The shear strength of unsaturated soils

TLDR

Shear strength of unsaturated soils is expressed by two independent stress state variables, with two forms of the equation illustrating the roles of total stress and pore‑water pressure, though published data are limited. The authors outline a laboratory procedure to evaluate the relevant shear strength parameters from test results. Data confirm that shear strength can be represented by a planar surface as proposed by the two equations.

Abstract

The shear strength of an unsaturated soil is written in terms of two independent stress state variables. One form of the shear strength equation is[Formula: see text]The transition from a saturated soil to an unsaturated soil is readily visible. A second form of the shear strength equation is[Formula: see text]Here the independent roles of changes in total stress σ and changes in pore-water pressure u w are easily visualized.Published research literature provides limited data. However, the data substantiate that the shear strength can be described by a planar surface of the forms proposed. A procedure is also outlined to evaluate the pertinent shear strength parameters from laboratory test results.