- Home
- Conferences
- Conference Proceedings
- Conferences
20th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 01 Apr 2007 - 05 Apr 2007
- Location: Denver, Colorado, USA
- Published: 01 April 2007
61 - 80 of 164 results
-
-
Geophysical Technologies To Image Old Mine Works
Authors Kanaan Hanna and Jim PfeifferZapataEngineering, Blackhawk Division performed geophysical void detection demonstrations for the US Department of Labor Mine Safety and Health Administration (MSHA). The objective was to advance current state-of-practices of geophysical technologies for detecting underground mine voids. The presence of old mine works above, adjacent, or below an active mine presents major health and safety hazards to miners who have inadvertently cut into locations with such features. In addition, the presence of abandoned mines or voids beneath roadways and highway structures may greatly impact the performance of the transportation infrastructure in terms of cost and public safety. Roads constructed over abandoned mines are subject to potential differential settlement, subsidence, sinkholes, and/or catastrophic collapse. Thus, there is a need to utilize geophysical imaging technologies to accurately locate old mine works. Several surface and borehole geophysical imaging methods and mapping techniques were employed at a known abandoned coal mine in eastern Illinois to investigate which method best map the location and extent of old works. These methods included: 1) high-resolution seismic (HRS) using compressional P-wave (HRPW) and S-wave (HRSW) reflection collected with 3-D techniques; 2) crosshole seismic tomography (XHT); 3) guided waves; 4) reverse vertical seismic profiling (RVSP); and 5) borehole sonar mapping. In addition, several exploration borings were drilled to confirm the presence of the imaged mine voids. The results indicated that the RVSP is the most viable method to accurately detect the subsurface voids with horizontal accuracy of two to five feet. This method was then applied at several other locations in Colorado with various topographic, geologic, and cultural settings for the same purpose. This paper presents the significant results obtained from the geophysical investigations in Illinois (Hanna, et al, 2006).
-
-
-
Evaluation Of Three-Dimensional Electrical Resistivity Array Types For Optimal Detection Of Voids In Karstic Limestone
Authors James D. Prikryl, Ronald N. McGinnis and Ronald T. GreenElectrical resistivity imaging provides a non-destructive means for detecting the presence of karst features (e.g., caves, solution cavities, and sinkholes) in limestone terrains. To statistically improve delineation of three-dimensional (3-D) heterogeneities, such as caves, a true 3-D electrical resistivity survey using a 3-D interpretation model can be used. When conducting 3-D resistivity investigations in karst terrains, a common problem is determining which of the existing electrode configurations will respond best to material changes in the subsurface, and provides the needed depth and resolution for accurate void delineation. In this study, 3-D electrical resistivity measurements were collected over the site of Dead Deer Cave in Bexar County, Texas, using various electrode configurations (i.e., dipole-dipole and pole-dipole). The entrance to Dead Deer Cave is a pit that connects to a series of vertical and horizontal solution cavities that have
been surveyed to a depth of approximately 30 m. The pit has been filled in with rock and dirt, concealing its exact location. Results of 3-D numeric modeling of the resistivity measurements at Dead Deer Cave indicate that the pole-dipole array configuration provided the needed depth and resolution for locating the cave entrance as well as the shafts and passages that are beneath the surveyed area.
-
-
-
The Use Of Ground Penetrating Radar To Evaluate The Location And Formation Of Sinkholes Associated With A Retention Pond
Authors Craig C. Schuettpelz, Dante Fratta and David J. HartDevelopment and construction over karst often leads to unintended results. In this case study, a retention pond was built in a new subdivision to capture surface runoff and add appeal for potential homeowners. However, water never rose to the proposed level and has drained suddenly and frequently since construction in the year 2000. The failure of the retention pond to perform as designed is due to the presence of carbonate bedrock beneath the site. The bedrock, the Prairie du Chien dolomite, is highly weathered and prone to many relatively small sinkholes. Geophysical surveys were proposed to evaluate the subsurface conditions and to determine the extent of sinkholes below the pond shorelines in an attempt to propose engineering solutions to the problem. Four geophysical surveys were performed: ground penetrating radar (GPR), seismic reflection and refraction, electromagnetics (EM), and subbottom profiling. Although all methods provided subsurface information, the GPR surveys were most useful to site characterization. The GPR surveys show evidence of severely disturbed soil in the subsurface that is associated with sinkhole formation. These surveys help delineate the areas around the retention pond that may produce additional sinkholes and failure and will help to focus remediation efforts.
