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25th Symposium on the Application of Geophpysics to Engineering & Environmental Problems
- Conference date: 25 Mar 2012 - 29 Mar 2012
- Location: Tucson, USA
- Published: 25 March 2012
181 - 195 of 195 results
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NOISE SOURCES AND PARAMETER ESTIMATION VARIATION IN RECENTLY DEVELOPED EMI SENSORS USED FOR UX0 DISCRIMINATION
By Bruce BarrowA variety of electromagnetic induction (EMI) sensors have been recently developed for the purpose of discriminating buried unexploded ordnance (UX0) from other metallic clutter. The ultimate goal is to reduce the cost of cleaning up military ranges by positively identifying the EMI anomalies that come from dangerous UXO. This allows the clean-up operation to ignore the far larger number of anomalies that originate from other metallic clutter. These sensors are designed to collect data locally over the EMI anomaly. The data is used to identify UXO by using a physics-based model inversion. For the UXO problem, an induced dipole moment model is used and the inverted magnetic polarization factors are used to identify UXO. Errors in the inverted polarization parameters are driven by system noise and limit the ability to distinguish UXO and clutter.
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INTEGRATION OF TOTAL GAMMA AND SPECTRAL GAMMA LOGGING OVER EXTENDED PERIODS FOR INVESTIGATION AND MONITORING OF RADIOACTIVE CONTAMINATION IN THE VADOSE ZONE
By Rick McCainThe Hanford Site in southeastern Washington State produced plutonium for the United States nuclear weapons program from 1944 to 1988. Large quantities of highly radioactive waste were generated as a result, and cleanup continues today. Since the early days, gamma measurements in boreholes have been recognized as a means to detect and monitor radioactive contaminants in the subsurface. Total gamma and spectral gamma data have been collected with a variety of detectors over the years. Early data consisted of written records of count rates, and later, strip charts. Log data are available in electronic format from as early as the mid-1970’s. High-resolution spectral gamma detectors have been used since the early 1990’s to provide identification and quantification of man-made radionuclides. There are several thousand wells and boreholes across the Hanford Site, and many of these have been logged multiple times over decades. This paper provides a general overview of gamma logging activities at Hanford and shows how integration and standardization of data from multiple detector systems can be used to establish a coherent history of contaminant migration over time.
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ARCHAEOGEOPHYSICAL STUDIES CONDUCTED ON SINOP BALATLAR CHURCH
Authors Fethi Ahmet Yuksel, Gulgun Koroglu and Mehmet Safi YildizSinop, Turkey was founded at the tip of Cape Boztepe on Sinop Peninsula on the most northern edge of the Black Sea coast.The Balat Church complex in Sinop houses a stratigraphic structure stretching from Roman times to the Ottoman period. These structures include an area that has been systematically used for long periods from the Romans to the Ottoman State on the Black Sea coast of Anatolia. From the early period to the present day since Sinop was built on the same location, it is not easy to discern the urban fabric of different periods. Within the city, the most important archeological finding involving the late Roman and early Byzantium periods, and known in scientific journals and colloquially, is the Balatlar Church or the Mitridates Palace. This site is a cross planned large structure and although there are no remains of the roof of the structure, the 5 to 6 m height walls have remained intact to this day and consist of what may be defined as triangular planned chambers that are inter-connected to each other. Despite the fact that only the outer walls remain standing, remnants or traces of carriers or the grounds of the inner sections of the area surrounded by the walls are not present. The remains of a cistern of four sections attached to each other that is triangularly planned and that is covered with barrel vaults are assumed to be related to this structure.
