Estimation of the tensile elastic modulus using Brazilian disc by applying diametrically opposed concentrated loads

Abstract

The tensile elastic modulus E t of a rock is different from the compressive elastic modulus E c, due to inhomogeneity and microcracks. There is no convenient method to obtain E t except using direct tension tests. However, the direct tension test for rock materials is difficult to perform, because of stress concentrations, and the difficulty of preparing specimens. We have developed a new method to determine E t of rock materials easily and conveniently. Two strain gauges are pasted at the center part of a Brazilian disc's two side faces along the direction perpendicular to the line load to record tensile strain, and a force sensor is used to record the force applied; then the stress–strain curve can be obtained; finally the E t can be calculated according to those related formulas which are derived on the basis of elasticity theory. Our experimental results for marble, sandstone, limestone and granite indicate that E t is less than E c, and their ratio is generally between 0.6 and 0.9.