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By Vernon R. Shorter, Wayne N. Clark

Introduction Coal is the US's largest indigenous fossil fuel resource and is used to power 57% of this country's electrical generation (NCA, 1986). Congress, however, is focusing its attention on the acid rain issue and public sentiment is leaning toward further curtailments of SO2, NO, and particulates from utility and industrial coal-burning facilities. The Cool Water plant has proven that integrated-gasification-combined-cycle (IGCC) technology can reliably produce economical electrical power while limiting SO2, NOx, and particulates to a rate of only one-tenth of the federal New Source Performance Standards for coal-fired plants. Process water requirements at Cool Water are 40% less than those of a conventional coal-fired utility plant equipped with flue-gas desulfurization units for stack gas scrubbing, thus reducing waste water treatment requirements (Clark and Shorter, 1985). The IGCC technology employed at Cool Water has now been demonstrated to efficiently convert coal to electricity in an environmentally superior fashion. The Cool Water Coal Gasification Program is an unincorporated California association of six partners whose commitment is proving that the integration of gasification with combined cycle power production (IGCC) is commercially viable and environmentally safe. The 120 MW Cool Water plant began commercial production on June 24, 1984. The Program is operating it for a five-year commercial demonstration period. The Program is about halfway through this period. Much of that which was intended to be proven is now fact. In this mid-term assessment, the authors report that the com-

Jan 2, 1987

By G. Gutierrez, M. C. Fuerstenau, J. D. Miller

The response of pure goethite and two natural iron ores to flotation with potassium octyl hydroxamate is presented. The ores contained 12.5% and 39.7% iron; concentrates containing 69.5% and 61.5% iron, respectively, were obtained with additions of 0.4 lb/ton hydroxamate. Selective flotation of iron oxides from associated gangue minerals has proven difficult in the past with standard collectors, such as sulfonates and fatty acids. As a result, recent work has been directed toward silica flotation with calcium activation after the iron oxide surfaces have been blinded with certain starches.& The results obtained with this technique are encouraging. This method, however, involves depressing a mineral that would normally float under the conditions employed. A preferable method would involve floating the iron oxide because quartz is naturally depressed until activated. Earlier work involved this approach, but in view of the results obtained, collectors that exhibit greater specificity for iron are needed. During an investigation of chrysocolla flotation with potassium octyl hydroxamate, a metal chelate former, it was observed that pyrite floated well with low additions of collector.3 This phenomenon suggests that hydroxamate has a rather strong affinity for iron, and that other iron-bearing minerals should also respond to flotation with octyl hydroxamate. The object of this paper is to determine this response. The experimental work was divided into areas, the first of which involved microflotation experiments with pure goethite with an apparatus described previously.4 Goethite was selected because of the ease

Jan 1, 1968

On request of the Commissioner of Education, a small group of administrative professors of engineering and commerce from higher institutions near St. Louis met in conference with the Specialist in Commercial Education of the Bureau of Education on Feb. 22, for the purpose of discussing ways and means whereby the business of our country may be furthered through increased opportunity in our higher institutions for the preparation of engineers with business training. One or more representatives were present at this conference from the University of Minnesota, University of Illinois, Washington -University, University of Missouri, University of Iowa, Iowa State College, University of Kansas. It was recommended at this conference: First, That the Commissioner of Education appoint immediately a committee to consider commercial engineering in its various aspects and to prepare and approve one or more curricula in commercial and industrial engineering that can be recommended by the Bureau of Education for adoption in our colleges and universities. It was suggested that the committee consider the following curricula plans: First, That a minimum number of hours in business training be required in all engineering courses. Second, That a curriculum providing for a minimum of fifteen to thirty units in business economics be incorporated in all engineering courses and offered on an elective basis. Third, That a curriculum in commercial or industrial engineering, permitting full and proper emphasis upon engineering subjects, be offered in the School of Commerce with degree to be given in that school. Fourth, That a five-year combined engineering and commercial course he prepared.

