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By V. K. Gupta

A detailed laboratory study was carried out to investigate the effect of the particle size distribution on the grinding rate parameters, Si, for the dry ball milling of quartz and limestone. Contrary to the present belief, the Si values were found to vary strongly with the particle size distribution. In particular it was observed that: (i) the Si values increased with the fineness of the particulate charge - the increase being more pronounced in the case of the coarser sizes, (ii) the next finer size class had the maximum effect on the breakage of the particles of a given size class, while the coarser size classes had only a slight effect, (iii) the effect of two or more size classes was non-additive, and significant higher order inter-size interactions were indicated. The importance of these results in the context of the analysis, design and scale-up of the comminution systems is discussed.

Jan 1, 1987

By Donald Whittaker

Severe climatic conditions in mines are normally associated with working at depth. More precisely, it is a matter of working in regions of high strata temperature, since, for example, some coal mines in the Ruhr have strata temperatures at 1000 m which are matched only at 3 times that depth in the South African gold mines. In Britain we are perhaps fortunate in encountering strata temperatures in our deeper coal mines some 10-15 K lower than at the same depth in the hot mines of the Ruhr. Nevertheless the problems of high temperatures and humidities in UK mining operations, which in the past have been confined to a few specific sites, have in recent years become more widespread, and there is every reason to suppose that the trend will continue. Clearly strata temperature is not the only .causative factor. Long ventilation circuits serving districts remote from the shaft must also play a part, while the heavy use of machinery and the rapid, rates of excavation of modern mining methods are obviously important. It is necessary to understand the mechanisms of all such factors, and to measure their magnitudes and fluctuations, if remedial measures are to be properly designed or predictions made which are accurate enough to be of use in ventilation planning. This paper presents the results of a long-term (and continuing) investigation carried out in several mines to measure the major sources of heat and moisture on longwall districts and trunk conveyor roadways. The variation with time of these sources is reported, and the resultant effect on the climate is considered. In their investigations of the heat exchanges occurring in a whole mine Oakes and Hinsley (1955-56)1 listed and estimated the magnitudes of a large number of heat sources. Some of these, namely autocompression of the air in the shaft, diesel engines and compressed air mains, do not apply to the present investigations, which refer to longwall districts with conveyor transport and no compressed air supply. Others, such as oxidation of coal and, desorption of methane, have not been taken into account in the measurements, but are discussed later. One other source, the importance of which was pointed out by Gracie and Matthews (1975)2, is the coal on the conveyor, a form of strata heat emission, but one which is strongly dependent on the rate of coal production. The heat emissions measured in the present investigations were the energy consumed by electrical machinery, the heat conducted from the strata and the heat lost by the conveyed coal. Most of the emitted heat was removed from the district by the ventilation air, and was measured by continuously recording the enthalpy of the air at fixed stations. The heat removed by service water, supplied for machine cooling and dust suppression, was also measured. Account was of course taken of the relatively minor changes in level around the districts, in terms of the potential energy gained or lost by the coal and by the ventilation air (autocompression).

Jan 1, 1980

By Stanley R. Riggs

The rocks exposed in the phosphate district are of Neogene age and consist of clayey quartz and phosphorite sands overlying phosphatic dolomite. The Bone Valley Formation is redefined as a marine phosphorite containing primary phosphorite and abundant terrigenous sediments. It contains a Middle Miocene vertebrate and invertebrate fauna and conformably overlies the Hawthorn Formation containing similar invertebrate fauna. A new, unnamed formation, with Pliocene and Pleistocene fauna and containing reworked phosphorite, overlies the Bone Valley disconformably. Its phosphorite is derived from the subjacent Bone Valley by post-Middle Miocene erosion and deposition in stream channels and marginal marine environments. The Bone Valley contains two main types of primary marine phosphorite. Orthocbemical phosphorite, a direct precipitate of microcrystalline phosphorite (microsphorite), occurs as a cement or binder in thin beds. Allochemical phosphorite consists of clastic phosphorite particles that were originally formed as microsphorite on another part of the shelf. Microsphorite was deposited in a very shallow open marine environment which had an abnormally high phosphorous content caused by upwelling currents. The mechanism of deposition is still in doubt, but organisms probably were a major factor. Soon after deposition, microsphorite was indurated, periodically torn up, and the resulting fragments transported and deposited elsewhere on the shelf. These processes account for a great portion of the clastic phosphorite in the Miocene deposits of Florida. The primary fossil skeletal material is of minor importance.

