1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, The Pennsylvania State Univ., University Park, PA 16802.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, The Pennsylvania State Univ., University Park, PA 16802 (corresponding author).
3. Professor, State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu Univ. of Technology, Chengdu 610059, P.R. China.