Jan 5, 1919

By H. Verakis

A fire in a coal mine conveyor belt entry represent a major safety and health risk to miners. Fighting belt entry fires can be a commanding effort. If there is a failure of one aspect in the fire fighting needs such as a dissimilar hose-valve connection, then it can result in the inability to extinguish a fire. Fire incident data compiled over nearly 30 years for underground coal mines shows that fires in belt entries account for 15-20 percent of the total number of fires. Fires in the belt entries of coal mines have resulted in injuries and fatalities. New regulations have been promulgated that require an unplanned fire not extinguished within 10 minutes of discovery to be reported to the Mine Safety and Health Administration (MSHA). A fire that is not extinguished within several minutes may take hours or days to extinguish or may require sealing a section or the mine in some cases. The current fire protection regulations in the U.S. Code of Federal Regulations (CFR), Title 30, Part 75 are designed to prevent or control the fire hazards present in a belt entry. These requirements and other factors affecting belt entry fires are discussed, including fire detection and warning, fire suppression devices, type and location of fire fighting equipment, waterlines, and cleanup and removal of combustible materials. The fire suppression systems used to extinguish/control a belt fire and the effect of ventilation on the propagation of conveyor belt fires are also discussed.

Jan 1, 2009

By D Moss, P Ganza

There are continuing developments in underground narrow vein mining, from innovative mining methods using low-profile equipment to adaptations of current mining methods using equipment such as road-headers. The development of new mining methods and mining equipment has one purpose in mind û to extract narrow reef orebodies keeping dilution to a minimum, whilst maximising mining recovery. Achieving this will increase the head grade of the ore mined and reduce the tonnes delivered to the mill. Narrow vein mining in Australia has been limited to traditional hand held or mechanised drill and blast methods using existing æoff the shelfÆ equipment. Numerous trials have been undertaken using rock cutting technology and lower profile equipment, but these mining trials have not resulted in the full implementation of any new mining method or the adoption of low profile equipment in narrow vein mines as an accepted mining methodology. Mine operators in Canada and South Africa have teamed up with a number of equipment manufacturers and have taken steps to further mechanise and automate the mining of narrow vein orebodies, in particular to increase safety and productivity. The challenge to Australian narrow vein mining projects is to capitalise on work undertaken by overseas mining companies and equipment suppliers and to investigate the adaptation of low profile coal mining machinery to specialised metalliferous mining. With the inevitable fall in metal prices, it is necessary for Australian mine owners and mining contractors to apply these specialised methods and equipment to make narrow vein mining profitable.

Jan 1, 2005

By J. E. Schiller, S. E. Khalafalla

To improve technology for treating process water, US Bureau of Mines research has shown that magnesium oxide (MgO) has many advantages over lime or caustic soda for precipitating heavy metals. Sludge produced by MgO occupies only 0.2-0.3 times as much volume as the precipitate made wing a soluble base. While a settled, lime-formed precipitate is easily resuspended, the MgO-metal hydroxide sludge becomes cemented together on standing. Settling of the metal hydroxides from a dilute suspension is more complete than precipitates formed with other bases. Virtually any metal that can be precipitated by raising the pH can be treated using MgO. A three fold to fourfold stoichiometric excess of solid reagent is added. The mixture is reacted for five to 10 minutes. Polymer is added, and settling or filtration completes the process. Because of the greater cost of MgO compared with lime, large-scale practice of this technology will probably be limited to water containing 50 mg/L (3 gr per gal) or less of dissolved metals. For such dilute solutions, chemicals are not a large fraction of total treatment costs, so more desirable sludge properties might justify higher chemical expenses. While the MgO process is technically suitable for widespread application, the extent to which it is adopted will probably be determined by a trade-off between the greater cost of MgO compared with lime and the superior properties of the precipitates and their corresponding ultimate disposal costs.

Jan 1, 1985

By Joseph J. Yancik

In Moscow, the delegation received a briefing on the Soviet coal industry from First Deputy Minister Vladimir Fedanov. A similar briefing was given to us on the Donets coal basin by Deputy Minister S. Saratikyanz of the Ukrainian Coal Ministry. Lengthy technical discussions were held with the mines staff and research personnel at the institutes we visited. In addition, we had detailed discussions with key staff members of two combinats; Donetskugol and Tulaugol. In all these meetings, principal topics were matters of safety related to hazards associated with face mechanization, coal transport, methane gas control measures, gas outbursts, coal and rock outbursts, fire fighting and control, explosion suppression and control measures, and other related hazard factors. There was also much discussion on miner training, miners' attitudes toward safety and accident prevention practices, and preparation and enforcement of safety rules and regulations. It would be helpful to briefly review Soviet coal production statistics for comparison purposes with the U.S., and for the purpose of referencing some of the delegation findings mentioned in this report. For an excellent, comprehensive picture of Soviet coal production and other related fuel statistics, the reader is referred to Strishkov's, et d. report.1 Strishkov's estimates agree with the numbers given us by Coal Ministry officials except in clean coal tonnage. The figures of 604 million mt of clean coal out of a total production of 655 tons raw coal in 1972 is much higher than Strishkov's estimate of 375 million mt clean coal.

