In situ determination of borrow density

[lcruzz01]

A client needed the maximun dry density and optimum moisture content from a borrow sample. He also needed the in situ density to calculate the swelling index, but I told him we needed to perform the sand cone or use the nuclear gauge. One of my lab technicians (really old) told me that the field density is almost equal to 95% modified proctor and I recall reading that in an old geotechnical book. I don't believe in using this correlation. What do you guys think?

 

[fattdad]

I think the whole topic of "swelling index" is confusing. That said, if the soil in the borrow pit happens to be at 95 percent compaction and the contractor actually places it at 95 percent compaction, there is no swell and all is right in the world.

Get a few samples of borrow, do the moisture-density relations, return to the job with a nuke gauge (or sand cone), measure the in-situ density and learn how it all works out.

Then again, if the borrow is residual sandy silt and the moisture content is well over optimum, you may find that 2 cubic yards in the borrow is less than 2 cubic yards in the fill. Some measure of drying and such will also be needed.

f-d

¡papá gordo ain’t no madre flaca!

 

[lcruzz01]

I'm sorry! I meant swell factor. Th technician used to calculate the swell factor using the loose density and the 95% modified proctor density instead of using the natural density of the soil.

 

[cvg]

shrink or swell, it doesn't matter. in-situ density is rarely ever the same as moisture conditioned compacted final density. you can either make an assumption or get some data and make an informed estimate.

 

[motorbiketocrank]

I agree with the responses. Assuming the natural density is at 95% of maximum isn't appropriate nor accurate.