273
t 3/TE + t 3 /T
12 =[ 2 2 ]3 Eqn. 6.9
1 2
Figures 6.70 and 6.71 present the relationships between E12 and
Di D4 for each of the weighting methods. There is very little
difference between modulus-deflection relationship for the standard
weighting method (Equation 6.8) and the Thenn de Barros' formula
(Equation 6.9), as shown in Figure 6.70 and Figure 6.71, respectively.
It would appear that either method would be suitable for defining E1
although the difference between methods becomes significant at low E1
values and high D1 D4 values (e.g., E12 < 34.0 ksi, and D D > 1.0
mil). Thus knowing E12 from D D and E1 from asphalt rheology (or
using Figure 6.64), E2 can be calculated using Equations 6.8 and 6.9. A
procedure incorporating the above and other layer moduli predictions for
routine pavement evaluation studies is presented in Appendix F.
The relationship between E and D0 D, is illustrated in Figure
6.72. The figure shows that the simplified format of Equation 4.15
could be used for a wider range of E values. Even though the results
of the regression analysis of Figure 6.72 is fairly good, the range in
E3 values is still narrow and limited to only two values below 20.0
ksi. Additional test data in the lower range would be helpful in either
verifying the validity of the E3 prediction equation or modifying the
regression equation.
Subgrade modulus prediction equations and the modified Dynaflect
sensor 10 deflection values are shown in Figure 6.73. The simplified
equation (Equation 4.35), as previously explained, was originally
developed using data collected in Quebec, Canada and Florida. Figure