-
-
-
Advances In Air-Coupled Lamb Wave Scanning
Authors Alex Gibson, Nils Ryden and John S. PopovicsImpact-echo is an effective method for the nondestructive evaluation of in-situ concrete members and has progressively developed over the past 20 years. This study outlines recent advances in the adoption of microphone-based signal acquisition in order to perform rapid non-contact impact echo scanning, in the context of the recently proposed Lamb wave dispersion hypothesis. Various challenges associated with noise control, data acquisition, processing and imaging are addressed. Data obtained from scanning a control slab over a range of source-receiver separations are presented alongside results from traditional point-by-point impact-echo testing. Potential applications of this method include rapid thickness profiling of large structures and
identification of flaws in concrete pavements, reinforced concrete pipes, bridge decks, as well as quality assurance of grouting in post-tensioning tendon ducts.
-
-
-
Application Of Probabilistic Approach To The Solution Of Inverse Problems In Nondestructive Testing And Engineering Geophysics
Authors Rambod Hadidi, Nenad Gucunski and Ali MaherInterpretation of geophysical data often requires the solution of an inverse problem or simply, inversion. Inverse problem is a problem where the observed data is used to infer the characteristics of the system under investigation. There are two general approaches to the solution of inverse problems, deterministic and probabilistic approaches. Traditionally, in engineering geophysics, inversion is carried out using a deterministic approach, where a single set of results is identified as the interpretation outcome. In complex inverse problems, the deterministic solution process is often guided by an interpreter, who uses his information, experience, or judgment to guide the process. The deterministic approach to the solution of inverse problems implicitly assumes that the uncertainties in data and quantitative models are negligible. However, this assumption is not valid in many applications and, consequently, obtaining a single set of results does not provide a complete picture in terms of quantifying the effects of data and/or theoretical uncertainties on the obtained solution. In this paper, a general probabilistic approach to the solution of inverse problems is introduced, which offers the framework required to obtain uncertainty measures and to include some a priori information in the solution process. A technique for the evaluation of the probabilistic solution using Monte Carlo Markov Chains (MCMC) with Neighborhood Algorithm (NA) approximation is introduced and explained. Finally, the application of the presented approach in the health monitoring of transportation infrastructure using non-destructive testing (NDT) is illustrated.
-
-
-
Seismic Modeling of a Rising Mine Water Table
Authors Dirk Orlowsky and Bodo LehmannIn former deep coal mining areas in Germany the mine water table is regulated by a water pump system such that the drinking water at the earth’s surface is not influenced. Nevertheless, in the next years it is planned to reduce the pumping rate in selected areas or to stop the pumps completely. Thus, the mine water table will rise and will effect the hydrogeologic situation at the earth’s surface. To minimise or to avoid critical changes it will be necessary to determine the effects of a rising mine water table in advance. For a detailed forecast the exact depth of the mine water table has to be monitored during the rising process. For the modelling of possible changes at the earth’s surface using the so called box model (Eckart et. al., 2003), a finite element model of the hydrogeologic situation in the Ruhr Area
has been developed. To observe the depth of the mine water table usually old shafts or exploration drill holes are used at selected locations. Nevertheless, there are to less observation stations for a detailed modelling of the complete Ruhr Area so that additional observation locations are needed. To avoid the construction of expensive and complicated drill holes down to more than 1000 m depth an alternative technique to monitor the rising of the mine water table could be the time-lapse seismic (TLS) which is routinely used to monitor the effects of the exploitation of oil and gas deposits.
-
-
-
Stresses Analysis Of The Area Between Aswan And Red Sea Hills, Egypt Using Magnetic And Anisotropy Techniques
Authors Ahmed Saleh and Mahmoud MekkawiThe aim of the present study is to obtain the stress direction using magnetic anisotropy and aeromagnetic interpretations. Representative sixty oriented rock samples have been collected from five sites in the study area. The rocks magnetic properties and magnetic anisotropy analysis have been determined for all the studied samples. The interpretation clearly defined magnetic lineation at all site and anisotropy of magnetic susceptibility (AMS) parameters. The stress direction of the studied area has been determined using magnetic anisotropy and aeromagnetic analysis. The specific objective of the aeromagnetic interpretation is to establish the trend and depth of the structural configuration of the basement rocks.. Horizontal gradient could
to delineate deep sources and enabled tracing several faults that are mainly striking in the E-W direction. Eular deconvolution method has been applied to the aeromagnetic data and provided fast information about depth and trends of the shallower subsurface structures. In agreement with results from AMS interpretation has been estimated and the present stress direction results agree with the geological and tectonic information in Red Sea and Aswan areas. Keyword: magnetic anisotropy, aeromagnetic interpretation and stresses analysis.
