Experimental and DEM analysis of granite multi-angle centrally single-cracked Brazilian disks (CSCBD) fracture behaviors

Brazilian splitting tests were performed on granite disk samples (ϕ50 mm × 25 mm) with five-angle (0°, 20°, 40°, 60°, and 90°) cracked fissures to study the fracture characteristics of granite multi-angle centrally single-cracked Brazilian disks (CSCBD). The loading rate in the laboratory test and the numerical simulation were both 0.10 mm/min. The stress–strain response, crack extension, and distribution were obtained. The change patterns of peak strength, peak strain, and elastic modulus and the correlation of acoustic emission characteristics with the fracture mode were analyzed. An efficient three-dimensional clump (3D-Clump) numerical model construction method for pre-cracked granite in three-dimensional particle flow code (PFC3D) based on the discrete element method (DEM) was used to construct five-angle centrally cracked granite Brazilian disk samples. The failure pattern of samples and the evolution characteristics of interparticle parallel bond force in the numerical simulation were explored. Results indicate that the single crack surface significantly affects the damage strength of the disk samples, and the strength of the samples has a prominent difference with different angles of the single crack. When the angle is 0°, 20°, 40°, and 60°, the cracking point of the sample deviates from the endpoint of the precast fissure. When the sample undergoes a significant brittle fracture, the acoustic emission count curves mainly show the characteristics of peak distribution. The failure modes in computational experiments are similar to those in the laboratory experiments. The samples show mainly tensile damage, with more red tensile cracks than green shear cracks. With the increasing damage, the parallel bond force between the particles reaches the loading limit, breaking the bond. At this time, the local damage of the sample gets its limit, forming macroscopic cracks.