Oedometer Test for Undaturated Soils

[WestTennesseeLoess]

Does anyone have any experience or knowledge of unsaturated oedometer tests? Specifically, soil specimens that have been compacted to the same preconsolidation pressure, but are compacted at different dry densities and moisture contents. I have not been able to find any papers pertaining to this type of research. Should the virgin curves (i.e. normal consolidation lines) be parallel to each other or at a given overburden pressure should these curves begin to merge. Any information would be greatly appreciated!