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3rd EEGS Meeting
- Conference date: 09 Aug 1997 - 11 Aug 1997
- Location: Aarhus, Denmark
- ISBN: 978-94-6282-128-6
- Published: 09 August 1997
101 - 120 of 124 results
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Physical properties of clays and their variation
Authors J. Kulenkampff, C. Flechsig and A. JustIn geophysics, clays are known as materials which considerably influence and alter properties of 'clean' materials. Nevertheless, apart from results from more or less qualitative investigations of day effects, not much is known about the geophysical properties of clays, Forming the barrier for fluid flow in the subsoil, and as a raw material, clays are of increasing economical and social interrest.
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Pyrotechnical survey in Dukla Pass region (NE Slovakia)
More LessThe detecting and liquidation of ammunition in the World War II. battles areas is an important task of engineering geophysics in Slovakia. The paper presented deals with a results of pyrotechnical survey in Dukla pass area (north-eastern Slovakia). In this region, one of the most borrible battle look place at the end of World War II. between German and Soviet-Czechoslovak troops.
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Advances in processing and interpreting magnetic gradiometer data for UXO detection
Authors B. Spurgeon, T. Wilson, O. G. Engels and C. BarthelGeophysical mapping techniques offer a cost-effective solution to clean up and reclaim land contaminated with Un-eXploded Ordnance (UXO). Modem survey techniques involving rapid-sampling gradiometers generate large, high resolution land and marine datasets which need to be properly processed by UXO detection and removal companies to exiract the maximum amount of information possible.
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Location of cavities with geophysical methods: An example of combination of seismic reflection and dipole geoelectrics in the Phlegrean Fields (Southern Italy)
Authors G. Bais, P. Paolo, G. Bruno, E. Carrara, G. Florio, V. Paoletti, N. Roberti and A. RapollaA shallow seismic reflection and a dipole geoelectric surveys were carried out at one site located in the Phlegrean Fields, a volcanic area near Naples (Italy). The target is constituted by a railway tunnel excavated in the "Neapolitan Yellow Tuff', a compact volcanic formation very common in the area. The test has an important practical application, in terms of reduction of the risk associated with the presence of many unknown cavities, dug in the past centuries into the tuff formation to extract material for building. In order to predict the seismic and electric response of the ground-cavity system, 2D syn-thetic wave propagation seismograms and 2D models of the electric response of the ground were produced.
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Mapping of the Cretaceous-Tertiary boundary in the coastal area of Køge Bugt by gamma- and resistivity borehole logging
By O. LarsenIn the coastal region of Køge Bugt Maastrichtian chalk and Danian bryozoan limestone form the prequaternary basement. Maastrichtian chalk forms the prequatemary basement along a section of the coastline, while Danian bryozoan limestone inland appears above the chalk. On a regional scale the Maastrichtian/Danian boundary surface dips westwards.
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An application of combined geophysical methods to the subsurface investigation in old mine activities area
More LessThe risk of further subsidence is still present in areas of old mining activities. For a surface protection it is very important to locate dangerous zones connected with old galleries down to a depth of 100m below the ground level. Activity up to this depth may produce inhomogenous subsidence of the exploited area overburden. Sinkholes are moving slowly up to the surface and when appears near the earth surface they cause sudden collapse of ground.
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A EM geophysical survey over an abandoned coal mining area S Pedro da Cova (North Portugal)
Authors M. S. Matias and F. AlmeidaThe environmental recovery of former mining areas and communities is an economical activity of increasing importance. Among other aspects such activity must include careful planing and an accurate knowledge of the positioning of old mining works. Frequently these works were conducted underground; very often the location of these works is very difficult because of their complexity as well as lack of information. Thus Geophysics can be very helpful both in their location and in the study of their influence on subsurface geological formations.
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A rapid procedure to map overburden thicknesses by using a 3 point electrical sounding method
Authors M. Lajarthe, N. Florsch and P. AndrieuxElectrical soundings are usually used for overburden thickness estimation. Since a classical electrical sounding (herein called «complete sounding») involves at least ten or a dozen points, vast area surveying requires an important amount of time on the field. Here, we study the possibility to reduce an electrical sounding to only three measurements (we call it the «3-point method»), but which provide the same information as would be obtained from a complete sounding.
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Seasonal changes of DC resistivity measurements
By J. AaltonenOne of the most important factors that control the results of DC resistivity measurements is the water content of the ground measured. This is directly governed by the weather situation and the seasonal changes in most geological surroundings. As the water, noticeable, changes character with temperature, this is also a factor to take into account. It is important to know how this natural variation over time, sometimes as short as days, will effect the achieved results. If this natural variation is left without consideration, wrong conclusions may easily be drawn. For monitoring of i.e. leakage situations over a longer period this can be of vital importance.
