Energy dissipation and fault dilation during intact-rock faulting

Rock-failure is usually analyzed by using the stress-based Coulomb criterion with the empirical parameters of cohesion and internal friction. We recently developed an alternative rock failure theory that is based on two conditions: rocks fail under a critical elastic energy threshold, and the applied elastic strain is accommodated by shear and dilation along the faults. We refer to this theory as Critical Energy Fault Failure (CEFF) and demonstrated its applicability to a range of rock failure experimental co nfigurations from uniaxial to polyaxial loadings (Reches and Wetzler, 2022). In the present analysis, we utilized the energy-based CEFF theory to highlight further aspects of rock faulting: A. Evaluation of the dissipated energy associated with rock faulting which revealed that intact rock failure dissipates 35-55% of the available elastic energy. B. For a given normal stress, the CEFF calculated shear strength of a developing fault is smaller than the equivalent of the Coulomb shear strength. C. The predicted dilation associated with faulting of intact brittle rocks that is calculated by CEFF is comparable to experimental observations. These three analyzed subjects provide important contributions for the understanding of rock failure processes. • Failure by faulting dissipated 35-55% of the total elastic energy of the loading system. • Energy-based faulting theory predicts lower shear strength than Coulomb criterion. • Dilation is an integral component of faulting contributing up to 30% of strain and energy dissipation.