Abstract
The particle shape of coral sand is a crucial factor that affects its accumulation characteristics. Two-dimensional particle images of coral sand with different particle sizes were obtained through optical imaging, and the basic size parameters of particles were measured by digital image processing. The particle shape parameters were created, and on this basis, the variation of shape parameters with size, the distribution characteristics, and the sensitivity of shape parameters were analyzed by mathematical statistics and the fractal theory. In addition, a comparative analysis was conducted for the particle shape and bulk density of coral sand and quartz sand with the same particle size. The results show that (1) for coral sand with particle size ranging from 0.5 to 5.0 mm, as the particle size augments, its overall profile coefficient grows, while the flatness, angularity, and roughness diminish and the particle shape deviates more from the regular circle. (2) The shape of coral sand particles exhibits good fractal characteristics, and the particle shape gets more complex as the particle size grows as evidenced by the fact that the fractal dimension enlarges. (3) All the shape parameters obey a skewed distribution. Concerning the sensitivity to the change in particle shape, the flatness occupies the first place, the overall profile coefficient and angularity come second, and the roughness ranks third, accordingly. It is suggested that flatness should be preferred as the evaluation parameter of the particle shape. (4) Compared with that of quartz sand, the particle shape of coral sand is more irregular, and the intergranular pores are larger under the same accumulation conditions, which is the primary reason why the specific gravity of coral sand is greater than that of quartz sand while the bulk density is smaller than that of quartz sand.
Highlights
Recent years have seen large-scale hydraulic reclamation projects launched by China in the South China Sea
(4) Compared with that of quartz sand, the particle shape of coral sand is more irregular, and the intergranular pores are larger under the same accumulation conditions, which is the primary reason why the specific gravity of coral sand is greater than that of quartz sand while the bulk density is smaller than that of quartz sand
The results of relevant studies [19,20,21,22,23,24,25] indicate that a change in the particle shape of sand may lead to a change in the particle arrangement and intergranular pores, thereby exerting a remarkable impact on its physical and mechanical properties
Summary
Recent years have seen large-scale hydraulic reclamation projects launched by China in the South China Sea. More scholars tend to use two-dimensional particle shape scanner and digital image processing technology to study the two-dimensional shape of granular materials and its impact on the physical and mechanical properties, achieving abundant research results. Owing to its special marine biological origin, coral sand, which is often accompanied with cementation [47,48], features high porosity ratio [49,50], easy breakage [51,52], and other physical and mechanical properties that are significantly different from those of terrigenous sediments It has not been confirmed by experimental data whether the above research results are applicable to coral sand. The research results provide a deep understanding of the sedimentation characteristics of coral sand from microscopic and mesoscopic level
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