1. Postdoctoral Researcher, Laboratory of Soil Mechanics, Swiss Federal Institute of Technology in Lausanne, École Polytechnique Fédérale de Lausanne, Station 18, CH 1015 Lausanne, Switzerland (corresponding author).
2. Research Assistant Professor, Charles E. Via, Jr. Dept. of Civil and Environmental Engineering, Virginia Tech, 750 Drillfield Dr., 200 Patton Hall, Blacksburg, VA 24061; presently, Dept. of Civil, Architectural and Environmental Engineering, Missouri Univ. of Science and Technology, 127 Butler-Carlton Hall, Rolla, MO 65409.
3. Professor, Laboratory of Soil Mechanics, Swiss Federal Institute of Technology in Lausanne, École Polytechnique Fédérale de Lausanne, Station 18, CH 1015 Lausanne, Switzerland.