Search Documents

There is a Chinese saying-may you live in interesting times. Certainly we do tod.a~our mining professions. We are, of course, totally dependent on a' healthy mining industry for the chance to practice our chosen professions, and for our Institute.Let us look at one of the more interesting facts. The mining industry now accounts for some 50 per cent of Australia's exports.This massive earning of foreign exchange is the key to keeping our increasing overseas debt in check. Furthermore, mineral production..including petroleum, saves us a large amount of foreign currency by providing essential minerals, including energy minerals, for local consumption.With such fundamental inputs to our economy, any primary school student, any child in fact, should be able to see that the mining industry and mining professions are very important to our nation. Yet the average citizen is unaware of this simple fact as they enjoy their high standard'of living and think that we are still living in the lucky country.Therefore, it is most interesting to me that the average citizen, and most of our politicians, seem to hold mining and miners in low esteem. I use the term miners to describe all those important people, like us, who work in the mining professions, and are employed by, or are dependent on, the mining industry.So why are we miners in this paradoxical situation of doing wonderful works, being the backbone of the country, and yet being held in low regard by the very community we underwrite.Truly-it is interesting-or did the Chinese mean intriguing?It is indeed paradoxical that we are the rare people who open up the land, borrow small parts of it for a relatively short time to harvest the mineral crops, then return it to the community for other uses; and when we return the land back to the community at large it should be in better shape than when we started. There will be infrastructure - roads, airstrips, supplies of water and power, parks and housing-all left behind after mining.These benefits to the community are ignored while our critics focus on the small scars on the landscape which sometimes cannot be healed at reasonable cost; and yet, if we allow time, nature usually heals the small scars anyway. Look at New Zealand, particularly the Coromandel Peninsula which was intensively mined and logged; now it is covered with secondary growth and stark pine plantations. Remember that mining scars are infinitesimally small when compared to urban sprawl or clearing of land for farming and grazing, or highways, or the area of most national parks.Thus, miners are important citizens economically, and we are the majority of the few who actually practice the principles of multiple land use.What are the consequences of our image? They are serious in that the poor image we seem to project, discourages many people from becoming involved in, or supportive of, our industry. This brings me to my theme for the year: Students, Education and Communication - the Key to our Future.

Jan 1, 1987

By Clark Harrison

It is not uncommon for overall quality of coal from a mine to deteriorate as the mine is developed or for an improved-quality coal specification to be imposed during the life of the mine. Either of these conditions typically results in management pressuring mine personnel to take greater care in delineating the seam from top and bottom rock. When mining and seam conditions require a portion of the seam to be removed to ensure sufficient rock is removed to meet the quality specification, physical-coal cleaning may become economically competitive with in-pit seam grooming. The additional cost of coal cleaning may, in some cases, be justified by permitting higher recovery of the coal seam than is possible when cleaning the seam with excavators in the pit. This paper compares projected coal cleaning results with present in-pit grooming techniques and reports the economic results.

Jan 1, 1987

By Deno M. Pappas

The purpose of this Bureau of Mines study of U.S. roof and rib (roof- rib) accident statistics and related accident costs is to define current accident trends (1980-84) associated with fatal and nonfatal roof-rib fall accidents. Data were retrieved from a data base containing all recorded U.S. mining accidents, then sorted and normalized utilizing a computer software program. The statistics indicate that roof-rib accidents have significantly declined in the 5-yr study period. Moreover, they indicate that there have been increases and/or patterns of roof-rib accidents associated with specific mine characteristics, such as seam height, mine size, geographic location, and seasonal variations. Also, roof-rib injury characteristics produced pattern changes involving worker activity, lost workdays, types of injury, and severity of injury. A conservative estimate indicates that there has been a 30% adjusted increase in the cost of a roof-rib accident over the 5-yr study period.

Jan 1, 1987

The accurate estimation of ore reserves is the most crucial element in a financier's assessment of the risks associated with funding a mining project. It is crucial because any deficiencies in the estimation of a company's ore reserves will be later reflected in the cash flows derived from the production and sale of the commodity. Bankers must rely on the advice of members of your institute in assessing the quality and quantity of reserves. This information helps determine the cash flows which bankers use in their credit making decisions. It is against this background that this exposition has been prepared on "what bankers require in ore reserve statements" or put another way, "what does a bank require in ore reserve statements in order for it to provide the necessary credit Approvals".

