Some properties of irregular 3-D particles (original) (raw)
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Cement and Concrete Research, 2006
The shape of aggregates used in concrete is an important parameter that helps determine many concrete properties, especially the rheology of fresh concrete and early-age mechanical properties. This paper discusses the sample preparation and image analysis techniques necessary for obtaining an aggregate particle image in 3-D, using X-ray computed tomography, which is then suitable for spherical harmonic analysis. The shapes of three reference rocks are analyzed for uncertainty determination via direct comparison to the geometry of their reconstructed images. A Virtual Reality Modeling Language technique is demonstrated that can give quick and accurate 3-D views of aggregates. Shape data on several different kinds of coarse aggregates are compared and used to illustrate potential mathematical shape analyses made possible by the spherical harmonic information.
Quantifying the three-dimensional shapes of spheroidal objects in rocks imaged by tomography
The shapes of objects in rocks are sometimes measured through tomographic sections, either 'physical' sections or 'virtual' X-ray computed tomography. Approximation of these objects as ellipsoids is often sufficient in these analyses. Here we present an easily implemented algorithm to best-fit an ellipsoid to a set of n points (n ! 9) distributed on the surface of a spheroidal object observed in tomographic sections. The method is demonstrated on X-ray computed tomography data of 90 chondrules in a CR2 chondrite.
Powder Technology, 2020
Particulate solids or fragments are found in nature and many industrial processes. They are commonly characterized by a number of morphological parameters, for which the mathematical expressions in literature usually come from comparisons to idealized shapes. Whereas these expressions must fit some requirements firstly on common geometric shapes before being used on a real solid particle. In this work, the expressions for calculating morphological parameters based on both projected area (2D) and on three-dimensional (3D) shapes of solid particles were evaluated. Hereof expressions from literature related to the same morphological parameter were identified, and others defined originally on projected area, 2D, were proposed to be used on 3D shapes. The results allowed to indicate the most suitable expression for each parameter based on pre-established criteria. In practice, distinct values obtained from different expressions applied to the same shape make a comparative analysis a complex task, which requests commitment for Standardization.
Particle Shape Quantities and Measurement Tecniques - A review
Electronic Journal of Geotechnical Engineering
It has been shown in the early 20th century that particle shape has an influence on geotechnical properties. Even if this is known, there has been only minor progress in explaining the processes behind its performance and has only partly implemented in practical geotechnical analysis. This literature review covers different methods and techniques used to determine the geometrical shape of the particles. Particle shape could be classifying in three categories; sphericity - the overall particle shape and similitude with a sphere, roundness - the description of the particle’s corners and roughness - the surface texture of the particle. The categories are scale dependent and the major scale is to sphericity while the minor belongs to roughness. The overview has shown that there is no agreement on the usage of the descriptors and is not clear which descriptor is the best. One problem has been in a large scale classify shape properties. Image analysis seems according to the review to be a...
GRANULOMETRIC DETERMINATION OF SEDIMENTARY ROCK PARTICLE ROUNDNESS
A number of subjective and objective methods have been proposed, and are in use, to determine the roundness of sedimentary rock particles. Roundness, which is one of three properties describing the shape of a particle, is a measure of the extent to which the corners and edges of a particle have been worn away.
Representative Elementary Volume Analysis of Sands Using X-Ray Computed Tomography
Geotechnical Testing Journal, 2007
The concept of a representative elementary volume ͑REV͒ provides an effective means of developing macroscopic measures in the description of granular materials. However, due to the difficulties associated with the measurement and characterization of granular microstructure the existence and size of an REV has remained largely conjectural. This study presents a systematic method to examine the characteristics of the REV using X-ray computed tomography images. The 3-D images of spherical glass beads, Silica sand, and Ottawa sand have been characterized using advanced image processing techniques. An interactive computer program is developed to study porosity variation within a sphere with increasing radius from the images of these materials. The porosity variation of Silica sand and Ottawa sand showed three characteristic regions: an initial fluctuation region due to microscopic variations, a constant plateau region, and a region with a monotonic increase/decrease due to heterogeneity. The homogenous medium of glass beads did not show the last region. The results show that for a random packing of spherical glass beads the REV is about two to three times of the identical average diameter. The radius for Silica sand composed mainly of elongated particles is between 5 to 11 times of d 50 and for Ottawa sand composed mainly of subrounded particles is between 9 to 16 times of d 50 .
A new approach to rapid 3D modelling of rock mass structure
Proceedings of the ICE - Geotechnical Engineering, 2010
The prediction of rock mass behavior is an important task in many engineering projects, as the behavior of rock masses can be controlled by the presence of discontinuities. Being able to map the structure of a rock mass is crucial to understanding its potential behavior. This understanding can positively impact the safety and efficiency of an engineering project. In this research, rock masses were mapped and analyzed using linear mathematical transformations and isometric perspective methods to achieve meaningful three-dimensional (3D) results. The rock mass fracture representation is based on explicit mapping of rock faces. The developed model can improve safety and productivity through its application in the determination and analysis of rock mass structure for geological and geotechnical assessment. Based on the methods explained here, a software system was developed for analyzing the geometric characteristics of discontinuities in a rock mass. In this model, discontinuities in a rock mass can be visualized both individually and in combination, and cross-sections can be generated at any desired location. In addition, intersection lines between discontinuities can be generated as dip direction vectors. The natural structure attained by using this developed model agrees well with field measurements.
Solid Earth, 2016
Recent years have seen a growing interest in the characterization of the pore morphologies of reservoir rocks and how the spatial organization of pore traits affects the macro behavior of rock-fluid systems. With the availability of 3-D high-resolution imaging, such as x-ray microcomputed tomography (µ-CT), the detailed quantification of particle shapes has been facilitated by progress in computer science. Here, we show how the shapes of irregular rock particles (pores) can be classified and quantified based on binary 3-D images. The methodology requires the measurement of basic 3-D particle descriptors (length, width, and thickness) and a shape classification that involves the similarity of artificial objects, which is based on main pore network detachments and 3-D sample sizes. Two main pore components were identified from the analyzed volumes: pore networks and residual pore ganglia. A watershed algorithm was applied to preserve the pore morphology after separating the main pore networks, which is essential for the pore shape characterization. The results were validated for three sandstones (S 1 , S 2 , and S 3) from distinct reservoirs, and most of the pore shapes were found to be plate-and cube-like, ranging from 39.49 to 50.94 % and from 58.80 to 45.18 % when the Feret caliper descriptor was investigated in a 1000 3 voxel volume. Furthermore, this study generalizes a practical way to correlate specific particle shapes, such as rods, blades, cuboids, plates, and cubes to characterize asymmetric particles of any material type with 3-D image analysis.