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Fourth International Conference on Ground Penetrating Radar
- Conference date: 08 Jun 1992 - 13 Jun 1992
- Location: Rovaniemi, Finland
- Published: 08 June 1992
45 results
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General Ground Penetrating Radar (GPR) concepts
Authors Leon Peters Jr., Michael Poirier and Mark BarnesConcepts involving operational properties of Ground Penetrating Radar are presented. Simple relations for depth of penetration for both the low and high frequency windows are discussed. A relatively new antenna, the Active Isolation Antenna is discussed and sample results obtained using it are presented. Key words (GeoRef Thesaurus, AGI): radar methods, techniques, instruments, attenuation, antennas
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The development of subsurface impusle imaging radar and its application
Authors Zhang Junrong, Liu Fengyu, Wang Hongqi, Chen Meng and He YanSubsurface radar is a new undestroied instrument for searching underground structure and buried object. It transmits electromagnetic wave from ground down to underground and identifies target depth, feature and structure of medium according to the delay and shape of return wave which scattered from interface where dielectric feature of underground medium changes.
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Application of ground penetrating radar to engineering geology in China
Authors Wang Huilian, Li Daxin, Qi Mingsong and Deng ShikunChina began to work with GPR technology in the sixties. At that time, analogue display of the reflected waveform on an oscilloscope was the only option, and all data processing and interpretation had to be done manually. Rapid growth in areas such as the hydropower industry drew attention to a number of complex geotechnical problems. To solve these, China began to introduce GPR systems from abroad. In the early 1980s two types of ground radar systems were popular in China: SIR-8 and Geo-radar I. The China University of Geosciences (CUG) introduced a third system from Canada the year before last. The switch to digital technology allowed great improvement in data interpretation and opened a new phase of engineering geology. CUG has carried out measurements in more than ten regions in Guangxi, Henan, Hubei and Fujian Provinces, and in Guanzhou during the last two years.
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Propagation Deconvolution
More LessIt is well known that at radio frequencies the electrical properties of rocks are frequency dependent (e.g. Cook 1975, Davis & Annan 1989). As a result, the propagation properties of radiowaves, namely velocity and attenuation, are also frequency dependent. In particular, attenuation increases rapidly with increasing frequency. Ground penetrating radar (GPR) operators trade this property with resolution, which also increases with frequency, to determine the optimum antenna centre frequency to use for a particular application. However, it is often ignored or forgotten that pulsed GPR systems transmit broadband signals+H47 covering two octaves of frequencies or more and so the propagation properties vary significantly over the actual transmission bandwith.
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Influence of lithology on radar echoes: analysis with repsect to electromagnetic parameters and rock anisotropy
Authors Sylvia Tillard and Jean-Claude DuboisApplying data processing techniques developed for seismology to radar records has assisted in the graphic presentation of radar images and improved signal analysis. Procedure evaluation was based on radar measurements obtained with nominal frequencies of 50, 100 and 200 MHz (Pulse EKKO III). The measurements involved a set of geological formations covering a wide range of the determinate physical parameters for ground penetrating radar (GPR).
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Application of some seismic data processing methods to ground penetrating radar data
Authors Pekka Maijala and University of OuluDigitally recorded ground penetrating radar (GPR) data resembles reflection seismic data. Both GPR and the reflection seismic method rely on an impulse-type wave signal, whose length in wavelengths varies with the source. Wave packets are sent into the ground by radio-frequency antennas in the case of GPR and by acoustic sources in the case of reflection seismics. The waves are propagated, attenuated and reflected within the studied material.
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Field and laboratory tests on line scatterers
Authors G. Greeuw, J.W. de Feijter and A.F. KathageDetection of pipes, cables and other anomalies in the subsoil is of great importance when a new pipeline is being constructed, especially when a no-dig technique is used. GPR is probably the most suitable technique for the purpose. Quantitive depth information and a distinction between cables and other objects, e.g. old trenches, would provide useful information before the construction starts.