Jan 1, 1987

Geosynclines have been well studied for many years, but very little has been written about the concepts of sedimentary basins in spite of the vast amount of data available. They have been regarded, perhaps, as well- understood intuitively, and therefore not worthy of study. Many of the fundamental concepts of geology were developed during the 19th Century with the construction of coal mines, canals and railways. It was a happy chance that led railway engineers in the early days to think that trains could not climb any but the smallest gradient, so, in Britain at -least, numerous railway cuttings and tunnels were made. These exposed to view and study, in a better form than Nature usually provides, a great deal of interesting geology. Because of the lack of literature about the concepts of sedimentary basins, it is not possible to be sure what the early geologists thought. It seems that sedimentary basins were regarded as recording a history of subsidence during the early stages, when a transgressive sequence accumulated; and a history of uplift during the later stages, when a regressive sequence accumulated. It seemed axiomatic that the age of folding and faulting was younger than the rocks folded or Faulted.

Jan 1, 1987

By C. D. Elifrits, N. B. Aughenbaugh

Introduction Federal and state laws enacted to regulate coal mining and the accompanying public concern about the adverse effects that mining might have on land use have focused much attention on the subsidence of the land surfaces over underground mines. Some questions asked are • Will abandoned mines subside in the future even though they have exhibited no surface adjustment to date? If so, when will subsidence take place? • Can a specific surface area be affected by subsi¬dence more than once? • What surface form will the subsidence feature take? • Is there any way to predict when subsidence will occur and end? An attempt is made here to address these questions insofar as it is possible with available data and experience of evaluation of subcritical extraction conditions. Mining that results in subsidence features can be classified as supercritical, subcritical, and critical with respect to the minimum span lengths of the worked-out rooms (Fig. 1). A complete basin will not develop fully immediately over subcritical conditions because the span lengths of the entries are less than the critical dimension (Wardell, 1983). Passageways, entries, and room-and-pillar panels are all included in the subcritical category. Because of the short span lengths, subcritical mining conditions tend to be stable over the life of the mine unless adverse geologic conditions exist (Gray et al., 1974; Dunrud, 1976). Various roof control and support procedures are employed to maintain entry stability during mining. Little information exists concerning the time factor of subsidence over areas of subcritical extraction. Data that have been collected relate to longwall mines, whereby the cavity sizes are designed large enough to induce caving behind the working faces so that complete subsidence at the surface occurs within a short period of time. The UK's National Coal Board (1975) has reduced the enormous amount of data it has collected to empirical correlations and has published these correlations in its Subsidence Engineers Handbook. The handbook states that "None of the foregoing remarks applies to pillar and stall working," with respect to the section discussing the time factor of subsidence caused by longwall mining (National Coal Board, 1975, p. 40). To understand and evaluate how time relates to subsidence above room-and-pillar mines, one must first recognize how mine cavities deteriorate and fail. The propagation of failure to the surface must then be studied, and, finally, the failures that are manifest at the surface in the form of depressions accompanied by both compressional and tensional movements must be investigated. Failure of mine cavities Any cavity beneath the earth's surface represents a condition of nonequilibrium and tends to close with time. Failure of cavities in a subcritical mine can be classified as failure of the roof, failure of the floor, failure of the supports (pillars, cribs), and elastic rebound of the rock. One mode of failure may dominate, but generally combinations of the four will occur. Also, initial instability of geologic materials and structural features and in situ stress may be unknown factors that can contribute to cavity failure. Roof failure is the most obvious opening stability problem in most operating mines. The bridging capabilities of the roof rock are dependent on the rock's material strength, geologic discontinuities, and reaction to humidity changes in the air of the mine. This type of failure may vary in magnitude from gradual flaking to massive roof falls. Mine floor instability can be manifest in the form of a general heave over a broad area or of individual pillar punching. The weaker and thicker the immediate floor material, the more prone a mine is to experience floor problems. Water seeping into an area can soften the underclay, reduce its bearing capacity, and precipitate failure of support for the overburden.

