- Home
- Conferences
- Conference Proceedings
- Conferences
5th EEGS-ES Meeting
- Conference date: 06 Sep 1999 - 09 Sep 1999
- Location: Budapest, Hungary
- ISBN: 978-94-6282-119-4
- Published: 06 September 1999
81 - 100 of 196 results
-
-
Surface proton magnetic resonance method: What do users get ?
Authors A. Legchenko and A. BeauceThe Surface Proton Magnetic Resonance method (PMR) was proposed by Varian in 1962. It allows a noninvasive detection of subsurface proton-containing liquids and particularly of water. The method is direct, and hence the fact of existence or absence of the PMR signal tells us (also directly) whether there is water in the subsurface or not. Only the amplitude of the signal is to be analysed in this case. Using groundwater as a natural tracer geological anomalies could be detected with PMR. For example, the fault which separates a reef limestone and fractured sandstone areas was crossed by a PMR profile in Cyprus. 5-6 folds variations in the PMR parameters were observed along this profile. The fault position derived from PMR results is in good agreement with geological data.
-
-
-
Block inversion of surface NMR date using simulated annealing
Authors O. Mohnke and U. YaramanciSurface nuclear magnetic resonance (SNMR) is a new non-invasive groundwater-exploration method allowing direct determination of the mobile water content using relaxation amplitudes and of the permeability using decay times of excited hydrogen protons [1, 2]. At present inversion of SNMR data is only one dimensional. The currently available inversion schemes are the programs NUMIS [1], using a smooth regularised least-squares inversion and SAINV [2], using smooth-inversion with simulated annealing (SA), an optimised random search algorithm which is largely independent of the starting model and can escape from local minima [3]. The program SAINV allows to choose between two different types of regularisation, being standard ‘‘smooth’’ (type I) and a more ’’blocky’’ regularisation (type II) [2]. So far the inversion is carried out on the basis of a number of predefined inversion layers that have fixed positions and thicknesses. The inversion scheme introduced in the present paper, based on SA as well, uses block-inversion. In analogy to 1D geoelectrics (VES) the inversion tries to fit the water content of each layer as well as the depth of the layer boundary for a given number of inversion layers, e.g. a 3-layer-case. In block-inversion also a regularisation of type II instead of type I may be used, however, with negligible differences in the results except for very high degrees of regularisation. Inversions have been carried out for data obtained from SNMR measurements at the test site Haldensleben [4]. At this site borehole measurements confirmed a 3-layer-case with a single aquifer between 21.7 and 46 m having a sharp upper boundary due to a very small capillary zone as well as a sharp lower boundary to glacial till and about 30% of mobile water. While the smooth inversion type I yields only a rough estimation of the aquifer location the results of the smooth inversion type II are somewhat more realistic, however, only for a high degree of regularisation. The results of the block inversion are in good agreement with the known sharp boundaries of the aquifer and, in contrast to the smooth inversion, prove to be not influenced by the degree of the applied regularisation. For all inversion results the error of the data fit is generally less than 4 % and the water content is slightly underestimated Block-inversion has some significant advantages. There is no limitation due to the use of predefined inversion layers and therefore it allows a more nature like interpretation especially for aquifers with sharp boundaries. Furthermore it is largely independent of the type and the degree of regularisation and so considerably reduces the ambiguity of the inversion of SNMR data.
-
-
-
Application of combined resistivity and IP multielectrode-measurements for envrionmental investigation
Authors R. Supper, G. Oberlercher and B. JochumIn common IP surveys normally unpolarizeable elektrodes are used to overcome polarisation effects near the electrodes. Moreover, rather high primary currents are necessary as the potential differences due to the IP effect are normally much smaller compared to the voltages observed in common DC – surveys. Using a multielectrode equipment it is not possible to use unpolarizeable electrodes as current injection is done with the same node as the measurements of potential differences. Moreover the use of multicore cable for current injection as well as for potential measurements limits the strength of the primary current. Under favourable conditions the maximum current due to our experience was 1.6 A with the SYSCAL multielectrode system. In addition, the time necessary for both types of measurements is much higher than for resistivity surveys only. On the other hand multielectrode surveys produce much more data along a profile in less time compared to conventional IP procedures allowing a better determined 2d inversion of the data. The above mentioned limitations raise the question if significant measurements of the IP effect are possible at all using a multielectrode equipment and how a two-dimensional combined inversion can be performed properly. A case study demonstrates that in some cases also a multielectrode equipment using steel stakes can produce high quality IP data. Further, sometimes only the combination of IP and Resistivity measurements can solve environmental problems and make correct interpretation of geoelectric data possible. In our surveys we used a STING multielectrode equipment with 100 electrodes for the resistivity survey and the SYSCAL system with a booster for combined measurements of IP and resistivity. Conventional steel stakes were used as electrodes.
