Rock correction issues in compaction specifications for high gravel content soil

Reference dry density is a crucial factor in the construction control for engineered fills. This factor is usually measured using laboratory compaction tests. However, there are some cases wherein laboratory compaction tests become ineffective. Thus contractor and engineer must rely on experience with the performance of high gravel content fills at certain specified percentages of a reference dry density, selecting specification requirements appropriate to individual circumstances. Currently, there are several methods which can be used to account for the effect of the coarse fraction on the reference dry density such as rock correction equations and laboratory scalp-and-replace techniques. Each method may provide a different reference dry density. In this article, the issues related to the implementation of these methods are addressed.