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 or 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 also 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. Fill, however, can potentially be complex because its nature and behaviour may change during its design life.
To become a competent geotechnical engineer requires postgraduate training and years of practical experience. Because of its diverse nature and complexity, only the basic elements of geotechnical engineering can be taught at undergraduate level. It requires a good understanding of the geology and resulting ground profile, as well as soil and rock behaviour and applied mechanics, combined with empiricism based on well-winnowed experience, as illustrated in Figure 1.
The need to investigate the ground properly and to understand its behaviour is of paramount importance for any construction project. All too often this is not done and the consequences of inadequate site investigation are often extremely expensive. This has been highlighted in the series of documents produced by the Site Investigation Steering Group initiated by the ICE.
Proper site investigation and ground characterisation requires the involvement of experienced geotechnical engineers. Their expertise is also essential to interpret ground behaviour during construction, mining and hydrocarbon extraction and take the necessary actions in response to observations, as well as to react to environmental changes. The assessment of risks and hazards associated with the ground (including those occurring after completion of construction) is also an important responsibility of geotechnical engineers.
The practice of geotechnical engineering often encompasses a wide variety of skills, as illustrated in Figure 2, and consequently involves many types of professionals concerned with the ground, eg civil and structural engineers, tunnelling and mining engineers, geotechnical engineers, engineering geologists, geologists, hydrogeologists, geochemists. As a result there is a very wide geotechnical constituency within the UK comprising a large variety of professionals with different academic backgrounds, training and experience.