1. Postdoctoral Research Fellow, Nottingham Centre for Geomechanics, School of Civil Engineering, The Univ. of Nottingham, University Park, Nottingham, NG7 2RD U.K. (corresponding author)..
2. Professor, Dept. of Civil Engineering, Univ. Laval, Ste-Foy PQ, Canada G1K 7P4.