1. Associate Professor of Geotechnical Engineering, School of Civil Engineering, National Engineering Laboratory for High-Speed Railway Construction, Central South Univ., 22 South Shaoshan Rd., Changsha, Hunan 410075, China (corresponding author).
2. Professor of Geotechnical Engineering, School of Civil Engineering, Key Laboratory of Heavy-Haul Railway Engineering Structures, Central South Univ., 22 South Shaoshan Rd., Changsha, Hunan 410075, China.