Geotechnical Problems Due To The Collapse Of Unsaturated Soils: The Case Of Loess From Northern France

Some periglacial loess deposits from Northern France are partially saturated thanks to the protection provided by an upper surface layer with higher clay content. When excavated and exposed to climatic changes, the loess deposit may exhibit collapse if their clay fraction is small enough and carbonate content high enough. These conditions allow for the stability of a loose porous microstructure with bonding links that are destroyed by water infiltration. In the paper, the origin and the properties of loess deposits from Northern France are described, together with the laboratory method of characterising collapse. Some practical conclusions are afterwards drawn.