-
-
-
Geoelectrical studies to predict and monitor the filtration process on the reservoir at Nuevo Leon, Mexico
Authors A. A. Mousatov, V. A. Shevnin, C. Pola Simuta, N. A. Kousoub and J. A. AndaverdeThe world experience shows that the construction of large reservoirs provokes, as the results of its filling and exploitation, the development of hydrogeological phenomena undesirable or risky for adjacent lands. Filtration processes increase a loss of the reservoir water and, in addition can cause an ascent of the underground water level, a growth of the water mineralization and the salinity of the cultivated lands. That is why the geological and geophysical study is very important on the exploration stage of the hydrotechnical works to predict and monitor the hydrological and hydrogeological changes. El Cuchillo reservoir on San Juan river supplies with the drinking water more than 3.5 million inhabitants of the metropolitan area of Monterrey in Mexican state Nuevo Leon. The capacity of the reservoir restricted by the dam and dike is 1784 Mm3, its maximum depth reaches 35 m. The territory of the reservoir is composed by rocks (intercalating sandstones and shales) of the Eocene age with east dip at the angle 5-100. The sediments were affected by tectonic disjunctions with two principal directions: northeast (NE) and southeast (SE). One fault of the NW direction is located in zone of the dike with horizontal displacement 50-75 m. Two orthogonal fracture systems (N-S and E-W directions) are observed in the sandstone formations. Two types of the underground water exist in the study area: superficial with the salinity until 0.4 g/l related to the flow of San Juan river and brackish one (from 2-3 until 6-7 g/l) obtained from the deeper parts of the Eocene rocks. The rocks were affected by weathering, which reaches the depth of 15 m according to drilling data obtained near the dam and dike. The dam of 4.8 km long has a clay core and a concrete screen. Furthermore bentonite cement was injected to depths of 15 to 25 in its base. The dike of the total length 6 km delimits the reservoir from the North. It is constructed from loose material with the clay core. It has no screen and had only injection of bentonite cement. The geological and geophysical studies were carried out in two stages: during the construction (1992) and filling (1995-1997) El Cuchillo reservoir. During the first stage (1992), the zones of probable filtration were predicted geophysical, geological and geomorphologic data. On the second stage (1995 and 1997), after filling the reservoir, the forecasts were verified and the filtration mechanisms were revealed on the base of repetitive vertical electrical sounding (VES), made with Schlumberger array with AB/2 distances from 1.4 until 100 m with the step 300 - 500 m along profile. Three factors complicate the hydrogeological situation in this zone: the existence of fractures and faults which are perpendicular to the dike; the absence of the waterproof screen in its construction; as well as the decrease of the relief about on 15 m outside of the dike with respect to the ordinary reservoir level. To verify the proposed forecast and to reveal changes of the formation resistivity, which have been provoked by water filtration, VES observations were carried out along the dike in 1995 (2.5 years after the first geoelectrical study and 1.5 years after the beginning of the reservoir filling). Apparent resistivity cross-sections are displayed on fig.1. Changes in the period 1992- 1995 are greater than that in 1995-1997.
