- Home
- Conferences
- Conference Proceedings
- Conferences
18th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 03 Apr 2005 - 07 Apr 2005
- Location: Atlanta, Georgia, USA
- Published: 03 April 2005
61 - 80 of 146 results
-
-
Internal Structure and Preferential Flow of A Waste Rock Pile From Geophysical Surveys
Authors Michel Chouteau, Jérôme Poisson, Michel Aubertin and Daniel CamposThe authors have carried out a geophysical investigation on a waste rock pile at the Laronde gold mine (Agnico-Eagle Ltd, Quebec). GPR, low-induction number EM and 2D resistivity tomography measurements have been conducted during consecutive field surveys in 2002 and 2003 on top of the pile to map its internal structure. Repeated infiltration tests and geophysical monitoring from ground surface have also been performed to map preferential flow paths. Using the field data, the authors propose here a three-layer model for the first 5-6 m of the pile, mainly based on electrical conductivities. Electrical conductivity increases with the degree of oxidation of the sulphidic minerals contained in the waste rock. The contact between unoxidized-oxidized waste rocks is typically marked by a well-defined resistive-conductive boundary, as shown by digging a 2.5 m-deep trench. Integration of geophysical and hydrogeological information indicates that there is a lateral conductivity variation, which may be due to the deposition method, mechanical alteration caused by machinery, and by increased oxidation of sulphides near the external boundary of the pile. GPR monitoring during infiltration tests seems to indicate preferential flow paths towards a zone of low sulphide content materials and low oxidation by products. The resistivity and GPR methods appear to be efficient geophysical methods to characterize the internal structure of the Laronde waste rock pile.
-
-
-
Spectral Induced Polarization (SIP) Measurements for Stability Assessment of Tailings Dams
Authors Ernst Niederleithinger, Sabine Kruschwitz and Matthias BehrensTailings dams pose major risks to human life and the environment. The often poor construction and low maintenance level has caused serious accidents in both developed and developing countries. The EC funded project TAILSAFE is aimed to find ways for better investigation, stabilization and management of these facilities. Geophysical methods play an increasing role in the investigation of tailing dams. But the interpretation of the results and the translation into something useful for the engineers is often difficult. Thus several geophysical techniques have been tested at tailing dams in Germany, Hungary and Romania. The focus was on detecting structures in the dams and determining the water level. The measurements are accompanied by sampling and lab investigations. The focus of the paper is on the use of the SIP technique.
-
-
-
Using Helicopter Electromagnetic Surveys To Identify Potential Hazards at Coal Waste Impoundments
More LessIn July 2003, the National Technology Transfer Center contracted with Fugro Airborne Surveys
to perform helicopter electromagnetic surveys of 14 coal waste impoundments in southern West
Virginia. The purpose of these surveys was to detect conditions that may lead to impoundment failure
either by structural failure of the embankment or by the flooding of adjacent or underlying mine works.
Specifically, the surveys attempted to: 1) identify saturated zones within the coal waste, 2) delineate the
paths of filtrate flow through the embankment and into adjacent strata or receiving streams, and 3)
identify flooded mine workings underlying or adjacent to the waste impoundment. In-phase and
quadrature data from the helicopter surveys were inverted using EM1DFM software to generate
conductivity/depth images. Conductivity/depth images were then spatially linked to georeferenced air
photos or topographic maps for interpretation. Preliminary analysis of the data indicates that helicopter
electromagnetic surveys can provide a picture of the hydrologic conditions that exist within the
impoundment. However, results from the helicopter electromagnetic surveys must be corroborated with
data from other sources to accurately assess the potential for impoundment failure or the potential for
filtrate from the impoundment to contaminate local streams and aquifers.
