Prediction of Resilient Modulus of Compacted Cohesive Soils in South China

The resilient modulus has been used to characterize the stress–strain nonlinear behavior of subgrade soils and is the primary property needed for pavement design and analysis. The degrees of stress and moisture content have a significant impact on the resilient modulus of compacted cohesive soils. Due to the hot, humid climate in South China, the moisture content in embankments will increase gradually from the optimum moisture content (OMC)—the design water content for embankments—to the equilibrium moisture content, which relates to soil properties and the surrounding climate. In this process, the resilient modulus of embankments will obviously decrease. In order to predict the resilient modulus of typical compacted cohesive soils in South China, repeated 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 Van Genuchten model with a relatively high coefficient of determination. Then, the effect of the moisture content, degree of compaction, and stress state including the deviator stress, confining pressure, and octahedral shear stress to the resilient modulus were analyzed. In addition, a logarithmic function was utilized to build the relationship between the matric suction and resilient modulus. Subsequently, a new resilient modulus estimation model of compacted soils in South China, which took the bulk stress, octahedral shear, and matric suction as the model variables, was developed and verified using the data of different cohesive soils from different studies. The results show that the new model matches their data well, and the coefficients of determination are high, which indicates that this new model is reasonable and widely applicable. Finally, the correlations between the physical parameters of soil samples, such as the liquid limit, dry density, the maximum dry density, plasticity index, percentage passing through a 0.075-mm sieve, and the regression coefficients of the new model, were established. The resilient modulus can be predicted much more easily with these physical parameters of compacted cohesive soils rather than conducting triaxial tests.