The Brittle‐Ductile Transition in Porous Limestone: Failure Mode, Constitutive Modeling of Inelastic Deformation and Strain Localization

Baud, Patrick; Hall, Stephen A.; Heap, Michael; Ji, Yuntao; Wong, Tak‐Lam

doi:10.1029/2020jb021602

Cited by 25 publications

(8 citation statements)

References 69 publications

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“…The in‐band flow behavior featured a dilatancy angle near zero at 10 MPa, slightly above zero at 15 MPa, and about 0.35–0.4 for nearly all samples tested at confining pressures of 20 MPa and above. Similar behavior has been observed in poorly lithified rocks (Baud et al., 2021).…”

Section: Resultssupporting

confidence: 85%

Micromechanics and Strain Localization in Sand in the Ductile Regime

Shahin

Hurley

2022

JGR Solid Earth

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Critical processes including seismic faulting, reservoir compartmentalization, and borehole failure involve high‐pressure mechanical behavior and strain localization of sedimentary rocks such as sandstone. Sand is often used as a model material to study the mechanical behavior of poorly lithified sandstone. Recent studies exploring the multi‐scale mechanics of sand have characterized the brittle, low‐pressure regime of behavior; however, limited work has provided insights into the ductile, high‐pressure regime of behavior via in‐situ measurements. Critical features of the ductile regime, including grain breakage, grain micromechanics, and volumetric strain behavior therefore remain under‐explored. Here, we use a new high‐pressure triaxial apparatus with in‐situ x‐ray tomography to provide new insights into deformation banding, grain breakage, and grain micromechanics in Ottawa sand subjected to triaxial compression under confining pressures between 10 and 45 MPa. We observed strain‐hardening at pressures above 15 MPa and strain‐neutral responses at pressures below 15 MPa. Compacting shear bands and grain breakage were observed at all pressures with no significant variation due to grain size, except for minor increases in breakage in less‐rounded sands. Grain breakage emerged at stress levels lower than the assumed yield threshold and more intense breakage was associated with thinner deformation bands. Contact sliding at inter‐grain contacts demonstrated a bifurcation into a bimodal distribution, with intense sliding within deformation bands and reduced but non‐negligible sliding outside of deformation bands, suggesting that off‐band zones remain mechanically active during strain hardening.

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Section: Resultssupporting

confidence: 85%

Micromechanics and Strain Localization in Sand in the Ductile Regime

Shahin

Hurley

2022

JGR Solid Earth

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“…Combined with our results, the instability of a granite fault at lower effective stresses may be accompanied by an increase in reservoir permeability during EGS development. Our effective pressure‐induced transition of frictional stability to instability on granite fault gouge is also similar to the reported brittle‐ductile transition (BDT) in porous rocks (Baud et al., 2021; Wong & Baud, 2012). At lower effective confining stresses, brittle faulting is generally observed with dilatant deformation accompanied by shear localization.…”

Section: Discussionsupporting

confidence: 88%

Competing Controls of Effective Stress Variation and Chloritization on Friction and Stability of Faults in Granite: Implications for Seismicity Triggered by Fluid Injection

Zhang

Huang

et al. 2022

JGR Solid Earth

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“…Since this is similar to the observed post-deformation microstructures in Volterra gypsum (Brantut et al, 2011), we can speculate that this was also the case in that rock. This macroscopic volume increase does not however rule out the possibility that local compaction occurred in some parts of our samples, particularly at high effective pressures, as it has recently been shown in carbonates using X-ray computed tomography and digital volume correlation by Baud et al (2021).…”

Section: Impact Of Effective Pressurementioning

confidence: 54%