determining preconsolidation pressure from e vs sigma graph

[ketanco]

When we have the e (void ratio) vs stress data from a consolidation test, other than plotting on a chart graphically and solving by graphical methods, or by calculating slopes at individual intervals and looking at where the knee of the curve happens, is there a formula to determine the preconsolidation pressure?

 

[Lomarandil]

No geotech here, but I'm not aware of any other method.