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13th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 20 Feb 2000 - 24 Feb 2000
- Location: Arlington, Virginia, USA
- Published: 20 February 2000
41 - 60 of 140 results
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Identifying Potential Collapse Zones Under Highways
Authors Paul J. Wolfe, Benjamin H. Richard, Ernest C. Hauser and James D. HicksSubsidence of abandoned coal mines is a problem in many places, e.g., the opening of a large hole in Interstate 70 in eastern Ohio. With the support of the Ohio DOT we are looking for geophysical methods to economically determine locations where potential coliapse may threaten highways. The goal is a reconnaissance survey method to identify areas that need detailed investigation. We have completed the first phase study at a site with collapsing coal mines. The techniques tested were:
1. P-wave refraction,
2. S-wave refraction,
3. Gravity,
4. 2D resistivity,
5. Ground penetrating radar (GPR),
6. Surface waves
a) spectral analysis (SASW)
b) profiling.
The data were acquired along a 480 ft (146 m) section of Ohio Route 32 in Jackson County. The data were interpreted and several test borings were made to verify the geophysical results. We found that P-wave refraction, 2D resistivity, and surface wave profiling provided the best correlation with the boring results. S-wave refraction was useful. Gravity and SASW did not have adequate horizontal resolution to be worthwhile additions to the interpretation. GPR signals were too attenuated by the clay-rich soil.
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Locating Subsurface Voids In Karst: A Comparison Of Multi-Electrode Earth Resistivity Testing And Gravity Testing
Authors M.J.S. Roth, J.E. Nyquist and B. GuzasIn this paper, the authors compare microgravity, multi-electrode resistivity, and boring data in
karst at a site in eastern Pennsylvania. The hypothesis being tested is that a comparison of
resistivity results and gravity results (both non-intrusive tests) can be used to provide information
concerning the location of voids at a site where the depth to bedrock is highly variable. The
authors conclude that while either resistivity or gravity can be used to predict bedrock depths,
fluctuations observed in the gravity data in areas without voids are of a similar magnitude to
those observed in areas with voids. Therefore, void locations cannot be reliably identified using
a combination of these two test methods.
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4-D Microgravity: A Method For Cave Detection And Monitoring
Authors M. Rybakov, V. Goldshmidt and L. Fleischer and Y. RotsteinSinkhole hazard is becoming an apparent problem in the Dead Sea area and a severe obstacle in future land use planning in the region. A feasibility study for the use of microgravity for cave
detection (3D) and monitoring the collapse development over time (4D) has been completed in the area. The microgravity was used with the assumption that it could detect subsurface cavities, regardless of their shape or filling material, as long as there is sufficient density contrast. 3-D modeling indicated that subsurface sinkholes could be detected at a depth of up to several times the diameter of the subsurface cavity. Detection was carried out microgravity mapping, using a 5x5-meter grid, with accurate geodetic control in real time. Accuracy is estimated to be in the range of 0.01 to 0.02 mGa1. The microgravity maps indicate the presence of large subsurface cavities underlying the areas where several open sinkholes are observed, suggesting that additional sinkhole development can be expected. Tracing the development of sinkholes, before their roof collapses and they become an apparent surface feature, was attempted by repeated measurements along a road, where such sinkholes were observed in the past. This 4D microgravity monitoring experiment lasted 4 months and revealed apparent changes in the gravity field in the order of 0.03 mGa1, which are thought to be associated with changes in the size of the cavity, probably as a result of roof collapse. The results suggest that microgravity can be an effective technique, not only for detecting and delineating subsurface cavities, but also in monitoring their development in time and prediction of collapse hazards.
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A Geophysical Investigation Of A Sugar Cane Plantation, St. Croix, U.S. Virgin Islands: Using Multiple Techniques To Assess A Complex Industrial Site
Authors Len Mankowski, Seth Lemke, Susan Martin, David Hayes, Pat Martin, Charles Young and Jimmy DiehlAn archaeological geophysical investigation was conducted at Estate Whim Plantation Museum
(Whim) February 25 to March 5, 1999. Whim is the only preserved and publicly open site
on St. Croix that offers a guided interpretation of lifeways and processes associated with the island’s
historical role in the sugar trade from the 1 sth to the early 20th centuries. During its operation
Whim was not only a plantation, but also housed a factory for on-site cane processing. The plantation
and factory were worked by slaves until 1848. While many features remain standing, the
original slave village and factory have been buried up to a depth of three meters.
