This set of functions classifies soil using the American Association of State Highway and Transportation Officials (AASHTO) Soil Classification System.

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`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 |

`p10` |
percent passing #10 sieve |

`p40` |
percent passing #40 sieve |

`p200` |
percent passing #200 sieve |

`LL` |
liquid limit (percent) |

`PL` |
plastic limit (percent) |

`PI` |
plasticity index (percent) |

`NP` |
logical variable indicating whether the soil is nonplastic (TRUE or FALSE) |

In the AASHTO function:

For the grain-size data, one of three following pieces of data must be specified:

Sieve numbers (sieve); and percent passing

Grain sizes (size); and percent passing

p10, p40, p200

If sieve data are specified, for sieves larger than the no. 4 sieve, the user should specify the sieve size in inches (e.g., 3/8, 3/4, 1, 1.5, 2, 3, etc.)

If sieve or size data are specified, this function assumes that the no. 10, 40, and 200 sieves have been used.

For the plasticity data, one of three following pieces of data must be specified:

LL and PL

LL and PI

NP (if the soil is nonplastic)

This function only calculates the AASHTO group classification. To obtain the AASHTO group index, use the GI function.

In the GI function, either PL or PI must be specified in addition to the required arguments: F and LL.

`AASHTO`

: AASHTO group classification`GI`

: AASHTO group index (rounded to the nearest integer)

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

American Association of State and Highway Transportation Officials [AASHTO] (1993). "Recommended Practice for the Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes", AASHTO Designtation 145-91, Standard Specifications for Transportation Materials and Methods of Sampling and Testing.

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

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