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    Concept of Critical Shear Stress in Relation to Characterization of Dispersive Clays

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    A laboratory study has been made on the dispersive behavior of selected clay systems when subjected to the disruptive action of flowing water. The studies were made in a rotating cylinder apparatus and thus were mainly confined to dispersion phenomena on the clay boundary. It was observed that surface erosion was initiated with the removal of individual particles or clusters, due to the relative instability of a particle or domain compared with the remainder of the surface. The chemical system was defined in terms of the cation ratio, and the equilibrium solution concentration, and initiation of motion was fixed by measurement of the critical shear stress. An experimental relationship between the critical shear stress, cation ratio, and total salt concentration was shown for the soils studied and explained in terms of the flocculation-deflocculation characteristics. Taking the criterion of instability as that corresponding to zero critical shear stress proved to be advantageous in this study and helped in a satisfactory demarcation of stable and unstable states.


    clays, flocculating, dispersions, salts, cations, shear stress

    Author Information:

    Sargunan, A
    Professor, Department of Soil Mechanics, College of Engineering, Madras,

    Committee/Subcommittee: D18.02

    DOI: 10.1520/STP27002S