Cohesionless soils are defined as any free-running type of soil, such as sand or gravel, whose strength depends on friction between particles (measured by the friction angle, Ø).

Permeability is the quality or state of being permeable—able to be penetrated or passed through, especially by a liquid or gas. The verb permeate means to penetrate, pass through, and often become widespread throughout something.

The plasticity index is the size of the range of water contents where the soil exhibits plastic properties. The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL).

Texture differences in soils result from the types of rock that make up a particular area. So non-cohesive soil environments contain little to no clay or fine particles while cohesive soils contain high amounts of clay and fine particles.

The angle of the failure envelope tangent to the Mohr’s circle is denoted as phi or phi’, depending on whether effective stresses are being used. Soils texts usually discuss this concept extensively, as the state of stress and failure criterion concepts are fundamental.

Soil is classified into four types:

• Sandy soil.
• Silt Soil.
• Clay Soil.
• Loamy Soil.

The uniformity coefficient (Cu), curvature coefficient (Cc) and the effective size (D10) are the grading characteristics of the soil. These are the geometric properties of a grading curve that describe a particular type of soil.

Cohesive soils are black cotton soil or fine soils and non – cohesive soils are sand or coarse soils. The cohesive soils are having property of expansive or shrunk. The black cotton soil is serious problem for geotechnical engineers and it is required to be treated before the construction of superstructures.

Black soil is the fertile soil present in India. It is abundantly found in Haryana, Maharashtra and Uttar Pradesh. The black colour of the soil is due to the presence of iron, aluminium and humus. This type of soil is most suitable for the cultivation of grains, vegetables and cotton.

Black cotton soils are inorganic clays of medium to high compressibility and form a major soil group in India. They are characterized by high shrinkage and swelling properties. This Black cotton soils occurs mostly in the central and western parts and covers approximately 20% of the total area of India.

Kharif in dependable rainfall areas (750mm-1250mm/yr) means considerable loss of water through runoff, considerable loss of nutrients, considerable soil erosion and loss of one crop. Black soil have low fertility and are poor in organic matter, nitrogen, available phosphorous and zinc.

Black soil is ideally suited for growing cotton, sugar cane, tobacco, wheat, millets, and oilseed crops. Black soil is to be the best soil type for cotton cultivation. It is also suitable for the production of cereals, oilseeds, citrus fruits and vegetables, tobacco and sugar cane, in addition to cotton.

Under Reamed Piles in Black Cotton Soil It is the safest and economical option to construct the foundation in black cotton soil. In this type of foundations, the building or a house is anchored to the ground at the depth where the ground movement due to changes in moisture content is negligible.

Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash. But they lack in phosphorous, nitrogen and organic matter.

Tropical Chernozems

Because of their high fertility and retentivity of moisture, the black soils are widely used for producing several important crops. Some of the major crops grown on the black soils are cotton, wheat, jowar, linseed, Virginia tobacco, castor, sunflower and millets.

Black soils are mineral soils which have a black surface horizon, enriched with organic carbon that is at least 25 cm deep. A base saturation in the black surface horizons ≥50%.