Lesson 1/Learning Event 3
Equivalent operations for a 2-year period: 365 days x 2 years x 5072 equivalent operations per
day = 3,702,560 or 3.7 x 106.
It can be seen that although the actual number of tracked vehicle operations is small, the number
of equivalent operations of tracked vehicles is very large and has the greatest influence on the
thickness requirements of all three vehicle categories.
Thickness Requirements.
The thickness requirements are found by using Figure 8.
Enter Figure 8 at 3.7 x 106 equivalent operations and proceed vertically to the CBR 10 line, then
horizontally to the left to the cover required. It is found that the CBR 10 material must have a
cover of 13 inches.
Table 8 indicates that the minimum thickness of pavement and base course for CBR 50 material
with an anticipated traffic of 3.7 x 106 equivalent operations is 3 1/2 inches of pavement and 4
inches of base course. This is in excess of the cover requirement of 4 inches over the CBR 40
material.
Figure 9, #1, illustrates the proposed design for the flexible pavement structure.
FIGURE 9. ROAD DESIGN
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