1. Postdoctoral Researcher, Institute of Transportation Engineering, College of Civil Engineering and Architecture, Zhejiang Univ., Hangzhou 310027, P.R. China.
2. Professor, MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang Univ., Hangzhou 310027, P.R. China (corresponding author).
3. Professor, Dept. of Civil, Environmental and Architecture Engineering, Univ. of Kansas, Lawrence, KS 66045.