Jan 1, 1987

By Hedley TP

Success for underground coal mine operators in the 1990's and beyond will be dependent upon better understanding of the dynamics of their operating environment, and extension of emerging technologies to reach new levels of output and productivity. The Collieries Division of B.H.P. Steel International Group clearly identifies with the concept of business/product life cycles - and the need to adopt strategies that can drive the business successfully into the future. Three main thrusts within BHP Collieries Division relate to: 1) Detailed assessment of current mines to determine: a) The real output potential of the current facilities. b) What factors now inhibit the full potential from being realised. c) Opportunities that exist to enhance overall mine performance. 2) Based upon the findings of these studies, putting into place cost effective strategies and systems for the ongoing "tuning" of the mine. 3) of new/improved technology primarily in areas of: a) Coal cutting and underground coal clearance. b) Controlling the overall mine gas Regime.

Jan 1, 1987

By David A. Zegeer

Since 1980, more than 40 miners have lost their lives by being trapped and suffocating in stock-piles, bins, silos, and similar facilities. Mine Safety and Health Administration (MSHA) is concerned about these accidents, most of which could be prevented if management and miners appreciated the hazard. In February 1986, the coal industry had a suffocation accident that drew national attention. A group of engineers were standing on a coal stockpile. It gave way under their feet. Five of the engineers were buried in the coal and suffocated. As with all fatal accidents, MSHA investigated the cause of this tragedy. I also asked my staff to look into the history of similar accidents. I found out it is rare to have multiple fatalities due to suffocation in material. But, over the years, there has been a long series of individual fatalities from this type of accident. Here are some examples. In Oct. 1985, a coal mine employee in Virginia entered a hopper to collect a coal sample. The feeders were started while he was standing in the hopper. He sank into the coal and suffocated. In Sept. 1985, an employee at a Texas sand company climbed onto a surge pile, to check a problem with sand flow. When other employees found him, the sand had swallowed him. Only his face and one hand were showing. Though the victim's face was clear of the sand, he suffocated before rescuers could free him. Many people do not realize you can suffocate in this kind of situation, though your head is free. Every time you exhale, the material has room to shift and press harder against your chest. Then you have less room to inhale. If this goes on long enough, it gets to the point where you cannot inhale at all. That is what happened to the victim in this accident. In May 1985, a plant operator at a Wisconsin sand and gravel operation purposely slid into the drawhole of a surge pile. He tried to break up large rocks that were clogging the drawpoint. Material piled on the side of the surge pile slid down and buried him. The operator was wearing a safety belt and line. But he was covered by 3 to 3.7 m (10 to 12 ft) of material and could not be pulled free. This incident illustrates another point. A safety line can help. But it is not enough. Workers should never put themselves in a position where loose material can fall on them from above. In Jan. 1985, a young Utah coal miner was waiting for a ride home from a co-worker whose job was at the tipple. A jam developed in the coal bin. The men could not clear the jam from the outside. So the young miner jumped into the bin. He started digging with a shovel at the toe of the coal pile. It caved in on him and he suffocated. The young miner had only three months of mining experience. He had not been trained for work around the coal bin. Since 1980, 16 coal miners and 26 nonmetal miners have lost their lives in loose-material suffocation accidents. Suffocation accidents occur in many areas around mines - bins, hoppers, stockpiles, surge piles, and silos, among others. One recent accident occurred at a surface coal mine in Illinois. The victim was walking over an area that had been drilled and blasted the week before. He fell into a void that had been crusted over with earth. He too suffocated. And many materials have been involved in suffocation accidentscoal, crushed stone, sand, salt, different kinds of ore, ammonium nitrate pellets used in blasting, and a powdery byproduct of iron ore milling called calcine. In addition to fatal accidents, there are near misses. We do not know how many. Most of them are not reported. A person who gets trapped in material, but is rescued, is usually unhurt. MSHA sometimes hears about these accidents by chance, or because they are reported in the local media. We do know that near misses are happening far more often

Jan 1, 1987

By A. Montini

The problems encountered in the design of control systems for milling cir- cuits when the model of the system and the model parameters are uncertain are discussed. Considering these uncertainty factors has led to the development of a technique that gives a quantitative assessment of real system stability, reveals the trade-offs between performance and stability and helps the designer in deciding what level of model complexity to use in the controller design. Furthermore, it allows for on- or off-line optimization of the milling circuit performance as it provides the base for the design of a controller which is stable over the plant operating range.

