P-constant condition applied to undrained cyclic triaxial test of unsaturated soils

H. Wang*, J. Koseki, T. Sato

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


To evaluate the liquefaction resistance of unsaturated soils by a triaxial system, it is suggested to keep a p-constant condition rather than the rh-constant condition (i.e., cell pressure constant) that is normally applied to the same test for saturated specimen. The main concern is that the pore pressure coefficient (B value) of unsaturated specimens may be far less than unity, which causes undesired effects on the behaviors of unsaturated soils. A modified triaxial system that can maintain the p-constant condition has been recently developed. By using the system, the behaviors of an unsaturated soil subjected to undrained cyclic triaxial loading are compared between the p-constant condition and the rh-constant condition, which implies that the testing conditions affect behaviors of pore pressures generation, stress strain relationship, etc. Results suggest that tests under the rh-constant condition underestimate the liquefaction resistance of soils. In addition, the modified triaxial system could effectively reduce the variation of p by more than 60 % in the full tested range, or by 75 % in a range with relatively small magnitude of the vertical loading based on test results of three sandy soils.

Original languageEnglish
Pages (from-to)710-718
Number of pages9
JournalGeotechnical Testing Journal
Issue number4
Publication statusPublished - 2017
Externally publishedYes


  • P-constant condition
  • Undrained cyclic triaxial test
  • Unsaturated soil

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology


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