TYPES OF SOILS | Alluvial Soils | Loams | Peat | Black Cotton Soil | Cohesive Soil | Organic Soil

TYPES OF SOILS


1) Alluvial Soils :

Soils carried and deposited by water are known as alluvial soils. 


2) Lacustrine Soils :

Soil particles carried by flowing water and deposited in lakes are called Lacustrine soil.


3) Marine Soils :

Marine soils are formed when the flowing water carries soil to ocean or sea.


4) Aeolian Soils :

Soils deposited by wind are known as Acolian Soils e.g. Sand dunes, Loess.


5) Glacial Soil (drift) :

Glaciers carry with them soils varying in size from fine grained to huge boulders Soils get mixed with the ice and are transported far away from their original position. Drift is a general term used for the deposits made by glaciers.


6) Loam :

It is a mixture of sand, clay and silt.


7) Clay :

It is a fine grained soil. It is a cohesive soil. The particle size is less than 0.002 mm.


8) Colluvial Soil :

Soils transported and deposited by gravity are called Colluvial soil. e.g. talus.


9) Humus:

It is a dark brown, organic amorphous carth of the topsoil. It consists of partly decomposed vegetable matter. It is not suitable for engineering works.


10) Black Cotton Soil :

It is a residual soil containing high percentage of the clay mineral montmorillonite. bearing capacity. It possess high swelling and shrinkage properties.


11) Moorum : 

The word moorum is derived from a Tamil word, meaning powdered rock. It consists of small pieces of disintegrated rock or shale, with or without boulders. It is gravel mixed with red clay.


12) Sand:

It is a coarse grained soil, having particle size between 0.075 mm to 4.75 mm. The soil is cohesionless and pervious


13) Gravel:

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


14) Boulders:

Boulders are rock fragments of large size, more than 300 mm in size.


15) Residual soils:

Residual soils are those that remain at the place of their formation as a result of the weathering of the parent rocks. The depth of residual soils depends primarily on climatic conditions and the time of exposue. In temperate zones residual soils are commonly stiff and stable. An important characteristic of residual soil is that the sizes of grains are indefinite.

e.g. Black cotton soils, Laterite soils 


16) Organic soils:

Organic soils are formed by growth and subsequent decay of vegetable matter. e.g. peat, humus, muck


17) Inorganic soils:

Inorganic soils are formed by the accumulation of fragments of the inorganic skeletons or shells of organisms.


18) Bentonite:

It is a type of clay with a very high percentage of clay mineral montmorillonite. It is a highly Plastic Clay It is highly water absorbent and has high shrinkage and swelling characteristics. It is chemically weathered volcanic ash.


19) Peat :

A fibrous aggregate of finer fragments of decayed vegetable matter. Peat is very compressible and one should be cautious while using for supporting foundations of structures.


20) Loess:

This is a fine grained, air bome deposit characterised by a very uniform grain size, and high void ratio. The size of particles range between 0.01 to 0.05 mm. The soil can stand deep vertical cuts. Its colour is yellowish light brown.


21) Cohesive soils : 

Soils in which the absorbed water and particle attraction act such that it deforms plastically at different water contents are known as cohesive soils or clays.

Cohesive property of these soils is due to the presence of clay minerals like montmorillonite, illite or kaolinite. These soils posses higher plasticity. Clays and plastic silt are termed as cohesive soils. 


22) Cohesionless soil:

The soils composed of bulky grains are cohesionless regardless of the fineness of the particles. The rock flour is cohesionless even when it has the particle size smaller 24 size. Non-plastic silts and coarse grained soils are cohesionless. Sand and gravel are cohesionless.


23) Varved clay: 

Soil containing alternate thin layers of clay and silt.

Gravitational forces are predominant in gravels and sands. Surface forces, chemical forces and electrical forces are predominant in clays.


24) Hardpan:

A layer of extremely hard, cohesive soil that can hardly be drilled with ordinary earth boring tools is called hardpan. It does not soften when wet Boulder clays or glacial till is also sometimes named as hardpan.


25) Kankar:

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


26) Marl :

It is a crumbly mixture of clay, sand and limestone with shell fragments, with clay content not more than 75 % and lime content not less than 15 %. It is also designated as marine calcareous clay and is usually of greenish colour.


27) Muck :

It is a mixture of fine grained soil and highly decomposed organic matter. It is black in colour. 


28) Kaolin, china clay:

A very pure form of white clay used in the ceramic industry.


29) Tuff :

It is a fine grained soil composed of very small particles ejected from volconoes during explosion, and transported and deposited by wind or water. 


30) Diatomaceous earth:

Diatoms are the minute unicellular marine organisms. Diatomaceous earth is a fine, light grey, soft sedimentary deposits of the silicous remains of the skeletons of the diatoms.

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