In this chapter, the probabilistic porous-solid model is used to determine the
mean effective stress of soils at failure. The plots of the deviator stress against the
mean effective stress show a unique failure line for a series of triaxial tests performed
at different confining net stress and suctions for both wetting and drying paths. This
result confirms that the proposed effective stress equation is adequate to predict the
shear strength of unsaturated soils. It also results in different strengths for wetting and
drying paths as the experimental evidence indicates.
Keywords: Axis translation technique, Confining stress, Constant volume test,
Critical state, Drying path, Eeffective stress, Friction angle, Grain size
distribution, Logarithmic normal distribution, Net stress, Pore size distribution,
Porous-solid model, Shear strength, Soil-water retention curve, Triaxial tests,
Wetting path.
