A volumetric yield surface for compacted soils based on constant water content testing

¹ PhD candidate, Department of Civil Engineering, Monash University, Melbourne, Australia
² Professor, Department of Civil Engineering, Monash University, Melbourne, Australia
³ Senior Lecturer, Department of Civil Engineering, RMIT University, Melbourne, Australia

^* Corresponding author: Chathurika.jayasundara@monash.edu

Abstract

Unsaturated soils exhibit various complex behaviours compared to saturated soils, such as collapse upon wetting. Therefore, understanding the response of unsaturated soils under general field conditions is essential for the design and construction of safe and economical geotechnical engineering structures. This research is based on the Monash-Peradeniya-Kodikara (MPK) framework proposed by Kodikara [1] for unsaturated compacted soils, which provides a direct link to the traditional compaction loaded curves and constant water content loading experiments. Kodikara [1] named the loaded compaction surface the loading wetting state boundary surface (LWSBS) and validated the model for a combination of loading and wetting stress paths. However, the experimental validation of the yield surface after drying stress paths was not addressed in the original paper. This paper reports the results of drying stress path tests carried out within the specific volume (v),specific moisture ratio (v_w) and mean net stress (p) space of the MPK model, and observations suggest that the yield surface is unique after drying stress paths. Mathematical equations for the volumetric behaviour of unsaturated soils are derived using the constant degree of saturation hyperlines derived from constant water content testing, as this enables direct coupling with the soil water retention curve. Finally, the volumetric equations are validated based on the available experimental data.