-
-
-
Examination of surface-NMR within an integrated geophysical survey in Nauen, Berlin
Authors U. Yaramanci, M. Hertrich and L. GerhardA combined geophysical survey has been conducted at the test site Nauen near Berlin, prospecting a shallow aquifer in fluvial sediments bordered by glacial till. Some of the geophysical results have been reported earlier [1]. Comprehensive investigations of geoelectric sections and depth-soundings as well as georadar profiles were interpreted to describe subsurface conditions. The structure of the dipping glacial till is well recognisable up to a depth of 13 m. The sandy sediments above represent the aquifer with the water table at a depth of about 2 m. The radar velocities and resistivities from Block-Inversion of geoelectric sections have been used to derive hydrological parameters. The aquifer is accordingly determined to have a porosity around 24 % and a water content of 5 % in the vadose zone. At the main profile, five SNMR soundings have been carried out in order to compare the results with those from conventional geophysical methods. Inversion results show mobile water contents of less than 20 % in the first few meters of the vadose zone, increasing rapidly to 30 %. This means an aquifer with an effective porosity of at least 30 % plus adhesive water content. Decreasing water contents below 15-18 m relate to the glacial till which has low permeability and less mobile water. Increasing water contents in larger depth again to values above 30 % indicates another aquifer which is not verified with other methods yet. The decay times within the aquifer are generally about 150-250 ms and correspond in average to medium sands [2]. However, in detail they are somewhat ambiguous.
-
-
-
The water balance of the „Lange Lacke“ (Burgenland/Austria) – A Ggeophysical isotope hydrological, and hydrogeological study
Authors R. Belocky, G. Huebl, W. Papesch, D. Rank and A. RoemerA typical feature of the landscape of the Seewinkel area east of the Neusiedlersee in the province of Burgenland are the “Lacken” – shallow brackish little lakes – which are famous for their rich wildlife and specialised vegetation. Some of them dry up during the warm season. Up to now this behaviour was exclusively attributed to the influence of precipitation and evaporation. This study is focused on the area of the “Lange Lacke” with the goal to investigate the interaction between the groundwater and the water body of the “Lacke”. The hydrogeological conditions of the Seewinkel are characterised by low ground water recharge rates, little ground water movement, small depth of the subsoil water level, and considerable ground water table fluctuation during the year. In the last decades a subsidence of the groundwater level caused by drainage activities was observed. As a first step isotope hydrological investigations have been conducted in order to determine the origin of the water of the Lange Lacke and a possible interaction between ground water and lake water. 3H isotope data show that the origin of the water of the Lange Lacke can solely attributed to the precipitation. On the other hand oxygen isotope data of the surrounding ground water exhibit an enrichment in 18O in areas of ground water flow downstream of the Lange Lacke. This indicates that during times of low ground water table lake water drains off into the ground water.
-
-
-
Electromagnetic reflection method as a nondestructive tool for hydrogeological investigation
Authors F. Bahloul, N. Blindow and M. A. LangeElectromagnetic reflection technique (EMR, ground penetrating radar GPR) is a non-destructive survey device using electromagnetic waves, and it is one of the most promising surface geophysical methods for mapping shallow subsurface structures and the groundwater table. EMR was used to delineate water table topography and depth as well as to locate some structures in the saturated and unsaturated zones. By means of continuous EMR reflection profiles, geological and hydrogeological descriptions of the areas under investigation can be obtained.
-
-
-
Electrical and magnetic investigations of deep aquifers in North Matabeleland, Zimbabwe
Authors T. Dahlin, D. Glatz, N. Persson, P. Gwaze and R. OwenGeophysical investigations are being carried out in North Matabeleland, Zimbabwe, with the aim of finding suitable aquifers to provide the city of Bulawayo with water. In this part of the study an attempt has been made to map the hydrogeology in an area around the railway siding Sawmills. The investigated area is covered by basalt that is mostly weathered on the surface. Outside the Umguza River valley Kalahari Sands overlie the basalt. The basalt rests on the Upper Karoo sandstone, which is the target aquifer. (MacDonald 1970; Stagman 1978)
-
-
-
Seismic, Gravity and geoelectric survey for geothermal research at Lipari Island (Italy)
Authors V. Paoletti, P. P. Bruno, V. Di Fiore, M. Grimaldi, A. Rapolla and N. RobertiIntegrated geoelectric, seismic and micro-gravity surveys were performed in two sites, "San Calogero" and "Fuardo" in the volcanic Island of Lipari (Italy), in order to explore geothermal fluids at low enthalpy and locate the geothermal reservoir of the island. The geophysical methods utilized consist of a seismic reflection profile, five seismic refraction profiles, a microgravity survey and a 2D geoelectric profile in the Fuardo area and a 2D geoelectric profile associated with a microgravity survey in the S. Calogero area. The seismic methods allowed us to locate the main subsurface seismic discontinuities and evaluate their geometrical relationships. The gravity field was used for comparison, while the electric prospecting allowed us to discriminate more conductive areas, within the gravity and seismic model, which could correspond to an increase in fluid circulation in the investigated area.
