Evaluation of load distribution in Piled-Raft Foundation Systems (PRFS) founded on soft clay, via geotechnical centrifuge tests

Piled raft foundation systems (PRFS) have been increasingly adopted as an alternative foundation system in developed urban areas underlain by soft soils. In such soils, a double consolidation process may occur as a result of both external loading and subsidence, leading to changes in the soil stress state. Previous studies on PRFS have primarily focused on settlement behaviour induced by external loading, whereas the effects of subsidence processes have received comparatively limited attention. Moreover, most investigations of PRFS behaviour have been conducted using numerical approaches. This study presents an experimental investigation of the behaviour of PRFS using geotechnical centrifuge modelling, with particular emphasis on the redistribution of load between the raft and piles and the associated changes in pore water pressure. Physical models at a scale 1:70 were developed and instrumented to enable direct measurements of the foundation response. The results demonstrate that the proportion of load carried by the raft and piles varies with the pile arrangement and changes in pore water pressure within the soil. The pile contribution increased from 23–26% during Stage 2 to 46–54% during Stage 3, indicating a substantial redistribution of load from the raft to the piles following groundwater extraction. Under subsidence conditions, the redistribution of load between the raft and piles was found to be consistent with trends previously reported in the literature.