Three geophysical techniques were used to assess potential excavation sites. These were:
Magnetics (Total field), DC resistivity (square array); and ground penetrating radar (GPR).
Ambient noise levels were high due to soil inhomogeneity. The industrial site also contained
a complex firebrick foundation with an extremely strong magnetic and resistivity signature which
masked more subtle structural features. Low amplitude boundary features were revealed by converting
measured resistances to transverse anisotropy plots. The magnetics data required more intensive
processing. Removal of an upward continued dataset served as a high pass filter. This was
reduced to the pole and converted to pseudogravity sections to perform a horizontal derivative.
The GPR survey was performed using 200 MHz antennas; lower than those typically used at archaeological
sites. Removal of the average trace from a line and band-pass filtering, indicated numerous
shallow diffraction events and discontinuous surfaces not apparent in the raw data.
The data from all three techniques were combined to produce maps to assess the site. Processing
did not appear to introduce significant artifacts. Interpretation of anomalies (e.g. foundations,
firebrick, etc.) proceeded with much greater confidence due to multiple technique results.
Several sites within the factory were chosen for excavation in August of 1999, based in-part on the
geophysical results. Compared to excavation results, transverse anisotropy and magnetics had
been reliable indicators of potential excavation sites. GPR’s service as an interpretive tool was
heightened after excavation.
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Development Of The Initial Physico-Archaeological Model Of The Nahal Zehora Site (Central Israel) Using Modern Magnetic Data Interpretation
Authors Lev Eppelbaum, Sonya Itkis and Avi GopherMagnetic survey provides a ground plan of cultural remains before archaeological
excavations. In special cases it may even be used instead of excavations for understanding
the cultural environment in order to avoid the site destruction. For the first time a detail
magnetic survey was conducted in Israel at sufficiently large (60 x 80 m) area. This area
borders south the known Prehistoric Nahal Zehora site partially excavated during the
many year’s archaeological investigations. The total magnetic field was observed with a
step between points of 0.5 m, distance between investigated profiles was 10 m and the
total number of the observed points was about 5,200. Magnetic susceptibility of soil
was measured on 180 samples. At the studied area has been recognized 12 anomalies
apparently reflecting three types of archaeological remains: (1) local high-intensive
anomalies due iron-containing (we do not exclude an agricultural origin of these objects)
or fired structures, (2) negative anomalies caused by the ancient constructions made
from a non-magnetic material (limestone), (3) positive anomalies due to accumulation
of the ancient human habitation (repeated heating of the soil as well as accumulation of
organic debris, etc.). In parallel with the conventional procedures (removing temporal
magnetic variations, gridding magnetic data and qualitative interpretation) here were
applied improved methods for inverse problem solution and 3-D modeling of magnetic
field. The developed initial physico-archaeological model of the site shows ranging studied
targets, their exact location and calculated depth of the upper edge (for the model of thin
bed) and position of the center of anomalous body (for the model of horizontal circular
cylinder).
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Combined Shallow Seismic And Hydrogeological Investigation Of The Ancient Hierakonpolis Site In Southern Egypt
Authors S.S. Alexander, S.M. Brown, R.R. Parizek and D.P. GoldThe ancient temple-town of Hierakonpolis, and its surrounding area near Edfu in southern Egypt
has been investigated using shallow seismic observations and hydrologic field measurements.
This temple-town, now buried in Nile silts beneath a shallow water table produced by
surrounding irrigation canals, was continuously inhabited from at least 3200 B.C. through
Roman times and is believed to hold many important artifacts in addition to those found at the
turn of this century. Any future excavations will require continuous dewatering to a depth of at
least 5 m. Typically 24- or 36-channel profiles or arrays were run using shotgun shell shallow
sources placed off the ends and in the middle of each spread. The high-quality data collected has
been used together with shallow boreholes to map the depth of the water table (l-4 m) beneath ’
the site and in adjacent areas; to locate localized anomalies believed to be associated with burred
man-made structures or objects: to discover a major reflecting boundary, interpreted to be an
ancient channel of the Nile River. at a depth of approximately 100 m; to discover a prominent
deeper reflector at a depth of approximately 180 m; and to discover a prominent shallow reflector
at a depth of approximately 30 m, the origin and significance of which is unknown. The
water-table depth distribution over the site has been determined at approximately 60 borehole
locations. Some of these boreholes. co-located with seismic profiles, provide calibration data for
continuous seismic determinations of water depth as well as soil moisture and soil composition
that are very helpful in the seismic interpretation. Borehole temperature and salinity
measurements help to characterize the groundwater flow regime induced by nearby irrigation
canals. Examples of the field observations and their interpretation will illustrate each of these
major findings.
