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By J. D. Bennett

The degree of injury and days lost from work due to an injury are examined for selected electrical sources, occurring in conjunction with falls of the injured miner or with selected machinery, that could have been eliminated by use of diesel equipment. Although the number of electrical source injuries that could have been prevented is small relative to the total number of injuries during the period examined, many lost-time injuries could have been precluded and thousands of days lost from work could have been avoided.

Jan 1, 1984

By Donald J. Hill

To be successful, every organization within the mining industry must involve itself in researching and evaluating methods of loss control. The appraisal and evaluation of accidents and injuries is required to determine the costs of loss producing practices and conditions. This involves all of an organizations disciplines that concern themselves with a more efficient and cost effective organization. To come to know the cost of your safety program or how much is expended yearly for each employee on safety; to know what your safety costs are per man-hour or per ton-produced; to know what the health, medical and compensation costs are for any given incident are just a few of the important facts and figures that the safety management of a given organization needs to know to operate in the mining industry today.

Jan 1, 1984

By Paul H. Lu

Methods and results of measuring three basic parameters for ground stability control, ground pressure, strata movement, and geomechanical properties of mine rock are presented in this paper. It is found that these parameters can be measured in situ by simple and practical techniques with nonsophisticated and inexpensive instruments. Specifically, a drillhole dilation technique employing a cylindrical hydraulic borehole pressure cell (CPC) was used to determine the modulus of rigidity. Premining ground pressures were determined by pressure convergence tests with a combination of one CPC and two pre-encapsulated flat hydraulic borehole pressure cells (BPC) installed in a single drillhole. Abutment pressures and pillar loading were monitored with BPC's. Differential strata movements and bed separations were measured with self-recording 10-anchor-point extensometers. Roof-to-floor convergence was measured with self-recording convergence meters. Some applications of these in-situ-determined parameters to mine design and ground stability control are also discussed.

Jan 1, 1984

By K. J. Ladwig

The Bureau of Mines conducted a field investigation of the water quality in inundated underground coal mines in the Northern Anthracite Field, eastern Pennsylvania. Water samples were collected at multiple depths from nine abandoned mine shafts in the Wyoming Basin, ranging from 68 to 650 m (223 to 2,132 ft) in depth and intersecting as many as seven mined seams in a single shaft. The shafts were also monitored for fluid resistivity, fluid temperature, Eh, and pH using downhole instrumentation. The monitoring program showed that the formerly highly acidic mine water is now slightly alkaline. Sulfate concentrations decreased as much as 74 pct in the flooded workings and 54 pct at a mine water discharge from values reported in 1964 and 1968, respectively. These data are consistent with the inhibition of pyrite oxidation and gradual flushing of oxidation products in flooded mine environments. The monitoring program also revealed significant vertical stratification in water quality in five of the nine shafts, each characterized by two easily recognizable zones. The transitions between zones were sharp, marked by rapid changes in Eh, pH, and ionic composition, the upper zones being less contaminated than the lower zones. The development of stratification appears to be a function of shallow localized flow conditions, arising primarily from the relative positions of mine openings and structural features of the coalbeds.

Jan 1, 1984

By Robert L. Skaggs

Sixteen nonaqueous techniques conceived to replace the current aqueous scheme for separating hafnium and zirconium tetrachlorides were re- viewed and evaluated by the Bureau of Mines. The methods are divided into two classes: separation by fractional volatilization of the tetrachlorides, which takes advantage of the higher volatility of hafnium tetrachloride; and separation by chemical techniques, based on differences in chemical behavior of the two tetrachlorides. The criteria used to evaluate separation methods were temperature, pressure, separation factor per equilibrium stage, complexity, compatibility with existing technology, and potential for continuous operation. Three processes were selected as being most promising: (1) high-pressure distillation, (2) extractive distillation from a molten salt, and (3) preferential reduction of gaseous ZrC14. Any of the proposed nonaqueous Hf-Zr separation schemes must be supplemented with additional purification to remove trace impurities.

Jan 1, 1984

By Dae S. Young

A new probabilistic approach is introduced for slope stability analysis including adverse impact of blasting vibrations. The material strength within a slope area is randomized in this bi-variate joint probability analysis. To be a completely general engineering method, the new probabilistic approach employs the random variable transformation technique; the Hermite model of the Gaussian transformation function, which transforms the experimental histogram of strength values to the standard Gaussian variables. Because bi-normal joint probability is analyzed on the true probability region projected on the Gaussian transformed variable plane, it is an exact solution of slope stability based on the available sample data. Details of the probabilistic approach are given through a case study on an iron ore mine. The case study demonstrated that the probabilistic approach is effective and simple enough to be a routine engineering practice for slope analysis.

