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By H. N. Maleki

Tension-torque relationships were investigated *n a coal mine for bath standard 5/8 in. (16 mm) bolts and a vibrating wire instrumented bolt, using conventional and controlled installation techniques. The instrumented bolts differed from the standard bolts by their head size and hole preparation procedures. The controlled installation technique developed by the U. S. Bureau of Nines (USBN) involved using hardened washers and lubrication in the bolt assembly, and maintaining a minimum thrust level during bolt installations. The object of this study was to determine the tension to torque ratio (lb/ft-lbs; for standard bolts and instrumented bolts for both conventional and controlled installation techniques, and to modify the bolt assembly so that the ratios would be equal for the instrumented and standard bolts for both installation techniques. It was shown that the instrumented bolts installed in faced holes had a similar tension torque ratio td that of standard 5/8 in. (16 mm) bolts installed in unfaced holes for each installation technique, and thus they were representative of other uninstrumentea bolts. This was achieved by evaluating the influence of several factors oh the relationship, including: facing the hale surface, introducing washers and lubrication in the bolt assembly, and applying different levels of thrust at installation due to bolter operator practice. The tension to torque ratio fur conventional bolts was only 21 (lb/ft-lb) for the coal mine, resulting in an installation tension of 4000 lbs (17.8 kg) with the typical installation torque of 150 to 400 ft-lb. This tension level was approximately 50 percent of the required bolt tension, and thus, it was concluded that torque standards are not sufficient to assure adequate bolt tension. .he low tension levels were due to the particular wait hardware in use, operator practice, and bolt fencing.

Jan 1, 1984

By N. T. Halgreen

The use of coal for combustion, carbonization, and the production of synthetic fuel is discussed briefly, highlighting the effect of certain physical and chemical properties of coal on these processes. The effect of consumer specifications of properties such as calorific value, ash content, moisture content, and size consist on the planning and operation of a mine are discussed, including the influence of coal degradation through time or mechanical means. The effects of various mining methods on these parameters and on the utilization of coal reserves are discussed.

Jan 1, 1984

By Neil Styler

This paper presents an analysis of measurements of inter-burden de- formations above six longwall faces. An attempt is made to demonstrate some correlation between the movements at the various sites, and to examine their importance with respect to predicting caving height, disruption of overlying seams, and disruption of aquifers. This analysis demonstrates some significant differences between predicted surface subsidence, and inter-burden deformation. In addition it is shown that the caving height above a longwall face is equal to 8 to 12 times the extraction height, with a zone of fractured rock ex- tending to approximately 50 times the extraction height above the seam.

Jan 1, 1984

By R DeLon Hunsaker

In the past, quarrying and other small operations have not been able to take advantage of the lower cost, convenience and better performance of bulk slurries. However, with the introduction of repumpable emulsion slurries and their ability to be stored in containers as blasting agents, bulk slurries are now available for small operations with small diameter boreholes and are producing excellent results. This same concept is being used successfully in larger underground operations.

Jan 1, 1984

The selection of the best comminution circuit for the preparation of concentration feed is a compromise based on economics, energy efficiency, labour costs, steel consumption, availability and other factors specific to each case. It is postulated that the selection must be a choice of one of the eight basic comminution circuits which can be divided into two basic groups, (1) autogenous or semi-autogenous primary mills with or without a secondary grinding stage and (2) fine crushing usually in cone crushers followed by a rod mill-ball mill circuit or a single stage ball mill circuit. The accuracy of selection may be improved by pilot plant and laboratory tests which are described in this paper. For (1) above, testing includes media competency tests with standard impact crushing, grindability and abrasion tests followed by pilot plant tests. For (2) above, bench scale crushability, grindability and abrasion testing is available. It is suggested that, through these tests, it should be possible to eliminate all but one in each group of basic comminution circuits. Then engineering and economic studies should lead to the best comminution circuit for the specific requirement.

Jan 1, 1984

By Mark A. White

Arch Mineral has developed several computer programs that aid the surface mine planning function. These programs are utilized to perform long term projections for various area or semi-area stripping operations. The program generated reports include yardage, tonnage, quality and ratio information for the user-specified time periods. The projections are used to anticipate the annual budget, to compare alternative mine plans and to analyze acquisition candidates. The programs are user friendly, fast and accurate. Geological Grid File Two data files must be set-up and used in conjunction with the mine planning programs. These are a geological data file and a general input file.

