Towards the development of a new guideline for the design of geosynthetic-reinforced column-supported embankments

Deep cement mixed (DCM) columns with geosynthetic reinforcements are used as integrated foundation systems for construction of embankments over soft soils. Several design guidelines are available in the literature for these embankments based on the soil arching and membrane theories. This paper identifies some inconsistencies in applying these design guidelines, especially the shape of the arches formed and their evolution. A two-dimensional numerical model calibrated using a well-established case study confirmed that soil arches formed within the embankment fill are semi-circular or catenary in shape and the size changes during the construction process. Using the same numerical model and the field measurements from the case study, three different design procedures currently available for the design of geosynthetic reinforced-column supported (GRCS) embankments are investigated. All three design methods yielded uneconomical and over conservative predictions for the geosynthetic reinforcements while giving unsafe predictions for DCM columns. Thereby gaps in current design practice are identified and some future research directions are proposed for the development of better design guidelines for these embankments.