-
-
-
Distribution of sulfide-rich black shales in Finland and applications for environmental risk evaluation
Authors J. Lerssi, H. Arkimaa, E. Hyvönen, J. Vanne and K. Loukola-RuskeeniemiSulfide-rich black shales have environmental impacts, in some cases even hazardous ones, especially if the bedrock is broken and exposed and the rocks are in contact with surface waters. Release of harmful elements such as arsenic from sulfide-rich black shales have, for example, caused fish kills (Pasava et al., 1995). In the natural environment, the distribution of sulfide-rich black shales in the bedrock is reflected in elevated heavy metal concentrations in till, lake and stream water and sediments, and groundwater (Loukola-Ruskeeniemi et al., 1998).
-
-
-
Paleoclimate investigation based on magnetic and electric properties of sediments in the basin of Lake Ferto (Neusiedlersee)
Authors A. Jelinowskal, M. Menvielle, L. Szarka, P. Tucholkal, B. V. Wesztergom, J. J. Schott and F. KohlbeckLake Ferto (Neusiedlersee) (309 km2) is located on the Austro-Hungarian border south (20 km) of the Danube. It is a shallow (average water depth 50 - 60 cm) water body with large water level fluctuations over the historical period. More than one-third of its surface is now overgrown with uliginal plants. The age of the lake is estimated to be nearly 20 kyr and its origin is related to the simultaneous formation of Hanság and Ferto basins. Large depositions of gravel and sands by Danube and Rába rivers at the end of Pleistocene formed a barrier separating the two basins. During high water periods the two basins were frequently connected. The lake is supplied by local rainfall (78%) and the Vulka and Rákos rivers (20%); groundwater feed represents 2% (Boroviczényi et al 1992). In its natural state lake Ferto has no outlet, its water level is regulated by the discharge through the Hanság channel. Lake Ferto is a part of the Ferto-Hansag (Neusiedler See - Seewinkel) National Park. After some former geophysical experiments (e.g. Fritsch, 1961, Ádám et al 1964, then Kohlbeck et al 1993, 1994) the present study of the area of lake Ferto (Neusiedlersee) is being carried out since 1997 with an aim to understand the past of its basin and environment during the post-glacial period, its actual state and possibly future evolution. Physical properties of sediments measured from the surface (resistivity by geoelectric end electromagnetic methods) and directly from cores are investigated. Preliminary study was realised in 1997 in 6 sites using short (up to 3.5 m) hand-drilled cores and vertical electric soundings. It has shown by comparison of high precision electrical sounding (20 data/decade, millimetre range geometry of electrode positioning for AB distances shorter than 6.4 m; a combination of potential electrodes at the surface and at a depth of 40 cm) with direct measurements of physical parameters (resistivity, water content and low field magnetic susceptibility) on the cores that although very thin sedimentary layers and local inhomogenities cannot be identified by surface measurements, the geoelectric inversion methods allowing smooth layer transitions and stochastic Bayesian method provide a realistic model of the subsurface structure while classical few-layer inversion techniques fail (Kohlbeck et al 1999). Variation of some environmental parameters in sediments were investigated using changes of magnetic minerals which reflect variation in salinity and organic material contents in waters and sediments of the lake and therefore give information about the evolution of hydrogeological system of the lake basin (Jelinowska et al 1999).
-
-
-
Application of electrical methods in mining-quarry natural resources investigations
Authors J. L. Bermejo and L. A. CólligaIn mining industry is very important to quantify and locate the natural resources. These resources help to determine the value of new land to expand or create new quarries and mines. In order to know this, it is very challenging and expensive for the mine developer. This is usually done by excavating pits, drilling wells, and studying the geology of the area. This practice is very expensive when covering wide areas. Geophysics offers the opportunity for nonintrusive characterization covering wide areas in relatively short period of time, thus minimazing the number of wells to characterize a site, and therefore obtaining a great deal of valuable information at a competitive price. The study was conducted at the former urban 28 site of Guadassuar, Valencia, Spain. The area is characterized by orange tree plantations and other agricultural crops. The geology of the area is mainly composed by Quaternary deposits governed by the Jucar River´s dynamics. The first layer was formed by river overflowing, which deposited large amounts of silty loamy deposits during different flooding episodes. A second layer of unconsolidated sediments (sand and gravel) were deposited by the river varying in thickness and location. This is the layer of most interest for mining. The sand and gravel layer is underlain by clay.
