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Artigos de revistas sobre o assunto "Hard rock pillar"
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Jessu, Kashi, Anthony Spearing e Mostafa Sharifzadeh. "A Parametric Study of Blast Damage on Hard Rock Pillar Strength". Energies 11, n.º 7 (20 de julho de 2018): 1901. http://dx.doi.org/10.3390/en11071901.
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Pillar stability is an important factor for safe working and from an economic standpoint in underground mines. This paper discusses the effect of blast damage on the strength of hard rock pillars using numerical models through a parametric study. The results indicate that blast damage has a significant impact on the strength of pillars with larger width-to-height (W/H) ratios. The blast damage causes softening of the rock at the pillar boundaries leading to the yielding of the pillars in brittle fashion beyond the blast damage zones. The models show that the decrease in pillar strength as a consequence of blasting is inversely correlated with increasing pillar height at a constant W/H ratio. Inclined pillars are less susceptible to blast damage, and the damage on the inclined sides has a greater impact on pillar strength than on the normal sides. A methodology to analyze the blast damage on hard rock pillars using FLAC3D is presented herein.
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Kamran, Muhammad, Waseem Chaudhry, Blessing Olamide Taiwo, Shahab Hosseini e Hafeezur Rehman. "Decision Intelligence-Based Predictive Modelling of Hard Rock Pillar Stability Using K-Nearest Neighbour Coupled with Grey Wolf Optimization Algorithm". Processes 12, n.º 4 (13 de abril de 2024): 783. http://dx.doi.org/10.3390/pr12040783.
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Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, productive, reliable, and profitable underground mining engineering processes. This study developed the application of decision intelligence-based predictive modelling of hard rock pillar stability in underground engineering structures using K-Nearest Neighbour coupled with the grey wolf optimization algorithm (KNN-GWO). Initially, a substantial dataset consisting of 236 different pillar cases was collected from seven underground hard rock mining engineering projects. This dataset was gathered by considering five significant input variables, namely pillar width, pillar height, pillar width/height ratio, uniaxial compressive strength, and average pillar stress. Secondly, the original hard rock pillar stability level has been classified into three types: failed, unstable, and stable, based on the pillar’s instability mechanism and failure process. Thirdly, several visual relationships were established in order to ascertain the correlation between input variables and the corresponding pillar stability level. Fourthly, the entire pillar database was randomly divided into a training dataset and testing dataset with a 70:30 sampling method. Moreover, the (KNN-GWO) model was developed to predict the stability of pillars in hard rock mining. Lastly, the performance of the suggested predictive model was evaluated using accuracy, precision, recall, F1-score, and a confusion matrix. The findings of the proposed model offer a superior benchmark for accurately predicting the stability of hard rock pillars. Therefore, it is recommended to employ decision intelligence models in mining engineering in order to effectively prioritise safety measures and improve the efficiency of operational processes, risk management, and decision-making related to underground engineering structures.
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Xie, Xuebin, e Huaxi Zhang. "Research on Hard Rock Pillar Stability Prediction Based on SABO-LSSVM Model". Applied Sciences 14, n.º 17 (2 de setembro de 2024): 7733. http://dx.doi.org/10.3390/app14177733.
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The increase in mining depth necessitates higher strength requirements for hard rock pillars, making mine pillar stability analysis crucial for pillar design and underground safety operations. To enhance the accuracy of predicting the stability state of mine pillars, a prediction model based on the subtraction-average-based optimizer (SABO) for hyperparameter optimization of the least-squares support vector machine (LSSVM) is proposed. First, by analyzing the redundancy of features in the mine pillar dataset and conducting feature selection, five parameter combinations were constructed to examine their effects on the performance of different models. Second, the SABO-LSSVM prediction model was compared vertically with classic models and horizontally with other optimized models to ensure comprehensive and objective evaluation. Finally, two data sampling methods and a combined sampling method were used to correct the bias of the optimized model for different categories of mine pillars. The results demonstrated that the SABO-LSSVM model exhibited good accuracy and comprehensive performance, thereby providing valuable insights for mine pillar stability prediction.
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Korzeniowski, W. "Rheological model of hard rock pillar". Rock Mechanics and Rock Engineering 24, n.º 3 (1991): 155–66. http://dx.doi.org/10.1007/bf01042859.
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Xu, Huawei, Derek B. Apel, Jun Wang, Chong Wei e Krzysztof Skrzypkowski. "Investigation and Stability Assessment of Three Sill Pillar Recovery Schemes in a Hard Rock Mine". Energies 15, n.º 10 (21 de maio de 2022): 3797. http://dx.doi.org/10.3390/en15103797.
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In Canada, many mines have adopted the sublevel stoping method, such a blasthole stoping (BHS), to extract steeply deposited minerals. Sill pillars are usually kept in place in this mining method to support the weight of the overburden in underground mining. To prolong the mine’s life, sill pillars will be recovered, and sill pillar recovery could cause failures, fatality, and equipment loss in the stopes. In this paper, three sill pillar recovery schemes—SBS, SS1, and SS2—were proposed and conducted to assess the feasibility of recovering two sill pillars in a hard rock mine by developing a full-sized three-dimensional (3D) analysis model employing the finite element method (FEM). The numerical model was calibrated by comparing the model computed ground settlement with the in situ monitored ground settlement data. The rockburst tendency of the stope accesses caused by the sill pillar recovery was assessed by employing the tangential stress (Ts) criterion and burst potential index (BPI) criterion. All three proposed sill pillar recovery schemes were feasible and safe to recover the sill pillars in this hard rock mine, and the scheme SBS was the optimum one among the three schemes.
