An analytical model for predicting the shear strength of unsaturated soils

Tuan A. Pham*, Melis Sutman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
6 Downloads (Pure)


The prediction of shear strength for unsaturated soils remains to be a significant challenge due to their complex multi-phase nature. In this paper, a review of prior experimental studies is firstly carried out to present important pieces of evidence, limitations, and some design considerations. Next, an overview of the existing shear strength equations is summarized with a brief discussion. Then, a micromechanical model with stress equilibrium conditions and multi-phase interaction considerations is presented to provide a new equation for predicting the shear strength of unsaturated soils. The validity of the proposed model is examined for several published shear strength data of different soil types. It is observed that the shear strength predicted by the analytical model is in good agreement with the experimental data, and get high performance compared to the existing models. The evaluation of the outcomes with two criteria, using average relative error and the normalized sum of squared error, proved the effectiveness and validity of the proposed equation. Using the proposed equation, the nonlinear relationship between shear strength, saturation degree, volumetric water content, and matric suction are observed.

Original languageEnglish
JournalProceedings of the Institution of Civil Engineers: Geotechnical Engineering
Publication statusE-pub ahead of print - 5 Jan 2022


  • effective stress
  • experimental comparison
  • micromechanical model
  • Partial saturation
  • shear strength
  • soil suction
  • statistical analysis

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Earth and Planetary Sciences (miscellaneous)


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