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Nondestructive Geophysical Surveys For Delineating Buried Tombs And Identifying Their Environmental Status
More LessA number of ring roads and highways surrounding the highly populated city of
Cairo, Egypt are currently under construction. To the south of Cairo, part of these roads is
planned to cross a graveyard of unknown layout. Site observation indicates that a
significant part of this site is a constant drain for sewage and household water. Due to the
sacred nature of the site, non-destructive, geophysical tools (Electromagnetic, electric
resistivity, and Ground Penetrating Radar”GPR”) were decided upon for delineating buried
tombs and identifying their environmental status.
An exhaustive sequence of 2-D data processing techniques was applied to the EMdata
to minimize the disturbed electrical conductivity pattern imposed by the infiltrated
wastewater. Observed and buried graveyard boundaries were delineated on the high-pass
(0.15 cycle/m) filtered conductivity map. Buried tombs (2.5m x 2m) were detected as high
conductivity anomalies indicating that tombs may be filled with soil and/or infiltrated
wastewater. EM-method succeeded in delineating the area1 extent of the buried graves; the
GPR-technique complemented this information by determining their depth of burial. .
A dc-resistivity profile was performed at an abnormally high EM-anomaly, using
dipole-dipole array, to delineate the extent of infiltrated sewage water and its spreading
direction. An 2-D inverse resistivity model revealed a very low resistivity (0.24-0.91
Ohmm) anomaly, indicating its saline sewage water, spreading at the shallow part of the
resistivity section and possessing the highest thickness, about 2.0m, at the northeastern part
of the section close to the nearby housing utilities.
GPR survey lines, at 500 MHz central frequency, was conducted at two selected
EM-anomalies to essentially map the depth of the buried graves. The graves are located
within the depth range of l-1.8m. The observed radar wave attenuation suggested soil
contamination with saline wastewater.
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Significance Of Crossed-Dipole Antennas For High Noise Environments
Authors Stanley J. Radzevicius, Jefhey J. Daniels, Erich D. Guy and Mark A. VendCrossed-dipole antennas can be used to reduce clutter and improve the signal-tonoise
ratio of ground penetrating radar (GPR) surveys, depending upon field conditions
and the targets of interest. The crossed-dipole antenna consists of transmit and receive
antennas oriented orthogonal to each other, and is sensitive to field components oriented
parallel to the long axis of the receive antenna. These cross-polarized components can be
introduced by scattering from subsurface targets or may be composed of scattered crosspolarized
components present in the field incident on the target. The physical shape and
composition of targets will influence the polarization of the scattered field, and this
enables cross-pole and co-pole antenna configurations to discriminate between different
classes of targets for clutter removal. The crossed-dipole antenna configuration also
improves isolation of the receive antenna from the direct arrival of the transmit antenna.
The improved isolation and ability to discriminate between different targets can therefore
result in an improved signal-to-noise ratio.
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Consideration Of Automatic Waveform Interpretation Of Gpr Data To Detect Void Space Beneath A Concrete Highway
More LessFor waveform interpretation of ground penetrating radar (GPR) data, one must compute
the response of the earth to a specific source wavelet. This is not commonly done, because it
requires either prior knowledge of the source wavelet shape, or a good understanding of the local
earth model. When waveform interpretation is possible, then certain steps in the interpretation
process can be automated. This paper describes a successful case history of GPR waveform
interpretation used to solve a problem of locating voids under a concrete highway. It worked in
this case because the earth model was well constrained according to design specifications and
core information. Automatic interpretation is really just the creation and use of a computer
algorithm to recognize specific features in the data. The human interpreter must still do the work
of determining what the diagnostic features are, and then do a good job of writing the program to
recognize them. This process is only cost-effective for large surveys or those where the
distinguishing data features are already known.
