Rational design of piled raft

Abstract

Piles have been traditionally designed to ensure the transfer of the whole structural load to the soil in which they are embedded. It is now largely accepted that this way of doing is unduly conservative, especially in those cases in which an unpiled raft is sufficient to guarantee a satisfactory safety level. Nevertheless, it is still very common in the daily practice, sometimes for the restrictions imposed by local codes and regulations. Much research efforts have been dedicated to a more rational design of piled foundations, essentially based on a proper collaboration among raft and piles not only for increasing the overall stiffness of an unpiled raft but, if required, also for increasing its capacity, for controlling differential settlements, for reducing the state of stress into the raft. With no claim to cover any single aspects, some design options will be presented, providing some insight into a rational approach to piled raft design.