Failure characteristics of two porous sandstones subjected to true triaxial stresses: Applied through a novel loading path

Xiaodong Ma*, John W. Rudnicki, Bezalel C. Haimson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


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 languageEnglish (US)
Pages (from-to)2525-2540
Number of pages16
JournalJournal of Geophysical Research: Solid Earth
Issue number4
StatePublished - Apr 1 2017
Externally publishedYes


  • Lode angle
  • bifurcation theory
  • failure characteristics
  • failure plane angle
  • porous sandstones
  • true triaxial testing

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)


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