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51	STABILITY ANALYSIS OF A LONGWALL MINING IN NARVA OIL SHALE MINE Oisalu, Ott, Lõhmuste, Taavi January 2017 (has links) Oil shale industry in Estonia is looking at other mining technologies as alternative to strip mining and room and pillar mining methods. One such alternative to the room and pillar method is the punch-longwall mining method. Enefit Kaevandused AS, one of the major oil shale companies in Estonia, plans to employ this technology in exploiting some of its resources in the near future. This thesis examines the different stability problems related to the planned punch-longwall mining project in Narva oil shale mine. Determining optimal chain pillar dimensions and stability of the punch-longwall highwall slope are the main objectives of this project. Rock mechanical analyses have been done and recommendations are made based on the rock mechanical aspect of the mining process. Taavi Lõhmuste is responsible for the chain pillar stability analysis and Ott Oisalu for the punch-longwall highwall slope stability analysis. It is essential to understand the geology of a certain area in order to make accurate stability assessments. Because of the previously stated requirements, the geology of Estonian oil shale deposit is examined in the first part of the thesis in order to determine the geological and rock mechanical conditions to set the foundation for further analyses. In conclusion, for the part of the highwall slope, a properly designed barrier pillar plays a key role in the stability of the slope. After reviewing and analyzing the results of both highwall slope numerical models, it can be stated that the minimum length for the barrier pillar that still will yield in stable highwall slope is 65 meters. For the part of the chain pillars, in conclusion, it can be determined that optimal chain pillar dimensions that should be suitable, from the stability standpoint, are 6x6 meters for 3-entry system and 7x7 meters for 2-entry system (length x width). longwall mining oil shale stability analysis chain pillars barrier pillar slope stability Geotechnical Engineering Geoteknik
52	Optimizing secondary tailgate support selection Harwood, Cary P. 18 September 2008 (has links) A model was developed to facilitate secondary tailgate support selection based on analysis of a data base of over 100 case studies compiled from two different surveys of operating longwall coal mines in the United States. The ALPS (Analysis of Long wall Pillar Stability) program was used to determine adequacy of pillar design for the successful longwall case histories. A relationship was developed between the secondary support density necessary to maintain a stable tailgate entry during mining and the CMRR (Coal Mine Roof Rating). This relationship defines the lower bound of secondary support density currently used in longwall mines. The model used only successful tailgate case history data with adequate ALPS SF according to the CMRR for each case. This model facilitates mine design by predicting secondary support density required for a tailgate entry depending on the ALPS SF and CMRR, which can result in significant economic benefits. / Master of Science coal mining Longwall tailgate secondary support capacity LD5655.V855 1996.H379
53	Improvement of Ground-Fault Relaying Selectivity through the Application of Directional Relays to High-Voltage Longwall Mining Systems Basar, Joseph James 05 May 2004 (has links) The continuing trend toward larger longwall mining systems has resulted in the utilization of higher system voltages. The increase in system voltage levels has caused the industry to face complexities not experienced with the lower-voltage systems. One such complexity arises from the larger system capacitance that results from the outby configuration commonly used on 4,160-V longwall power systems. Simulations show that during a line-to-ground fault, the larger system capacitance can cause a situation where the ground current sensed by the ground-fault relays in unfaulted circuits is greater than the mandated ground-fault relay pick-up setting. Simulations show that ground-fault relaying selectivity is potentially lost as a result of this situation. Two alternatives were identified which could improve ground-fault relaying selectivity. They are: the application of a directional relaying scheme and increasing the ground-fault relay pick-up setting. It was determined that directional relays have