Jan 1, 1987

By A. Sainato, S. J. Kravits, G. L. Finfinger

This report describes a project conducted by the Bureau of Mines in which the accurate directional drilling of a borehole was demonstrated with the objective of intercepting a designated target. The project was conducted at Navajo Dam in northern New Mexico at the request of the Bureau of Reclamation. Borehole survey and drill logs are provided in an appendix. The trajectory of the demonstration borehole was designed to intercept a 5-ft-radius target at the final or "punchout" distance of 885 ft. The elevation of the borehole at this distance was within the target; the borehole punchout coordinates were 8.81 ft southwest of the target. As a result of the demonstrated accuracy, the Bureau of Reclamation has contracted the accurate drilling of boreholes as long as 600 ft from the inside of a short tunnel, to control water seepage in the right abut- ment. This resulted in a substantial cost savings compared to the orig- inal plan of constructing a longer tunnel and drilling 150-ft boreholes.

Jan 1, 1987

This paper briefly discusses the negotia- tion of the more important provisions in agree- ments for exploration and mining rights with Pacific countries. LAND RIGHTS Land rights are complicated and sometimes controversial in many of the Pacific countries. In some countries, a company will have to deal with land owners directly; in others, the government will act as intermediary. Inevit- ably, a company will have to deal with both. Mining companies need to be sensitive to the culture and particular interests of the land owners and of their history in defending their rights. The issues are too complicated to be dealt with here. Some mining companies have spent, and will continue to spend, considerable time trying to understand them. It will " require patience, perseverance, sensitivity and unflagging optimism. The better advised companies will ensure that their local repre- sentatives get to know the land owners, under- stand their concerns, and will pursue a policy of keeping them informed on a regular basis of all of the company's activities and proposed activities. Good community relations are the keystone for good mining operations in the Pacific. Most countries will require the submission of an environmental impact statement so that they will know in advance what effects a pro- posted mining operation are expected to have on the environment and how it is intended to deal with them. They will also want to approve the company's environmental reclamation and rehabilitation plan. Let's face facts right away - mining, by its very nature, is not going to improve the environment. There will be waste discharges, emissions and deposits. They will affect the land, air and water and hence human, marine and animal life and vegetation. There will be sounds and odours and the esthetics of mining operations, though perhaps pleasing to geolo- gists and mining engineers, will not please Others.

Jan 1, 1987

By S. P. Singh

Destress blasting is commonly used in the mines to minimize the occurrence of rockbursts. The fracturing created by destressing in the vicinity of the face reduces the stress concentration by pushing the zone of high stress deeper into the rock mass. But the destressing practice by blasting may be devastating near the faults or other sensitive high stress zones. To avoid severe rockbursts in such situations, the application of chemical destressing has been proposed in this paper. A laboratory investigation was conducted on the rocks in the Sudbury basin to examine the change in the material properties with an aim of assessing the feasibility of destressing by chemical means. The favourable change observed in the rock properties led to the suggestion that the injection of surfactants in boreholes would enhance fracture propagation similar to what is currently done by blasting but in a safer, inexpensive and non-violent manner. The current destressing practices in Ontario mines have also been reviewed in this paper.