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Ma, Hai Tao, e Jin An Wang. "Dynamic Simulation Method for Hard-Rock Pillar Failure in Open-Stope Goaf". Applied Mechanics and Materials 556-562 (maio de 2014): 4055–60. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.4055.
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An attempt to simulate the cascading pillar collapse is made in this paper for a quick evaluation of a large number of mined-out area data that have been collected throughout China. Pillar collapse, load transfer and load redistribution are modeled by the area-apportioned method, and this methodology is general in sense and has been implemented in the expert system developed by the authors as an independent module. The proposed method can provide a quantitative criterion for determination of the failure pattern and identification of the key pillars in the stability analysis of the mined-out area formed by a pillar-room method.
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Ile, D., e D. F. Malan. "A study of backfill confinement to reinforce pillars in bord-and-pillar layouts". Journal of the Southern African Institute of Mining and Metallurgy 123, n.º 5 (13 de julho de 2023): 223–33. http://dx.doi.org/10.17159/2411-9717/2452/2023.
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This study explores the use of backfill in hard rock bord-and-pillar mines to increase the pillar strength and extraction ratio at depth. The use of backfill will also minimize the requirement for tailings storage on surface and the risk of environmental damage. A literature survey indicated that backfill is extensively used in coal mines, but rarely in hard rock bord-and-pillar mines. To simulate the effect of backfill confinement on pillar strength, an extension of the limit equilibrium model is proposed. Numerical modelling of an actual platinum mine layout is used to illustrate the beneficial effect of backfill on pillar stability at greater depths. The magnitude of confinement exerted by the backfill on the pillar sidewalls is unknown, however, and this needs to be quantified using experimental backfill mining sections equipped with suitable instrumentation.
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Napier, J. A. L., e D. F. Malan. "Numerical simulation of large-scale pillar-layouts". Journal of the Southern African Institute of Mining and Metallurgy 123, n.º 5 (13 de julho de 2023): 203–10. http://dx.doi.org/10.17159/2411-9717/2451/2023.
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A number of shallow coal or hard rock mines employ pillar mining systems as a strategy for roof failure control. In certain platinum mine layouts, pillars are designed to 'crush' in a stable manner as they become loaded in the panel back area. The correct sizing of pillars demands some knowledge of the pillar strength and the overall layout stress distribution. It is particularly important to understand the impact of the layout geometry on the effective regional 'stiffness' of the rock mass around each pillar. An important design strategy is to model relatively detailed layout configurations which include a precise representation of the local pillar layout geometry and to analyse multiple mining scenarios and extraction sequences to select optimal pillar sizes and barrier pillar spacing. Although computational solution techniques are now impressive in terms of run time efficiency, a major difficulty is often encountered in assigning suitable material properties to the pillars and in devising an effective material description of the layered rock strata overlying the mine excavations. This paper outlines an efficient numerical strategy that can be used to assess large-scale pillar layout performance while retaining the ability to modify individual pillar constitutive behaviour. The proposed method is applied to selected layouts to compare estimated average pillar stress values against values determined by detailed modelling and against observed behaviour.
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Liu, Jiangwei, Changyou Liu e Xuehua Li. "Determination of fracture location of double-sided directional fracturing pressure relief for hard roof of large upper goaf-side coal pillars". Energy Exploration & Exploitation 38, n.º 1 (4 de novembro de 2019): 111–36. http://dx.doi.org/10.1177/0144598719884701.
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After mining the upper-goaf side, large coal pillars and part of hard roof exposed above the pillars remain. The hard roof can significantly deform the roadway by transferring high stress through coal pillars to the roadway. This paper reports the use of hydraulic fracturing technology to cut the hard roof on both sides (i.e. the broken roof slides to the goaf) to relieve the pressure. The position of the roof fracture is the key to controlling the pressure relief. The bearing characteristics of the large coal pillars and hard roof are analyzed to establish a mechanical model of the broken-roof sliding instability after directional fracturing and determine the width of the coal pillars that can collapse under maximum overburden load on coal pillars as a reasonable hydraulic fracturing position. The results show that the distance from the mine gateway to the fracture location increases with increasing hard-roof length, coal pillar depth, coal pillar thickness (mining height), and goaf width. In addition, the distance to the mine gateway decreases with increasing coal strength, support of the coal pillar by the anchor rod, cohesive force, and internal friction angle of the coal–rock interface. Engineering tests were applied in coal roadway 5107 of coal seam 5# of the Baidong Coal Mine of the Datong Coal Mine Group. Given the site conditions, a reasonable fracturing length of 8.8 m was obtained. Next, directional hydraulic fracturing was implemented. The comparison of the roof deformation before and after fracturing suggests that this method reduces the local stress concentration in coal pillars, which allows the surrounding rock deformation in roadway 5107 to be controlled.
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Liang, Weizhang, Suizhi Luo, Guoyan Zhao e Hao Wu. "Predicting Hard Rock Pillar Stability Using GBDT, XGBoost, and LightGBM Algorithms". Mathematics 8, n.º 5 (11 de maio de 2020): 765. http://dx.doi.org/10.3390/math8050765.
