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CLASSIFICATION OF SOILS
ASTM/Unified Soil Classification System

ASTM D 2487

Standard Specifications for Soils

Classification of Soils For Engineering Purposes (Unified Soil Classification System)

Standard ASTM D 2487-11

ASTM D 2487 soil classification system, an ASTM version of the Unified Soil Classification System, classifies mineral and organo-mineral soils for engineering purposes based on its particle-size characteristics, liquid limit, and plasticity index. Please note that, this soil classification standard is limited to naturally occurring soils. Also, the group symbol portion of this classification system is applicable on the portion of the soil sample passing 75 mm (3 in.) sieve.

ASTM D 2487 soil classification system identifies three major soil divisions: coarse-grained soils, fine-grained soils, and highly organic soils which are further subdivided into a total of 15 basic soil groups. The soil is catalogued according to the basic soil groups, assigned a group symbol(s) and name, and classified.
A sample composed primarily of vegetable tissue in various stages of decomposition and has a fibrous to amorphous texture, a dark-brown to black color, and an organic odor is designated as a highly organic soil and is classified as peat, PT. Peat is not subjected to the classification procedures described in ASTM D 2487. Instead, classification of type of peat can be performed in accordance with ASTM D 4427.
Median size and Effective Size: The diameter of soil particles at which 50% passes (i.e., 50% of the soil by weight is finer than this size) is known as the median size (denoted by D50). The diameter at which 10% passes is called the effective size (denoted by D10).
Coefficient of Uniformity and Curvature: Coefficient of Uniformity,  C u = D 60 D 10 Coefficient of Curvature,  C c = D 30 2 D 60 × D 10 where D10, D30, D60 are the diameter of soil particle corresponding to 10%, 30% and 60% finer respectively.

Using the Plot:
The generated plasticity chart is interactive and can be zoomed in or out and hovered over for additional data display. The plot can be saved by using the toolbars located on the top right of each plot. Please make use of the help texts provided in each input cell for further guidance on the usage of this tool.

Boulders

Particles of rock that will not pass a 12 in. (300 mm) square opening.

Cobbles

Particles of rock that will pass a 12-in. (300-mm) square opening and retained on a 3-in. (75-mm) sieve.

Gravel

Particles of rock passing a 3-in. (75- mm) sieve and retained on a No. 4 (4.75-mm) U.S. standard sieve. Further classified into Coarse and Fine Gravel.
Coarse Gravel —passing 3-in. (75-mm) sieve and retained on 3⁄4-in. (19-mm) sieve.
Fine Gravel —passing 3⁄4-in. (19-mm) sieve and retained on No. 4 (4.75-mm) sieve.

Sand

Particles of rock passing a No. 4 (4.75- mm) sieve and be retained on a No. 200 (75-μm) sieve with the following subdivisions:
Coarse Sand — passing No. 4 (4.75-mm) sieve and retained on No. 10 (2.00-mm) sieve
Medium Sand — passing No. 10 (2.00-mm) sieve and retained on No. 40 (425-μm) sieve.
Fine Sand — passing No. 40 (425-μm) sieve and retained on No. 200 (75-μm) sieve.

Silt

Soils which are nonplastic or very slightly plastic and that exhibits little or no strength when air dry and passing a No. 200 (75-μm) sieve. For classification purposes, silt is considered as a fine-grained soil, or the fine-grained portion of a soil, with a plasticity index less than 4 or if the plot of plasticity index versus liquid limit falls below the “A” line (plasticity chart).

Clay

Soil passing a No. 200 (75-μm) sieve that can be made to exhibit plasticity within a range of water contents and that exhibits considerable strength when air dry. For classification, clay is a fine-grained soil, or the fine-grained portion of a soil, with a plasticity index equal to or greater than 4, and the plot of plasticity index versus liquid limit falls on or above the “A” line.

Organic Silt

Silt with sufficient organic content to influence the soil properties. For classification, an organic silt is a soil that would be classified as a silt except that its liquid limit value after oven drying is less than 75 % of its liquid limit value before oven drying.

Organic Clay

Clay with sufficient organic content to influence the soil properties. For classification, an organic clay is a soil that would be classified as a clay except that its liquid limit value after oven drying is less than 75 % of its liquid limit value before oven drying.

Peat

Soil composed of vegetable tissue in various stages of decomposition usually with an organic odor, a dark-brown to black color, a spongy consistency, and a texture ranging from fibrous to amorphous.


Coefficient of Curvature and Uniformity




Coefficient of Uniformity and Curvature

Coeff of Uniformity:

Coeff of Curvature:

ASTM Soil Classification

When the liquid limit cannot be determined, please enter a Liquid Limit value of 0.

For non plastic materials, please enter a Plasticity Index value of 0.

For soils dark in color with organic odor when moist and warm, liquid limit test shall be performed on soil specimen oven dried at 110 ± 5°C.



ASTM Soil Classification

Percent Gravel:

Percent Sand:

Soil Group Symbol:

Soil Group Name:

REPORT SECTION

Please enter the Project Details to appear on the generated pdf report.

Please enter the Sample Details to appear on the generated pdf report.

Please enter brief remarks to appear on the generated pdf report.

PLASTICITY CHART


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