Predicting resilient modulus of fine-grained subgrade soils considering relative compaction and matric suction

The resilient modulus has been used to characterise the stress-strain non-linear behaviour of subgrade soils and is an important parameter for pavement design and analysis. This study aims at developing an accurate and efficient methodology to estimate the resilient modulus of subgrade soils. Therefore, repeated load triaxial tests were carried out in this study. The soil matric suction was measured by the pressure plate test and the soil-water characteristic curve (SWCC) was described using the Fredlund & Xing model. Then, the influence of stress state, matric suction and relative compaction on the resilient modulus were analysed. Subsequently, a new resilient modulus model was proposed to incorporate the relative compaction and matric suction in addition to the stress state. The new model matched 7 sets of experimental data well and the coefficients of determination were high, which indicates that this new model is reasonable and widely applicable. Finally, the correlations between the basic properties variables of soil samples and the regression coefficients of the new model were established.