an application to high-voltage longwall power systems as the ground current sensed by the relay in the unfaulted circuits is out of phase with the ground-fault current sensed by the relay in the faulted circuit. Furthermore, it was determined that raising the ground-fault relay pick-up setting by a factor of eight would also improve ground-fault relaying selectivity. A safety analysis considering the potential for electrocution and the power dissipated by the maximum fault resistance showed that increasing the pick-up setting by a factor of eight would have no detriment to safety. Therefore, either method would improve ground-fault relaying selectivity on high-voltage longwall mining systems, yet because of the escalating size of longwall systems, a directional relaying scheme is a longer term solution. / Master of Science coal mining 4160-V longwall underground mining mine power systems coal electrical safety
54	Longwall mining, subsidence, and protection of water resources in Virginia Roth, Richard A. January 1989 (has links) In the coalfields of Southwest Virginia, Iongwall technology accounts for an increasing proportion of underground coal mine production. lt is a highly productive, capital intensive method that provides a degree of mine safety greater than conventional methods. However, subsidence caused by Iongwall mining has been blamed for, among other things, damaging wells, springs, and streams above the mines. Surface landowners whose water supplies are affected by Iongwall mines may negotiate with mining companies for compensation, or they can seek redress in the courts. At the same time, the U.S. Surface Mine Control and Reclamation Act (SMCRA) provides a framework for regulation of the environmental effects of coal mining, including hydrologic effects. The Department of Mines, Minerals, and Energy, Division of Mined Land Reclamation (DMLR) is responsible for implementation of Virginia’s primacy program under SMCRA. This research has assessed the potential of Iongwall mining to damage the groundwater and surface water resources In Southwest Virginia; and examined whether existing laws and regulations, as implemented, provide an adequate and appropriate level of protection to both water property rights and the environment. Methods included review of published and ongoing literature on effects of underground coal mining on hydrologic systems and methods of mitigation; review of mining permits and complaint investigations on file at DMLR; review of court case decisions involving mining effects on groundwater and surface water; review of regulatory documents from other states active in Iongwall mining and the Federal Office of Surface Mining (OSM); and interviews with coal company personnel, DMLR and OSM officials, researchers, and regulatory officials in other states. Review of both DMLR complaint investigations and published reports of numerous hydrologic investigations indicate that longwall mining is likely to alter the hydrologic regime in the vicinity of the mine. The knowledge base for regulation of hydrologic impacts has been inadequate but is being improved in Virginia. Both DMLR and some coal companies recognize the need for more and better data, and are taking steps to develop the requisite data and models. Regulatory personnel in Ohio, Pennsylvania, West Virginia, and Kentucky have expressed recognition of similar data deficiencies in their states. At least one state, Ohio, has dealt with the problem of water rights by enacting legislation that assigns liability for replacing damaged water supplies to the mining companies. West Virginia, through its regulatory program, also requires water replacement. Recommendations are offered that have as their main objective the reduction of uncertainty about the effects of longwall mining and about compensation of surface owners for damage to water supplies. / Master of Urban and Regional Planning / incomplete_metadata LD5655.V855 1989.R676 Coal mines and mining -- Virginia Longwall mining -- Virginia Water rights -- Virginia Appalachian Region -- Economic aspects