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Predicting pillar stability is a vital task in hard rock mines as pillar instability can cause large-scale collapse hazards. However, it is challenging because the pillar stability is affected by many factors. With the accumulation of pillar stability cases, machine learning (ML) has shown great potential to predict pillar stability. This study aims to predict hard rock pillar stability using gradient boosting decision tree (GBDT), extreme gradient boosting (XGBoost), and light gradient boosting machine (LightGBM) algorithms. First, 236 cases with five indicators were collected from seven hard rock mines. Afterwards, the hyperparameters of each model were tuned using a five-fold cross validation (CV) approach. Based on the optimal hyperparameters configuration, prediction models were constructed using training set (70% of the data). Finally, the test set (30% of the data) was adopted to evaluate the performance of each model. The precision, recall, and F1 indexes were utilized to analyze prediction results of each level, and the accuracy and their macro average values were used to assess the overall prediction performance. Based on the sensitivity analysis of indicators, the relative importance of each indicator was obtained. In addition, the safety factor approach and other ML algorithms were adopted as comparisons. The results showed that GBDT, XGBoost, and LightGBM algorithms achieved a better comprehensive performance, and their prediction accuracies were 0.8310, 0.8310, and 0.8169, respectively. The average pillar stress and ratio of pillar width to pillar height had the most important influences on prediction results. The proposed methodology can provide a reliable reference for pillar design and stability risk management.
Teses / dissertações sobre o assunto "Hard rock pillar"
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Li, Chuanqi. "Caractérisation automatique et semi-automatique des discontinuités des piliers de roche dure". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI045.
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Le pilier de roche dure est une structure rocheuse unique qui joue un rôle toujours cEAssant dans le maintien de la stabilité de l'espace souterrain dans les mines de métaux. Cependant, des effondrements, des éclatements de roches, des éboulements locaux sur de vastes zones et d'autres catastrophes techniques défavorables sont fréquemment observés sur le pilier avec des informations de discontinuité inconnues. Les recherches sur la caractérisation des discontinuités pour améliorer la sécurité minière méritent donc d’être menées. D'autre part, avec la vulgarisation et l'application de l'intelligence artificielle dans le secteur minier, il est nécessaire de réaliser la caractérisation automatique des informations discontinues des piliers.Cette thèse vise à caractériser les discontinuités des piliers en roche dure par des méthodes automatiques ou semi-automatiques. Les codes des principaux algorithmes sont écrits respectivement dans les langages MATLAB, Python et C++. Tout d’abord, une technique de mesure sans contact appelée SfM basée sur la photogrammétrie est utilisée pour obtenir des informations sur les discontinuités représentées par des images. Ensuite, un modèle de pilier 3D est reconstruit pour exporter les données de nuages de points afin de détecter les ensembles de discontinuités et les plans correspondants et de calculer l'orientation des discontinuités à l'aide d'une méthode automatique. Ensuite, les données d'image sont adoptées pour établir des modèles d'apprentissage profond permettant d'extraire des traces de fracture. La squelettisation, la description quantitative et l'approximation sont utilisées pour quantifier la longueur de la trace, l'angle d'inclinaison, la densité et l'intensité. Enfin, l'espacement des traces de fracture est caractérisé à l'aide d'une méthode semi-automatique. Les traces de fracture extraites sont déconnectées à l'aide d'un algorithme de seuil d'angle et classées à l'aide d'un nouvel algorithme de regroupement. Trois indices d'espacement peuvent être calculés à l'aide de lignes de balayage définies par les utilisateurs. Le travail présenté étudie d’abord les paramètres discontinus des piliers en roche dure, fournissant ainsi des données réelles pour la conception des supports des piliers, l’évaluation de la stabilité et l’analyse de simulation de ruptureThe hard rock pillar is a unique rock structure that plays an ever-increasing role in maintaining underground space stability in metal mines. However, collapse, rock burst, local large area caving, and other adverse engineering disasters are frequently observed on the pillar with unknown discontinuity information. Therefore, the research on the characterization of discontinuities to improve mining safety is worth carrying out. On the other hand, with the popularization and application of artificial intelligence in mining, it is necessary to realize the automatic characterization of pillar discontinuous information.This dissertation aims to characterize the discontinuities of hard rock pillars using automatic or semi-automatic methods. The codes of the main algorithms are written in MATLAB, Python, and C++ languages, respectively. First, a non-contact measurement technique named the photogrammetry-based SfM is utilized to obtain discontinuity information represented by images. Then, a 3D pillar model is reconstructed to export point cloud data for detecting discontinuity sets and the corresponding planes and calculating discontinuity orientation using an automatic method. Next, the image data is adopted to establish deep learning models for extracting fracture traces. The skeletonization, quantitative description, and approximation are used to quantify trace length, dip angle, density, and intensity. Finally, the fracture trace spacing is characterized using a semi-automatic method. The extracted fracture traces are disconnected using an angle threshold algorithm and classified using a novel grouping algorithm. Three spacing indices can be calculated using scanlines set by users. The presented work first investigates discontinuous parameters of hard rock pillars, thus it provides real data for pillars’ support design, stability evaluation, and failure simulation analysis
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Maybee, William Gregory. "Pillar design in hard brittle rocks". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0011/MQ61284.pdf.
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Jessu, Kashi Vishwanath. "Investigating the Performance of Hard Rock Pillars with Different Width to Height Ratios and the Effects of Inclination, a Discontinuity and Blasting". Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75347.
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Pillar design, a challenge in underground hard rock mines, contributes to catastrophic failure or economic loss based on its failure mechanism. Factors influencing the pillar failure mechanisms such as pillar inclination, presence of discontinuity and blasting effects were investigated with the help of laboratory tests and numerical analyses to create a design structure. Lastly, the pillar designs were evaluated by developing strain based monitoring method for pillar classification and pillar optimization.
