Numerical analysis of the applicability of engineering linear models of inelastic behavior and fracture for the description of porous rocks under confined conditions

Abstract

The paper is devoted to the numerical study of the features of inelastic deformation and fracture of representative mesoscopic volumes of porous brittle materials (including rocks) under the condition of triaxial compression. The study is focused on the analysis of applicability of the classical macroscopic “linear” criteria of plasticity and strength for the description of the mechanical response and assessment of the onset of fracture of representative volumes. Analysis of simulation results confirmed that conventional plasticity conditions (criteria), which take into account the contribution of the local average stress in the linear approximation, are able to adequately describe the mechanical behavior of confined mesoscopic representative volumes of brittle porous rocks only up to the stage of formation of the system of distributed relatively long cracks. We found that material work softening under confined conditions is concerned not with loss of integrity of the sample, but with subsequent formation of localized shear band. The conditions for actual fracture of confined brittle porous rocks are adequately described using “linear” failure criteria with parameters determined on the base of multiaxial compression tests.