Abstract
Sand particles depositing through air generally align their largest dimensions in horizontal plane, forming a cross anisotropic fabric. Therefore, sands display varying strength, permeability, compressibility with directions. This study characterizes fabric anisotropy in loose and dense air-pluviated sand specimens scanned by X-ray Computed Tomography (X-ray CT) using a series of image processing techniques. The principal component analysis, three-dimensional watershed analysis, and Delaunay triangulation technique are used to compute directional parameters, including particle long axes, contact normals, and branch vectors, and scalar parameters, including index void ratios, coordination number, and average branch vector length. The particle long axes and branch vectors displayed preferred horizontal directions while the contact normals displayed preferred vertical directions. The dense specimen has smaller index void ratios, larger coordination number, and smaller average branch vector length than the loose specimen.
Highlights
In granular soils, particles depositing through air and water generally align their largest dimensions in horizontal plane, forming a cross anisotropic fabric
Soil fabric can be quantified by scalar parameters, such as index void ratios, coordination number, and average branch vector length
A river sand specimen was prepared at loose and dense conditions. Both loose and dense specimens were scanned by X-ray CT to generate volumetric images
Summary
Particles depositing through air and water generally align their largest dimensions in horizontal plane, forming a cross anisotropic fabric. Two-dimensional (2D) image processing techniques (Yang et al [12] and Zheng and Hryciw [13, 14]) have been developed to compute directional and scalar parameters and characterize fabric anisotropy from 2D images. These methods cannot characterize fabric anisotropy in three-dimensional (3D) soil specimen. To date, there was a lack of studies characterizing fabric anisotropy in air-pluviated sand specimen in loose and dense conditions. A river sand specimen (containing sub-angular to well-rounded particles) was prepared at loose and dense conditions. Both loose and dense specimens were scanned by X-ray CT to generate volumetric images.
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