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Lunder, Per John. "Hard rock pillar strength estimation an applied empirical approach". Thesis, 1994. http://hdl.handle.net/2429/5391.
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Pillars are present in all hard rock mining operations and in order to effectively design these pillars, an
estimate of the pillar strength is required. Two new pillar strength estimation methods for hard rock mine
pillars are presented in this thesis. 31 pillar case histories of the database that was used to develop these new
formulae were acquired during a cooperative study, entitled “Ground Stability Guidelines for the Extraction of
Barrier Pillars in Hard Rock Mines”, between Westmin Resources Ltd. and The Canadian Centre for Mineral
and Energy Technology (CANMET). 147 additional case histories were acquired from six documented hard
rock pillar case studies in the literature, resulting in a combined database of 178 case histories.
The combined database is comprised mainly of massive sulphide pillars with rock mass ratings of
between 60% and 85%. Major structural features were not deemed to be an influence in pillar instability.
Pillar stressess were calculated using either tributary area theory or numerical modelling methods. The factors
determined to influence pillar strength for the combined database therefore are:
• the average pillar confinement (which is a function of pillar geometry)
• the unconfined compressive strength of the intact pillar material
• the stresses that a pillar is subjected to
The degree to which a pillar has failed is quantifiable using a pillar stability classification index which
ranges from “1” (stable) to “5” (failed). The estimation of pillar stresses is preferably determined using threedimensional
numerical modelling, but in some situations two-dimensional numerical modelling or tributary
area theory may provide adequate results. It was concluded that the full size unconfined compressive strength
of a pillar can be approximated by a strength size factor of 44 percent of the small scale unconfined
compressive strength of intact pillar material.
Two pillar strength formulae have been developed from the combined pillar database: “The Log-Power
Shape Effect Formula” and “The Confinement Formula”. Both of the methods utilize the average pillar
confinement. “The Log-Power Shape Effect Formula” is a refined shape effect formula which has a form
similar to that proposed by researchers in the past. “The Confinement Formula” has a form that resembles the
Mohr-Coulomb shear strength formula.
The combined database was analyzed and the predicted strengths from “The Confinement Formula”
was compared to the results for existing pillar strength methods (Hedley & Grant (1972), Bieniawski (1975),
Salamon & Munro (1967), Obert & Duvall (1967), Hoek & Brown (1980)). “The Confinement Formula” is
shown statistically to be the most reliable method of estimating the strength of the pillars that make up the
combined database.
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Mandingaisa, Omberai. "Quantification of the impacts of rock mass quality on stope width control and pillar stability in a hard rock narrow reef mine". Thesis, 2018. https://hdl.handle.net/10539/26770.
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A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2018In bord and pillar mining, pillar stability is a key element of the mining process. This is usually underpinned by successful adherence to planned mining stope width. Stope width control is the backbone to the grade control process in platinum mines on the great Dyke of Zimbabwe. Poor rock mass has always been used to explain the failures by mining personnel to meet the requisite stoping width. A quantification process for this risk in monetary terms is tested and proves that geotechnical risk at times does less damage to the business value stream than malpractices. A review process followed in this research shows the vital path to value preservation and reduction of unnecessary dilution of the ore. A robust pillar support system is critical in a bord and pillar setup in shallow mines. These pillars are designed not to yield nor crush. Despite meeting design criteria, however, pillars are still found to fail. A tool to quantify this risk in monetary terms is an unparalleled advantage. A classical case is presented in this research illustrating the critical steps that can be followed to scientifically provide management with the financial information on which to base decisions. Poor rock mass conditions will always require to be adequately supported for sustainability of the mining business. This normally requires the installation of longer tendons, a time-consuming process. A slightly more expensive support product (the Flexibolt) was tested in this research to optimise the support process resulting in great value addition to the business. A case study is presented in this research report. Proposals for inclusion of a geotechnical risk quantification process to assist management to make value-based mining layout and operational decisions are also presented in this report.
XL2019
Livros sobre o assunto "Hard rock pillar"
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Maybee, William Gregory. Pillar design in hard brittle rocks. Sudbury, Ont: Mineral Resources Engineering, Laurentian University, 2000.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Hard rock pillar"
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Spasojević, S., e K. Skrobic. "Examination of rock reinforcement and stability of the hard rock pillars due to the over-break and blast damage". In Expanding Underground - Knowledge and Passion to Make a Positive Impact on the World, 958–66. London: CRC Press, 2023. http://dx.doi.org/10.1201/9781003348030-115.
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Hamediazad, Farzaneh, e Navid Bahrani. "Stability Analysis of Hard Rock Pillars Under Compressive and Shear Loading Conditions Using 2D and 3D Numerical Modeling". In Atlantis Highlights in Engineering, 859–69. Dordrecht: Atlantis Press International BV, 2023. http://dx.doi.org/10.2991/978-94-6463-258-3_80.
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Jeremic, M. L. "Mine pillar structures". In Ground Mechanics in Hard Rock Mining, 211–56. CRC Press, 2020. http://dx.doi.org/10.1201/9781003079217-8.
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Andersson, Christer, Mikael Rinne, Isabella Staub e Toivo Wanne. "The On-Going Pillar Stability Experiment at the Äspö Hard Rock Laboratory, Sweden". In Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems - Fundamentals, Modelling, Experiments and Applications, 389–94. Elsevier, 2004. http://dx.doi.org/10.1016/s1571-9960(04)80072-7.