Jan 1, 1984

By P. J. D. Lloyd

This fascinating paper deserves study by all who are interested in the economics of gold production. The argument in the paper that price is determined by the balance between supply and demand may be thought to be obvious. However, correlation analysis presumes causality, and there is some evidence in the paper to suggest that causality is absent in this market.

Jan 1, 1984

By Neil D. Donnell, O&apos

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1984

By James E. Lawver

During the past century, the Florida Phosphate Industry has established an enviable record of innovative technology in nearly all aspects of mining and beneficiation. A notable exception is the lack of technology to improve the present practice of storing waste clay in earthen dams. The rule which has been adopted by the Department of Natural Resources states, "Since storage of clay wastes for long periods of time interferes with expeditious reclamation and since above grade storage of clays takes otherwise useful land out of production and raises potential health and safety problems, below grade storage and rapid reclamation techniques are encouraged." The two waste products from the beneficiation plant are clay slimes (-0.1 mm in size) and sand tailings. The sand tailings do not present a problem since the tailings rapidly dewater to a dry weight of about 100 pounds/ft3 and make good land fill. By contrast, disposal of waste clay slimes is a formidable task. The basic problem is simply that the waste clay not only dewaters very slowly, but also that the ultimate solids content is very low and in most cases the volume of the clay greatly exceeds the available volume of below ground storage of the mined land.

Jan 1, 1984

This paper will discuss Fordertechnik dawatering screens and their application in process industries. Fordertechnik screens were designed for the dewatering of deslimed, wet fines materials encountered in the mineral beneficiation, sand and coal processing industries. However, these screens have also been used in such industries as municipal waste treatment, paper pulp, chemicals and the food industries. Fordertechnik screens are of simple design and, as a result, offer low capital and maintenance costs. The design is based on the use of twin counter-rotating vibratory motors which provide high frequency, low amplitude linear movement of the screen deck which is essential for high production requirements. Fordertechnik dewatering screens are engineered and manufactured in Australia by Mitchell Cotts Engineering under licence to Fordertechnik GmbH of Mulheim, West Germany

Jan 1, 1984

By Ronald R. Rollins

A continuous propagation velocity measurement probe has been utilized to determine velocities of slurry explosives, whole prills, crushed prills, aluminized crushed prills, in bulk and plastic screw tubes.

Jan 1, 1984

By Terrence J. Stobbe

On the job injuries to the musculoskeletal system are probably the oldest of the industrial safety problems. Long before we had pinchpoints to guard, chemical vapors to ventilate, and noise to enclose, people were getting strains, sprains, and sore backs from their work activities. In spite of the age of the problem, it remains a long way from being solved. The past ten years have seen a significant commitment by the sci¬entific community to understanding the problem. Engineers, scientists, doctors, and epidemi¬ologists have been involved, and as a result, today we have a much better understanding of the problem. The first step in understanding a problem such as this is to explore its history and epidemiology. The research done by Chaffin (1977), Snook (1970), Ayoub (1978), the ILO (1962), and others, led NIOSH to publish its Work Practices Guide for Manual Lifting in 1981. The guide was based on research carried out in general industry, but subsequent research by Stobbe (1983) and Peters (1983) has suggested that the nature of the problems producing injuries in underground mining is the same as in general industry. The problems are more intense in the mining environment.

Jan 1, 1984

By Peter Jackson

Over a quarter of a century ago a New Zealand physicist suggested the possibility of detecting coal seam discontinuities by a seismic method carried out underground in the mine workings (Evison 1955). Twenty years ago initial experiments were performed in Germany (Krey 1963). Since then research has continued, notably in Britain and Germany, in order to provide a reliable fault and washout detection system. The National Coal Board of Great Britain has now carried out more than 250 surveys in Britain, France and Australia. The first NCB survey in the U.S., a successful application of the technique to an Ohio coal seam, will be described and the strengths and limitations of the method explained.

