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

The tensile elastic modulus Et of a rock is different from the compressive elastic modulus Ec, due to inhomogeneity and microcracks. There is no convenient method to obtain Et 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 Et 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 Et 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 Et is less than Ec, and their ratio is generally between 0.6 and 0.9.