Evaluation of Flattened Brazilian Disc Test to Analyze the Indirect Tensile Strength of Rock
摘要
Rocks are weaker in tension. Therefore, the estimation of tensile strength is crucial in any rock engineering environment. The Brazilian disc test is the most conventional method carried out to evaluate the indirect tensile strength of rock. However, the problem of fracture initiation in Brazilian discs has been a topic of concern for several researchers. High shear stresses tend to develop at the platen-specimen contacts leading to initiation of fracture at the contact. Eventually, researchers suggested plane loading of Flattened Brazilian Discs (FBD) to solve the issue. This modification is done by flattening two diametrically opposite ends of the disc. In FBDs, it is theorized that the crack initiation originates at the center if the loading angle subtended by flat ends (2α) is ≥19.5°. Most of the work regarding FBD specimens is numerical in nature, and a comprehensive experimental evaluation does not seem to have been taken up by previous researchers. Nearly all the numerical analyses assume homogenous and isotropic specimens which are far from reality. Moreover, almost no study has been done on the influence of the strain rate or deformation rate on FBDs. This study investigates the tensile behavior of FBD specimens using granite when loaded under deformation rates of 0.5 mm/min, 1.5 mm/min, and 5.5 mm/min. The loading angles (2α) considered for experimentations are 10°, 20°, 30°, and 40°. The failure patterns are also observed and analyzed.