Modulus of Subgrade Reaction. The plate load test can also be used to calculate the modulus of
subgrade reaction, also known as the subgrade modulus Kv
. The procedure (per NAVFAC DM-7.1,
1982) is to plot the stress exerted by the plate versus the penetration of the plate. Using this plot, the
yield point at which the penetration rapidly increases is estimated. Then the stress qand depth of
penetration of the plate (d) corresponding to half the yield point are determined from the plot and
the subgrade modulus Kv
is defined as: