Search Documents

By M. D. G. Salamon

It has been noted in recent years that the pillars in some bord-and-pillar workings scale or spall. In due course this process may result in the collapse of the affected panels. This paper presents a methodology for assessing the long-term behaviour of such workings, employing a simple model of pillar deterioration by scaling. It is assumed that scaling causes a gradual reduction in pillar width, hence the safety factor of pillars reduces in time. It is also postulated that the process of scaling will be arrested if the coal rubble around the pillar reaches a critical height. The probability that the pillars will survive for a certain period of time, or indefinitely, can be estimated. This can be accomplished by using the log-normal distribution proposed by Salamon and Munro4todescribe the distribution of the apparent safety factor values at failure. If an estimate of the rate of scaling is known, it is also possible to quantify, using a Monte Carlo technique, the expected life of the pillars. The method also facilitates pillar design by specifying a probability of survival for a given number of years or, alternatively, for an indefinite period. Using the limited pool of available data, analyses show that the proposed model does not appear to be inconsistent with observed behaviour of pillars in the Vaal Basin. The crucial parameter is the rate of scaling. Back calculations from eleven cases suggest that the rate of spalling in the Vaal Basin is about 0.2 m/year. It is noteworthy that two further cases in the same area give significantly higher rates (0.85 m/year). Some underground observations in the Witbank area indicate considerably lower rates in the order of 0.02?0.04 m/year. Further areas for study are recommended. These include a study of old workings to determine the extent and rate of scaling in the various coal fields, an investigation into the possible relationship between scaling and the chemical composition of the coal. In addition, model studies will be required to assess the practical impact of the research findings.

Jan 1, 1998

By M. Cornelius

Drilled shaft construction through caving soils has historically been an uncertain, risky and costly operation. Uncertain, because the zone of caving may or may not be known, risky because the loss of a shaft is disastrous, and costly because the Contractor, who faces these risks, must include large sums of money in his bid for shaft wall stabilization techniques. This case study will discuss the stabilization techniques that are typically used within the United States, and then present new technologies, born in Europe, that are being utilized in the States by Malcolm Drilling Company today.

Jan 1, 1999

In July 1982 the Committee on Underground Coal Mine Safety completed its study of safety in U.S. underground coal mines; the results of the study were published in the National Research Council report entitled Toward Safer Underground Coal Mines. One of the findings of this study was: THERE IS A STRONG CORRELATION BETWEEN MINE SIZE AND FATAL INJURIES. THE FATALITY RATE IN MINES WITH 50 OR FEWER EMPLOYEES IS NEARLY THREE TIMES THAT OF LARGE MINES (WITH OVER 250 EMPLOYEES), AND ABOUT TWICE THAT OF INTERMEDIATE-SIZED MINES (WITH 51-250 EMPLOYEES). Although the Committee explored possible reasons for the higher fatality rate in the smaller mines, it was not able to explain this phenomenon fully. Therefore the Bureau of mines requested that the Committee undertake a supplementary study of fatalities in small underground coal mines. The Committee met in the fall of 1982, discussed the problem, developed an approach to it, approved a program of statistical analyses, and authorized a panel of four committee members to explore the problem in greater depth. The panel, in turn, reviewed the results of the statistical analyses and met with the president of the National Independent Coal Operators Association and with several owners of small underground coal mines for a detailed discussion of the unique problems of small mines. Panel members examined 66 individual fatality reports prepared by Mine Safety and Health Administration (MSHA) inspectors who investigated fatal accidents that occurred in small underground coal mines in 1979 and 1980. This report is the result of those studies, analyses, and deliberations. The first draft was prepared by the panel, but the report has been reviewed and approved by the entire Committee.

Jan 1, 2011

By E. R. Bauer

Prolonged exposure to noise can cause permanent damage to the auditory nerve and/or its sensory components, known as noise induced hearing loss (NIHL). It is the most common occupational disease in the United States today. The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) is addressing NIHL in the mining industry through several research efforts. This paper presents a general review of NIHL, the status of NIHL in mining, the results of the longwall noise surveys, and a review of the longwall engineering controls research efforts.

