Energy Dissipation-Based Method for Brittleness Evolution and Yield Strength Determination of Rock

Abstract Brittleness is one of the most important mechanical properties of rock, especially in designing an efficient fracturing method for deep production of raw petroleum and shale gas. In this study, triaxial compression tests for sedimentary, igneous and metamorphic rocks are carried out to investigate the relationship between brittleness and yield under different confining pressures. To research the yield property in the deformation and failure process of rock, the referenced brittleness index BIM is adopted to analyze the brittle evolution of rock based on the energy dissipation characteristics. The experimental results show that the BIM following increasing axial strain presents N-shaped variation in the deformation process. The two inflection points are exactly marked as the compaction point and yield point in the rock deformation process. Accordingly, the scientific linear correlation between BIM and yield and peak strength is investigated to obtain the response of brittleness to the corresponding stress values increasing under different confining pressures. Based on this correlation, a new method for determining the yield strength by considering the energy dissipation is proposed. In comparison with the fitting correlation, the estimated BIMmax values from other rock strengths are close to the correlation between yield and brittleness (error range within 10 %). Accordingly, the proposed method may provide a reliable estimation of rock yield strength.