Soil Plasticity Chart

Classification of Fine Grained Soils/Fine Grained Fraction of Coarse Grained Soils

Soil Plasticity Chart

Reference ASTM D 2487

Plasticity Chart, developed by Arthur Casagrande (1932) is a plot of the Plasticity Index (PI) versus the Liquid Limit (LL) of soils. The chart is used for the classification of fine grained soils (or fine grained fraction of coarse grained soils) based on their plasticity.

The plasticity chart comprises of two important lines, A-line and U-line.
A-line is an empirically chosen line which separates the chart between clays and silts; soils that fall above A-line are classified as clays and that falling below as silts. A-line is given by the equation PI=0.73(LL-20).
U-line lies above the A-line and is approximately the upper limit of the relationship of PI to LL, for any currently known soil. The equation of U-line is given as PI=0.9(LL-8).
There is also a vertical line in the plasticity chart which corresponds to a liquid limit of 50% and separates the high plasticity fine grained soils (LL>50%) from low plasticity fine grained soils (LL<50).
To classify as soil based on the plasticity chart, plot the PI and LL of the soil on the chart; the region in which the point falls indicates the type of fine-grained soil it is.

Plasticity Chart - Input

Liquid Limit Plasticity Index


To advertise, please contact .


The information and calculation tools provided on website (the "Service") is for general information purposes only. TransCalc assumes no responsibility for errors or omissions in the contents on the Service.In no event shall TransCalc be liable for any special, direct, indirect, consequential, or incidental damages or any damages whatsoever, whether in an action of contract, negligence or other arising out of or in connection with the use of the Service or the contents of the Service. TransCalc reserves the right to make additions, deletions, or modification to the contents on the Service at any time without prior notice.