55	Numerical modeling of stress redistribution to assess pillar rockburst proneness around longwall panels : Case study of the Provence coal mine, France / Modélisation numérique de la redistribution des contraintes pour évaluer la prédisposition aux coups de terrain autour des panneaux de longue taille : étude de cas de la mine de charbon de Provence, France Ahmed, Samar 13 December 2016 (has links) Le phénomène de coup de terrain est une explosion violente de roche qui peut se produire dans les mines souterraines. Dans la présente recherche, nous avons essayé de démontrer les causes qui peuvent influer sur la prédisposition aux coups de terrain en utilisant la modélisation numérique. Cependant, avant tout, l'état de contrainte avant l'exploitation minière et les contraintes induites par les excavations environnantes doivent être étudiés avec précision. La mine de charbon de Provence, qui a subi un phénomène de coup de terrain au niveau de son puits vertical entouré de nombreux panneaux de longue taille, a été choisie comme cas d’étude. Un modèle numérique 3D à grande échelle a été construit pour inclure la zone du puits vertical avec ses piliers et galeries à petite échelle et les panneaux de longue taille à grande échelle avec leurs zones de foudroyage associées. Plusieurs problèmes ont été rencontrés lors du développement de ce modèle numérique à grande échelle. Le premier porte sur l'initialisation de l'état de contrainte à grande échelle, où les contraintes verticales mesurées divergent avec le poids des déblais et les contraintes in situ sont très anisotropes. Le deuxième porte sur la simulation de la zone de foudroyage associée aux panneaux de longue taille. Le troisième concerne l'évaluation de l’instabilité du pilier en fonction de son ratio résistance/contrainte moyenne et de son volume. Le quatrième concerne l'évaluation de la prédisposition aux coups de terrain au niveau du puits vertical en fonction de différents critères. Cinq méthodes ont été développées pour initialiser l’état de contrainte hétérogène dans le modèle numérique à grande échelle avant l’exploitation minière. Elles sont basées sur la méthode de corrélation Simplex, qui consiste à optimiser la différence entre les valeurs de contrainte mesurées in-situ et les valeurs numériques. Le but est de développer des gradients qui soient capables d'exprimer l'hétérogénéité de la contrainte et qui soient compatibles avec les mesures in-situ. La méthode basée sur l’initialisation de l'état de contrainte avec des gradients 3D s’est avérée plus efficace que celle traditionnelle basée sur les ratios de contrainte horizontale à verticale. Concernant la simulation du foudroyage, trois modèles ont été développés et intégrés dans le modèle numérique pour exprimer le comportement mécanique dans la zone de foudroyage au-dessus des panneaux de longue taille. Deux d’entre eux sont basés sur un comportement élastique alors que le troisième est basé sur un comportement elasto-plastique avec écrouissage un phénomène de consolidation. Il a été constaté que la zone de foudroyage au-dessus des panneaux de longue taille peut atteindre 32 fois l'épaisseur de la couche exploitée et que le module d'élasticité de la partie la plus endommagée de la zone foudroyée ne doit pas excéder 220 MPa pour satisfaire la convergence toit-mur. Mais, avec l'avancée de l'exploitation, ce matériau souple se compacte sous la pression des couches supérieures. Dans le cas d'une largeur critique et super-critique, la contrainte verticale dans la zone de foudroyage pourrait dépasser le poids des déblais et pourrait augmenter jusqu'à 4 fois ce poids sur les bords. La contrainte verticale a augmenté dans les piliers au niveau du puit vertical suite à l'exploitation des panneaux de longue taille à proximité. Il a été constaté que le volume du pilier joue un rôle important dans sa stabilité. Le rapport contrainte/résistance a été jugé insuffisant pour expliquer un coup de terrain. Plusieurs critères ont été intégrés au modèle numérique pour évaluer la prédisposition aux coups de terrain. Il a été constaté que les critères basés sur les contraintes et les déformations sont capables d'évaluer la prédisposition aux coups de terrain / Rockburst is a violent explosion of rock that can occur in underground mines. In the current research, the main objective is to demonstrate the causes that may influence the rockburst proneness by using the numerical modeling tool. However, firstly, the pre-mining stress state and the induced stresses due to surrounding excavations have to be studied precisely. The Provence coal mine, where a rockburst took place in its shaft station that is surrounded by many longwall caving panels, has been chosen as a case study. A large-scale 3D numerical model has been constructed to include the shaft station area with its small-scale pillars and galleries, and the large-scale longwall