Slope stability analyses in stiff fissured clays

Timothy D Stark, Hisham T. Eid

Research output: Contribution to journalArticlepeer-review


Results of torsional ring shear, direct shear, and triaxial compression tests on cohesive soils reveal that the fully softened shear strength is stress-dependent and related to the type of clay mineral and quantity of clay-size particles. An empirical relationship for the fully softened friction angle is presented that is a function of liquid limit, clay-size fraction, and effective normal stress. Studies of first-time slides, i.e., slopes that have not undergone previous sliding, in stiff fissured clay with a liquid limit between 41 and 130% suggest that the mobilized shear strength along the failure surface can be lower than the fully softened shear strength. Recommendations are presented for estimating the mobilized shear strength in first-time slides based on soil plasticity. Soils with a liquid limit greater than 30% exhibit a large difference between the fully softened and residual friction angles. In these soils, the presence or absence of a pre-existing shear surface should be clarified.

Original languageEnglish (US)
Pages (from-to)335-343
Number of pages9
JournalJournal of Geotechnical Engineering
Issue number4
StatePublished - Apr 1997

ASJC Scopus subject areas

  • Environmental Science(all)
  • Geotechnical Engineering and Engineering Geology

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