SOIL, SOIL MECHANISM & SOIL INTRODUCTION

SOIL, SOIL MECHANICS AND SOIL ENGINEERING:

The definition of soil given by agriculturist or a geologist is different from the one given by a civil engineer. To an agriculturist, soil means the top layer of earth which is responsible for supporting plant life. Even to a geologist, soil is the thin outer layer of loose sediments within which plants roots are present. A geologist refers to the rest of earth's crust as rock, irrespective of how strong or weak the bonding forces of the sediments are.

For a civil engineer, soil mean all naturally occurring, relatively unconsolidated earth material- organic or inorganic in character- that lies above the bedrock. According to Terzaghi, soil can be broken down into their constituent particles relatively easily, such as by agitation in water. On the other hand, rocks are an agglomeration of mineral particles which are bonded together by strong molecular forces. Often, this distinction between soils and rocks is not clear-cut. Many a hard soil can also be termed as soft rock or vice versa. Rocks can be the massive bedrock or large fragments of gravel, pebbles, etc., within a soil.

Soil mechanism is the branch of civil engineering that concerns the application of the principles of mechanics, hydraulics and to a smaller extent, chemistry, to engineering problems related to soil. It includes the study of soil behaviour.

Soil engineering is a broader term which includes not only soil mechanics but also geology, structural engineering, soil dynamics and many other which are often essential to obtain practical solutions to problem of soil. 

Problems related to soil:

• Foundation design and construction.
• Pavement design.
• Design of underground earth retaining structure.
• Design of embankments and excavation.
• Design of earth dams.

Process of soil formation:

Soils are formed by weathering of rocks and minerals at or near the earth surface by either

• Physical disintegration

1. Temperature changes
2. Abrasion
3. Wedging action of Ice
4. Spreading of Roots of Plants

• Chemical dicomposition

1. Hydration
2. Carbonation
3. Oxidation
4. Leaching
5. Hydrolysis

Types:

If the products of rock weathering are still located at the place where they originated, they are called residual soil. Any soil that has been transported from its place of origin by wind, water, ice or any other agency and has been redeposited, is called a transported soil. Residual soil are not as common as transported soil.

Regional soil deposits of INDIA: