Some Commonly Used Soil Designations

The following are some commonly used soil designations, their definitions and basic properties:

Bentonite: Decomposed volcanic ash containing a high percentage of clay mineral— montmorillonite. It exhibits high degree of shrinkage and swelling.

Black cotton soil: Black soil containing a high percentage of montmorillonite and colloidal material; exhibits high degree of shrinkage and swelling. The name is derived from the fact that cotton grows well in the black soil.

Boulder clay: Glacial clay containing all sizes of rock fragments from boulders down to finely pulverised clay materials. It is also known as ‘Glacial till’.

Caliche: Soil conglomerate of gravel, sand and clay cemented by calcium carbonate.

Hard pan: Densely cemented soil which remains hard when wet. Boulder clays or glacial tills may also be called hard-pan— very difficult to penetrate or excavate.

Laterite: Deep brown soil of cellular structure, easy to excavate but gets hardened on exposure to air owing to the formation of hydrated iron oxides.

Loam: Mixture of sand, silt and clay size particles approximately in equal proportions; sometimes contains organic matter.

Loess: Uniform wind-blown yellowish brown silt or silty clay; exhibits cohesion in the dry condition, which is lost on wetting. Near vertical cuts can be made in the dry condition.

Marl: Mixtures of clacareous sands or clays or loam; clay content not more than 75% and lime content not less than 15%.

Moorum: Gravel mixed with red clay.

Top-soil: Surface material which supports plant life.

Varved clay: Clay and silt of glacial origin, essentially a lacustrine deposit; varve is a term of Swedish origin meaning thin layer. Thicker silt varves of summer alternate with thinner clay varves of winter.

Some Commonly Used Soil Designations, Bentonite, Black Cotton Soil, Boulder Clay, Caliche, Loess, Loam, Varved Clay, Laterite

--- [TcGeoTeknik] Detailed Academic Knowledge on Soil Mechanics, Geotechnical Engineering, In-Situ and Laboratory Soil Tests, Plaxis, GeoStudio, Geo5, MatLAB, Word, Excel, PowerPoint and AutoCAD.

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