covering the range listed in Table 4.1. Typical theoretical FWD

deflection basins are shown in Figures 4.4 through 4.10. Figures 4.12

and 4.13 illustrate typical Dynaflect deflection basins for selected

combinations of moduli and asphalt concrete thickness. The BISAR

predicted deflection values served as a database for the development of

prediction equations which would hopefully provide the capability of

evaluating the structural capacity and deficiencies of in-service

pavements.

 The deflection data generated from different combinations of layer

moduli and thicknesses were evaluated to determine if the deflection

response from one or more geophone positions in the Dynaflect or FWD

could provide a unique relationship for prediction of individual layer

moduli. The sensitivity analysis had indicated the possibility of

uniquely relating the farthest sensor in the Dynaflect or FWD system to

the subgrade modulus. Attempts were therefore made to identify similar

unique positions for the other layer modulus predictions. The lack of

sensitivity of the upper pavement layers with sensor deflections

suggested the difficulty of developing simple prediction equations.

 However, it was found from the modified Dynaflect sensor system

(see Figure 4.2) that the difference between sensor 1 and 4 deflections

(i.e., Di D ) tend to be uniquely related to the combined effect of

asphalt concrete and base courses. As shown in Figure 4.2, modified

sensor position 1 is located adjacent to one of the Dynaflect wheels,

6.0 in. transversely from standard sensor position 1; and the modified

sensor 4 is positioned 4.0 in. longitudinally from the standard position

of sensor 1. This deflection difference essentially eliminated the

effect of the underlying layers and was primarily dependent upon the