Resilient Modulus Of A Stabilised Fine-Grained Subgrade Soil

Mechanistic design methods of pavement structures require the use of elastic moduli for each pavement material including subgrades. In the Austroads pavement design guide (Austroads, 1992), elastic characterisation of subgrades and cemented pavement materials is determined from empirical relationships based on California bearing ratio and unconfined compressive strength, respectively, while repeated load triaxial testing yielding resilient modulus is only mentioned as a recommendation for characterising unbound materials. However, in recent years, the resilient modulus of pavement materials has become a more important parameter in pavement analysis and design. This paper presents some of the findings of a continuing research project on engineering properties of a stabilised fine-grained subgrade soil. In particular, the variations in resilient modulus values due to the changes in additive content, dry density, moisture content and curing time were investigated. Laboratory repeated load triaxial tests yielding resilient moduli were conducted on stabilised fine-grained soil samples simulating the material properties at various levels. The resilient modulus results based on various stress levels were then analysed by using deviator stress and octahedral stress models. Resilient modulus values were calculated for an estimated in-situ stress condition using the octahedral stress model. The relationships between the resilient modulus values and each of the parameters mentioned above were defined by single regression analysis. Also, an equation that helps to estimate resilient modulus as a function of additive content, dry density, moisture content and curing time was established.