-
-
-
Efficient Large-Scale Utility Mapping With Radar and Induction Arrays
Authors Michael Oristaglio, Ralf Birken, Thorkild Hansen, Ross Deming, Scott MacIntosh and Qifu ZhuA project sponsored by the United States Department of Transportation (U.S. DOT) has developed a new mobile geophysical system combining an array of broadband electromagnetic
induction (EMI) sensors with an array of ultra-wideband ground-penetrating radar (GPR) antennas. This “dual-array system” was designed for mapping underground utility networks efficiently over large areas, but can also be useful in environmental surveying for applications such as leak detection and hazardous waste monitoring. The project was part of the Pipeline Safety Research and Development Program1 of the U.S. DOT Research and Special Programs Administration. Several utility companies, including Consolidated Edison Company of New York and Regional Water Authority of South Central Connecticut, participated in the project. The EMI array consists of 16 vector magnetometers (induction coils) with a flat frequency response from about 1 to 100 kHz. Signals from each sensor are recorded and digitized as time series, with a sampling rate of 1 MHz. The EMI sensors are arranged in two linear arrays, each consisting of 8 sensors with a spacing of 30 cm; the arrays are offset vertically by about 50 cm. The system works with two types of transmitters: “clamp-on” transmitters which can inject current at discrete frequencies onto individual pipes (by galvanic or toroidal clamps) and a 3-axis induction coil which rides “on-board” with the transmitters and operates over the same frequency range as the sensors. The GPR array, which is based on the commercial CART Imaging System (Birken et al., 2002), consists of 17 antenna elements in an arrangement that creates 16 independent radar channels (transmitter-receiver pairs). The GPR array system has two antenna sets: one set has a central frequency of about 200 MHz and a channel spacing of about 14 cm; the other, a central frequency of 400 MHz and a spacing of 8 cm. The positioning system is designed to allow surveying in arbitrary patterns. Each array is mounted on a trailer whose position is monitored by a laser surveying instrument as the array moves over the survey area. Special algorithms merge data from different passes of each array to create a regular data grid. The radar data are imaged into a 3D volume using standard synthetic-aperture seismic imaging techniques adapted for GPR. The EMI data are inverted using a parametric model that assumes currents in the subsurface flow mainly along a network of (possibly interconnected) pipes. Two large surveys have been conducted with the dual-array system. One survey in the spring of 2004 successfully mapped a complex network of subsurface water, electrical, gas and telecommunication lines in Connecticut for a local water utility company. This survey covered over 2000 sq m with radar traces on a 10 cm grid and EMI data on a 30 cm grid. A second survey done in the summer of 2004 mapped electrical lines emerging from an electrical substation in New York. 1The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the RSPA or the U.S. Government.
-
-
-
Voodoo Methods: Dealing With The Dark Side of Geophysics
By Greg HodgesThe exploration industry has been plagued since the dawn of technology with near-magical oil,
gold and waterfinders. They do untold damage to the reputation and business of honest geophysical
applications and research. A geophysicist with sound scientific knowledge can usually recognize when
geophysics is "from the dark side", but it can be difficult to convince non-scientists. Exposing the
voodoo methods can be a complex and expensive nightmare of politics, marketing, and litigation.
Some common characteristics of voodoo geophysical methods are: dubious theoretical bases,
fantastic levels of instrument sensitivity, phenomenally accurate interpretations, extraordinary levels of
secrecy, and combative or evasive response to challenges. The evaluator should also determine whether
the questionable method is the product of over-zealous marketing, misguided science, or fraud.
Funding agencies and corporations must insist on assessment and approval by technical experts
before investing in a new system. The technical investigators must be open-minded, but rigorous. The
tests must be definitive, and the testers must have the right to publish results. Fraudulent methods shy
away from technical testing and publication, and refusal of the purveyor of a new system to comply with
evaluation and publication of results must be viewed with the greatest suspicion.
-
-
-
Human-Sensed Fields: Does Dowsing Response Correlate With-Self Potential Or Conductivity Anomalies?
