In-plane propagation of shear microcracks in brittle rocks under triaxial compression
The localized separation of the two cracks faces near the tip of a shear microcrack, which is otherwise kept closed by a normal pressure, is suggested as a possible mechanism for the propagation of microcracks in rocks loaded in triaxial compression. Finite element calculations show that when a shear crack runs along a surface of elastic discontinuity (interface between different minerals or between differently oriented domains of an anisotropic mineral), it can remain open at its tip while a normal pressure acts across that part of the crack which has reclosed. Such a separation bubble allows the shear crack to propagate in plane without frictional sliding taking place. It is speculated that dilatancy could be the result of a residual separation of the reclosed crack faces. On the basis this mechanism a heuristic failure model is derived, which can correlate the published trixial failure data of Westerly granite up to a confining pressure of 2000 MPa (20 kbar).
- Research Organization:
- Institut CERAC SA, CH-1024 Ecublens, Switzerland
- OSTI ID:
- 5058011
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 85:B5
- Country of Publication:
- United States
- Language:
- English
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