Jan 1, 1965

By James G. Tilton

Subsidence resulting from mining operations, has been the object of sporadic study for many years. Reports have shown that subsidence has ranged from minor settlement detected only by precise measurements to great slips where buildings are destroyed, roads disrupted, and large fissures opened at the surface. For years, a controversy has raged over the question of whether there is a positive or negative angle-of-draw. None of these questions can be given a flat answer for the variables controlling, subsidence are infinite. Generalizations can be made for various situations and areas but some means of control must be executed.

Jan 1, 1966

By A. Mukherjee

This paper presents an analytical technique for prediction of the damaged rock zone (DRZ) around a circular drift subjected to an anisotropic stress field (analytical solution exists only for the case of hydrostatic stress field). The method can readily be adapted to micro or personal computers. Stress concentrations around the drift are calculated at the centers of small rock elements, using the analytical solutions for a hole in an infinite plate. Potential failure of a rock element is assumed to be governed by the Coulomb failure criterion. When the failure condition is exceeded for an element, the excess shear stress is transferred to the neighboring elements. Progressive failure is allowed to occur until convergence is obtained. The final configuration of the damaged rock zone so obtained can be used to assess rock support requirements, as well as modified modulus and permeability of the DRZ.

Jan 1, 1988

By Jameel Menashi

A process has been developed for recovering the refractory metal values contained in mixed secondary source materials such as contaminated grinding wastes, oxides and sludges. The wastes are calcined with sodium carbonate in air to convert the refractory metals to water soluble Na2CrO4, Na3V04, Na2Mo04 and Na2W04. The base metals, Fe, Ni, Co and Cu, are converted to water insoluble oxides. An aqueous leach of the calcine effectively separates the refractory metals from the insoluble base metals. Co, Ni and Cu can be recovered from the oxidic residue by conventional processing methods. The leach solution is purified and then treated to recover the refractory metals as Cr203, NH4VO3, (NH4)6Mo7024?4H2O and H2WO4. The purity of the products is sufficient for their use in many metallurgical applications. The Na+ values in the leach solution are recovered as Na2CO3(or NaHC03) and are recycled to the calcination step. It is shown that the process can accommodate a wide range of feed compositions and generates a minimum of aqueous effluents.

Jan 1, 1984

By Musa D. Manzi, Raymond J. Durrheim, Richard T. Masethe

Large mining-induced seismic events and their aftershocks cause hazardous working conditions, damage infrastructure, delay production and pose a risk to miners in the deep-level gold mines of South Africa. Stress changes affecting pre-existing zones of weakness are the main drivers of large mining-induced seismic events, which are often followed by aftershocks triggered by quasi-static stress transfer within the rockmass. A better understanding of seismic source mechanisms is important if the seismic data is to be used more effectively for mine planning and to reduce the rockburst risk. Four large seismic events (ML≥2.0) associated with the mining of the Ventersdorp Contact Reef (VCR) at Kloof Gold Mine occurred on 13 June 2017. The events and their fore- and aftershocks were studied in detail to establish the circumstances and the cause of the incidents. The local magnitudes ranged from ML 2.3 to ML 3.0, the seismic moment from 0.69 to 2.25 x 1013 Nm and the source radius from 92 – 150 m. The main shocks were preceded by foreshock sequences, which were especially vigorous in the four hours before the main shock. Seismicity was recorded by in-mine arrays of three-component 4.5Hz geophones (detection threshold approx. ML -2.9). Following all four main seismic events, ML 2.3, ML 2.3, ML 2.9 and ML 3.0, the network detected a total number of 300 aftershocks ranging from ML -2.9 to ML 1.6 spread within a 1300 m radius from the centre of the seismic network. The statistical properties of the aftershocks were analysed using three scaling relationships: (i) Gutenberg–Richter frequency magnitude relationship; (ii) modified Omori’s law; and (iii) Båth’s law for the magnitude of the largest aftershock. The geological or mining feature that controlled the failure (e.g., fault, dyke, pillar, abutment) was determined by calculating the orientation of the nodal planes of the large seismic events using moment tensor analysis and studying the aftershock distributions.

