geotech (version 1.0)

Plasticity: Plasticity Functions

Description

These functions compute diferent aspects related to plasticity:

• LL calculates and plots a soil's liquid limit (LL) using the flow curve from measured lab data.
• PI calculates plasticity index.
• LI calculates liquidity index.
• A.line calculates the PI corresponding to the A-line on Casagrande's plasticity chart.
• plasticity.plot plots a soil's plasticity parameters on Casagrande's plasticity chart.

Usage

LL(N, w, draw)
PI(LL, PL)
LI(w, LL, PL)
A.line(LL)
plasticity.plot(LL, PL = NA, PI = NA)

Arguments

LL

Liquid Limit (percent)

PL

Plastic Limit (percent)

PI

Plasticity index (percent)

w

moisture content (percent) [see details below]

N

vector of number of blows obtained from the liquid limit test (for LL function)

draw

logical variable: TRUE if plot of flow curve is desired, and FALSE to suppress the creation of the plot (for LL function)

Value

• LL outputs a soil's liquid limit and, optionally, a plot of the soil's flow curve.
• PI outputs a two-element list composed of:
  1. PI = Plasticity index (percent)
  2. descr = qualitative description of soil based on Sowers (1979)
• LI outputs a two-element list composed of:
  1. LI = Liquidity index (percent)
  2. descr = qualitative description of soil based on Sowers (1979)
• A.line outputs the plasticity index corresponding to the A-line on Casagrande's plasticity chart
• plasticity.plot is used to make a plot of a soil's plasticity parameters (LL and PI) on Casagrande's plasticity chart. No numerical values are output from this function.

Details

• Note that all inputs should be entered as percents, not decimals (e.g. w = 23, not w = 0.23)
• The argument w (water content) should be a single value for the LI function that represents the soil's in-situ moisture content; and w should be a vector of values for the LL function that represent the measured water contents, each with N blows.
• For plot.plasticity and A.line, either PL or PI must be specified in addition to LL.

References

Casagrande, A.M. (1948). "Classification and Identification of Soils", ASCE Transactions, Vol. 113, pp. 901-991.

Sowers, G.F. (1979). "Introductory Soil Mechanics and Foundations: Geotechnical Engineering", 4th edition, Macmillan, New York.

See Also

USCS, AASHTO, grainSize

Examples

## Example code for Plasticity Index
PI(LL = 80, PL = 30)

## Example code for Liquidity Index
LI(w = 55, PL = 20, LL = 50)

## Example code for plasticity plot
plasticity.plot(LL = 40, PL = 20)

## Example code for liquid limit analysis
LL(N = c(72, 37, 14), w = c(7, 15, 21), draw = TRUE)