Authors Charles T. Young and James TrowDowsing is the use of metal rods, forked sticks, pendulums, etc to locate minerals, water, pipes
etc. Dowsing has been practiced for centuries and in various world cultures, and there are abundant
reports of dowsing success in the non-scientific, popular literature. The natural question arises whether
the dowsing response correlates with any geophysical measurement such as self potential or
electromagnetic response. The dowsing reported here uses U-shaped bent metal rods carried along a
survey line. Both authors have found that the rods move in their hands. We report dowsing responses for
the two authors and compare these responses with self-potential and electromagnetic response across a
folded graphitic slate body and across metallic copper deposits, both in Michigan’s Upper Peninsula.
-
-
-
Smoke Without Mirrors: A New Tool for The Geophysical Characterization of Shallow Karst Cavities
Authors Jonathan E. Nyquist, Mary J.S. Roth, Sandra Henning, Ron Manney and John PeakeWe are involved in a multi-year study to evaluate electrical resistivity as a tool to characterize
thinly-mantled karst. Guided by the results of a multielectrode resistivity survey, we drilled into a cave
7m below the surface. While mapping the cave's dimensions, triangulating using laser pointers and a
downhole camera, we observed a snake crossing the floor of the cave. Hypothesizing that one or more
animal burrows must intersect the karst network, we purchased a Hurco Technologies, Inc., Power
Smoker II, designed for smoke testing plumbing systems for leak detection. It is a 2.5 hp Honda Motor
modified to heat and blow Hurco's LiquiSmoke into plumbing systems. We injected non-toxic smoke at
a rate of approximately 700 cfs, but did not discover an animal burrow. After about half an hour,
however, we noticed puffs of smoke coming up through the grass about 30 ft from the borehole along a
straight line about 10 ft long. Comparison with the resistivity data shows that the smoke emerged downstrike
from the borehole along the same limestone ridge as the cave. We conclude that "leak-testing"
with non-toxic smoke may prove to be an effective complement to geophysical investigations of karst.
-
-
-
Application of 2D-Ert In Feasibility Study of Hydropower Projects In Nepal
More LessIn Nepal seismic refraction is the traditional method of subsurface exploration for geotechnical
applications. Until the mid-90s seismic refraction was routinely used to investigate proposed sites for
hydropower projects of Nepal. These areas lie in the mountain and are inaccessible for vehicular
transportation. Very high heterogeneity of surface material creates poor energy coupling for both source
and receiver. Because of the high-energy content and easy transportability, explosives were the preferred
source for the generation of seismic waves.
Due to the rebel activities in the recent years, however, the government has tightened regulations
on transporting and using explosives. This situation has forced the hydropower projects to search for
alternative geophysical methods in place of seismic refraction. Electrical resistivity tomography (ERT)
was selected as a possible replacement method. In the initial stage of the application of ERT, various
electrode arrays and data acquisition approaches were evaluated for data quality and subsurface
resolution. Experience in different projects reveals that the pole-dipole electrode arrangement with data
levels at different electrode spacing is suitable for better resolution of the subsurface material.
Furthermore, manual acquisition, although less productive than automatic acquisition, seems to secure
higher quality data. With these systems of data acquisition ERT was able to fulfill most of the objectives
of the subsurface investigation at hydropower projects.
-
-
-
Geophysical Exploration at The Giza Plateau, Egypt A Ten-Year Odyssey
More LessThe Giza Plateau of Egypt has many above-ground marvels (Pyramids and the Great Sphinx) and
many hidden or suspected tunnels/rooms that may lurk in the limestone beneath the sands. Since 1991,
we have been granted several opportunities to look for buried structures on the Plateau as well as on, in,
and under some of the Plateau’s more famous structures. Five separate campaigns have included
geophysical surveying utilizing ground penetrating radar (2D and 3D), electromagnetic conductivity,
magnetic field, and seismic reflection, refraction, and refraction tomography techniques. The results of
these surveys can be qualified as ranging from glowing successes, to tantalizing opportunities, to
fascinating failures. 2D and 3D GPR surveys within the Sphinx Enclosure and in the sands west of the
Sphinx have detailed anomalous structures within the shallow limestone that defy geologic interpretation
(man-made?) and are waiting to be excavated. Whether or not they will ever see exposure may be the
source of the Sphinx’s inscrutable smile.
