Centrifuge Modeling of Soft Soil Reinforced with Granular Columns

This paper presents a geotechnical centrifuge model of an embankment built in stages, over a 6.0 m layer of soft soil reinforced with nine floating granular columns arranged in a 3 × 3 square grid. The container was divided in two compartments where reinforced and unreinforced soil were tested simultaneously for comparison purposes. The load was applied by means of a 4 m high sand embankment (prototype dimensions) built in three steps. For each step, the centrifuge was stopped to allow the placement of the embankment layer and then re-accelerated up to 26 g and the excess of pore pressure was allowed to dissipate after each step. The instrumentation, comprised of total stress cells, pore pressure transducers and displacement transducers, was configured to collect information about the load transfer mechanism between the soil and the instrumented central column for each loading step during pore pressure dissipation. Results showed that despite representing only 30% of the total load, the first step provoked almost 70% of total vertical displacement. Finally, the columns were exhumed for a detailed and comprehensive visual analysis aiming to support and explain the results obtained.