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Ching, Barbara. "Dying hard: Hard country at the finish line?" In Wrong’s What I do Best, 119–34. Oxford University PressNew York, NY, 2001. http://dx.doi.org/10.1093/oso/9780195108354.003.0006.
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Abstract In the ’70s, as Owens’s career was fading, the much-heralded Outlaw movement, led by Waylon Jennings and Willie Nelson (but including a range of others),1 managed to buck the system in ways very similar to Owens’s. Like Owens, the Outlaws armed themselves with Telecasters and a rock beat, and then insisted on the right to produce their own music. Like Owens, they preferred show venues like Manhattan’s hip Max’s Kansas City or massive festivals and arenas to the staid and low-paying Opry. “Who listens to the Opry nowadays? Ain’t nobody out there listening anymore,” Jennings told Peter Guralnick in 1974 (208). According to Frye Gaillard, Roy Acuff denounced Nelson’s rejection of the fold from the Opry stage (146). However, this rebellion would have been far less newsworthy if the rebels had acknowledged their similarity to Owens. Instead, one of Jennings’s first appearances in the outlaw mode introduces him as a pill-popping “psychedelic cowboy” and critic of Owens: “he does some of the most ridiculous damn things I ever heard,” Jennings complained (Grissim, 80).2
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Djerassi, Carl. "A softer chemist". In This Man’s Pill, 188–213. Oxford University PressOxford, 2001. http://dx.doi.org/10.1093/oso/9780198508724.003.0009.
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Abstract Until 1969, I would have described myself as a ‘hard’ scientist, the proudly macho adjective employed by chemists and other physical scientists to distinguish their work from the ‘soft,’ fuzzy fields such as sociology or even psychology. Next to physics, chemistry is the hardest of the hard sciences, the rock on which the biomedical, environmental, and material sciences all build their molecular edifices. Chemistry—the molecular science par excellence—also tends to pride itself on the social corollary of its flinty strength: it is the most insular of the hard sciences. In academia, we chemists are often the most conservative, refusing to climb beyond our self-imposed disciplinary walls.
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Reddy, M. N., R. Venugopala Rao, S. Naik e R. N. Gupta. "Novel approach to optimise the dimensions of pillars in underground hard rock mine". In Geoecology and Computers, 451–59. Routledge, 2018. http://dx.doi.org/10.1201/9780203753620-77.
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Pytel, Witold, Bogumila Palac-Walko e Piotr Mertuszka. "Geomechanical safety aspects in hard rocks mining based on room-and-pillar and longwall mining systems". In Minefill 2020-2021, 288–304. CRC Press, 2021. http://dx.doi.org/10.1201/9781003205906-26.
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Clarke, Katherine. "Geographical and Historiographical Traditions". In Between Geography and History, 1–76. Oxford University PressOxford, 2000. http://dx.doi.org/10.1093/oso/9780199240036.003.0001.
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Abstract ‘Where are you going from here?’ Gilles asked. ‘South, to Sartene and Bonifacio.’ ‘Bonifacio is a very pretty place. You know Homer’s Odyssey? Bonifacio is where the Laestrygonians live.’That was beautiful, that he referred to the distant little port, not for a good restaurant or a luxury hotel or its fortress or a trivial event, but as the place where a group of savage giants had interfered with Ulysses. When it comes to literary allusions you can’t do much better than use the authority of the Odyssey to prove that your home town was once important. In Gibraltar Sir Joshua Hassan had jerked his thumb sideways towards the Rock and said to me ‘That’s one of the Pillars of Hercules’ .
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Gratzer, Walter. "Dr Pincus’s pill". In Eurekas and euphorias, 252–53. Oxford University PressNew York, NY, 2002. http://dx.doi.org/10.1093/oso/9780192804037.003.0154.
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Abstract The birth-control pill is associated with the names of Gregory Pincus, John Rock, and Carl Djerassi—the physiologist, the doctor, and the organic chemist— and quite a number of others, for many man-years of patient research went into its development. Much of the initial impetus came from Margaret Sanger, who had sought to liberate women from the tyranny of unwanted pregnancies, and the philanthropist Katherine McCormick. The first success came in 1955, when Rock, a professor at Harvard Medical Scool and an expert on fertility, began cautiously testing the effect of the hormone analogue, progestin, on a plucky ‘cagefull’ of ovulating women, willing guinea-pigs all.
Trabalhos de conferências sobre o assunto "Hard rock pillar"
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Dzimunya, N. Z., e Y. Fujii. "A Proposed Framework to Estimate Pillar Strength in Room-And-Pillar Hard Rock Mines". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0116.
