Determination of the direct tensile strength of granite rock by using a new dumbbell shape and its relationship with Brazilian tensile strength

Abstract

In this study, the determination of the direct and indirect tensile strength of granite rock was carried out in compliance with related standard test methods. In order to analyze rock tensile strength between direct (with using a new dumbbell shape) and indirect (Brazilian tensile strength) test methods were conducted and obtained results were compared between them. A new dumbbell shape samples were used in direct tensile tests and cylindrical specimens, which have different t/D ratios such as 0.5, 0.75, and 1.0, were used in Brazilian tests. Moreover, stress distribution and the stress intensity within the sample were analyzed with Finite Elements Method (FEM) and numerical modeling techniques by using ANSYS R18 software. The direct tensile test yielded lower strength values than the indirect test. For the specimens tested in direct tensile test, failure occurred middle of the dumbbell shape sample due to lower stress intensity factor. Since Brazilian disc test, stress value in the diametrical line of the specimen has been found higher than nominal stress value according to FEM, tensile strength value that should be re-calculated by using any coefficient. Moreover, t / D ratio did not affect the Brazilian test results.