[1] Univ British Columbia, Dept Civil Engn, Vancouver, BC V6T 1Z4, Canada
[2] Univ Calif Davis, Dept Civil & Environm Engn, Davis, CA 95616 USA
[3] Natl Tech Univ Athens, Dept Mech, Zografos 15780, Greece
[4] Norwegian Geotech Inst, N-0806 Oslo, Norway
[5] Earth Mech Inc, Oakland, CA 94621 USA