Observation of Pile-Soil-Interaction during Cyclic Axial Loading Using Particle Image Velocimetry

Abstract

Two phenomena characterize cyclic axial loaded piles: accumulation of plastic pile displacements and degradation of pile capacity with increasing load cycles. The reason for this complex pile-soil-interaction is still not well understood. Hence, load and displacement controlled small-scale model pile tests were performed to investigate pile and soil behaviour from a qualitative point of view. Particle Image Velocimetry (PIV) was used to visualize the grains movement near the pile. A volume change was generally observed in all the tests depending on the mode of cyclic load. Shear localization appears in a small shear zone parallel to the pile shaft and remains approximately constant with increasing load cycles. Next to the shear zone a shear band can be observed which expands outwards with increasing load cycles. Moreover, a different pile and soil behaviour was observed under cyclic load compared to the static load test.