| A comprehensive experimental study of a high porosity rock is carried out to provide the fundamental information for the development of an elastic-plastic constitutive model. This study involves uniaxial and triaxial compression tests (;According to the experimental observations, a failure surface and an initial yield surface are proposed, and since the elastic response of Berea sandstone is non linear, an elastic constitutive model is given in terms of the hypoelasticity theory. The shear and bulk moduli are found to depend on confining pressure and volume strain, respectively, and the equation for this variation with confining pressure and deformation are given. Also a general yet relatively simple elastic-plastic constitutive model is proposed to describe the irreversible deformation of a high porosity rock. 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 different triaxial compression tests for Berea sandstone; predictions using this model agree well with the experimental observations. |
