Experimental and numerical study of the effect of fatigue on the strength and deformation behavior of granite rock

Fatigue in rocks is a time-dependent failure mechanism caused by repeated cyclic loading, which leads to progressive microcracking, reduction in strength, and eventual sudden failure at stress levels lower than those under static loading. This problem is of critical importance in engineering applications such as mining, tunneling, dam foundations, and underground energy storage, where rock masses are frequently subjected to seismic vibrations, blasting shocks, or machine-induced dynamic loads. Despite its significance, predicting rock fatigue remains challenging due to the heterogeneous nature of rock, experimental limitations, and the lack of universally validated models. In this research, the fatigue behavior of granite rock was investigated through a combined experimental–numerical approach. Laboratory cyclic uniaxial compression tests were performed to evaluate fatigue life, followed by numerical simulations using the Finite Difference Method (FDM) with FLAC۳D code and the Finite Element Method (FEM) with ABAQUS software. The models were developed under assumptions of homogeneity, isotropy, and intact rock behavior. Sensitivity analyses were conducted to study the effects of loading cycles, confining pressure, and sample scale. The novelty of this study lies in the comparative evaluation of FDM and FEM approaches for predicting rock fatigue, the integration of laboratory data with numerical modeling for validation, and the systematic analysis of multiple influencing factors (loading cycles, lateral stress, and scale). Results showed that cyclic loading significantly reduces rock strength and elastic modulus compared to static conditions. For example, fatigue life decreased with higher cycle numbers, while confining pressure increased strength and delayed failure. Larger specimens also exhibited longer fatigue life due to stress redistribution. This research contributes to a deeper understanding of fatigue in brittle rocks and provides practical insights for the safe design of rock engineering structures under dynamic conditions. Future improvements could focus on incorporating discontinuities, anisotropy, and particle-scale modeling to better capture the complex mechanisms of fatigue in natural rock masses.

کلیدواژه ها:

Rock fatigue ، Strength ، Deformation ، Experimental tests ، Finite Difference Method (FDM) ، Finite Element Method (FEM)