-
-
-
Combining Multiple Seismic And Ground Penetrating Radar Techniques To Analyze Geologic Controls Of Riparian Meadow Complexes In The Central Great Basin, Nevada Usa
Riparian meadow systems in the Central Great Basin are of interest because they support the majority of ecosystem diversity in the region. The riparian meadows are highly dependent upon
groundwater levels, thereby making them vulnerable to fluctuations. These systems are actively degrading due to incision of the streams, resulting in a lowered water table and modification of the associated ecosystems. Geologic controls, such as bedrock geometry and sediment variability, are important in the meadows because of their control on the overall system. The current hypothesis is that the sediments associated with side-valley alluvial fans and fault-related bedrock steps interact to constrict ground water flow. Seismic reflection data and seismic refraction tomography data were collected to analyze bedrock structure and topography from 10 to 80 meters depth, while ground penetrating radar (GPR) data were collected to determine the stratigraphic variability in the upper 10 meters. These data were integrated to provide a comprehensive interpretation of the upper 80 meters of the subsurface. Seismic reflection data were processed to identify the bedrock surface. This surface was then correlated with the seismic refraction tomography to extend the bedrock surface across the meadow complexes. The large
volume of GPR data were interpreted by classifying radar facies based on the characteristics of the radar reflectors. These facies (in conjunction with borehole information) confirm and extend areas of alluvial fan related sediment distribution. Integration of these three geophysical techniques is advantageous because they provide more information than could be obtained with the individual techniques.
-
-
-
3-D Electrical Resistivity Imaging (Eri) Of A Potential Mine Stoop
More Less3-D electrical resistivity imaging (ERI) survey of a recently and twice-repaired sinkhole at a site in Chester County, PA reveals a small localized opening in the top of rock suggestive of a potential sinkhole throat. The area is underlain by carbonate rocks prone to sink activity. It is also located fairly close to the Wheatley Mine District, a series of lead, zinc, and copper mines that date back to the 1800's, and that have operated periodically up until the 1920's. Re-fined imaging of the 3-D data shows that the small opening is a top of rock expression of an inclined, cylindrical-shaped structure that looks like a mine stoop. The approximately 3 meter wide opening is associated with a linear depression in the rock surface that may represent a haul road and/or man-made drainage to control storm-water runoff. The proximity of the site to the former mining district, coupled with the mine-like structure observed in the 3-D data strongly suggest that ground failure was not triggered by sink activity but rather by a mine collapse.
-
-
-
Defeat The Dragon: Coal Fires Between Self Ignition And Fire Fighting
Authors Manfred W. Wuttke, Stefan Weßling and Winfried KesselsSpontaneous coal fires in near surface coal seams are a worldwide recognized problem. They are destroying coal as a resource and emit climate relevant gases like CO2 both in considerable amounts. While the extinction of such fires is a most desirable goal, the estimation of the actual input of greenhouse gases into the atmosphere is of great interest especially in the context of the Kyoto protocol as such values are needed as baseline for the Clean Development Mechanism policies. Under the framework of the Sino-German Coalfire research project we develop numerical models of such coal fires. The aim of our calculations is first to understand the governing physical and chemical processes that are relevant for the whole combustion process. Based on such gained insights we study the coal fire spreading along the seams for typical situations. From these scenario calculations we can deduce informations needed to support the CDM baseline estimation and to assess the progress of fire extinguishing efforts like water injection and surface covering to dissipate the heat and suffocate the fire. We present case studies using the finite-element-code ROCKFLOW applied to realistic geometries based on field observations in the Shenhua Group Coal Mining Area Wuda (Inner Mongolia, PR China).
