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By Stuart Brashear, J. W. Reil

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the authors elect, they may distribute copies at the time of the Symposium.

Jan 1, 1986

By D. J. McParland

This paper will deal with some of the considerations which, were involved in the design and construction of the uranium mills in the Elliot Lake area . These plants, eleven in number, range from 1500 to 6500 tons per day milling capacity. Most references are with respect to the seven plants in the Rio Tinto Group which have a combined milling capacity in excess of 20,000 tons per day. In dealing with such abroad subject as mill design, one has the choice, of covering a few specific problems in great detail, or else attempting to cover many subjects superficially and briefly. In preparing this presentation, an attempt has been made to compromise on these extremes, and to select some interesting illustrations which are of general interest in the field of mill design, and of value to persons concerned with mill design broadly, beyond the field of uranium mills.

Jan 1, 1959

By K. J. Sollman

As a class, silicate minerals have likely found the broadest, if not largest volume, use in combination with polymeric binders of all industrial minerals. Among the silicates, calcium metasilicate, wollastonite, enjoys a front runner position in a near universal sense. It is a viable and desirable part of composites ranging from thin films to large moldings; from a common filler/extender for paint for your garage to a reinforcement for the exterior surfaces of a luxury vehicle affordable to very few. This article is focused upon the variations in particle morphology and the surface characteristics which, by way of commercial examples and discussion of active research programs, make this environmentally benign mineral so unique.

Jan 1, 1993

By Wenbing Guo, Gaobo Zhao, Erhu Bai, Brijes Mishra

"Violent damage to overlying strata can occur above the large mined-out space left by high-intensity longwall mining. For the safe mining under the aquifer and surface water body, it is imperative to investigate the criteria of overburden failure degree due to high-intensity mining. In this paper we present the characteristics of high-intensity longwall mining panels and overburden critical failure. Based on the geological and mining conditions of a high-intensity mining panel, 3D numerical models that consider the maximum horizontal principal stress and minimum horizontal stress and their orientations with the panel advance direction were established by using the 3DEC software. Sizes of the panel reaching the critical failure of the overburden under different mining thicknesses (3.5 m, 6.5 m, 9.5 m, 12.5 m, and 15.5 m) were analyzed. Further, criteria of overburden critical failure were proposed for the high-intensity mining. The coefficient of overburden critical failure (Cf) is the ratio of the strike length (Ls) to the mining depth (H). Through curve fitting analysis, a fitting equation between Cf and mining thickness was obtained. The results showed that overburden failure criterion with high-intensity mining panel is 0.38 = Cf = 0.97 with different thicknesses. Field measurements validated the results from the numerical models.INTRODUCTIONHigh-intensity longwall mining refers to a coal mining method with thick coal seam, large panel width, fast face advance rate, and severe damage to the overburden and surface in China (Guo et al., 2018). Violent movement of the roof rock and severe damage to overlying rock strata occur in the large mined-out space left by a high-intensity longwall mining panel, which is a 3D (three-dimensional) structure layout with highly non-uniform stress distribution. Recognition of such fact a will facilitate this overlying rock strata failure problem investigation (Peng et al., 2019).The studies of overlying strata failure due to longwall coal mining have been reported by some scholars with different methods. Kang et al. (2018) studied the sudden massive roof collapse during longwall coal retreat mining by a large-scale two-dimensional physical model and a UDEC numerical model. Ghabraie et al. (2015) researched the mining-related strata movement by applying the three-dimensional laser scanner, optical transducer, and digital image processing techniques to two-dimensional physical models. Wang et al. (2015) analyzed the structural characteristics and fracture failure process of overlying hard and thick main roof by a 3DEC numerical model; this study also investigated the geostress reduction and permeability enhancement redistribution of the adjacent coal measure strata by FLAC3D. Guo et al. (2012) performed a three-dimensional finite element analysis and shared some insights into the dynamic interaction between mining induced strata stress changes, failures, and gas flow patterns. Meng, Shi, and Li (2016) proposed a 3D coupling model between stress and permeability, investigating the dynamics of a stress, permeability coefficient using FLAC3D. Khanal, Guo, and Adhikary (2019) used the 3D numerical modelling approach (COSFOW) to investigate the strata deformation and the change in permeability in the overburden strata due to the underground extraction. However, few studies considered the influence of the horizontal stress on overburden failure in a high-intensity longwall mining panel, and the critical failure criteria of overlying rock strata is unclear."