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A challenge: GPR in advance of horizontal drilling
By A.F. KathageThe first horizontal jet-drilling machines were imported to Germany in 1986. Since then they have increasingly been used to lay pipes and cables into the ground without trenching. The main features of the horizontal jet-drilling process are illustrated in Figure 1. First a pilot drilling is done (Fig. la); then the expansion and insertion operation takes place (Fig. Ib). Figure lc shows the drilling principle. A high pressure jet of mud excavates the microtunnel. The antisymmetric shape of the drilling head allows the direction of the drilling path to be controlled. Most horizontal drilling projects take place within a depth range of 2 m. A transmitter built into the drilling head allows precise location of the position of the head.
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Soil taxonomy: a useful guide for the application of ground penetrating radar
Authors Mary E. Collins and University of FloridaGround penetrating-radar (GPR) has been used as a pedologic tool in the United States since the early 1980's. The USDA-Soil Conservation Service routinely uses GPR to update soil surveys in Florida. GPR has also been used for many soil investigations particularly to determine the depth of diagnostic subsurface features that are important in separating soils.
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GPR and dielectric classification of glacial materials
Authors Raimo Sutinen, Pekka Hnninen, Rowland Cromwell and Eija HyvnenNumerical information on unconsolidated geological materials has use in many geotechnical, hydrogeological and forestry appHcations. Glacial geological mapping, is not based on numerical data, however, but on the morphogenetic interpretation of landforms and visual field checking. The average sampling density for basic map (1 : 20000) production in Finland is less than one sample/km2. One of the practical problems in the mapping is that till, the most common glacial sediment type, has no unambiguous numerical definition, and the conventional dso-classification does not necessarily correspond to the genetic classification. There is a need, therefore, for fast techniques for field data collection, which are consistent with the textural characteristics of glacial materials and allow the differentiation of tills.
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The years of applications of ground penetrating radar by the United States department of Agriculture
Authors James A. Doolittle and Loris E. AsmussenThe need for information on soil properties and behavior is growing at an unprecedented rate (Brown, 1985). People are requiring more accurate and site-specific information concerning the properties, composition, and variability of soils and to greater depths than are presently being attained in most modern soil surveys (Miller, 1978). Many non-agricultural uses of soils require information from zones deeper than the limits of modern investigations or to depths where insufficient observations have been made to establish reliable standards. To fulfill the needs for deeper, more intense sampling, and quantitative descriptions of soils, different methods of observing soils are required.
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Recent advances in subsurface radar technology
Authors Thomas J. Fenner and Geophysical Survey SystemsRecent advances in subsurface interface radar technology. Geological Survey ojFinland, Special Paper 16, 13-19,5 figures. The acceptance and use of Subsurface Interface Radar (SIR) has increased dramatically over the last five years. During this period, the number of SIR Systems in use worldwide has nearly quadrupled. New and increasingly diverse applications are putting demands on manufacturers to produce systems that can satisfy the growing range of resolution and penetration requirements. Systems must be more flexible yet simple to use and lower in cost.
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Sub-bottom profiling: a comparison of short-pulse radar and accoustic data
Authors Allan J. Delaney, Paul V. Sellmann and Steven A. ArconeCharacteristics of sediment distribution and layering in freshwater settings is of importance to the dredging industry and for a range of geological, environmental, and engineering studies. The literature on acoustic sub-bottom investigations is extensive. Recent field studies include Scott (personal communication), Larocque (1987), and Klassen and Shilts (1982). Hampton and Anderson (1974) discuss acoustical properties of saturated sediments and include an extensive bibliography. Several studies have used short-pulse radar for observations in lakes and streams (Annan & Davis, 1977; Haeni et al; 1987; Gorin & Haeni, 1989; Truman et al; 1991; Beres & Haeni, 1991; Kovacs, 1991; Delaney et al; 1991). Recently, Sellmann et aI. (in press) reported on the use of a short-pulse radar assembled specifically to profile sub-bottom sediments beneath freshwater bodies.