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ABSTRACT: Pillar strength determination is a fundamental aspect of room-and-pillar mine design. Pillars are left between excavated rooms to maintain stability by restraining the hanging wall. In a typical mining environment, pillars of different rock mass conditions and geological characteristics are cut, resulting in variations in pillar strength. This is because pillars are highly anisotropic and cannot always be formed according to design dimensions. Consequently, unstable pillars may be present, requiring site-specific calibrated methods for ongoing monitoring and strength estimation. Pillar strength determination is typically accomplished using empirical formulae or numerical modelling. Although several numerical codes are available, mine sites still rely on empirical approaches despite their well-known limitations. Empirical methods are popular in the mining industry due to their simplicity. However, it is widely acknowledged that these methods can only be effective within the boundaries of their database and the specific problem scale for which they were designed. In contrast, continual monitoring of pillars and practical experience can enhance pillar strength evaluation. This work briefly describes pillar conditions at a case study mining operation. Additionally, a framework is proposed to estimate pillar strength based on ongoing pillar mapping, risk management decision making, numerical modeling, and analytical hierarchy process. 1. INTRODUCTION The room-and-pillar mining method is one of the most vital underground ore extraction methods in practice today. In this method, pillars are systematically left in situ to support the overburden weight of the overlying rock mass. If the rooms and pillars are not designed carefully, it can compromise safety or lead to sterilization of the ore reserves. Designing non-yield pillar systems for shallow hard rock room-and-pillar mines has always been a challenging task. It is important to know the stress distribution in the pillar and the strength of the pillar so that a sound design be produced. Due to the significance of these parameters, extensive research has been conducted on the strength of pillars in hard rocks. However, despite the numerous research outcomes, pillar failures still occur in underground room-and-pillar mines. The literature contains documented examples of such failures and their consequences (Esterhuizen et al., 2006, 2019; Malan, 2012; Ozbay et al., 1995).
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Wedding, Z., Z. Agioutantis e J. Calnan. "Preliminary Laboratory Results of Irregularly Shaped Specimens Modeled After Irregularly Shaped Stone Pillars". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0145.
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ABSTRACT Underground stone or hard rock mines typically employ the room-and-pillar mining method. Room-and-pillar mines are designed in traditional patterns with square or rectangular shaped pillars. This method is favorable because the symmetric pattern aids in optimizing mining operations. In active mines, deviations from the mine plan often result in irregularly shaped pillars. In older mines, which were designed when pillar design methodology was less developed, irregularly shaped pillars are more common than in current operations. The performance of hard rock pillars is primarily based on the pillar's stability factor and the width to height ratio, where the width is the smallest dimension of the rectangular base. The estimation of pillar strength in room-and-pillar stone mines has been studied by researchers and empirical relationships between traditional geometry (square and rectangular), and strength have been developed. Determining the strength of irregularly shaped pillars is integral to determining the pillar and regional stability. This paper presents preliminary laboratory results for specimens with irregular geometry that correspond to odd-shaped pillars and contrast to the strength of traditional specimens. Although a statistically significant difference between the UCS values measured for different specimen geometries was not established, preliminary results indicate that the intact core areas are of different dimensions. INTRODUCTION Underground stone or hard rock mines typically employ the room-and-pillar mining method. Room-and-pillar mines are designed in traditional patterns with square or rectangularly shaped pillars. This method is favorable because the symmetric pattern aids in optimizing mining operations. In active mines, deviations from the mine plan often result in irregularly shaped pillars. The performance of stone or hard rock pillars is primarily based on the pillar's stability factor, which is a function of rock mass strength and the width-to-height ratio of the pillar. Width typically refers to the smallest dimension of the rectangular base. The estimation of pillar strength in room-and-pillar stone mines has been studied by researchers, and empirical relationships between traditional geometry (square and rectangular) and strength have been developed (Esterhuizen 2006; Esterhuizen et al., 2011; Lunder & Pakalnis, 1997; Martin & Maybee, 2000). Determining the strength of irregularly shaped pillars is integral to determining the pillar and regional stability, as the effective design of an underground pillar will maintain the local and global stability.
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Moyo, S., T. Chikande, T. Zvarivadza, R. T. Masethe, A. C. Adoko, M. Onifade e A. A. Firoozi. "Investigation into the Rock Mass Response to Pillar Extraction in a Hard Rock Tabular Mine". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-1011.
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ABSTRACT: Historically, secondary pillar extraction has been successful in the soft rock mining environment. Several hard rock platinum mines have conducted selective remnant extraction with backfill as a regional support measure. A hard rock tabular platinum mine instigated the extraction within a non-yield pillar layout without backfill support. The mine is situated within the Great Dyke of Zimbabwe in a shallow depth environment of approximately 100m. Pillar extraction without backfill in a hard rock mine is a novel mining method. A study was carried out to make a quantitative comparison between the various design parameters and the rock mass response measurements. The primary mining utilised the mechanised room and pillar mining method to extract ore from the wide tabular reef. Similar, low profile mechanised equipment with additional automated systems were adopted for ore extraction and transportation to the surface crusher. The risks associated with the extraction of pillars include large localised falls of ground due to wide spans, pillar run, high severity injuries due to windblasts and large regional collapses through to the surface. The pre-feasibility study for the mine layout design used MAP3D to assess the expected displacement and stress limits post-extraction. MAP3D uses the boundary element method of analysis and has an in-built CAD system for stress analysis and 3-dimensional visualisation of models. A monitoring strategy consisting of displacement, deformation, stress change, ground motion and groundwater level measurements was put in place to record the variations resulting from the pillar extraction. The rock mass response analysis aimed at trending the monitoring results, conducting a comparison to the design parameters and previous pillar collapse trends. Minor stress, strain, and displacement changes have been recorded within a period of one year since the project began with no visible deformation noted on accessible pillars. The current system was identified as including the hazard identification and first-pass monitoring stages. Real-time monitoring systems with a higher sensitivity are required to ensure long-term data retrieval and timeous emergency response.
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Ladinig, T., H. Wagner e M. Grynienko. "Need and Design of a Field Test to Improve the Knowledge on Strength and Behavior of Massive Hard-Rock Pillars in Deep Mines". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0400.
