156 research outputs found

    Ground penetrating radar investigations in Upper Kama potash mines

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    An understanding of the structure and state of the rock mass surrounding underground openings in the potash mines is critically important for safe mining, planning the methods of extraction of an orebody, and preventing the influx of ground water. Continuous common offset ground penetrating radar (GPR) data were acquired in the potash mine operated by the Joint Stock Company (JSC) Silvinit (Russia) as part of an investigation of both pre-existing fractures exposed by mine workings and other anomalous geological structures. During the course of GPR investigation, the electrical properties of salt-bearing units were determined, site-specific data acquisition techniques and object-oriented data processing schemes adapted to the geological and geotechnical environment of the Upper Kama potash deposit were developed, and the methodology of 2-D and 3-D GPR data interpretation using interactive modeling was worked out. Open fractures and fault and fold features were successfully mapped using 2-D and 3-D GPR techniques. FK filtering significantly improved the reliability of fracture detection. Spatial models of mapped fractures were created using 3-D GPR imaging technique. Migration of the georadar data was required to obtain the true geometry of folded salt beds. The results of this GPR-based investigation demonstrate that the ground penetrating radar georadar method is capable of providing valuable information about deformation structures within the evaporite units of the Upper Kama potash deposit --Abstract, page iv

    Geologic Hazards And Roof Stability In Coal Mines

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    The U.S. underground coal miner faces a continuing hazard from the fall of roof. At the root of many injuries and fatalities are weak or defective roof strata. Throughout mining history, millions of miles of entry have provided exposure of every conceivable geologic roof hazard. This report describes the geologic origin, association, and potential danger from the most common hazards. Discussions of weak rock include drawrock, rider coals, head coal, stackrock, and stream valley effects. Discontinuities, or roof defects, are described including, clay veins, slickensides, joints, and paleochannels. A number of examples from U.S. coalfields are used to document geologic structure and associated hazards. Roof fall analysis is a methodology used by NIOSH for hazard recognition and prevention; its application and benefit to the industry are discussed

    Measurements of the electrical properties of coal measure rocks

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    Subsurface imaging technologies are part of the electromagnetic (EM) geophysical methods. EM technologies such as radio imaging method (RIM), ground penetrating radar (GPR), and drill string radar (DSR) have great application potentials in the mining industry.;However, the success for applying the EM methods to subsurface observations is largely dependant on the correct evaluation of the electrical properties (e.g., wave attenuation rate and dielectric constant) of the rocks in the domain of interest. Study of the electrical properties of rocks was performed in order to gain better understanding about their variations across the country. The study was done specifically for rocks associated with coal seams. The findings are to be used for improvement of the exploration capabilities of the electromagnetic (EM) technologies in the mining industry.;A large amount of data was collected and available for use to the potential users via the database that was developed

    Ground penetrating radar technique to locate coal mining related features: case studies in Texas

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    The goal of this research project is to identify the efficacy of the ground penetrating radar (GPR) technique in locating underground coal mine related subsidence features at Malakoff and Bastrop, Texas. The work at Malakoff has been done in collaboration with the Railroad Commission of Texas (RRC). RRC has been carrying out reclamation of abandoned underground coal mines at Malakoff since the early 1990Ă‚s. The history of the specific mining operations (at Malakoff and Bastrop) that took place in the early 1900Ă‚s has been difficult to ascertain; therefore, the use of a geophysical techniques like ground penetrating radar to identify hidden voids and potential subsidence features is vital for future reclamation process. Some of the underground mine workings at the field site have collapsed over time affecting the topography by creating sinkholes. GPR data, employing 25 MHz, 50 MHz and 100 MHz frequency antennae, have been collected in common offset patterns and azimuthal pattern. GPR data indicate the mine tunnels possibly connecting existing sinkholes by radargram hyperbolae that correspond with mine openings observed visually or during reclamation. This study also denotes the importance of understanding the variable physical properties of the stratigraphy, which could lead to false alarms by misinterpretation of the radar signals. Natural and man-made above-ground structures cause obstructions in data collection, and hence an optimal design is required for each survey. RRC successfully ground-truthed the data during its reclamation process. In turn, the acquired geophysical data helped to guide the reclamation. At Bastrop, GPR data along with historical documentation led to the conclusion that coal mining did exist in this region but is not a major concern to the immediate stability and safety of the field site. It can be concluded from both the studies that the GPR technique identifies anomalous shafts/tunnels possibly connecting potential failure

    Hydrogeologic Investigations of Pavement Subsidence in the Cumberland Gap Tunnel

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    Cumberland Gap Tunnel was constructed under Cumberland Gap National Historical Park in 1996 to improve transportation on a segment of U.S. 25E, connecting Kentucky and Tennessee and restoring Cumberland Gap to its historical appearance. The concrete pavement in the tunnel started to subside in 2001. Ground penetrating radar surveys revealed voids in many areas of the limestone roadbed aggregate beneath the pavement. To investigate possible hydrogeologic processes that may have caused favorable conditions for voids to form in the aggregate, we studied geology, groundwater flow, and groundwater chemistry in the tunnel using a variety of methods, including bore drilling, packer test, dye tracing, groundwater- and surface-flow monitoring, water-chemistry modeling, and an aggregate dissolution experiment. The study revealed that the aggregate receives a large volume of groundwater from much of the bedrock invert, but the flow velocity is too slow to transport small particles out of the aggregate. Calcite saturation indices calculated from water-chemistry data suggest that the groundwater was capable of continuously dissolving calcite, the primary mineral in the limestone aggregate. Water samples taken during different flow conditions indicate that groundwater under low-flow conditions. The dissolution experiment showed that all the limestone aggregate placed beneath the roadbed and in contact with groundwater lost mass; the highest mass loss was 3.4 percent during a 178-day period. The experiment also suggested that water with higher calcite-dissolving potential removed limestone mass quicker than water with low calcite-dissolving potential. We recommend that the limestone aggregate be replaced with noncarbonate aggregate, such as granite, to prevent dissolution and future road subsidence