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Geometry and structure of deltas in large lakes: a ground penetrating radar overview
Authors Harry M. Jol and Derald G. SmithThe limited amount of detailed internal structure of lacustrine (lake) deltas from morphology and widely spaced drill holes has led to the development of simplistic depositional models. To properly understand the geomorphology and internal sedimentology of deltas, it is necessary to determine subsurface sediment facies and their structure. To analyze deltas, other seismic geophysical methods have been hampered by cost, portability and technical limitations (Le. low resolution) and, therefore, has had only limited success. Recent GPR technology has lowered purchase price, maintenance, operating cost, while improved portability, durability and resolution. Published research on the use of GPR in studying subsurface sedimentology and geomorphology is very limited (Ulriksen, 1982; Forgotson et al.1990; Moorman 1990; Moorman et al. 1991; 101 & Smith in press). Our objective is to show and discuss how GPR can be used to better understand subsurface sedimentary structures of different deltas which allows one to improve the construction of depositional models.
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GPR results used to infer depositional processes of coastal spits in large lakes
Authors Derald G. Smith and Harry M. JolThe depositional processes which determine the locations and sedimentation pattern of lacustrine coastal spits is still controversial (Gilbert 1885, 1890; Thompson 1937; Coakley 1976; Nielsen et al. 1988). Most frustrating is the difficulty of recognizing spit deposits in ancient rock successions. The criteria for recognition of spit deposits from drill core and geophysical logs is still an uncertain because the sedimentologic linkage with modern deposits is not well understood. Recent improvements in ground penetrating radar (GPR) offers a means to better understand modern sedimentary structures in coastal spits, which in turn will improve the interpretation of spit deposits in buried rock sequences. Previous research on the use of GPR to infer sedimentary facies and depositional processes to our knowledge is limited only to the pioneering work of Ulriksen (1982). Later work by Forgotson et al. (1990) and Beres and Haeni (1991) provided several guidelines for classifying and interpreting radar signatures. The actual linkage of spit depositional processes with radar facies (reflection patterns) will be the focus of this paper. Our objective is to show how radar facies from two coastal spits can be used to infer depositional processes.
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GPR at a superfund (hazardous wast) site, Vermont, New Hampshire, USA
Authors Doria L. Kutrubes, Keith Dubois and Tom FennerA geophysical investigation was conducted at the Parker Landfill Superfund site in Lyndonville, Vermont. The site is underlain by glacial lacustrine deposits primarily comprised of thinly to thickly bedded silty fine sand. Ground penetrating radar (GPR) was utilized in conjunction with other geophysical methods to characterize the site. Three Industrial Waste Sites, IWSI, IWS2, and IWS3, were identified as potential areas where 55 gallon drums containing solvents had been buried. GPR was used to determine the extent of the fill, characterize subsurface materials, locate buried drums and other objects, and identify buried materials which impede intrusive exploration by borings or test pits. A magnetic survey, which delineated the approximate location of ferro-magnetic materials, and test pits were conducted to assess the accuracy of the GPR interpretation.
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GPR monitoring of DNAPL migration in a sandy auifer
Authors Michael L. Brewster, A. Peter Annan and J. David RedmanChlorinated organic solvents belong to a class of groundwater contaminants commonly referred to as dense non-aqueous phase liquids or DNAPLs. As the acronym implies these liquid are more dense than water and are immiscible in water. DNAPLs also have lower viscosities than water making them highly mobile in the subsurface. In a spill situation DNAPLs will migrate downwards through the watertable as a separate liquid phase. As it moves downward the DNAPL will leave a trail of residual concentration often exceeding 15 % of the pore volume (Feenstra and Cherry, 1988). When a low permeability zone is encountered the DNAPL will tend to pool, until it can build up enough pressure to breakthrough and continue its downward migration path. Pooling may cause considerable lateral spreading of the DNAPL (Keuper and Frind, 1988). Eventually the DNAPL will come to rest, pooling on a horizon which is impermeable to the DNAPL. There it will act as a long term contaminant source as it is slowly dissolved into the passing groundwater. Although DNAPLs are mechanically immiscible in water they will dissolve in concentrations orders of magnitude higher than acceptable drinking water limits.
