Brazilian Tensile Test for Soils

Abstract

Analysis and design of impermeable cores of earth dams against cracking require knowledge of the tensile strengths and tensile stress–strain relationships of the concerned soils. The same is needed for any stress and deformation analysis of an earth structure when a portion of it is expected to be in tension. In order to investigate behavior of soils in tension the Brazilian tensile test has been employed and found advantageous over other methods. However the interpretation of results of this test is involved because of the biaxial stress conditions existing at the center of the test specimen. Neglecting this fact leads to erroneous evaluation of the test results, particularly if the moduli in tension and compression differ. A numerical stress solution which considers the difference between compressive and tensile moduli with respect to tensile strength and tensile stress–strain relationship is developed. The magnitude of errors associated with the incorrect assumption of equal modulus in tension and compression is also investigated. The developed procedures of analytical evaluation of a Brazilian test are illustrated in the case of Mica Till, which is considered to be a typical example of a low plastic soil used in cores of earth dams. The results indicate that the Brazilian tensile test is a simple and accurate testing method, requiring however a proper consideration of the difference between a modulus in tension and compression.