What is Geotechnical Engineering?

Geotechnical engineering is the branch of civil engineering concerned with the behavior of earth materials. Geotechnical engineering includes:

  • exploring subsurface conditions
  • modeling soil and rock behavior
  • assessing risks posed by site subsurface conditions
  • designing earthworks and structure foundations
  • monitoring site conditions, earthwork and foundation construction.

A typical geotechnical engineering project begins with a site exploration of soil and bedrock below an area of interest to evaluate their engineering properties including how they will interact with a proposed construction project. Explorations typically include:

  • reviewing existing information such as geologic maps, soil surveys and air photographs
  • drilling and sampling the soil and rock
  • conducting tests, both in-situ and in the laboratory, to evaluate the physical properties of the subsurface materials

A geotechnical engineer then analyzes the data and designs the type of foundations, retaining structures, earthworks, and/or pavement subgrades required for the intended man-made structures to be built. Foundations for above-ground structures include shallow and deep foundations. Retaining structures include earth-filled dams and retaining walls. Earthworks include embankments, tunnels, levees, channels, reservoirs, deposition of hazardous waste and sanitary landfills. Pavements include roads, runways, parking areas,  loading docks and aprons. Risk assessment includes hazards such as: earthquakes, landslides, sinkholes, soil liquefaction, debris flows, uncontrolled fill and rock falls.

Soil and rock conditions vary dramatically across the country and even over limited geographic areas.  Design and construction of functional and cost-effective earth supported structures require a thorough understanding of local soil, rock and groundwater conditions. It’s not enough to understand the theories of soil mechanics; knowledge of the local and regional geotechnical conditions is essential.