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USE OF GEOPHYSICAL METHODS TO CHARACTERIZE THE HYDROGEOLOGY OF ASSATEAGUE ISLAND NATIONAL SEASHORE, WORCESTER COUNTY, MARYLAND, 2010
Authors Carole Johnson, John Masterson, Eric White, Emily Voytek, Peter Joesten, Brandon Fleming and John LaneA suite of borehole and surface geophysical methods was used to characterize the lithology and salinity of the subsurface of Assateague Island, a barrier island on the Atlantic Coast of Maryland and Virginia. The U.S. Geological Survey, as part of its Climate and Land Use Change Research and Development Program, is conducting a multi-year investigation to assess potential impacts to the natural resources of Assateague Island National Seashore that may result from changes in the hydrologic system in response to projected sea-level rise. The geophysical data collected as part of the characterization phase of this investigation will serve as the foundation for development of numerical groundwater-flow models to assess the potential effects of climate change on the coastal groundwater system of Assateague Island. Geophysical data were collected along five transects across the island. Methods used included borehole electromagnetic induction and gamma, and surface timedomain electromagnetics, frequency-domain electromagnetics, ground-penetrating radar, and coupled-capacitance resistivity. Two of the transects were in areas subjected to frequent and periodic overland wash and two of the transects were in the oldest, most stable part of the island where there is no overland wash. Based on an integrated interpretation of the geophysical data, it was concluded that the geophysical methods used are effective for determining the following: approximate location of the freshwater/salt-water interface, the distribution of fresh and brackish water in the shallow aquifer, the geometry of the fresh groundwater lens beneath the island, and the distribution and thickness of fine-grained lagoonal and peat deposits in the subsurface throughout the island.
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Characterization of Waste Density and Settlement via Microgravity
Authors K.D. Harris, C. Samson and P. van GeelOptimizing the utilization of landfill space and production of biogas, which can be used as an energy source, is dependent on understanding the compaction and stabilization of waste over time. Maximum compaction minimizes the landfill footprint; however, it might not provide the optimal environmental conditions for bacteria development and waste stabilization. This paper reports on a research project which pilots the use of repeated microgravity surveys to map changes in waste density of waste over time in a bioreactor landfill. Over the duration of 3 years, several microgravity surveys will be conducted on a new cell at a bioreactor landfill in Sainte- Sophie, Quebec, Canada, as it is gradually filled with waste up to a height of 25 m. The paper presents a comparison of gravity data acquired in June 2010 (waste height ≈5.5 m) and April 2011(waste height ≈13 m).
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IMAGING IN KARST TERRAIN USING ELECTRICAL RESISTIVITY TOMOGRAPHY AND SURFACE WAVE METHODS
Authors Evgeniy Torgashov, Neil Anderson, Mengxing Li, Ahmed Ismail and Adel ElkrryElectrical resistivity tomography (ERT) profiles were acquired along traverses at two study sites (Jefferson City and Lane Springs) in central Missouri using overlapping arrays consisting of 68 electrodes spaced at 5-foot intervals. Multi-channel analyses of surface wave (MASW) data were acquired at 50 ft intervals along each traverse; both 1-D and 2-D shear-wave velocity profiles were generated. The primary objective was to map variable depth to top of rock based on both soil/rock resistivity and shear-wave velocity contrasts.
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IMPACT OF 3D GPR ON SUBSURFACE UTILITY ENGINEERING QUALITY LEVELS
By Ralf BirkenThe combination of Subsurface Utility Engineering (SUE), Geophysical Array Technologies, and reduced use of exposures, e.g. vacuum excavation, may proof to be best way to negotiate cost and risk. SUE is an engineering practice concerned with obtaining information about the location of underground utilities with different levels of reliability/accuracy. Knowing the capabilities and limitations of SUE methods used and their associated risk allows for proper management of a subsurface construction projects. Accurate 3D locations of buried utilities derived by SUE are not only desired for safety reasons, but also to expedite design and construction projects often providing cost savings in the process.
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BOREHOLE NMR PERMEABILITY ESTIMATES AND UNCERTAINTY IN AN UNCONSOLIDATED FLUVIAL AQUIFER, KANSAS, USA
Borehole nuclear magnetic resonance (NMR) measurements may be used to estimate permeability at several depth intervals in the saturated zone. The empirical Schlumberger-Doll Research (SDR) equation utilizes NMR-derived porosity and an average NMR relaxation time (representative of surface-area-to-volume ratio) to estimate permeability (kSDR) using three fitting parameters. While it would be possible to optimize the fitting parameters for each depth, it is more useful to have SDR equation parameter values that are valid for the entire length of a borehole or for a study site.
