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By G. T. Lineberry, R. Q. Honaker

Coal extraction typically results in the recovery of pure rock that ranges from small to very large quantities depending on seam thickness and other characteristics. The removal of pure rock may allow the recovery of three times the amount in middling coal particles, which has significant economical benefits. In an industrial example, a 150% increase in revenue was realized from deshaling a low-ash, run-of-mine coal and blending with a processed clean coal product. Deshaling is the process of removing pure rock from coal, which normally involves a high-density separation in a gravity-based process. The removal of the relatively pure rock near the point of extraction has the potential to further enhance the economics of an operation due to reduced materials handling and refuse storage costs.

Jan 1, 2004

By Raj K. Rajamani, Poly K. Songfack

The slurry transport within the ball mill greatly influences the mill holdup, residence time, breakage rate, and hence the power draw and the particle size distribution of the mill product. However, residence-time distribution and holdup in industrial mills could not be predicted a priori. Indeed, it is impossible to determine the slurry loading in continuously operating mills by direct measurement, especially in industrial mills. In this paper, the slurry transport problem is solved using the principles of fluid mechanics. First, the motion of the ball charge and its expansion are predicted by a technique called discrete element method. Then the slurry flow through the porous ball charge is tackled with a fluid-flow technique called the marker and cell method. This may be the only numerical technique capable of tracking the slurry- free surface as it fluctuates with the motion of the ball charge. The result is a prediction of the slurry profile in both the radial and axial directions. Hence, it leads to the detailed description of slurry mass and ball charge within the mill. The model predictions are verified with pilot-scale experimental work. This novel approach based on the physics of fluid flow is devoid of any empiricism. It is shown that the holdup of industrial mills at a given feed percent solids can be predicted successfully.

Jan 1, 1995

During the past decade, international mining companies have descended on South America. Countries like Chile, Brazil and Peru have seen billions of dollars in exploration and development funding turn their once meager mineral industries into mining giants that have become the envy of the world. Part of this outpouring of foreign investment in those countries has been because each has privatized its state-owned mining companies and has liberalized its foreign investment laws. In addition, they have rewritten their mining codes to encourage minerals development and passed new tax laws that have made natural resource development more attractive. Now these same international mining companies are turning their attention to Argentina. This a country that, like Chile, Brazil and Peru, has a wealth of largely un- tapped mineral resources. And Argentina wants its share of the foreign investment that its neighbors have enjoyed. With that in mind, ministers of Argentina's natural resource agencies came to Denver, CO to meet with mining executives and pitch their country's mining industry. The meeting, attended by about 200 people, was sponsored by the US Trade and Development Agency and organized by the World Trade Center Denver. Others involved were the Colorado Mining Association, the Colorado International Trade Office and the Secretariat of Industry, Commerce and Mining of Argentina. The following is a summary of a report on Argentina's mining industry. It was prepared by Anderson & Schwab Management Consultants and distributed to attendees as part of the meeting's program.

Jan 1, 1998

By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risks associated with the design of mine waste-management facilities. These experiences show that the technical and managerial challenges of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur in developed and developing countries is indeed re¬markable and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailings storage facilities are, in many cases, more demanding than those of conventional water dams because seepage of fluids that contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 2000

By Heribert F. Broicher

As of 1998 German companies have been engaged in research and development of LIF analyzers for rock identification, i.e. for the fingerprinting of rock by the analysis of laser-induced fluorescence (LIF). Test work in Germany, Sweden and South Africa showed the potential of this new technique, which operates online and in realtime (1). In 2003 the Finnish company IMA Engineering Ltd Oy commenced building and marketing LIF analyzers under the trade name OreSpex. Today, one OreSpex analyzer has been installed in the Kiruna Mine, Sweden to check the phosphorus content of train loads. In 2004 a second OreSpex analyzer was built for dilution control in the Argyle Diamond mine, Australia. In 2005 another LIF analyzer will be used for test work in various mines in the US. The principles of the technology and status of ongoing work are presented.

Jan 1, 2005

By E. Bane Kroeger

Plane failure in rock and soil slopes is usually caused by the intersection of a discontinuity plane with a slope face. Normally, these discontinuities are weaker than the surrounding intact rock and provide a surface along which movement can occur. The discontinuities are typically analyzed to determine the stability of a particular slope. One problem that arises when evaluating the stability of a planar feature is that the method for planar analysis is two-dimensional and has difficulty dealing with planes that are oblique to the slope face. Several researchers have stated in the past that planar failures are a special case of wedge failure. Wedge failures occur when two planar discontinuities intersect in an unfavorable manner. Sliding can occur along the intersection of the planes. Wedge failures are very common in rock slopes and can often be problematic. Wedge stability analysis methods are typically three-dimensional and can analyze planar features that are very oblique to the slope face. Wedge failure analysis can also be used to determine the stability of planar features with good success. One advantage to using wedge analysis over plane analysis is that a tension crack can be both non-vertical and oblique to the slope face in the wedge analysis. This allows the engineer to more closely match field conditions. It also negates the need for the engineer to have two separate software packages to analyze a single slope, saving both time and money.

