An X-ray computed tomography technique for the measurement of packing density in granular particles

It has been shown that the flow and shear characteristics of granular particles such as soils are significantly dependent on the shape of the particles. This is important from a practical viewpoint because a fundamental understanding of granular behavior will lead to an improved understanding of soil stability and influence the design of structural foundations. Furthermore, the calculation of soil stability and consequently structural stability is particularly useful during earthquake events. In previous work, we have demonstrated the applicability of X-ray and optical tomography measurements for characterizing 3-D shapes of natural sands and manufactured granular particles. In this paper, we extend the work to measure the arrangement and orientation of an assemblage of such particles. A combination of X-ray CT for measuring the coordinates of the individual particles, and basic image processing techniques for computing the local variations in packing density are employed to generate density maps. Such maps can be used to gain a more fundamental understanding of the shear characteristics of granular particles. In this paper, we demonstrate the success of our technique by exercising the method on two sets of granular particles - glass beads (used as a control) and Michigan Dune sand.