ABSTRACT
Structural foundations are roughly divided into direct foundations (usually named as shallow foundation) and piled foundations (deep foundation), with piled raft foundations classified as the middle type between them (Japanese Society of Architecture 2001). In other words, piled rafts are typical foundations that combine a direct foundation (or named as raft) with piles. As shown in Figure 1, in this type of foundation, the superstructure is supported with both the subgrade reaction of the raft and the skin friction and endbearing capacity of the piles. This method has already been put into practical use as a structure foundation in building construction to compensate the poor bearing capacity of raft itself with piles (Japan Road Association 1999). It will also be necessary in the near future to establish design and construction methods for piled raft foundations in the field of civil engineering structures for improving the cost performance and effective allocation of construction funding. For example, its application for retaining walls, culverts and other simple structures that allow relatively large deformation is considered to be highly feasible (Japan Road Association 1999).
