Numerical analysis of the flattened Brazilian test: Failure process, recommended geometric parameters and loading conditions

The Brazilian test (BT) has been criticized since crack initiation occurs away from the center of the disk due to the stress concentrations at the loading ends. Therefore, two parallel flat ends are introduced into the disk to improve the distribution of the stress. This approach is called the Flattened Brazilian Test (FBT). To investigate the validity of this method, a Discrete Element Method (DEM) using the Flat Joint Model (FJM), which can characterize brittle rock appropriately, is adopted in the present study. The crack propagation and horizontal stress distributions of BT and FBT are compared, the effects of the loading conditions are explored and the recommended geometric parameters are investigated. Notably, the stress concentration weakens in FBT, and the crack initiates from the center portion of the disk. This method can be used to determine the tensile strength of brittle rock and applied to various geometric specimens within certain limits.