Jan 1, 1984

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

"Who is the man who views the mines and promptly turns them down? Who is the one that thinks this is the short cut to renown? Who is it gives the bum advice to the innocent financier? The knowledge-feigning, theory- straining mining engineer." -Anonymous INTRODUCTION Taxes levied against mining properties and operations are a critical cost in the economic evaluation of mining investments. Indeed, taxes represent a substantial cost of doing business in the minerals industry and often have a significant impact on corporate investment decisions. A good example was the postponement of mineral development in the state of Wisconsin, primarily because of what was perceived to be excessive taxes imposed by that state. In many respects mining investments are no different from other industrial investments. Astute taxing authorities should recognize that geologic endowment is a necessary but clearly not a sufficient condition for mineral investments. The fact that a mineral deposit exists does not necessarily mean that it will ultimately be developed-a point that many taxing authorities fail to recognize. While it is true that ore deposits are not mobile in the sense that they cannot be physically moved to a district having more favorable taxes, corporate investment capital certainly is mobile and flows to ventures which maximize wealth to the firm. In short, higher taxes reduce project yields and tend to drive investment capital elsewhere. The appropriate type and level of taxation imposed upon the mining industry continues to be a very controversial and emotion-charged topic. Mining activities have been taxed at various levels over the years due to widely differing taxation philosophies. Location has also influenced taxation policies, as evidenced by the diversity of tax laws and assessment procedures applied to mineral deposits by the various states. Indeed, mineral taxation varies from state to state, from county to county, and from one mineral commodity to another. Whether or not a given tax is appropriate for a specific mineral deposit, or even an industry, is a difficult problem to assess. First, the type or kind of tax which should be imposed must be considered. Second, it is most important to define a fair and unambiguous base against which to levy the tax. Finally, one must consider the tax rate to be applied to this base. It is the combination of these two components

Jan 1, 1984

The HYC mineral deposit at McArthur River is about 1.5 kilometres long by 1.0 kilometres wide and 55 metres thick, and contains 227 000 000 tonnes of ore of average grade 9.2% Zn, 4.1% Pb and 41 g/t Ag. Major studies have been carried out continuously since 1955 over the deposit and in the general region. This work is continuing. A small underground mine was developed by driving a decline tunnel to intersect the mineralization 80m below the surface. This provided a fully representative sample of the total deposit unaffected by weathering or oxidation, and was available for the major test program carried out in a pilot plant built to determine the full metallurgical charac- teristics of the ore. The pilot plant operations followed investigations by research institutions, both in Australia and overseas, into the problems of this ultra-fine grained ore. The ultra-fine grained nature of the ore required grinding to an average size of 95% passing 37 micro metres or 400 Tyler mesh. A major feasibility and environmental report was submitted to the government covering all aspects of a development program. The geological, engineering, metal- lurgical, economic, cultural and environmental submissions contained in this report were studied by external consult- ants employed by the government, who agreed with the conclusions that the McArthur HYC deposit is at present Uneconomic.

Jan 1, 1984

By George D. Lessner

I'm sure that everyone at this meeting is aware of the current problems facing the U.S. metals mining industry. Prices are depressed and expected to remain depressed for quite some time. On the other hand, industrial minerals, including talc, are doing quite well. The profitability of industrial minerals has sparked considerable interest on the part of many companies in expanding into industrial minerals. Our company is one of those actively seeking to expand its position in industrial minerals. It is appropriate that the A.I.M.E. asked me to speak to you regarding entry into the talc business. So how do you get into the talc business? Earlier speakers have explained how to locate, mine, process, and market talc, so you have the "how ton.

Jan 1, 1984

By Guang Ping Cui

In this paper the imminent relationship between rock burst and its phenomenon with normal rock pressure and its appearance, as well as the factors of one changing into another have been analyzed. Based on this, the necessary and sufficient appearing factors of rock bursts have been put forward, and the term "burst pressure" has been defined. According to the statistics data of tremendous rock bursts which appear in collieries in Hunan Province, the futures of high frequency, great strength and shallow depth of the beginning burst have been found. There ere some special structures in the coal seams, which are closely related with the burst phenomenon. A hypothesis of "star structure" has been suggested for the appearing mechanism of bursts. Inside and around this star structure the distribution rule of burst pressure and rock strength has been researched depending upon the theory of the limited stress field. A new description of the appearing causes of bursts has been raised.