Jan 1, 2008

By Virgil A. Marple

The primary purpose of this contract was to evaluate methods and techniques by which the size distribution acid concentration of mining-related dusts can be measured. One result has been the development of a portable, battery-operated optical particle counter/ multi-channel analyzer system which can he used to determine the size distribution and concentration of mining aerosols. One important aspect of this program has been the development of a calibration technique which relates the output of the optical particle counter to the penetration of the particles through an impactor: This results in a calibration curve in terms of the aerodynamic or Stokes' diameter or the aerosol particles. Using this technique, calibrations were performed on coal, silica, Arizona road dust, potash, and rock dust (corer ore) aerosols. Another task of this program was the calibration and evaluation of the GCA respirible dust monitors (RMD) 101-1 and 301. The results of evaluation showed that the instruments were within the manufacturer's specification of ±25% of the true mass concentration up to about 15 mg/m , if the dust particles were in a size range from about 0.7 to 10 µm aerodynamic diameter. Particles smaller tan about 0.7 µm were not collected by the instrument and particles larger than about 10 µm were lose in the inlet. Other tasks included performing field studies in cooperative research programs with the Bureau of Mines personnel, development of a portable polystyrene latex generator for use in optical particle counter calibrations in the field. The incorporation of impactor classification devices on the inlets of aerosol mass measuring instruments to give mass size distributions, and a study of the density of coal particles as a function of the particle size.

Jan 1, 1977

Mr G H Park was born and brought up in Zimbabwe, in mining from the University of the Witwatersrand. Starting as a Learner Official at Rand Mines, he went Mr D J van Niekerk was educated at Helpmekaar Boys' High School in Johannesburg and the University of Pretoria. Mr C J C Janse van Vuuren was educated at Klerksdorp High School, Pretoria Technical Colege, the University of Pretoria, and Unisa. He holds the folowing degrees: BSc (I&S), BSc Hons (Met Pta), ND (Met Tech), AEP (Unisa). Prof. R F Sandenbergh was educated at the Afrikaanse Hoerskool Germiston and the University of Pretoria. He holds the degrees of B Ing (Chem), M Ing (Chem), and D Ing (Metal). President's Award Professor Jannie van Deventer, Head of the Department of Metalurgical Engineering at the University of Stelenbosch, has been honoured with one of the five President's Awards for 1990. These awards are made by the CSIR's Foundation for Research Development. G R Bozzoli Awards* Prof. Alan Kemp, Dean of the Faculty of Engineering at the University of the Witwatersrand, has appealed to industry not to cut bursary funding during recessionary times.

Jan 1, 1990

By Y. Mitani, F. Vallier, T. Esaki

Shear-flow coupling tests are conducted using an original apparatus, and a shear-flow coupling model using Geographic Information System (GIS) is developed in order to evaluate shear-flow coupling properties of a rock joint. Shear-flow coupling tests indicate that the hydraulic conductivity of joint once decreases, and then rapidly increases at the shear displacement near the peak shear stress. The proposed model simulates the test results relatively well. However it indicates that it is difficult to apply the local ‘cubic law’ model in the initial shear stage, in which the change of selective flow path is remarkable. Scher-Fliess-Kopplungsversuche werden mit einem neuartigen Versuchsgerät durchgeführt und mithilfe von Geo-Informationssystemen (GIS) gedeutet, um so ein Modell für die Scher-Fliess-Kopplung in Gebirgstrennflächen zu entwickeln. Die Versuche zeigen, dass die hydraulische Leitfähigkeit zuerst abnimmt, dann aber schnell wieder zunimmt sobald die maximale Scherfestigkeit erreicht ist. Das vorgestellte Modell bildet die Testergebnisse relativ gut nach. Es zeigt auch, dass es schwierig ist, das lokale Cubic Law im Initialstadium der Scherbeanspruchung anzuwenden, in dem die Variationen selektiver Fliesswege gross ist. Les essaies hydro-mécaniques couplés en cisaillement sont réalisés grâce à un appareil éxperimental prototype et un modèle de couplage hydro-mécanique utilisant le S.I.G (systeme d'information géographique) développé dans le but d'évaluer les propriétés hydro-mécaniques des joint rocheux. Les résultats indiquent que la conductivité hydraulique des joints décroit puis augmente rapidement en se rapprochant du pic de cisaillement. Le modèle proposé simule relativement bien les résultats expérimentaux ; mais indique également qu’il est difficile d’appliquer localement la loi cubique au début du cisaillement où, les changements d’orientation dans le réseau d'écoulement sont considerables.

Jan 1, 2003

By J. L. Howell, D. E. Pollock, A. B. Cecala, A. D. O’Brien

Dust from worker,s clothes has been shown to be a problematic source of personal dust exposure. A recently completed effort between NIOSH and the Unimin Corporation has resulted in a quick and effective way to clean worker clothing. The process involves a booth under negative pressure with an air spray manifold to supply compressed air to blow off the dust from the clothing. The overall system is designed to meet MSHA and OSHA requirements. Results of field testing indicated that the manifold cleaned the clothes 10 times faster and removed 50% more dust than cleaning methods used by workers today.