-
-
-
Geophysical techniques applied to trees assessment
Authors S. Luigi, G. Alberto and S. L. ValentinaThe problem of trees assessment is increasingly felt either as a life quality problem either as a safety problem within the city management. Many towns in Italy and in Europe have large boulevards and squares with trees, and parks surrounding historical buildings where citizens spend a noticeably part of their free time. These kind of “green belts” and areas are considered an essential part of the quality of life in the cities. At the same time, as these areas can be very crowd, the safety of people as far as the stability of the trees is concerned is a matter of primary importance. In the town of Turin (Italy) the Municipality has committed a research project to the university concerning methods of preventive diagnosis of tree pathologies that could compromise the overall stability of the tree itself. One of the main cause of the collapse of a tree is the decay of the bearing capacity of some of the primary roots (the largest ones). This decay is usually caused by some kind of fytopathology that deteriorate the wood of the root so that it misses both its function of bearing and feeding the tree. This deterioration either changes the physical characteristics of the wood either changes the water content in the peripheral part of the tree immediately above the ground where the root lies. According to these phenomena a detailed survey has been carried out following these two ways: to check if there is a geophysical technique able to find decayed roots in the ground; to check if there is a geophysical technique able to see the change in water content in the peripheral part of the wood immediately above the ground of a decayed root.
-
-
-
The role of geophysical methods at the engineering geological site investigations for construction
Authors I. A. Busel, V. V. Kazaryan and V. G. LobodenkoThe development of technology's principles of integrated engineering geological site investigations to get reliable information for designing buildings and constructions at the optimal expenditures is one of the most important tasks at present. In general true technology's basis of integrated site investigations with continuous technological working cycle includes the following aspects: The analysis of the past investigations' results and (or) information on the adjacent sites, the preliminary working hypothesis of the category of engineering geological condition's complicity, including construction's classification; Geophysical investigations to estimate and reveal the peculiarities of geological structure and hydrogeological conditions, the preliminary scheme of the investigation's sites location; Penetration logging, static and (or) dynamic sounding on a relatively thin net, drilling and sampling of some boreholes, laboratory soil tests; The analysis of the first results, the specification of the condition category's complicity and investigation's scheme in accordance with the designing organization; Penetration logging completion, drilling with purposive sampling specimens of undisrupted and disrupted structure and choosing places of different field works on the basis of spatial variability estimating of soil property according to the penetration logging data, the use of penetration logging between the boreholes for detalization and specification; The analysis of investigation's results, definition of engineering geological and soil calculated elements, the necessary calculated soil characteristics, conclusions, recommendations on conducting further investigations and monitoring.
-
-
-
Inverse problem solution for the dissipation test
By E. ImreExisting dissipation tests differ in the filter position. If the filter is located on the cylindrical shaft 1 D consolidation model is applicable. The paper compares some measured data with the analytical solution of an old and a recently elaborated 1D consolidation models. The model fitting procedure includes the identification of the initial condition and, the coefficient of consolidation. (The usual practice for the inverse problem solution is a “one point” model fitting procedure where the model response is fitted on the t50 measured dissipation time.) The analytical pore water pressure solution of the Soderberg (1962) model:
-
-
-
Geophysical reconnaissance methods for landslides in softrocks - recent developments
Authors R. Arndt, A. Römer and G. SendlhoferIn the past, ground geophysics, cf. MCGUEFFEY et al. (1996) and helicopter-borne systems, SEIBERL et al. (1995), had been successfully applied for reconnaissance work over landslide. Three geotechnical aspects are necessary for the civil engineer to evaluate the stability of landslides in unconsolidated sediments, the (i) 3-D shape with references to shear- and slip surfaces, the (ii) hydrogeological regime and its network within the slip mass, and the (iii) detection of movements and their directional tracking, cf. MCCANN & FORSTER (1990). By conducting typical near surface geophysics, e.g. electromagnetics, DC multi-electrode soundings, induced polarization, GEORADAR, or shallow seismics, sufficient information may be provided for the working geotechnician to proceed with the layout of drilling patterns, to locate trial pits and, and to (re)-design drainage systems.
