Offshore jacket foundations may fail under lateral loads of wind, wave, current, earthquake, etc.This paper describes centrifuge model tests carried out to investigate the pile-soil interaction of a tetrapod jacketfoundation subjected to laterally monotonic and cyclic loads in the diagonal direction. The monotonic loadingtest results show that the maximum bending moment of the up-lifted pile is smaller than that of the down-pushedpile. Moreover, within the depth of 2.5 times the pile diameter, the static soil reaction on the up-lifted pile perunit length is only approximately 40% of that of the down-pushed pile at the same depth, since the axial force onthe up-lifted pile decreases the effective stress on the soil around the pile. In the cyclic loading test, the maximumbending moments of both up-lifted and down-pushed piles decrease and the latter one decreases more. The soilreactions on piles per unit lengthwere derived from the measured bending moments of the pile shaft. Degradationof these soil reactions occur during laterally cyclic loading, and the cyclic degradation factor of the up-lifted pileis almost half of that of the down-pushed pile of the jacket foundation.
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