Proceedings of the 15th European Conference on Soil Mechanics and Geotechnical Engineering : geotechnics of hard soils, weak rocks = Comptes Rendus du 15m̈e Congrs̈ Europěn de Mč... by European Conference on Soil Mechanics and Geotechnical Engineering (15th : 2011 : Athina), Anagnostopoulos, Andreas, editor, Pachakis, Michael, editor, Tsatsanifos, Christos, editor