Quantification of Plasticity and Damage in Berea Sandstone through Monotonic and Cyclic Triaxial Loading under High-Confinement Pressures

This work presents indirect tensile tests and uniaxial and triaxial monotonic and cyclic compression tests of Berea sandstone (BST) under different levels of confining pressure (CP) where the axial and lateral strains are measured in addition to the axial stress. Based on these experiments, the influence of the CP on the mechanical behavior and the damage mechanics of BST is investigated. Results reveal a strong influence of the applied CP on the strength of the material, where BST switches from brittle to ductile due to the presence of the CP. Damage-controlled tests are exploited to quantify the evolution of plasticity and damage as a function of the applied axial load, as well as the CP level. Experimental analysis imparts damage and plasticity rates with respect to the applied axial load to get lower as the CP increases. To the authors' best knowledge, very little work has been conducted on carefully quantifying plasticity and damage of rocks, especially using cyclic loading at high confinements. The proposed experimental methodology in this work of damage and plasticity quantification delivers a baseline blueprint to refine triaxial experimental data for the sake of development and accurate calibration of advanced constitutive models.