1. M.Sc. Student, College of Environment and Civil Engineering, Chengdu Univ. of Technology, Chengdu 610059, Sichuan, China.
2. Professor, State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong Univ., Chongqing 400074, China (corresponding author).
3. Ph.D. Candidate, Dept. of Geological Engineering, Southwest Jiaotong Univ., Chengdu 610031, Sichuan, China.
4. State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing Jiaotong Univ., Chongqing 400074, China.
5. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.