P. Smart

Particle Arrangements in Kaolin

An ambiguity in interpretation of electron micrographs of replicas of fracture surfaces of dry clay samples is illustrated, and a method of making ultra-thin sections described. Micrographs of ultra-thin sections of remoulded, consolidated, and sheared kaolin specimens are shown. In unconsolidated specimens random arrangements of particles, or of small groups of particles, were found. In failure zones, in sheared samples, the preferred orientation was parallel to the zone, with, in some cases, a subsidiary zone in which particles were inclined to the main zone. Interparticle contacts were mainly edge-to-edge or face-to-face.

Automatic orientation mapping of some types of soil fabric

Abstract A technique is described which can automatically delineate regions of micrographs of soils which have a similarly oriented microfabric. This is achieved by an initial pass over a digitized image using an intensity gradient algorithm to specify the orientation at each pixel. Each pixel is then given a value according to this computed direction. A second pass over the image examines the values attributed to each pixel. If, within the neighbourhood of a pixel, one particular general orientation class is dominant then the central pixel is assigned a grey-scale value appropriate to that class. The resulting image shows regions of the image which are aligned predominantly in a given direction. The resulting domain-segmented image may also be combined with the original to generate an image showing the normal grey tonal range, but overlaid with colour washes according to the general orientation of the features in the image at that location. Quantitative parameters, such as the degree and direction of preferred orientation, may be derived from both the initial intensity gradient analysis and also the domain-segmented image. All the steps may be combined in a batch processing mode to automatically analyse several images sequentially.

Circular hough transform for roundness measurement of objects

Abstract We propose a method, based on the Circular Hough Transform, for finding the “sharpness of the corners” of a curve in a plane. An efficient method for computing the Hough transform for this purpose is also presented, as is an additional application of the method to finding the intrinsic equation of a curve and the evolute of a curve.

Quantitative Orientation Analysis of Soil Microfabric

Abstract By evaluating the intensity gradients in two orthogonal directions at each pixel in digitized images of soil microfabric, it is possible to quantitatively assess the degree of orientation of features in that image. The results may be displayed as rosette diagrams, or processed further to evaluate an index of anisotropy which may be compared with external physical factors such as the stresses applied to the soil. Various formulae for deriving the intensity gradients have been considered. Simple arrays utilizing only the neighbouring pixels tend to show rosette diagrams showing a preference towards certain selected angles. More complex formulae have been developed in which any number of pixels in an array centred on the picture point of interest are included. These new formulae can provide improved estimates of the orientation of soil microfabric. The techniques described are applicable to any digitized image, and a selected number of such images of deformed clays are presented to illustrate the technique.

Optical Microscopy and Soil Structure

USE of a photometer in conjunction with a polarizing microscope has yielded useful information regarding the structural anisotropy of soil mechanics test specimens.

Quantitative methods to determine microporosity in soils and sediments

Abstract Tovey, N.K., Smart, P. and Hounslow, M.W., 1994. Quantitative methods to determine microporosity in soils and sediments. In: A.J. Ringrose-Voase and G.S. Humphreys (Editors), Soil Micromorphology: Studies in Management and Genesis. Proc. IX Int. Working Meeting on Soil Micromorphology, Townsville, Australia, July 1992. Developments in Soil Science 22, Elsevier, Amsterdam, pp. 531–539.

Semiautomated analysis of clay samples

Important information about physical characteristics of clays can be inferred from the distribution of the orientations of straight lines in photographs of cross sections of its samples. This article describes the development of a semiautomated system for clay analysis that is based on the application of computer vision techniques. Due to the inherent complexity of these techniques, two strategies have been used in order to reduce the execution time: an effective technique, the binary Hough transform, is applied for detection of straight lines and the transputer is used to enhance the system processing power. The article includes the characterization of the clay analysis application, the description of the binary Hough transform for detection of straight line segments, the presentation of the semiautomated system, and a complete illustrative example.

Strength of weathered rock

Abstract An approximate analysis of the deformation of an ideal model of weathered rock, consisting of cubical blocks of intact rock set in a continuous clay matrix, leads to expressions for the anisotropic constitutive constants of an equivalent continuum in terms of the degree of weathering. The rigidity of the massif is seen to decrease rapidly during the early stages of weathering. A comparison with some field data is included; and the analysis is extended, tentatively, to the onset of yield.

Automatic Analysis of Microstructure of Cohesive Sediments

Qualitative interpretation of electron micrographs of soils and sediments is both useful and necessary (see, e.g., Smart and Tovey, 1981; Grabowska-Olszewska et al., 1984; Bennett and Hulbert, 1986). However, quantitative instrumental interpretation is needed: 1. to express more precisely that which can be seen by eye; 2. to present data in a form suitable for statistical testing; 3. to retrieve information that cannot be obtained by eye; 4. to release expensive staff for productive work.

Microstructural classification of clayey sediments

Progress is being achieved in developing automatic methods of image analysis of electron micrographs for measuring the strength and direction of local preferred orientation, recognition of random areas, and measuring local variations in void ratio and other parameters. Such methods are necessary to provide a better microstructural classification of these sediments.