For circular opening in ground, E/(1-v)R relationship is well known. Then there is a lower bound limit to its use for increasing radius of opening. For example, 5m or 7m, etc. The Vesic equation for modulus of subgrade reaction for flat elastic footing should be quite compatible to the above mentioned lower limit of E/R. Has anyone ever make a comparison between Vesic's equation and the lower limit (highest radius) of E/(1+v)R. My experience with these two formulae however says that the Vesic seems to have much higher value than the lower limit of E/(1+v)R
For case of horse shoe opening, the flat invert is the typical place where one may want to choose between the two equation. It has significant influence to the bearing capacity at the invert.
Any people have any suggestion to their use in underground structures?