Browsing by Author "Westman, Erik C."
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- Analysis of Seismic Signatures Generated from Controlled Methane and Coal Dust Explosions in an Underground MineMurphy, Michael M. (Virginia Tech, 2008-11-07)Examination of seismic records during the time interval of the Sago Mine disaster in 2006 revealed a small amplitude signal possibly associated with an event in the mine. Although the epicenter of the signature was located in the vicinity where the explosion occurred, it could not be unequivocally attributed to the explosion. More needs to be understood about the seismicity from mine explosions in order to properly interpret critical seismic information. A seismic monitoring system located at NIOSH's Lake Lynn Experimental Mine has monitored nineteen experimental methane and dust based explosions. The objective of the study was to analyze seismic signatures generated by the methane and dust explosions to begin understanding their characteristics at different distances away from the source. The seismic signatures from these different events were analyzed using standard waveform analysis procedures in order to estimate the moment magnitude and radiated seismic energy. The procedures used to analyze the data were conducted using self-produced programs not available with existing commercial software. The signatures of the explosions were found to be extremely complex due a combination of mine geometry and experimental design, both of which could not be controlled for the purposes of the study. Geophones located approximately 600 m (1970 ft) and over from the source collected limited data because of the attenuation of the seismic waves generated by the methane explosion. A combination of the methods used to characterize the seismic signatures allowed for differentiation between experimental designs and the size of the explosion. The factors having the largest impact on the signatures were the mine geometry, size of the methane explosion, construction of the mine seal and location of the mine seal. A relationship was derived to correlate the radiated seismic energy to the size of the explosion. Recommendations were made, based upon the limitations of this study, on methods for better collection of seismic data in the future.
- Analysis of Wireless Tiltmeters for Ground Stability MonitoringLogan, Kenneth Scott (Virginia Tech, 2008-04-23)Tiltmeters can be used in the mining environment to monitor slope stability by making use of gravitational force to measure angles of inclination relative to horizontal. Tiltmeters typically use accelerometers, which output a voltage measurement that can be related to angle of tilt. Though wireless tiltmeters already exist today, they lack certain ruggedness and sensitivity preventing use in mines. The purpose of this project was to investigate the feasibility of using already existing wireless tiltmeters in the mining setting. Additionally, a new wireless tiltmeter was designed which could be specially tailored for the needs of monitoring hazardous rock bodies in both surface and underground mines. By recording angles of any slope, either in a surface mine or underground, over extended periods of time, changes in readings can infer instabilities in the rock mass underlying the slope being measured. By placing many tiltmeters in a mesh on a surface slope or underground roof, rib, or other face, the entire surface can be monitored. Compared to the measurements of a single point using one instrument, a dense network can be extremely useful in detecting rock movement. Many monitoring techniques are in use already in mines. Traditional methods of monitoring, though undeniably useful, are often time consuming. By utilizing wireless devices that transmit data back to a single location, data acquisition and analysis time can be minimized, saving the mine employee hours as well as down time. As surface mines continue to deepen, and underground mines continue to progress further from the surface, the extent of necessary monitoring continues to increase: this widening range will require greater time for proper monitoring, unless an automated system is implemented. With proper wireless equipment, real time monitoring of an entire mine is possible.