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Dielectric permittivity monitoring in a sandy aquifer following the controlled release of a DNAPL
Authors J. D. Redman and A.P. AnnanContamination of groundwater by DNAPLs, such as chlorinated solvents, is a serious environmental problem. After an accidental spill into the subsurface, a DNAPL will redistribute itself and form both isolated liquid-phase blobs known as residual, and connected-phase zones known as pools. The behaviour of liquid-phase DNAPLs in a sandy aquifer is controlled principally by variations in hydraulic conductivity(Kueper et aI1989). When groundwater flows through zones containing liquid-phase DNAPL, a small amount of the DNAPL dissolves into the water creating a more extensive plume of dissolved-phase contamination that usually poses the most serious threat to drinking water.
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Integrating ground penetrating radar and electrical resistivity data to delineate groundwater contamination
Authors Alvin K. Benson and Brigham Young UniversityCharacterization of subsurface hazardous materials has become an extremely important application of geophysical and geotechnical techniques. The objectives of subsurface investigations at sites containing hazardous materials include (a) the location of buried materials, (b) the determination of the presence of contaminant plumes and their source(s) and geometry, and (c) the assessment of associated hydrogeologic conditions. The purpose for locating buried hazardous materials is typically for some kind of remedial action, usually involving excavation and safe disposal of the materials with minimal damage to the environment.
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The detection anf mapping of kaolinitic clay by ground probing radar in the cornish granites of southwest England
Authors P.J. Leggo, J.M. Glover and M.R. WajzerThe objective of this study was to assess the potential applications of the Ground Probing Radar (GPR) technique to the china clay industry, chiefly through the property of distinguishing variation in degree of argillisation. China clay deposits principally occur in strongly argillised areas of granitic outcrop, where the granite has been totally replaced by kaolinite. The local variations in intensity of kaolinisation of a potential china clay deposit determine the planning, costing and execution of extraction operations. The most intensely kaolinised, highest grade deposits are very soft, and are able to be extracted by ripping and bulldozing, whereas lower grade, harder material is more efficiently mined by drilling and blasting.
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Application of ground penetrating radar techniques to peatland investigations
Authors Pauli Hnninen and Geological Survey of FinlandA need was perceived in the Geological Survey of Finland in 1983 to improve the rapidity and accuracy of fieldwork methods based on traditional drilling methods. The possibilities offered by the Ground penetrating radar technique were then explored. The first measurements to be carried out by the Geological Survey of Finland, in 1983, employed a Swedish Markradar Ab device, and radar equipment from Helsinki University of Technology was tested in 1984. As the preliminary results were highly promising, the Geological Survey of Finland decided to purchase Ground penetrating radar equipment of its own in 1985. The Subsurface Interface Radar (SIR) by the American manufacturer Geophysical Survey Systems ic. was bought.
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GPR application for the definition of unconformities in a Carrara marble quarry (Massa Carrara - Italy)
More LessThe ground penetrating radar (GPR) method finds a variety of applications in the field of nondestructive surveys and can be successfully employed to map unconformities in ornamental stones quarries. A series of GPR tests was carried out in a marble quarry at Massa Carrara, Italy. The tests allowed the mapping of a series of unconformities due both to fractures and to natural stratifications. At the same time it verified the presence of cavities and other altered zones within the carbonate rock. These macro-structures are quickly profiled by means of medium and low frequency transducers. The detailed definition of small fractures and of unconformities 5 and 6 m below the surface is not yet common practice. The objective of the tests at Massa Carrara was therefore to achieve a highresolution mapping of interfaces only centimetres thick. Correct knowledge of their spacial and geometrical distribution allows better planning of excavation work and minimization of waste.
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Geo-radar development at the Norwegian Geotechnical Institute (NGI)
Authors Tore Lasse By, Fan-Nian Kong and Harald WesterdahlGeo-radar offers high resolution subsurface profiling of features at distances of several metres to several tens of metres in low attenuation material such as sand, gravel, rock and fresh water. The distance may decrease to a few metres in high attenuation materials such as clay. With detection distances like these, geo-radar promises to become an important tool not only for geotechnical investigations, but also for environmental and archaeological investigations.