By P. H. Oliver

"The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden.A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many blast effects which the current theory does not address and the need for adequate timing delays between rows. It improves on the design of inter-row delay timing by defining the length of free-blasted face needed in front of a hole *Retired from Inco Ltd., Sudbury, Ontario when selecting the delay element which will provide an adequate inter-row delay time."

Jan 1, 2003

By P. H. Oliver

The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden. A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many blast effects which the current theory does not address and the need for adequate timing delays between rows. It improves on the design of inter-row delay timing by defining the length of free-blasted face needed in front of a hole when selecting the delay element which will provide an adequate inter-row delay time.

May 1, 2003

By C. D. Messelt

The Bureau of Mines investigated the application of a diffusion model to sintering rate data developed for lithium titanium ferrite. The data were obtained by sintering pressed pellets under identical conditions for various times up to 11 hours. Stereological measurements were made on polished sections, and sintering rates were calculated. A model for intermediate stage sintering was fitted to the stereological data. This procedure produced a method by which these type data could be used to study the relative importance of volume and grain-boundary diffusion under a variety of sintering conditions.

Jan 1, 1979

By J. H. Rowland

The Mine Improvement and New Emergency Response Act of 2006 (MINER Act) amended the Federal Mine Safety and Health Act of 1977 to improve the safety of mines. The MINER Act established a Technical Study Panel (the Panel) to provide independent scientific and engineering review and recommendations with respect to the utilization of belt air and the composition and fire retardant materials in underground coal mining (1). Because frictional heating is a common cause of belt fires, the Panel recommended that the Mine Safety and Health Administration (MSHA) evaluate the drum friction test to determine if such a test would contribute to conveyor belt safety beyond that provided by the Belt Evaluation Laboratory Test (BELT). This paper compares the results of the drum friction test to results from the BELT and large-scale tests for six different conveyor belts. The results are used to evaluate the drum friction test as a method to determine the fire resistance of conveyor belts.

Jan 1, 2011

By Frank P. Frandina, Michael J. Loehr, Paul E. Gabryszak

The Heartland Corridor Clearance Improvement Project is part of a regional Public-Private initiative to allow double stack container trains a direct route from the Port of Norfolk through Virginia, West Virginia, Eastern Kentucky and into Central Ohio. In the Preliminary Engineering stage, 30 existing tunnels were assessed and 28 were found to need clearance improvements to allow the use of double stack trains. Alternative tunnel enlargement methods were developed to achieve the desired clearance improvements, while maintaining structural integrity and minimizing disruption to train traffic. This paper summarizes the geometric and condition investigations of the existing tunnels, as well as describes the preferred methodologies to achieve the desired clearance. The clearance improvements will be implemented beginning in the summer of 2007.

Jan 1, 2007

For the past four years, the Department of Mining Engineering at the University of Kentucky has conducted a validation study of the CFD Fluent code, by comparing its results against mining-related benchmark experimental data provided by NIOSH?s Pittsburgh Research Laboratory. This particular study is dedicated to the effect of machine-mounted dust scrubbers on the performance of face ventilation systems using extended-cut mining with a blowing curtain.

Jan 1, 2009

Development and Validation of Ore Characterisation Test and its Use in Variability Campaigns of Comminution Circuits Impact testing was developed by assessing the fragmentation characteristics of ore samples after controlled impact. Standard methods are, however, limited to relatively large and coarse samples, which thus precludes their use in early stages of projects, as well as where only drill cores are available. The method described in this paper is based on the same concepts of controlled ore breakage, but using relatively smaller samples. It is particularly useful in assessing the variability of ore characteristics in early stages of greenfield projects, as well as in predicting the performance of existing grinding circuits. A validation program was carried out in which a good adherence to the original test results was obtained. The results were used for (a) simulation of a copper comminution circuit as a function of the ore characteristics, and (b) evaluation of sampling protocols used for assessing fragmentation characteristics.

