NUMERICAL MODEL FOR GROUP OF STONE COLUMNS

Stone columns are one of the most effective ground improvement techniques, which is widely used to enhance the performance of shallow foundations built on soft ground. Stone columns are also installed in embankment dams’ foundation to reduce the settlement, increase the bearing capacity and minimize the liquefaction potential. The current design procedure for these columns is based on the method developed for a single isolated column, ignoring the columns interaction and accordingly the group efficiency, and the ultimate load of the group is taken to be the design load of the single column multiplied by the number of columns. Model test has shown that the failure mechanism of a group of columns could be quite different from a single type. The deforming shape of a single stone column is mostly due to bulging however due to group effect the shear failure type is very probable when group of columns is concerned. This paper analyzes the group effect and failure shape of group of stone columns using finite elements method. Furthermore, the effect of modulus ratios of stone column to clay, columns diameter, spacing between them and internal angle of friction of columns is investigated. The results show that the presence of adjacent columns provides confinement and failure behavior of stone columns is very dependent to the group effect.