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Assessment of bauxite reserves using ground penetrating radar
Authors Richard Benson and Lynn YuhrThis paper deals with the Southern Plateau of Jamaica, where a large number of localized bauxite deposits occur on top of limestone. The limestone is highly pitted by dissolution, and is typical of tropical karst areas. Dissolution pits of about 10 to 100 m in diameter and about 3 to 15 m or more in depth are not unusual. For years bauxite reserves had been estimated by drilling on 30 m centers and multiplying the depth obtained by 30 x 30 m. Since the bauxite reserves are relatively small and the top of rock is highly irregular with many karst pits, obtaining an assessment of bauxite reserves by drilling on 30 m centers alone yields inaccurate results.
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GPR measurements for locating underground mine workings at an active open-pit mine
Authors Jeffrey J. Daniels, Dwayne Harris, Roger Roberts and Brian SchillingLocating buried voids, tunnels or other openings in the subsurface is one of the more frequently used applications of Ground Penetrating Radar (GPR) (Daniels, 1988). Buried air-filled voids provide an excellent electric permittivity contrast with any rock type. A host rock that is a relatively homogenous and low-loss provides ideal conditions for detecting and delineating subsurface voids. This nearly ideal GPR environment exists in the syenite porphyry rocks at the Zortman Gold Mine in Zortman Montana.
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GPR systems for roads and bridges
Authors N.S. Parry and J.L. DavisGround Penetrating Radar (GPR) surveys over roads pose some unique challenges when compared to conventional site surveys. Data collection rates are several orders of magnitude greater than conventional GPR surveys. It is not unusual to collect up to 50 linear km of data in one day. A current single-receiver radar system, operating at 50 scans/second, can typically collect 1.5 Mbytes per minute of 8 bit data. However, 8 bit data have insufficient amplitude resolution or signal to noise levels for processing subtle amplitude features. Therefore, data are often digitized at 12- or 16-bit, thereby doubling the data rate to 3 Mbytes per minute. As road radar systems move towards multiple receivers, the problem increases accordingly.
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Non-destructive testing of bridge, highway and airport pavements
Authors Gary J. Weil and EnTech EngineeringIn the inspection of metals and metal-based materials nondestructive testing is an accepted practice. For example, radiographic and ultrasonic techniques are routinely used to identify anomalies in steel pipelines and there are recognized national and international standards on their use. However, in the inspection of concrete the use of nondestructive testing is relatively new. The slow development of nondestructive testing techniques for concrete is because, unlike steel, concrete is highly non-homogeneous composite material. Apart from precast concrete units, which like steel products, are fabricated at a plant, most concrete is produced in ready-mixed plants and delivered to the construction site. The placing, consolidation and curing of concrete takes place in the field using labor which is relatively unskilled. The resulting product is, by its very nature and construction method, highly variable and does not lend itself to testing by nondestructive methods as easily as steel products.
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Highway speed radar for pavement and bridge deck evaluation
More LessTraditional GPR applications have been based on the use of ground-coupled antennas and on manual interpretation of graphical data. This approach is very limiting for highway surveys since much larger areas must be covered at lower unit costs. Therefore, recent radar developments for highways have involved the use of high-resolution air-coupled horn antennas, operations at highway speed, and automated data interpretation software for computing pavement properties.
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Using ground penetration radar technology for pavement evaluations in Texas, USA
Authors Chun-Lok Lau, Tom Scullion and Paul ChanIn recent years several investigators have attempted to use Ground Penetrating Radar (GPR) to detect subsurface problems in pavement systems. Much of the initial work focused on manual interpretation of multiple GPR traces collected along a highway. The traces were often color coded and an expert was needed to locate the problem areas. Sometimes the approach worked, other times poor results were obtained. Highway Departments who evaluated the technology recognized potential, but were often disappointed by the manual interpretation system.