Jan 1, 2019

By M. P. Meehan

The purpose of this paper is to present the key elements in a system; study of the electrical system for a timing and/or tilling operation. The ability of an electrical system to function in a reliable fashion at its proper levels is essential for an operation to be successful. A system study consists of a load study for determining the capability of the electrical network to provide power to the various loads and a short circuit study for determining the capability of the electrical protective equipment to properly protect against fault conditions. The sequence of events in a system study is data acquisition, determining the electrical parameters and analyzing the ability of the system to meet these requirements. If the system is small, herd calculations will be the manner in which the study will be conducted; if it is large then commuters will be used. A load study has as its objectives the determination of the capability and reliability of the source of power, transformers and conductors to satisfactorily deliver power to the loads at an acceptable voltage level. The Information required is a single line diagram showing the source, transformers, conductors and loads.

Jan 1, 1980

By L. S. Rubin

The efficient and acceptable disposal of fine coal refuse (28MxO) is one of the highest priority problems facing the coal industry today. For many years the established system for the disposal of this fine refuse slurry has been to concentrate the solids in a static thickener and pump the resulting 20-40% solids underflow to lagoons or impoundments. Although this technique has served the coal industry well, increasing environmental concerns and refuse related disasters, such as Buffalo Creek, West Virginia and Aberfan, Wales, Great Britain have resulted in federal and state regulations which now control fine refuse disposal methods. As a consequence of these regulations, the capital costs of constructing, maintaining, and operating regulatory complying impoundments has become in many cases economically unattractive. Areas processing topologies similar to those coal preparation plants of the Appalachians are particularly burdened by these regulations and are consequently turning to alternatives for handling and disposal of their fine coal refuse. The basic requirements of impoundment alternatives as defined by environmental and plant demands are: (1) A relatively solids-free liquid (1000 ppm or less) to serve as plant make-up water in a "closed circuit" system, and (2) a sufficiently dewatered solids product which can be combined with the coarse refuse to form a compactable stable land-fill.

Jan 1, 1978

By Gene Mattila

Each installed rock bolt costs in excess of 520.00. High cost in conjunction with the primary purpose of safety makes it only logical to install the highest quality anchors possible. Each bolt has designed support capabilities in axial, shear and fluctuating ground condition, if installed to manufacturers recommendations. The quality of anchor is not; however, only affected by material specifications, but by transportation, handling storage, installation procedure, machine performance and geology. The quality is not only affected by many variables, but reliability should be assured. Non-destructive methods of testing reliability are only available for several types of bolts.

Jan 1, 1985

By Kathleen A. Altman

INTRODUCTION The basic premise of the ideas presented in this paper are as follows: Engineers believe that "theoretically" it will work. Operators ask what they must do to make it work. And, people can screw it up. r Today the challenges conf onted during the engineering, startup and operation of mines are becoming more complex. As mining and processing professionals, we are called upon to trav­el all over the world, are subjected to a wide variety of climates and must deal with a numerous cultures and people. Historically, for the majority of the people working in the mining industry, the primary challenges related to projects have focused on the differing perspectives of the disciplines involved. For example, geologists focus on resources and reserves, mining engineers relate to tons or tonnes, metallurgists count ounces or pounds or kilograms of product, mechanics emphasize availabil­ity, human resources personnel deal with absentee rates and turnover and accountants watch the bottom line ($$'s). As the world has become "smaller" and the mining industry has become more globalized, the puzzle is becoming increasingly difficult. Even the most experienced in the crowd of mining profes­sionals are oftentimes surprised by the types of problems that are encountered. Try as we may, we cannot anticipate the complex­ity of dealing with the human side of an operation.

