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

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`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) |

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:

Sieve numbers (sieve); and percent passing

Grain sizes (size); and percent passing

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.

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

symbol = USCS group symbol

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.

James Kaklamanos <kaklamanosj@merrimack.edu> and Kyle Elmy <ElmyK@merrimack.edu>

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

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