Comparative study on the behavior of encased stone column and conventional stone column

Stone columns, one of the most commonly used soil improvement techniques, have been utilized worldwide to increase bearing capacity and reduce total and differential settlements of structures constructed on soft clay. Stone columns also act as vertical drains, thus speeding up the process of consolidation. However, the settlement of stabilised bed is not reduced in many situations for want of adequate lateral restraint. Encasing the stone column with a geogrid enhances the bearing capacity and reduces the settlement drastically without compromising its effect as a drain, unlike a pile. The behavior of the encased stone column stabilized bed is experimentally investigated and analysed numerically. In the numerical analysis, material behaviour is simulated using Soft Soil, Mohr Coulomb and Geogrid models for clay, stone material and encasement respectively and is validated with experimental results. The parametric study carried out on varying the L/D ratio (L = length of the column; D = diameter of the column) of column, stiffness of geogrid and angle of internal friction of stone material gives a better understanding of the physical performance of the encased stone column stabilized clay bed.