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By Noreen D

At Bougainville Copper Limited comparison testwork was conducted between "horizontal" cycloning and conventional vertical cycloning. Horizontal cycloning reduces circulating load and allows increased ball mill throughput. Cyclone efficiency is the same or better as a result of the reduction of fines short-circuiting to the underflow. Operationally, horizontal cyclones are less likely to suffer from blocked spigots and high cyclone feed pump sump levels. Cyclone feed pumping power is reduced. High horizontal cyclone underflow density provides the option to optimise grind by manipulating water addition to the ball mill feed.

Jan 1, 1988

By D. B. Ogbenlowo

A major problem facing the Nigerian Mineral Industry today is flooding in its underground mines. Flooding has reduced productivity to a very low level which results in huge economic losses. Consequently, this paper presents a computer based model that pre¬dicts the quantity of water accumulating from diverse sources in an underground coal mine with a view to suggesting a permanent solution to the problem. Specifically, the paper describes the model building technique and the output achieved from its application to a real mine case study.

Jan 1, 1988

The special mixing requirements for backfilling are discussed, and the problems associated with the mixing of coarse and deslimed slurries, as well as the tailings from the gold plant are outlined. The mixing of binders which are used to strengthen backfill and the parameters for the scale-up of mixer pilot plant work are also discussed

Jan 1, 1988

By D. S. Bloswick

An investigation an4 analysis of slip/fall accidents specifically pertaining to underground coal mines was conducted. From a population of 751 accident reports, three major sources of injury which account for over 80% of the incidents have been identified. The specifics of this study are presented in this paper. Based on the results, several recommendations are made to reduce such accidents in underground mines. In addition, a brief discussion of the slip-hazard analysis laboratory at the University of Utah, which will be useful in future analyses of these accidents is presented. Work in this facility includes the simulation of certain mining activities in a controlled setting. Foot forces are measured and work methods subsequently developed to minimize the slip potential of these activities.

Jan 1, 1988

By Wesley L. Bender, James E. Murray

Pre-blast surveys are often conducted solely to document existing structural conditions and uncover potential problem areas. This paper presents a case history where the pre-blast survey was also used as a vehicle to initiate a public relations program with the occupants of a large apartment complex adjacent to a major excavation site. The public relations program, in conjunction with good blasting practices, succeeded in keeping complaints to a minimum. The presentation includes an overview of the project, details of the public relations program, some of the blasting methods that were utilized and a recap of the complaints received.

Jan 1, 1988

By Thomas M. Barczak

This report describes a study that examined load transfer mechanics in longwall shield supports as part of the Bureau of Mines research program to optimize support design and utilization. The objectives of this study were to determine the contribution of the leg cylinders and the caving shield-lemniscate assembly towards full shield vertical and hor-izontal load resistance capability and to determine how the interaction of these members affect overall shield response. Load-displacement characteristics of the leg cylinders and the caving shield-lemniscate assembly, independent of the full shield, were evaluated from controlled displacement tests in the Bureau's mine roof simulator and responses were compared with full shield responses to identify load transfer mechanics. It is concluded from this research that the participation of the caving shield-lemniscate assembly significantly affects the response of the shield support. It is likely that the caving shield-lemniscate assembly is not participating fully in current shield designs because of translational freedom in the numerous pin joints. It is also concluded that the shield will respond differently to different boundary condi-tions resulting from interaction with the strata. This report describes load transfer mechanics of shield supports and the implication of these research findings on shield design and utilization.

Jan 1, 1988

By Deren Zhu

Based on the results of field observation and physical model analyses, a computer simulation method, FEAEBP, has been developed for simulating the breakage of the main roof by considering it as a Kirchhoff plate on Winkler elastic foundation. By this method various parameters of rock property, different boundary conditions of the working face and the initiation, development and results of the breaking process of the main roof with different geometric dimensions can be effectively simulated. Since the main and immediate roofs, and the coal seams are treated as an integrated mechanical system, the interaction among them can be studied in detail.

