Comparative Evaluation of Shear Strength Enhancement in Soft Clay Reinforced with Sand and Stone Dust Column

Soft clay soils are problematic soil that causes bearing capacity failure and excessive settlement, leading to severe damage to buildings and foundation. The stone column technique, commonly utilised to reinforce soft clay soils, enhances bearing capacity and reduces settlement by compacting gravel or stone aggregates, hence improving the stability and load-bearing capacity of foundation beds. This study aimed to examine and compare the efficacy of sand and stone dust columns in improving shear strength via laboratory-scale modelling. Initially, several geotechnical experiments were conducted to ascertain the qualities of the materials, and the findings were thoroughly analysed. The Unconfined Compression Test (UCT) and Triaxial Test were performed on 19 soil samples, comprising a control sample and three batches, each of 16 mm, 19 mm, and 25 mm diameter sand and stone dust columns, to comprehensively evaluate shear strength parameters, including apparent cohesion (c′) and effective friction angle (φ′). Sand and stone dust columns were tested with different area replacement ratios, such as 10.24% for a 16 mm diameter, 14.44% for a 19 mm diameter, and 25% for a 25 mm diameter. The column heights varied for each diameter, measuring 60 mm, 80 mm, and 100 mm, which corresponded to penetration ratios of 0.6, 0.8, and 1.0, respectively. The most significant enhancement was observed for both stone dust and sand columns at a diameter of 19 mm with a penetration of 100 mm, showing improvements of 90.21% and 85.31%, respectively. The improvements in shear strength were significantly influenced by both column diameter and height, with optimal height-to-diameter (H _c /D _c ) ratios for enhancing load-bearing capacity ranging from 4 to 8.