- Application of Background Oriented Schlieren (BOS) in Underground Mine VentilationJong, Edmund Chime (Virginia Tech, 2011-04-21)The schlieren technique describes an optical analysis method designed to enhance light distortions caused by air movement. The ability to visualize gas flows has significant implications for analyzing underground mine ventilation systems. Currently, the widely utilized traditional schlieren methods are impractical underground due to complex equipment and design requirements. Background oriented schlieren (BOS) provides a solution to this problem. BOS requires two primary components, a professional quality digital camera and a schlieren background. A schlieren background is composed of a varying contrast repetitive pattern, such as black and white stripes or dots. This background allows the camera's sensor to capture the minor light diffractions that are caused by transparent inhomogeneous gases through image correlation. This paper investigates a possible means of mitigating some of the major problems associated with surveying underground mine ventilation systems with the BOS method. BOS is an imaging technique first introduced in 1999 that allows the visualization of flowing inhomogeneous transparent media. In ventilation surveys, BOS can be used to attain qualitative data about airflows in complex areas and methane emissions from coal. The acquisition of such data would not only enhance the understanding of mine ventilation but also improve the accuracy of ventilation surveys. As an example, surveys can benefit from small scale BOS investigations around fans, regulators, overcasts, and critical junctions to identify effective data gathering positions. Regular inspections of controls and methane monitoring points could also be improved by the systematic nature of BOS. Computer programs could process images of each location identically regardless of quantity. BOS can then serve as a check to identify items that were overlooked during the routine inspection. Despite the potential of BOS for ventilation analysis, several limitations still exist. These issues are sensitivity threshold and quantification of flow data. This paper specifically examines the qualitative potential of the BOS technique for imaging various underground ventilation flows and outlines initial experimental efforts used for the evaluation. Three primary experiments were conducted to evaluate BOS as a potential qualitative analysis technique for underground mine ventilation. The first experiment used BOS to image of flow induced by an axial vane fan and an axial flow fan using an artificial background and an imitation rock background. This experiment showed that the BOS system was unable to image isothermal airflow from either fan. Heated airflow could be visualized with both fans using the artificial striped background but not with the imitation rock background. The BOS system lacked the sensitivity necessary to image isothermal airflow from the two fans. The focus of the overall BOS study was changed to explore higher pressure airflows through a regulator. The second experiment used BOS to image flow through a regulator induced by an axial flow fan using an artificial striped background. The BOS images were compared to ones produced by a traditional schlieren single mirror systems for validation of the BOS experimental design. This experiment was unable to image isothermal airflow through the regulator from either system. However, heated airflow could be visualized by both systems. The BOS and traditional schlieren systems used in this experiment lacked the sensitivity necessary to image isothermal airflow through a regulator. However, the BOS procedures were successfully validated by the ability of both the BOS and traditional schlieren systems to image heated airflows. The focus of the study was changed to explore methane gas emissions. Numerous mining industry techniques already exist to quantify methane content. However, methane content is different from the actual methane emission rate of exposed coal. Emission rates have been modeled using numerical simulation techniques, but the complexity of the methane migration mechanism still requires physical data to achieve higher accuracy. The third experiment investigated the feasibility of using the BOS technique for imaging methane flow by imaging methane emission from a porous medium. Laboratory grade methane was directly injected into a Brea sandstone core sample using a flexible tube. The BOS system was successfully able to image methane desorption in this study. A repeating pattern consisting of alternating black and white stripes served as the schlieren background for the Nikon D700 camera. The ability to image methane emission even at low injection pressures (i.e. 20 psi) demonstrates that actual methane desorption from coal can potentially be imaged. This result can only be conjectured because of a lack of research in the area of methane emission. Despite this issue, the experimental results suggest that BOS can be feasibly utilized to image methane emissions from coal in an underground mine. The results of the three experiment demonstrated that the potential for large scale implementation of BOS in underground mines does exist. Qualitative BOS information has the potential in the practical sense to optimize the procedures of ventilation surveys and design of ventilation monitoring equipment. For example, images of methane flow in active mining areas can be used to optimize the positioning of auxiliary ventilation equipment to dilute known areas of high methane concentration. BOS images could also be used to re-evaluate the placement of methane monitors on mining equipment to better facilitate the detection of dangerous methane concentrations in active mining areas. For these reasons, further investigation into the BOS technique for use in imaging underground airflows with differential temperatures and methane emissions in underground coal mines is suggested as an addendum to this study.
- Application of Double-Difference Seismic Tomography to Carbon Sequestration Monitoring at the Aneth Oil Field, UtahSlaker, Brent; Westman, Erik C.; Luxbacher, Kramer Davis; Ripepi, Nino (MDPI, 2013-10-23)Double difference seismic tomography was performed using travel time data from a carbon sequestration site at the Aneth oil field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting (MVA) of sequestered CO2. A total of 1211 seismic events were recorded from a borehole array consisting of 23 geophones. Artificial velocity models were created to determine the likelihood of detecting a CO2 plume with an unfavorable event and receiver arrangement. In tests involving artificially modeled ray paths through a velocity model, ideal event and receiver arrangements clearly show velocity reductions. When incorporating the unfavorable event and station locations from the Aneth Unit into synthetic models, the ability to detect velocity reductions is greatly diminished. Using the actual, recorded travel times, the Aneth Unit results show differences between a synthetic baseline model and the travel times obtained in the field, but the differences do not clearly indicate a region of injected CO2. MVA accuracy and precision may be improved through the use of a receiver array that provides more comprehensive ray path coverage, and a more detailed baseline velocity model.
