1. Assistant Professor, Dept. of Civil, Geologic and Mining Engineering, Polytechnique Montreal, 2900 Edouard-Montpetit, Montreal, QC, Canada H3T 1J4 (corresponding author).
2. Lecturer, Dept. of Engineering, Univ. of Exeter, Prince of Wales Rd., Exeter, Devon EX4 4SB, U.K.