panels with their accompanying goaf area. Many problems appeared while developing such large-scale numerical model, the first problem was the initialization of stress state at a large-scale, where the measured vertical stresses are in disagreement with the overburden weight, and the in-situ stresses are highly anisotropic. The second problem was the simulation of the goaf area accompanying longwall panels. The third problem was the assessment of pillars instability in terms of its strength/average stress ratio, and its volume. The Fourth problem was the assessment of rockburst proneness in the shaft station based on different rockburst criteria. Five methods were developed to initialize the heterogeneous pre-mining stress in the large-scale numerical model. These methods are based on the Simplex Method, which is mainly based on optimizing the difference between the in-situ measured stress values and the numerical stress values to develop stress gradients able to express the stress heterogeneity and compatible with the in-situ measurements. The method that is based on initiating the stress state with 3D stress gradients was found to be more efficient than the traditional method that is based on the horizontal-to-vertical stress ratios. Regarding the goaf simulation, three models were developed and implemented in the numerical model to express the mechanical behavior within the goaf area above longwall panels. Two of these models are based on an elastic behavior, and the third one is based on the strain-hardening elasto-plastic behavior that takes the consolidation phenomenon into consideration. It was found that the goaf area above longwall panels could reach up to 32 times the seam thickness, and the elastic modulus of caved area (the first few meters in the goaf area) did not exceed 220 MPa to fulfill the roof-floor convergence. But, with advance of the exploitation, this soft material consolidated under the pressure of the overlying strata. In case of critical and super-critical width, the vertical stress in the goaf area exceeded the overburden weight, and it increased up to 4 times the overburden weight on the rib-sides. The vertical stress increased in the shaft station pillars as a result of exploiting the nearby longwall panels. It was found that the pillar volume plays an important role in its stability. And, the strength/stress ratio was found to be insufficient to quantify the rockburst proneness in underground mines. Many rockburst criteria were implemented in the numerical model to assess the rockburst proneness. It was found that the criteria that are based on stress and strain changes were able to assess the rockburst proneness Modélisation numérique Excavation par longue taille Foudroyage Prédisposition aux Coups de terrain Numerical modeling Longwall excavation Goaf Rockburst prediction 624.151 32 622.809 44
56	Visualizing and Modeling Mining-Induced Surface Subsidence Platt, Marcor Gibbons 13 July 2009 (has links) (PDF) Ground subsidence due to underground coal mining is a complex, narrowly-understood phenomenon. Due to the complicated physical processes involved and the lack of a complete knowledge of the characteristics of overlying strata, the reliability of current prediction techniques varies widely. Furthermore, the accuracy of any given prediction technique is largely dependent upon the accuracy of field measurements and surveys which provide input data for the technique. A valuable resource available for predicting and modeling subsidence is aerial survey technology. This technology produces yearly datasets with a high density of survey points. The following study introduces a method wherein these survey points are converted into elevation plots and subsidence plots using GIS. This study also presents a method, titled the Type-Xi Integration method (TXI method), which improves upon a previous subsidence prediction technique. This method differs from the previous technique in that it incorporates accurate surface topography and considers irregular mine geometry, as well as seam thickness and overburden variations in its predictions. The TXI method also involves comparing predicted subsidence directly to measured subsidence from subsidence plots. In summary, this study illustrates a method of combining data from aerial survey points and mine geometry with subsidence models in order to improve the accuracy of the models. longwall coal mine mining subsidence GIS Deer Creek Mine Crandall Canyon Mine Aberdeen Mine TXI influence function aerial survey natural neighbor voronoi GCS 1927 SPCS Civil and Environmental Engineering
