Mechanical response and fracture behaviors of pre-cracked granite under time-delayed triaxial compression: Experimental and 3D DEM insights

The time-delayed failure of rocks is a potential geological hazard, and it poses severe challenges to the stabilization and safety in deep rock engineering. To explore the triaxial time-delayed failure process under high-stress conditions, this paper conducts time-delayed triaxial compression (TDTC) experiments on multiple granite samples. A three-dimensional grain-based model (3D-GBM) for pre-cracked granite is constructed. Combined with the parallel-bonded stress corrosion (PSC) model, TDTC numerical simulations are carried out to investigate the triaxial time-delayed damage and fracture characteristics of pre-cracked granite under high-stress levels. The results show that when the stress level k is 85 %, the fracture characteristic of each type of sample is the most obvious. The fractal dimension and damage variable of the type B-30 sample are the largest. The pre-cracked granite 3D-GBM based on the real mineral composition achieves a high consistency between the numerical simulations and the experimental results in conventional triaxial compression tests. For all types of samples, the axial strain confining pressure compliance during the time-delayed deformation stage shows a gradual upward trend as k increases. The fracture degree is most significant when k = 85 % for the same type of samples. The x-direction particle displacement of the type B-30 sample is the largest. The number of intragranular cracks in all samples is generally larger than that of intergranular cracks for k = 85 %.