1. Assistant Project Engineer, Paul C. Rizzo Associates, Inc., Monroeville, PA 15146.
2. Professor, Geological Engineering Program, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin, Madison, WI 53706.
3. Wisconsin Distinguished Professor and Chairman, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin, Madison, WI 53706.
4. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, 1163 Glenn Martin Hall, College Park, MD 20742 (corresponding author).