A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Summary Surface geophysical surveys and geophysical well logging are aimed at the detection and location of subsurface geological structures and the determination of certain physical characteristics, which depend on e.g. pore volume, rock structure and the properties of the liquid filling the pores. Geophysical surveys permit the reduction of the drilling programme; geophysical well logging enables the application of fast drilling methods. Geo-electrical surveying is applied in the exploration of large areas for geo-hydrological purposes. Local studies e.g. to determine the extension of a geological formation can also be made economically. The seismic refraction method involves the creation of a shock at the earth’s surface and the determination of the time required for the resulting shock wave to travel known distances to geophones. The travel time of elastic waves depends upon the properties (e.g. density, cementation) of the layers which they pass. Seismic waves may be reflected and refracted at any velocity discontinuity (interface). Geophysical well logging methods, nearly always used in combination, can furnish information regarding lithology, stratigraphy, porosity and water quality in terms of salt content or total hardness. Most electrical methods can only be applied in uncased wells; methods based on the natural or induced radioactivity of rocks yield valuable information as well in cased wells.
Summary Surface geophysical surveys and geophysical well logging are aimed at the detection and location of subsurface geological structures and the determination of certain physical characteristics, which depend on e.g. pore volume, rock structure and the properties of the liquid filling the pores. Geophysical surveys permit the reduction of the drilling programme; geophysical well logging enables the application of fast drilling methods. Geo-electrical surveying is applied in the exploration of large areas for geo-hydrological purposes. Local studies e.g. to determine the extension of a geological formation can also be made economically. The seismic refraction method involves the creation of a shock at the earth’s surface and the determination of the time required for the resulting shock wave to travel known distances to geophones. The travel time of elastic waves depends upon the properties (e.g. density, cementation) of the layers which they pass. Seismic waves may be reflected and refracted at any velocity discontinuity (interface). Geophysical well logging methods, nearly always used in combination, can furnish information regarding lithology, stratigraphy, porosity and water quality in terms of salt content or total hardness. Most electrical methods can only be applied in uncased wells; methods based on the natural or induced radioactivity of rocks yield valuable information as well in cased wells.
Geophysical investigations
Terwey, J. L. (author)
1974
Article (Journal)
English
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