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ABSTRACT Pillars have a central role in an active stress management approach, which has been proposed for the extraction of thick tabular and massive hard-rock mineral deposits. A mining method making use of this approach, is the novel raise caving mining method. Initially, the pillars have width-to-height ratios of 5 to 10. In the course of stope extraction, the dimensions of the pillars are altered, namely the height of pillars is increased and the width of pillars may be decreased. Consequently, the pillar strength is reduced and pillar crushing is triggered. A stable crushing process must be ensured. Knowledge on the complete stress-strain behavior of massive hard-rock pillars is paramount for the design of these pillars. However, a review shows that there is insufficient knowledge available. An in-situ pillar test is found to be best suited to improve the knowledge. The need for, objective of and design of such a full-scale in-situ pillar test are discussed. An in-situ pillar test is planned in one of LKAB's underground operations in connection with the development of the raise caving mining method. The layout and sequence of the test and the current progress of design and open points in the design are outlined. INTRODUCTION Pillars are used in underground mining for several, different purposes. The tasks for pillars comprise regional support of the overburden strata (panel pillars), local support of the immediate roof strata (crush pillars), the separation of adjacent extraction areas (inter-panel pillars), the control of regional convergence and the associated limit of mining-induced seismicity and abutment stresses (stabilizing pillars) and the protection of critical infrastructure, such as shaft systems (protection pillars). This paper addresses massive hard-rock pillars, which take over a central function in an active stress management strategy in massive deposits or in thick tabular deposits. Due to the shape and dimensions of the deposits and the considered purpose, the pillars are massive and they have a width and height in the range of several tens of meters and a length of up to and more than hundred meters.
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Belzer, B. E., e N. Gupta. "Three-Dimensional Salt-Pillar Equations and Their Applications to Industry". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0566.
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ABSTRACT Salt-pillar equations were developed over 25 years ago to assist with mine design. Pillar design is important for salt mines because the pillar size influences convergence of underground drifts with equipment clearance and headroom constraints, subsidence at the surface, and functional life of ground support. Current methodologies for salt-pillar design include using numerical-modeling techniques and salt-pillar-design equations as a method for estimating stresses and deformation rates. In this paper, three-dimensional simulations of square and rectangular salt pillars were performed, and the results were compared to the estimates of stress conditions using the salt-pillar-design equations. The results were used to investigate if the same salt-pillar-design equations are still valid following advancements in numerical-modeling software and the constitutive behavior of salt. This paper (1) reviews the salt-pillar-design equations, (2) compares the estimated stress conditions using numerical-modeling methods with the salt-pillar-design equations, and (3) discusses applications for the use of salt-pillar-design equations to salt mine design. INTRODUCTION The room and pillar size play a crucial role in the viability of an underground mine. Even for extensive mineral resource mines such as salt, pillar design influences the roof-to-floor convergence rate, stability of the salt back and nonsalt units, and accessibility period of mine workings. Unlike hard rock or coal mines, time-dependent deformational behavior of salt increases the pillar design complexity in underground salt mines. With technological advancement and laboratory creep tests on salt specimens, site-specific creep laws can be determined, and sophisticated numerical models can be developed to predict the room-and-pillar response over a specified period. Van Sambeek (1996) presented that the simple pillar-design equations for salt pillars can reproduce the results of extensive numerical models, such as stress conditions in salt pillars. The premise of the Van Sambeek salt-pillar-design equations is that the average values of the vertical stress, the two horizontal stresses (as compared to their actual distributions), and the corresponding deviatoric of those average stresses are adequate to estimate the pillar's creep behavior and structural stability. Therefore, the salt-pillar-design equations relate the stress averages to the shape of the pillar in terms of its height-to-width (H:W) and height-to-length (H:L) ratios.
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Deng, Jian. "The induced mechanism of pillar rockbursts in deep hard rock mines". In Seventh International Conference on Deep and High Stress Mining. Australian Centre for Geomechanics, Perth, 2014. http://dx.doi.org/10.36487/acg_rep/1410_49_deng.
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Bahrani, Navid, Soheil Sanipour e Farzaneh Hamediazad. "The strength of massive to moderately jointed hard rock masses for tunnel and pillar designs". In Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, 1123–34. , Perth, 2024. http://dx.doi.org/10.36487/acg_repo/2465_73.
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Yao, M., e D. Landry. "Seismic Risk Management Practices at Vale's Sudbury Operations". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0616.
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ABSTRACT: Vale Base Metals has been operating many underground mines in the Sudbury Basin for over a century and all mines have experienced a significant increase in the number of major seismic events over the last decade. Various mitigation strategies have been developed at Vale's North Atlantic Operations in Ontario to manage and control the risks associated with seismicity and rockbursts. The mines have seen a significant increase in the number of large seismic events, but the overall trend of rockbursts is decreasing. This paper will focus on Seismic Risk Management Strategies developed over the last decade, including both strategic and tactical control measures. Examples will be given in the paper to demonstrate the effectiveness of control measures over the last decade. Recent developments in Seismic Hazard Assessment for burst prone ground conditions are also presented in this paper. Although the strategies presented in this paper can be applied to other deep hard rock underground mine operations that face similar challenges with burst-prone ground conditions, they should be applied with caution and tailored for site specific conditions. 1. INTRODUCTION Vale Base Metals has operated several underground mines in Sudbury for over a century, and currently five mines are active (Coleman, Creighton, Copper Cliff, Garson, and Totten Mines). Numerous mining methods have been employed including cut and fill, post pillar cut and fill, and sub-level caving, however, currently the primary mining method employed is open stoping. The primary rock mechanics challenge at these operations is seismicity and rock bursting. Figure 1 shows a recent rockburst at one of the mines which was associated with a large seismic event. Seismicity has been observed to be primarily linked with: • Late stage of extraction: sill and diminishing pillars • Brittle and high strength rocks (UCShost > 200 MPa) • Mining depths between 1.5 and 2.5 km below surface • Lack of confinement due to higher extraction ratio • Presence of seismically active geological structures A Seismic Risk Management Plan is an important element at any seismically active mine and is also a legal requirement in some mining jurisdictions. The following main items are key requirements: • Responsibilities • Microseismic Monitoring & Data Analysis • Seismic Hazard Assessments • Hazard Mitigation Plans/Strategies • Training This paper will focus on two key requirements described above: Hazard Mitigation Strategies and Seismic Hazard Assessments.
