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1st EEGS Meeting
- Conference date: 25 Sep 1995 - 29 Sep 1995
- Location: Torino, Italy
- ISBN: 978-94-6282-129-3
- Published: 25 September 1995
21 - 40 of 142 results
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The Application of Shear-Wave Reflection Seismics in Shallow Subsurface Investigations
Authors J. Brouwer, V. Nijhof and F. LuitenIn the past decades we have seen the introduction of shallow reflection seismic investigation techniques for application in engineering projects. Although some papers report the use of Shearwave techniques for engineering purposes (e.g. Suyama et al, 1987), the P-wave method has obviously been more attractive. P-wave seismics, however, suffer from a number of fundamental problems that cannot easily be solved: • the P-wave method only indirectly (through AVO) addresses the shear-strength of the soils whereas this parameter is usually of major interest in engineering projects; • within the depth-range of interest (< 50 m) the P-wave method is relatively insensitive to changes in lithology that are significant from an engineering point of view; • within the depth range of interest the P-wave data can be 'blurred' by weathering layer effects (multiples, attenuation, etc.) thus limiting recognition and interpretation of deeper information.
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Shear Wave Velocities of Campanian Tuffs (Southern Italy)
Authors F. M. Guadagno, R. Mele and C. NunziataShear wave velocities of Campanian tuffs were measured both in the laboratory (ultrasonic pulse and resonant column) and in the field (Rayleigh wave spectral analysis). It resulted that it is not sufficient to recognize the tuff basement for computing the site amplification effects, but the dynamic parameters have to be measured because of hardening variation and fracturing.
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Transient Electromagnetic Soundings Applied to Hydrogeology: Some Case Histories in Central Italy
Authors S. Floris, A. Menghini and G. PaganoThese short notes report the results we collected for over four years in geophysical investigations, applied to hydrogeology on various geologic situations in Central Italy, by timedomain electromagnetic method (TDEM). Detailed stratigraphic knowledges, by drillings, allowed a direct comparison with geophysical data.
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High Resolution Seismic Imaging of a Shallow Aquifer
Authors Z. Hajnal, C. D. Hooge and B. SchreinerTwo intersecting high resolution surveys, designed with the support of advanced modelling results, mapped shallow ground-water aquifers. The project was intended to determine optimal data acquisition and processing parameters to image fluids in shallow glacial till deposits. The survey not only imaged the expected target but recognized previously unknown stratigraphic variations within the aquifer. In addition, a study built on geophysical information was initiated to enhance a better understanding of the mechanical properties of till deposits. The test site for the investigation is located north of Saskatoon, Saskatchewan, Canada (Figure 1).
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Applicability of Shallow Cross-Well Tomography in Ground Water Investigations
Authors M. van Kempen, K. Roy-Chowdhurry and W. SpakmanGround water flow is known to be affected by presence of thin, impermeable clay layers. In an area near Ede in Holland, reflection seismics could not be used to detect continuity of such clay layers, due to the presence of a low velocity lid. The applicability of cross-well tomography to this situation was then investigated.
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TDEM Soundings for Locating Aquifers inside the Caldeira of Fogo Active Volcano, Cape Verde Islands
Authors M. Descloitres, M. Ritz and P. MourguesFogo is the highest island of the archipelago of Cape Verde situated 500 km west from Senegal (West Africa). It is an active volcano with a diameter of 27 km and geological outline can be describe as follow: in the beginring, a predominantly effusive vólcanic activity has formed the lower cone overlying a carbonatitic basement.
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Dilution Technique in the Logging Variant: State of the Art
More LessIn an aquifer with confined as well as unconfined groundwater level, the movement of groundwater is usually observed in the direction of the hydraulic gradient. This movement can be described quantitatively by a vector of the filtration velocity Vf with a prevailing horizontal or subhorizontal component, which can be determined reliably in a well penetrating the aquifer.
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Contribution of Geophysical Well-Logging Techniques to Evaluation of Water Resources
More LessCarrying out borehole geophysics measurements applicable to ground-water studies repeatedly in time we can monitore both the dynamics regime of underground water and technical parameters of the borehole. Geophysical logs can be reinterpreted in a post mortem investigation of some geologic or hydrologic factor that was not considered while the hole was being drilled.
