1. Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing, P. R. China.
2. School of Civil Engineering, Beijing Jiaotong University, Beijing, P. R. China.
3. Tianjin Municipal Engineering Design & Research Institute Co., Ltd., Tianjin, P. R. China.
4. Discipline of Civil and Infrastructure Engineering, School of Engineering, Royal Melbourne Institute of Technology, Melbourne, Vic, Australia.