A constitutive model based on modified mixture theory for unsaturated rocks

Xiaohui Chen, Michael A. Hicks

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Non-equilibrium thermodynamics and Biot poro-elasticity have been combined to give a coupled hydro-mechanical formulation for unsaturated rock. Darcy’s law for unsaturated flow has been derived from the dissipation process by using standard arguments of non-equilibrium thermodynamics, whereas Helmholtz free energy has been used to derive the relationship between stress and pore pressure changes. The resulting general framework accommodates both large and small deformation theories. When small deformations are assumed, the formulation is comparable with coupled equations derived using an alternative approach. For illustrative purposes, the formulation has been used to analyse a seasonally affected tunnel model. Numerical results for the desaturation in winter and resaturation in summer, of the zone near the tunnel wall, have been evaluated and compared with the findings of other researchers.
Original languageEnglish
Pages (from-to)925-933
Number of pages9
JournalComputers and Geotechnics
Issue number8
Publication statusPublished - Dec 2011
Externally publishedYes


  • Biot’s theory
  • Mixture theory
  • Non-equilibrium thermodynamics
  • Unsaturated rocks


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