The steady state is exactly representing the critical void ratio under CSSM interpretation.
Year Researchers Developments 1940 Casagrande  Introduced critical void ratio, the same void ratio where contracted loose soil and dilated dense soil approach after sheared to large strains 1956 Taylor  Showed experimentally that dilatancy is stress dependent 1958 Roscoe et al.
The pressure-dependent critical void ratio [e.sub.cs] is expressed as
where [lambda] is the slope of the critical state line in the e - ln p' plane, [e.sup.[GAMMA]] corresponds to the critical void ratio for ln p' = 0, and p' is the mean effective pressure.
The critical void ratio of soil might be negative when the mean effective pressure p' in Equation (3) increases to a certain value, which is obviously unreasonable.