Concept:

Soil is also classified based on mode of deposition or mode of transportation.

Soil deposit formed due to transportation by wind is called Aeolian deposit e.g. Loess

Important Points

According to transporting agencies, soil is classified as:

(i) Alluvial Deposit â†’ Deposited by river water.

 (ii) Lacustrine Deposit â†’ Deposited by still water lakes.

(iii) Marine Deposit â†’ Deposited by seawater.

(iv) Colluvial Deposit â†’ Deposited by gravity e.g. Talus

(v) Glacial Deposit â†’ Deposited by ice e.g. Till

The harmonic diameter DH can be found by using kozney?s method using formula
F=6/?s×1/Dn.

Explanation:

Suffix and prefix used in soil classification:

Additional Information  These symbols are used for classification of fine-grained soil in plasticity chart as given below:

Important Points 

The equation of "A" line for plasticity index, P.I = 0.73 ( WL - 20 )

The equation of "U" line for plasticity index, P.I = 0.9 ( WL - 8 )

In 1940, casagrande originally developed unified soil classification system (USCS).

The soils formed at a place may be transported to or places by agents of transportation, such as water, wind, ice, and gravity.

1) Water transported Soils: Flowing water is one of most important agents of transportation of soils. Swift running water carries a large quantity of soil eir in suspension or by rolling along bed.

The size of soil particles carried by water depends upon velocity.

All types of soils carried and deposited by water are known as alluvial deposits. Deposits made in lakes are called lacustrine deposits. Such deposits are laminated or varved in layers. Marine deposits are formed when flowing water carries soils to ocean or sea.

2) Wind transported Soils: Soil particles are transported by winds. The particle size of soil depends upon velocity of wind. Soils deposited by wind are known as aeolian deposits.

Loess is a silt deposit made by wind. These deposits have low density and high compressibility. The bearing capacity of such soils is very low.

3) Glacier-Deposited Soils: Glaciers are large masses of ice formed by compaction of snow. As glaciers grow and move, y carry with m soils varying in size from fine-grained to huge boulders.

Drift is a general term used for deposits made by glaciers directly or indirectly. Deposits directly made by melting of glaciers are called till. The soil carried by melting water from front of a glacier is termed out-wash.

The A-line, dividing inorganic clay from silt and organic soil has equation: IP=0.73(WL-20).

In earlier stages of World War 2, USCS system was used for air field construction.

Based on HRB system, soil is divided into 7 primary groups, designated as A-1, A-2?A-7.

Since properties of clay soils is less dependent on particle size distrubution(textural classification) and more dependent on size it is best suited for clay soil.

As per Indian standards of group symbols and typical names, G-refers to gravel and C-refers to clay.