A novel methodology for measuring the tensile strength of expansive clays

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Several experimental techniques (viz., triaxial tests, direct tensile tests or suction measurements) have been developed and employed by earlier researchers to measure the tensile strength of fine-grained soils. However, these studies yield results that are soil specific and dependent on the methodology adopted. Apart from this, due to the bulk form of the sample, the sample heterogeneity (i.e., both in terms of the density and the moisture content) influences test results to a great extent. Under this situation, and in the absence of guidelines regarding sample thickness, determination of the tensile strength of expansive clays by employing their thin samples (1 mm to 5 mm) appears to be an excellent alternative. With this in view, efforts were made to determine the tensile strength of expansive clays by resorting to techniques that deal with measurement of (a) the deflection undergone by a silicon wafer, due to air-drying of a thin film of these clays, with the help of a laser beam and (b) the suction by employing a dewpoint potentiameter, WP4. Results obtained from these techniques were critically evaluated vis-à-vis those obtained from triaxial tests and empirical relationships reported in the literature. It has been observed that there is a unique relationship between the results of the thin and thick samples and hence thin samples of expansive clays can be employed for determining their tensile strength. This shows the usefulness of the proposed techniques for measuring the tensile strength of expansive soils.