-
-
-
Measuring Sub-Seabottom Seismic Velocities - Some Unusual Experiments
During the last 30 years, we have performed a number of unusual experiments to measure P- and Swave
velocity structure of unconsolidated sediments below the seafloor at sites to water depths of 700
m. These experiments were designed to aid in specific geotechnical problems related to soil stability
along pipeline routes or beneath bottom-founded structures as well as to provide regional information
for military purposes. Some of these experiments were done in open-water conditions, but many were
performed beneath ice-cover.
Early testing was directed towards mapping sub-seafloor ice-bonded permafrost in the Beaufort Sea
and elsewhere in the Arctic Archipelago, mainly using dynamite sources. Continuous ice-cover at high
latitudes presented specific challenges for refraction methods and various devices and hydrophone
arrays were designed for deployment beneath the sea-ice through open leads or drilled holes. Later
testing evolved from seabottom-laid hydrophones to towed, near-bottom arrays and non-dynamite
sources. As well, mapping of shear wave velocity structure was tested using seabottom coupled
interface waves.
All of these experiments (successful or otherwise) were learning experiences in one form or other,
and it is hoped that documentation of these experiments herein will be of some future research value.
-
-
-
How Far Will You Go To Collect The Data?
Authors K. Michael Garman and Scott F. PurcellSubsurface Evaluations, Inc. has been using three-dimensional multi-electrode resistivity (3DMER)
surveys in the Tampa, Florida, area to image karst features beneath undeveloped sites; around and
beneath buildings; beneath bridges, canals, and tertiary treatment ponds; and around bridge and highway
support structures. The surveys have been very successful for identifying karst features such as buried
depressions, breached confining layers, cavities and caves. Although the survey data have been very
useful for site evaluation and positioning test borings, many interesting and unpredicted problems
develop during the long days it takes to setup and collect the surveys when over a mile of cable has been
deployed in urban areas and the unpredictable Florida weather turns bad. Alligators, Soccer Moms in
minivans, lightning, flash floods, traffic, and small boats create unusual situations that often require
novel solutions. Somehow, the data usually gets collected even though the field crew often believes
management has acted irresponsibly. We provide some interesting examples of 3D-MER surveys with
the stories of how the data were collected.
-
-
-
Integrated Geophysical Methods for Lng Site Characterization In A Jungle Environment
Authors Finn B. Michelsen and Martin MieleThe contribution of integrated geophysical survey methods to site characterization in difficult
and challenging environments is extremely valuable to design engineers and planners of new Liquid
Natural Gas (LNG) facilities, especially if the site is located in a remote and geologically complex area.
In particular, subtropical jungle environments present unique equipment and instrument preparation
requirements, field operation problems, and have certain human risk factors that must be taken into
account. Qualifying and characterizing jungle sites for installation of an LNG facility is costly, time
consuming, and requires the application of a variety of geoscientific investigation methods, including
geophysics. In conjunction with geotechnical and other site investigation methods, data from
continuous resistivity profiling, seismic refraction tomography, P-S wave downhole seismic, and
Wenner sounding surveys are used as an aid the design and planning of an LNG expansion facility
located on Bioko Island, Equatorial Guinea.
-
-
-
The Pentagon Building Performance In The 911 Crash
Following the 911 crash of an airliner at the Pentagon, the American Society of Civil Engineers
established a team to study the damaged structure and make recommendations for the future. The team
reviewed available information on the structure, the crash loading, and focused assessments by others.
