1. Laboratory of Mechanics of Lille, UMR 8107, USTL-EPU, Cité Scientifique, 59655 Villeneuve d’Ascq, France.
2. Laboratory of Mechanics of Lille, UMR 8107, USTL-EPU, Cité Scientifique, 59655 Villeneuve d’Ascq, France.
3. Institute of Geotechnics and Hydrotechnics, Wroclaw Univ. of Technology, St. Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland.