Modeling of dilatancy effect in layered rock with rough interfaces using micropolar continuum

Rock formation such as shale normally has a layered structure where the rock blocks interact with each other by their interfaces like head joints and bed joints. In practical geological conditions, such interfaces are often rough and able to result in dilatancy and volume change of the overall geological structure. The dilatancy can be an important effect and cannot be neglected in determining the practical mechanical behavior of the layered rock. The purpose of this paper is to study the dilatancy effect on the mechanical behavior of layered rock structures with rough interfaces. Interfaces with various roughness are defined to evaluate the dilatancy effect. To estimate the stiffness properties of rough surfaces, a dilatancy model known as the contact density model is used. The current problem involves the size effect of the interface which must not be neglected, thus, a homogenized micropolar continuum is taken into consideration. According to the principle of energy equivalence, a homogenization method is used to get the constitutive parameters of the micropolar model. The present problem is analyzed by using finite element numerical codes to show the validity of the dilatancy models in combination with micropolar theory for a layered rock structure.