ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04145.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThis paper presents the results of experimental studies on the microstructure of clay soils, using scanning electron microscopy. Approximately 300 samples of clay soils of various ages, origin and degree of lithification have been analysed. Five main types of microstructure have been identified in clay soils of sedimentary origin, i.e. honeycomb, skeletal, matrix, turbulent and laminar. Among clay soils of sedimentary origin and hydrothermal origin three types of microstructure were distinguished; domain, pseudoglobular and globular.In natural environments, microstructures of mixed features have been found, i.e. honeycomb‐matrix, honeycomb‐skeletal, turbulent‐matrix, etc.The detailed description presented of the different microstructural types comprising morphology and quantitative calculations, shows a close relationship with mineral composition, origin and degree of lithification.In addition physical and mechanical properties as well as the resistance and deformation indices of clay soils have been found to be related to microstructural fea

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04146.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYBehaviour of soils and sediments is generally assessed by laboratory tests of mass property relationships and semi‐empirical equations. A basic approach calls for more detailed information concerning the properties of sediments and manageable methods of calculation. The scanning electron microscope is now providing data concerning the fabic, diagenesis and weathering of sediments. Some sediments are fragile and care is needed in sample preparation to avoid the introduction of artefacts. For example, moisture removal is often accompanied by dimensional change. Freeze drying and critical point drying appear to reduce this problem.Quantitative methods of fabric and texture analysis are being developed, the data being processed by computer. The Fourier method is able to provide quantitative information concerning shape and texture of particles. This sort of information has been used in studies of provenance, correlation, pedogenesis and environmental processes.Examples are given of the use in engineering of fabric and textural data obtained by the Fourier method and by microscop

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04147.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYSurfaces and cross sections of individual quartz sand grains have been examined in both the emissive and cathodoluminescent (CL) modes using a scanning electron microscope. The cathodoluminescent micrographs reveal sub‐surface information not seen in the emissive mode micrographs. The CL features are generally associated with previous stressing, fracturing or abrasion of the grains, and are probably related to the formation of disrupted‐lattice and/or amorphous quartz. The sequence of events during the formation of these features can be identified on many grains by studying the spatial distribution of the most common form of CL contrast—narrow dark bands. On other grains, irregularly distributed dark patches are generally observed to be a surface phenomenon, but the distribution, depth and intensity of these features can be studied by examining cross sections of grains. While it is common for the banded features to cross the entire specimen, it is rare for the diffuse areas to penetrate more than 30 μm. Some grains when experimentally heated above the α‐β transition temperature show a marked change and even a complete reversal in CL contrast.Such studies of grains in cathodoluminescence can supplement the environmental information obtained from emissive mode micrographs of geological

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04148.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYMatching 010 and 001 cleavage faces of a microcline perthite from Arendal, Norway, were hydrothermally etched for increasing periods of time. On both faces the interface between the two felspar phases quickly becomes etched, enhancing the contrast between them and indicating dislocations in the plane of the perthitic lamellae. Moreover, on the 010 face, etch lines reveal dislocations which transect the lamellae parallel to the trace of 001 cleavage. In all probability these dislocations result from the strain arising from partial coherence of the two felspars. The microcline matrix develops innumerable rhomboidal‐shaped etch pits on the 001 face and pits with an elongated parallelogram‐shaped outline on the 010 face. The dominant direction of etching is parallel to the pericline twinning, suggesting that dislocations occur within the pericline twin boundaries. At a later stage micro‐crystalline boehmite develops preferentially in the perthitic lamellae and along the dislocations parallel to the (001) plane. Such sites may be particularly favoured for clay mineral formation during natural weath