Jan 1, 1998

By David Martin Menne

In a small tank, slurry is passed through the high shear impeller zone with small time intervals, and a large proportion is regularly exposed to air at the surface, and at relatively high shear rates. This accounts for significant differences in the performance of large and small tanks. It is preferable to derive data where possible directly from an operating plant rather than applying data generated in small tanks where allowances must be estimated for the above differences [and where slurry aging and often substantial cooling compared to hot freshly milled ore further distorts results]. Various measurements have shown that many gold slurries can suffer extreme variability, as streamers of bypassing material or boules of hold-up periodically condstitute the instantaneous discharge from a tank - the relatively high Yield stress of slurries [around 1 to 10 Pa] causes very incomplete homogenization of slurry in any tank, the worse the larger the tank and the more viscous the slurry. To provide a background for this subject, this monograph presents leach and adsorption models based on the fundamental physics and chemistry of these processes, and includes quantitative discussions of factors which can lead to deviations on scale-up. The Throughflow model which avoids the need for such alowances is then presented, as well as a Computer Programme applying this model, and which allows direct calculation of the effects of:

Jan 1, 1995

By Andreas Rubo, Stephen Gos

Over the past couple of decades several endeavours have been made to develop lixiviants with the intention of replacing cyanide in gold leaching. In 1980s these endeavours were largely economically driven, due to cyanide shortages at that time. In more recent times, the driving force has shifted to occupational health and environmental considerations. It is often argued that the high acute toxicity of cyanide alone makes it worthwhile considering to replace it completely by less toxic alternative lixiviants. This has led to having to consider more criteria in the choice of any alternative lixiviants, which have often not been taken into account in the past. The intention of this paper is to review these alternative lixiviants and also review the criteria, which have ultimately led to most of these lixiviants never having found any large scale application, if they passed laboratory stage at all. It is also intended to show, that by handling and treating cyanide in a proper manner, the overall profile for the use of cyanide compared to these alternative lixiviants is very favourable. The question to really be answered is whether there is actually any chemical or process applicable to gold leaching that does not show the high toxicity potential of cyanide and that is still favourable with regard to looking at a broader spectrum of criteria and not only acute toxicity.

Jan 1, 2000

By A. Founie

The United States continues to be the world’s leading producer and consumer of diatomite. Production of diatomite in the United States during 2005 was estimated to be 653 kt (720,000 st). This was a 5-percent increase compared with 2004. The value of processed diatomite in the U.S. was about $179 million in 2005. Production was from six companies with 12 processing facilities in four states. California and Nevada were the principal producing states. They accounted for about 70 percent of U.S. production in 2005. U.S. diatomite exports were about 144 kt (159,000 st). Imports were negligible. The internal structure and chemical inertness make diatomite an excellent raw material for filtration, absorbent and filler applications. Filtration, especially the purification of beer, liquors and wine and the cleansing of greases and oils, continued to be the largest end use for diatomite. Other applications include the removal of microbial contaminants, such as bacteria, protozoa and viruses in public water systems, and the filtration of human blood plasma. The use of diatomite as fillers and in pharmaceutical applications, including the filtration of human blood plasma, continues to increase as has its use as an insecticide base and as pozzolan. The relative rank of end uses of diatomite were filter aids, 75 percent; fillers, 11 percent; absorbents, 7 percent and other (mostly cement manufacture), 7 percent.

Jan 1, 2006

By H. C. Juvkam-Weld

R. Michael Craig Mr. Juvkam-Wold's article is a timely and much needed presentation of the method of depressurization to reduce ground-water inflow into mine shafts. The article is very informative and discusses the effects of depressurization upon shaft inflows adequately. However, the article omits a discussion of another important benefit of depressurization: the reduction of potential for artesian burst or, as it is also called, floor heave. Confined aquifer systems (artesian aquifers) can contain water under several hunder pounds per square inch (psi) of pressure. For example, water levels at elevations of 455 m (1500 ft) or more above the top of the Westwater Canyon member of Reply by H.C. Juvkam-Wold In general, Mr. Craig's comments are useful and accurate regarding the potential benefits of aquifer depressurization. However, two of his points require further explanation since they may lead to a misunderstanding of my paper and its predictions. These refer to his comments regarding failure to account for storativity and to non-artesian conditions. Equation 5 is indeed Darcy's steady state equation. However, as a careful review of the appendix in this paper will reveal, I have used this equation to represent semi-steady state conditions. In other words, steady state conditions are assumed at any instant of time, but conditions may change gradually from

