Technical information

5-29
backcalculated viscoelastic properties are associated with strain levels that are about
four times higher. Furthermore, the dissimilarity can originate from the differences in
aggregate structure between an HMA prepared in the laboratory versus an HMA
prepared using full-scale construction equipment.
Figure 5.2.4 shows the measured and calibrated model responses for APT pass
number 5,000. Six charts are included, each showing a different response vs. offset
distance from the gauge. With reference to Figure 3.5.1, the two topmost charts show
horizontal strains in X (left) and in Y (right) for gauges located along the loading
centerline (between the dual tires). The charts in the middle of the figure show
horizontal strains in X (left) and in Y (right) for gauges positioned outside the loading
path. The bottom charts show vertical stresses as measured by pressure cells located on
top of the base (left) and on top of the subgrade (right). In each chart the measured
gauge data is represented by two types of solid markers and the calibrated model
responses are shown using solid lines.
From the figure it may be graphically seen that the isotropic LVT captures
relatively well both the shape and magnitude of all measured responses except for the
vertical stresses on top of the base (gauges 1178 and 1185) which are under predicted. It
should be noted that the non-symmetry is the responses were also captured very well;
the LVT was able to simulate the differences between the approaching and receding
response branches and the delay in the peaks (occurring slightly after the load had
passed a gauge).