Jan 1, 1988

By A. R. L. Thoresson, S. J. Lennon, F. P. A. Robinson

This paper reports and discusses experimental work carried out on heavy nickel-electroplated turbine-disc steel. Mechanical and fatigue tests were used to determine whether the coating was suitable for turbine-disc applications. It was concluded that dehydrogenation treatment is necessary in order to produce compatibility of the coating and substrate

Jan 1, 1988

By Gene E. McClelland, Dirk J. A. van Zyl

5.1 INTRODUCTION Heap leach cyanidation techniques possess considerable potential for exploitation of low-grade ores, small ore bodies, mine strip waste and tailing materials where fine grinding is not necessary for good extraction. For heap leaching to be successfu1, ore must exhibit certain characteristics, as previously discussed in Chapter 1. Primary among the necessary ore characteristics is that the ore must have good permeability after being crushed or treated and stacked into heaps if uniform distribution of the cyanide leach solution is to be achieved. Gold and silver ores containing excessive amounts of clays or fines generated by crushing are some of the most difficult to treat successfully by heap leaching. The presence of excessive amounts of slimes (generally classified as minus 50-micron or 270 Tyler mesh sieve size particles) in the heap leach feed will slow the percolation flow of the leach solution, cause channeling, or produce dormant or unleached areas within the heap. This may result in unreasonably long leaching periods and poor extractions. In extreme cases, the clays or slimes can completely seal the ore heap, causing the leach solution to run off the sides of the heap rather than to penetrate the ore heap. The problem of heap leaching ores containing fines can be aggravated during stacking and preparation of the ore heaps, because natural sorting of coarse and fine material occurs during these steps (Johanson, 1978). This phenomenon results in a concentration of ore fines at the center of individual ore piles and a concomitant concentration of larger rock fragments on the lower slopes and base of the piles. When the individual piles within the heap are leveled off prior to installation of the sprinkling system which delivers the leach solution, additional segregation occurs as the fines sift through the coarser ore particles. The segregation results in localized areas or zones with marked differences in permeability. As a consequence, the leach solutions follow the path of least resistance, percolating downward through the coarse ore regions and bypassing or barely wetting areas that contain large amounts of fines or slimes. Effective utilization of marginal gold and silver resources through heap leach processing requires the development of new methods in order to achieve more uniform size distribution during ore heap preparation and better slime control during leaching.

Jan 1, 1988

By S. M. Spottiswoode

Rock mechanics benefits of stope support in deep-level mining originate principally from the ability of the support to resist relative movements between the hangingwall and the footwall. While the role of stabilizing pillars and backfill on reducing the energy release rate (ERR) at the face is well understood on the basis of elastic behaviour of the rock mass, the effect of support on controlling movement of fractured ground around deep-level stopes has not yet been thoroughly studied. As part of a programme of studying the behaviour of this fractured ground, geophones were placed 10 m from the face on the roof and floor of a longwall stope in which packs were used as supports. It was found that differential movement between the roof and floor generally exceeds average stope movement during a seismic event. Conventional support therefore transmits very little seismic energy; this is expected to remain true until complete convergence occurs. In backfilled stopes, backfill can become at least as stiff as the fractured wall rock. This will have the effect of reducing the length of the hanging- wall beam. Amongst other rock mechanics considerations, a shorter hanging- wall beam should: (i) increase the resonance frequency of the hangingwall and thereby decrease the levels of vibration for seismic events with M > 1,0; (ii) reduce absolute vibration levels by increasing the mass of rock immediately adjacent to the stope which is shaken by seismic waves; and (iii) reduce differential movement between the roof and floor and thereby reduce cyclic strain on the backfill and on gully support.

Jan 1, 1988

By W. H. Hodgson, A. R. Preston

"Improved rail production techniques provide new options for the rail user. Steelmaking improvements offer tighter composition control, lower oxide and sulphide counts, greater control of segregates and freedom from hydrogen problem s. New ultrasonic, laser and eddy current equipment gives printout information on surf ace flatness, straightness and internal condition. These have come along at a time when dramatic changes have occurred on the rail heat treatment scene. Rails can now be deep hardened on or offline in ways which should eventually result in a complete rewrite of the world's specifications. Rails of simple composition can be produced in the hardness range 2801400 BHN as required. The rail user can choose the hardness within this range according to requirement without the necessity for any step changes in the process routes.It is suggested that this is the pattern f or the next decade.IntroductionRails have been the subject of very slow improvement over many years but developments gathered momentum in the early seventies. Recent improvements in quality and properties have provided dramatic increases in rail life under the more severe service situations. Rail profile grinding, lubrication and other track improvements have greatly added to expectations of even longer life. All of this, coupled to even newer mill heat treatment developments, tilt both technical and economic advantages away from tradition to the point where specifications will need to be rewritten so that railroads can take full advantage of these new products."

