Numerical modelling of the cyclic behaviour of rock material in the context of underground pumped storage hydroelectricity

The use of old mines as a reservoir in the context of pumped storage hydroelectricity rises the question of their stability especially upon cyclic loading due to filling and emptying the mines. This paper presents the formulation of a new constitutive law able to represent the inherently cyclic behaviour of rocks at low confinement. The main features of the behaviour evidenced by experiments in the literature depict a progressive degradation and deformation of the material with the number of cycles. A constitutive law based on a boundary surface model is developed. It represents the brittle failure of the material as well as its progressive degradation. It also encompasses a fatigue resistance under which no degradation of the material holds. Parameters are calibrated with respect to laboratory experiments from the literature. A parametric study is carried out to highlight the role of different parameters.