Apr 26, 2022

By Melvin W. Kraschnewski

In 1966 Central Ohio Coal Company and Bucyrus-Erie signed a contract authorizing Bucyrus-Erie Company to design and build a 220 cubic yard dragline. This dragline would be used for stripping overburden from their coal reserves located near Cumberland, Ohio. The size of the machine was arrived at after a thorough application study of their annual coal output requirement, depth of overburden and type of terrain. The design and construction of this machine which has been designated by BECO as model number 4250-W is the title of this paper. Size wise based on machine weight the 4250-W represents an increase factor of three over our largest current dragline. Probably the easiest way of presenting a machine of this size is to build it from the bottom up.

Jan 1, 1969

By J. P. A. Hortley

In conventional electrolytic copper production, looped copper starter sheets, on which the copper is deposited, are supported by hard-drawn copper bars. These bars have cross-sectional areas of between 1 and 1.4 in2. The suspension bars serve two purposes: firstly to support the cathode, which can weigh up to 150 kg, and secondly to introduce the electric current. IYI examined these two requirements in detail to see whether a better design could be achieved. Considering firstly the current carrying requirement, it wee noted that under normal refinery conditions, each cathode carries between 400 and soak. If one applies the generally accepted rule that 1 in of copper can carry 1000A4 a suspension bar need theoretically contain only 1/2 in2 of copper. This contention is supported by the fact that the 500A current passed through the cathode also appears to pass quite satisfactorily through the two support loops, which have a cross-sectional area of approximately 0.35 in 2. Turning now to the strength requirements, the cross-section of hard-drawn copper bar required to support a 150 kg cathode is relatively small, and easily met by the present designs. It is not, however, the static load applied by the 150 kg cathode immersed in the electrolyte which causes the damage to the hard-drawn copper, or even the increased static load of a 100 kg man standing on one foot in the centre of the bar; the damage is actually caused by the dynamic loads applied to the bare when they are dropped, thrown into containers, lowered too rapidly into the cell, or otherwise mistreated. The important requirement is therefore that the bar does not permanently bend. Its proof stress of limit of proportionality, rather than the amount that it deflects under static loading, should be the strength criterion. With the hard-drawn copper normally used for the manufacture of suspension bars, it has been observed that the copper becomes annealed during use, particularly at the end of the bar where the current is introduced. Thus, after a relatively short time, the cathodes are in effect being supported by annealed copper bars.

Jan 1, 1978

By Daniel T. Brian, O&apos

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summary. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition, and development planning are presented in this paper.

Jan 1, 1969

By R. R. Klimpel

The grinding of coal-water slurries has received increasing industrial attention during the last decade. In particular, there is long-term interest in the use of pulverized coal-water slurries to replace oil in combustion equipment and the development of coal gasification/liquefaction processes which require coal-water slurries as feed. More specifically, the use of coal-water slurries in gasification requires grinding a high density slurry containing the smallest amount of water consistent with slurry pumping and spraying. As part of a fundamental engineering research support program aimed at the industrial implementation of dense coal-water slurry grinding, this author has published several papers on how specific rates of breakage vary as a function of slurry rheology, Klimpel (1982, 1982/83). These papers demonstrated that there is a consistent pattern of change in specific rates of breakage of coal in dense slurries with controlled variations in slurry rheology. By matching rheological data with laboratory grinding results, it was possible to identify directly slurry conditions that correspond to: (1) slowing down of breakage rates, (2) the occasional acceleration of breakage of some sizes, and (3) conditions where chemical additives will increase rates of breakage.