- Application of Electromagnetic Methods to Identify and Characterize Sub-surface Structures Associated with the Coles Hill Uranium DepositWhitney, Joshua Andrew (Virginia Tech, 2009-04-22)The Coles Hill uranium deposit in Pittsylvania County, Virginia represents the largest unmined uranium resource in the United States, with an estimated resource of 110 million pounds of U3O8 in place with a cutoff grade of 0.025 wt% U3O8. The deposit is localized along a geologic unit that parallels the Chatham Fault, which separates the Triassic Danville Basin to the east from the older crystalline rocks to the west. The location of the Chatham Fault is important to understanding distribution of ore and for developing an effective mine plan. In this study the Chatham Fault location has been inferred from ground conductivity and ground penetrating radar (GPR) surveys. Anomalies in the data are consistent with previously mapped fault locations based on drillhole and geophysical data, such as gravity and magnetic surveys, collected in the 1980s. These results confirm that the strike of the Chatham Fault is approximately N40ºE and dips to the southeast with dip values ranging from 70º, in the northeast, to 50º, in the southwest.
- Applications of Double-Difference Tomography for a Deep Hard Rock MineKerr, Jeffrey Bryan (Virginia Tech, 2011-11-16)Seismicity at a deep hard rock mine can be a precursor to ground failure events. Seismicity data can be used in double-difference tomography, which produce tomograms showing velocity distributions in the rock mass that can be used to infer relative stress of the rock mass. The data set used for the double-difference tomography inversion was from Creighton Mine in Sudbury, Ontario, Canada, and consisted of two months of data averaging 150 microseismic events per day. Three separate studies were conducted to evaluate the applications of double-difference tomography on a deep hard rock mine. These studies produced mine scale tomograms, stope scale tomograms of two active stopes, and stope scale tomograms for a cluster of events. TomoDD was used for the tomographic inversion, with other commercial programs used to view the results. All three studies produced results consistent with prior mine knowledge and basic concepts of rock mass stress redistribution. Mine scale tomograms accurately displayed a low velocity where the mined ore body is known to be with adjacent high velocity, stope scale tomograms of the two stopes both correctly demonstrated a low velocity relaxed zone near the stope following a production blast, and stope scale tomograms of an event cluster displayed consistency in results for two clusters in periods before, during, and after each cluster. The three studies show that double-difference tomography is a promising tool for observing rock mass stress redistribution that provides a baseline evaluation for the potential uses of the technology in a deep hard rock mine.
- Applications of Queuing Theory for Open-Pit Truck/Shovel Haulage SystemsMay, Meredith Augusta (Virginia Tech, 2013-01-29)Surface mining is the most common mining method worldwide, and open pit mining accounts for more than 60% of all surface output. Haulage costs account for as much as 60% of the total operating cost for these types of mines, so it is desirable to maintain an efficient haulage system. As the size of the haulage fleet being used increases, shovel productivity increases and truck productivity decreases, so an effective fleet size must be chosen that will effectively utilize all pieces of equipment. One method of fleet selection involves the application of queuing theory to the haul cycle. Queuing theory was developed to model systems that provide service for randomly arising demands and predict the behavior of such systems. A queuing system is one in which customers arrive for service, wait for service if it is not immediately available, and move on to the next server or exit the system once they have been serviced. Most mining haul routes consist of four main components: loading, loaded hauling, dumping, and unloaded hauling to return to the loader. These components can be modeled together as servers in one cyclic queuing network, or independently as individual service channels. Data from a large open pit gold mine are analyzed and applied to a multichannel queuing model representative of the loading process of the haul cycle. The outputs of the model are compared against the actual truck data to evaluate the validity of the queuing model developed.
