Elastoplastic Modelling of Porous Limestones with Porosity Dependency.

In this study, three typical limestones, including Tavel limestone, Indiana limestone, and Lixhe chalk, were selected from a large number of porous limestones. These limestones with different porosities have been largely studied in previous experimental investigations because of the complexity of mechanical behavior. According to previous experimental studies, porous limestones present two basic plastic mechanisms: plastic shear as a response at low confining pressures and plastic pore collapse at high confining pressures. In related to the plastic mechanisms, two types of plastic volumetric deformation are revealed: plastic compaction induced by pore collapse, and plastic dilatancy by plastic shearing. In this paper, a micromechanics-based plastic model is extended to describe the elastoplastic behavior of porous limestones. The plastic criterion of porous rock is explicitly dependent on the porosity in addition to being directly based on the relevant mechanical properties of solid matrix at the microscopic scale. An additional plastic hardening law for the solid matrix is proposed, in which two plastic deformation mechanisms are considered in hardening law of the solid matrix, including hardening effect caused by the local equivalent plastic deformation and weakening effect caused by the increase in porosity. Three typical porous limestones with different porosity are selected to validate the proposed model on both hydrostatic and triaxial compression tests. By comparing numerical predictions and experimental data, it is shown that the presented model can correctly describe the mechanical behavior of porous rocks. Highlights: Limestones with different porosities have been largely studied in previous experimental investigations because of the complexity of mechanical behavior. In related to the plastic mechanisms, two types of plastic volumetric deformation are revealed: plastic compaction induced by pore collapse, and plastic dilatancy by plastic shearing. A micromechanics-based plastic model is extended to describe the elastoplastic behavior of porous limestones. The plastic criterion of porous rock is explicitly dependent on the porosity in addition to being directly based on the relevant mechanical properties of solid matrix at the microscopic scale. [ABSTRACT FROM AUTHOR]