Energy Criterion of In-plane Fracture Propagation in Geomaterials with Rotating Particles
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In-plane propagation of tensile fractures (Mode I cracks), shear fractures/bands (Mode II cracks) and compaction bands (Mode I anticracks) is routinely observed in geomaterials in the presence of high compressive stress. While the in-plane propagation of tensile cracks is expected, the mechanics of in-plane propagation of shear cracks is not clear. We propose a unified criterion of in-plane growth of these types of fractures based on the assumption that the grains are able to undergo independent relative rotations. The relative rotations break the binder between the grains even in the presence of high compressive stress. An asymptotic model is developed for long fractures showing that the energy release rate is controlled by the conventional Mode I and II stress intensity factors. The proposed unified criterion of fracture growth compares the energy release rate with the specific fracture energy consisting of three terms: the fracture energy of the bonds (present in all three types of fracture), specific energy of shear (for shear fractures/bands) and specific energy of compaction (for compaction bands). We developed estimates for all three components of the specific fracture energy.
KeywordsStress Intensity Factor Energy Release Rate Hydraulic Fracture Shear Fracture Tensile Crack
We acknowledge financial support from ARC Linkage Grant LP120200797. The paper is a part of research under the initiative ‘Engineering for Remote Operations of the Faculty of Engineering’, mathematics and Computing of the University of Western Australia.
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