263
Correlation of the base course modulus (E2) from the Dynaflect and
FWD for the various test sections resulted to the following equation:
E2 (Dynaflect) = 1.380 E2 (FWD) Eqn. 6.4
(R2 = 0.871, N = 17)
Table 6.20 shows that the ratio of the subbase modulus from the
Dynaflect to the FWD ranges from 1.01 to 3.75, except for SR 15C M.P.
0.055 in which a ratio of 6.25 was obtained. This value was considered
to be an outlier (though both deflection basins tuned well) in subse
quent analysis. The trend for the subbase is similar to that of the
base course. Therefore, the same conclusions, with regard to the effect
of the type of NDT device on granular base course materials, applies to
the subbase layer. Regression analysis of Dynaflect and FWD data in
Table 6.18 resulted in the following equation:
E3 (Dynaflect) = 1.488 E$ (FWD) Eqn. 6.5
(R2 = 0.930, N = 16)
It is interesting to note that not only does the R2 value increase, but
also the regression coefficient increased in Equation 6.5 compared to
Equation 6.4. Thus, higher ratios (see Table 6.20) were obtained for
the subbase than the base course.
The comparison between Dynaflect and FWD predictions of the sub
grade modulus (E^) is presented in Tables 6.19 and 6.20. The ratio