Terminology of Soil

Hello, friends today I am going to share about some terminology of soil.


Terminology of different types of soil

A geotechnical engineer should be well versed with the nomenclature and terminology of different types of soils. The following list gives the names and salient features of different types of soil, arranged in alphabetical order.

Bentonite: It is a type of clay with a very high percentage of clay mineral – montmorillonite. It is a highly plastic clay, resulting from the decomposition of volcanic ash. It is highly water absorbent and has high shrinkage and swelling characteristics.
Black cotton soil: It is a residual soil containing a high percentage of the clay mineral – montmorillonite. It has very low bearing capacity and high swelling and shrinkage properties.



Boulders :- Boulders are the rock fragments of large size, more than 300mm in size.
Calcareous soil: This type of soil contains a large quantity of calcium carbonate. Such soils effervesce when tested with weak hydrochloric acid.
Caliche: It is a type of soil which contains gravel, sand and silt. The particles are cemented by calcium carbonate.



CIay : It consists of microscopic and sub-microscopic particles derived from the chemical decomposition of rocks. It contains a large quantity of clay mineral. It can be made plastic by adjusting the water content. It exhibits considerable strength when dry. Clay is a fine-grained soil. It is a cohesive soil. The particle size is less than 0.002mm.
Organic clay contains finely divided organic matter and is usually dark grey or black in colour. It has a conspicuous odour. Organic clay is highly compressible and its strength is very high when dry.


Cobbles:- Cobbles are large size particles in the range of 80mm to 300mm.
Diatomaceous earth: Diatoms are minute unicellular marine organisms. Diatomaceous earth is a fine, light grey, soft sedimentary deposit of the silicious remains of skeletons of diatoms.



Dispersive soil: These are special type of clays which defloculate in still water. Such soils erode if exposed to low-velocity water. Susceptibility to dispersion depends upon the cations in the soil pore water.



Dune sand : These are wind-transported soils. These are composed of relatively uniform particles of fine to medium sand.


Expansive clays: These are prone to large volume changes as the water content is changed. These soils contain the mineral montmorillonite.


Fills: All manmade deposits of soil and waste-materials are called fills. These are the soil embankments raised above the ground surface. Engineering properties of fills depend upon the type of soil, its water content and the degree of compaction.


Gravel: It is a type of coarse-grained soil. The particle size ranges from 4.75mm to 80mm. It is a cohesion-less material.


Hardpans: H8ardpans are the types of soil that offer great resistance to the penetration of drilling tools during soil exploration. The soils are designated hardpans regardless of their particle size. These are generally dense, well-graded, cohesive aggregates of mineral particles. Hardpans do not disintegrate when submerged in water.


Humus: It is a dark brown, organic amorphous earth of the topsoil. It consists of partly decomposed vegetal matter. It is not suitable for engineering works.


Kankar: It is an impure form of lime stone. It contains calcium carbonate mixed with some silicious material.


Laterites: Laterites are residual soils formed in tropical regions. Laterites are very soft when freshly cut but become hard after long exposure. Hardness is due to cementing action of iron oxide and aluminium oxide. These soils are also called lateritic soils.


Loam: It is a mixture of sand, silt and clay. The term is generally used in agronomy. The soil is well suited to tilling operations.


Loess: It is a windblown deposit of silt. It is generally of uniform gradation, with the particle size between 0.01 and 0.05 mm. It consists of quartz and feldspar particles, cemented with calcium carbonate or iron oxide. When wet, it becomes soft and compressible because cementing action