1. Professor, Dept. of Geotechnical Engineering, Tongji Univ., 1239 Siping Rd., Shanghai 200092, P. R. China (corresponding author).
2. Engineer, Suzhou Rail Transit Co., Ltd., 668 Ganjiang Rd. West, Suzhou, Jiangsu Province 215006, P. R. China.
3. Ph.D. Candidate, Dept. of Geotechnical Engineering, Tongji Univ., Shanghai 200092, P. R. China.
4. Engineer, Beijing Municipal Construction Design Institute, Shanghai Branch, Shanghai 200092, P. R. China.
5. Dept. of Geotechnical Engineering, Tongji Univ., Shanghai 200092, P. R. China.