Summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests

This paper summarizes experimental studies on wetting-induced collapsibility in loess using single-oedometer, double-oedometer, and triaxial wetting tests. Artificially structural loess samples with interparticle bonding calcite (CaCO3) and a large void ratio were tested in the laboratory to avoid sampling disturbance of natural loess. The comparison between the single- and double-oedometer tests confirms that the wetting-induced deformation is independent of the sequence of wetting and loading. The conventional triaxial apparatus was enhanced for investigating the collapse deformation in response to different water content increments when subjected to different stress levels. The wetting-induced strain subjected to high confining pressure develops in two steps. It increases with increasing water content and reaches a relatively stable plateau, and then increases rapidly again until a final stable state is reached. The initial collapse surface was found by plotting the wetting-induced strain vectors observed in triaxial wetting tests. The wetting-induced strain is negligible when a specimen is wetted at a stress point inside this surface, while it becomes significant when wetted beyond this surface.