Long-term resilient behaviour of thawed saturated silty clay under repeated cyclic loading: experimental evidence and evolution model

In seasonally frozen regions, subgrade soils are not only being subjected to large numbers of repeated cyclic loading at a stress level lower than shear strength, but also suffer from the effect of freeze–thaw cycles, which could make the long-term resilient behaviours of subgrade soils as important as the short-term resilient behaviours determined by standard test procedures. In this study, three series of undrained cyclic tri-axial tests were performed to investigate the evolution of the resilient modulus for thawed saturated silty clay during the long-term repeated cyclic loading. Effects of the freeze–thaw cycles, cyclic stress amplitude, confining pressure and loading frequency were considered. Based on the experimental evidences, it was found that the normalised resilient modulus decreases with an increase in the number of freeze–thaw cycles, cyclic stress amplitude and number of loading cycles, respectively, but increases with an increase in confining pressure and increasing loading frequency. An evolution model, which considers the effects of these five influencing factors together with the values of fitting parameters, was established and validated. The proposed model can be used for predicting the evolution of resilient modulus for thawed saturated subgrade clays under the long-term repeated traffic loading, and assist in evaluating the long-term deformation of pavement in seasonally frozen regions.