A Microstructural Model for Soils and Granular Materials - Multiscale Geomechanics: From Soil to Engineering Projects - page 200

from the Adour Valley. The Atterberg's limits are wl = 75% and wp = 25%. The
undrained test results on samples around 13.5 m deep are presented in Figure 7.14
[FAY 00]. The maximum strength envelope in the p ', q plane shows a macroscopic
cohesion of the clay around 10 kPa.

Figure 7.14. Triaxial tests on Guiche clay [FAY 00, KHE 92]

The model parameters were determined from a series of drained and undrained
triaxial tests, as well as from the physical characteristics of the material. They are
summarized in Table 7.4. In order to account for macroscopic cohesion, the contact
law was modified by introducing an additional adhesive force perpendicular to the
contact plane, which plays the role of the intergranular glue, as discussed above. In
this example, the glue is ductile and keeps the same value throughout the mechanical
loading. Its value was calibrated in order to obtain the correct value of the measured
macroscopic cohesion: f = 0.022N.

e ref p ref (MPa) λ

φ μ （ ˚ ） φ 0 （ ˚ ） C e

β m e 0

1.80 0.01 0.80 27.00 27.00 0. 10 1.00 0.50 1.62

Table 7.4. Model parameters for Guiche clay

The results of the numerical simulations of three undrained triaxial tests are
presented in Figure 7.15. They demonstrate that the model can reproduce both the
stress−strain relationships and the effective stress paths for three different
consolidation stresses with good accuracy. The maximum strength envelope was