A Microstructural Model for Soils and Granular Materials - Multiscale Geomechanics: From Soil to Engineering Projects - page 213

demonstrated that the collapse of an unsaturated specimen could be obtained during
wetting, provided that a sufficiently high stress ratio was applied throughout the
process.
The integration of the capillary forces over all spatial orientations permits us to
define a capillary stress tensor. This tensor is isotropic, i.e. it can be reduced to a
capillary pressure, but only if the particulate structure is itself isotropic. A
generalized effective stress tensor can, therefore, be determined by adding the total
stress and the capillary stress tensors. Numerical simulations demonstrate that the
maximum strength criterion, expressed in terms of generalized effective stresses, is
unique for dry, partially and fully saturated samples.
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[BIA 02] B IAREZ J., H ICHER P.Y., “Mechanisms of soil deformation”, in: H ICHER P.-Y. and
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