The construction of a 10-metre-height embankment on a marsh area is presented. The foundation ground was improved with stone columns to reduce the final settlement and increase the settlement rate. Stone columns were constructed by the dry bottom-feed method with a diameter of 0.8 m and a spacing of 2.8 m in a triangular pattern. The soft soil treated is a more or less homogeneous clay layer of 9 m. Field instrumentation was used to study stone column behaviour. Total pressure cells on soil and column, piezometers and a 3-level extensometer were installed. Settlement and stress concentration factors are assessed, whereas the consolidation process was too fast to be analysed. The measurements are compared with the results of a three dimensional finite element model.