Geotechnical engineering is a branch of civil engineering which deals with the behavior of earth materials. Professionals in this field examine the soil and rock layers that make up the earth in order to determine their physical and chemical properties. Using this information, they design foundations and earthworks structures for buildings, roads, and many other types of projects.
The goal of geotechnical engineering is to design soil stabilization systems that keep people safe. This may include ensuring a building will remain standing on unstable soil, or preventing earthquakes and landslides from impacting major roads. Geotechnical engineers may also work on projects that deal with underwater soils, such as those affecting marinas or offshore platforms.
The geotechnical design process starts with a subsurface investigation, where soil samples are taken using test pits or bores. Geotechnical engineers will then examine the properties of the soil, including its stability, the presence of air or rock pockets, and the chemical makeup of the earth. This investigation allows them to determine the environmental impact of disturbing the soil, as well as what steps should be taken to prepare the site for construction.
Once subsurface work is complete, a geotechnical engineering professional can use the results of this research to design stable footings and foundations. These structures are made from steel, concrete, or masonry, and are placed underground to support and distribute the weight of the building. To create accurate designs, engineers calculate the load of both building materials and the people inside. These systems must also allow the building to settle over time, and accommodate ground movements and impacts from weather. Typically, the more unstable the soil at a project site is, the larger and more complex the foundation system will be.
Geotechnical engineers also design earth support structures to accommodate roads, tunnels, dams, and other projects. Whenever the earth is moved or excavated, support systems must be used to keep the remaining earth from caving in or becoming unstable. Earthworks systems may include concrete or steel retaining walls, which physically hold the soil back and prevent collapsing or cave-ins. Another popular methods uses tie-backs or piles, which consist of steel pins that tie loose sections of earth to more stable ones. Temporary earthworks structures may be also be used to protect workers during excavation and underground work.
To work in the geotechnical engineering field, one must usually obtain both an undergraduate and professional level engineering degree. While some universities may offer specialized geotechnical programs, most students will find only general civil engineering programs. Upon graduation, candidates may find work in the field, working under the supervision of a licensed engineer. To perform geotechnical design work without supervision, one must secure a Professional Engineer (P.E.) license in civil or geotechnical engineering. To obtain this license, the engineer must have several years of relevant work experience, then pass a state-administered engineering exam.