Effects of orthogonal lateral loading on ultimate lateral pile load capacity and lateral flow behavior of a model pile

Previous studies have primarily focused on the effects of unidirectional lateral loading on piles, forming the basis for established design guidelines. However, in practical applications, lateral loads on pile foundations often act in multiple directions. This study examines the behavior of a model single pile subjected to orthogonal lateral loads, specifically analyzing how different loading levels in the x-direction impact the pile’s response to subsequent loading in the y-direction. A specially designed bi-directional lateral loading apparatus was used to independently apply loads in the x and y directions, allowing for diverse lateral loading paths. Findings indicate that increasing preloading in the x-direction reduces the ultimate lateral load capacity of the pile under y-direction loading. Additionally, increasing the load in the y-direction while holding the x-direction load constant alters the pile’s lateral flow behavior, with these variations diminishing as the y-direction load rises. The py-y curve shows a decreasing slope with higher x-direction loads, suggesting a reduction in y-direction soil modulus (Es). Both the py-y and px-x curves are affected by loads in the orthogonal direction, highlighting the importance of accounting for preload history and levels when predicting pile performance under multidirectional lateral forces.