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By N. S. Tanious

This paper summarizes the results of an investigation into possibly the largest coal pillar failure in the USA. The newly opened drift mine is located in Southeastern Kentucky and worked an 11 feet thick coal seam, all other mines in the District worked seams 4-5 feet thick. The initial mine development consisted of 14 main entries (Fig. 1) which were driven in two sets of 7, under increasing depth of overburden. As the left seven entries came under deeper overburden the pillar ribs began sloughing which caused many of the concrete-block ventilation stoppings to crack. The mine management stopped the advance in the left seven and continued with the right seven entries. During the spring of the following year development resumed in the left seven, rib sloughage occurred again and this time severely cracked many stoppings and many were totally disintegrated from the excessive deformation. Within few weeks the sloughage was so heavy that many of these entries behind the active face were filled with piles of sloughed coal slabs. When the face reached a depth approximately 1150 feet, the sloughage became a slow, massive squeeze. The entry convergence (closure) reduced their height from 11 to 7-8 feet and the squeeze spread back to shallower depth covering an area roughly 300 pillars.

Jan 1, 1989

By C. J. Kirkland

The paper describes the arrangements for the casting, curing and handling at the casting yard, of the concrete segments for the lining of the UK half of the tunnel, and the plant used for the handling of these linings at the construction site. An outline of the tunnel boring machines being used is given, with particular reference to lining handling and erection, and the extensive muck disposal systems installed. A general progress update will be given to the conference.

Jan 1, 1989

By D. R. Barker

The economic performance and competitiveness of a concentrator are dependent on the production of accurate real-time assay information and the manner in which it is utilized. Our paper describes the relative merits of on-and in-stream analysis techniques and the economic significance of Assay-Based control and Target Oriented Display Systems. At Outokumpu's pyhasalmi Concentrator, a Flotation Expert Display System aids the process operator to make better decisions and provides guidance on the most efficient method of achieving the desired control objectives.

Jan 1, 1989

By R. L. Beatty

The Bond International Gold (BIG) Colosseum Gold Mine was discovered in 1865, but no recorded production occurred until the 1930's, with production approximately 19k9 (615 oz) of gold. The mine was closed in 1942 as a non-essential industry during World War II. The property was acquired by Dallhold Resources in mid 1986. Construction of a 1.1 million Mt carbon-in-pulp, cyanide mill started in November, 1986, and was completed in September, 1987. Minable reserves are estimated to be 9,560,831Mt (10,539,000St), with an average grade of 2.1 g/Mt (0.062 oz/st). This paper describes a general view of process flow and plant equipment, as well as a look at the maintenance and operational problems encountered in the fist six months of operation.

Jan 1, 1989

By R. V. Ramani

It is common knowledge that there is an endless stream of possibilities, proposals, and projects - each representing a demand on available capital - for improving the mining company's performance measure. It is true that these proposals go through an increasingly stringent evaluation process as they move up the echelons of management for approval. Therefore, there is every reason to expect that a proposal or project accepted for deployment will make a substantial contribution to the organization's performance. The reality, too often, is otherwise. Castle (1985) reveals some significant insights into the difficulties in predicting the performances in the mining industry. A sample of eighteen mining ventures, which have been developed over the years, was selected by Castle to illustrate the problems. The actual performances were compared with the original projection. The sample encompasses both surface and underground mines, a large number of commodities, and a wide geographic distribution. The experiences in these mining projects were analyzed through answers to four specific questions.

Jan 1, 1989

By D. H. Warren

This presentation we hope will provide you with an orderly approach co mine and surface plant closure taken from our experience over the past several years on six different projects within the intermountain states. There is no magic to the approach. It is basic common sense and yet it is interesting how many of the specific details are overlooked due to the individual complexity of each site. Our attempt here is to share some of the issues that have confronted us on these six sites. Please recognize that it is impossible to be all inclusive. Of the six sites we have drawn from; two are mine, mill and smelter sites dating back to pre-1900, one is an industrial site dating back to the early 1900s, two are mill and concentrator sites dating from the late 1940s and one is a mining district site dating from the late 1800s.

