Technical information

3-38
24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120 126 132 138 144 150 156 162 168 174 180 186 192 198 204 210 216
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
-0.65--0.50 -0.50--0.35 -0.35--0.20 -0.20--0.05 -0.05-0.10 0.10-0.25 0.25-0.40 0.40-0.55
Location in Y [in.]
Lateral Offset in X
Pass #90,000
Figure 3.5.18: Contour plot of Section n1 rutting after 90,000 passes.
3.6 DIRECT COMPARISON WITH NCAT RESULTS
Assuming similar pavement systems were built at NCAT and in the APT, there should
be a way to relate the two experiments. The simplest and most direct method of analysis
is to compare the observed behavior by contrasting (separately) the observed
performance and response.
In the NCAT study the N1 (and N2) pavement failed predominantly in fatigue
mode (see Figure 2.5.5) while very little rutting was observed. The maximum recorded
rut depth (Figure 2.5.6) was 0.31 in. (8 mm). In contrast, in the APT study very little (if
any) cracking occurred, and the n1 pavement experienced under the first 90,000 passes
alone (see Table 3.4.1) maximum rutting of about 0.65 in. (11.5 mm) and heaving of
similar magnitude (see Figure 3.5.18).
NCAT responses to one truck pass were shown in Figures 2.5.1 to 2.5.4. Each
figure includes strain or stress pulses recorded by one gauge. As can be seen, one pass
induced eight pulses with different peak magnitudes even for nominally identical axle
loads. Also, the pavement was allowed to rest for 45 seconds between truck passes
(assuming three running trucks) and for about two full days during weekends. APT