BEHAVIOR OF BEREA SANDSTONE UNDER CONFINING PRESSURE .2. ELASTIC PLASTIC RESPONSE

The experimental results presented in part I provided sufficient information about the behavior of Berea sandstone under a large range of confining pressure. In that article, initial Yield and failure surfaces were determined, and a yield and a failure criteria were proposed. Further, a hypoelastic model was given for the initial elastic response of this material, that is, for the response within initial yield surface. This article (part II) contains an elastic-plastic model to deal with the irreversible deformation region. A general yet relatively simple elastic-plastic constitutive model is proposed here, and it is formulated in accord with the experimental observations. In the proposed model, the yield function is obtained by introducing a single scalar growth function for the initial yield function. At this stage of the development of the model, an associated flow rule is used. The validity of the model is examined by comparing its predictions with the experimental results for the different triaxial compression tests on Berea sandstone.