Jan 2, 1983

By Charles F. Herbert

The waves of prospectors who struggled across the wide Alaskan wilderness between 1898 and 19 10 came close to but did not actually find the rich copper/zinc/silver deposits strung out along 161 km ( 100 miles) of felsic schist in the remote Brooks Range of northwestern Alaska. They had heard rumors of gold in the valley of the Kobuk River, so they skirted the Arctic ice pack in the Chukchi Sea and, in a force at least 800 men strong, ascended the Kobuk River in 1898. Twenty-eight placer mining camps were established but only a handful survived for more than a few years. One of the placers that died rapidly was Ruby Creek. A map showing the location of Alaskan mineral deposits is given in Fig. 1. The Ruby Creek miners, disappointed with the scarcity of gold in that creek, followed copper-bearing float to two places where the float was especially plentiful. Pits, a short adit, and a shallow shaft uncovered copper carbonates, bornite, and chalcopyrite in fractured limestone but the remoteness of the district blocked efforts to sell the claims or to raise capital for development. Shortly after 1906, the copper prospects were abandoned and, except for an account published in 1913 by the US Geological Survey, they were forgotten, as were the names of the prospectors.

Jan 1, 1991

By John R. Marks

The first 0.7 m3 (1 cu yd) diesel load- haul-dump vehicle (LHD) arrived at the Homestake Gold Mine in Lead, SD in I969 to muck a ventilation drift. Others soon followed. Mechanization has subsequently changed stoping methods, manpower requirements, ventilation practice, the definition of minable reserves, and it has impacted safety and health. These have all had a direct bearing on the economics of producing gold ore from deep underground. Mechanized mining Before mechanization, production quotas at Homestake were met by several open cut-and-fill (OCF) mining methods. OCF mining relied on jackleg and wagon drilling, electric and compressed air slushing and cribbed raises brought up through the fill. Even square- set stoping was used until about eight years ago. The mine became 100% mechanized in 1988. The two current stoping methods are mechanized cut-and-fill (MCF) and vertical crater retreat (VCR). In 1992, MCF accounted for 54’S, VCR for 44% and development/uphole for 2% of the 1.4 Mt (1.55 million st) of underground ore produced. These methods are typically ramp- based and use diesel-powered LHDs, trucks, pneumatic drill jumbos and utility vehicles. Electric LHDs and rubber-tired compressed air muckers have also been used in VCR scrams. Pfarr (1991) and Mitchell (1980) provide good overviews of current production methods.

Jan 1, 1993

By Bruce Congleton

The Florida phosphate industry is a leader in environmental control, both in terms of dollars spent and significant achievements. For instance, since 1960 the phosphate industry has spent over $71 million for air pollution and control devices, including installation, research and development and maintenance. Water pollution control expenditures also total in the millions, with over $69 million spent in the same 10 year period. The industry also is a leader in water conservation measures, having spent nearly $ 18 million since 1966 for conservation devices. Since phosphate is mined by strip mining, land reclamation plays an important part in the environmental control picture. Here again, the phosphate industry has met the challenge with a voluntary program of reclamation which accounts for over 20,000 acres of land useable after mining has taken place. In terms of progress in environmental control, the industry has been able over the years to solve within the limits of technology the fluoride emission problems it once had, and is currently at work solving sulfur dioxide and particulate problems. In just the past year the industry also has been extremely successful in limiting phosphorus and nitrogen discharges into area streams. The industry continues to cooperate with state and local pollution control officials on matters of environmental control, and future plans include even closer cooperation and assistance, as well as increased expenditures.

Jan 1, 1972

By J. F. T. Agapito

Significant economic benefits can result when rock mechanics is applied within a practical framework and integrated within the other engineering functions of the mine organization. Such application and integration requires management support and understanding of rock mechanics as a practical tool to help attain high standards of safety, productivity and resource recovery. For such an approach, a long-term geotechnical program is needed in most operations to build an adequate data base and to ensure that design and ground control issues are handled in a cost-effective manner. Best usage of rock mechanics in mining occurs when management recognizes the application as a long-term investment, where time is needed to realize good returns. The need for this approach is due to the difficulty in accurately predicting ground conditions ahead of mining. The practical application of rock mechanics must follow an iterative process of design and verification based on site-specific experience to account for geologic and mining impacts. Ground conditions experienced during mining must be used to check the initial mine design and, if necessary, to provide a basis for design modification. Such a practical rock mechanics program includes comparative experience, in situ instrumentation and numerical modeling. The program begins with the geologic site investigation and continues throughout the life of the mine. It is an integral part of mine planning and operation.

