Fracture characteristics and energy evolution analysis of pre-cracked granite under uniaxial compression based on a 3D-Clump model

To develop a numerical model that can truly reflect the internal structure and mechanical properties of pre-cracked granite realistically, an efficient method for constructing a three-dimensional Clump (3D-Clump) numerical model of pre-cracked granite was proposed based on three-dimensional Particle Flow Code (PFC3D) in this paper. Laboratory uniaxial compression experiments and numerical simulations were conducted on six different pre-cracked granite cylinder specimens with the dimension of ϕ50 mm × 100 mm to obtain the stress–strain response and damage modes. The axial loading rate on the specimens and numerical models was 0.10 mm/min. The relative errors of peak strength σp and elastic modulus E were also compared and analyzed. The relationship between each energy and the variation of stress–strain and cracking during the loading process of numerical simulation was also explored. Results indicate that the relative errors of peak strength and elastic modulus between numerical simulation and laboratory experiments are below 5.00 %. The consistency between the experimental and numerical results indicates that the proposed 3D-Clump numerical model of pre-cracked granite is reliable. A wider damage zone forms in the numerical model at the interconnected crack between the pre-cracked endpoints or at the secondary crack, which is in good agreement with the damage mode of the laboratory experiment. Before the peak point under uniaxial compression in the numerical simulation is mainly the storage of elastic strain energy and the slow dissipation of energy. After the peak point, the elastic strain energy releases sharply, the dissipation energy increases rapidly, the microcrack extension rate increases sharply, the slip dislocation appears obviously, and the crack penetration leads to the destruction of the specimen eventually.