-
-
-
Geophysical Investigation Of The Success Dam Foundation: An Overview
Authors Lewis E. Hunter, Michael H. Powers, Seth Haines, Theodore Asch and Bethany L. BurtonSuccess Dam is a zoned earth-fill embankment located about 70 miles northeast of Bakersfield, CA. Stability analyses indicate that there is a potential for large-scale deformation of the dam during relatively low levels of earthquake shaking. At least three earthquakes in the past 150 years, and prior to dam construction, are believed to have been large enough to create a dam failure. To better understand material behavior, the U.S. Army Corps of Engineers has been investigating properties of the dam and its foundation. This includes extensive field explorations and detailed engineering studies using a variety of analytical techniques to estimate the response of the dam and foundation to earthquake shaking. Although a large amount of data have been acquired since 1992, these data are largely point data from borings. A geophysical investigation was designed to provide a continuous image of the foundation toe. This investigation employed direct-current (DC) resistivity, seismic refraction tomography (P- and S-wave), audio-magnetotellurics (AMT), and self-potential (SP). The purpose of the DC resistivity and seismic refraction tomography was to produce 2-D imagery across the foundation to investigate depth to bedrock and the occurrence of beds potentially susceptible to liquefaction. DC resistivity was used to look at the conductivity relationships in the subsurface. The resistivity data produced a higher-resolution image relative to seismic refraction tomography, which looks at compressional and shear properties of the material. AMT was applied to look considerably deeper (several 100s of m) in order to confirm depth to bedrock and investigate for deep faults. The goal of this paper is to provide technical background on the site and to highlight how these data have been used by the engineers in redesigning the new dam. Specific details on the geophysical methods are presented by the co-authors in two other papers in this session (Asch et al., 2007; Powers et al., 2007).
-
-
-
Using Airborne Electromagnetic Data To Construct A Sediment Textural Model And Salt Budget For Use In Hydrogeological Applications: A Case Study From New South Wales, Australia
More LessThis paper reports on the research to quantify salt budgets and sediment and saprolite textures in a sub-catchment of the Lachlan Catchment, NSW. Data were obtained from airborne electromagnetic (AEM), ground and borehole electromagnetic (EM) data, and laboratory petrophysical and geochemical studies. Algorithms have been derived from statistical relationships between AEM conductivity data, down-hole induction logs and petrophysical attributes. These algorithms are then used in ArcGIS™ software to model the salt budgets and textural distribution model.
-
-
-
Detection Of Subsurface Diesel Contamination Using Electromagnetic Induction Geophysical Techniques
Authors Jeffrey S. Cooper and Song JinDelineating the extent of petroleum hydrocarbon spills/plumes in subsurface soil and groundwater is typically done by soil boring and installation of monitoring wells. These methods are labor intensive and expensive. Site heterogeneity tends to introduce errors. In this study, we investigated electromagnetic induction survey as an alternative technique to map the extent of subsurface hydrocarbons in a nondestructive, noninvasive way. This study was designed to demonstrate the effectiveness and accuracy of such a survey in its response to subsurface diesel contamination. Geophysical surveys were undertaken at two mining sites near Gillette, Wyoming, using a EM34-XL™ unit. Samples from monitoring wells at the two sites were
correlated to the survey results for validation. Data from the survey well matched the readings from sample analysis. Results from this study indicate that electromagnetic induction surveys could be an effective tool in mapping the subsurface petroleum contaminants.
-
-
-
Electrical Resistivity Imaging To Monitor A Simulated Leak From An Underground Storage Tank At A Radiological Waste Facility
Authors Brian D. Cubbage, Dale F. Rucker, Marc T. Levitt and Shawn M. CalendineAn electrical resistivity survey was performed during a simulated leak near an underground storage tank, located on the Hanford Site in eastern Washington. The resistivity data collection involved eight surface arrays oriented along orthogonal lines and 41 steel cased wells completed in the vadose zone in the S Tank Farm. The monitoring included three phases to determine the effects of fluid migration: (1) pre leak to establish baseline conditions, (2) mid leak using surface arrays, and (3) post leak survey, conducted several weeks after the cessation of the injection, to determine the simulated leak’s migration.
-
-
-
Case Study: Resistivity Variation With Biodegradation In A Refinery Oil Dump In Brazil
Authors Guilherme P. Castilho, Daniel F.S. Maia and Maria C. PessoaThe geoelectrical response of an oil contaminated site has been the focus of several scientific studies over the last years, mainly when considering the time-related changes of the oil physical
properties such as it's resistivity due to bacterial degradation. The site under study is located at an oil refinery in Brazil and was used as hydrocarbonate residue dump until two decades ago. An environmental diagnostic request was made by the refinery owner in order to investigate the contamination extension and to plan the area remediation. The contaminated region presented an electrical resistivity two orders of magnitude below the normal background for the area. These results combined with TPH (Total Petroleum Hydrocarbon) levels analysis confirmed previously made laboratory measurements that asserted the decrease in electrical resistivity with biodegradation.
-
-
-
Integrated Geophysical Approach For Mapping An Active Landslide In Himalaya: A Case Study
Authors Rambhatla G. Sastry, Suman K. Mondal, Param K. Gautam and Ashok K. PachauriA gravimetric survey was carried out over an active landslide area, followed by 2D multielectrode resistivity surveys in order to understand the present landslide in terms of failure surfaces and
predict its future behavior. Preliminary gravity survey has delineated a number of failure surfaces or faults within the active landslide zone and its neighboring area. The electrical resistivity profiles were conducted across the inferred faults lines for confirmation and for deciphering subsurface lithology.