Jan 1, 1987

By A. Mcdonald

"An X-Met Analyzer was purchased from Outokumpu in late 1983for use in the Hudson Bay Mining and Smelting smelter. Its first use was in the fuming plant to give zinc assays of each charge of slag tapped from the fuming furnaces. This quickly told the operators exactly when each charge had reached its economic tap-out point, and gave supervision a fool-proof method of identifying good operation. These and other factors led to major improvements in coal utilization in the fumers and to major increases in zinc oxide production. A second unit was later purchased for the reverberatory furnace to give silica and iron assays of the slag, and these were used to make adjustments in the feed composition to maintain the desired SiO2:Fe ratio in the slag. Since purchasing the units for the furnace, the oil consumption and copper content of the slag have dropped significantly. IntroductionSmelters have lagged far behind concentrators in process control by mean s of rapid product analysis. The on-stream X-ray analyzer was developed about seventeen years ago, and soon concentrators around the world were getting assays of the incoming ore, .concentrates and tailings every fifteen minutes, and using these to control reagent additions and other process variables. Almost always, the concentrate grade and recovery improved.In smelters, product streams are solids or molten materials, not the more easily handled slurries, and until seven years ago no inexpensive equipment was available to provide rapid analysis of this type of material. In approximately 1980, several companies developed instruments based on irradiating solid samples with low-intensity gamma rays from radio-isotope sources, and measuring the secondary X-rays emitted from different elements in the sample to provide an analysis of the elements desired.The smelter staff had a close look at what was needed and listed the following points as being critical:1. ability to provide Zn assays of a sample of slag within 15 minutes of taking it, in order to achieve optimum fuming times (zinc fuming , being a batch process, had the greatest potential benefit from rapid slag analysis);2. ability to give Cu and Fe assays on the slag, and on other smelter products, such as matte and converter slag;3. ability to give Si02 assays since the SiO2 content of the slag has a strong effect on fuming rate; and4. ability to stand up to an industrial atmosphere such as exists in the fuming plant."

Jan 1, 1987

By J. A. Farinelli

In the Appalachian region of the United States, approximately 40% of the underground coal reserve base exists in seams 0.7 - 1.1m thick. These seams are, in general, often of premium quality and are frequently accessible through above-drainage drift-type openings. Unfortunately, there are no apparent advantages to mining thin seams, if quality is disregarded. The thin-seam mine is faced with the same legal and economic pressures as any other underground coal mine. But in addition to these common problems, thin-seam operations must also deal with the unique problems associated with mining at such a restrictive height. Small-scale, short-lived operations appear to be the most feasible means of mining these reserves. The purpose of this paper is to evaluate the production and safety potential of various thin-seam mining systems. Recommendations will be made regarding present and future thin-seam operations.

Jan 1, 1987

By S. J. Haynes

"This paper documents the characteristics of the different quartz veins, and their relation to gold, in the turbiditic Meguma domain of eastern Nova Scotia. Eleven different types have been distinguished in the greenschist facies on the basis of form, internal structure, mineralogy, wallrock alteration and crosscutting relationships to each other and to regional structures. Gold is present as rare visible disseminations in host rock slates and in ore-grade, early-formed veins, that pre-date the formation of upright Acadian folds and intrusions of Devonian granitoids. Four vein types pre-date Acadian folding. Five gold-deficient vein types are associated with Acadian folding (syndeformation); whereas two gold-deficient vein types clearly post-date this deformational event: Previously unreported, wall rock alteration is associated with early crosscutting and semiconcordant auriferous veins. In contrast, early stratiform veins are devoid of wallrock alteration. It is suggested that the auriferous vein arrays formed as submarine exhalitive systems over synsedimentary tensional faults and that the Meguma domain may represent the opening of a basin similar to the modernGuaymas rift .IntroductionThe term ""turbidite-hosted gold deposits"" is introduced to distinguish gold deposits contained within a turbiditic sequence of wackes and shales (or their metamorphosed equivalents) from gold deposits in other types of sediments. Usage and justification for the term is similar to ""carbonate-hosted lead-zinc deposits"" or ""volcanogenic massive sulphides"". A range of different characteristics can be present in individual deposits, some of which may be indicative of specific deposit types in the same manner that volcanogenic massive sulphides can be subdivided into ""Cyprus type"", ""Kuroko type"", ""Besshi type"", etc. Historically, gold deposits hosted by turbiditic flysch were an important class of quartz-vein gold mines in the 19th century. They included the goldfields of Victoria, Australia, Otago, New Zealand and Nova Scotia, Canada. Production from most of these fields had ceased by World War II and interest in this type of deposit waned. However, the recent exploration interest in gold has resulted in both re-assessment of the classical mining camps and the discovery that ""turbidite-hosted"" gold deposits are present in many parts of the world.Mapping of the regional geology and gold deposits of the Megumadomain of Nova Scotia was carried out by E.R. Faribault of the Geological Survey of Canada between 1886 and 1939. Faribault produced a comprehensive series of maps and reports for each gold district, a compendium of which was published by Malcolm (1929)."