Jan 1, 1989

By J. D. Megeath

In the October 1988 issue of MINING ENGINEERING, J.G. Wargo's paper discusses the problem of measuring and analyzing permeability, porosity, and fracturing in its relation to in situ leaching of disseminated gold deposits. This paper made me suspect that a good deal of information and analysis may have been done on this in reverse in the petroleum industry. Some years ago, I was involved with the US Geological Survey in a project studying the Devonian shale of the eastern United States. The Devonian shale contains gas deposits that have the characteristic of slowly seeping gas over a very long time period. To understand the rate of seepage, considerable study and analysis was done on the interrelationship of poros¬ity, permeability, and fracturing. The purpose was to find out how and why the gas could escape in the varying rates found in wells throughout the formation. It strikes me that this is the mirror image of the problem faced in attempting to understand how a cyanide solution will travel into a deposit. To possibly invent our own personal wheel a little faster, I would suggest a look at the work done on the Devonian shale. Some of it is contained in "Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," US Geologi¬cal Survey Open-file Report 82-474, 1982, and "Additional Data for the Estimates of Unconventional Natural-Gas Re¬sources of the Devonian Shale," Open-file Report 83-676, 1983. It is entirely possible that some of this previous work could shorten the time required to make in situ leaching of dissemi¬nated gold deposits a profitable technique.

Jan 1, 1989

By Lawrence Adler

[An innovative framework is proposed which most efficiently and systematically handles the large quantity of information needed for equipment failure and other non-performance analyses. It is based on the accepted engineering dimensions of mass (material), length (geometry), and time (MLT). To these are added human and machine factor. Several failure "Modes" are identified for each dimension, which are then subdivided into specific "Types". Material Failure Modes such as Separation and Slip are easily recognized, but others had to be established. Geometric Failure Modes are usually straight-forward, Obvious ones include Geometrics Design and Stability with more synthesized. Time Failure Modes are again largely self-evident such as Life and Chemical Effects, others are needed. Human and Machine Factors as failure modes are loosely assembled. The results contain strengths, but also organizational weaknesses which are noted. Lacking a better alternative its use is recommended.]

Jan 1, 1989

By Qing Wang

A longterm overburden removal plan can be realistic and optimum only when the cost and capacity profiles off the equipment assigned to the operation are taken into consideration. Therefore, the planning should involve the proper assignment of equipment capacity by insuring a timely investment and a timely replacement policy throughout the mine life. A dynamic solution algorithm has been developed, by which all possible truck fleet alternatives are evaluated for each year off the operation. Cumulative cost off the operation is carried throughout the analysis. The optimum solution is obtained by selecting the minimum cumulative cost at the last year and tracing backward the best fleet alternative for each year. The solution provides: 1. the optimum amount of overburden to be removed each year; 2. the best fleet to be assigned to the job; and 3. the best equipment replacement policy.

Jan 1, 1989

By Jr. Gambrell

Support characteristics of in-cycle trusses are analyzed using a photo-elastic model loaded by tightening a truss in the sequence normally used in an underground mine. Stresses in the roof at its center point and at the junction of the roof and rib are examined. Effects of zero tension and unequal tension in the inclined anchor rods are presented. Effects of simulated subsidence on stress in the roof surface and on tension in the separate truss members are examined. Conclusions are drawn relating to (1) the effects of tension in the inclined anchor rods on uplift and compressive stress parallel to the roof surface, (2) the effects of subsidence on stress in the roof surface and, (3) the effects of subsidence on tension in the truss members.

Jan 1, 1989

Diamond wire rock cutting is the most widely used technology in carbonate stone quarrying owing to technical performance and block face quality. Interest is also growing for siliceous deposits. This paper deals with the problem of optimum wire utilization under restrictions regarding a set of variables and parameters. A computer program of general applicability has been set up with the aim of studying the most suitable combination of technologies and the effect on the technical and economic results of bench geometry, overall quarry yield, market -stone value, quarry size as well as the quantity, productivity and price of human and material resources and their organization in the elemental working cycle. Two quarrying problems are considered as significant instances a granite and a travertine quarry. The results are illustrated and discussed.

Jan 1, 1989

By Samuel Polinsky, Lawrence W. Bierman, Wayne Perkins

[A column float beneficiation plant using 9, 8.5 foot diameter, cells was constructed by the Simplot Company and the Smoky Canyon Facility in the fall of 1986 and has been in operation since May of 1987. The float beneficiation process was developed jointly by the Simplot Company and the Bureau of Mines (Salt Lake City, Utah) which incorporates the Bureau's bubble generator design and chemistry system based around the reverse float technology, (Albany Bureau of Mines, Application of Carbonate-Silica Flotation Techniques to Western Phosphate Materials, Rule, Dallenbach , Larsen, RI8728, 1982) . This chemistry has been modified by Simplot in both patented and unpatented improvements. The objective of the beneficiation process was to reducethe A1203 content in the overall pipeline concentrate by 0.2 wt z. Therefore, a process stream was identified in the mill circuit which provided an opportunity to isolate and treat 1100 tons per day of poor quality phosphate concentrates The process allows recovery of approximately 15% of the mill concentrates, otherwise unsuitable for fertilizer production. The alternative would have been to waste this ore. Wasting would have resulted in considerable ore loss, increased mining costs and required additional products grinding. ]

