''Soil mechanics'' is the study of the engineering behavior of soil when it is used either as a construction material or as a foundation material.
This is a relatively young discipline of civil engineering, systematized in its modern form by
Karl Von Terzaghi (1925), who is rightly regarded as the ''Father of Modern Soil Mechanics''. An understanding of the principles of mechanics is essential to the study of soil mechanics.
A knowledge and application of the principles of other basic sciences such as physics and chemistry would also be helpful in the understanding of soil behavior. Further, laboratory and field research have contributed in no small measure to the development of soil mechanics as a discipline.
The term 'Soil' has different meanings in different scientific fields. It has originated from the Latin word Solum. To an agricultural scientist, it means ''the loose material on the earth' crust consisting of disintegrated rock with an admixture of organic matter, which supports plant life''. To a geologist, it means the disintegrated rock material which has not been transported from the place of origin. But, to a civil engineer, the term 'soil' means, and the loose unconsolidated inorganic material on the earth's crust produced by the disintegration of rocks, overlying hard rock with or without organic matter. Foundations of all structures have to be placed on or in such soil, which is the primary reason for our interest as Civil Engineers in its engineering behavior.
Soil may remain at the place of its origin or it may be transported by various natural agencies. It is said to be 'residual' in the earlier situation and 'transported' in the latter. The application of the principles of soil mechanics to the design and construction of foundations for various structures is known as ''Foundation Engineering''. ''Geotechnical Engineering'' may be considered to include both soil mechanics and foundation engineering.
In fact, according to Terzaghi, it is difficult to draw a distinct line of demarcation between soil mechanics and foundation engineering; the latter starts where the former ends.