Stone Columns and Reinforced Sand Bed for Performance Improvement of Foundations on Soft Clay

being one of the most erratic soils with very low bearing capacity and high compressibility. Many techniques, such as stone columns and geosynthetic reinforced sand bed, are effective means of performance improvement of foundations on soft clay soil. Although their individual applications have been studied extensively, the combined application of both has remained unexplored. Stone columns develop their load carrying capacity from the circumferential confinement provided by the surrounding soils. In very soft soils, an important problem which should be taken into account for designing stone column is bulging as the circumferential confinement offered by the surrounding soft soil may not be sufficient to develop the required load carrying capacity. Hence a confinement by geosynthetics would yield a better result and prevents squeezing of stones into the surrounding clay. The load carrying capacity is further increased and settlement is decreased with the addition of a sand bed over the stone columns, also this layer of sand is used to let the foundation distribute its load uniformly. In the current research, a series of numerical model tests on an unreinforced sand bed (USB) and a geogrid reinforced sand bed (GRSB) placed over a vertically encased stone column (ESC) floating in soft clay. Three dimensional finite difference numerical models were performed using a finite difference package FLAC3D. In the finite difference analysis, geosynthetics were modeled as an elasto-plastic material