Physical Modeling of Stone Columns in Unsaturated Soil Deposits

Abstract

Abstract This article focuses on evaluating the load–settlement response of circular footings on unsaturated soil layers improved with stone columns using 1-gravity (1-g) physical modeling experiments. The initial (preloading) conditions in the soil layers were varied by compaction to the same dry density but different initial degrees of saturation. An effective stress analysis calibrated using direct shear experiments was found to satisfactorily predict the measured bearing capacities of unimproved soil layers, considering a change in failure mode for soil specimens at certain initial degrees of saturation. As the bearing capacity of the unsaturated soil layers increased, the amount of improvement gained by incorporating stone columns decreased. Bulging deformations of the stone column exhibited a close relationship with the bearing capacity, with smaller amounts of bulging in soil layers with low initial degrees of saturation that also have high bearing capacity. The stress concentration ratio increases with increasing initial degree of saturation, indicating that stone columns carry a greater fraction of the applied footing stress for soil layers closer to saturated conditions.