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04149.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYSeveral methods exist for quantifying soil fabric information from electron micrographs, but hitherto little interest has been shown in digital computer techniques. This paper describes such a method for the quantitative analysis of the orientation of clay particles in electron micrographs. The intensity distributions across several micrographs have been digitized at up to two million picture points and the data stored on magnetic tape. By examining the gradient of the intensity variations in two orthogonal directions, the resulting intensity gradient vector at each point can be determined. The information from all points in a micrograph can then be plotted as a rosette diagram, or used in a regression analysis to determine the equation of the ellipse which most closely approximates the actual rosette distribution. Finally an index of anisotropy can be estimated from the major and minor axes of the ellipse.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04150.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYUsing the technique of image analysis it is now possible to make advances in the quantification of soil structure which were not previously possible because of laborious methods and techniques. For the purposes of quantification aggregated soil material is distinguished from non‐aggregated soil material. Aggregated material is characterized by the aggregates themselves and inter‐ and intra‐aggregate pores. Basic measurements on aggregates and pores include size, area, perimeter, Feret's diameter and projection, and these are supplemented by derived measurements such as shape, irregularity and orientation. Non‐aggregated soil material is characterized by pore patterns, defined by the types of pores, and their size, statistical distribution, irregularity and orientation. Quantification of structure is important in a number of fields of soil science and these are briefly sum

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04151.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYSamples of remoulded kaolin have been subjected to varying consolidation and shearing stress conditions, and the resulting microfabric has been examined using a scanning electron microscopy and an X‐ray texture diffractometer. Preparation of samples for observation in the SEM involved both freeze‐drying and critical point drying methods. In consolidation experiments, a significant regional variation in the degree of orientation is observed in each sample. An increase in orientation is seen near drainage surfaces. Observations from areas remote from these surfaces on samples consolidated one‐dimensionally show that from 0 kPa to 100 kPa there is little increase in the general degree of orientation. However, the large decrease in voids ratio associated with this change of stress level is achieved by aggregation of particles into domains, the latter being randomly orientated with respect to one another. Above 100 kPa, the degree of orientation increases, as the particles show a tendency to align with their normal vectors parallel to the principal stress direction.These findings are in agreement with the X‐ray texture goniometer studies on impregnated specimens cut from parts of the consolidated samples adjacent to those for scanning electron microscopy studies. The surfaces of specimens for the X‐ray studies were cut orthogonal either to the major principal stress direction or to the space diagonal in σ1, σ2, σ3space.Micrographs of kaolin consolidated one‐dimensionally in one direction and then to a higher stress level in an orthogonal direction show a closely packed near random fabrics. Examination of samples deformed in shear reveal narrow zones, although regular herring‐bone‐shaped kink bands have been seen in the region between two pa

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04152.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYHalite (NaCl), the most common halide mineral, is omnipresent in saline soils and frequent in alkaline soils. The present study, with a scanning electron microscope, is undertaken to evaluate the morphologies of this mineral in soils and a recent sediment.Salorthids, from Iran and Syria, and a recent crust from the beach of a lake, are employed. The major part of the crust on the surface of the soil is composed of diffuse, waxy and massive forms of halite. The morphology is attributed to the hydroscopic nature of the salt which dissolves in its own absorbed water and crystallizes to give these forms. Directly on the crust surface is a layer of thin fibrous halite which shows elongation along the [100] axis. In the porous parts of the crust, secondary growths occur on the waxy and massive forms. The crystallites have a partially developed hexahedral habit and, according to their orientation, appear as cubes or as trigonal pyramids. In some cases the cubes grow along the axis normal to the surface, resulting in prismatic or acicular habits.In salic horizons the massive form is dominant. Euhedral forms only occur on the exposed face of the soil pit or on the pit floor. Perfect cubes—hexahedral—develop h

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04153.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe accumulation of clay and organic material, forming argillans and organans, is poorly understood and is at least not a subject of general agreement. Electron scanning and microprobe show striking features. The argillans, having Si, Al and Fe, are clearly layered and seldom cracked. The organans do not contain Si, but either Al only, or Al and Fe, are not layered, but are composed of discrete very small bodies, stacked at random. They have a strong polygonal cracking pattern, indicating a shrinking process.The morphology of argillans seems inconsistent with a flocculation process, which would give a porous structure with much water, so that the strong layering is obviously due to a slow deposition of layer silicates out of a dispersed phase.The organans are formed by deposition of gel‐like organo‐metallic compounds and evaporation of the solvation water, causing a strong shrink

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1980.tb04154.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY