Journal of the Geological Society · 1974 · 106 citations · 11 references
EngineeringEarth SciencesGeologyMechanical Behavior Of MaterialsRock MechanicsStructural GeologyBrittle Failure Of RockFracture InitiationFracture MechanicsFracture PropagationRock FailureStress In RocksBrittle Fracture TheoryCataclastic DeformationFracture DevelopmentFracture Initiation In Brittle RocksFracturesShear Fracture InitiationShear FracturesStress Distribution
Brittle fracture leading to fault formation proceeds through stages—load‑parallel tensile, load‑normal shear, inclined shear, strength failure, second‑order fracture, and faulting—where the first two stages can be quantified by an elastic flaw concept based on the pre‑fracture stress distribution. The authors develop a stress‑gradient model that departs from conventional brittle fracture theories by incorporating the stress gradient along the fracture path. Experimental data confirm the stress‑gradient model’s validity; the initiation of inclined shear fractures depends on a quasi‑cataclastic state produced by earlier fractures, and because the original elastic stress distribution is destroyed before inclined shear fracture, later events cannot be explained by the elastic flaw model, suggesting a Coulomb‑type mechanism governs inclined shear fracture initiation and propagation.
At the macroscopic scale, the process of brittle fracture, leading to the formation of a macroscopic fault, involves several stages of fracture development. The usual sequence of events consists of the following stages: load-parallel tensile fracture, load-normal shear fracture, inclined shear fracture, strength failure, second order fracture and faulting. The first two stages can be defined quantitatively in terms of an elastic flaw concept which is based on the elastic stress distribution existing around the flaw prior to the appearance of the first fracture. The appropriate theories are developed through a stress model which, in departure from other brittle fracture theories, involves the stress gradient along the fracture path. Experimental results are introduced to demonstrate the general validity of the stress gradient model. The initiation of the first inclined shear fracture seems to be contingent on the existence of a quasi-cataclastic state produced by the earlier sets of load-parallel tensile and load-normal shear fractures. Because the original elastic stress distribution, including the stress anomaly around the flaw, is destroyed before the initiation of the inclined shear fracture, later events of fracture cannot be interpreted in terms of the elastic flaw model • Probably a Coulomb-type mechanism, similar to the one involved in the failure of cohesionless, granular materials, controls the initiation and propagation of inclined shear fractures as well as the development of maximum resistance.
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State of stress in the earth's crust
Tectonophysics · 1964 · 433 citations
Post-failure behavior of a granite and diabase
W.R. Wawersik, W. F. Brace · Rock Mechanics and Rock Engineering · 1971 · 415 citations