On the strength of transversely isotropic rocks

Yang Zhao, Shabnam J. Semnani, Qing Yin, Ronaldo I. Borja

Research output: Contribution to journalArticlepeer-review


Accurate prediction of strength in rocks with distinct bedding planes requires knowledge of the bedding plane orientation relative to the load direction. Thermal softening adds complexity to the problem since it is known to have significant influence on the strength and strain localization properties of rocks. In this paper, we use a recently proposed thermoplastic constitutive model appropriate for rocks exhibiting transverse isotropy in both the elastic and plastic responses to predict their strength and strain localization properties. Recognizing that laboratory-derived strengths can be influenced by material and geometric inhomogeneities of the rock samples, we consider both stress-point and boundary-value problem simulations of rock strength behavior. Both plane strain and 3D loading conditions are considered. Results of the simulations of the strength of a natural Tournemire shale and a synthetic transversely isotropic rock suggest that the mechanical model can reproduce the general U-shaped variation of rock strength with bedding plane orientation quite well. We show that this variation could depend on many factors, including the stress loading condition (plane strain versus 3D), degree of anisotropy, temperature, shear-induced dilation versus shear-induced compaction, specimen imperfections, and boundary restraints.

Original languageEnglish (US)
Pages (from-to)1917-1934
Number of pages18
JournalInternational Journal for Numerical and Analytical Methods in Geomechanics
Issue number16
StatePublished - Nov 2018
Externally publishedYes


  • anisotropy
  • bifurcation
  • rock strength
  • shear band
  • thermoplasticity
  • transverse isotropy

ASJC Scopus subject areas

  • Computational Mechanics
  • Materials Science(all)
  • Geotechnical Engineering and Engineering Geology
  • Mechanics of Materials


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