The influence of the in situ state of sands on the load-deflection behaviour of driven piles

A series of pile load tests was carried out in a centrifuge model, investigating the influence of the in situ volume–stress state on the load–deflection behaviour. Two sands of different mineralogies were tested at a variety of accelerations and sample densities. In each case a good correlation was found between the load–deflection behaviour and the in situ state quantified by the distance of the initial state from the critical state line in the v–ln p′ plane. How the soil arrived at its initial state, whether by compaction or overconsolidation, did not have a significant impact on the load–deflection behaviour. Repeated loading with a zero head load condition maintained between each cycle was not found to influence significantly the capacity or stiffness of response, but loading the pile to its full tensile capacity was found to reduce significantly the stiffness of response in compression.