ANALYSIS OF EMBANKMENT SUPPORTED BY STONE COLUMNS ENCASED WITH GEOSYNTHETIC MATERIAL

Stone column is often employed for strengthening of an embankment seated on deep soft clay. But in very soft clay, stone column may not derive adequate load carrying capacity and undergo large lateral deformation because of inadequate lateral confinement. In such cases, reinforcement to individual stone column by geosynthetics enhances load caring capacity and reducing lateral deformation. In this study analysis of an embankment resting on encased stone columns ESC are investigated using the latest version of finite element program ''Plaxis 3D 2013''. Example of model prediction and accuracy of finite element formulation were given. Then the transient analysis of three-dimensional embankment problem supported on geogrid reinforced stone columns has been carried out taken in to consideration the influence of some parameters on the long-term behavior of the system, such as stone columns diameter (d), stone columns length ratio (L/d), encasement stiffness, undrianed shear strength. The results also indicated that the percentage of decrease in settlement for embankment reinforced with ESC relative to untreated embankment for (L/d=5) were (49.83 %, 43.53 %, 38.7 % and 32.63 %) for S/d (2.5, 3.0, 3.5, and 4.0); respectively. And for (L/d=8) being (68.86 %, 67.23 %, 55.48 % and 51.36 %) for S/d (2.5, 3.0, 3.5, and 4.0); respectively. And the pattern of ESC has significant influence on the settlement comparing with the effect of spacing between them. Also for (L/d = 8) the maximum horizontal deformation was observed at a depth of about 1.7d. The results showed significant decreasing in lateral displacement with increasing the diameter of encased stone columns. Also increasing the undrianed shear strength, cu by 100 % decreased the vertical settlement by about 65 % and a noticeable decrease in the lateral displacement was obtained with increasing cu.