The figures above illustrate the sustainability of earthworks compaction for a soil with a loose dry density of 80 pcf being compacted to a target dry density of 135 pcf. 

Both density growth curves in the LEFT figure are effective in reaching the target density. The density growth curves in the RIGHT figure are ineffective since they fail to reach the target density regardless of the compactive effort provided.

The solid line curves on both figures show higher energy-efficiency than the dashed line curves.