Jan 1, 1988

The only functional underground Coal Mine in Nigeria is located in Enugu in Anambra State. For some years now the mine has been beset with a perenial problem of flooding. This has hampered produc- tion and some time ago the mine was abandoned. Recently money and equipment were made available to reactivate the mine. Attempts are now made to increase production as it is very much below demand. However, there are problems as the mine is below the water table under some major rivers and any advance exposes men and equipment to water surge. The paper traces the different attempts made to dewater the mine and the problems encountered in producing coal in this mine.

Jan 1, 1988

By David G. Borg, John Bussey

The new AIRDEK (tm) technique for pre-splitting in surface coal mines produces highwall conditions that have greater safety with lower costs for explosives, labor, and drilling. Successful applications have been made in highwalls ranging from 20 to 100 feet or more and in blasthole diameters from 3-1/2 inches to 12 inches.

Jan 1, 1988

By Robert B. Parsons

"One of the disadvantages of the federal government's idea of ""taxation by consultation"" is that it seems to take longer to enact new legislation. The proposed new rules for taxing automobile benefits is one example. Here is a ball which has been batted around between government and the public several times and still has not come down to earth. Fasten your seatbelts, there may be more to come. IntroductionThe draft legislation released on April 13 contains the details of the government's current proposals on car expenses and benefits. They differ significantly from the last announced position. Finance Minister Wilson has indicated that the release in draft form will provide an opportunity for the Commons Standing Committee on Finance and Economic Affairs (the Blenkarn committee) and other interested persons to comment before the legislation is introduced in Parliament. Accordingly, there may yet be revisions.Notwithstanding the prospect of further changes, the proposed rules generally come into force in 1988. While taxpayers may welcome some of these changes, particularly the increase in the tax-exempt allowance, many must be frustrated that, at this late date, the rules for the current taxation year are not yet finalized."

Jan 1, 1988

By Just G. D

The results of a geostatistical analysis of geochemical data obtained from field measurements are described in the paper. Q values derived from seismic signal rise times for different travel paths in the rock masses were used in the study. Cross-hole seismic measurements made at surface and underground sites formed the basis for the work. Geostatistical estimation of average l/Q values for area of the rock were compared with geological interpretions of rock type distributions. Reasonable correlations were obtained between the two methods of rock quality estimation.

Jan 1, 1988

By Pyrih R, House A, Shangraw J, Silva AJ

Sunbeam Mining -Corporation has the inten mine with heap leach gold recovery, near spent ore indicated a relatively high ar topographical configuration, the spent across a small drainage and a lake. Du permit for spent ore disposal from th agencies, concerns about the potential contamination by the arsenic were expres conducted extensive studies to addre contamination. These studies consiste( geochemical and geotechnical parameters underlying the proposed disposal si geotechnical investigations were also hydrologic characteristics were include with the use of an IBM PC computer. :ion of opening an open pit gold Stanley, Idaho. Testing of the ?enic content. Due to the local ore was planned to be disposed :ing the process of obtaining a federal and state regulatory for surface and ground water .ed. Sunbeam Mining Corporation is the potential for arsenic of laboratory testing of both of the spent ore, and the soils te. Field hydrogeologic and -onducted. Local climatic and 1 in the analysis of these data Conclusions of studies indicated that although the seepage through the spent ore disposal would contain an elevated dissolved arsenic content, the hydrologic and geochemical characteristics of the site would prevent arsenic migration into the local ground water system. The attenuation of arsenic on soils with high clay content, and dilution after reaching the ground water table would lower the arsenic content to acceptable Concentrations.

Jan 1, 1988

For tax purposes a mining company is a New Zealand company whose principal source of income is from the business of mining, or exploring for certain specified minerals in New Zealand. New Zealand tax law distinguishes between a non-resident mining operator and a mining company, with the only major difference in tax treatment being the corporate tax rates. New Zealand mining companies are taxed at 28 per cent, whereas non-resident mining operators are taxed at 33 per cent of taxable income. These provisions also apply to the petroleum mining industry. Individuals who carry on the business of mining are also specifically defined in the Act. They are termed as 'resident mining operators'. Non-resident mining operators are non-residents of New Zealand who carry on mining ventures as a business in New Zealand. Mining ventures are defined as the exploring, searching and mining of specified minerals, including development work carried out for profits. Similar provisions apply to the petroleum mining sector. Specified minerals are defined in the Income Tax Act 1976 ('the Act') and while no useful purpose is obtained by listing them in the paper, they include a larger number of industrial and commercial minerals. The Minister of Finance is also empowered to add to the list by publishing his determination in the Gazette.