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Putra, F., Hasan R. Meiharriko e J. P. E. Hamman. "The Geotechnical Aspects of a Pillar Recovery Project in the DOZ Cave Mine". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0292.
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ABSTRACT The Deep Ore Zone (DOZ) mine is a part of the PT Freeport Indonesia (PTFI) underground cave mining complex. It is the third lift in the Ertsberg East Skarn System (EESS). These mines are located on elevations between 3,000 to 4,500 amsl in an area with very high rainfall of approximately 5,500 mm per year. A significant challenge in the operations of the DOZ mine is the handling and management of wetmuck. As mining progressed since the start of production in 2000, the percentage of wetmuck drawpoints increased dramatically against the dry muck drawpoints. This condition impacted the ore blending strategy in the ore pass systems to mitigate the ore spill hazard in the ore flow systems. To overcome this dry: wet muck ratio problem, an option for pillar recovery to increase the dry muck tonnages was evaluated. Pillar recovery strategies along the major pillar apexes in inactive extraction levels was initiated. This challenging project took place in six panels between 2019 - 2021 and had to deal with a long history of abandoned areas, active wetmuck issues, closed drawpoints and panel instability concerns. This paper aims to provide an overview on the management of the pillar recovery project, geotechnical assessment of pillars and wetmuck to ensure safety and production targets are met. INTRODUCTION The Deep Ore Zone (DOZ) cave mine is a part of the PTFI underground mining complex that implement the block cave mining method between 3,000 to 4,500 amsl. DOZ mine is the third lift in the Ertsberg East Skarn System (EESS) orebody after the Gunung Bijih Timur (GBT) Mine and Intermediate Ore Zone (IOZ) Mine (Figure 1). The topography around these mines is extremely rugged and typical of the Jaya Wijaya Mountain range in West Papua, Indonesia. Wet weather with very high rainfall that averages 5500 mm per year (Widijanto et al., 2012). The very high rainfall combined with the block cave mining methods, that has broken through into the open pits or to surface, is one of the main contributors to the wetmuck at PTFI. Other contributing factors include lithology, fragmentation and draw rates (See Section 4.1 for detail Wetmuck Classification).
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Rylance, Martin. "Optimist, Pessimist or Engineer - Conductivity Based on Need Not Fashion". In SPE International Hydraulic Fracturing Technology Conference & Exhibition. SPE, 2022. http://dx.doi.org/10.2118/205286-ms.
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Abstract An optimist says the glass is half-full, a pessimist half-empty, whereas a good engineer says that the glass is twice as big as it needs to be. There has been much debate over the years about the relative functionality, application and even necessity of proppant in delivering effective hydraulic fractures. Often these debates have been directly linked to major changes in core frac applications, more recently in the dominant North American onshore unconventional market. However, the debates have all too often used broad or unclear brush strokes to describe shifting fracture requirements. Meanwhile, the developing oilfield in the rest of the world resides in more permeable areas of the resource triangle, great care must be taken to ensure that conventional lessons hard learned are not lost, but also that unconventional understanding develops. Over recent years there have been many debates and publications on the relative value of the use of proppant (and associated conductivity), although the true question was about appropriate fracture design in different rock/matrix qualities and environments. Certainly, the vast majority of fracturing engineers appreciate the difference between continuous proppant-pack conductivity and other techniques, such as infinite conductivity, pillar fracturing or duning designs. However, there is increasing evidence that conventional fracturing is suffering from populist attitudes, leading to ineffective fracturing. Additionally, and just as impactful, that unconventional fracturing continues to rely on the lessons learned and physics derived directly from our conventional experience but applying this in an entirely different environment. Primarily, the main concern is with the transfer of recent lessons learned and techniques utilised in one rock quality and environment, to an entirely different scenario, resulting in the misapplication, reduced IP30, poorer NPV or reduced long term EUR and IRR. Examples will be referenced where appropriate proppant selection and frac design can be the difference between success and failure. Fundamentally, we have not sufficiently developed our understanding of the role of proppant and conductivity, for application in unconventionals and thereby rely far too much on our previous conventional thinking. While at the same time we are exporting often inappropriate unconventional populist practice into very conventional environments, thereby potentially achieving the abhorrence of the worst of both worlds. This paper will describe and address scenarios where appropriate engineering selection, rather than popularity-based decision making, has resulted in a successful outcome. It will also attempt to ensure that we show the importance of studying your rock, in anticipation of engineering design, and that this should be a key consideration. The paper will also suggest that as an industry we urgently need to address our approach to consideration of conductivity, placement and importance and ensure that unconventional knowledge and learning progresses with a beneficial outcome for all.