Talk:Unified Soil Classification System

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Adding an Explanation of Peat[edit]

I would like to request that an explanation for Pt be added. I remember that it is peat, and is different from the other soil types because it is highly organic. mgoins (talk) 23:30, 26 April 2016 (UTC)

LL units?[edit]

What units are being cited for the liquid limit? That article does not specify this either. I would expect weight percent, but I'm no soil scientist!! DefMorn 19:01, 5 September 2006 (UTC)

Liquid Limit test results are technically a dimensionless number, according to the definition of the test, but in reality, the liquid limit is the water content (expressed as a percentage of dry weight) at which the soil transitions from a plastic to liquid state. Argyriou 20:53, 5 September 2006 (UTC)

Is there a "bedrock" classification?[edit]

I was working with a document that used USCS symbols. I see all the symbols in this Wikipedia article that were included in that document with the exception of "Rx," which was used to denote "bedrock." Is "Rx" an actual USCS symbol or is it a symbol created by the author(s) because there is no symbol for "bedrock."? Thanks! Unfoldingfire 23:21, 20 February 2007 (UTC)

"Rx" is not a USCS symbol, nor have I encountered it in any documentation of USCS symbols. Rocks are not soil (since they are consolidated), which is why we don't see it here. However, I've certainly seen similar symbols for bedrock in soil survey databases, since it needs to somehow be classified. So it is an appropriate modification of the USCS, but not encyclopedic to include in the front page.+mwtoews 23:49, 20 February 2007 (UTC)

grading vs sorting[edit]

I repost here my reply to User:Mwtoews at User talk:Argyriou#grading:

Gap-graded soils are not terribly common, but do exist. Many beach sands have a large number of particles in the range of 0.5 to 1mm, and a small but noticeable amount of particles in the 5mm+ size, with almost nothing between 1mm and 5mm. That's "poorly sorted", but also "poorly graded". You (and Britannica) are correct in thinking that generally well-graded is poorly-sorted and vice-versa, but it's not an exact relation. Furthermore, the criteria for "well-graded" in the USCS are pretty stringent; there are probably many sands which don't quite meet the USCS criteria for "well-graded", but which are also not "well-sorted" in a sedimentology sense. A former boss of mine ended up running 400 sieve analyses on natural sands from near the All-American Canal in Southern California. 397 of the sands were "poorly graded" by USCS criteria; only 3 passed the requirements for SW. I'm sure a sedimentologist would find many more than 3 of those samples to be "poorly sorted". Αργυριου (talk) 00:42, 11 May 2007 (UTC)

no. sieves[edit]

It may be useful not to use No. for sieves as it confuses geotechnicians. mm or microns might be more understandable. david beasley —The preceding unsigned comment was added by (talk) 07:39, 13 May 2007 (UTC).

Symbol M for Silt[edit]

I understand M is used instead of S because S is already used for sand, but does anybody what M stands for? Initial letter of the word for "silt" in another language? —Preceding unsigned comment added by (talk) 19:54, 13 February 2009 (UTC)

Who created the system? How widely used is the system?[edit]

The page just says it's a "system used in engineering and geology" but does not say how old the system is or the origins.

Is this the defacto soil classification system which everyone uses? Or is it a system which only a few companies or countries use? How does this system compare to other systems? Why is it called 'Unified'? - (talk) 20:42, 23 July 2017 (UTC)