Stone columns are commonly used for ground improvement in soft soils. In very soft soils, insufficient soil strength for the soil surrounding the upper portion of the column often causes lateral bulging failure in this zone when the column is loaded, even at relatively small applied vertical stresses. To prevent this type of failure, stone columns can be encased using a high strength geosynthetic; this encasement increases the overall strength and stiffness of the stone column and prevents lateral bulging of the column into the surrounding soft soil. Encased stone columns can be used for foundation support applications or for large-area ground improvement, and show potential utility for the support of road embankments, oil storage tanks, and other types of structures that are not overly sensitive to settlement. In certain field cases, the soft soil layer can be thick, making the construction of the encased stone column down to a hard bearing layer impractical. This study describes the results from three-dimensional finite element analyses that were carried out to analyze the behavior of a single fully encased stone column resting on a non-rigid layer that is subjected to load on the top of the stone column. The numerical modeling that was performed studies the influence of varying the: dilation angle of the stone column material, diameter of the encased stone column, tensile strength of the encasement, and depth of the soft soil beneath the tip of the encased stone column (i.e. floating depth). These parameters play an important role in the behavior of the stone column in both the elastic and plastic phases of deformation. The numerical analyses show that the column diameter has a significant effect on the bearing capacity and load-displacement response of the encased stone columns. Also, the bearing capacity of the encased stone column tends to have a high correlation with decreasing ''floating depth".
展开▼
