log E3 =
4.970 + 0.1773(t1) 1.6966 log(t ) 0.1069(D4)
+ 0.2552(D7) 2.6546 log(D1) 3.9906 log(D3)
+ 1.8241 log(D ) + 3.5092 log(D2 D5)
Eqn. 6.13
R2 = 0.887 and N = 22
Error analysis indicated that one pavement (SR 15B) had -34.6
percent prediction error. The actual E value was 50.0 ksi, while
the predicted value was 32.7 ksi. Others had prediction errors
generally less than 15 percent.
Equation 6.13 for the prediction of E3 applies to a slightly
wider range of variables than Equation 4.24 which was selected from
the theoretical analysis. However, the latter is more simplified
and contains fewer variables than Equation 6.13. Also, since the
R2 value is greater, Equation 4.24 should be used for E3 predic-
tions.
6.7.3.2.4 Subgrade modulus, E4. Regression
against either D or D or both resulted in the
tions:
E = 53.697(D )-1.041
4 6
(R2 = 0.997 and N = 22)
E = 39.690(D )1.004
4
(R2 = 0.999 and N = 22)
analyses of E4
following equa-
Eqn. 6.14
Eqn. 6.15