Figure 1:   (a) Compaction data from room-temperature experiments shown against effective mean stress. The hydrostatic compaction curve is shown for reference. Triaxial data are shown as a function of effective pressure for each experiment (denoted by the numbers by each curve). Similar results were obtained from experiments at 150^oC.
                (b) Yield data presented in terms of differential stress and effective mean stress. Triaxial deformation at low effective pressures defines a quasi-linear yielding trend consistent with brittle Mohr-Coulomb failure. Deformation at higher effective pressures defines an elliptical failure curve that departs from the lower pressure linear trend.