Modification of the Brazilian indirect tensile strength formula for better estimation of the tensile strength of rocks and rock-like geomaterials

Rock mechanical properties are essential input in many design applications in petroleum, mining, environmental and civil engineering. The most reliable source for these properties is the laboratory tests. Among these important rock mechanical properties are the tensile strength. Tensile strength can be measured directly and indirectly. For rocks, the indirect tensile test is the most convenient in terms of samples preparation, testing requirements, and availability of appropriate standards. The most common experimental method used to indirectly estimate tensile strength of rocks is called Brazilian indirect tensile test. It is well documented in the literature that the Brazilian indirect tensile test provides over estimated tensile strength values compared to the direct tensile test. The objective of this work is the investigation of potential modification of the Brazilian indirect tensile strength formula by the analysis of the relevant published laboratory data. Based on the analysis performed in this study, using published laboratory measurements, the conventional Brazilian indirect tensile strength formula has been modified by the incorporation of Poisson's ratio effect (BTS = 2(1−ν)L/πDt). The modified Brazilian indirect tensile strength formula was validated using another set of published laboratory data for various rocks and rock-like geomaterials other than that used initially in the modification process. Direct tensile strength values have been estimated; for various types or rocks; using the modified Brazilian indirect tensile strength formula with an average error of estimate as low as 8% compared to 32.6% before correction. Therefore, the modified Brazilian indirect tensile strength formula (BTS = 2(1−ν)L/πDt) is very promising and suitable for most rocks and rock-like geomaterials having Poisson's ratio value lies between 0.10 and 0.45. © 2020 The Author