Among different types of soils spread over the Indian Peninsula, only six major deposits have been identified, viz., marine deposits, black cotton soils, lateritic soils, alluvial deposits, desert soils and boulder deposits.
1. Marine Deposits
They are generally formed in seawater areas. These deposits cover a narrow belt of tidal flats all along the coast from Porbandar in west to Puri in east. Marine deposits need a pre-treatment before application of any external load.
2. Black Cotton Soils
They are spread over a wide area of 300,000 sq km around Central India and in some parts of Tamil Nadu, Karnataka and Andhra Pradesh. The soil surface is hard in summer and becomes slushy during rainy season. Because of swelling and shrinking nature of the soils, there is a necessity for treatment of the soil. Special foundations are to be adopted in these soils to prevent failure of structures.
3. Lateritic Soils
In tropical regions of high moisture and temperature the lateritic soils are formed. These soils spread over an area of 100,000 sq km around Kerala, Tamil Nadu and West Bengal. Coarse grained soils of this type are called lateritic. The characteristic property of this type of soil is high strength when it is cut and dried in the sun.
4. Alluvial Deposits
The well-known alluvial deposits of India are in the Indo-Gangetic and Brahmaputra flood plains. North of Vindhya Satpura range is also covered with alluvial deposits. Alluvial deposits exhibit alternate layers of coarse and fine soils. The Bengal basin is another important alluvial deposit.
5. Desert Soils
Thar desert in Rajasthan covers most of the area which forms the desert soils of India. These are wind-blown deposits generally present in the form of sand dunes. Scarcity of water is a serious problem in these areas for any construction activity.
6. Boulder Deposits
Rivers flowing in hilly terrains and near foot hills carry large quantities of boulders. Such deposits are often found in the sub-Himalayan regions of Himachal Pradesh and Uttar Pradesh. The properties of these deposits depend on the relative proportions of the boulders and the soil matrix.
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