The team then analyzed the essential features of column response to impact, the residual frame capacity,
and the structural response to the fire. Plausible mechanisms for the response of the structure to the crash
were determined and recommendations were offered for design and construction. This paper
summarizes the study and discusses the role of geophysics in such forensic inquiries.
-
-
-
Testing A Safe Acquisition Procedure for An Effective Application of GPR To Security Operations
Authors Maurizio Lualdi and Luigi ZanziTerrorism is posing new technological problems to security forces. The need of checking for
hazardous targets such as explosives, bombs, weapons, etc., hidden inside unexpected packages or
embedded within blocks of other materials is increasing. GPR has been already explored for Anti-
Personnel Mines (APM) detection and most prototypes are based on single or arrays of antennas
surveying the suspected area from a distance of a few centimeters. We are exploring a flexible solution
that is expected to be: a) applicable to different scenarios such as soil inspections (as for landmines) but
also investigations on packages, blocks of materials, walls, etc., b) adaptable to a set of antennas to
ensure proper penetration and resolution, c) safe for operator and equipment, d) accurate in antenna
positioning to produce 3D reconstructions, e) based on a survey procedure that allows the contact with
the medium to eliminate the energy loss produced by the non-contact approach. A single antenna plus an
armored PSG (Pad System for Georadar) seem to fulfill the requirements. Radar performances were
tested to explore the effects of the armor material. Tests were executed on the landmine field managed
by the Joint Research Center (JRC) in Ispra (Italy). The results demonstrate the feasibility and the
advantages of this solution.
-
-
-
Tunnel Detection Along The Southwest U.S. Border
The U.S. Army Engineer Research and Development Center (ERDC) has worked with U.S. Law
Enforcement Agencies (LEAs) since 1995 to address the problem of clandestine tunnels beneath the
U.S./Mexico border. ERDC has performed tunnel-related research, equipment development, or tunneldetection
missions at the request of the LEAs, coordinated by Joint Task Force 6 (JTF-6, Fort Bliss, TX,
now known as JTF-N for Northern Command, US Army). This support to LEAs has revealed the
importance of understanding the geologic context of a suspected tunnel site as a basis for selecting the
appropriate geophysical tools and interpreting anomalies indicated by geophysical data. Tunnel detection
missions always involve multiple tools and techniques. A combination of geophysical instruments is used to
record data based on different physical principals. When interpreted in a regional geologic context, the
combined geophysical methods improve the likelihood of success for tunnel detection.
A variable-frequency electromagnetic survey tool was developed in the 1990s as part of tunneldetection
research, and proven at a tunnel test bed near Otay Mesa, CA. Also at the Otay Mesa site, an
ERDC-led team installed and tested a prototype passive-seismic fence, a system that can detect machine and
impact noise during the tunnel excavation process. This seismic fence concept has strong potential for
deterring tunneling in geographic areas where tunnels have been found most frequently and where cultural
clutter limits the usefulness of surface geophysical techniques and tunnel detection.
Current ERDC tunnel detection efforts (March 2005) are coordinated with the National Geo-
Intelligence Agency (NGA, formerly NIMA) to combine electromagnetic and radar methods with emerging
technology in microgravimetry.
-
-
-
Simultaneous Geophysical Surveys Using a Towed Multi-Sensor Platform and Its Application to Characterisation of Brownfield Sites
Authors Chris Leech, Ian Hill and Tim GrosseyThe multi-sensor platform allows dense data sampling with an array of geophysical sensors, chosen for the particular purpose e.g. magnetic, EM, Radiometric, VLF or metal detection. Geophysical data and navigation parameters are telemetered in real-time to a base station where they are viewed and logged on a laptop PC. Data can be collected from up to 6 geophysical sensors plus navigation at data rates in excess of 10 Hz. The system can be pulled at up to 7-8 km per hour in normal terrain, using a lawn tractor, or ATV. The combination of multi-parameter measurements at each point of the survey maximises the ability to characterise the material underlying the site. The real-time transmission of the data allows real-time data QA, survey design modification, and facilitates rapid in-field processing of the data. The method is applied to the geological, and archaeological sites in addition to part of a large integrated site investigation over a land fill site.
