Abstract: As pile foundation is usually deeply buried underground,the horizontal deformation of pile-soil is not easy to be observed in field tests. Model test of a single pile subjected to lateral load on pile head was carried out in sandy soil by using Particle Image Velocimetry (PIV) to study the deformation mechanism of soil-pile under lateral loads. Factors such as bending stiffness of pile, relative density of soil, and size of scour pit were taken into consideration in the model test. The soil displacement and strain around the pile were obtained, and the horizontal pile-soil interaction modes of a flexible pile and a rigid pile were discussed. The influence of local scour on lateral pile-soil interaction were also examined. Results demonstrate that: 1) the displacement and shear strain of soil around the pile gradually develop along the horizontal direction and depth direction; therefore, the assumption that the soil strain in the strain wedge developes evenly in the strain wedge model for analyzing laterally loaded pile needs to be modified. 2) Pile-soil interactions were observed mainly in the passive compressed area of soil in front of pile and the active pressurizing area of soil behind pile above the first zero-point of lateral displacement of pile body, while those below the first zero-point for a laterally loaded rigid short pile shall not be ignored. 3) Scoured soil layer above the bottom of the scour pit still plays a due role in reducing the lateral deformation of the pile-soil system.

Key words: laterally loaded pile, scour, PIV technique, pile-soil interaction, lateral deformation, sandy soil