USCS: USCS Soil Classification

In geotech: Geotechnical Engineering

Description

This set of functions classifies soil using the Unified Soil Classification System (USCS).

Usage

USCS(pg = NA, ps = NA, pf = NA, Cc = NA, Cu = NA,
     LL = NA, PL = NA, PI = NA, sieve = NA, size = NA,
     percent = NA, metric = NA)
USCS.fine.symbol(LL, PL, PI = NA)
USCS.coarse.symbol(pg, ps, pf, Cc, Cu, PI = NA, LL, PL)

Arguments

pg	percent gravel
ps	percent sand
pf	percent fines
Cu	coefficient of uniformity
Cc	coefficient of curvature
sieve	vector of sieve numbers (according to ASTM D422) in grain-size distribution
size	vector of grain sizes (in or mm) in distribution
percent	vector of percent passing in grain-size distribution
metric	logical variable for grain-size distribution: TRUE for metric units (mm), FALSE for English units (in); only required if "size" is supplied
LL	liquid limit (percent)
PL	plastic limit (percent)
PI	plasticity index (percent)

Details

The USCS function is the master function for performing soil classifications:

• Data on the soil's grain-size distribution are required if the percent fines is less than or equal to 12 percent. The user has three options for input to this function:

  1. Sieve numbers (sieve); and percent passing

  2. Grain sizes (size); and percent passing

  3. Percent components (pg, ps, pf) and coefficients of uniformity and curvature (Cc and Cu)

• Data on the soil's fines [either (a) LL and PL or (b) LL and PI] are required if the percent fines is greater than or equal to 5 percent.

• If percent components are specified, then Cu and Cc are needed if pf < 85 percent.

The USCS.fine.symbol and USCS.coarse.symbol are used to obtain the group symbols for fine-grained and coarse-grained soils, respectively. For USCS.fine.symbol, either PI or PL must be specified in addition to LL. For USCS.coarse.symbol:

• Data on the soil's gradation (Cu and Cc) are required if the percent fines is less than or equal to 12 percent.

• Data on the soil's fines [either (a) LL and PL or (b) LL and PI] are required if the percent fines is greater than or equal to 5 percent.

Value

• USCS outputs a two-element list providing a soil's USCS group symbol and name:

  1. symbol = USCS group symbol

  2. name = USCS group name

• USCS.fine.symbol outputs a fine-grained soil's two-letter group symbol.

• USCS.coarse.sybmol outputs a coarse-grained soil's two-letter group symbol.

Author(s)

James Kaklamanos <[e-mail]> and Kyle Elmy <[e-mail]>

References

ASTM (2010). "Annual Book of ASTM Standards", Volume 04.08 – Soil and Rock, ASTM International, Philadelphia.

See Also

AASHTO, grainSize, Plasticity

Examples

## Example code for USCS
USCS(pg = 15, ps = 34, pf = 51, Cc = 1, Cu = 4, LL = 40, PL = 10)

Example output

$symbol
[1] "CL"

$name
[1] "Sandy lean clay with gravel"

geotech documentation built on May 1, 2019, 9:09 p.m.