Effects of un-parallel notches on the granite fracture properties and acoustic emission phenomena under biaxial test: PFC computation and experimental verification

To assess connections between these notches throughout fracture formation under stress, the mechanical performance of granite specimens with two non-parallel notches underwent a biaxial compression test. The first notch had a 45 degrees angle, whereas the second had a variable angle (0 degrees, 45 degrees, 90 degrees, 130 degrees, and 180 degrees). Three ligament angles (0 degrees, 45 degrees, and 90 degrees) were measured between the inner tips of two notches and the horizontal axis. The ligament length, distance between the inner tips of the two notches, and both notch lengths were each 2 cm. These samples were examined at 0, 1, and 3 MPa confining pressures. By using the particle flow code (PFC), simulated results of the evaluations were run after the trials. It was discovered that the specimens' failure strengths were influenced by the notch's geometric characteristics, which in turn impacted the failure mechanism as well as fracture geometry. The number of tensile fractures had an impact on the specimens' failure strengths. Whilst also increasing the ligament angle, more induced tensile cracks were produced. In the early stages of loading, just a few AE events were found, but after that, they multiplied quickly before approaching the peak stress. By raising the confining pressure, the AE hits were increased and delay failure was occured. The failure strength and AE hits are significantly impacted by the second notch's angle. In constant ligament angel, the compressive strength of models containing overlapped joint were more than that with non-overlapped joints. In models containing non-overlapped notches, the model with ligament angles of 0 degrees and 45 degrees had maximum and minimum compressive strength, respectively. In models containing overlapped notches, the model with ligament angles of 90 degrees and 45 degrees had maximum compressive strength and minimum compressive strength, respectively. In all ligament angles, minimum compressive strength was occurred when the upper joint angle was 45 degrees. Both the computational and experimental methodologies showed that the specimens' failure pattern and compressive strength were very comparable.