Behaviour of circular footings resting on a reinforced granular bed underlain by a single floating stone column

A hybrid system of stone columns with a granular bed is often used to improve the behaviour of soft clays. However, the potential benefits of reinforcing this bed with geogrids have not been sufficiently emphasized in the literature. In the present study, a three-dimensional finite element model of a field-scale circular footing supported by a reinforced bed over a single floating stone column was developed. The accuracy of the developed model was verified by comparing the predicted load settlement responses with measured ones from the literature. The main objectives are to assess the bearing capacity characteristics of the footing and the bulging behaviour of the columns. The impact of various governing factors was evaluated, including the length and diameter of the stone column, the thickness of the reinforced bed, and the number, width and stiffness of geogrids. The results showed that the bulging diameter of the stone column increases continuously with increasing its length (L) up to 10 times the diameter (d). Beyond L = 10 d, there was no further increase in the bulge. The results also showed that reinforcing the granular bed with a geogrid layer could reduce the bulging of the stone column by 21%. The bearing capacity improved by increasing the width of the geogrid up to 3B, beyond which there was no further significant improvement.