A fatigue constitutive model for rock masses based on cross-applications of rheological theory

In geotechnical engineering construction and underground ore mining, periodic cyclic fatigue loading is a major cause of rock mass instability and failure. With a constitutive model, the fatigue characteristics of rock masses can be studied effectively. Based on the similarities between rock mass rheology and cyclic fatigue loading, this paper applies rheological theory to study the fatigue characteristics of rock masses. Two constitutive models that describe different stages of nonlinear mechanical behaviour during the fatigue process were proposed, and a fatigue constitutive model that accurately describes the mechanical properties of rock during different fatigue stages was established after combining the two models. A sensitivity analysis showed that the model parameters E-K, gamma and delta can effectively reflect the deformation and damage evolution characteristics of the rock mass during the three fatigue stages. By comparing the laboratory splitting and three-point bending fatigue experiment results with the calculated model values, the rationality, reliability, and application scope of the model were verified. Moreover, based on the model parameter inversion results, the evolution mechanism of the rock mechanical properties during the different fatigue stages can be accurately understood.