Prediction of resilient modulus of unsaturated soils considering inter-particle suction bonding

Understanding the behaviour of compacted soils in road and railroad formations is crucial for ensuring the long-term performance of transportation infrastructure. These formations are often under unsaturated conditions and their response to repeated traffic-induced loads is significantly influenced by soil water content and suction (i.e., water retention), which vary due to environmental factors such as precipitation and evaporation. This paper proposes a predictive framework to establish a relationship between the mechanical cyclic response and water retention properties of unsaturated compacted soils. The proposed framework employs two constitutive variables, i.e. Bishop's stress and an inter-particle bonding parameter, and is intended to predict the resilient modulus of unsaturated compacted soils subjected to repeated traffic and environmental loading. Both constitutive variables allow consideration of the effects of the degree of saturation and suction on the compacted soil behaviour and facilitate a smooth transition between unsaturated and saturated states. The proposed model is used to predict the resilient modulus of various unsaturated soils subjected to cyclic loading. The results show a good agreement between the predictions of the model and experimental data.