Numerical Analysis Of The Performance Of Geogrid-Reinforced Stone Columns In Soft Soil

One of the methods suitable for the improvement of the soft and loose ground is to use the stone columns technique. In modifying soil using stone columns, soft and loose soils with low shear strength and high compressibility are replaced by granular materials with high shear strength and very low compressibility, and a significant contribution of loadings applied on the foundation will be transferred to the underlying layers. Typically, stone columns are used in soils with undrained shear strength between 15 and 25 kPa. In soils with lower shear strength, the lateral constraints induced by the surrounding soil are inadequate to prevent lateral buckling of the column under applied loadings, so, it is necessary to take special measures in order to use stone columns in this type of soils. In such soil, one of the suitable techniques is to use geogrid reinforcement layers, in the form of a plate, at different depths of the stone column. Therefore, the present study aims to numerically analyze the soft ground modified using geogrid-reinforced stone column, using a finite element software, called PLAXIS software. According to the arrangement of the stone column, the axial strain modeling is used to model the improved soft ground in the form of a single cell. Also, geogrid plates are used in the column at different intervals and with different stiffness. In order to study the settlement of improved ground, a settlement reduction ratio is defined. The results indicated that the settlement reduction ratio depends on the various parameters such as reinforcement depth, inter-layer interval and stiffness of reinforcement elements and it ranges from 2.3% to 18.3%. In addition, a decrease in lateral expansion of the stone column is observed in the case of using geogrid layers.