Enlarged Base Stone Columns to Improve Soft Clay Soil

This paper focuses on the behavior of enlarged base stone columns. The investigation was carried out through model tests performed on 400 mm in depth of soft saturated bed of clay, with undrained shear strength of 7.5 kN/m². Circular footings of 60, 70, 80 and 100 mm, in diameter, resting on the bed of soil were loaded incrementally up to failure. Two series of model tests were performed, the first consists of footing with soil underneath improved by ordinary stone columns, 52 mm in diameter and 102 and 204 mm in depth. The second consists of enlarged base stone columns with diameter twice the diameter of the stone column. The presence of the enlarged base caused a substantial increase in the load carrying capacity that reached about 3.5 times the load carrying capacity of the ordinary stone columns when the area replacement ratio is 0.72.