A database is presented of case histories showing long-term set-up of driven piles in non-cohesive soil, revealing that long-term set-up can be substantial ― an average of 40% per log cycle of time being observed. The main results from a comprehensive study of the mechanisms behind pile set-up are presented. In the main, the study is based on pile loading tests, undertaken at different points in time, on piles instrumented with earth pressure cells on the shaft. In addition, dynamic testing and torque testing on small-scale rods were also performed at different points in time. It was concluded that pile set-up is caused by two strongly interconnected mechanisms: creep (stress relaxation) and soil aging (increasing dilation and stiffness). A conceptual model explaining the underlying process is presented.
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