- The Assessment of Sonic Waves and Tracer Gases as Non-Destructive Testing (NDT) Methods for In-Situ Underground Mine SealsBrashear, Kyle Thomas (Virginia Tech, 2014-09-17)Since the MINER Act of 2006, the minimum static load of in-situ underground mine seals has been increased from 20-psi to either 50-psi if monitoring is conducted or 120-psi if left unmonitored. These minimum strength requirements in seals must be designed, built, and maintained throughout the lifetime of the seal. Due to this, it has become necessary to assess the effectiveness of non-destructive testing (NDT) technologies to determine seal integrity, which in this case, are explored using sonic waves and tracer gases. Through both small and large scale testing, two NDT methods were evaluated on their abilities to determine integrity of the seal. A sonic wave technique to observe a change in wave velocity to identify faults within the seal material. As a NDT method, tracer gases may be used as a potential indicator of a connection between both sides of the seal material through a series of faults and cracks within the material itself. This paper reviews the history of underground mine seals and discusses the overall assessment of sonic waves and tracer gases to serve as NDT methods for estimating the integrity of these seals.
- Back-analysis methods for optimal tunnel designVardakos, Sotirios (Virginia Tech, 2007-01-24)A fundamental element of the observational method in geotechnical engineering practice is the utilization of a carefully laid out performance monitoring system which provides rapid insight of critical behavioral trends of the work. Especially in tunnels, this is of paramount importance when the contractual arrangements allow an adaptive tunnel support design during construction such as the NATM approach. Utilization of measurements can reveal important aspects of the ground-support interaction, warning of potential problems, and design optimization and forecasting of future behavior of the underground work. The term back-analysis involves all the necessary procedures so that a predicted simulation yields results as close as possible to the observed behavior. This research aims in a better understanding of the back-analysis methodologies by examining both simplified approaches of tunnel response prediction but also more complex numerical methods. Today a wealth of monitoring techniques is available for tunnel monitoring. Progress has also been recorded in the area of back-analysis in geotechnical engineering by various researchers. One of the most frequently encountered questions in this reverse engineering type of work is the uniqueness of the final solution. When possible errors are incorporated during data acquisition, the back analysis problem becomes formidable. Up to the present, various researchers have presented back-analysis schemes, often coupled with numerical methods such as the Finite Element Method, and in some cases the more general approach of neural networks has been applied. The present research focuses on the application of back-analysis techniques that are applicable to various conditions and are directly coupled with a widely available numerical program. Different methods are discussed and examples are given. The strength and importance of global optimization is introduced for geotechnical engineering applications along with the novel implementation of two global optimization algorithms in geotechnical parameter identification. The techniques developed are applied to the back-analysis of a modern NATM highway tunnel in China and the results are discussed.
- Blasting Design Using Fracture Toughness and Image Analysis of the Bench Face and MuckpileKim, Kwangmin (Virginia Tech, 2006-07-21)Few studies of blasting exist because of difficulties in obtaining reliable fragmentation data or even obtaining consistent blasting results. Many researchers have attempted to predict blast fragmentation using the Kuz-Ram model, an empirical fragmentation model suggested by Cunningham. The purpose of this study is to develop an empirical model to relate specific explosives energy (ESE) to blasting fragmentation reduction ratio (RR) and rock fracture toughness (KIC). The reduction ratio was obtained by analyzing the bench face block size distribution and the muck fragment size distribution using image analysis. The fracture toughness was determined using the Edge Notched Disk Wedge Splitting test. Blasting data from twelve (12) blasts at four (4) different quarries were analyzed. Based on this data set, an empirical relationship, ESE=11.7 RR801.202 KIC4.14 has been developed. Using this relationship, based on the predicted blasting energy input for a desired eighty-percent passing (P80) muckpile fragment size the burden and spacing may be determined.
