A Mechanistic-Empirical Model To Predict Suction Profile In Subgrade Soil

The moisture condition in the pavement subgrade is critical because it directly affects the strength and stiffness of the pavement structure. Subgrade soils are usually unsaturated, and the resilient modulus of the subgrade soil is highly dependent on the degree of saturation and the corresponding matric suction. Past studies showed that the equilibrium suction has a direct influence on the strength and stiffness of pavement systems. Hence, an accurate estimation of equilibrium suction underneath pavement structures is critical for determining the long-term resilient modulus of subgrade soil, which is further used to predict pavement performance. In this study, a mechanical-empirical model was developed based on the Mitchell 1980 model to predict suction variation within subgrade soil. The proposed suction variation model predicts the suction distribution throughout the soil subgrade by solving the diffusion equation and incorporates the measured suction from the Oklahoma Mesonet weather stations to estimate the diffusion coefficient. The research study resulted in a practical and implementable tool for pavement engineers in predicting site-specific moisture variations underneath the pavement within the moisture active zone in response to wetting and drying weather cycles. The proposed model was tested, and the results were compared with the predicted values from the well-established climatic model in the literature.