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3-D Imaging Of Subsurface Features Using Gpr Array Beam Imaging
Authors Jeffrey L. Orrey, Phil C. Sirles and Charles B. ArchambeauIn this paper, we provide a brief review of standard survey and analysis methods for ground
penetrating radar (GPR) and then introduce a new method for producing three-dimensional (3-D)
images of the subsurface using GPR. We outline the theory of the new imaging method, called
Array Beam Imaging ( ABI ), by way of a schematic description. We then show results from
application of the ABI imaging method to the characterization of a former manufactured gas
plant (MGP) site. The 3-D image results are examined using 3-D isosurfaces, 3-D and 2-D
volumetric projections, and 2-D tomographic slices. These techniques improve the interpretation
of the otherwise standard GPR survey of the relatively complex characteristics of the gas holder
and coal tar at the site. Finally, we discuss the relative advantages of the ABI method over
traditional methods and summarize some potential future applications of the method.
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Polarization And Kinematic Effects In Azimuthal Investigations Of Linear Structures With Ground-Penetrating Radar
Authors M. Pipan, L. Baradello, E. Forte and A. PrizzonAzimuthal variations of the GPR response may be diagnostic of elongated subsurface targets.
We performed tests on two classes of targets of interest in archaeological and engineering
applications: walls (archaeological remains) and underground utilities (plastic and
metallic pipes). The objective of the study is the implementation and test of a procedure
for the identification of elongated subsurface targets by means of GPR which may
provide information on the properties of the materials and may be an effective alternative
at sites where logistic constraints prevent from the acquisition of conventional grids. We
analyzed the response of targets buried at different depths in soils ranging from clays to
coarse sands, to compare the performance of azimuthal Multi-Fold and conventional GPR
techniques. A 3-D azimuthal Multi-Fold (MF) G round Penetrating Radar (GPR) data acquisition
and processing scheme was implemented and tested. Bi-static co-polarized and
cross-polarized 200 MHz and 400 MHz antennas were rotated around a Common Mid Point
in steps of 10’ and 30”. We obtained an average 6000% fold at each azimuth by varying the
source-receiver offset in steps of 10 cm. The amplitude of the radar response and the radar
velocities measured by means of Common Mid Point analysis exhibit sinusoidal variations.
The range of amplitude and velocity can be effectively used to discriminate among targets
of different characteristics. The location of maxima and minima in the (a) amplitude and
(b) amplitude-velocity responses can be used to evaluate the strike of the subsurface targets
in case of small and large radar cross-section respectively.
KEYWORDS
Ground Penetrating Radar - Multi-azimuth - Multi-fold - Velocity analysis - Amplitude analysis
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Detection Of Buried Steel Drums From Magnetic Anomaly Data Using Neural Networks
Authors Ahmed Salem, Keisuke Ushijima, Dhananjay Ravat and Ross JohnsonMagnetic detection to locate buried ferro-metallic objects has become one of the
standard methods in environmental investigation. However, geophysical measurements need
to be interpreted and this can be time consuming. As a result, shallow sources are usually
investigated by heavy machinery without the knowledge of their depth. This practice may
risk contamination by damaging the containers with hazardous materials. Therefore, there is a
need for an interpretation technique that could make rapid decisions in the field in real-time.
Conventional inversion methods cannot meet this need because they depend on initial models
that are nearly correct. In this paper, we have investigated the ability of neural network
processing method to estimate the location of steel drums. Back propagation neural network
was trained to estimate the spatial location of steel drums using theoretical magnetic
signatures of equivalent dipole source. The performance of the neural network was tested
using theoretical and field data. The neural network could estimate the location of drums
from theoretical data with maximum error 0.03 m for depth and 0.24 m for horizontal
location. The neural network also showed a potential to estimate the depths in the presence of
noise. The accuracy of the estimated depth from real magnetic data is greater than 80% when
regional can be adequately removed beforehand. The neural network system has proven to be
fast, accurate, and objective for detection of steel drums.
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Magnetic And Gpr Surveys Of A Former Munitions Foundry Site At The Denver Federal Center
Authors David L. Campbell, Shay Beanland, Jeffrey E. Lucius and Michael H. PowersWe made magnetometer and ground penetrating radar (GPR) surveys over part of
the foundation of a World War II-era foundry located on the Denver Federal Center. The
site-contains a number of highly magnetic source bodies, concrete foundation walls, and
underground openings, buried under a clay cap. The cap is several feet thick and has a
conductivity of about 35 mS/m, making the features underneath it a poor target for
conventional GPR. Indeed, the raw data look unlike typical GPR data, but rather show
reverberation (?) bands under sidewalks and other shallow buried sources. Using a
newly-written computer package, we made plan maps of the GPR response at different
time slices. The sliced GPR data did not outline buried foundry foundations, as we had
hoped it might. The resulting plan maps of the sliced data show sidewalks and other
blobby features, some of which correspond to magnetometer highs.
