modulus of deformation, constrained modulus) can easily double when the density increases from 85 to 95 percent compaction (Gemperline and Gemperline 2011).
This increased soil stiffness reduces the settlement beneath a loaded structure, reduces the deflection of buried flexible pipe, and increases the support of haunch embedment for rigid pipe.
Other published comparisons of stiffness (or strength) show increases up to 600% when cohesionless soils, such as gravels, are compacted to high densities (Howard when the gravel density goes from uncompacted to 95 percent compaction.
That future should be protected by proper installation.
NOTES: Raining cohesionless soils (pluviation) in a laboratory testing is sometimes used to create high densities for research projects.
Applied to pipeline installation, dumped gravel around a pipe is more likely about 80 to 85 percent of the maximum density.
Note that laboratory vibratory tests are used to determine the maximum density.
Owners, engineers, contractors and inspectors have been known to use this expression.
Some even claim that dumping in gravel and crushed rock will result in 95 percent compaction meaning that the density of the dumped soil is 95 percent of the maximum density for that soil.
The data show that the minimum density is generally 75 to 85 percent of the maximum density with 80 percent being a representative average.
These studies are discussed in the Technical Note “Self-Compacting
In reality, the dumped density is only about 80 percent of the maximum density.