The behaviour of a raft foundation above a pile-supported earth platform is studied in a centrifuge. Instrumented piles are inserted in a soft soil model made of a mixture of sand and clay. A granular mattress made of Hostun sand is set between the raft and the group of inclusions in order to transfer by arching effects a part of loadings directly to the piles. Different types of loading are applied on the raft foundation: vertical loading, combined loading and swipe test. The preparation of soil samples and the instrumentation of the model are detailed. The complex loading device is also presented. Finally, tests results are presented and show the improvement made by the pile reinforcement of the soft soil.