Experimental Study on the Influence of Polypropylene Fibres on the Strength and Swelling Behaviour of Lime Stabilized Clayey Soil

Abstract: Black cotton soil is a prevalent soil type in India, known for its significant swelling and shrinking behavior when exposed to changes in moisture content, making it particularly challenging for engineering purposes. This soil is highly clayey, predominantly composed of the Montmorillonite clay mineral. Given its unstable properties, this soil is not ideal for construction at the site. As a solution, the engineer may consider replacing or stabilizing the soil to ensure the stability and integrity of the structure. Soil stabilization is employed to enhance the geotechnical properties of black cotton soil, making it suitable for various engineering applications such as embankment protection, road construction, minor-loaded structures, parking lots, factories etc. In this study the Black cotton soil is treated with lime and reinforced with polypropylene to increase the strength and decrease the expensive behaviour. This thesis examines various soil properties like optimum moisture content (OMC), dry density, UCS , swelling pressure and shear parameters. Different quantities of lime (3%, 6%, and 9% by weight) are used to significantly decrease the expensive behaviour and plasticity of black cotton soils and polypropylene fibers (0.25%, 0.5%, and 0.75%) were mixed with black cotton soil to enhance its load-bearing capacity and reduce settlement, making it more suitable for construction. A series of experiments were conducted on these mixtures to evaluate their effectiveness in improving the soil's geotechnical properties. The tests conducted include liquid limit, plastic limit, optimum moisture content (OMC), maximum dry density (MDD), bulk density, dry density, and grain size analysis. The goal of this study is to improve the engineering properties of black cotton soil, ensuring that structures built on it can effectively withstand applied loads. The test results revealed that the Liquid limit, Plasticity index, differential free soil index and swelling pressure significantly on addition of lime and on further addition of polypropylene fibers resulted in increased strength of BC soil.