SEISMIC RESPONSE OF PILE-RAFT FOUNDATION CONSTRUCTED IN SOFT CLAY

Two groups of centrifuge tests coverage to relatively flexible and stiff piles were conducted to examine the response of clay-pile-raft system under different loading levels of superstructure during earthquake shakings. It is observed that interaction between pile-raft and clay will cause a strain soften and stiffness degradation in the surrounding clay which produce a higher resonance period in clay of near field than that of free field clay. The difference of period among raft and clay of both near and free field indicates that ground motion of either near field and free field may not be representative of pile-raft motion. Furthermore, there is a quite difference between flexible and stiff pile response. For flexible pile, the effect of surrounding clay acted as an additional inertial loading on the pile-raft may not be as significant as on the stiff pile during earthquake shakings.