1. Structural Engineer, Tunneling and Underground Structures Dept., AECOM Technology Corporation, 20 Exchange Place, 13th Floor, New York, NY 10005.
2. Professor, Dept. of Civil, Environmental, and Sustainable Engineering, School of Sustainable Engineering and the Built Environment, Arizona State Univ., Tempe, AZ 85287 (corresponding author).
3. Professor, Dept. of Mechanical Engineering and Technology, College of Engineering and Technology, Wentworth Institute of Technology, Boston, MA 02115.