Engineering geology

Engineering Geology is the application of the science of geology to the understanding of geologic phenomena and the engineering solution of geologic hazards and other geologic problems for society. Engineering geologic studies may be performed during the planning, environmental impact analysis, civil engineering design, value engineering and construction phases of public and private works projects, and during post-construction and forensic phases of projects. Engineering geologic studies are performed by a geologist or engineering geologist educated, professionally trained and skilled at the recognition and analysis of geologic hazards and adverse geologic conditions. Their overall objective is the protection of people and property against damage and the solution of geologic problems. Engineering geologic studies may be performed for residential, commercial and industrial developments; for governmental and military installations; for public works such as a power plant, wind turbine, electrical transmission line, sewage treatment plant, water treatment plant, pipeline (aqueduct, sewer, outfall), tunnel, trenchless construction, canal, dam, reservoir, building, railroad, transit, highway, bridge, seismic retrofit, airport and park; for mine and quarry excavations, mine tailing dam, mine reclamation and mine tunneling; wetland and habitat restoration program; coastal engineering, sand replenishment, bluff or sea cliff stability, harbor, pier and waterfront development; for offshore outfall, drilling platform and sub-sea pipeline, sub-sea cable; and for other types of facilities.

Geologic Hazards

Typical geologic hazards evaluated by an engineering geologist include fault rupture on seismically active faults, seismic and earthquake hazards (ground shaking, liquefaction, lurching, lateral spreading, tsunamis and seiches; landslide, mudflow, rock fall and avalanche hazards; unstable slopes and slope stability; erosion; slaking and heave of geologic formations; ground subsidence (such as due to ground water withdrawal, sinkhole collapse, cave collapse, decomposition of organic soils and tectonic movement); volcanic hazards (volcanic eruptions, debris flows, earthquakes and ash falls); collapsible soils; shallow ground water/seepage; and other types of geologic constraints. Engineering geologists, often working in conjunction with a geophysicist, may evaluate conditions such as the excavatability of rock and earth materials (also referred to as rippability) to assess the need for blasting during earthwork construction, as well as associated impacts due to vibration during blasting on projects.

Methods and Reporting

The methods used by an engineering geologist in their studies include geologic field mapping of geologic structures, geologic formations, soil units and hazards; the review of geologic literature, geologic maps, geotechnical reports, engineering plans, environmental reports, stereoscopic aerial photograph, remote sensing data, topographic maps and satellite imagery; the excavation, sampling and logging of earth/rock materials in drilled borings, backhoe test pits and trenches, fault trenching, and bulldozer pits; geophysical surveys (such as seismic refraction traverses, resistivity surveys, ground penetrating radar (GPR) surveys, magnetometer surveys, electromagnetic (EM) surveys, high-resolution sub-bottom profiling, and other geophysical methods); and other methods. The field work is typically culminated in analysis of the data and the preparation of an engineering geologic report, fault hazard report or seismic hazard report, geophysical report, ground water resource report or hydrogeologic report. The engineering geologic report is often prepared in conjunction with a geotechnical engineering report by a geotechnical engineer. The report describes the objectives, methodology, references cited, tests performed, findings and recommendations.

Characteristics of an Engineering Geologist

1. Observation skills: Ability to observe and understand the important physical features, as well as the small, subtle and seemingly unimportant features. Ability to listen and take good notes. 2. Spatial skills: Ability to visualize and draw geologic structures (for example faults, bedding planes, landslides, jointing, etc.) in 3-dimensions. 3. Problem solving: Desire to analyze and solve problems. 4. Scientific curiosity: Desire to know the truth regardless of whether or not it agrees with your original idea about something. 5. Open mind: Ability to withhold your final judgment until all data has been gathered and analyzed. 6. Writing and communications: Ability to write and communicate geologic and engineering ideas to other geologists, engineers, non-specialists and the public. 7. Math and computer skills: Ability to quantify and analyze data and results. 8. Team player: Ability to work in teams and get along with others. 9. Desire to work outdoors: The reason why many students become engineering geologists. 10. Professional Ethics:

Education

Education of Engineering Geologists requires a college degree, such as a Bachelors, Masters in Geology, or Geological Engineering. Course work in Geophysics, Seismology, Hydrogeology, Soil Mechanics, and Geotechnical Engineering is also helpful. A PhD is required for certain university teaching and research positions and certain governmental positions.

By Greg Farrand, CEG, San Diego, California

See also

• Important publications in engineering geology