1. U. S. Army Engineer Research and Development Center, Geotechnical and Structures Laboratory, Building 5014, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180-6199, USA
2. Southern Methodist University, Roy M. Huffington Department of Earth Sciences, P.O. Box 750395, Dallas, Texas 75275-0395, USA
3. U. S. Army Engineer Research and Development Center, Information Technology Laboratory, Building 8000, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180-6199, USA