Load transfer mechanisms of piled raft foundations

Within an extensive research programme on piles as settlement reducers, multi-g centrifuge tests have been performed on models of piled rafts with the piles arranged in two configurations: in direct contact with the raft and separated from the raft by a granular fill layer, introduced to create a uniform pressure distribution on the raft bottom and to reduce constraint reactions between the piles and the slab. The aim of this paper is to present some of the observations concerning the load transfer mechanisms which take place within a mixed foundation and to evidence the influence of a granular cushion, inserted between the raft and the pile heads, on the foundation load-settlement behaviour.