The soil deposits in India can be classified into these five types broadly :
- Alluvial Deposits –
Alluvial deposits are usually seen in North India. Mainly the flood plains of Ganga and Brahmaputra River. The depth of layers varies from few meters to one hundred meters. You can also fine alluvial deposits in peninsular India.
In Alluvial soil, there are alternating layers of silt, sand, and clay. The existence of these layers is a distinct characteristic of alluvial soil. The thickness of the layers depends upon local terrain and nature of floods which cause deposition. These deposits are low in density and prone to liquefaction in earthquake prone areas.
- Black Cotton Soil –
This soil has high plasticity. Mostly central India and a portion of south India is covered by BC Soil. This soil is the residual deposit of basalt or trap rocks. This soil type is suitable to grow cotton and hence it is termed as Black cotton soil. Soil contains mineral montmorillonite in a considerable quantity.
The main property of this soil is it expands with the presence of moisture and contracts in the absence of moisture. So, the shrinkage properties are high. Due to this property, this soil is found to be most troublesome from engineering considerations. The bearing strength of BC soil is very low which makes it more dangerous for construction.
- Lateritic Soils –
This type of soil is formed by decomposition of rock, removal of bases and silica, Accumulation of iron oxide and aluminum oxide. The red color of soil is due to iron oxide. This soil exists in central, southern and eastern India. This type of soil is so soft that it can be cut with a chisel when wet.
With time it gets hardened. The plasticity of Lateritic soil is reduced as we go deep and towards parent rock. The soils containing Iron Oxide have high specific gravity.
- Desert Soil –
Fine gradation soil found in large part of Rajasthan and adjoining states. These sand deposits are called as sand dunes. In this area arid conditions exists and the rainfall is minimum. This type of sand is granular.
Gradation is uniform and in classification it falls under Sand category. It has high porosity and very less plasticity. As the sand has no cohession, to increse the strength densification is required.
- Marine Deposits –
Marine soil deposits are mostly found on the narrow belt near coast i. e. The south west coast of India. There are thick layers of sand above the layers of marine sand. These marine deposits have very fine particles can be classified as clay.
Soil is also soft and has high plasticity. It has low strength and highly compressibe. Being Marine deposite, it contains organic matter.
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