ELECTRON MICROGRAPHS OF CONSOLIDATED CLAYS

Abstract

Insignificant work has been done on X-ray diffraction analysis and scanning electron microscopy on Indian soils. The present study deals with clays only.. The minerals present in different clay samples were determined by preparing , the slides of clay suspension and using X-ray diffraction method. The geotechnical properties of clays such as Atterberg limits, specific gravity, percentage of clay particles were determined. The electron micrographs of prepared slides were also obtained by SL1V, and thereby the size, orientation, effect of treatment by different methods, type of structure were evaluated. The concepts of soil microstructure are evaluated and the methods 'of quantitative expressions of micrographs are established. In this thesis SEND study is utilized for the study of particle orientation changes in clayey soils induced due to the consolidation. Observations of the micrographs of both horizontal and vertical sections suggest that the particles orientation increases under increasing pressure. The structure is mainly found to be flocculated and dispersed. Quantitative evaluation of the structure is done by several methods. In the first method the degree of particle orientation is evaluated as a function of void ratio and permeability using the Kozeny- C arman.' s equation for the results of consolidation tests. Increa-sed degree of consolidation indicates the preferred orientation. In the second method, vector mean direction and vector magnitude - iv - of particle inclination are calculated. The vector magnitude increases with increase in stress levels and the directional tendency of vector mean tilts towards horizontal with increase in pressure. In the third method Rayleigh probability is evaluated to assess statistical significance of preferred orientation of particles. Finally the deviation (b) of vector mean from the vertical is studied and 6 is found to increase with increasing consolidation pressure.. Circular frequency histograms are also drawn to assess particle orientation and rotation under different stress conditions.