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A Vetem Survey Of A Former Munitions Foundry Site At The Denver Federal Center
Authors David L. Wright, David V. Smith and Jared D. AbrahamThe present Denver Federal Center in Lakewood, Colorado, was a center for production of small
arms and artillery ammunition during World War II and was then known as the Denver
Ordnance Plant. When munitions manufacturing ended, some of the buildings were converted to
other uses and some were removed, A massive building, thought to be a foundry, just east of
Building 20 at the Denver Federal Center, was removed just before the end of the war.
Remaining subsurface parts of the building are buried under a clayey loam soil. High-resolution
images we recently made using data recorded by the very early time electromagnetic (VETEM)
system clearly show some buried parts of the building or objects that were in the building. Many
of the subsurface structures produced exceptionally strong signatures that we think were caused
by large, relatively shallow buried electrically conductive objects. We find, however, that the
correlation between the VETEM images and magnetic data is not high, suggesting that some of
the highly conducting objects may not have metal in them. The former foundry site affords an
excellent opportunity to evaluate the performance of the VETEM system and other geophysical
instruments because of the location and conditions.
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Advances In Very Early Time Electromagnetic (Vetem) System Data Analysis And Image Processing
Authors David vonG. Smith, David L. Wright and Jared D. AbrahamThe Very Early Time Electromagnetic (VETEM) system operates in a frequency band
between electromagnetic (EM) conductivity systems and ground penetrating radar (GPR).
VETEM survey data exhibit higher resolution than EM methods and better detection
depth than GPR. A single computer application performs data analysis and image
processing, yielding detailed images of transient response over the survey area, with the
ability to discriminate between metallic and nonmetallic buried objects using a method
based on the persistence of the received signal. Processing steps of field data from the
Idaho National Engineering and Environmental Laboratory (INEEL) are presented, and
data processing methods are discussed.
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Optimized Model Resolution Using Low Pass Filters In Tdem Soundings
Authors E. Auken, K.I. Sørensen, P. Thomsen and F. EffersøIn the time domain electromagnetic (TDEM) method it has been common practice to model the
current waveform of the transmitted signal, but the effect of the instrument transfer function has
been neglected. In Effersar et al. (1999) it was shown that inverting TDEM data without taking
into account the system transfer function in the forward modeling scheme lead to an erroneous
description of the shallow part on the geophysical/geological model. The degree of error is very
dependent of the near-surface resistivity of the model. High resistivity models leads to distinct
but localized errors at very early time gates, whereas the effect from models with low to
intermediate resistivities is “smeared” out over a larger time interval.
The system transfer function can be described as a combination of one or several low-pass (LP)
filters in the TDEM receiver. In this abstract we describe some side effects of having a bandlimited
receiver. It turns out that it is possible to actually enhance the model resolution to some
degree by band-limiting the receiver. This means that not only do the low-pass filters in the
receiver system suppress coherent noise from power lines etc., but they also enhance the model
resolution if the filters are of optimal designed.
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Tdem In Groundwater Mapping - A Continuous Approach
Authors K.I. Sørensen, E. Auken and P. ThomsenCulturally developed areas provide a challenge when applying the transient electromagnetic
(TDEM) method, for mapping valley aquifers in inhomogeneous glacial geologies.
Magnetic coupling between the transmitter coil and cultural conductors such as power lines,
metal fences, metal pipes, etc. distort the measurements of the earth responses and generate
datasets that in many cases will yield erroneous interpretations. Furthermore, as TDEM
soundings are routinely interpreted with one-dimensional (1 -D) inversion schemes (Christensen
and Sorensen, 1995), perturbations in data originating from two- and three-dimensional (2-D, 3-
D) geological structures have to be revealed in order to ensure reliable 1-D interpretations
(Auken, 1995).
In Denmark it has become a common practice to perform 16 - 25 soundings/km2. In many cases
this number provides basis for estimating the data and interpretation quality. However, much
denser data coverage is generally required to discover distorted data and to resolve the multidimensional
geology of the valley aquifers. Due to the expense involved in acquiring dense
datasets, coverage is unfortunately seldom attained.