Jan 7, 1974

By T. L. Brekke, T. R. Howard

Stability of an underground opening can be defined in several ways. To geologists and engineers that are used to working in geological environments where the major parts of the works after careful scaling can be left unsupported during the construction period as well as during operation, any rock mass behavior that requires reinforcement, support or lining may be regarded as a stability problem. To colleagues excavating underground openings in geological environments that require continuous use of reinforcement or support and lining "stability problems" are often associated only with those parts of the work where "standard" construction procedure and method of reinforcement or support and lining is inadequate, and special measures therefore needed. In either case, a major objective is to assess the stability problems correctly -as far as possible at the planning stage -- and choose methods for excavation and reinforcement or support that will bring the opening safely and as economical as possible through the problem areas. INTRODUCTION It is not uncommon that stability problems associated with faults or seams have been described as "unexpected." This term has unfortunately been used to indicate that no one knew that the fault or seam existed prior to excavation. A careful review of documented cases where serious stability problems have occurred revealed that the existence of these zones most often was known, but that their behavior was incorrectly assessed prior to or during construction. Miscalculations have been made in terms of the type and magnitude of loads that developed, and in particular in terms of the time-dependant behavior.

Jan 1, 1997

By Finn Ouchterlony

INTRODUCTION Much of present fracture toughness testing con¬cerns chevron notched specimens (Newman Jr., 1984) since these, in principle, require neither fatigue precracking nor more registration than failure load to determine fracture toughness. Two such specimens which can be made from diamond drilled rock cores with minimal machining are the Short Rod (Barker, 1977) and the Chevron Edge Notch Round Bar in Bend¬ing or CENRBB Specimen (Ouchterlony, 1980). Even if the precracking property is especially valuable for a material like rock, practice has made the relative advantages of these chevron notched specimens much less apparent (Ouchterlony, 1982; Ouchterlony and Sun, 1983). Enough remains, however, to have the Commission on Testing Methods of the International Society for Rock Mechanics (ISRM) focus on them as standard configurations in a "Suggested Method for Determining Fracture Tough¬ness of Rock Material", which is in preparation. This paper presents material which supports the ISRM effort: 1. An experimental compliance calibration of the Chevron Bend (CENRBB or CB for short) and re¬sulting formulas. 2. Specimen tolerances, evaluation formulas, and loading rate requirements relating to both Short Rod and Chevron Bend Specimens of suggest¬ed standard proportions. 3. Some fracture toughness values obtained with the Chevron Bend Specimen. This material is mainly based on two reports (Ouchterlony, 1984 and 1985). CALIBRATION OF THE CHEVRON BEND SPECIMEN Preliminaries The specimen and basic notation is shown in Figure 1 together with a straight notched variety (SECRBB). Subscripts c and s are sometimes used below to distinguish between them. Assuming linearly elastic conditions the load point compliance [ ]

Jan 1, 1986

By Stanley D. Michaelson, Ben. H. Slothower

The depletion of most high-grade ore reserves coupled with growing demands for metals and fuels has made it necessary to bring into production increasingly lower grade deposits. Improvements in technology have made lower grade ores economically recoverable in spite of major increases in labor and material costs and the initial investments required to open new mines and build their metallurgical and service plants. To remain competitive, managements of mining companies must keep abreast of and exploit these often complex technical developments. The proper application of these improvements in technology requires extensive and detailed study. In addition, managements of mining and other industries are becoming more deeply involved in public affairs and the myriad of other nontechnical problems common to all industries. These involvements, plus the demands of evaluating technological developments as well as the necessary work related to the routine administration of operations, have required mining managements to delegate additional study and review functions to staff services. To help overcome the problems involved in adopting the best technologies, managements have generally expanded their engineering and research staff services. Integrated, base-metal-producing companies, having open pits, concentrators, smelters, and refineries, are generally more research and engineering oriented than are most smaller mining companies and quarries. However, mining methods for even the simplest open pits and quarries are improving rapidly, and installations of these improvements are essential to combat increasing costs. Because of this, the managements of smaller operations may also require enhanced engineering staff services to realize the potential benefits.

