Evaluation on deformation behavior of subgrade clay under freeze-thaw cycles: Laboratory tests and evolution model

The deformation behavior of subgrade soil is crucial to the design of subgrade structures and to maintaining the long-term performance of pavements. Resilient modulus (MR) and permanent deformation (PD) are important indices to characterize elastic deformation and plastic deformation of subgrade soils, respectively. This study aims to investigate the evaluation of deformation behavior (MR and PD) of subgrade clay under deviatoric stress, confining pressure, moisture content, loading cycles, and freeze-thaw (FT) cycles by repeated triaxial load test. An evolution model for calculating PD was proposed based on experimental data. The results showed that the influence of FT cycles on MR and PD was obvious. The largest damage and stable trend were in the first and sixth FT cycles, respectively. MR decreases and PD increases rapidly during the first 2000 loading cycles. The PD evolution model consisting of deviator stress, confining pressure, moisture content, loading cycles and FT cycles of explicit modification functions was proposed and validated. The results obtained in this study contribute to a better understanding of the deformation behavior of subgrade clay under FT cycles.