- Building, Updating and Verifying Fracture Models in Real Time for Hard Rock TunnelingDecker, Jeramy Bruyn (Virginia Tech, 2007-04-20)Fractures and fracture networks govern the mechanical and fluid flow behavior of rock masses. Tunneling and other rock mechanics applications therefore require the characterization of rock fractures based on geological data. Field investigations produce only a limited amount of data from boreholes, outcrops, cut slopes, and geophysical surveys. In tunneling, the process of excavation creates a priceless opportunity to gather more data during construction. Typically, however, these data are not utilized due to the impedance of sampling and analysis on the flow of construction, and safety concerns with sampling within unlined tunnel sections. However, the use of this additional data would increase the overall safety, quality, and cost savings of tunneling. This study deals with several aspects of the above, with the goal of creating methods and tools to allow engineers and geologists to gather and analysis fracture data in tunnels without interrupting the excavation and without compromising safety. Distribution-independent trace density and mean trace length estimators are developed using principles of stereology. An optimization technique is developed utilizing Differential Evolution to infer fracture size and shape from trace data obtained on two or more nonparallel sampling planes. A method of producing nearly bias free empirical trace length CDF's is also introduced. These new methods and tools were validated using Monte Carlo simulations. A field study was conducted in an existing tunnel allowing the above methods and tools to be further validated and tested. A relational database was developed to aid in storage, retrieval, and analysis of field data. Fracture models were built and updated using fracture data from within the tunnel. Utilization of state of the art imaging techniques allowed for remote sampling and analysis, which were enhanced by the use of 3d visualization techniques.
- Carbon Dioxide Storage in Coal Seams with Enhanced Coalbed Methane Recovery: Geologic Evaluation, Capacity Assessment and Field Validation of the Central Appalachian BasinRipepi, Nino Samuel (Virginia Tech, 2009-08-03)The mitigation of greenhouse gas emissions and enhanced recovery of coalbed methane are benefits to sequestering carbon dioxide in coal seams. This is possible because of the affinity of coal to preferentially adsorb carbon dioxide over methane. Coalbed methane is the most significant natural gas reserve in central Appalachia and currently is economically produced in many fields in the Basin. This thesis documents research that assesses the capacity of coal seams in the Central Appalachian Basin to store carbon dioxide and verifies the assessment through a field validation test. This research allowed for the first detailed assessment of the capacity for coal seams in the Central Appalachian Basin to store carbon dioxide and enhance coalbed methane recovery. This assessment indicates that more than 1.3 billion tons of carbon dioxide can be sequestered, while increasing coalbed methane reserves by as much as 2.5 trillion cubic feet. As many of the coalbed methane fields are approaching maturity, carbon sequestration and enhanced coalbed methane recovery has the potential to add significant recoverable reserves and extend the life of these fields. As part of this research, one thousand tons of carbon dioxide was successfully injected into a coalbed methane well in Russell County, Virginia as the first carbon dioxide injection test in the Appalachian coalfields. Research from the field validation test identified important injection parameters and vital monitoring technologies that will be applicable to commercial-scale deployment. Results from the injection test and subsequently returning the well to production, confirm that fractured coal seams have the potential to sequester carbon dioxide and increase methane production. It was demonstrated through the use of perfluorocarbon tracers that there is a connection through the coal matrix between the injection well and surrounding producing gas wells. This connection is a cause for concern because it is a path for the carbon dioxide to migrate to the producing wells. The thesis concludes by presenting options for mitigating carbon dioxide breakthrough in commercial-scale injection projects.
