D.P. Giles, in Encyclopedia of Geology, 2005
Geotechnical engineering has recently (1999) been formally defined in a Memorandum of Understanding on the proposed unification of the British Institution of Civil Engineers Ground Board and the British Geotechnical Society. Appendix A of that memorandum, establishing the British Geotechnical Association, sets out the following definition:
Geotechnical engineering is the application of the sciences of soil mechanics and rock mechanics, engineering geology and other related disciplines to civil engineering construction, the extractive industries and the preservation and enhancement of the environment.
Geotechnical engineering plays a key role in all civil engineering projects, since all construction is built on or in the ground. In addition, it forms an important part of extractive industries, such as open cast and underground mining and hydrocarbon extraction, and is essential in evaluating natural hazards such as earthquakes and landslides.
The use of natural soil and rock makes geotechnical engineering different from many other branches of engineering: whereas most engineers specify the materials they use, the geotechnical engineer must use the material existing in the ground and in general cannot control its properties.
In most cases the complexity of the geology means that the geotechnical engineer is dealing with particularly complicated and variable materials; their mechanical properties usually vary with time and are critically dependent on the water pressures in the ground, which can often change.
The geotechnical engineer does sometimes have the opportunity to specify certain properties or treatment of soils, rocks and other materials used in construction.
Geotechnics can thus be primarily considered as the science of the engineering properties and behaviour of rocks and soils. Geotechnical engineering can be considered as the professional practice and implementation of that knowledge contributing principally to the design of engineered structures in and on the ground (Figure 1).
Geotechnical engineering is the systematic application of techniques which allows construction on, in, or with geomaterials, i.e., soil and rock. Every civil engineering structure and construction is related to soil in some way, and subsequently, its design will depend on properties of the soil or rock. Geotechnical operations are of importance with respect to soil sampling, investigating geomaterials properties, controlling groundwater level and flow as well as environmental and hydrological interactions. Foundation engineering, excavations and supporting ground structures, underground structures, dams, natural or artificial fills, roads and airports, subgrades and ground structures, and slope stability assessments are examples of geotechnical engineering applications in practice.
Despite notable progress in geotechnical engineering, many solutions are still approximate, which is mainly due to the natural inherent inhomogeneity of soils and dominant environmental conditions. Additionally, soils are more sensitive to local environmental conditions compared to other prefabricated building materials such as steel or concrete. Consequently, it would be necessary to have comprehensive understanding of natural soil deposits, environment interactions, and response to local conditions to allow more accurate prediction of geomaterials engineering performance and behavior in projects.
Geotechnical engineering activities are a part of a team effort involving other disciplines including geology, structural engineering, construction management, hydraulics, earthquake and transportation engineers, and other pertinent branches. The final design of any project reflects a collaboration of these professions.