Geotechnical engineering: Difference between revisions

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Geotechnical engineers and engineering geologists perform geotechnical investigations to obtain information on the [[Physical property|physical properties]] of soil and rock underlying and adjacent to a site to design earthworks and foundations for proposed structures and for the repair of distress to earthworks and structures caused by subsurface conditions. Geotechnical investigations involve surface and subsurface exploration of a site, often including subsurface sampling and laboratory testing of retrieved soil samples. Sometimes, [[Exploration geophysics|geophysical methods]] are also used to obtain data, which include measurement of [[seismic waves]] (pressure, shear, and [[Rayleigh waves]]), surface-wave methods and downhole methods, and [[Prospecting|electromagnetic surveys]] (magnetometer, [[Electrical resistivity and conductivity|resistivity]], and [[ground-penetrating radar]]). [[Electrical resistivity tomography|Electrical tomography]] can be used to survey soil and rock properties and existing underground infrastructure in construction projects.<ref>Deep Scan Tech (2023): [https://www.deepscantech.com/news/deep-scan-tech-uncovers-hidden-structures-at-the-site-of-denmarks-tallest-building.html Deep Scan Tech uncovers hidden structures at the site of Denmark's tallest building].</ref>

Surface [[exploration]] can include on-foot surveys, [[geologicgeological map]]ping, [[Exploration geophysics|geophysical methods]], and [[photogrammetry]]. GeologicGeological mapping and interpretation of [[geomorphology]] are typically completed in consultation with a [[geologist]] or [[engineering geologist]]. Subsurface exploration usually involves in-situ testing (for example, the [[standard penetration test]] and [[cone penetration test]]). The digging of test pits and trenching (particularly for locating [[Fault (geology)|faults]] and [[landslide|slide planes]]) may also be used to learn about soil conditions at depth. Large-diameter borings are rarely used due to safety concerns and expense. Still, they are sometimes used to allow a geologist or engineer to be lowered into the borehole for direct visual and manual examination of the soil and rock [[stratigraphy]].

Various [[Geotechnical investigation#Soil sampling|soil samplers]] exist to meet the needs of different engineering projects. The [[standard penetration test]], which uses a thick-walled split spoon sampler, is the most common way to collect disturbed samples. Piston samplers, employing a thin-walled tube, are most commonly used to collect less disturbed samples. More advanced methods, such as the Sherbrooke block sampler, are superior but expensive. Coring frozen ground provides high-quality undisturbed samples from ground conditions, such as fill, sand, [[moraine]], and rock fracture zones.<ref name="Coring frozen ground">{{cite web | url=https://www.geofrost.no/en/ground-investigations/#Undisturbed%20samples | title=Geofrost Coring | publisher=GEOFROST | access-date=20 November 2020}}</ref>