A Yield Strength Model for Partially Saturated Unbound Granular Material

ABSTRACT The predominant mode of distress for unbound pavement layers is the permanent deformation of the layer either through gradual deformation or rapid shear failure. Both these forms of permanent deformation have been linked to the shear strength of the material by researchers. Conventionally, the shear strength of the material is characterised with the Mohr-Coulomb shear strength parameters of the material. This paper presents an alternative model to describe the yield strength of the material incorporating the effects of density and degree of saturation. The model includes the influence of the suction pressure resulting from matric suction in partially saturated material on the yield strength and has been calibrated with a high degree of accuracy using conventional tri-axial test results for a number of road-building materials ranging from fine sand to crushed stone.