1. Associate Professor, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 500 West 120th St., New York, NY 10027.
2. Director, Geotechnical Laboratory, National Research Institute of Agricultural Engineering, 2-1-2 Kannodai, Tsukuba, Japan.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Delaware, Newark, DE 19716.
4. Graduate Student, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 500 West 120th St., New York, NY 10027.
5. Research Engineer, Geotechnical Laboratory, National Research Institute of Agricultural Engineering, 2-1-2 Kannodai, Tsukuba, Japan.