Bearing Capacity and Settlement Response of Ordinary and Geosynthetic Encased Granular Columns in Soft Clay Soils: Analysis and Design Charts

This paper discusses the bearing capacity and settlement response of granular columns with and without geosynthetic encasement using the currently available design procedure. The design procedure is modified to include the influence of the geosynthetic encasement. The key parameters influencing the load bearing capacity and settlement are studied through comprehensive parametric analyses. The results portray the advantage of geosynthetic encased granular columns in enhancing the bearing capacity and reducing the settlements compared to granular columns without encasement. Different installation patterns of granular columns were considered in this investigation. The maximum bearing capacity improvement and settlement reduction are observed with granular columns installed in triangular plan arrangement. The hexagonal pattern results in the lowest area replacement ratio and also the lowest improvement factors. It is shown that with geosynthetic encasement, the performance with hexagonal pattern could be improved to match with other more efficient patterns like square and triangular. Some selected results are validated through detailed finite element results. A quick assessment of the settlement improvement with geosynthetic encapsulated granular columns is possible with the design charts presented.