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Fluid Logging: the Dilution Technique
Authors D. Chapellier, V. D. Le, A. Re, V. Iliceto and S. MaresRecourse to timed borehole fluid logging after tracer tests (dilution technique) makes it possible to determine, in a mathematical manner, the flow rate and filtration speed up to values of 10-5 m/sec in the case of an induced or natural flow. It also makes possible the continuous recording of variations in these parameters according to the depth. With the help of a tracer, usually NaCI, the variation over time of the electrolytic borehole fluid is studied.
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Maximum Likelihood Object Location Employing Magnetometer and Radar Surface Data
Authors I. Johansen and L. J. GeliusEnvironmental projects concerning site characterization or remediation may also include the problem of locating known objects such as buried drums, unexploaded ordnances, etc.
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Prediction of Rock Temperatures and Water lnflow Zones in Deep Tunnels
Authors A. Busslinger and L. RybachIn deep tunnelling/mining the knowledge of in-site rock temperatures is of paramount importance, e.g. for planning of the underground operabons or for the design of ventilation. During construction large water inflows from karstic or fracture zones can lead to disastrous geotechnical problems. In the following, examples will be presented to predict rock temperatures and water inflow zones.
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Geophysical Imagery of Small-Scale Fracturing
Authors J. C. Gourry and G. GrandjeanInsufficient knowledge of fractured rock represents a common problem in many fields of the Earth Sciences such as the environment, storage, hydrogeology, etc. The study presented here was undertaken in ornamental stone quarries, which offers the main advantage of being able to verify geophysical interpretation after cutting of the working face (meso-scale) or the blocks (micro-scale). As far as the meso-scale is concerned, the aim is to make an inventory of fracturen of an order of approximately 1 m in length, whereas for the micro-scale, it is to identify fractures of up to ten centimetres.
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Advanced GPR Exploration in Karstic Areas
Authors I. Finetti, M. Pipan and G. CandottiMultifold GPR techniques and 3D common offset GPR grids were used for a high resolution geophysical exploration programme in the karstic area surrounding the town of Trieste (Italy). The objective of the programme is the identification of natural cavities and fractures, of interest for applications rangmg from quarry exploitation to civil engineering.
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Use of Geophysical Methods in Old Coal Mine Site Investigations: Some Case Studies
Authors S. C. J. Dawson, K. R. Onions and P. J. JacksonSince the early 1980's, the UK coat industry has declined in size from 200 to its current level of 20 major collieries. Whilst this has meant a reducing demand for Goal exploration geophysics, a new market is emerging: that of site investigations prior to the reclamation of abandoned colliery sites.
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Borehole Radar Survey Applied to a HST Tunnel Investigation
Authors L. Corin, L. Halleux, B. Dethy and T. RichterConsidering the high cost of boreholes, any technique providing additional information on the rockmass around the borehole is extremely useful. Geotechnical tests and geophysical logging techniques are widely used, but the information they provide is only representative of the immediate vicinity of the borehole.
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Earth Resistivity Tomography (ERT) and Cavity Investigation
By F. JacobsTomographic inversion methods appeared in geophysics about ten years ago. In general, they are based upon the principle of transmission of geological bodies by means of elastic or electromagnetic waves, especially in seismology and in engineering geophysics.
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Comparison Between some Borghole Geophysical Methods to Defect Underground Cavities
Authors R. Lagabrielle, P. Cote and N. Lecocq-LeventWhen underground cavities have geometrical characteristics (size and depth) or feature geophysical contrasts which place them beyond the detection limits of surface geophysical methods, borehole geophysics should be used to make sure that they can be detected if they actually exist.
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Single Geophone Profiling (SGRP) Used in the Detection of Lateral Vetocity Changes: Example of Cavity Detection
Authors R. Gauderon, G. Alleman and D. ChapellierThe interest of this new type of research consists in setting up a new method based on the common seismic refraction and reflection methods which are sometimes too expensive and too complex to use. These reasons have led us to develop a new method, the Single Geophone Refraction Profiling (SGRP), which makes possible the rapid and inexpensive interpretation of a chosen site.
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Airborne Geophysics for Geotechnical Applications (Tunnel Location)
Authors W. Seiberl, R. Arndt, A. Romer, R. Supper and G. OberlercherThis papers focusses on the results gained from a hydrogeological study and their geotechnical implications for a tunneling project to be planned in the Inn-Valley (Tyrol).
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