    Environmental geology study: parts of west Wiltshire and south-east Avon

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    The objective of this study has been to collect and interpret the available environmental geology data and to use it to compile a set of thematic maps and this report. The maps and report are intended for use by those not trained in geology as well as specialists, and to help assess the land-use planning implications of surface and subsurface development

    Ground penetrating radar technique to locate coal mining related features: case studies in Texas

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    The goal of this research project is to identify the efficacy of the ground penetrating radar (GPR) technique in locating underground coal mine related subsidence features at Malakoff and Bastrop, Texas. The work at Malakoff has been done in collaboration with the Railroad Commission of Texas (RRC). RRC has been carrying out reclamation of abandoned underground coal mines at Malakoff since the early 1990Ă‚s. The history of the specific mining operations (at Malakoff and Bastrop) that took place in the early 1900Ă‚s has been difficult to ascertain; therefore, the use of a geophysical techniques like ground penetrating radar to identify hidden voids and potential subsidence features is vital for future reclamation process. Some of the underground mine workings at the field site have collapsed over time affecting the topography by creating sinkholes. GPR data, employing 25 MHz, 50 MHz and 100 MHz frequency antennae, have been collected in common offset patterns and azimuthal pattern. GPR data indicate the mine tunnels possibly connecting existing sinkholes by radargram hyperbolae that correspond with mine openings observed visually or during reclamation. This study also denotes the importance of understanding the variable physical properties of the stratigraphy, which could lead to false alarms by misinterpretation of the radar signals. Natural and man-made above-ground structures cause obstructions in data collection, and hence an optimal design is required for each survey. RRC successfully ground-truthed the data during its reclamation process. In turn, the acquired geophysical data helped to guide the reclamation. At Bastrop, GPR data along with historical documentation led to the conclusion that coal mining did exist in this region but is not a major concern to the immediate stability and safety of the field site. It can be concluded from both the studies that the GPR technique identifies anomalous shafts/tunnels possibly connecting potential failure

    Patterns of stress and strain distribution during deep mining at Boulby, N. Yorkshire

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    The understanding of stress-deformation state transmission within the rock mass above deep mine workings is a key factor to the comprehension of the response of rock masses to changes of stress regime brought about by the mining activity for the safety of surface and subsurface structures. Based on monitoring data from active actual mine workings, this study numerically analyzes factors controlling stress and deformation using the 2D Fast Lagrangian Analysis of Continua (FLAC 2D) code and a strain-softening model to approximate creep behaviour of rock masses. The results show that distribution of stress and deformation at Boulby mine is primarily governed by the lithological heterogeneity of the overlying strata and the geological structure, including its nature within the undermined area. Data from a bespoke roof-to-floor monitoring closuremeter indicate that convergence of openings is a function of local variables, including the site location, geometry and age of the site. Patterns of ground subsidence are compared to the pattern of levelling-based measured ground subsidence. Furthermore, the analysis shows that the strain-softening model reasonably approximates the creep behaviour of the excavations. The results have implications for how we monitor and model subsidence due to mining deep excavations

    Proceedings of the 2009 Coal Operators\u27 Conference

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    Proceedings of the 2009 Coal Operators\u27 Conference. All papers in these proceedings are peer reviewed. ISBN: 978 1 920806 95 8

    Feasibility assessment and informed survey design of cavity detection by forward geophysical modelling

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    Feasibility analysis of near-surface cavity detection is presented using modelling of the gravity, gravity gradient, magnetic, magnetic gradient, and ground penetrating radar techniques. The geophysical signal is modelled over typical cavity shapes in three-dimensional subsurface environments with varying geologies and survey parameters. The cavity detection probability is calculated for each technique in the outlined environments and these values are used to aid technique choice, assess the feasibility of cavity detection, assess the limits of detection for each technique, and optimise survey design before entering the field. The “halo” effect is quantified by simulating the halo around cavities and calculating the change to the gravity and magnetic anomalies by geophysical modelling. The magnitude of the effect is shown to be more complicated than existing literature implies, depending heavily on the fracture percentage in the halo area and the halo spread. Tests in a range of conditions show that technique choice is conditional to site characteristics and site parameters, and highlight the need for modelling in the desk study stage of site investigation and survey design. Detection probability results show that standard survey direction practice in magnetometry is not always optimal, and demonstrate the importance of site specific noise level consideration. Comparisons with case study measurements demonstrate that modelling and subsequent detection probability calculation chose appropriate techniques and survey parameters, but also highlighted the limitations of the method
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