Overlay Design

a

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0

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*a. Overlay design.*

Spacing between Test Points (ft)

b

Network Level

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*b. Network level.*

Spacing between Test Points (ft)

*Figure 3. Distance between NDT test points.*

improving both employee and public safety), and

of FWD test points. Following completion of pave-

3) guaranteeing that adequate data are collected

ment strength variability analysis, we hope to

for overlay design and pavement evaluation.

minimize the cost for overlay design and pave-

Classical statistics can address random vari-

ment evaluation by developing a computer pro-

ability, but neglects relative positions of test points.

gram to optimize the number and location of

However, there currently exist several less tradi-

FWD test points. Ideally, it would continually

tional mathematical models that can quantify spa-

adjust the optimal distance to the next test point

tial variability of pavement properties.

in real time as data are collected in the field. Based

The following is a simplified look at a geo-

upon preliminary work, this continually adjust-

ing optimal test point configuration computer pro-

statistical model that provides the basis for the

proposed test point spacing optimization program.

gram would maximize efficiency of FWD testing

Test points located close together (e.g., the 10-ft

by 1) eliminating both undertesting and over-

grid in Fig. 4a) yield similar test values. The vari-

testing (thereby eliminating underdesign and over-

ance (or statistical measure of spread) of differ-

design), 2) minimizing lane closure time (thereby

4