Figure 13-8.Laboratory CBR test equipment and tools.
specimens are prepared; second, a penetration test is
performed upon the prepared soil samples. Although
one standardized procedure has been established for the
penetration portion of the test, it is not possible to
establish one procedure for the preparation of test
specimens since soil conditions and construction
methods vary widely. The soil test specimens are
prepared to duplicate the soil conditions existing (or
expected to occur later) in the field. Although
penetration tests are most frequently performed on
laboratory-compacted test specimens, they may also be
performed upon undisturbed soil samples or in the field
upon the soil in place. Detailed procedures for preparing
the test samples and performing the test can be found in
CBR Test Equipment and Tools
Figure 13-8 illustrates the equipment and tools
needed to perform the CBR test. The principal piece of
equipment is the CBR loading press. It is used to force
the penetration piston into the compacted CBR
specimen. The complete loading-press assembly (fig.
13-9) includes a penetration piston, proving ring and
proving-ring dial, penetration dial, and a mechanical (or
Figure 13-9.Assembled CBR loading press.