Analysis of the Shear Strength of Expansive Soil Stabilized with Sand and Coal Bottom Ash Columns

Soil stabilization refers to a range of techniques and methods used to upgrade the engineering properties of soil, transforming it from an unconsolidated state into a more reliable medium. Expansive soils can cause serious problems, such as cracks and building damage, because they swell and shrink with moisture changes. One common solution is using granular columns. This research aims to determine the effect of sand and coal bottom ash (CBA) columns on expansive soil. The Unconfined Compression Strength (UCS) was used to measure the improvements. There was a total of 19 batches of soil samples, which consisted of one control sample and six batches each of 16 mm, 19 mm, and 25 mm diameter sand and CBA columns. Columns of each diameter were tested at heights of 60 mm, 80 mm, and 100 mm. All soil samples measured 50 mm in diameter and 100 mm in height. The results showed that sand columns increased shear strength by 25% to 76%, while CBA columns gave even better results, with a 30% to 88% improvement, depending on the size and depth of the column. Overall, the study shows that both sand and CBA columns can make expansive soils stronger, with CBA being more effective. The size and placement of the columns play an important role in improving soil strength.