The subject of geotechnics can be considered as a set of applied fields of soil mechanics and rock mechanics, derived from the word Geo. At the same time, it should be noted that in many cases the terms soil mechanics and geotechnics are still used interchangeably, and it is pointed out that the term geotechnics (as a technology) and the term soil mechanics (as A branch of knowledge) do not necessarily convey a synonymous and completely identical concept; However, they have a lot in common and in many cases they are in place. For example, the first and most prestigious journal on soil engineering issues, published since 1948. It started in the UK and is still going on, called the International Journal of Geotechnique. In addition to these explanations and in completing them, it is appropriate to translate the definition given in the introduction to the book "Geotechnical Engineering" by B. M. Das (1993).It has beed said:

"Geotechnical engineering is a sub-branch of civil engineering that studies the engineering properties of natural surface materials and its role is to apply the principles of soil mechanics and rock mechanics in the design of projects such as foundations, retaining structures and earthen structures."

due to the fact that the materials studied in geotechnical knowledge are terrestrial (and natural) materials etc soil and rock, these studies and studies are divided into basic sections, each of which contains specific theories and tools. These sections are described under such headings as soil or rock physics, soil or rock mechanics, soil or rock dynamics, laboratory tests for soil or rock, field experiments, and related tools, and have developed dramatically in recent years. Has been found and in parallel, several books and article have been published under the same names.

On the other hand, due to the natural nature of soil and rock materials, which are often (almost always) "in place", geotechnical studies are closely related to the topic of "Engineering Geology" and therefore in executive projects - especially Projects that take place over a large area (such as dam projects) or in a long direction (such as roads and tunnels) - the subject of engineering geology forms the primary foundation for studies and decisions, and so on. Reason: In some cases, there is a necessary interaction between engineering geology, soil mechanics, rock mechanics, and geotechnic. On the other hand, due to the nature of soil and rock materials, which are often (almost always) "in place", geotechnical studies are closely related to the topic of "Engineering Geology" and therefore in executive projects - especially Projects that take place over a large area (such as dam projects) or in a long direction (such as roads and tunnels) - the subject of engineering geology forms the primary foundation for studies and decisions, and so on. Reason: In some cases, there is a necessary interaction between engineering geology, soil mechanics, rock mechanics, and geotechnic.

Geotechnical knowledge field of application:

  Any development that takes place on the land surface (as well as below the water surface), its support is a bed of rock or soil and, therefore, inevitably related to their properties. Residential and office buildings, silos, towers, roads, stadiums, airports, power plants, road and railway tunnels and underpasses, subways and parking lots, bridges, warehouses, tunnels and water supply canals, Dams, refineries, and refineries, etc., are all somehow supported by a bed or soil or rock. How accurately and what properties and characteristics of soil or rock should be studied in each of these projects depends on several factors, the most important of which are: the strength or resistance of the project site against forces. The internal influences of the place, such as the presence of water, fractures, voids, inhomogeneities , and inequalities, the economic importance and the level of safety necessary to maintain the safety and security of users, the useful life of the project and how Durability of the properties of that environment in relation to time, factors affecting the sustainability or damage to the project and its infrastructure and some other factors.