What is meant by "standard effort" in the context of compaction?

In the context of compaction, "standard effort" refers to a specific level of mechanical energy applied to compact a soil sample, which is standardized for consistency in testing. The value of 12,400 lbf/ft³ pertains to the Standard Proctor test, which is used to determine the maximum dry density and optimum moisture content of soils.

This test involves a specific procedure where soil is compacted into a mold using a standardized weight dropped a certain height, and the resulting density provides a reference for evaluating soil compaction in the field. The established standard effort helps ensure that any comparisons or assessments made regarding soil density are based on the same compactive energy, allowing for reliable evaluations of how well a specific soil has been compacted in earthwork projects.

Other values like 56,000 lbf/ft³, 10,000 lbf/ft³, and 14,000 lbf/ft³ represent different compaction energies or may not correspond to standard methodologies employed in soil testing. Thus, they do not reflect the designated standard effort recognized in the industry for typical soil compaction measurements.