Direct Shear Behavior of a Mixture of Sand and Tire Chips Using X-ray Computed Tomography and Discrete Element Method

Abstract

Granular materials such as soils, powders, and other particulate materials have been widely used in geotechnical engineering. In particular, sandy soils are one of the representative ones. Recently, there has been attention on environment friendly materials such as tire chips or other waste materials. Besides, one of the key behaviors for these materials is shear behavior, including the effect of dilatancy. In this paper, direct shear behavior of sands as rigid particles and tire chips as elastic particles is discussed. Here, micro-focus type X-ray computed tomography (CT) scanner is used with direct shear tests to investigate the close behavior in granular materials. To discuss the results of CT scanning quantitatively, a digital image correlation method is used and then, the distribution of the displacements in the shear box, shear strain, and volumetric strain are measured using CT data. In addition, a series of numerical analysis using discrete element method (DEM), which is often used for granular materials, is carried out for the same cases as direct shear test to validate the CT results. Finally, based on the comparative discussion between test results with CT scanning and DEM results, the direct shear behavior of different granular materials is precisely investigated for the first time using X-ray CT. The use of tire chips mixed with sand decreases the dilatant behavior under shear stress, and the peaks in shear stress are no longer observed. In addition, tire chips 3 seem to prevent shear bands to propagate in the material.

An enhanced tool for probing the microscopic behavior of granular materials based on X-ray micro-CT and FDEM

“…More recently, advanced tomographic techniques, such as X-ray computed tomography [2][3][4][5][6][7], 3D X-ray diffraction microscopy [8,9], have been successfully used to characterize the structural properties and particle scale dynamics throughout the full 3D systems. X-ray computed tomography aided laboratory test allows for the investigation of granular materials from micro-meso-macro perspectives [10][11][12][13][14][15][16][17], thus making it a promising tool in studying the complex granular systems. Tracking the trajectory of large number of moving particles remains a challenge, especially for the granular system undergoing large deformation and the large scanning interval.…”

PLATYMATCH – A particle-matching algorithm for the analysis of platy particle kinematics using X-ray Computed Tomography

“…An increasing body of research shows that the particle scale properties of soil importantly influence the mechanical behaviour of granular materials. Sand-grained soils unlike clays have been widely studied at the particle scale and this has revealed important micromechanical behaviours including the change of sand grain morphology due to fracture mechanisms (Zhao et al 2015), the decrease of dilatant behaviour with the suppression of peak shear strength in sand mixed with tyre chips (Chevalier et al 2019), and the observation of pre-peak initiation of strain localisation in sand using X-ray computer tomography (X-ray CT) (Andò et al 2012).…”