Engineering geology
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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;
- for wetland and habitat restoration program;
- for 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, tsunami and seiche events);
- 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, hot springs, pyroclastic flows, debris flows, gas emissions, volcanic earthquakes);
- collapsible soils;
- shallow ground water/seepage; and
- other types of geologic constraints.
An engineering geologist or geophysicist may be called upon to evaluate the excavatability (i.e. rippability) of earth (rock) materials to assess the need for pre-blasting during earthwork construction, as well as associated impacts due to vibration during blasting on projects.
Methods and Reporting
The methods used by engineering geologists 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 photographs, remote sensing data, Global Positioning System (GPS) 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 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 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. Engineering geologists provide geologic data on topograpic maps, aerial photographs, geologic maps, Geographic Information System (GIS) maps, or other map bases.