Jan 1, 1968

By Teder R. I., M. M. Protodyakonov

In order to find an empirical relation between a quantity F and (m) independent variables or factors, each of which take (n) different values or levels, it is necessary to conduct nm different experiments (all possible combinations of the factors), each of which has to be repeated a few times (usually five) due to the scattering of the data. The total number of such experiments is very large, thus for example, when m = 4 and n = 5, it is equal to 5.54 = 3125; and very rarely is it possible to conduct such a number of experiments. Various possible methods of planning partial experiments are illustrated in Fig. 1. Each method shows a large combinative square consisting of five columns and five rows of middle squares, each of which, in turn, is further divided into five columns and five rows of cells. Such a partition corresponds to a plan of an experiment with four factors, each of which takes five different levels. The blackened cells indicate the combination of factors in a partial experiment. The total number of experiments is reduced on the basis of the following considerations: a) The effect of only a few levels of some factors is studied (Fig. la). Such an investigation gives no information on the effect of some factors, therefore it cannot be accepted as satisfactory; b) By reducing the number of levels of each factor; in such a case it is not possible to obtain an empirical relationship, but only whether some factors have an effect. This is evidently inadequate;

Jan 1, 1971

By Donald J. Olson, Thomas J. Lutzenberger, John Ramage

The North Shore Inline Interceptor, Phase IA tunnel is a 8,550-meter (28,000-ft) interceptor tunnel currently being constructed by Traylor Bros./Frontier-Kemper, Joint Venture, using a 9.8-meter (32-ft - 4-in) diameter Robbins tunnel boring machine (TBM). This tunnel is being driven in Silurian age dolomite approximately 91.5 m (300 ft) below ground surface. Significant water inflows were encountered when the tunnel drive penetrated the thinly-bedded Waubakee Formation. Flow increases approaching 0.75 cu m per min per 30 m of tunnel (200 gpm per 100 ft) have occurred in this formation. After driving approximately 2,285 m (7,500 ft) of tunnel (200 m full face in the Waubakee Formation), total flows exceeded 12 cu m per min (3,200 gpm) with about 5.7 cu m per min (1,500 gpm) entering the tun¬nel from the 200 m (600 ft) of exposed Waubakee Formation. Additional water control measures consisting of increased pumping capacity, increased water treatment capacity, surface grouting ahead of the tunnel, grouting ahead of the tunnel face and panning to improve the working environment for installation of tunnel support, were implemented to deal with the large water inflows. Currently (January 24, 1989), 3,400 m (11,000 ft) of tunnel has been driven, total water inflows are in the range of 11.7 cu m per min (3,100 gpm) with only 6.8 cu m per min (1,800 gpm) inflow from about 1,220 m (4,000 ft) of tunnel driven full face through the Waubakee Formation.

Jan 1, 1989

By John F. Vynne

This paper will discuss several of the systems and processes that have been developed over the past few years, and are now being utilized by major mining companies on draglines in North America, Australia and South Africa. These technologies include production monitors and reporting systems, GPS navigation systems, structural integrity monitoring systems, structural analysis studies to increase the dragline RSLs, and inspection and response strategies. The use of these technologies provides significant increases in dragline production, and reduces maintenance costs and downtime. The question that needs to be asked is what value is there in monitoring? Increasing dragline productivity is dependent upon to two items with the overall goal being to maximize the number of bank cubic meters moved and to uncover more coal: 1) maximizing payload and 2) maximizing the number of cycles. If you do not measure and try to optimize the parameters that impact payload and number of cycles, there is very little chance that you can improve overall dragline productivity. These parameters are: Maximizing payload is dependent upon the following: ? Geology ? Blasting ? Monitor weighing accuracy ? Engage location ? Disengage Location ? Rigging ? Suspended load ? Bucket characteristics ? Operator skills ? Minimizing rehandle Maximizing the number of cycles depends upon maximizing digging time, and minimizing cycle and delay/down times by: ? Minimizing Operational Delays ? Minimizing Mechanical Delays ? Minimizing Idle time ? Minimizing Walking time ? Minimizing Fill Time ? Minimizing Swing Angle ? Maximizing Swing & Return Rates ? Minimizing Spot Time A third reason to monitor, conduct structural analysis studies, and have inspection strategies is to prevent catastrophic failures such as shown in the following photographs (figures 1 & 2).

