4.3.2.4 Prediction Equations for E It was concluded from the
sensitivity analysis that the subgrade modulus, E4, could be uniquely
related to the furthest NDT sensor deflection. Therefore, deflections
at the modified sensor 10 position, Do1, which were generated from the
BISAR simulation run, were regressed to their corresponding E4 values.
Two equations were essentially obtained from the regression analysis
(39).
Case 1. For 0.35 < Eq < 200.0 ksi,
"1.0299
E = 5.198 (D ) Eqn. 4.16
4 10
(N = 266, R2 = 0.984)
Case 2. For 10.0 < E < 50.0 ksi,
"0.9745
E = 5.851(D ) Eqn. 4.17
4 10
(N = 193, R2 = 0.9924)
Figure 4.20 compares Equations 4.16 and 4.17 for E4 values ranging
from 0.1 to 200 ksi. Also shown in Figure 4.20 is a simplified equation
which was originally developed from analysis of Dynaflect tests on pave-
ment sections in Quebec, Canada, and Florida (55). It is seen from the
figure that within the E4 range of 10 to 100 ksi, the three equations
are practically the same. Thus, unless the subgrade modulus is