Abstract
Digital image processing (DIP) is used to measure shape properties and settling velocity of soil particles. Particles with diameters of 1 to 10 mm are arbitrarily sampled for the test. The size of each particle is also measured by a Vernier caliper for comparison with the classification results using the shape classification table. The digital images were taken with a digital camera (Canon EOS 100d). Shape properties are calculated by image analysis software. Settling velocity of soil particles is calculated by displacement and time difference of images during settling. The fastest settling particles are spherical shaped. Shape factors well explain the difference of settling velocity by a particle shape. In particular, the aspect ratio has a high negative correlation with residual of settling velocity versus mean diameter. Especially, DIP has a higher applicability than classification using the shape classification table because it can measure a number of particles at once. The settling velocity of soil particles is expressed as a function of mean diameter and aspect ratio.
Highlights
E aim of many researches on the study of the settling velocity is to make precise, general formula for prediction of settling velocity [1,2,3,4,5,6]. e shape of sediment particles can be divided into ideal spherical and nonspherical. e settling velocity of spherical particles can be predicted to be more than 98% accurate [7]
To compare with the classification result using the shape classification table, the particle shape is measured by a Vernier caliper and digital image processing (DIP) method. e settling velocity equation uses shape properties measured by the DIP method instead of 3-dimensional shape indexes for high applicability
Classification of the Particle Shape by the Shape Classification Table. e size of a soil particle could be given by 3dimensional as the shape of particle is commonly nonspherical. e major (A), intermediate (B), and minor (C) axes of the particle are measured by a Vernier caliper, and each particle is classified by the shape classification table [31]. e shape classification table classifies soil into 9 groups according to elongation ratio ( B/A) and flatness ratio ( C/ B). e shape classification table is plotted in Figure 5(a). e shapes of nonspherical soil are classified into 4 groups such as sphere, short rod, thick plate, and ellipsoid (Figure 5(b))
Summary
E aim of many researches on the study of the settling velocity is to make precise, general formula for prediction of settling velocity [1,2,3,4,5,6]. e shape of sediment particles can be divided into ideal spherical and nonspherical. e settling velocity of spherical particles can be predicted to be more than 98% accurate [7]. To predict settling velocity of nonspherical particles, researchers propose a shape index to explain the effect of the particle shape on settling velocity [11,12,13,14,15,16,17,18,19,20]. Most of the shape indexes well represent the difference in settling velocity according to the particle shape, but they have a poor applicability because the measurement of the 3-dimensional particle shape is inconvenient. E objective of this paper was to measure particle shape and settling velocity of nonspherical soil by DIP and develop the empirical prediction formula of settling velocity considering the particle shape and diameter. E settling velocity equation uses shape properties measured by the DIP method instead of 3-dimensional shape indexes for high applicability To compare with the classification result using the shape classification table, the particle shape is measured by a Vernier caliper and DIP method. e settling velocity equation uses shape properties measured by the DIP method instead of 3-dimensional shape indexes for high applicability
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