Statistical Micromechanics-Based Modeling for Low-Porosity Rocks under Conventional Triaxial Compression

Abstract

It is acknowledged that porosity and voids encapsulated in rocks significantly affect the mechanical behavior of specimens from laboratory observations. In this study, a proposed conceptual porosity model was idealized to evaluate the change of voids fraction caused by straining, and the equivalent porosity was introduced to indirectly characterize material properties on a macroscopic scale. A micromechanics-based analytical method was developed to track the progressive failure of specimens induced by the localization strains; in particular, the shear-failure factor was assumed to be a cumulative distribution function of the shear straining. On this basis, a phenomenological constitutive model for low-porosity rocks, generally within 5%, was further developed with only a few model parameters. In addition, predictions of multiaxial stress-strain relation and volumetric strains were examined by comparing the observed results from laboratory data. A parametric study was carried out to address how the variation of porosity impacts mechanical behaviors of rocks in the proposed model.