- Carbon Monoxide Generation and Transport from Compartment FiresWieczorek, Christopher John (Virginia Tech, 2003-05-23)The aim of the present research was to gain a better understanding of the species generation and transport from enclosure fires. The species generation experiments were conducted with a half-scale ISO 9705 enclosure with three different ventilation conditions and heat release rates ranging from 50 kW to 500 kW. The transport study was conducted with a 6.1 m long hallway connected to the compartment in a head-on configuration. All measurements were performed at the compartment or hallway exit plane during the steady-state period of the fire. Measurements included species mole fractions of oxygen, carbon dioxide, carbon monoxide, and unburned hydrocarbons, along with gas pressure (used to determine gas velocities) and gas temperatures. Species mappings performed at the exit plane of the compartment indicated that the exiting species are not spatially uniform. Horizontal and vertical gradients in the species mole fractions were observed for all ventilation conditions and heat release rates examined. Predictive techniques developed previously were applied to the data obtained in the present study and were determined to be inappropriate for situations were the plume equivalence ratio was not equal to the global equivalence ratio. A new methodology for predicting species levels at the exit plane of an enclosure was developed. The proposed methodology correlates the species yields based on the combustion within the compartment as a function of a non-dimensional heat release rate. The non-dimensional heat release rate is based on the fuel load and geometrical parameters of the enclosure. The present methodology in applicable to situations where a well-mixed uniform layer is not present and the overall global conditions are of interest. Species transport to remote locations was also examined. Experiments were conducted with the baseline ventilation at x = 0 m (the compartment/hallway interface) and three different ventilation conditions at x = 6.1 m (end of hallway). The three ventilation conditions consisted of the narrow, baseline, and wide doorways. Experiments were conducted for heat release rates of 85 kW, 127 kW, and 150 kW. The results from the tests indicated that, for over-ventilated compartment fires, the hallway and hallway ventilation had no impact on the species generation within the compartment. This allows the correlations developed from the compartment study to be applied to more complex scenarios. Differences in species mole fractions between x = 0 m and x = 6.1 m were shown to be a result of air entrainment into the upper layer within the hallway, which acted as a dilutent or as a source of oxygen for further oxidation reactions. For non-dimensional heat release rates less than 1.0, the reduction in carbon monoxide levels along the hallway was a result of dilution, while for non-dimensional heat release rates greater than or equal to 1.0 the reduction in carbon monoxide levels along the hallway was a combination of dilution and further oxidation reactions.
- A Characterization and Determination of the Coal Reserves and Resources of Southwest VirginiaWestman, Erik C. (Virginia Tech, 1999-04-14)Coal mining and timber are the two primary industries supporting the people of Southwest Virginia. Coal mining has occurred for more than 100 years, but production has dropped since reaching a peak in 1990. In order to properly plan with remaining coal production a study was conducted to characterize and estimate coal resources. Seam thickness was found to be the parameter which most influenced resource levels. An economic model was developed to determine which portion of the reserves could economically be extracted. It was found that 3.95 billion tons, or 14% of the remaining resource, is economic under current mining conditions. More than 60% of these reserves, however, are in deep seams which require shafts to be constructed prior to initiation of mining.
- Column-Supported Embankments: Full-Scale Tests and Design RecommendationsSloan, Joel Andrew (Virginia Tech, 2011-05-26)When an embankment is to be constructed over ground that is too soft or compressible to adequately support the embankment, columns of strong material can be placed in the soft ground to provide the necessary support by transferring the embankment load to a firm stratum. This technology is known as column-supported embankments (CSEs). A geosynthetic-reinforced load transfer platform (LTP) or bridging layer may be constructed immediately above the columns to help transfer the load from the embankment to the columns. There are two principal reasons to use CSEs: 1) accelerated construction compared to more conventional construction methods such as prefabricated vertical drains (PVDs) or staged construction, and 2) protection of adjacent facilities from distress, such as settlement of existing pavements when a roadway is being widened. One of the most significant obstacles limiting the use of CSEs is the lack of a standard design procedure which has been properly validated. This report and the testing described herein were undertaken to help resolve some of the uncertainty regarding CSE design procedures in light of the advantages of the CSE technology and potential for significant contributions to the Strategic Highway Research Program, which include accelerated construction and long-lived facilities. Twelve design/analysis procedures are described in this report, and ratings are assigned based on information available in the literature. A test facility was constructed and the facility, instrumentation, materials, equipment, and test procedures are described. A total of 5 CSE tests were conducted with 2 ft diameter columns in a square array. The first test had a column center-to-center spacing of 10 ft and the remaining four tests had center-to-center spacings of 6 ft. The Adapted Terzaghi Method of determining the vertical stress on the geosynthetic reinforcement and the Parabolic Method of determining the tension in the geosynthetic reinforcement provide the best agreement with the test results. The tests also illustrate the importance of soft soil support in CSE performance and behavior. A generalized formulation of the Adapted Terzaghi Method for any column/unit cell geometry and two layers of embankment fill is presented, and two new formulations of the Parabolic Method for triangular arrangements is described. A recommended design procedure is presented which includes use of the GeogridBridge Excel workbook described by Filz and Smith (2006, 2007), which was adapted for both square and triangular column arrangements. GeogridBridge uses the Adapted Terzaghi Method and the Parabolic Method in a load-displacement compatibility design approach. For completeness, recommended quality control and quality assurance procedures are also provided, and a new guide specification is presented.
