Relating strain localization and Kaiser effect to yield surface evolution in brittle rocks

Hannah Gajst*, Eyal Shalev, Ram Weinberger, Shmuel Marco, Wenlu Zh, Vladimir Lyakhovsky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The yield surfaces of rocks keep evolving beyond the initial yield stress owing to the damage accumulation and porosity change during brittle deformation. Using a poroelastic damage rheology model, we demonstrate that the measure of coupling between the yield surface change and accumulated damage is correlated with strain localization and the Kaiser effect. Constant or minor yield surface change is associated with strong strain localization, as seen in low-porosity crystalline rocks. In contrast, strong coupling between damage growth and the yield surface leads to distributed deformation, as seen in high-porosity rocks. Assuming that during brittle deformation damage occurs primarily in the form of microcracks, we propose that the measured acoustic emission (AE) in rock samples correlates with the damage accumulation. This allows quantifying the Kaiser effect under cyclic loading by matching between the onset of AE and the onset of damage growth. The ratio of the stress at the onset of AE to the peak stress of the previous loading cycle, or Felicity Ratio (FR), is calculated for different model parameters. The results of the simulation show that FR gradually decreases in the case of weak coupling between yield surface and damage growth. For a strong damage-related coupling promoting significant yield surface change, the FR remains close to one and decreases only towards the failure. The model predicts that a steep decrease in FR is associated with a transition between distributed and localized modes of failure. By linking the evolving yield surface to strain localization patterns and the Kaiser effect, the poroelastic damage rheology model provides a new quantitative tool to study failure modes of brittle rocks.

Original languageEnglish
Pages (from-to)2091-2103
Number of pages13
JournalGeophysical Journal International
Volume221
Issue number3
DOIs
StatePublished - 2020

Funding

FundersFunder number
National Science Foundation1761912, EAR-1761912
National Science Foundation
United States-Israel Binational Science FoundationBSF 2014036
United States-Israel Binational Science Foundation
Israel Science Foundation1645/19
Israel Science Foundation

    Keywords

    • Fracture and flow
    • Numerical approximations and analysis
    • Numerical modelling

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