In order to meet the demands of dense spatial sampling a new method, the Pulled Array
Transient Electromagnetic Method (PATEM) has been developed. With the PATEM method a
transmitter and a receiver coil system is towed along profile lines while measuring. Obviously
this technique generates dense data sets and reduces the cost of the fieldwork drastically.
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Variable Frequency Monopole-Dipole Sonic Logging For Mechanical And Hydrogeologic Properties
Authors Charles P. Oden and James J. LoCocoMost traditional sonic logging tools operate at a single frequency. Usually this frequency
is a relatively high frequency, which in turn excites many unwanted modes that can make
waveform interpretation difficult (Paillet and Cheng, 1991). If the survey frequency is too low,
fixed frequency tools may not excite the desired modes in fast rocks or small boreholes. A
variable frequency sonic tool can minimize these problems.
Low frequency tools can provide waveforms from which it is easy to pick shear wave
arrivals in real time. By selecting a proper survey frequency, compressional head wave
amplitude can be reduced, and the first high amplitude head wave is the shear wave. Low
frequency dipole logging can be used to find shear velocities for soft formations (Chen, 1988).
Mechanical properties are readily calculated from compressional and shear velocities.
Many authors relate Stoneley wave amplitude (or Stoneley index) to permeability (Tang,
et al., 1996). Stoneley waves are easily interpreted from low frequency surveys when the
amplitude of other modes are reduced. Stoneley index can be directly generated while logging
from this type of survey.
A prototype variable frequency tool was tested in soft shale, mudstone, and concrete
boreholes. By varying the source frequencies, the modal content of the received waveforms was
controlled. The tool can be configured so that the first high amplitude arrival is a shear wave or a
Stoneley wave. We conclude that a variable tool exhibits greater versatility than conventional
tools by being able to provide good shear wave and Stoneley wave data in real time.
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Physical Modeling Of A Prototype Slim-Hole Time-Domain Dielectric Logging Tool
More LessDielectric logging tools were originally developed by the oil industry to determine oil saturation in highly
resistive environments. Conventional resistivity and induction tools are insensitive to the oil/water interface within
fresh water formations. Recently dielectric logging tools have found potential uses in environmental applications to
estimate porosity, to distinguish between water and organic-solvents, estimate water content, and to provide velocity
information for surface radar and boundary constraints for radar tomography. A prototype slim-hole time-domain
dielectric logging tool was developed at the U.S. Geological Survey. This tool was designed to utilize a broadband
EM-pulse to determine the frequency dependent dielectric properties of the surrounding geologic medium. In an
attempt to understand and characterize the tool, physical modeling experiments were conducted using a 100 gallon
polyethylene barrel filled with dry silica sand, deionized water saturated silica sand, and deionized water.
Examination of the results indicated that the borehole has a strong influence on the dielectric logging tool.
We have found that the travel time and amplitude are not monotonic with dielectric properties. The likely
explanation of the observed effect is that wave guides are being set up within the borehole and/or the tool.
Reflections and resonances internal and external to the tool produce a frequency-dependent tool response. Favorable
results from the physical modeling and field tests indicate that the tool is highly sensitive to changes in the dielectric
permittivity of the surrounding geologic media, particularly to thin layers perpendicular to the borehole.
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Incorporating Size Scaling As A Modelling Parameter For Estimating The Dielectric And Electrical Properties Of Porous Rocks And Soils
More LessThe solid components and pore spaces in rocks and soils have a spectrum of size scales,
ranging from clay platelets and intergranular cracks to vugs and boulder size grains. While the
size scale of structural features has been recognized as a factor in determining the physical
properties of porous media, it is rarely an explicit modelling parameter.
The differential effective medium approximation (DEMA) is used to estimate the dielectric
and electrical properties of porous rocks and soils. This approximation employs a sequential
embedding process that implies a progressive size scale increase as it proceeds. This feature of
DEMA is used to explicitly incorporate size scale relationships that occur in porous rocks and
soils into estimates of their dielectric and electrical response. The effects of size scaling are
investigated using a model where the pore space is divided into microscopic porosity (e.g.,
intergranular cracks), mesoscopic porosity (e.g., main pore volumes) and macroscopic porosity
(e.g., vugs and fractures). Modelling results demonstrate that the dielectric and electrical
properties of porous rocks and soils are very sensitive to the range of porosity size scales present.
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