Abstract
Grain breakage is of paramount importance for understanding the behaviour of granular materials used in various engineering applications, such as pavements, roads, rail tracks, the oil and gas industry, and mineral processing. Changes to grain properties of a uniformly graded sand specimen stemming from breakage during compression were studied with the aid of three-dimensional Synchrotron Radiation-based Micro-Computed Tomography. The fast scanning and high-resolution 4D imaging were utilised to capture images from the interior body of the granular assembly during loading. The fractal distribution of the sand assembly showed that breakage becomes dominant in smaller grains rather than larger ones, where an increase in the amount of newly generated fine fragments leads to high coordination number surrounding the larger grains. More importantly, the results of morphological changes in the particulate assembly revealed that there is a reversal trend in the grain morphology evolution with increasing stress. The sand grains tended to create more spherical fragments with higher aspect ratio whereas by increasing the stress this trend completely shifted.
Highlights
Grain breakage is common in granular materials, such as powders, soils, and manufactured aggregates, when subjected to high loading or large deformations
While breakage is desirable in some industries such as comminution in mineral processing [1], it may cause accelerated degradation of civil infrastructure, such as roads and pavement layers or ballast rail tracks [2], or decreases in the recovery rate in the oil and gas industry due to proppant crushing [3]
Grain breakage brings about changes in characteristics of granular materials, especially in grain size distribution and grain morphology
Summary
Grain breakage is common in granular materials, such as powders, soils, and manufactured aggregates, when subjected to high loading or large deformations. Grain breakage brings about changes in characteristics of granular materials, especially in grain size distribution and grain morphology. These shifts affect the mechanical behaviour of granular media and most prominently the material’s crushing strength against further breakage [4]. In order to obtain a better understanding of sand behaviours in relation to grain-scale damage, a novel loading apparatus capable of conducting compression tests at the high stress on assemblies of grains was designed and developed. Synchrotron Radiation-based X-ray Micro-Computed Tomography (SR-μCT) was used to capture high-resolution 4D images (i.e. 3D monitoring over time) from a sand assembly subjected to compression at different loads
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