2ND CANADIAN GEOTECHNICAL COLLOQUIUM - APPROPRIATE CONCEPTS AND TECHNOLOGY FOR UNSATURATED SOILS

This paper presents concepts that can be used to develop an appropriate engineering practice for unsaturated soils. The nature of an unsaturated soil is first described along with the accompanying stress conditions. The basic equations related to mechanical properties are then proposed. These are applied to practical problems such as earth pressure, limiting equilibrium, and volume change. An attempt is made to demonstrate the manner in which saturated soil mechanics must be extended when a soil is unsaturated. The complete volumetric deformation of an unsaturated soil requires two three-diemnsional constitutive surfaces. These converge to one two-dimensional relationship for a saturated soil. The shear strength for an unsaturated soil is a three-dimensional surface that reduces to the conventional Mohr-Coulomb envelope for a saturated soil. The manner of applying the volumetric deformation equations and the shear strnegth equation to practical problems is demonstrated. Refs.