Nonlinear Mechanical Behavior of Natural Argillite under Monotonic and Cyclic Loading

Abstract

This paper presents an experimental study on the mechanical behavior of the argillite that was considered as a possible host rock for a high-level radioactive nuclear waste repository in France. A specific mechanical setup with optical observation was used to investigate the behavior of the material at both the macroscopic scale (cm) and the microscopic scale (100 μm). The full-field strain of the material during mechanical loading was obtained by use of the digital image correlation (DIC) technique. A series of uniaxial compression tests under monotonic and cyclic loading were performed on the Callovo-Oxfordian argillite samples to characterize the corresponding elastic and plastic properties. The results showed that the mechanical behavior (elastic modulus, Poisson’s ratio, and plasticity) depended on water content. The obtained strain-stress curve was nonlinear, and this nonlinearity was mainly related to plasticity and time-dependent effects of the material. The heterogeneous behavior related to the mineralogical composition and the damage induced by mechanical loading are also discussed.