The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

OFS Soil Classificator: geotechnical software based on Atterberg’s system

Written By: Francesco Salvatore Onorio - Jul• 06•11

OFS Soil Classificator is a simple software that permits the soil classification by grain size. When referring to soils, we often hear terms like “clay”, “sand”, “gravel”, etc., which are primarily based on grain size. In the very beginning of the 20th century, Atterberg, a Swedish scientist and agriculturalist, proposed a classification system based on specific grain sizes. With minor modifications, the Atterberg system is still used and are the basis of the International Geotechnical Standard.

But a soil is made up of grains with a wide range of size, so we need more accurate specifications when naming it. This is the classification used by the International Geotechnical Society (and also by the Canadian standard, CFEM 1992):

“Noun” (clay, silt, sand, gravel)                  35 < X <= 100 %

“and” plus noun                                          20 < X <= 35 %

“adjective” (clayey, silty, sandy)                 10 < X <= 20 %

“trace” (clay, silt, sand, gravel)                  1 < X <= 10 %

So, let’s make some examples.


85% – 0.001 mm

15% – 0.06 mm

The soil is a silty clay.


88% – 0.2 mm

12% – 0.0015 mm

The soil is a clayey sand.


46% – 50 mm

48% – 4 mm

6% – 0.0015

The soil is composed by coarse and fine gravel with trace of clay.

You can download this software from this link:

OFS Soil Classificator v. 1.0

For guidance, reports and more you can contact the author at:

Eng. Onorio Francesco Salvatore

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