Verification of Flattened Brazilian Test on the Tensile Strength Determination of Layered Sandstone

This study investigates the mechanical behavior of layered sandstone under flattened Brazilian disc (FBD) test conditions based on experimental studies and numerical simulations. The tests included 7 group specimens with different dip angles, namely 0°, 15°, 30°, 45°, 60°, 75°, and 90°. The load-deformation curves, failure modes, and tensile strengths are discussed and compared with the conventional Brazilian disc (BD) test results. The experimental results show that the FBD tests generally have two stages of failure modes. In the first stage, the load increases as the displacement increases until it suddenly decreases, with one major fracture occurring in the center of the disc. In the second stage, the load increases again until the specimen is destroyed via a complex fracture mode. Numerical simulations are utilized to analyze the fracture mode of the two stages, indicating that the fracture in the first stage is purely tensile. Hence, the maximum load in the first stage is recommended to estimate the tensile strength under the FBD test.