Compaction of granular fill

[SkipR]

Often we are asked by inspectors to verify the compaction rate of 1/2" clean-crushed stone or well-graded gravel fill that has been placed on undisturbed soil. I have been told that there are no testing standards for homogeneously sized material, short of nuclear equipment, and that these materials reach a 90-95% AASHTO standard density without compaction. Typically the depth of fill is under one foot in thickness and the bearing loads are in the 3000-4000 psf range. Is my information correct and is there anything else I can say to satisfy them?

 

[cvg]

you could use the min/max index density, unit weight and specify a relative density of approx 70%. you can specify ASTM methods D4253 and D4254. The method is described in design manuals by the Corps and the BuRec for testing compaction of cohesionless, free draining soils. To avoid running the tests, you may also want to specify a certain number of passes with a roller or other prescriptive method for compaction. However for critical applications such as in a dam embankment, the relative density method is normally used.

Chuck
cgopperton@stantec.com

http://www.stantec.com/

 

[snafuman]

Clean washed uniform sized gravels pretty much falls out of the dump truck at maximum compaction. Running equipment over it just shifts the rocks around. There are few sands or fines to fill any voids, making compaction somewhat moot. However, I can't help you convince your inspectors of this.