ABSTRACT
This paper describes how recently developed experimental procedures have been used to quantitatively study the initial and evolving microstructure of sand specimens. Procedures for capturing images using a microscope mounted CCD camera and brightfield illumination from the surfaces of coupons cut from specimens whose structures were fixed at desired stages of loading by resin impregnation are described. Analysis of the images using automated algorithms to quantify measures such as local void ratio distribution and particle orientations shows how global response masks the complex conditions existing within the specimens. Differences in microstructure resulting from specimen preparation are illustrated. The evolution of structure at various stages of shearing in replicate dilatant specimens shows how global void ratio measures lead to erroneous determinations of steady state and provides direct microstructure based evidence of the need for routine use of lubricated end platens and local deformation measurements.
