Microplane damage model for jointed rock masses

Xin Chen*, Zdeněk P. Bažant

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The paper presents a new microplane constitutive model for the inelastic behavior of jointed rock masses that takes into account the mechanical behavior and geometric characteristics of cracks and joints. The basic idea is that the microplane modeling of rock masses under general triaxial loading, including compression, requires the isotropic rock matrix and the joints to be considered as two distinct phases coupled in parallel. A joint continuity factor is defined as a microplane damage variable to represent the stress-carrying area fraction of the joint phase. Based on the assumption of parallel coupling between the rock joint and the rock matrix, the overall mechanical behavior of the rock is characterized by microplane constitutive laws for the rock matrix and for the rock joints, along with an evolution law for the microplane joint continuity factor. The inelastic response of the rock matrix and the rock joints is controlled on the microplane level by the stress-strain boundaries. Based on the arguments enunciated in developing the new microplane model M7 for concrete, the previously used volumetric-deviatoric splits of the elastic strains and of the tensile boundary are avoided. The boundaries are tensile normal, compressive normal, and shear. The numerical simulations demonstrate satisfactory fits of published triaxial test data on sandstone and on jointed plaster mortar, including quintessential features such as the strain softening and dilatancy under low confining pressure, as well as the brittle-ductile transition under higher confining pressure, and the decrease of jointed rock strength and Young's modulus with an increasing dip angle of the joint.

Original languageEnglish (US)
Pages (from-to)1431-1452
Number of pages22
JournalInternational Journal for Numerical and Analytical Methods in Geomechanics
Issue number14
StatePublished - Oct 10 2014


  • Constitutive model
  • Damage mechanics
  • Failure
  • Geomaterials
  • Inelastic behavior
  • Joint
  • Microplane model
  • Rock

ASJC Scopus subject areas

  • Computational Mechanics
  • General Materials Science
  • Geotechnical Engineering and Engineering Geology
  • Mechanics of Materials


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