Sep 13, 2010

By William P. Blake

We are so familiar with water in its liquid and its solid form, that we seldom think of it as a mineral, and still less as a mineral product of any considerable industrial importance, though in the form of ice it is mined and stored up in enormous quantities yearly. The industry is peculiarly American, and in no other country has the business of cutting and storing ice been so well systematized and perfected. The interest has grown steadily from year to year, until it has attained large proportions, the annual production being counted in millions of tons, requiring, in the aggregate, a large investment of capital in all the Northern States. It gives employment, also, to thousands of men and horses, in the depth of winter, when farming work cannot be carried on. Ice is not only a luxury, but a necessity, in our climate, and is indispensable in many manufacturing operations: and finds constantly increasing applications and uses. As the industry has grown, so the necessity for suitable implements and tools has grown with it, and it has become necessary to systematize and cheapen the methods of handling such a large amount of material with rapidity and economy. As the industry is properly a branch of mining, and as our mining literature does not, to my knowledge, contain any description of the methods and appliances used in it, it seems desirable to place a brief description on record in our Transactions, and I therefore offer to the Institute the following outline description, based partly upon observations for several years past of the methods and processes employed, and partly upon the information obtained from prominent ice-miners and from the manufacturers of ice-tools. My acknowledgments are particularly due to the firm of W. T. Wood & Co., of Arlington, Massachusetts, for much information in detail, and also to the Knickerbocker Ice Company, of Philadelphia. The wood-cut blocks used in the illustration of this paper, have been kindly lent by both of these firms. The sequence of operations in getting ice is as follows : 1. Wetting down a light snow. 2. Scraping off an excess of snow, if present. 3. Marking out the field. 4. Ploughing and cross-ploughing. 5. Cutting the channel and detaching large floes.

Jan 1, 1883

By D R. Cohen

As one of the four basic sciences, the study of geology is intrinsically worthy as a means of increasing fundamental knowledge of the behaviour and evolution of the universe. Geological knowledge can also be translated into practical outcomes for society such as resource discovery and protection of the environment. Australia has a long tradition of providing very high quality geoscience programs to prepare graduates for a range of occupations. We are, however, reaching a nexus in the way universities should or can deliver engaging programs. This has been triggered by the rapid evolution of the digital world (the Internet of Things), new technologies, unprecedented access to information, better understanding of the processes by which we learn and adapt our thinking, growing complexity in the problems we must face or opportunities to grasp, and university funding models. Designing education programs for the next generation of geologists extends far beyond tinkering with syllabuses. We must develop skills sets that will allow graduates to work in rapidly changing landscapes, but in doing so may have to sacrifice content to build capability in our graduates. Whereas universities must respond to changing demands on graduates by ensuring degree programs contain an appropriate balance of material and high quality of delivery, industry and government must also fulfil their responsibilities to provide additional training programs for graduates to assist their rapid transition into independent professionals. This paper examines various educational issues being considered in developing the new Decadal Plan for the Earth Sciences, and reflects on directions that education is heading in many of our universities.CITATION:Cohen, D R, 2017. Educating the next generation of geologists, in Proceedings Tenth International Mining Geology Conference 2017, pp 3–10 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

Shaft sinking through an amphibolite-granite rock mass experienced rock bursts on the shaft walls and benches. However, rock burst phenomena was exhibited only in granite, which is e1asto-brittle with ability to store strain energy caused by orogenic and man made stresses. To improve ground conditions, blasting of destressing holes at shaft corners was carried out. By this technique rock burst during shaft sinking was minimized, but not eliminated.

Jan 1, 1982

By Robert L. Lagace

This final report documents the work dune by Arthur D. Little, Inc. (ADL) on behalf of the U.S. Bureau of Mines, Pittsburgh Mining and Safety Research Center (PMSRC), on Contract H0122026 (which began in August of 1971). Under this contract ADL provided technical assistance to the Bureau on a task basis on virtually all aspects of the Bureau's programs related to present and planned emergency and operational communications and miner location systems for underground coal mines. The work consisted of independent investigations, analyses, experiments, breadboard and prototype hardware development, workshops and technology transfer seminars on mine communications, and on-going evaluations and guidance related to the Bureau's contracted programs on electromagnetic noise, mine communications systems, and trapped miner location. This final report documents the work in two volumes, Volume I, "Emergency and Operational Mine Communications," and Volume II, "Seismic Detection and Location of Isolated Miners." The Tables of Contents of both Volumes are included in each Volume. Phase I of the contract was devoted to performing an in-depth assessment of electromagnetic noise measurements taken by several contractors and other investigators, and then defining a new noise measurement program and instrumentation system tailored to obtain the necessary but missing noise data. These data are required for use in the design of new emergency and operational communication systems. This work, and the follow-on coordination and guidance activities of ADL on this noise measurement program in subsequent phases of the contract, are treated in Part One of Volume I.

Jan 1, 1974

By Patrick Bermingham

The advancement of hydraulic impact hammers has followed the general advancement of hydraulics. The construction industry has been revolutionized by the application of hydraulics in excavators, cranes and, of course, in the hydraulic vibratory driver/extractor, which has become a standard tool. The innate ability to move a large mass with a very small displaced volume has given hydraulic power the advantage over previous power mediums. Recent development of more specialized and complex seal configurations and compounds has greatly improved the reliability and permitted the use of higher pressures in hydraulic systems.

Jan 1, 1987