May 1, 2008

By Jon T. Langstaff

The microseismic method of detecting instability and high-stress zones in underground mines was first developed in this country by the US Bureau of Mines in the early 1940's (Obert and Duvall, 1957). Early laboratory experiments showed that when competent rocks are stressed in a testing machine, the rock noise rate (number of rock noises per unit time) increases with increasing applied stress. This increase is more pronounced as the ultimate strength of the rock is approached. Subsequent testing of rock noises in underground mines confirmed this laboratory experience and much effort has been directed in recent years to make use of this property to develop a practical method of predicting rock failure. Investigations conducted in the Coeur d'Alene district mines have pointed out a definite relationship between the stress buildup in a rock mass caused by mining activity and the emission of audible and subaudible seismic activity (microseisms). In 1968, a concentrated joint effort by USBM Denver Mining Research Center and American Smelting and Refining Co. at Asarco's Galena mine was undertaken to verify several theories regarding the generation of microseisms (Blake, 1971; Blake, Leighton, and Duvall, 1974; and Kovacs, 1973). Findings indicate that (1) rocks under stress emit detectable seismic energy; (2) the energy source can be located using a triangulation method involving travel time differences to various receiving stations; (3) the rate of release of seismic energy increases with increasing stress; and (4) this increase in noise generally precedes a major rock failure (rock burst).

Jan 1, 1979

By John A. Graves

Anaconda's Jackpile-Paguate mine, located between Albuquerque and Grants, N.M., is situated at an elevation of 6000 ft in a semi-arid desert region. The original Jackpile deposit was discovered by Anaconda air and ground exploration parties in Nov. 1951. A large percentage of the uranium mined in New Mexico comes from the Jackpile-Paguate, which is one of, if not the largest, open pit uranium mines in the world. From 1953 to the present, 120 million tons of overburden, mining waste, and low-grade material have been removed to produce approximately 10 million tons of merchantable uranium ore, having an average grade of about 0.25% uranium oxide. Identifying the Orebody Surface drill holes delineate the ore bodies on a predetermined grid which varies in dimension but usually affords 100-ft control. These holes are probed immediately after drilling by geophysical logging trucks, resulting in a gamma log and digital readout from each hole. From this information it is possible to arrive at an almost immediate conversion to percentage of U3O8 on 6-in. intervals. Initially a hole is probed at a reconnaissance speed of 10 fpm with a time constant of 8 sec. Wherever the gamma recording goes off scale on an initial run, that particular zone is rerun at 2 fpm and at a time constant of 2 sec. This time constant is the interval that emissions are counted and accumulated for recording purposes. The search radius of the Geiger probe is approximately 18 in.

Jan 8, 1974

By Christine Wenzl, Andreas Filzwieser, Stefan Konetschnik

"The METTOP-BRX-Technology is a novel manifold electrolyte inlet, which allows improved productivity and production in new and existing tankhouses by achieving higher current efficiency and cathode quality, as well as using current densities higher than 400 A/m2. Two installation examples are shown: Montanwerke Brixlegg AG, Brixlegg, Austria (upgrade of existing tankhouse) and Xiangguang Copper, Yanggu, China (new tank house). Montanwerke Brixlegg AG has been using the METTOP-BRX-Technology since 2005, and converted half of the whole tankhouse to METTOP-BRX in 2011 in order to use a current density of more than 400 A/m2. Xiangguang Copper started up their second tankhouse in May 2011. This tankhouse was constructed in the same way as the existing tankhouse, but was designed for 292,000 t/a cathode copper (existing tankhouse: 200,000 t/a) by using the METTOP-BRX-Technology. This production increase is a consequence of a much higher current density, namely 410 A/m2, compared to 280 A/m2 in the old tankhouse.IntroductionCopper electrorefining has been practised for more than hundred years, the last big change being the implementation of stainless steel cathodes in the 1980s [1], In 2005, the METTOP-BRXTechnology was first introduced. This technology was developed jointly by METTOP and Montanwerke Brixlegg, Austria, and allows improvements in productivity and production in new and existing tankhouses in an economic way. The METTOP-BRX-Technology is a novel manifold inlet that allows improved tankhouse productivity by increasing current density and/or current efficiency while maintaining or improving cathode quality [2]."

