Visualization of an internal sand displacement field around a laterally loaded vertical pile

Abstract

In this research, an internal sand displacement field around a laterally loaded vertical pile is visualized using transparent soil and an image processing technique called digital image cross-correlation (DIC). DIC is a region-based image processing technique which can calculate the displacement field between two images. Transparent soil is made of silica gel with a pore fluid having the same refractive index. Transparent soil has been studied to have the strength and deformation properties similar to natural soil. An optical test set-up is developed to capture the images during loading. This optical test set-up consists of a camera, a laser light, a line generator lens, a loading frame, a Plexiglas mould, and a PC. The saturated fine sand in loose condition is modeled in this research. A laser light sheet is generated to slice the transparent soil model by passing a laser beam through the line generator lens. A distinctive laser speckle pattern is generated through the interaction between the laser light and transparent soil. A series of images are taken from the camera while a scaled pile is being loaded laterally. The displacement fields are calculated by cross-correlating two consecutive images and the corresponding strain fields are deduced from the displacement fields. The development of both displacement and strain fields is investigated by studying deformation and strains at different loading stages. The test results are similar to the published data. This research improves the understanding of soil movement around a laterally loaded pile. It also advances the physical modeling technique using transparent soil.