Unsaturated mechanical behaviour of a granular material

Abstract

This paper presents the influence of the unsaturated state and especially the suction on the permanent and resilient behaviour of a granular material for roads. In this context, the soil water retention curves (SWRCs) of a compacted clayey sand with two different fine contents are initially obtained to deduce the suction corresponding to a given water content. A parameter s* is defined as the suction value corresponding to the intersection point of wetting and drying paths in the SWRC. The permanent deformation and resilient deformation under repeated loading with different water contents and different fine contents are then studied by repeated load triaxial tests. Based on the experimental results, it can be stated that the hydraulic conditions affect strongly both permanent and resilient deformations of the granular materials. Finally, a series of equations can be proposed to describe the correlations between suction ratio s/s* and permanent and resilient deformations of the granular material at different water contents and different fine contents. Generally, the prediction models can effectively capture the permanent and resilient behaviours based on the suction ratio s/s*. The analytical solutions are unique to estimate permanent and resilient behaviour in the same framework based on the suction value. We recommend the models as improved approaches to reduce the number of tests required to estimate the soil deformation in pavement structures.