Jan 1, 2012

Exploration risk increases with time, due to a general decrease in prospectivity as the more accessible deposits are found, and be- cause of rising costs and demands due to an improving standard of living. Risk is separated into financial risk, which increases sharply at the development stage, and the risk of failure which is at its peak at the outset of exploration. Risk is also divided into internal and external factors; some of the latter cannot be offset, viz. the systematic overall risk for any enterprise. The recently emergent risk embodied in withdrawal of large areas from exploration access is discussed. An appeal is made for objective multiple land-use policies to be applied so that land remains available at reasonable cost and with appropriate environ- mental safeguard conditions. Risks specific to gold exploration are discussed. As gold now accounts for over 50% of all mineral exploration, and most other metals are depressed, any sharp decline in gold will have grave effects on the ex- ploration industry. Gold exploration will become more difficult and expensive in about five years, after most of the readily accessible deposits in Australia are found. Government's role is important in pro- viding stability and basic data at reasonable cost. Exploration for specific minerals or of particular areas could be stimulated by extending the 150%.tax deductibility of R & D to aspects of exploration of strategic im- portance, particularly in the event of a downturn. Exploration is classic scientific research, at least through to the proving Stages.

Jan 1, 1987

The dictionary defines 'jargon' as "barbarous or debased language ". This description does not suffice. Quiller-Couch has said, it is "a kind of writing which, from a superficial likeness, commonly passes for prose in these days, and by lazy folk is commonly written for prose, yet actually is not prose at all ". The two main vices of jargon, he says, are "that it uses circumlocution rather than short straight speech", like the Babu who reported his mother's death by saying: "Regret to inform you, the hand that rocked the cradle has kicked the bucket ". Its other chief vice is that "it habitually chooses vague woolly abstract nouns rather than concrete ones", like the newspaper statement, "He was conveyed to his place of residence in an intoxicated condition", instead of saying, "He was carried home drunk". Jargon is "an infirmity of speech", it is not journalese, but akin to it. "Like respect- ability in Chicago, jargon stalks unchecked in our midst" and renders much technical writing ridiculous. It deals in periphrasis instead of going straight to the point, it loves the abstract rather than the concrete, it dabbles in words of sound rather than of meaning. Avoid it, despise it, if you purpose earnestly to write well. "In literature as in life he makes himself felt who not only calls a spade a spade but has the pluck to double spades and redouble." * Jargon is rampant in technical publications. Catalogues and other advertisements are conspicuous offenders, but with these the critic is not concerned, except in so far as such 'write-

Jan 1, 1931

By D. Valic

In 1997, 9.2 million tonnes of mined, recoverable copper was produced, of which, 1.8 million tonnes or 19.4% was produced by leaching, solvent extraction and electrowinning. The amount of copper produced by this method grew faster than those attained from concentrate smelting, signifying the growing importance of this low-cost production method. Statistical experimental design, unlike traditional approaches, allows for proper distribution of experiments within the boundaries of factors being studied such that the number of experiments required to develop a sound relationship between the factors and a response is minimized. In the past, very little use has been made of statistical experimental design in copper electrowinning studies. Traditional one- variable-at-a-time approaches are widely employed for this purpose. The present study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A/m2), copper concentration (25 and 65 gL), and temperature (40 and 60 °C). Pure synthetic electrolyte with a constant acid concentration of 180 g/L was used throughout the study. The designed study produced a linear relationship where the independent variables of current density, copper concentration, and temperature, and their interactions, were found statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to be incorporated into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.

Jan 1, 1999

By Martyn F. Roetter

The work of the operational communication systems' group dealt with a range of communication needs and functions within mines, primarily along haulageways, to and within sections up to the working face itself, and in mine shafts. A mixture of communication techniques and hardware is needed to satisfy this variety of communication needs within the differing environments encountered in U.S. mines. Substantial progress, both experimental and theoretical, has been made in recent years towards developing alternative communication systems suitable for use in mines which are based on "guided" waves, including wire-less (waveguide-like propagation in mine tunnels) and wire-based systems (leaky coaxial cables or wires) . Major priorities identified for further work needed to confirm (or deny) the applicability, and refine the operational specifications of promising communication systems for mine use include: Short-Term Projects o Cost/performance analyses of promising leaky coaxial cable and UHF radio communication systems which require further data from: - Experimental investigation under U.S. mine conditions of the performance of potentially applicable leaky coaxial cable communication systems developed in Europe (France, Belgium, and the U.K). - Cost estimates on these coaxial cable communication systems. - Measurements of UHF radio propagation in low-coal mines. - Investigation of the influence of obstacles (e.g. shuttle cars and section machinery) in the entries on UHF radio propagation in mines. o Investigation of the problems of transmitter and receiver coupling and termination matching associated with the two-way propagation of low frequency radio waves in hoist shafts.

Jan 1, 1973