Discrimination of Particle Breakage below Pile Tip after Model Pile Penetration in Sand Using Image Analysis

Abstract

Particle breakage is a common phenomenon in granular soils and has been well observed during laboratory and in-situ pile studies. In this paper, an image analysis approach was developed to investigate the particle breakage behavior below a flat-ended pile tip, with special attention given to the location of particle breakage. The color difference between the original silica sand (light gray) and its coated surface (black) allows particle breakage to be distinguished based on the gray level variation. Larger gray values corresponded to a higher degree of breakage that occurred within the target area, which provides a new approach for quantitative assessment of the particle breakage extent. First, sequential images of the subsoil at different depths below a loaded pile tip were digitally recorded, and the degree of particle breakage was subsequently evaluated based on the gray level of the images. Then, the layered images at different depths were assembled to form a quasistereoscopic graph, and the slice image at any profile could be obtained. Accordingly, the zone of particle breakage below a flat-ended pile tip was graphically illustrated. The results of this study are beneficial for further clarifying the mechanism of particle breakage and provide a fundamental basis for accurate assessment of the ground-bearing capacity considering soil crushability.