-
-
-
Application of 2D electrical and seismic tomography techniques for investigating landslide sites
Authors D. Jongmans, D. Demanet, H. Havenith and P. HemroulleProviding a ground image, electrical and seismic tomography tests are increasingly used for investigating landslide sites. After a slope failure, these techniques help to understand the geological structure of the site and to design support or remedial treatment. On the other hand, these non-destructive and relatively low-cost methods also contribute to assess the landslide risk in potential unstable areas. Two case histories are presented in this paper. The first one is an instantaneous rock failure of a few thousands of cubic meters which affected a railway slope, causing a spectacular train derailment without injury (Hemroulle et al., 1999). This slide occurred along a fault plane after heavy rain falls in a rock massif consisting of a succession of shale and sandstone layers which were folded and fractured during the Variscan orogeny. Five seismic tomography profiles were performed perpendicular to the slope with a spacing of a few tens of meters. The aim of this survey was to check the rock quality and to detect potential instability of the slope along the railway. Twenty-four geophones with a natural frequency of 10 Hz were placed along the slope with a spacing ranging between 2 m and 5 m. Waves were generated by hammer drops or explosions. For each profile, a few hundreds of travel times were inverted using the SIRT method (Krajewski et al., 1989).
-
-
-
High-Resolution seismic measurements on an alpine rock glacier
Authors M. Musil, H. Maurer, H. Horstmeyer and F. O. NitscheRock glaciers are an important form of Alpine permafrost. Due to their potential instabilities, possibly caused by global warming, they pose a serious natural hazard for mountainous regions (Haeberli, 1992). To quantify the mechanical behavior of rock glaciers, a multidisciplinary research program consisting of geophysical, geotechnical and glaciological aspects has been initiated. The Muragl rock glacier, located in the eastern Swiss Alps, was chosen as a test site where a number of surface and borehole experiments are to be conducted in order to establish efficient monitoring procedures. Some of the problems that make this investigation difficult are: (i) strong heterogeneities of the rock glacier material, (ii) pronounced topographic variations and (iii) logistic constraints, in an Alpine region at an elevation of 2600 m above sea. Here, we present results from a reconnasaince seismic survey aimed at resolving the subsurface structure, with particular emphasis on delineating the bedrock depth. This information will form the basis for identifying suitable locations for boreholes where various cross-hole tomographic experiments will be conducted.
-
-
-
DC Resistivity and SASW for validation of effeiciency in soil stabilisation prior to road construction
Authors T. Dahlin, M. Svensson and P. LindhThe Öresund link project involves a number of connecting roads and bridges, of which the main road on Swedish ground is Yttre Ringvägen around Malmö. Parts of this road will be built where the bearing capacity of the existing ground is too low. Some of the contractors handle this by lime or cement stabilisation of the uppermost soil. Two of these stabilised sites were investigated with geophysical methods aiming at validating the efficiency of the stabilisation process. DC-resistivity was tested as a method for checking the homogeneity and depth penetration of the stabilisation, and SASW for determining the increase of the stiffness of the subsurface when stabilised.
-
-
-
Geoelectric investigation of flood-control embankments: two case histories
More LessBig floods of late years necessitate the detailed status survey of the river embankments to mark out the segments to be repaired. An efficient tool for this purpose is the geoelectrical geophysical measurement. The inhomogeneities in the dam (fissures, cracks, mudded zones, etc.) are in general threedimensional and small in size, therefore their detection needs lot of measurements and for this reason a quick, efficient measuring system and at least two-, but in the most cases threedimensional interpretation procedures. Purpose of investigation is always the determination of the three-dimensional resistivity distribution of the subsoil with as big horizontal and vertical resolution as possible. We present two examples for the measurements performed using multi-electrode geoelectric measuring system (GRM-30) developed and manufactured in KBFI TRIAS Ltd., Hungary.
-