The Behavior of Sand Columns in Soft Expansive Clay: Experimental Study

This paper discusses the results of study conducted on sand column constructed in soft expansive clay. The length to diameter ratio (L/d ratio) of the sand column was varied, from 2 to 10 with an interval of two. Floating sand column encased with geogrid were also formed in the soil. The load tests were carried on a circular footing placed over the sand column to study the load settlement behavior in the two cases of floating sand column; the one with ordinary sand columns and the other with geogrid wrapped sand column. The soil beds were prepared in a model tank of diameter 173 mm and height 605 mm. The sand column of diameter 55 mm was constructed at the center of the soil bed. A load test on the footing placed directly on the soft soil bed was also conducted to compare the results of load tests of sand column and geogrid encased sand column. The improvement in load carrying capacity of sand column was expressed as a non dimensional parameter, improvement ratio (IR), which is the ratio of ultimate load carried by the footing on sand column (Qult. column) to that obtained for unreinforced soil i.e. Q. It is found that IR increases with L/d ratios up to 8 then the increment is marginal.