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Use of ground-penetrating radar to investigate refilled scour holes at bridge foundations
Authors F.P. Haeni, Gary Placzek and R.E. TrentScour and removal of sediments and bed materials supporting bridge foundations has caused the collapse of many bridges that crossed streams and rivers (Jarrett and Boyle, 1986; Murillo, 1987). The rate and amount of scour depends on sediment type and transport, depth and velocity of the water, and obstructions to flow (Richardson and Richardson, 1989).
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GPR applications in geotechnical investigations of peat for road survey purposes
Authors Timo Saarenkato, Kari Hietala and Tiina SalmiOne third of the land area in Finland is covered with peat and there are parts of Northern Finland where mires can account as much as 50-70 0,10 of the land area. Even though efforts have been made to construct most of the roads on a hard and bearing soil there are hundreds of kilometers of roads and highways in Finland built over peat bogs, most of them resting on the peat itself.
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Limitations of shallow cross-hole radar investigations
Authors A.F. Siggins and CSIRO Division of GeomechanicsSubsurface radar when used as a geophysical tool is noted for its high spatial resolution. This compensates for the relatively modest ranges usually achieved in geological media. When used in its most popular mode of zero offset surface profiling, the presence of moist soils and near surface conductive clays with attenuations often approaching 50 dB/m, limits the useable range still further. Currently available radar equipment, with performance figures of the order of 120 dB, will be restricted to one or two metres range in these materials.
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Ground penetrating and borehole radar surveys in the Borth salt mine (FRG)
Authors Lucien Halleux, Pascal Feller, Albric Monjoie and Raymond PissartThe salt deposit mined in Borth (FRG) lies in the Zechstein basin, which covers a large part of Central Europe. The mine is located north-east of Duisburg. Although the deposit is over 150 metres thick, only the lower part will be considered here.
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Portable short range subsurface radar
Authors P. Vainikainen, M. Tiuri, V Kontra and E. NyforsHigh-resolution radars with large frequency bandwidth are widely used for the detection and location of subsurface objects (Daniels et at. 1988). The most common wideband signal is the very short pulse (impulse) utilized in short pulse radars (impulseradars). In the ideal case the impulse is a one-sided sinusoidal or gaussian signal (Esselle & Stuchly 1991). In practice the signal contains a few oscillation periods at a particular operation frequency. Frequencies of the order of 100 MHz are used in the measurement of large objects (e.g. ground), where high penetration depth is needed and range resolution of 0.1-1 m is adequate. If range resolution of the order of centimetres is desired, the frequency of the radar must be 1000 MHz or more.
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A shielded loop array antenna for a directional borehole radar
Authors Motoyuki Sato and Tatsuya TanimotoA borehole radar measures the distance of a reflecting object from a receiver. However, conventional omnidirectional borehole radars cannot determine the direction of the object. Some earlier attempts have been made to achieve a directional borehole radar. A cross-loop antenna (Mundry et al. 1983) and a dipole array antenna (Olsson et al. 1989, Sato 1990) have been used for the purpose. These antennas have resonance, which increases the maximum detectable range of the radar. However, the antenna resonance also tends to broaden the received signal, with a reduction in the resolution. This paper introduces a new type of array antenna for a directional borehole radar. The new antenna measures the current induced on the conducting sonde surface by an incoming electromagnetic wave. The antenna is broadband and has good potential for direction finding.
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The results of surface and borehole radar profiling from Permit Area B of the Whiteshell Research Area, Manitoba, Canada
Authors A.L. Holloway, K.M. Stevens and G.S. LodhaAECL Research is assessing plutonic rock for its suitability as a host medium for the disposal of nuelear fuel waste (Dormuth and Nuttall, 1987). One aspect of this research involves identifying and characterizing fracture zones within the rock mass using nondestructive geophysical techniques, ineluding surface and borehole radar reflection surveys.