Jan 1, 1984

By Paul R. Thomas

This paper addresses the long-term cost and availability of primary gold production from the Republic of South Africa. Forty-four major producing or developing operations were evaluated. The analyses present estimates concerning 1) total refined gold potentially available from demonstrated resources, 2) annual production potential into the next century, 3) long-term weighted average total costs for underground mine production and surface waste reprocessing, 4) the expected annual decrease in gold production, and 5) the ability of other market economy countries to compensate for the anticipated decline in South African gold output. This paper draws upon the data and analyses of a recent Bureau of Mines, U.S. Department of the Interior, Minerals Availability Program appraisal that evaluated the worldwide availability of gold and silver from primary precious metal operations and as a byproduct of base metal production.

Jan 1, 1984

Improve the effectiveness of face ventilation systems in coal mines by minimizing leakage around line and check curtains. Approach In-mine surveys were conducted to determine current curtain construction techniques, their effectiveness and associated costs. In addition, performance characteristics of extensible curtains were evaluated. A total of 77 conventional curtains in 10 mines was examined for 12 important characteristics. Extensible curtains were erected in a full-scale model and examined for operational difficulties, effects of leakage, and air pressure. Survey Results The underground mine study identified four categories of face brattice construction ranging from simple to complex: 1. Simple suspension of the curtain from roof bolts with the bottom edge lying on floor. 2. Spadding of the curtain to the roof on about 12-inch centers and stabilization of the bottom edge with wood or rock. 3. Use of vertical props and spads with a base board for support on the bottom. 4. Use of vertical props with caps and bottom boards plus horizontal brattice support boards.

Jan 1, 1984

By Bernard S. Covino

The Bureau of Mines is conducting a study of methods to improve the efficiency of the process used to pickle stainless steels. A review of the literature on pickling of stainless steels showed that the chemistry of several process operations involved in the pickling of stainless steels is not fully understood, and that further research could improve the pickling efficiency. The benefits of this research would be a reduction in the annual loss of several thousands of tons of critical minerals such as nickel and chromium, and a reduction in the amount of solids and spent acid solution that are currently discarded. The conclusion from this review is that further research is needed in four operations that either directly or indirectly influence the pickling process: hot working, annealing, conditioning, and the actual operation of pickling, Laboratory studies of the pickling operation are presently in progress.

Jan 1, 1984

By J. A. Herbst

Ball mill grinding circuits can be subject to upsets that arise from variable characteristics of the feed ore. These upsets are transients in critical circuit variables such as ball mill mass holdup, circulating load, sump level, cyclone efficiency and product particle size. They may occur frequently so that the operation is continuously fluctuating or they may be of such magnitude that some of the equipment is overloaded, resulting in shutdown, or an undesirable product particle size. The feed ore characteristics that influence ball mill circuit behavior in this manner include the grindability of the ore, the eventual transport characteristics of the ore in the mills and the feed ore size distribution. Control strategies for grinding circuits using conventional proportional-integral (PI) control have limitations to their effectiveness in controlling against feed ore disturbances. The first of these are the interactive nature of two or more control loops on a single circuit. Under some circumstances they begin to fight each other, increasing control error and settling time. PI control loop gain constants can be tuned to give best response for some set of conditions but once these change, as they would with a change in the feed ore, they are no longer the "best" ones (Shinsky, 1967). Due to these limitations, alternatives to conventional PI control strategies have been investigated for grinding as well as other mineral processing operations. These alternatives, all computer-based, include self tuning regulators, decoupling control and optimal control (Herbst and Bascur, 1983).

Jan 1, 1984

Professor R.P. King holds a Ph.D. degree in chemical engineering, which he obtained at the University of Manchester in 1963. After that he lectured in the Departments of Chemical Engineering at the Universities of the Witwatersrand and Natal. From 1968 to 1973, he was Leader of the Chemical Engineering Research Group of the National Institute for Metallurgy at the latter University. Mr C.E. Fivaz, Pr. Eng., is Chief Consulting Metallurgist of Rand Mines (Mining & Services) Limited, and is responsible for the metallurgical activities of the Gold and Uranium Division and the Coal and Base Minerals Division of the Group.

Jan 1, 1984

By Peter M. Fozzard

A review is made of the actual costs of recent foreign mineral exploration programmes in third world countries. Target identification leading to the selection of areas, or macro-targets, must follow a well planned and defined series of steps. Suggestions are made with respect to this inter-active project development work. Potential revenues in the broad sense will always determine the overall economics of exploration but clear objective philosophy, good planning and adequate financing are essential for exploration success. Considerable opportunities exist for making important foreign mineral discoveries and broad selected suggestions are made for the identification of exploration areas in relation to high-grade and precious metal mineralization.

