1. Lecturer, Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Dept. of Geotechnical Engineering, Tongji Univ., Shanghai 200092, China.
2. Professor, Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Dept. of Geotechnical Engineering, Tongji Univ., Shanghai 200092, China (corresponding author).
3. Professor, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Singapore 117576.