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2-D synthetic radargrams for archaeological investigation
Authors Dean Goodman and Yasushi NishimuraGround radar is being used in archaeological surveys with considerable success. The structures at excavated sites nevertheless often turn out to be different from those determined from raw radar profiles. The primary reason for these differences is the broadness of the microwave beam transmitted into the ground (see Fig. 1). Many radar antennas have significant response over a l20-degree looking angle, which means imaging of objects both directly below the antenna and off to the side. Although there are processing techniques able to eliminate some of the problems of surveying with a broad beam radar (e.g. migration), these techniques also have drawbacks. The raw, unprocessed radar data normally contain maximum information about the surveyed area. To take advantage of the information content of raw radar records in the interpretation of buried structures, we use forward modelling incorporating matching synthetic radargrams that include the entire directional response of the antenna, together with measured radargrams.
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A radar investigation of pyramids
Authors F-N. Kong, J. Kristiansen and T.L. ByThe Norwegian Geotechnical Institute (NGI) has carried out geo-radar investigations at two archaeological sites, one in Peru and the other in the Canary Islands; in both cases anomalies were found in the pyramids. The frequency sweeping radar described in By et al. 1992, was used in the investigations. Generally speaking, there are two kinds of problems involved in the radar investigation of archaeological sites. The first is a technical problem, Le., how to obtain a clear radar image of subsurface reflectors. The second is how to translate the radar results into results useful to archaeologists. Radar sees all reflectors. Preliminary archaeological knowledge is therefore necessary to be able to sort out the useful information. The second problem may vary from case to case, but the first problem is common to all similar investigations. Our emphasis here is thus on the technical problems.The Norwegian Geotechnical Institute (NGI) has carried out geo-radar investigations at two archaeological sites, one in Peru and the other in the Canary Islands; in both cases anomalies were found in the pyramids. The frequency sweeping radar described in By et al. 1992, was used in the investigations. Generally speaking, there are two kinds of problems involved in the radar investigation of archaeological sites. The first is a technical problem, Le., how to obtain a clear radar image of subsurface reflectors. The second is how to translate the radar results into results useful to archaeologists. Radar sees all reflectors. Preliminary archaeological knowledge is therefore necessary to be able to sort out the useful information. The second problem may vary from case to case, but the first problem is common to all similar investigations. Our emphasis here is thus on the technical problems.
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Ground penetrating radar finds disturbed earth over burials
Authors R.R. Unterberger, Texas A and M UniversityWe are doing GPR research with an OYO Georadar unit, using it in a salt mine in Texas and in a potash mine under the North Sea in England. Rocksalt samples from this Texas mine have been measured to show a tan d of 2 x 10-5 by the U.S. National Institute of Standards and Technology in Boulder, Colorado. This is 5 times less lossy at 200 MHz than teflon, the best man-made dielectric used in coaxial cables. Thus we should expect large GPR ranges in rocksalt, and indeed, we found ranges to 62 m, the maximum time scale (1000 ns) for the Georadar unit. Figure 1 shows an example of a GPR record obtained in the Grand Saline salt mine owned by Morton Salt Company. The time scale is 1000 ns (62 m of depth) the profile length is 51 m and the arrows show two saltair interfaces beneath the floor of an upper-level mining operation. The horizontal line across the whole record is an artifact of the system on the 1000 ns mode only. Figure 2 shows a GPR profile in another salt mine location with three different levels of salt-air interfaces caused by previous mining operations. The Georadar artifact is not present. The time scale is 300 ns, equal to a maximum radar range of 18.6 m in salt; the profile length is almost 100 m.
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Location of human remains with ground-penetrating radar
Authors James S. Mellett and New York UniversityThe use of ground-penetrating radar to probe the upper 2 m ofthe earth's surface (Mellett, 1990) is expanding into a variety of fields as more sophisticated hardware and software permit highresolution applications not possible with earlier GPR equipment. A number of recent publications attest to the success of GPR in the location of human remains, in archaeological studies, and in law enforcement applications (Bevan, 1991; Davenport et al, 1989; Killam, 1990; Mellett, 1990, Mellett and Geismar, 1990, Unterberger, this volume). This paper will describe the use of GPR in historical cemeteries, Potter's fields (burial areas for the indigent), at an American Indian archaeological site, and in a police investigation of a missing person. All surveys discussed here involve localities within the United States.
