Effect of recent load history on laterally loaded piles in normally consolidated clay

The response of piles subjected to lateral loading (along a single line of action) has been substantially investigated in the past. However, little attention has been devoted to studying how a change in the lateral load direction (say, from east–west to north–south) may affect the overall response. This paper describes a Winkler type of soil–pile interaction model that allows coupling between the two perpendicular directions in a systematic way, by adopting local yield surfaces along the pile. A parametric study is presented for a range of pile lengths and cross sections, applied loads, and changes in direction from previous loadings. An analogy is shown to exist between the response of the pile to changes in the direction of lateral loads and the well-known elementary constitutive phenomenon of the recent stress history. As is commonly assumed in practice the model shows that the direction of the resultant pile response does not have a large impact on the load carrying capacity of the system. However, changes in the lateral load directions alter the global stiffness response, and this could potentially play a significant role in the serviceability design. © 2007 ASCE