142
exhibiting uniformity in Dynaflect deflection measurements. Table 5.2
lists those tests performed on each test pavement section.
5.3.2 Dynaflect Tests
Testing with the Dynaflect was accomplished using the standard
sensor spacing to identify segments of pavement with fairly uniform
deflection response. Each segment was tested at 25-ft. spacings until
three or more locations provided essentially identical deflection
basins. The modified Dynaflect sensor array was then used to obtain
deflection measurements. The sensors were positioned by hand at loca
tions designated as 1, 4, 7, and 10, as shown in Figure 4.2. These were
the best positions, based on the theoretical study, for separation of
layer response.
The initial part of the field testing involved placing the extra
sensor at position 9 in the modified system (standard position 4). This
procedure was later changed to placing one sensor near each Dynaflect
loading wheel and the remaining sensors placed at modified positions 4,
7, and 10. In the later case, an average value of Dx was used in the
analysis. Appendix A lists Dynaflect deflection measurements from each
test section.
5.3.3 Falling Weight Deflectometer Tests
The FWD measurements were conducted at approximately the same loca
tions as the Dynaflect. In the tests the height of drop and the weight
were adjusted to produce different load levels. Two to three drops
(load levels) were usually made, with the highest load often repeated.
The highest load was generally close to 9 kips. The exact magnitude of
each load applied was registered by a load cell located just above the
loading plate.