AN EVALUATION OF EXPANSIVE SOIL STABILIZATION WITH SAND AND COAL BOTTOM ASH: A COMPARATIVE STUDY

Expansive soils pose significant challenges in geotechnical engineering due to their tendency to swell and shrink with moisture variation, often leading to structural damage. Traditional stabilization techniques have limitations in addressing the volume change behavior and the insufficient strength of such soils. This study investigates the effectiveness of granular columns composed of sand and coal bottom ash (CBA) in improving the shear strength characteristics of expansive soil. While granular column techniques have been studied previously, limited attention has been paid to the comparative performance of CBA and sand columns with varying geometries, particularly in small-scale laboratory conditions. The research involved 19 batches of soil samples, including a control sample and six batches each of sand and CBA columns with diameters of 16 mm, 19 mm, and 25 mm, and penetration depths of 60 mm, 80 mm, and 100 mm. The unconfined compression strength (UCS) test was employed to evaluate the mechanical performance of the treated soils. Results revealed that sand columns enhanced the shear strength of expansive soil by 25% to 76%, while CBA columns demonstrated an improvement of 30% to 88%, depending on the diameter and penetration depth, which corresponded to replacement and penetration ratios of 0.6, 0.8, and 1.0. This study contributes to the understanding of the mechanical behavior of expansive soils treated with alternative sustainable materials like CBA, offering a cost-effective and environmentally friendly solution for ground improvement.