USING MATERIAL TOUGHNESS TO UNDERSTAND CHEMICAL COUPLING OF FRACTURE PROPAGATION

The material toughness of mode I fracture, G_I^*, may provide insights into the the relative role of different chemical processes on fracture propagation in rocks. Rather than focusing solely on geometric factors and tensile strength, as fracture toughness, K_I^*, does, the material toughness is inversely proportional to the Young's modulus, and proportional to 1-eta^2. Also, in extensions of Griffith crack theory, the material toughness is related to the release of elastic energy from bond breaking, and dissipative processes; this opens an opportunity to using the evolution of G_I during subcritical fracture to distinct processes. To explore the use of material toughness and energy release rate to understand progressive rock damage, we review a series of experimental and field studies, recasting their findings into a material toughness perspective to predict fracture behavior.