Combined pile-raft foundation subjected to lateral loads

Concerning the load bearing behaviour of vertically loaded Combined Pile-Raft Foundations many studies and publications are available whereas for Combined Pile-Raft Foundations subjected to lateral loads scientific results or case histories are very rare. But also for horizontal loading it is possible to obtain a very economic foundation design and to reduce displacements by using a Combined Pile-Raft Foundation (CPRF). In order to investigate the bearing behaviour of a CPRF subjected to horizontal loads a number of small scale model tests with CPRF, raft foundation and pile group at 1g-level were performed. The results show that e.g. the horizontal resistance of the CPRF is much higher than the resistance of a comparable pile group and a considerable part of the horizontal load applied is carried by the raft. Thus neglecting the horizontal resistance of the raft, as usually done for design purposes, leads to an underestimation of the total resistance of the foundation and to an overestimation of the horizontal displacements and of the shear forces as well as bending moments in the piles.