The Influence of Physico-Chemical Factors Upon the Mechanical Properties of Clays

Abstract
The engineering problems of clay soils are closely connected with the “bulk properties,” i.e. shear strength and deformation properties as function of stress conditions and time. These properties are based upon factors in the atomic range and can never be understood without an understanding of the fundamental processes.The bulk properties of virgin sediments differ from those of chemically or mechanically altered clays (called hypo-metamorphic).The difference in view generally held by soil mechanics engineers and ceramic research people concerning soil-water systems as built up of minerals in contact with or separated by water, may only be apparent. The water at the mineral surfaces appears to have properties of a solid substance but not the atomic arrangement of ordinary ice. Within a small area, as at the points “of contact,” the H’s and O’s may take the arrangement of a perfect solid. The movement of a corner of one mineral along the plane of another can only take place if flow or creep in the condensed water is possible. In perfect crystals we have only elastic deformation or yielding. The secondary consolidation of clays and the permeability at low hydraulic gradients are discussed as functions of the physics of the water. The influence of temperature and electrolytes upon the properties is suggested as fundamentally important. A plea for further research in the physics and chemistry of surface processes on the various clay minerals is given.

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