STRESS-STRAIN MODULUS OF CLAY IN UNDRAINED SHEAR

This closure notes that another important aspect of the effect of cyclic loading is the variation in modulus for a given cycle rather than the modulus in terms of total deformation. This effect can be significant in stiff fissured or laminated clays, or both. Data on stiff overconsolidated London clay from a depth of 50 ft to 160 ft (by Ward, Samuels and Butler) showed that the stress-strain modulus for reloading was 1.4 times that for initial loading with block samples and 1.9 to 2.6 times that for initial loading with tube samples. These were unconsolidated -undrained triaxial compression tests with confining pressures of 45 psi to 110 psi; the applied stress difference was 25% to 40% of the undrained compressive strength. This large effect occurred despite the fact that seating errors were taken into account. The authors hypothesized that the stress difference during initial loading closed up open laminations and fissures and that the higher modulus from the reloading cycle better duplicated in situ conditions. C. B. Crawford and K. N. Burn also found that cyclic loading in unconsolidated-undrained triaxial tests yielded values of modulus nearest the estimated field value.

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  • Accession Number: 00095453
  • Record Type: Publication
  • Report/Paper Numbers: Closure
  • Files: TRIS
  • Created Date: May 29 1975 12:00AM