Jan 1, 1989

By I. Longson

As a longwall coalface advances a caved goaf or waste region is left behind. Air flow takes place through this permeable goaf due to the pressure differentials existing across it and en route this leakage air picks up both heat and moisture. A marked deterioration in climatic conditions occurs in the face area at all points downstream of where this leakage air rejoins the main air-stream. This goaf heat source can make a very significant contribution, typically 30-40% to the rate of total heat pickup on an advancing UK longwall coalface with a VST of 40°C and hence on the climatic conditions that prevail at the return end and in the return gate of the face. The magnitude of the rate of heat collection from the goaf depends on a number of factors but it has been established that it is particularly influenced by the prevailing virgin rock temperature and the total flow rate of the leakage air. This paper proposes a model for the goaf based on a packed bed analogy and other assumptions required in order to evaluate the rate of heat pickup are identified. The outlet condition of the leakage air predicted by the model have been shown to correlate with underground measurements taken for a range of different production patterns with the face cutter at various locations on the face. The sensitivity of these predictions to variations in the input data has been tested and is commented on. At this stage of the development the capabilities and predictive limitations of the model are discussed. Further areas of investigation are suggested in order to improve the predictive ability and to extend the versatility of the model.

Jan 1, 1989

By H. H. Kleizen

The operation range and efficiency of dewatering apparatus are important factors in the selection of an apparatus for a given purpose. In this paper theories are presented allowing to predict these basic characteristics for different dewatering apparatus and compared with experimental and practical data obtained on coal and ore slurries.

Jan 1, 1989

By John Nadolski

Intensive hydrologic monitoring of the Powder river basin has been on-going since the early 1970's. Data were used in environ- mental assessments and for determination of hydrologic consequences associated with coal mining activities. For most coal mine operators, data collection has continued in this baseline mode with little or no statistical analysis of the data and with no statistical procedure established to detect changes in groundwater quality. For the past four years Powder River Coal Company has studied several statistical techniques to analyze groundwater quality. Three objectives were pursued: 1) to determine the baseline water quality for key aquifers; 2) to determine which wells could be deleted from the monitoring program without reducing monitoring effectiveness; and 3) to define a statistical test to determine water quality changes. Knowledge of the regional geo-hydrologic system was combined with an analysis of the water quality monitoring in order to identify homogeneous aquifer zones. All wells within an aquifer zone were treated as one population, and a t-test was used to determine the minimum number of samples needed to define the water quality for each aquifer zone. Results indicate that the data for each aquifer zone were nor- mally distributed and that groundwater quality could be defined using a fairly small number of samples. Because of the minimum sample size test, groundwater quality sampling was reduced by between 75 and 85 percent.

Jan 1, 1989

By Ava Walker

The first form of a surety bond was an honest handshake between two or more parties agreeing to a decision, and their personal guarantee of following through to completion. This has all changed. In 1895, the United States Treasury Department disclosed that $35 million worth of personal surety guarantees on file had become worthless. A law was then passed requiring all surety bonds, in favor of the United States, must be corporate surety bonds. Today, a surety bond is one of the nation's leading fi¬nancial instruments used to guarantee the completion of an obligation. One hundred-fifty years before cor¬porate surety bonds, outcrops near Richmond, VA, were being mined. These surface mines became under¬ground mines. Today, both are still being used to obtain a leading energy source, coal. Since that time, more than 5956 km2 (1.47 million acres) of coal mined lands have been reclaimed in the US (Coal News, August, 1987). More than 25,000 state and Federal mining permits cover¬ing 14,164 km2 (3.5 million acres) have been issued during the last 10 years. Coal production has exceeded 7.2 Gt (8 billion st). More than 5665 km2 (1.4 million acres) of mined land has been reclaimed by active coal mining opera¬tions and 267 km2 (66,000 acres) of abandoned mined lands have been re¬claimed by others. Reclamation bonds were freely writ¬ten in the 1970s. So why are they almost extinct today? Contract bond losses have been severe in the past several years, sureties reporting losses exceed¬ing 110%. But the same proof is not provided on coal reclamation bonds. A surety bond is generally required when one party has an agreement with another party, and that party wants a guarantee from a third party that a job will be completed according to the terms and conditions of a written contract. In the case of a reclamation bond, the surety company (surety) is the financial party. It extends the credit and a guarantee to the obligee (the State, Commonwealth, or Office of Surface Mining) that the principal (the coal operator/company) will complete the terms and conditions of the contract (the rules and regulations governing mining and reclamation). The Surety Association of America defines a surety bond as an agreement providing for monetary compensation should there be a failure to perform specified acts within a stated period. Webster's Dictionary defines surety in the following ways: "l: the state of being sure; 2a: a pledge or other formal engagement given for the fulfillment of an undertaking and; 3b: one who has become legally liable for the debt, de¬fault, or failure in duty of another." Banks never make accommodation loans. Either the loan is good or no loan is made. Surety companies feel the same way about surety bonds. In fact, the average person does not realize the dangers of becoming surety for another. How does a surety determine if a company is worthy of receiving surety credit? How is a coal account under¬written today for an obligation that may not be released for many years? When a surety company executes a reclama¬tion bond, it financially puts its name behind the coal company and its guaran¬tee that should the coal miner default on the obligation, the surety will fulfill the contract. How is the surety to determine if a coal company may still be in business five, 10, 20, or 40 years from today?