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Three-dimensional ground probing radar
Authors J.K. van Deen and J.W. de FeijterPulse-echo ground radar has been used for several tens of years to detect underground features and objects. Despite the many smaller improvements and innovations in specific fields of application (Daniels, 1989), no dramatic breakthrough in the method has occurred since the original application. Two factors can be held responsible. In the first place, the different developments have generally been focused on specialized applications and, in line with that, often been published only in specialized and application oriented literature. As a consequence, little cross-fertilization has occurred between different fields of development. In the second place there has been insufficient communication between users and those at the forefront of the technological development. Often the development has taken place either in an instrument oriented organization without much regard for the practical applicability, or in an applications oriented organization lacking the technical and physical background for optimal development.
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Geo-radar in tunneling - The radar tunnel
Authors Harald Westerdahl, Rolf Austvik and Fan-Nian KongBetween 75 and 100 kilometres of tunnel are excavated in Norway each year. In many of these tunnelling projects, the contractor is looking for methods to acquire geological information during the excavation process, enabling him to carry out the project safely and in a cost effective manner. Often the contractor would like to know the geological situation ahead of the tunnel front or the rock thickness and quality above the tunnel.
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Radar imagery and bore hol data - a partnership for identifying a rock instabilty problem
Authors Gerald Rupert, David Summers and Alan HopkinsAs part of the expansion program of the Jefferson National Memorial Expansion Memorial in St. Louis, Missouri, the National Park Service contracted an expansion to the associated museum. This required the floor of an existing room of dimensions 18 m by 25 m be lowered an average of 3 m. In order to maximize seating in the theater, it was also necessary to cut the walls of the excavation as close to flush under the existing footings as could be achieved. The memorial and associated museum are located in the downtown portion of St. Louis and are toured by some two million visitors each year. Consequently, the excavation of the proposed facility was to accomplished without the use of conventional blasting techniques. Figures 1 and 2 illustrate the original ground contour and the required final geometry, respectively. It was estimated that approximately 1200 cubic meters of material needed to be removed. The High Pressure Waterjet Laboratory of the University of Missouri-Rolla proposed to accomplish the work by means of innovative techniques, specifically the use of high pressure water jets and rock splitters designed by the Center. The proposal was accepted, a contract signed and work begun.
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Multistatic Radar System - MRS
Authors Peter Ulriksen and Tekniska Hgskolan I LundSingle channel impulse radars have been in operation for several years for ground penetrating surveys. Usually the radar antenna is kept very close to the surface in order to get an efficient coupling to the ground. This is important when the radio wave absorbtion is strong and the desired penetration is deep. In some cases it has been possible to elevate the antenna and still get a good result. Such applications is the airborne measurement of the equivalent water content in the snow cover and the thickness of freshwater ice. The maximum measured impulse radar penetration we have obtained is 575 m which was obtained in glacial ice in Greenland (Jonsson & Ulriksen 1988). A fundamental problem when operating a ground penetrating radar in the frequency range 80-1000 MHz is that the antennas must be electrically small to be physically manageable. Thus the directivity is always poor. For this reason no results with imaging side looking airborne impulse radars have been presented. Such imagery is very desireable since it would mean the advent of the true color airborne radar image.
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Development of a ground penetrating radar system for object detection and classification
Authors Staffan Abrahamson, Dan Axelsson, Bertil Brusmark, Gunnar Stenstrm and Hans StriforsThe system consists of a radar unit an antenna unit, and a 486 computer. The antenna and radar unit were designed by ERA Technology UK. The radar unit contains a transmitter and receivcer. The width of the transmitted pulse is approximately 1 nanosecond and its frequency content covers the band 200 MHz to 2 GHz. The pulse repetition frequency is 250 kHz and the peak power 50 W. Sampling of the received signal is performed in a repetitive mode, which means that only one sample of a waveform is taken for each transmitted pulse.
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