory tests were performed on both processed and unprocessed soils, including Specific Gravity, Atterberg Limits, Standard Proctor Compaction, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), Swelling Pressure, Swell Index, and Direct Shear tests on specimens with varying inclusion rates (0.5 - 3.0%) of geosynthetic products. Results showed substantial improvements across all measured properties. The Plasticity Index decreased from 53.40% to as low as 17% with the use of geogrid, while the maximum dry density (MDD) increased to 23.3 g/cc with geotextile. The CBR value doubled, reaching 11.8% with the use of geocomposite and geomembrane, and the UCS increased to 171 kPa. Swelling pressure and Swell Index decreased significantly, with the lowest values being 3.1 kPa and 3.72, respectively, when using the geocomposite. Additionally, the soil cohesion improved to 43.6 kPa with the use of geotextile, and the friction angle reached 23.5° with the use of geogrid. These findings confirm that geosynthetics, especially geocomposites, geomembranes, and geogrids, are highly effective in enhancing the mechanical behaviour of expansive soils. Incorporating them into subgrade stabilization strategies offers a sustainable and cost-effective solution for improving infrastructure performance in areas with problematic soils.