57	Prognose und bergschadenkundliche Analyse dynamischer Bodenbewegungen durch oberflächennahen Steinkohlenbergbau in den USA Zimmermann, Karsten 28 March 2011 (has links) (PDF) Der untertägige Abbau von Steinkohle führt zu Bewegungen des überlagernden Gebirges und der Tagesoberfläche. Eine Bewegungsprognose ist im Hinblick auf entstehende Bergschäden weltweit von großer Bedeutung. In dieser Arbeit wird untersucht, ob eine Prognose von Bodenbewegungen im amerikanischen Steinkohlenbergbau mit einem in Europa bewährten Verfahren, einem dynamischen stochastischen Senkungsmodell, möglich ist. Dazu wurde eine Literaturstudie über den bisherigen Kenntnisstand in den USA durchgeführt, abbaubegleitende Bodenbewegungsmessungen aus dem Steinkohlengebiet der Appalachen ausgewertet und durch Modellrechnungen nachgebildet. Es wurde darüber hinaus untersucht, welchen Einfluss die spezifischen Abbaubedingungen und die räumliche und zeitliche Abbauführung auf die Größe und Dynamik von Bodenbewegungen haben. Die theoretischen und praktischen Untersuchungen zeigen einen deutlichen Know-how Vorsprung des europäischen Bergbaus in den Bereichen der Senkungsmodellierung und Bewertung abbauinduzierter Bodenbewegungen und belegen die Anwendbarkeit des Senkungsmodells. Es wurden wichtige Erkenntnisse gewonnen, die Möglichkeiten und Grenzen einer Optimierung des Abbauzuschnitts und der zeitlichen Abbauführung im Sinne einer bergschadensmindernden Abbauplanung aufzeigen. Die Arbeit trägt zur Verbesserung der bergmännischen und markscheiderischen Abbauplanung im Steinkohlenbergbau bei. Bergbau Bergwerk Steinkohlenbergbau Steinkohlenabbau Steinkohlenbergwerk Steinkohle Abbau Streb Strebabbau Bodenbewegung Gebirgsbewegung Deformation Senkung Schieflage Zerrung Pressung Krümmung Bergsenkung Senkungsmodell Senkungsmodellierung Prognose Modellierung Abbauplanung Planung Abbaugeschwindigkeit Bewegungsdynamik Abbaustopp Dynamik Bergschaden Bergschadenkunde Bergschadensminderung Bergschadensmindernde Appalachen USA Pennsylvania Pittsburgh Morgantown Knothe Markscheider Markscheidewesen mining mine coal hard anthracite stone longwall face surface ground movement seam deformation subsidence strata overburden rock mass subsidence slope tilt model modeling prediction planning retreat winning rate speed stop break dynamics impact damage mitigation assessment protection control engineering Appalachia Appalachian basin USA Pennsylvania Pittsburgh Morgantown Knothe Knothe’s method surveyor miner surveying ddc:620 Appalachen USA / Nordoststaaten Steinkohlenbergwerk Steinkohlenbergbau Bergschaden Bergsenkung
58	Prognose und bergschadenkundliche Analyse dynamischer Bodenbewegungen durch oberflächennahen Steinkohlenbergbau in den USA Zimmermann, Karsten 28 March 2011 (has links) Der untertägige Abbau von Steinkohle führt zu Bewegungen des überlagernden Gebirges und der Tagesoberfläche. Eine Bewegungsprognose ist im Hinblick auf entstehende Bergschäden weltweit von großer Bedeutung. In dieser Arbeit wird untersucht, ob eine Prognose von Bodenbewegungen im amerikanischen Steinkohlenbergbau mit einem in Europa bewährten Verfahren, einem dynamischen stochastischen Senkungsmodell, möglich ist. Dazu wurde eine Literaturstudie über den bisherigen Kenntnisstand in den USA durchgeführt, abbaubegleitende Bodenbewegungsmessungen aus dem Steinkohlengebiet der Appalachen ausgewertet und durch Modellrechnungen nachgebildet. Es wurde darüber hinaus untersucht, welchen Einfluss die spezifischen Abbaubedingungen und die räumliche und zeitliche Abbauführung auf die Größe und Dynamik von Bodenbewegungen haben. Die theoretischen und praktischen Untersuchungen zeigen einen deutlichen Know-how Vorsprung des europäischen Bergbaus in den Bereichen der Senkungsmodellierung und Bewertung abbauinduzierter Bodenbewegungen und belegen die Anwendbarkeit des Senkungsmodells. Es wurden wichtige Erkenntnisse gewonnen, die Möglichkeiten und Grenzen einer Optimierung des Abbauzuschnitts und der zeitlichen Abbauführung im Sinne einer bergschadensmindernden Abbauplanung aufzeigen. Die Arbeit trägt zur Verbesserung der bergmännischen und markscheiderischen Abbauplanung im Steinkohlenbergbau bei. info:eu-repo/classification/ddc/620 ddc:620 Appalachen USA / Nordoststaaten Steinkohlenbergwerk Steinkohlenbergbau Bergschaden Bergsenkung

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