1. Tunnel/Geotechnical Engineer, HNTB, 31 St. James Ave., Ste. 300, Boston, MA 02116.
2. Professor, North Carolina State Univ., Raleigh, NC 27695-7908 (corresponding author).
3. Senior Engineer, GRL Engineers, Inc., 30725 Aurora Rd., Cleveland, OH 44139.
4. Professor, North Carolina State Univ., Raleigh, NC 27695-7908.