Modeling Resilient Modulus Hysteretic Behavior with Moisture Variation

The changes in subgrade moisture conditions play an important role in the in-service performance of a pavement. These conditions are sensitive to environmental conditions, such as a rise in the water table, precipitation, freeze-thaw cycles, and wet-dry cycles, among others. Several studies have been conducted to develop relationships between the mechanical properties, namely, the resilient modulus (M-R) of subgrade soils and moisture conditions. No studies, to the authors' knowledge, have directly addressed the hysteretic behavior of M-R with moisture conditions. This study evaluates the effect of moisture hysteresis on M-R values of a subgrade soil following two different paths: (1) drying-wetting-drying path and (2) wetting-drying path. Initially, cylindrical specimens were prepared at approximately optimum moisture content and maximum dry unit weight. The moisture content in each compacted specimen was altered to achieve the target moisture content. Specimens were then tested for M-R values. The laboratory results revealed that the relationships between M-R and the moisture content exhibit a hysteretic behavior similar to the soil-water characteristic curve; specimens subjected to drying exhibited higher M-R values than specimens subjected to wetting. M-R values on the drying-wetting-drying path are different than the corresponding values on the wetting-drying path. Finally, an experimental-empirical approach is proposed to predict the hysteretic behavior of M-R with moisture content. The study demonstrated that the model was capable of predicting the M-R hysteretic behavior, which would be helpful in predicting the response of pavements under seasonal conditions. (C) 2012 American Society of Civil Engineers.