Figure 13-8.—Laboratory CBR test equipment and tools.specimens are prepared; second, a penetration test isperformed upon the prepared soil samples. Althoughone standardized procedure has been established for thepenetration portion of the test, it is not possible toestablish one procedure for the preparation of testspecimens since soil conditions and constructionmethods vary widely. The soil test specimens areprepared to duplicate the soil conditions existing (orexpected to occur later) in the field. Althoughpenetration tests are most frequently performed onlaboratory-compacted test specimens, they may also beperformed upon undisturbed soil samples or in the fieldupon the soil in place. Detailed procedures for preparingthe test samples and performing the test can be found inNAVFAC MO-330.CBR Test Equipment and ToolsFigure 13-8 illustrates the equipment and toolsneeded to perform the CBR test. The principal piece ofequipment is the CBR loading press. It is used to forcethe penetration piston into the compacted CBRspecimen. The complete loading-press assembly (fig.13-9) includes a penetration piston, proving ring andproving-ring dial, penetration dial, and a mechanical (orFigure 13-9.—Assembled CBR loading press.13-11
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