1. Doctoral Student, Civil and Environmental Engineering, Univ. of Missouri, Columbia, MO 65211-2200.
2. Associate Professor, Civil and Environmental Engineering, Univ. of Missouri, Columbia, MO 65211-2200 (corresponding author).
3. Associate Professor, Dept. of Mining Engineering, Univ. of Kentucky, Lexington, KY 40506-0107.
4. Professor, Civil and Environmental Engineering, Univ. of Missouri, Columbia, MO 65211-2200.