Geotechnical Engineering Applications

The civil engineer has many diverse important encounters with soil. Apart from the testing and classification of various types of soils in order to determine its physical properties, the knowledge of soil mechanics is particularly helpful in the following problems in civil engineering.

1. Foundation design: Foundation is a very important element of all civil engineering structures. All civil engineering structures like buildings, dams, bridges, retaining walls, walls, canals, tunnels or pillars are founded in or on the surface of the earth. Hence, it is necessary to understand the bearing capacity of the soil, the pattern of stress distribution in the soil beneath the loaded area, the probable settlement of the soil, effect of groundwater and vibration, etc.
2. Pavement design: Pavement can be either flexible or rigid, and its performance depends upon the subsoil on which it rests. The thickness of a pavement and its component parts depends upon certain characteristics of the subsoil, which should be determined before the design is made. On busy pavements, where the intensity of traffic is very high, the effect of repetition of loading and the consequent fatigue failure has to be taken into account.
3. Design of earth-retaining structures and underground structures: The design and construction of underground and earth-retaining structures constitute an important phase of engineering. The examples of underground structures include tunnels, underground buildings, drainage structures and pipelines. A thorough knowledge of geotechnical engineering is essential to design gravity-retaining walls, tunnels, underground buildings, etc. subjected to soil loadings.
4. Design of embankments and excavations: When the surface of the soil structure is not horizontal, the component of gravity tends to move the soil downward, and may disturb the stability of the earth structure. The possibility of seeping groundwater reducing the soil strength while excavating must also be taken into account. Sometimes, it is required to drain the subsoil water to increase the soil strength and to reduce the seepage forces. Deep excavation requires lateral braces and sheet walls to prevent caving in.
5. Design of earth dams: The construction of an earth dam requires a very thorough knowledge of geotechnical engineering. As soil is used as the only construction material in an earth dam, which may be either homogeneous or of composite section, its design involves the determination of the physical properties of soil such as the index properties, such as density, plasticity characteristics and specific gravity, particle size distribution and gradation of the soil, permeability, consolidated and compaction characteristics and shear strength parameters under various drainage conditions. The knowledge of theoretical geotechnical engineering, assuming the soil to be an ideal elastic isotropic and homogeneous material, helps in predicting the behaviour of the soil in the field.

Geotechnical engineers are typically graduates of a four-year civil engineering programme and often hold a masters degree.