Talk:Unified Soil Classification System

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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 203.214.53.61 (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 138.100.42.23 (talk) 19:54, 13 February 2009 (UTC)