Jan 1, 1984

By R. W. Wittkopp

The Relief Canyon gold deposit is located approximately twenty- four kilometers east of the town of Lovelock in Northwestern Nevada. At Relief Canyon, the Late Triassic Grass Valley Formation has been thrust over the Late Triassic Natchez Pass Formation. The lower plate Natchez Pass Formation is composed of massive gray dolomitic limestone which is locally silty and sandy. The upper plate Grass Valley Formation is composed of shale, siltstone, argillite and quartzite. Gold mineralization at Relief Canyon occurs along the highly brecciated thrust contact between these two formations. Weak gold mineralization often occurs above the thrust in the Grass Valley Formation, however, most of the ore grade mineralization is present below the thrust in the brecciated Natchez Pass Formation or where the two formations are mixed as a result of movement along the thrust. Several types of gold mineralization have been recognized at Relief Canyon. A large amount of the ore is present as a jasperoid breccia, however, significant amounts of ore occur as a mixed breccia composed of upper plate rock, fresh limestone, clay and jasperoid breccia. Gold ore also occurs in a fresh limestone breccia which contains a large amount of clay. Below masses of jasperoid, jasperoid stringers containing gold extend into the fresh limestone. Gold mineralization at Relief Canyon appears to be truly disseminated and has the typically associated trace elements of arsenic, antimony, mercury and fluorine. The Relief Canyon deposit can be classified as a structurally controlled disseminated gold deposit. Other deposits that fit this classification are the Pinson and Dee gold mines.

Jan 1, 1984

By L. L. Oriard

There are certain site-specific geological and physical features of a rock mass which control its behavior under the dynamic stresses induced by the action of explosives. It is essential that blasting technology be adapted specifically to those features. There does not exist a single, simple "right" way for each type of blasting operation, but rather each operation must be custom-designed for each site. When this is done, it is often possible to produce unusual but highly desirable end resglts, such as undisturbed narrow rock walls, monoliths and square benches. Although the techniques illustrated here were developed specifically for "sculpture blasting", the geomechanics principles would apply to other types of blasting control, both large-scale and small-scale. Because the techniques are designed more for the purpose of modifying the site responses which would ordinarily be expected than they are to developing new "blasting formulae?, the name "Modified Site Response Blasting" will be used.

Jan 1, 1984

By Peter A. Hacquebard

"The coals of the Sydney and Pictou coalfields are generally classed as high volatile ""A "" and medium volatile bituminous coals but there are significant differences within and even beyond this rank. These are related to the observation that the coalification in eastern Canada is essentially post-deformational, resulting in a general increase of rank with depth in individual seams.Exploration drilling in the Sydney coalfield has shown that the rank increases offshore to M. V. bituminous at mineable depths and in the Pictou field to L. V. bituminous coal. There is also a marked easterly shift in rank within one seam at the same depth at Sydney, with the result that M. V. coal will be reached sooner in the Donkin Reserve area (at 700 m depth) than in the Lingan-No , 26 Reserve area (at 900 m depth). These rank changes are important for the manufacturing of metallurgical coke as shown with coke stability predictions based on petrographic analyses. The L. V. coal of the Pictou field can be used for blending purposes and is the only known L. V. deposit of mineable thickness in eastern Canada.In addition, the vertical rank changes between seams have been studied in ten boreholes. They are not constant within the confines of the Sydney coalfield. Four separate areas can be recognized, each with different coalification gradients, which can be related to changes in the paleogeothermal gradients . Variations of 2.5 degrees to 6. 7 degrees CI IOO m are indicated and geological causes for these changes are suggested.IntroductionThe Sydney coalfield is the largest and most important field in eastern Can ad a, and although it has been in production some 200 years, the remaining ""demonstrated "" resources of 1.6 billion metric tons can extend its production capability for at least another 100 years. All coals mined are high volatile "" A"" bituminous and have been used for both thermal and metallurgical purposes. For the latter rank variations even of a minor scale are of critical importance for the manufacturing of metallurgical coke.The significance at the present time of the Pictou coalfield, which has only modest remaining "" demonstrated"" resources of 60 million metric ton s, lies in the discovery in 1975 of a 14-million-ton deposit of low volatile bituminous coal. It is the only known low-volatile coal in eastern Canada and is suitable for use as a blend for metallurgical coal. As such, it could supply the Sydney coke ovens for a period of 30 years at the current rate o f coke production and replace imported American low volatile coal.Consequently, coal rank studies of the Sydney and Pictou fields are important not only from a geological point of view, but also because of economic considerations."

