1. Graduate Student, Dept. of Civil, Geological, and Mining Engineering, École Polytechnique, P.O. Box 6079, Station CV, Montréal, Québec, Canada, H3C 3A7.
2. Professor, Dept. of Civil, Geological, and Mining Engineering, École Polytechnique, P.O. Box 6079, Station CV, Montréal, Québec, Canada, H3C 3A7 (corresponding author). E-mail: pierre.leger@polymtl.ca