Application of particle image velocimetry (PIV) in the study of uplift mechanisms of pipe buried in medium dense sand

Abstract

Geotechnical centrifuge modeling, which can effectively simulate the stress field of soil in the prototype, was adopted to help investigate the effects of the uplifting of pipes buried at different depths within a medium dense sand under (1) a static state and (2) a dynamic state. To acquire the displacement vector fields and strain contours in the soil around pipes, particle image velocimetry technology was applied. The study focused on the deformation mechanisms of soil surrounding the pipes and ground surface. Two different deformation triggers, external forces and soil liquefaction, were considered. When uplifting was caused by an external force, the relationship between the soil deformation and uplift resistance was similar to the typical ground load–deformation characteristic relationships. There was little displacement of soil during the elastic stage. Along with the uplifting of the pipe, a plastic zone within the range of one pipe diameter (1D) above the pipe appeared in the soil at peak resistance. During the post-peak period, a shear failure plane extended upwards to the ground surface, at an inclined angle forming a trumpet-like shape. The ground surface deformation range expanded according to the buried depth of the pipe. Meanwhile, in a liquefied field, the soil flowed within a heart-shaped region around the pipe. The soil deformation region surrounding a shallow buried pipe, with a width of 5D–6D, was far larger than that found for a pipe buried at the same depth in a static field. Both heave and settlement could be observed on the ground surface.