Jan 1, 1991

By Jean-François Bougard

It has already been said and written many times that the construction of tunnels in urban areas has proved more and more indispensable, if not vital. The subsequent development of tunnelling for 15 or 20 years has brought large and sometimes spectacular improvements in the fiel of execution methods. But, particularly in urban areas, the difficulties to be overcome have been and still remain very important. As a matter of fact, most of big cities, have been settled near rivers or lakes; therefore the geological nature of the subsoil is soft ground and the level of ground water is high. As a consequence, tunnelling is often faced with many well-known difficulties and dangers issued from decompression or loosening of the ground, sometimes accompanied by a lowering of the water table. This may compromise the safety of the excavation itself and of the workers, and also cause settlements which many severely damage nearby buildings or structures. This is the reason why it is always necessary to work out specially adapted methods and even to develop new ones. In most cases, each work is a particular one and has to be specifically studied since numerous data are to be taken into account, related not only to geology, cohesion and behaviour of the different layers concerned, ground water, the activity of it, but also to

Jan 1, 1979

By P. N. Psarropoulos

During many strong earthquakes in the past, a significant number of tailings dams failures has been recorded, leading in some cases to human life losses. However, over the last decades, seismic design of tailings dams has drawn much attention mainly due to the high environmental hazard. Although the stability of such geostructures under dynamic loading is mainly related to their liquefaction potential, there exist several technical issues that have not been adequately investigated. One of these issues is the impact of local site conditions on the dynamic earthquake stresses developed, and therefore on the inertial instability of these dams. Based on the models examined in the first part of the present study (Stability of Tailings Dams ? Part I: Static Loading), two-dimensional numerical simulations are performed in order to examine the effects of local site conditions in the dynamic response of tailings dams. Imposing dynamic loading via characteristic pulses and real earthquake records, the most commonly used types of construction methods are studied at their final stage. Emphasis is given on the special characteristics of the ground motion, while the material nonlinearity of both soil and tailings is taken into account by an equivalent-linear procedure. The results obtained indicate that local site conditions may have a significant impact on the seismic response of a tailings dam.

Jan 1, 2005

By Krzysztof Filek, Anindya Sinha, Bernard Nowak

Taking into account the possibilities of condensation of water vapour contained in air during its flow through a series of spot coolers as well as formation of eventual fog, a mathematical model of dynamic temperature, specific humidity and degree of fogging of cooled air in underground mining galleries with direct ventilation is developed. In the gallery, there situated various heat and moisture sources both of distributive and of concentrated types. The model is represented by three partial differential equations of first order. The cases of cooling with full as well as with partial air stream flowing through the gallery are distinguished. Owing to the fact that in practical designing, more important is the knowledge of the variation process of temperature, specific humidity and fogging of cooled mine air at steady state conditions, the model is modified to a set of three nonlinear ordinary differential equations. Based on the presented algorithm, the obtained set of ordinary differential equations is numerically solved which enables to: • specify the distribution of temperature, specific humidity, relative humidity and degree of fogging of cooled air in mining galleries; • determine the cooling powers of air coolers for their known locations; • indicate the locations of the coolers of known cooling powers. Exemplary calculations of temperature and relative humidity of cooled air are presented graphically in a number of diagrams.

Jan 1, 1997

By H. Peter Knudsen

Karst hosted lignite deposits are characterized by variable thickness of lignite that was deposited in depressions in the karst topography and by the variable extent and shape of the lignite pods. Since the lignite to be mined will feed a mine mouth generating plant, an extremely important criteria in the mine plan is to assure continuous feed to the plant. The variability in both the extent of the pods and the thickness of the lignite within the pods must be taken into account in any mine design in order to quantify the risk that an area being developed will have enough lignite to feed the plant for the specified period. Indicator kriging was used to create a model of lignite thickness of the deposit. Pod boundaries were determined from the indicator kriging model by two methods. First, contour maps showing the probability that the lignite is above a minimum mining thickness were prepared. Using these maps the mine planning engineer can determine either conservative or optimistic boundaries. The second method recognized that the most costly error that can be made in the mine plan is to run out of lignite. Thus, a loss function was determined from the costs of overestimation and underestimation. Using this function, the probability that minimizes the risks of overestimation versus underestimation was calculated.

Jan 1, 1989