soil classification

[JL40]

Hi all, I have been working in geotech for ~1 year (not including internships) and have found myself working in an office where I am the engineer and lab tech. I know how to run the tests thanks to my schooling and internship, but don't have much experience with what is a "normal" result, particularly with grain size analysis. I have some samples that I am running and I have curves with near horizontal segments in the sieve/hydrometer report. These same curves have coefficient of uniformity values >10.
Is this a reasonable value? I have looked and looked but can not find a typical range of Cu values to compare against. Thank you!

 

[oldestguy]

A well graded silty, sand and gravel, with clay can be between 25 and 1000 for Cu, for no clay maybe 15 to 300 silty sand and gravel.

Most other soils between 1 and 10

 

[dgillette]

Gsp-graded soils (lacking grains of certain sizes, therefore having flat portions in their gradation curves) do indeed exist. They can be a real headache for dam foundations and cores.

 

[richardx1]

Use Civillabs.com to check your soil classification