Insight of molecular simulation to better assess deformation and failure of clay-rich rocks in compression and extension

Abstract

Clay minerals constituent an essential component of clayey rocks. Macroscopic mechanical behaviors of those rocks can be significantly driven by local deformation and failure processes of clay minerals. In this study, the mechanical behavior of Montmorillonite (MMT) crystal at the atomistic scale is investigated by using molecular dynamics (MD) simulations. In accordance with macroscopic laboratory tests, both triaxial compression and extension with constant mean stress are considered. A series of MD simulations are performed for these two loading paths with different values of mean stress and respectively applied in the parallel and perpendicular directions to crystal layers. It is found that the mechanical behavior of MMT crystal exhibits a clear dissymmetry between compression and tension, a strong anisotropy along two loading orientations and an important dependency on mean stress. The inter-layer space collapse and atomic sheet bending are two failure mechanisms of the crystal structure. The results issued from MD simulations provide a microscopic insight into macroscopic deformation and failure of clay-rich rocks.