-
-
-
Wide Area Assessment Of Munitions-Contaminated Sites
Authors H.H. Nelson and A.M. AndrewsIn response to a recent Defense Science Board Task Force report and Congressional direction, the Environmental Security Technology Certification Program initiated a Wide Area Assessment Pilot Program in 2005 with demonstrations at three Formerly Used Defense Sites. In 2006, the Pilot Program was expanded to include three additional sites with different characteristics. All data collection, interpretation, and validation efforts have been completed at five of the sites and data collection and analysis is ongoing at the former Camp Beale in CA. In this paper we briefly describe the technologies used in the demonstrations, present an overview of the survey data collected during the demonstrations, discuss the validation activities undertaken, and close by drawing conclusions on the applicability of this process to other potentially-contaminated sites.
-
-
-
Determination Of Soil Magnetic Susceptibility From Electromagnetic Induction Measurements
Authors Ryan E. North and Janet E. SimmsKnowledge of the magnetic susceptibility of soils is of primary importance in three subsets of geophysics: archaeology, landmine detection and unexploded ordnance detection. Current methodology involves making a number of in-situ point measurements or collecting soil samples at point locations for later laboratory analysis. Magnetic susceptibility data would be more useful if it could be measured at a higher spatial density, both horizontally and vertically. The long term goal of this project is to invert electromagnetic induction (EMI) data to determine the spatial distribution of magnetic susceptibility. As an initial study, in-situ magnetic susceptibility measurements were collected with three instruments (ZH Instruments SM-30, Geonics EM38B and Bartington MS2 D & F) at two meter spacing along a 100 meter transect. Surface soil samples were collected at each location and analyzed in the laboratory with the Bartington MS2B. Electrical resistivity data (AGI SuperSting R8) and EMI data (DualEM-4S, Geonics EM31 & EM38B, and Geophex GEM-2) were also collected along the line. The question to be answered is, can in-phase EMI data be used as a proxy for magnetic susceptibility point measurements or will a more advance inversion model be required to extract this information.
-
-
-
Airborne And Ground-Based Electromagnetic Investigation Of The Freshwater Potential In Tsunami-Hit Areas Of Northern Sumatra
Authors Annika Steuer, Bernhard Siemon and Detlef EberleThe earthquake and the tsunami event on December 26th, 2004, damaged the freshwater supply system in the coastal areas of northern Sumatra. Therefore, the German-Indonesian HELicopter Project ACEH (Siemon et al. 2007) was initiated to assist the Indonesian Government in their efforts to plan and realize a sustainable reconstruction of community infrastructure (like freshwater supply) by providing geophysical and hydrogeological data serving as a base for spatial planning. After two successful airborne geophysical surveys funded by the Federal Institute for Geosciences and Natural Resources (BGR) and conducted by the BGR airborne group on the north coast near the city of Banda Aceh and along the west coast between the towns of Calang and Meulaboh from August to October 2005, Coca Cola Foundation Indonesia (CCFI) funded an additional survey on the north-east coast around the town of Sigli (Figure 1).
-
-
-
Contaminants Evaluation As Indicators Of Water Quality In Ago-Iwoye, Southwestern, Nigeria
More LessThe study evaluates some functional parameters of well water in a densely populated university town, Ago-Iwoye, South-western, Nigeria. Well water samples were collected at ten sites across the town. Analysis of the presence of Coliform count, Salmonella count, standard plate count, physicochemical properties (14 elements and 2 physical parameters) as indicators of water contaminants in the wells in the study area were carried out on the water samples. 40 % of the well samples were contaminated with coliform while 20% were contaminated with salmonella indicating the source of contamination (fecal contaminant). Further analysis revealed that most of the wells have their mineral values within the tolerant level according to WHO standard, however the two most toxic chemicals from the recommendations of WHO were identified in wells 2,3,5 and 10 with values exceeding tolerant level of 0.05 mg/l for lead and 2.56mg/l value for nitrate in well 2.Results confirm the presence of bacteria growth of such samples, highly dangerous to life. Also wells 2, 4, & 8 were contaminated with excess concentration of Iron (Fe) mineral which could make the water tasty and have bacteria growth while wells 1, 2, 3, & 7 have excess concentrations of Copper (Cu) mineral which could cause a stringent taste.
-