- Computer Vision for Quarry ApplicationsChristie, Gordon A. (Virginia Tech, 2013-05-06)This thesis explores the use of computer vision to facilitate three different processes of a quarry's operation. The first is the blasting process. This is where operators determine where to drill in order to execute an efficient and safe blast. Having an operator manually determine the drilling angles and positions can lead to inefficient and dangerous blasts. By using two cameras, oriented vertically, and separated by a fixed baseline, Structure from Motion techniques can be used to create a scaled 3D model of a bench. This can then be analyzed to provide operators with borehole locations and drilling angles in relation to fixed reference targets. The second process explored is the crushing process, where the rocks pass through different crushers that reduce the rocks into smaller sizes. The crushed rocks are then dropped onto a moving conveyor belt. The maximum dimension of the rocks exiting the crushers should not exceed size thresholds that are specific to each crusher. This thesis presents a 2D vision system capable of estimating the size distribution of the rocks by attempting to segment the rocks in each image. The size distribution, based on the maximum dimension of each rock, is estimated by finding the maximum dimension in the image in pixels and converting that to inches. The third process of the quarry operations explored is where the final product is piled up to form stockpiles. For inventory purposes, operators often carry out a manual estimation of the size of a the stockpile. This thesis presents a vision system capable of providing a more accurate estimate for the size of the stockpile by using Structure from Motion techniques to create a 3D reconstruction. User interaction helps to find the points that are relevant to the stockpile in the resulting point cloud, which are then used to estimate the volume.
- A conceptual protocol for integrating multiple parameters for risk assessment due to induced seismicity in a deep mineGhaychi Afrouz, Setareh; Westman, Erik C.; Dehn, K. K.; Weston, B.; Luxbacher, Kramer Davis (2020-01-01)Typically, the time-dependent b-value has been shown to decrease prior to the occurrence of a higher-magnitude event, thus providing a possible indicator of the timing of a significant event. The Energy Index relates seismic energy to seismic moment and an increase in the Energy Index has been associated with an increase in rock mass stress levels. The distribution of P-wave velocity also indicates rock mass stress levels and is provided from time-lapse passive seismic tomography. Finally, prior studies have correlated an increased production rate (blast rate) to higher stress concentrations, potentially triggering a seismic event. Therefore, Energy Index, P-wave velocity, and blast rate may be correlated to stress levels within the rock mass and may imply the magnitude and timing of an event. In this case study, these parameters are used in a back analysis to define a safety protocol for a deep, narrow-vein, underground mine. A catalog of b-value, Energy Index, P-wave velocity, and mine excavation blasting rate, was developed and integrated as a concept of hazardous thresholds. The combination of these various parameters can be helpful in determining the potential for high-risk times and locations due to induced stress.
- A Data-Driven Approach for the Development of a Decision Making Framework for Geological CO2 Sequestration in Unmineable Coal SeamsMiskovic, Ilija (Virginia Tech, 2011-12-14)In today's energy constrained world, carbon capture and sequestration can play an essential role in mitigating greenhouse gas emissions, while simultaneously maintaining a robust and affordable energy supply. This technology is an end-of-pipe solution that does not contribute to a decrease of the production of greenhouse gases, but is very useful as a transition solution on the way towards other sustainable energy production mechanisms. This research involves the development of a comprehensive decision making framework for assessing the techno-economic feasibility of CO2 sequestration in unmineable coal seams, with the Central Appalachian Basin chosen for analysis due to the availability of empirical data generated through recent characterization and field validation studies. The studies were conducted in order to assess the sequestration capacity of coal seams in the Central Appalachian Basin and their potential for enhanced coal bed methane recovery. The first stage of this research involves assessment of three major sequestration performance parameters: capacity, injectivity, and containment. The assessment is focused on different attributes and reservoir properties, characteristic of deep unmineable coal seams in the Central Appalachian Basin. Quantitative and qualitative conclusions obtained through this review process are used later in the identification of the minimum set of technical information necessary for effective design and development of CO2 storage operations. The second section of this dissertation analyzes economic aspects of CO2 sequestration. This segment of the research uses a real options analysis to evaluate the impact of major sources of uncertainty on the total cost of developing and operating a CCS project in a regulatory environment that expects implementation of carbon taxes, but with uncertainty about the timing of this penalty. Finally, all quantitative and qualitative information generated in the first two stages of this research were used for development of a decision making framework/matrix that summarizes the interactions between major technical and economic parameters and constraints, on the other hand, and their impact on overall feasibility of CO2 sequestration in unmineable coal seams. This framework will provide user with capability to address complex problems in a more systematic way and to analyze the most efficient way to utilize available resources.