Jan 1, 1984

By J. M. Mutmansky

A number of previous publications have attempted to provide the practicing ventilation engineer with simple guidelines on the optimal velocity to be used in mine openings. Some of these velocities were meant to be used in metal mining operations and some were meant for coal mining. A careful review of these publications reveals that the optimal velocities were determined based upon assumptions that are not existent today. As a result, they are not suitable for use in a modern coal mine. This paper takes a new look at this problem and determines a statistical relationship for optimal velocity that can be applied under both current and future conditions. The analysis performed here is based upon the determination of the optimal velocity for coal mine entries under variations in power cost, mining cost differential, airway friction factor, time value of money, airway lifespan, and quantity of air carried. A total of 8400 different conditions were analyzed for optimal velocity using computer calculation of the capital and operating cost values. Using the individual values of the optimal velocity derived in the calculations, a linear regression equation was fitted to the data to relate the optimal velocity to the other six variables outlined above. This regression relationship allows the ventilation engineer to make an easy, rapid determination of the optimal velocity.

Jan 1, 1984

By S. G. Malghan

Flotation is the primary method for copper minerals separation from porphyry ores. The need to process difficult-to-float porphyry copper ores presents challenges to engineers and scientists in several areas. This paper is concerned with summarizing generalized problems faced in the processing of porphyry ores and treatment methods to overcome the specific problems. Though some of the problems are interrelated the problems have been classified into three broad catagories. The case studies of some of the successful applications of innovative methods to solve problems related to ore mineralogy, metallurgical aspects of ore treatment and process variables show that quite often the problems are solvable by a judicious choice of flotation variables.

Jan 1, 1984

By Steven J. Schatzel

Large-scale methane releases in dual salt mines have resulted in ignitions and mine fatalities as recently as 1979. Several past studies have implied that hazardous methane occurrences in U.S. salt domes are distributed neither uniformly nor randomly, but are geologically controlled and potentially predictable. A first step by the Bureau of Mines in addressing the problem of methane in deal salt mines required development of a new test to determine volumes of gases in solid salt samples. This report considers the results achieved when 80 deal salt samples were tested for gas content by dissolution in a controlled atmosphere chamber. Criteria were organized to delineate salt types based on geological occurrence. Outburst samples range from 0.014 to 7.4 cm3 CH4/100 g NaCl, anomalous salt samples from 0.0027 to 2.6 cm3 CH4/100 g NaCl, and normal salts from less than 0.0003 to 0.31 cm3 CH4/100 g NaCl. The presence of higher hydrocarbons was most common in samples containing larger quan¬tities of methane. The presence of higher hydrocarbons appears to be useful in detecting methane hazards where some methane may be lost before gas content testing. An exploratory rotary and/or core drilling program, dissolution testing for gas content, and up-to-date geologic mine napping could allow a mine operator to assess methane hazards in dual salt.

Jan 1, 1984

A subsurface study of the Maria Lode and associated hydrothermal alteration of andesites within the Karangahake epithermal gold-silver deposit defined the local evolutionary sequence in the once active geothermal system.   Some implications for mining of epithermal deposits arise as a result.

Jan 1, 1984

By Dr. O’Neil Thomas J., Donald W. Gentry

There are mines that make us happy, There are mines that make us blue, There are mines that steal away the tear-drops As the sunbeams steal away the dew. There are mines that have lost the ore chute faulted, When the ore's forever lost to view, But the mines that fill my heart with sunshine, Are the mines that I sold to you. -Anonymous INTRODUCTION The preceding chapters have discussed, in various degrees of detail, the primary considerations necessary to perform a cash flow analysis of a mining-related investment opportunity. Although the previous discussions regarding the manipulations, calculations, and interrelationships of the various components of the pro forma income statement were illustrated in the text, many individuals are un- familiar with the format and appearance of a final spread sheet for the evaluation of a mining property. As a result, it seems appropriate to conclude this book with an abbreviated case study of an actual mine property (currently in production) showing the cash flow analysis and some back-up data. Obviously all of the supporting data and calculations for the case study presented cannot be provided; however, reference is made to the major assumptions utilized and to the appropriate procedures employed in the calculations, as described elsewhere in the text. The problem associated with using any case study for illustrative purposes is that one tends to be overwhelmed by detail. For instance, specific costs, prices, expenditure timings, and other variable values may be challenged because they either do not conform to one's expectations or are not consistent with specific operating experiences. When this occurs the instructional value of the problem becomes obscured. The purpose of most case studies, and particularly the one presented in this chapter, is to expose the student to the methodology, procedure, and format associated with performing a cash flow analysis of a mining property. It is not to laboriously wade through the specific details associated with operating and capital cost development, mine plans, or equipment schedules. It should be noted, how- ever, that the values represented in this case study result from specific mine plans, operating procedures, equipment spreads, manpower requirements, and other en-

Jan 1, 1984