1. Research Assistant, Railway Engineering Research Institute, China Academy of Railway Sciences Corporation Limited, No. 2, Daliushu Rd., Haidian District, Beijing City 100081, China.
2. Professor, Faculty of Land Resources Engineering, Kunming Univ. of Science and Technology, No. 68, Wenchang Rd., 121 Avenue, Yunnan Province, Kunming City 650093, China; Research Scholar, School of Civil and Environment Engineering, Univ. of Science and Technology Beijing, No. 30, Xueyuan Rd., Haidian District, Beijing City 100083, China (corresponding author).
3. Professor, School of Civil and Environment Engineering, Univ. of Science and Technology Beijing, No. 30, Xueyuan Rd., Haidian District, Beijing City 100083, China.