1. Senior Engineer, Sichuan Provincial Transport Dept. of Highway Planning, Survey, Design and Research Institute, Chengdu 610031, China (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Hong Kong Univ. of Science and Technology, Clear Water Bay, Hong Kong.
3. Associate Professor, School of Civil Engineering, Southwest Jiaotong Univ., Chengdu 610031, China.
4. Assistant Engineer, Sichuan Provincial Transport Dept. of Highway Planning, Survey, Design and Research Institute, Chengdu 610031, China.
5. Master Student, School of Civil Engineering, Southwest Jiaotong Univ., Chengdu 610031, China.