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GEOTECHNICAL APPLICATIONS OF GROUND PENETRATING RADAR AT REMOTE SITES IN WESTERN CANADA
By Eric JohnsonA rapidly developing resource industry that is constantly building new infrastructure in remote locations, the extensive use of ice roads in winter, and thick and extensive muskeg cover in Northern and Western Canada are among the circumstances that require the use of ground penetrating radar (GPR) to assist in addressing near surface geotechnical challenges. This paper will describe four case studies where GPR surveys provided essential and quantitative information in remote situations where extensive or sufficient intrusive information was simply impossible to acquire.
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ELECTRICAL RESISTIVITY TOMOGRAPHY INVESTIGATIONS
Authors Evgeniy Torgashov, Neil Anderson, Ahmed Ismail and Jeremiah ObiElectrical resistivity tomography data were acquired at three study sites in Missouri. Sites 1 and 2 were earth fill dams; site 3 was immediately adjacent to a bridge abutment.
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LOCATING UNMARKED GRAVES IN HISTORIC CEMETERIES USING GROUND PENETRATING RADAR
Authors Evgeniy Torgashov and Neil AndersonGround penetrating radar (GPR) control was acquired at several historic cemeteries in south-central Missouri, with the objective of locating unmarked graves. At each study site, GPR profiles were acquired along closely-spaced traverses using a single 400 MHz antenna coupled to a survey cart. The locations of known graves, trees, tree roots, utilities, and small surface depressions were carefully noted. The latter was of particular interest because unmarked graves, especially in cemeteries that were neglected, are often characterized by surface depressions caused by the degradation of the coffin/content and the collapse of the overlying soil.
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LOCATING UNDERGROUND STORAGE TANKS USING A GROUND PENETRATING RADAR AND METAL DETECTOR
Authors Evgeniy Torgashov, Adel Elkrry and Neil AndersonGround penetrating radar (GPR) control and metal detector data were acquired at two study sites in St. Louis with the objective of identifying and locating buried underground storage tanks (UST). GPR profiles were acquired along closely-spaced traverses using a single GSSI 400 MHz antenna; metal detector data were acquired along the same traverses using a Geonics’ EM61-MK2. Both instruments were coupled to wheeled survey carts.
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INTEGRATION OF DOWNHOLE ACOUSTIC TELEVIEWER IMAGING, ULTRASONIC LABORATORY SHEAR WAVES VELOCITY MEASUREMENTS AND MULTI-CHANNEL ANALYSIS OF SURFACE WAVES FOR GEOTECHNICAL SITE CHARACTERIZATION: RILEY AND DOUGLAS COUNTIES SITES, KANSAS, USA
Authors Amelia Fader-Chumbley, Abdelmnoeam Raef and Assad EsmaeilyGeotechnical site characteristics are a function of the subsurface elastic moduli and the geologic structures. This study integrates borehole, surface and laboratory measurements for a geotechnical investigation that is focused on investigating shear wave velocity variation and its implication to geotechnical aspects of two sites in eastern Kansas. The area has a potential of seismicity due to the seismic zone associated with the Nemaha formation where earthquakes pose a moderate hazard. This study is in response to recent design standards for bridge structures require integrating comprehensive geotechnical site characterization.
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THE EFFECTS OF VARYING ACQUISITION PARAMETERS AND ARRAY ORIENTATIONS: AN MASW CASE STUDY
Authors Mengxing Li, Adel Elkrry, Evgeniy Torgashov, Ahmed Ismail and Neil AndersonMultichannel analyses of surface wave (MASW) data and electrical resistivity tomography control were acquired at two test sites in central Missouri. Limestone bedrock at both test sites was relatively shallow and dissected in places by solutionwidened joints. The ground surface at both test sites was relatively flat.
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GROUNDWATER EXPLORATION EXAMPLES USING CSAMT AND NSAMT
More LessAlthough the presence or absence of water in the subsurface obviously should have an effect on the electrical properties of the ground, in the exploration process, particularly in relatively unexplored areas, it is not always immediately clear whether groundwater is a low resistivity target relative to background, or a high resistivity target. In this paper, we discuss one case history in which groundwater production was successful after drilling a high resistivity target, whereas in a nearby project, groundwater production correlated with a low resistivity zone. Correlating the surface geophysical methods (in this case, controlled source and natural source audio-frequency magnetotellurics, or CSAMT and NSAMT) with known and suspected geological and hydrological background information was critical to understanding the production. In both cases, future wells can now be properly planned based on the geophysics.
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