Abstract
We performed an extensive suite of true triaxial experiments in two porous sandstones, Bentheim (porosity ≈ 24%) and Coconino (17%). The experiments were conducted using a novel loading path, which maintains constant Lode angle (Θ) throughout the test. This path enabled the examination of the effects of Lode angle and mean stress on failure (σoct,f). Our tests covered σ3 magnitudes between 0 and 150 MPa and of Θ at −30° (axisymmetric extension), −16°, 0°, +11°, +21°, and +30° (axisymmetric compression). Test results revealed the respective contribution of each of the two stress invariants to failure stress, failure plane angle, and failure mode. In both sandstones, the shear stress required for failure increases with mean stress but decreases with Θ when shear failure mode dominates. However, the dependence of failure stress on mean stress and Θ is reversed when the compactive failure mode is in control. The compactive failure mode was evident in Bentheim sandstone when compaction bands were observed under high mean stress. The Coconino sandstone did not reach the compactive failure regime within the maximum confinement applied. The failure plane angle monotonically decreases with increasing mean stress and Θ. For Coconino sandstone, failure plane angle varies between 80° and 50° for σoct,f between 50 and 450 MPa whereas it drops to 0° as σoct,f, approaches 250 MPa in Bentheim sandstone. We employed the bifurcation theory to relate the stress conditions at failure to the development of failure planes. The theory is in qualitative agreement with the experimental data.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2525-2540 |
| Number of pages | 16 |
| Journal | Journal of Geophysical Research: Solid Earth |
| Volume | 122 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1 2017 |
Fingerprint
Keywords
- Lode angle
- bifurcation theory
- failure characteristics
- failure plane angle
- porous sandstones
- true triaxial testing
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science
Cite this
}
Failure characteristics of two porous sandstones subjected to true triaxial stresses : Applied through a novel loading path. / Ma, Xiaodong; Rudnicki, John W; Haimson, Bezalel C.
In: Journal of Geophysical Research: Solid Earth, Vol. 122, No. 4, 01.04.2017, p. 2525-2540.Research output: Contribution to journal › Article
TY - JOUR
T1 - Failure characteristics of two porous sandstones subjected to true triaxial stresses
T2 - Applied through a novel loading path
AU - Ma, Xiaodong
AU - Rudnicki, John W
AU - Haimson, Bezalel C.
PY - 2017/4/1
Y1 - 2017/4/1
N2 - We performed an extensive suite of true triaxial experiments in two porous sandstones, Bentheim (porosity ≈ 24%) and Coconino (17%). The experiments were conducted using a novel loading path, which maintains constant Lode angle (Θ) throughout the test. This path enabled the examination of the effects of Lode angle and mean stress on failure (σoct,f). Our tests covered σ3 magnitudes between 0 and 150 MPa and of Θ at −30° (axisymmetric extension), −16°, 0°, +11°, +21°, and +30° (axisymmetric compression). Test results revealed the respective contribution of each of the two stress invariants to failure stress, failure plane angle, and failure mode. In both sandstones, the shear stress required for failure increases with mean stress but decreases with Θ when shear failure mode dominates. However, the dependence of failure stress on mean stress and Θ is reversed when the compactive failure mode is in control. The compactive failure mode was evident in Bentheim sandstone when compaction bands were observed under high mean stress. The Coconino sandstone did not reach the compactive failure regime within the maximum confinement applied. The failure plane angle monotonically decreases with increasing mean stress and Θ. For Coconino sandstone, failure plane angle varies between 80° and 50° for σoct,f between 50 and 450 MPa whereas it drops to 0° as σoct,f, approaches 250 MPa in Bentheim sandstone. We employed the bifurcation theory to relate the stress conditions at failure to the development of failure planes. The theory is in qualitative agreement with the experimental data.
AB - We performed an extensive suite of true triaxial experiments in two porous sandstones, Bentheim (porosity ≈ 24%) and Coconino (17%). The experiments were conducted using a novel loading path, which maintains constant Lode angle (Θ) throughout the test. This path enabled the examination of the effects of Lode angle and mean stress on failure (σoct,f). Our tests covered σ3 magnitudes between 0 and 150 MPa and of Θ at −30° (axisymmetric extension), −16°, 0°, +11°, +21°, and +30° (axisymmetric compression). Test results revealed the respective contribution of each of the two stress invariants to failure stress, failure plane angle, and failure mode. In both sandstones, the shear stress required for failure increases with mean stress but decreases with Θ when shear failure mode dominates. However, the dependence of failure stress on mean stress and Θ is reversed when the compactive failure mode is in control. The compactive failure mode was evident in Bentheim sandstone when compaction bands were observed under high mean stress. The Coconino sandstone did not reach the compactive failure regime within the maximum confinement applied. The failure plane angle monotonically decreases with increasing mean stress and Θ. For Coconino sandstone, failure plane angle varies between 80° and 50° for σoct,f between 50 and 450 MPa whereas it drops to 0° as σoct,f, approaches 250 MPa in Bentheim sandstone. We employed the bifurcation theory to relate the stress conditions at failure to the development of failure planes. The theory is in qualitative agreement with the experimental data.
KW - Lode angle
KW - bifurcation theory
KW - failure characteristics
KW - failure plane angle
KW - porous sandstones
KW - true triaxial testing
UR - http://www.scopus.com/inward/record.url?scp=85017527942&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85017527942&partnerID=8YFLogxK
U2 - 10.1002/2016JB013637
DO - 10.1002/2016JB013637
M3 - Article
AN - SCOPUS:85017527942
VL - 122
SP - 2525
EP - 2540
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
SN - 2169-9313
IS - 4
ER -