- Defining Stress Changes Ahead of a Tunnel Face and Design of a Data Acquisition SystemMurphy, Michael M. (Virginia Tech, 2005-12-13)With increasing world population, demand for underground construction is expected to accelerate in the future. Design of tunnels in rock is still largely empirical, while rock failure in underground mines and tunnel construction continues to claim lives. A seismic method to aid in increasing safety during excavation is tomography. Seismic tomography is a non-invasive technique to map the stress changes induced by mining ahead of the active face. Seismic tomography maps the velocity distributions of elastic waves traveling through a rock mass. The velocity distributions mapped in the tomograms can relate to anomalies in the rock such as fracture zones and highly concentrated stresses. In order to develop a relationship between stress and elastic wave velocity, laboratory tests in a controlled environment are required. In the current study tomographic tests were conducted on Berea sandstone and Five Oaks limestone samples. The stress redistribution in the sandstone samples could be imaged by mapping velocity distributions. On an unconfined test the sandstone sample acted much like a coal mine pillar where the stress redistributes to the least confined area. On a sandstone test where the sample was indented by a steel platen the velocity contrast was seen directly under the load and the velocity remained almost unchanged over the rest of the sample. For the limestone tests, the stress redistribution could not be mapped in the tomograms. The ability to map the stress distribution in the tomograms were attributed to the elastic and non-elastic characteristics of the stress-strain curve. For sandstone, a porous rock, the stress redistribution could be mapped and for limestone, a stiff rock, the stress redistribution could not be mapped. A field data acquisition system to apply tomography to ground control problems in a mine was designed and calibrated. Data acquisition hardware were assembled and programmed in LabVIEW to collect seismic data in a mine. The design of a geophone array that will fit into a miniature 5.08 cm (2 in) diameter borehole is presented.
- Design and Testing of a Laboratory Ultrasonic Data Acquisition System for TomographyJohnson, Wesley Byron (Virginia Tech, 2005-12-02)Geophysical tomography allows for the measurement of stress-induced density changes inside of a rock mass or sample by non-invasive means. Tomography is a non-destructive testing method by which sensors are placed around a sample and energy is introduced into the sample at one sensor while the other sensors receive the energy. This process is repeated around the sample to obtain the desired resolution. The received information is converted by a mathematical transform to obtain a tomogram. This tomogram shows a pixelated distribution of the density within the sample. Each pixel represents an average value at that point. The project discussed in this paper takes the principle of ultrasonic tomography and applies it to geomechanics. A new instrumentation system was designed to allow rapid data collection through varying sample geometries and rock types with a low initial investment. The system is composed of sensors, an ultrasonic pulser, a source switchbox, and analog to digital converters; it is tied together using a LabVIEW virtual instrument. LabVIEW is a graphical development environment for creating test, measurement, and other control applications. Using LabVIEW, virtual instruments (VIs) are created to control or measure a process. In this application LabVIEW was used to create a virtual instrument that was automated to collect the data required to construct a tomogram. Experiments were conducted to calibrate and validate the system for ultrasonic velocity determination and stress redistribution tomography. Calibration was conducted using polymethylmethacrylate (PMMA or Plexiglas) plates. Uniaxial loads were placed on limestone and sandstone samples. The stress-induced density contrasts were then imaged using the acquisition system. The resolution and accuracy of the system is described. The acquisition system presented is a low-cost solution to laboratory geophysical tomography. The ultimate goal of the project is to further the ability to non-invasively image relative stress redistribution in a rock mass, thereby improving the engineer's ability to predict failure.