Model-Scale Study on the Effect of Cyclic Loading on Pile Lateral Bearing Capacity at Different Directions

Foundation piles are extensively used to support the lateral loads exerted on structures. In earthquake-active areas, piles in service usually experience cyclic lateral loadings induced by earthquakes. Many previous studies mainly focused on the pile lateral bearing capacity along the same horizontal direction that the cyclic loadings are applied. This paper reports two series of pile model tests conducted in soft and medium-stiff clay utilizing a computer-controlled biaxial motion platform. In these tests, the piles were loaded monotonically along different horizontal directions, after being cyclically loaded along a specified horizontal direction and allowed to return to the original position. The results indicate that the post-cyclic lateral resistance of pile depends on the intersection angle between the directions of cyclic loading and monotonic loading. The degree of reduction in the bearing capacity is a function of the shear strength of soil as well as the intersection angle.