Bending Properties of Granite Beams with Various Section-Sizes in Three-Point Bending Tests

Abstract

To examine the size effects on the bending strength of rock and determine the relation between Brazilian splitting strength and bending strength, Brazilian splitting tests were performed to measure the indirect tensile strength of rock materials. Three-point bending tests were used to evaluate the bending properties of rock beam by changing the sample cross section size including height, width, and diameter. The peak load increases as section size linearly expands. An exponential relation between the peak load and the cross section area ratio is found for rectangular section with different heights and circular section with different diameters samples, whereas a linear one is observed for rectangular section with different widths samples. The measured peak load ratio for all tested samples actually differs from the theoretical one. The maximum shear stress on the cross section of the sample is linearly affected by the section height and diameter but hardly influenced by the section width. Bending strength is barely affected by section size which leads to the conclusion that no size effect is observed in the tested size range. However, the ratio of bending strength to Brazilian tensile strength is found within 3.81–4.26 for rectangular samples and 3.14–3.48 for circular samples. The obtained bending strength is higher than the Brazilian tensile strength, which is in good agreement with the previous results, and the bending strength to Brazilian tensile strength ratio is associated with the sample section size.