Jan 1, 1988

"This paper describes some of the methods and equipment used for fine milling of minerals, and gives particular attention to the Vibro Energy system.In addition, the paper describes a specific application in the gold mining industry. This is the 200 tpd plant built by Anglo American Corporation at the President Brand Mine in South Africa in 1985, now a division of Freegold. This plant treats a gold bearing pyrite flotation concentrate which is finely ground to 15 microns prior to cyanidation and carbon-in-pulp (CIP). l .0 INTRODUCTIONFree milling gold ores are those that yield acceptable dissolution and recovery of the gold following grinding to what can be described as normal fineness, frequently between 50% and 90% passing 74 microns.Increasingly, gold metallurgists are faced with ores that are refractory. The traditiona1 treatment route for refractory gal d ores and concentrates has been by roasting, but for environmental reasons this is becoming less acceptable, or in some areas of the world, totally unacceptable. New methods of treating refractory gold ores are being developed and applied in practice. These new methods include pressure and biological oxidation. Higher gold liberation can also be attained by increasing the fineness of grind, although with conventional systems there are economic limits to this.In flowsheet development and test programs on new deposits, a standard procedure is to establish the relationship between the grind and subsequent go 1 d extraction. The normal situation is that gold extraction increases as the ore, or concentrate, is ground finer. Typically, this relationship is as shown in Fig. l, where the incremental additional extraction is very small once an optimum, or economic, grind has been achieved. This generally app1ies whether the material is free milling or refractory. The limits to grinding are set by the type of equipment which is commonly in use, usually ball mills. These mills have the obvious advantage of high capacity, however, they are increasingly inefficient as finer grinds are required. In general, ball mills are used to reduce ore to some agreed percentage passing 74, or possibly 53 microns."

Jan 1, 1988

By David C. Yang

A packed column (or static tube) flotation system is an innovative technology which utilizes a controlled dispersion reagent scheme and a new machine. The unique aspect of the machine is its packed-bed design permitting an unlimited froth bed height with countercurrent water washing for effective processing of fine particles. In operation, the conditioned ore slurry is fed into the middle section of the column where separation processes begin. Air, introduced at the bottom of the packed column, contacts the hydrophobic particles and floats them off continuously as the feed is added, while the gangue sinks to the base of the column. The system functions efficiently because intimate particle-bubble contact is achieved by the packing design which has no moving parts and requires no ancillary air-bubble generator. Other attractive features of the packed column flotation include high throughput, low power requirements, and simple control. Results from laboratory and pilot plant tests of this system show remarkable improvements over current industrial practices on a wide variety of ores and coals.

Jan 1, 1988

By C. J. Hall

I would like to congratulate Professor Gershon on an idea that is obviously valuable and is certainly new to me. It has, however, to be further developed, in that one can get fallacious results by limiting oneself to positional weights. In the example problem, the positional weight of one block was 8.6 (the 8.0 value in the paper was incorrect) for 36 units in the cone, for a mean block value of 0.239. The positional weight of the second block was 4.4 for 15 units, for a mean block value of 0.293. Surely one would expect the second block to be rated higher. Additionally, the time value of money adjustment cannot be determined by depth, because the time that a block is mined is determined by the mining sequence, not depth. Figure 1 shows a slightly altered version of Professor Gershon's pit. The overall value of the pit is the same, as are the total values under each of his blocks. The values in the right-hand cone have been reversed top to bottom, and the values in the rest of the pit adjusted to keep the central cone total unchanged. All values have been multiplied by 10. Figure 2 shows the sequence of mining, at three blocks per year, for Professor Gershon's pit, and Fig. 3, the sequence for a pit under the other block. Table 1 shows the value and discounted value (15%) of Professor Gershon's pit, and Table 2 shows similar values for the second pit. It is apparent that the second pit schedule is more valuable than the first.

Jan 1, 1988