1. School of Transportation, Southeast University, Nanjing, P. R. China; also Department of Civil Engineering, University of Tokyo, Tokyo, Japan.
2. Department of Geological Engineering, Nanjing Tech University, Nanjing, P. R. China; also Nanjing Geotechnical Engineering Institute, Nanjing, P. R. China.
3. Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, P. R. China.
4. Department of Civil Engineering, University of Tokyo, Tokyo, Japan