geopiet May 7, 2017:

checkpoint or check plug? One-point "Proctors" are only useful to determine whether or not the correct curve is being used for testing, and/or to interpolate between curves where multiple soils are present on which moisture-density relationships have been determined, and where mixing will occur. In the latter case, you should plot all the Proctor curves on one sheet of graph paper so the one-point "Proctor" can be plotted and the probable curve roughed in order to estimate %relative compaction.

In the former case, if the one-point "Proctor" (aka checkpoint or check plug) is very far from any previously obtained moisture-density relationships, then a new moisture-density relationship should be determined for the soil represented by the check point. - http://www.eng-tips.com/viewthread.cfm?qid=73768