X-ray CT imaging of 3-D bearing capacity mechanism for vertically loaded shallow foundations

Abstract

 The three-dimensional bearing capacity of shallow foundations has not been fully investigated because of the difficulty in visualizing and understanding the complex three-dimensional failure mechanism. In this paper, a series of model loading tests were conducted on shallow foundations with square and rectangular shaped footings X-ray CT scanning techniques were utilized to nondestructively visualize and investigate the soil behavior during the loading tests. Based on the tomographic results for four different footing geometries, both surface deformations and below ground deformations along the failure surface cross section are described and three-dimensional failure mechanisms illustrated. A gradual change or progression of the bearing capacity failure pattern was observed and quantified as the footing aspect ratio changed from a square foundation to a rectangular shape that approached plane strain conditions. It is anticipated that the process and technique developed in this study could be beneficial in understanding and quantifying the mechanics associated with other soil-structure interaction problems, especially complex problems in which the failure mechanism is difficult or impossible to predict using conventional geotechnical engineering principles.