Jan 1, 1990

By R. K. Singhal

In open pit mining every effort is made to maintain as steep a pit slope as possible. Pi t slope angles are influenced by numerous factors some natural that are amenable to limited or no control at all and other mining technology related where a greater degree of influence can be exerted by the engineer. One such area where control is possible is the method of drilling and blasting in the pit. This paper discusses the influence of blasting techniques on the economics of pit slopes and demonstrates how balanced blasting can be used with advantage to pit wall control and improve fragmentation (thus reducing material handling costs). Microprocessor based instrumentation to monitor drill and blast performance has also been described.

Jan 1, 1988

By G. Johnston, P. K. Chatterjee, S. Holguin

M. Gershon The article is an excellent one, providing a basis for the conduct of the major tasks in underground mine planning and scheduling. I object to only one word. Since that word is featured in the title, it is a strong objection. The word used erroneously is optimization. There is no optimization performed in the article. By definition, an optimization is an approach that yields the best of all possible solutions. We can limit this definition to its narrowest sense, the optimization techniques of operations research such as linear programming, or broaden it to include less sophisticated search procedures that find the best mine plan or schedule. No such claim is made in the article. No optimization of any kind is performed. The major tool used is a simulation, which, in truth, is probably more appropriate for this problem than any optimization. But simulation does not optimize. It only allows for quick evaluation of many options, leading to the selection of the best plan "of those tried," not "of all possible plans." This article, of course, is not the first mining paper to make this error. It seems that the word optimization is used more to impress people than to refer to any act of optimizing. It is used in a way that implies "try to optimize"or "come close to optimize," but not to really do it. It is usually appropriate to quietly ignore this error. But when Dr. Chatterjee, who has done so much good work in true optimization projects and whose work I have come to admire, makes such an error, it is time to publicly dispute it. Having discussed this very point with him in the past, I am sure that he will agree. If he can support this position in his response, perhaps people will start to listen and we can reduce the number of false claims of optimization. This should be easy for him in this case since the approach he used, simulation, is the more appropriate one anyway.

Jan 8, 1988

By M. J. Laurila

Elemental analysis of slurry streams using X-ray fluorescence (XRF) has long been employed. However, detector technology has limited the application of XRF devices. Using detector technology employed on NASA's Mars Pathfinder to analyze soil samples, Process Control, Inc. has developed an on-line analyzer to mount on a sampling system. The prototype XRF elemental analyzer was installed at Detroit Edison's Monroe Power Plant in January, 1998 and has been employed to monitor feedstock quality. A slurry system has been developed for flotation control. This paper describes the testing of the analyzer using the new, draft ISO standard for evaluating the performance of on-line analyzers (ISO/DIS 15239).

Jan 1, 1999

By A. D. Davis

The disposal of spent ore from cyanide heap-leach processing facilities is of concern to the mining industry, regulatory agencies, and the public. Disposal of several hundred million tons of additional spent ore is planned in the western United States during the next decade, with increased amounts likely if gold prices rise. In the past decade, more than fifteen million tons of spent ore have been disposed of in the Black Hills. South Dakota's off-loading criterion for cyanide has been set by the state's Department of Environment and Natural Resources at 0.5 parts per million (ppm) as weak acid dissociable (WAD) cyanide. Nitrate off-loading limits vary for each mine in the state, depending on ore type and other factors. Nitrate concentrations in leachate from spent ore depositories could be caused by conversion from other nitrogen-containing species. One likely source of nitrate is residual explosives from blasting of ore. Previous work on the combustion products of nitrogen explosives has shown incomplete 3xidation (Johansson and Persson, 1970). Another likely nitrate source is degradation of cyanide to ammonia, followed by oxidation to nitrite and nitrate.

