Kenneth Pye
Associates
Ltd.
Scientific Research,
Consultancy and Investigations
.
..
Particle shape: a review and new methods of characterization and classification
...
|
|
|
Abstract Blott, S.J. and Pye, K. (2008) Particle shape: a review and new methods of characterization and classification. Sedimentology 55, 31-63. Shape is a fundamental property of all objects including sedimentary particles, but it remains one of the most difficult to characterise and quantify for all but the simplest of shapes. Despite a large literature on the subject, there remains widespread confusion regarding the meaning and relative value of different measures of particle shape. This paper re-examines the basic concepts of particle shape and suggests a number of new and modified methods which are widely applicable to a range of sedimentological problems. It is shown that the most important aspects of particle form are represented by the I/L ratio (elongation ratio) and S/I ratio (flatness ratio). A combination of these two ratios can be used to classify particles in terms of 25 form classes. A method of obtaining a quantitative measure of particle roundness using simple image analysis software is described, and a new visual roundness comparator presented. It is recommended that measurements of both roundness and circularity (a proxy measure of sphericity) are made on grain images in three orthogonal orientations and average values calculated for each particle. A further shape property, irregularity, is defined and a classification scheme proposed for use in describing and comparing irregular or branching sedimentary particles such as chert and coral. Click to download the visual comparators and graphical plots for use in analysing and displaying particle shape data |
|
|