Jan 1, 1984

Geostatistics originated as an application of a classical statistical concept, multivariate linear regression, to the solution of a practical problem, estimation of reserves in the South African gold mines. In this respect, geostatistics should only be considered as one statistical method among many that can be used to evaluate mineral deposits. R.F. Shurtz has studied possible applications of power spectrum analysis to the same problem, and these studies may result in future improvements over the presently accepted geostatistical methodology. The intention of R.F. Shurtz's paper, as stated by the author, is to "relate geostatistical doctrine to classical statistical and mathematical concepts." However, in this comparison the "geostatistical doctrine" appears to include only the simplest among the geostatistical concepts advocated by G. Matheron, while "classical statistical and mathematical concepts" are limited nearly exclusively to power spectrum analysis. The author attempts to compare the two methods, and to prove the theoretical superiority of power spectrum analysis. Unfortunately, a number of errors and incorrect statements are made concerning both the theory and application of geostatistics, which invalidate the comparison and the conclusions drawn from it. The errors made in this comparison are understandable since few scientists can claim to have expertise in two theories as diverse as those compared here. In many respects, this paper is reminiscent of polemics which occurred 15 to 20 years ago when geostatistics and trend surface analysis were compared. Each method has its own merit and limitations, and none can claim absolute superiority. The most misleading statements found in R.F. Shurtz's paper are: The definition of the semivariogram given on page 1923 is incorrect. If the maximum difference between two assays is 1, the maximum value of the semivariogram is not 1, as stated, but 0.5. The comparison of geostatistics and linear regression made in the section entitled "Insufficiency of Classical Statistics?" is not valid. The semivariogram of the sample values given in Table 1 (page 1919) has a parabolic shape indicative of a linear drift. When such a semivariogram is observed, the simplest method of geostatistical estimation (linear kriging with unknown mean) is not applicable. Universal kriging must be used that takes trends into account. On page 1921 it is stated that the use of trends "is officially disparaged in geostatistics." Again on page 1924 mention is made to "Matheron's commitment to random process (intrinsic) models and his present categorical rejection of deterministic (trend) models for mineral deposit evaluation." Indeed, from articles published by geostatisticians in the 1960s one could infer that geostatistical methods are not compatible with the presence of trends. However, even the simplest

Jan 1, 1984

By J. de la Vergne, L. O. Cooper

The hydrostatic steel mine shaft liner (HSL) Provides a permanent wall lining for drilled shafts. It is watertight and suitable for bad ground conditions. After a shaft has been drilled to its full depth, the HSL is lowered into it and secured in place with cement grout. The liner consists of a cylindrical steel shell usually reinforced with exterior stiffening rings. The shell is basically designed for compressive strength and the rings are provided to give the shell added resistance to buckling. There are no published standards for the correct procedures to design an HSL. This paper gives a method that appears logical. A design solution can be complex with increased opportunity for error. This paper presents simple formulas to produce sufficient accuracy for construction design. Two new concepts are presented, referred to as transition pressure and critical pressure. An example demonstrates use of the formulas and concepts presented. To facilitate comprehension and use of the formulas, Greek letters are avoided and most of the English alphabet symbols used refer by association to their definitions. An appendix shows derivation of the formulas.

Jan 1, 1984

By W. J. Locher

One important means of reducing steel consumption in grinding mills is not mentioned in S.G. Malghan's paper. It is simply to reduce the oxygen content in the mill and pulp. While oxygen dissolved in pulp is not readily reduced without additives, reduced aeration and reduced ventilation of grinding mills are often feasible. It is not necessary to completely eliminate the oxygen to achieve substantial benefits, since corrosion rates vary with oxygen content in a manner analogous to combustion rates as oxygen content increases. It is difficult to generate indisputable quantitative data on the relationship of oxygen reduction in a milling system to changes in consumption of grinding steel. Perhaps this accounts for the absence of technical papers on the effects of reducing oxygen content in grinding mills by reducing aeration of pulp and ventilation of grinding mills. One qualitative observation is that mills operating at a lower percent of critical speed will tend to have lower media consumption for similar fineness of grind without necessarily having an equivalent reduction in power consumption per ton of product. Reduced mill speed would also tend to reduce both ventilation of the mill and entrainment of air in the pulp. Larger grinding mills tend to be more media efficient because they operate at a greater ratio of charge volume to pulp surface area, which will tend to reduce the aeration per unit of pulp volume. The mechanical steps required to reduce aeration of grinding mill pulps depend on the configuration of the grinding circuit and related process. Reply by S.G. Malghan Mr. Locher stated that my paper did not mention the reduction of oxygen content of the pulp as a potential method of decreasing the steel consumption. I would like to bring to the attention of Mr. Locher that an indirect reference was made to the fact that pulp oxidation potential controls the corrosion wear of steel. Though dissolved oxygen is one of the factors that controls oxidation potential, additional discussion was deliberately avoided for the reasons mentioned by Mr. Locher. The most important reason being the difficulty of decreasing and controlling the oxygen concentration of the pulp in a commercial mill.

Jan 1, 1984