Jan 1, 1994

The value of US industrial mineral output last year was $20 billion, a 12% decline from 1981. A glance at the accompanying table and a review of the comments made by several contributors reveals how poorly many industrial minerals fared during 1982. Bromine and peat posted a 6% increase in production while recovered sulfur showed only a 3% gain over 1981. Pumice, salt, and dimension stone managed to stay more or less even with 1981 production. However, most industrial minerals posted losses for the year from 3% for vermiculite, sodium carbonate, and gypsum to 49% for ilmenite. Naturally, the depressed economy is to blame for decreased production and consumption. Low steel and auto production, lower housing starts, and many other factors impacted the industrial mineral industries. Hopefully the worst is over. Interest rates are down, energy costs are decreasing, the automobile and housing industries show signs of picking up. Perhaps the 1983 annual review will be less gloomy. Many thanks to these industrial minerals technical committee members for their contribution to this year's annual review: G. S. Austin, E. S. Montgomery, H. P. Ehrlinger III, D. B. Jorgensen, R. L. Parratt, J. F. Burst, W. Mallory, N. C. Trivedi, and N. K. Olson.

Jan 5, 1983

By K. N. Santini

Natural zeolites are gaining recognition as an important commodity with an increasing number of industrial and consumer applications. This potential has prompted the Anaconda Minerals Company and other firms to investigate occurrences and markets for zeolites. The deposits of mordenite-rich tuff at Rome are of interest for their economic potential and for the excellent opportunity they provide to study a zeolite deposit formed in a hydrologically closed basin. Location The Rome property is located approximately 9 km west of Rome, Oregon, in Townships 31S. and 32S., Range 41E., Malheur County. It lies within the Owyhee Uplands of the northern Basin and Range physiographic province (Figure 1). The area discussed here includes a major portion of the depositional basin in which the zeolitic tuffs occur.

Jan 1, 1982

By R. L. Frederking

Geological remote sensing is, "....the study of the Earth utilizing electro-magnetic radiation (EMR) which is either reflected or emitted from the land surface in wavelengths ranging from ultra-violet (0.3 micrometre) to microwave (3 metre)."1 Selected examples which illustrate a variety of successful geologic applications include lithologic mapping, 2 engineering soils mapping,3 tectonic interpretation,4 and mineral and petroleum exploration.5 This report examines the applicability of remote sensing for bauxite exploration in northeastern Mississippi. Specific objectives were to map lithologies of northeastern Mississippi from LANDSAT imagery, to determine the utility of LANDSAT imagery for delineating and mapping known deposits of bauxite, and to discover and map new bauxite deposits.

Jan 1, 1977

By Donald P. Schlick

Gentlemen, today I would like to talk to you about metal and nonmetal mine health and safety--past, present and future. Briefly, I will comment on the past because it is important to an understanding of our present activity and our plans for the future. Federal inspection of noncoal mines was not authorized until 1966, when congress passed the federal metal and nonmetal mine health and safety act; public law 89-577, with the passage of this act, the federal inspector, for the first time, had the delegated authority and responsibility to enforce health and safety regulations designed to prevent personal injuries and occupational diseases, the new law also provided for the education and training of our miners; assistance to the operator through the transmission of technical and scientific information and assistance and equally important, the law made provision for state participation in the congressional mandate to prevent injuries and save lives in the mineral industry, Before I tell you about our program and our future plans, I want you to know that I am here to listen as well as to talk! In my view, the only kind of communication that is meaningful is two-way communication. Our nationwide progress in metal and nonmetal mine health and safety during 1972 cannot be measured in reduced fatalities or injuries. The unforeseen tragedy that took pace in Kellogg, Idaho, in may of last year mode that almost a certainty.

Jan 1, 1973

By Richard F. Roethe

Surface coal mining productivity in the U.S. and Illinois has shown a general declining trend since 1969. The U.S. Department of Energy conducted an analysis in 1980 of the causes of declining productivity in different states. This paper presents a detailed analysis of changes in overall productivity and productivity in different functions such as overburden preparation, overburden stripping, reclamation, coal handling, etc. during the period 1970-1982. Statistical analysys techniques including multiple regression were utilized in the study.

Jan 1, 1983