Geotechnics, also called geotechnical engineering, is a branch of civil engineering. It deals with the application of scientific methods and engineering principles to the acquisition, interpretation and use of knowledge of the materials of the Earth's crust and the materials of the earth for the solution of engineering problems and the design of engineering works. It is the applied science of predicting the behavior of the Earth, its various materials and processes to make the Earth more suitable for human activities and development.[1]​.

Geotechnics covers the fields of soil mechanics and rock mechanics, and aspects of geophysics, hydrology, geology and other related sciences. Geotechnics is mainly practiced by civil engineers specializing in geotechnics.

Examples of the application of geotechnics include: predicting, preventing, or mitigating damage caused by natural hazards such as avalanches, mudflows, landslides, rockfalls, sinkholes, and volcanic eruptions; the application of soil, rock and groundwater mechanics to the design and intended performance of earth structures, such as dams (Dam (Hydraulic)); the design and performance prediction of foundations of bridges, buildings and other artificial structures in terms of the underlying soil and/or rock, flood control and prediction.

The geotechnical properties of a soil, such as its grain size distribution, plasticity, compressibility and shear strength, can be evaluated by appropriate laboratory tests. Furthermore, emphasis has recently been placed on the in situ determination of the resistance and deformation properties of the soil, since this process avoids altering the samples during field exploration.[2]​.

Particle size distribution.

The particle size distribution of a coarse-grained soil is generally determined by mesh size analysis. For a fine-grained soil, the grain size distribution can be obtained through hydrometer analysis.[3]​.

Floor size limits.

The table presents the size limits recommended by the American Association of State Highway and Transportation Officials (AASHTO) and the Unified Soil Classification systems (Corps of Engineers, Department of the Army and Bureau of Reclamation).[4]​.

Weight-volume relationships.

In nature soils are three-phase systems consisting of solid soil particles, water and air (or gas). To develop weight-volume relationships for a solid, the three phases can be separated. Based on this separation, volume relationships can be defined.

The void ratio, e, is the ratio of the volume of voids to the volume of solids of a soil in a given soil mass, or.

[5]​.