Jan 1, 1987

By Mark A. Koestel

Cobalt-sulfide mineralization can he found in potentially economic quantities where permeable, basal Cambrian formations "pinchout" against Precambrian pal eotopographi c highs. These environments are common around the Saint Francois Mountains of southeastern Missouri and they share many similarities with the geologic environments of Zambia and Zaire in South Africa. Exploration for this type of deposit involves test drilling targets identified by trend analysis from past drilling, geophysics, geochemistry and a comprehensisve study of regional geology and isopach maps. Innovative ideas, new exploration concepts and insoluble residue geochemical methods may provide the necessary "edge" needed to complement basic geologic understanding leading to ore discovery.

Jan 1, 1987

of the multitude of physiographic problems of immediate interest in volcanic terranes, it is the origin of the magma forming the magnificent volcanoes that is perhaps the most mysterious. Unlike anywhere else on earth, the possible locations of magma production beneath the convergent margins are strongly limited in depth and areal extent. Yet the exact process by which magma is produced still stands elusive, even in light of tremendous gains in analytical and physical insight. The principal aim here is to discuss some of what has been revealed about the physics and chemistry of the origin and evolution of island are magmas.

Jan 1, 1987

By E. M. Spokes

Starting in 1980, a committee of the National Research Council studied the question of why some underground coal mines are safer than others and what could be done to improve the ones with poorer performance. The results indicated that safety is improved by management commitment to safety, by cooperation between labor and management on safety matters, and by quality training of employees and managers. Younger miners have higher accident frequencies, but are less likely to be killed or permanently disabled by a lost-time accident. Methods for improving safety performance are proposed.

Jan 1, 1987

By G. Lucas

"Material substitution occurs continuously in response to competitive and economic pressures. Technical development can accelerate or slow substitution by improving the performance of the invading or defending material. The choices are seldom simple and have to be made in the context of continuous commercial change.The development and commercialization of a new aluminum material is examined. The material has been introduced into· several different markets, so it is possible to compare and contrast the degree of success obtained in each.IntroductionAluminum-based materials have been in use for over one hundred years and , therefore, the development of a new family of alloys is rare. In the early 1970s, Dr. L.R. Morris and his coworkers at Alcan' s Kingston Research Centre started work on what was, at the time, something of a scientific curiosity-a family of alloys strengthened by an unusual mechanism.This paper deals with the development and commercialization of what became known as the Alcan 255 alloys"". These alloys have found uses in several markets, usually as improved substitutes for existing materials. Forecasting the usefulness of a substitute material in an existing marketplace is difficult, in part, because even material users are seldom able to specify precisely their requirements. This uncertainty can cause the failure of some substitutions but can also lead to opportunities which were not initially obvious.Technical BackgroundPure aluminum is a soft, weak material. It can be strengthened by the addition of various alloying elements and by work hardening. Alloying elements usually act by forming solid solutions which are stronger than the pure metal or by precipitating during heat treating or aging and so preventing the easy movement of dislocations during deformation. Elements which can perform either role had been investigated for decades and were thought to offer little chance of technical breakthrough in 1970. An outgrowth of the then new and exciting research on directional solidification seemed, however, to offer such promise.Some aluminum-iran-manganese alloys will solidify under certain conditions as 'coupled growth' eutectics (Figs. I and 2). The microstructure shows one phase growing as long rods through the other. This is an uncommon structure and it was investigated to see if it had equally unusual properties. On deformation by rolling the rods were broken up into small equiaxed , evenly-spaced particles (Fig. 3). Materials with this structure were found to be stronger than other alloys with similar amounts of alloying addition, and to resist thermal softening remarkably well. This combination of properties was thought initially to be due directly to the particles by a dispersion strengthening mechanism, but later this was found not to be strictly true."

Jan 1, 1987

My forebears migrated to South Australia in the 1830s, 1840s and 1850s. All of them were literate but, because they moved about South Australia looking for work, family papers have become scat- tered and I am left with a few fragments. Some years ago I was intrigued to find among my fath- er's books a frontispiece in an old Anglican Book of Lessons. As can be seen Joseph, a mining smith, was also a Freemason. Thus my interest was aroused. I know some- thing of modern day mining communities in South Australia and wondered what they were like 100 or more years ago.

Jan 1, 1987