1. Assistant Professor, Dept. of Technology, Illinois State Univ., Normal, IL 61790 (corresponding author).
2. David Ross Boyd Professor and Aaron Alexander Professor of Civil Engineering, Professor of Petroleum and Geological Engineering, and Associate Dean for Research and Graduate Programs, College of Engineering, Univ. of Oklahoma, Norman, OK 73019.
3. Geotechnical Engineer Intern, Burgess Engineering & Testing, Inc., 809 NW 34th St., Moore, OK 73160; formerly, Graduate Research Assistant, School of Civil Engineering and Environmental Science, Univ. of Oklahoma, Norman, OK 73019.
4. Assistant Professor of Civil Engineering, Arkansas State Univ., Jonesboro, AR 72467; formerly, Research Associate, School of Civil Engineering and Environmental Science, Univ. of Oklahoma, Norman, OK 73019.