TM 5-822-5/AFM 88-7, Chap. 1
fore the reduction Will be affected in the subbase
consideration will be given to the sensitivity of the
course immediately above the subgrade. when only
subgrade to small increases in moisture content
limited rainfall records are available, or the annual
before any reduction in thickness is made.
precipitation is close to the 15-inch criterion, careful
requirements will necessitate an increase in
8-5. Example Thickness Design-Conventional
subgrade density to a depth of 9 inches below the
Flexible Pavements.
subgrade surface and that a soft layer occurs within
This example illustrates design by the CBR method
the subgrade 24 inches below the subgrade surface.
when the subgrade, subbase, or base course
The CBR design values of the various subgrade
materials are not affected by frost. Assume that a
layers and the materials available for subbase and
design is to be prepared for a road that will require
base course construction are as follows:
a design index of 5. Further assume that compaction
8-2
Previous Page