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Near-surface high resolution geoelectric measurements
More LessIn the problems occurring in environmental and engineering geophysics the inhomogeneities (contamination, fractures, cavities, etc.) are generally small and threedimensional. To detect these, measurements are needed with high resolution in both the horizontal and vertical directions, and it is necessary to measure very efficiently and exactly and to apply multi-dimensional interpretation.
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Identification of poor ground with the aid of DC-resistivity: Results from work on the Öresund bridge connections
Authors C. Bernstone, T. Dahlin, L. Bjulemar and J. BrorssonTogether with large investments in the connecting land infrastructure the construction of the 16 km-long coast to coast Öresund link between Copenhagen and Malmö is now underway. Construction works were initiated in 1994 and the link is scheduled to be inaugurated around the year 2000.
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Assessment of the rock fracturing degree by means of electrical resistivity measurements
Authors H. Marcak and S. Tomecka-SuchonStresses in rock masses, particularly stresses caused by mining activity, produce different kinds of anelastic deformations. In brittle rock, anelastic deformation initiates formation of microcracks or leads to the extension of existing cracks, and may eventually widen the aperture.
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Azimuthal resistivity studies using the offset Wenner sounding technique
Authors K. A. Watson and R. D. BarkerIn recent years, hydrogeologists have employed electrical surveying principles to detect and characterise fracture induced anisotropy, In particular, azimuthal resistivity surveying has been adopted (Leonard-Mayer (1984), Taylor and Fleming (1988), Ritzi and Andolsek (1992), Skjernaa and Jergensen (1993), al Hagrey (1994)) as a technique for determining the principal directions of electrical anisotropy and hence hydraulic conductivity. However, in most recent published examples of the application of azimuthal resistivity surveys, the technique has been poorly applied with resuits almost certainly wrongly interpreted. In this short paper we emphasise some of the pitfails and suggest methods of eliminating serious sources of interpretational ambiguity.
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Comparison of gravity, EM and DC-multi-electrode measurements carried out along two profiles
Authors F. Kohlbeck, A. Marcuello, J. Pous, P. Queralt, R. Supper and T. YelkencyGravimetric, DC-multi-electrode, Electromagnetic EM34 and VLF measurements were carried out on two profiles.
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Solution of engineering problems using combined geophysical tools
Authors L. Hermann, M. Pattantyús-Á, Zs. Prónay and B. NeduczaIt is frequently occurring problem that existing buildings are located at filled up onetime open pit mining area or at recultivated waste deposit sites. Many times the quality of refilling is not appropriate for bearing the bad, moreover, the foundation also has not been built properly. Recent and present damages (subsidences, cracks of houses) call the attention for this problem and for the need of investigation of building foundations using some non destructive geophysical methods.
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Convergent aspects in engineering and environmental geophysics, illustrated by case histories
Authors G. -P. Merkler and D. HannichThe goals, possible solutions and characteristic difficulties, that define convergent aspects in engineering and envfronmental geophysics will be discussed. The two independent branches of applied geophysics, i.e., engineering and environmental geophysies, should both be considered as aids of the geosiences, of the structural engineering and of the environmental research. The key for a succesful application of engineering or environmental geophysical measurements is the conversion of the obtained resuits into terms of structural engineering, geotechnical and hydrogeological language.
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Comparison of terrestrial gamma dose rate maps in border areas - a study for map regional unification
By M. MatolínTerrestrial radiation, the substantial component of the natural radiation environment, is variable with the geological setting of the earth surface. Potassium, uranium decay series, and thorium decay series are fundamental sources of radioactivity of rocks. Radiometric maps, descibing the gamma dose rate or concentration of natura! radioactive elements, are used in environmental studies, estimation of absorbed radiation dose from terrestrial radiation, geological investigations, exploration of raw materials, delimitation of regions of radon risk and they provide a base against which man made contamination can be estimated. A series of radiometric maps has been published (IAEA 1995).
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Teaching geophysics: A "case study
More LessThe University of Milan started the course unit 'Laboratory of Earth Physics" for the ("Laurea") Degree's course in Physics on fail 1995. This is a compulsory course unit for the specialisation in Geophysics and Environmental Physics.
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Acquisition, processing and inversion of magnetic data in archaeological prospecting
Authors J. V. Herwanger, H. R. Maurer, J. Leckebusch and A. G. GreenMagnetic prospecting is a powerful tool for locating and characterizing archaeological features in the shallow subsurface. The introduction of inexpensive optically pumped magnetometers with a resolution of better than 0.1nT facilitates magnetic prospecting for small structures with low susceptibility contrasts. To take full advantage of this new tool, appropriate acquisition strategies and new data analysis techniques are required. For example, applications of various digital signal processing routines allow the locations of archaeological structures to be more precisely determined. Furthermore, 3-D inversions of magnetic data can provide reliable information on the depth extent and shape of the buried objects. These new technologies have been applied in a multidisciplinary study of an archaeological site in northern Switzerland.
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