Undrained Load Response of Soft Clays Reinforced with Geosynthetic-Encased Sand Columns

Sand columns represent one of the options for strengthening weak, soft clays. In some field applications geosynthetic filter materials are used to separate the sand columns from the surrounding clay. The effect of encapsulating granular columns with geofabrics of different strengths and stiffnesses has been investigated by several researchers through laboratory and numerical modeling. This paper presents results from a laboratory program designed to explore the effects of encasing sand columns with geofabrics on the load response of the composite material. A series of consolidated-undrained triaxial tests were performed on samples of kaolin clay reinforced with non-encased sand columns and fabric-encased sand columns. The results are discussed and the effects of the various parameters which govern the load response of the sand column/clay composite are explored. Implications regarding the design methodology and expected behavior of sand column/clay composites are discussed in relation to actual field behavior.