-
-
-
Final Disposal of Spent Nuclear Fuel Triggers Security-Related Geophysics
By Olli T. OkkoA geological site investigation including a comprehensive geophysical program confirmed the suitability
of the studied crystalline bedrock sites for the safe disposal of highly radioactive spent nuclear fuel.
According to a legal decision endorsed by the Parliament in 2001, the final repository of Finnish spent
nuclear fuel shall be located at the Olkiluoto site in Eurajoki, western Finland. The next phase of the site
investigations includes the construction of underground premises for rock characterization purposes. The
excavation of these galleries began in 2004. Since these premises are scheduled to form a part of the
final repository, these investigations are subject to regulatory control with safety, security, safeguards
and societal aspects. The national geophysical site characterization and monitoring program planned for
the long-term safety assessment shall also be applied to other repository performance related matters.
The construction documentation and the adjoining geophysical monitoring program are applied to
safeguard the repository for homeland security purposes. The regulatory use of geophysical methods
creates new challenges to the geophysical community.
-
-
-
Detection of Subsurface Utilities Using GPR Techniques
Authors Sherif M. Hanafy and Mohamed A GamalThe nondestructive evaluation of buried utilities is of interest for engineering and environmental
applications. The use of Ground Penetrating Radar (GPR) for buried utility detections is one of the most
common geophysical techniques due to its capacity for accurate results in either horizontal or vertical
directions. Electric cables and metallic pipes are easily recognized on GPR profiles due to their high
dielectric values relative to surrounding soils. In this study, 12 different sites are investigated using GPR
techniques to detect buried utilities, such as electrical cables, water, and derange pipes located within the
first 3 meters of the ground’s surface. At each investigation site, two perpendicular GPR profiles, using
a 200 MHz antenna, are collected in order to detect any buried utilities. The area under study is
excavated after GPR data acquisition for manual verification. It is found that electric cables are easy to
recognize on radar profiles by their sharp hyperbola edges and multiples extending to the bottom of the
data set. Water pipes have especial characteristics on GPR lines, indicated by a thick, small hyperbola
without any multiples. The presence of cement blocks masks any object beneath them, but they are
prominent on radar lines as high amplitude reflections.
-
-
-
Underground Utility Location Challenges Using GPR: Life On The Streets
Authors Randy Sorenson and David TillsonThis paper presents a historical account of our evolutionary experiences over the last 8 years
using conventional GPR to locate underground utilities, typically prior to the installation of new water
lines, sewer lines, gas lines, telecommunication cables, etc. Brief summaries of several case histories
are presented to illustrate how GPR can be utilized, with and without, other geophysical techniques.
-
-
-
Location of Mammoth Remains In Perma-Frost of Northern Siberia Using GPR and Multifrequency Em
Authors Ken-Ichiro Makino and Hidetoshi MiuraIt is generally considered that that Wooly Mammoths have been extinct for around 10,000
years BP, however it is unknown whether the reasons for their extinction were due to an abrupt
change in the Earth’s climate, disease, or to indiscriminate hunting. This paper describes a
geophysical investigation conducted in 2004 to hunt for remains of Mammoths to assist in
studying the causes of their extinction. Ground Penetrating Radar (GPR) and
Multifrequency Electromagnetics (MF-EM) were used to map the subsurface of the
permafrost at sites along the Artic coastline of Northern Siberia. The sites were preselected by
helicopter reconnaissance, followed by ground geophysical surveys. The results obtained from
one control site plus two field sites are presented here. It is concluded that GPR is a valid method for mapping skeletal remains from Mammoths,
however there is little signature obtained with MF-EM due to the poor contrast between the
remains and the properties of the surrounding permafrost.
-