Jan 1, 1989

By Paul C. Miclea, Robert E. Murphy

The behavior of fire and airflows in a confined tunnel differ significantly from more familiar fire situations outside, due to the buoyant effect which tends to create a layer of hot smoke and gases flowing away from the fire near the crown of the tunnel, while air supporting combustion moves toward the fire beneath the smoke layer. A subway emergency ventilation system is designed to force air to flow through the tunnel, shifting the balance of heated air in the direction of the forced flow and avoiding the "back-layering" of hot gases and fumes. This paper presents a computer program, called the "Subway Environment Simulation" (SES), which can be used to predict airflows created by the emergency ventilation system. It utilizes the latest state-of-the-art analytical treatment of fires in enclosed spaces, including observations from mine fires and gas explosions. The program allows designers to reduce construction cost by identifying unnecessary ventilation shafts and by verifying fan capacities. In addition, the program allows the designers and operators to determine safe evacuation routes, in case of a train fire, by predicting the occurrence of back-layering. It can be used to determine when the ventilation system can control the direction of smoke movement to provide a clear and safe path for evacuating people and facilitate fire fighting operations.

Jan 1, 1989

By Thorvald Wetlesen

Computer controlled drilling is now proven technology. It was first introduced by the development of the Furuholmen system for a prototype three boom tunneling jumbo in Norway in 1978. Now, 13 rigs with this concept are in operation in Europe, 3. in mining in England and. 10 in tunneling elsewhere in Europe. The system is also adapted to roadheader guidance. Practical experience has shown that the computer control system makes it possible to drive tunnels with a more accurate contour thus reducing the total amount of rock excavated, and where a full concrete lining is required a reduction in concrete volume is achieved. The total tunneling economy is improved. In the future we expect to see a wider range of instrumentation on jumbos, from the simple direction instruments to computer guidance systems for monitoring only, as well as fully automatic drilling to a programmed drilling pattern. More compact and reliable electronics will be available. Systems with low power consumption will fit easily into flameproof applications. Cabling complexity will be reduced by connection of sensors to serial signal lines.

Jan 1, 1989

By G. Labonte

The behavior of four different redox sensing electrodes (gold spiral, black platinum, chalcopyrite, and galena) during roughing and cleaning flotation is examined and related to the flotation response. Although it is difficult to provide unequivocal interpretations of the different potentials measured, the results indicate that the solution potential (as sensed by the black platinum electrode) is different from that of the pulp potential (gold spiral) and is only weakly related to the flotation response. On the other hand, the potentials exhibited by the gold spiral and the two mineral electrodes are related to the floatation response. The gold and mineral electrodes exhibit different transcient responses during the addition of flotation modifiers (e.g. NaCN, SO2). These responses appear to be related to the reactivity of the minerals and could indicate the conditioning time required to achieve flotation or depression of selected minerals.

Jan 1, 1989

By Andrzej Wala, Tom Altman, Tom Hughes

The University of Kentucky Mine Ventilation Manager (UKMVM) is a system that contains Level Five knowledge bases and comprises an expert mine ventilation management system. The package uses production rule language (PRL) to interpret data monitored from sensors, e.g., for airflow, temperature, and concentration of gases, in an underground mining environment. Activated from the PRL knowledge bases are Pascal subprograms which (1) organize the monitored data to set up emergency consultations, (2) display graphic representations of a mine's ventilation network with the latest sensor readings, (3) provide interactive updating of mine ventilation parameters, e.g., resistance changes, revised flow requirements, and new regulator and fan settings. Also activated from these knowledge bases are programs which (1) monitor airflow, temperature and gas concentrations from a physical mine ventilation model and (2) adjust regulator openings and fan rpm's. Thus, as an expert system the UKMVM not only presents advisory consultations for underground environmental emergencies, but also serves as an interface between the monitoring and responsive control aspects in the continuous maintenance of normal mine ventilation.

Jan 1, 1989