Acoustic emission and breakage mechanism analysis on gypsum-filled granite specimens with varying notch dimensions under uniaxial compression testing

This research investigates how inserting notched gypsum filling between granite specimens affects their breakage under uniaxial compressive testing. Various thicknesses of gypsum filling slabs were placed between granite specimens, incorporating different dimensions and notch configurations. The investigated parameters include elastic modulus, Poisson’s ratio, uniaxial compressive strength, and Brazilian tensile strength of 5 GPa, 0.18, 7.4, and 1 MPa, respectively. Compression testing, at an axial load rate of 0.05 mm/min, was conducted on a total of 9 different models. Numerical simulations were performed on models with notched gypsum filling, varying thicknesses, and notch angles using Particle Flow Code in 2D. The results demonstrated that breakage behavior was primarily influenced by filling thickness and notch angle. The uniaxial compressive strengths in samples were found to be affected by fracture patterns and the breakage mechanism of the filling. The study revealed that the behavior of discontinuities is influenced by the number of induced tensile cracks, which increase with thicker filling. Acoustic emission (AE) hits during loading’s initial phase, a rapid increase in AE hits before the applied stress reached its peak, and significant AE hits accompanying each stress drop were observed. The breakage patterns and strengths were found to be similar in both experimental and numerical approaches.