Jan 1, 2002

By G. L. Bloomsburg, E. G. Zahl

INTRODUCTION During the past decade, disposal of mine and mill waste material has become an increasingly important issue. Problems of structural stability and seepage effects on stability have been well addressed, and significant technological advances have been achieved [(1-4)]. The primary problem currently facing industry in the waste disposal area is environmental protection. The greatest environmental concern is over the amount of seepage or leachate entering the ground or surface water systems. Methods to determine the quantity of water seeping from a tailings pond have also been covered in the literature [(5-23)]. However, much further work is necessary to fully implement these techniques to evaluate tailings pond performance and accurately predict the various influences of disposal management on seepage from mill tailings. This study is an effort to develop those necessary techniques. The partially saturated method of analysis which is discussed here is applicable to most situations involving seepage from waste piles. In a conventional type of tailings pond, a slime layer is ordinarily built up under the ponded area. This material will consolidate slowly from capillary pressures and the weight of material deposited above it. In situations where this consolidation results in a slime layer of lower permeability than the native foundation soil, a partially saturated flow condition will usually exist in the native soil. This will result in a smaller quantity of water entering the ground-water system than would be predicted by saturated flow analysis. The finite-element program used in this study was originally developed by Neuman [(17)] and is called UNSAT2. The program will analyze problems of saturated or unsaturated, steady or nonsteady flow and can be used with a variety of boundary conditions such as constant flux, constant pressure, maximum flux, minimum pressure, and with infiltration, evaporation, and seepage surfaces. The maximum conditions are controlled by exterior factors such as atmospheric conditions; but the actual flow in the porous media is determined by properties of the porous media. In this test, the computer code was used

Jan 1, 1980

By S. G. Malghan, W. H. Moyer

In reference to the section "Excess pyrite," the author discusses difficulties in separating chalcopyrite from pyrite. A technique does exist, and has been used commercially, for the flotation, separation, and recovery, if desired, of both chalcopyrite and pyrite. The method was described in Mining Engineering, March 1966, "An Improved Flotation Method for Cornwall Sulfides." While it was not used on a porphyry copper ore, it was used on a chalcopyrite- pyrite-containing ore and might well have application. Both sulfides, chalcopyrite and pyrite, were floated simultaneously using xanthate as a collector and MIBC frother to produce a cleaned sulfide product. This concentrate was then thickened and conditioned at high solids with aeration and lime to a pH above 12.0 for a period of 1.5 to 2 hr. A supplemental suppressant, such as cyanide, could be used if necessary to sharpen the subsequent separation; however, it was not required at Cornwall. The conditioned sulfides were floated with two stages of cleaning to produce a high- grade chalcopyrite froth product and a pyrite sink product barren in copper. The separation at Cornwall gave a 28.6% Cu grade chalcopyrite product and a pyrite analyzing 0.06% Cu. A desliming step on the raw ore initially used at Cornwall for a period of time was later discontinued. Advantages to be found in using a strong sulfide collector, such as a xanthate, is the rapid flotation it induces and, generally, an ability to float at a coarser grind. A following regrind circuit could be used to give maximum liberation and produce a clean sulfide concentration. The "differential" separation is concerned primarily with grade and with assuring a barren pyrite for maximum recovery.

Jan 1, 1987

By J. A. Finch, G. Labonté

The behavior of four different redox sensing electrodes (gold spiral, black platinum, chalcopyrite, and galena) during roughing and cleaning flotation is examined and related to the flotation response. The results indicate that the solution potential (as sensed by the black platinum electrode) is different from that of the pulp potential (gold spiral) and is only weakly related to the flotation response. On the other hand, the potentials exhibited by the gold spiral and the two mineral electrodes are related to the flotation response. The transient responses of the gold and mineral electrodes during the addition of flotation modifiers could indicate the conditioning time required to achieve flotation or depression of selected minerals.

Jan 1, 1991

Mineral sands mining for ilmenite, rutile, and zircon will disturb over 2,500 ha of prime agricultural farmland in Virginia and North Carolina (USA) over the next 20 years. Mining of the Virginia deposit was initiated in 1997 and approximately 750 ha have been disturbed to date with approximately 150 ha reclaimed to support a mix of agricultural post-mining land uses. While considerable university research and corporate effort were devoted to developing environmental management systems and reclamation protocols for these lands, specific indicators of sustainability and restoration success were lacking. By 2003, it became apparent to the mining operator (Iluka Resources), local land-owners/farmers, local government, and the regulatory authority that testable indicators of reclamation success were essential for long-term sustainability. Virginia Tech worked cooperatively with all stakeholders to review the pre-existing research base and to propose reasonable expectations of post-mining soil productivity levels. The state regulatory authority reinforced its position on a number of associated issues including necessity of topsoil return and specific comparative crop yield targets. Virginia Tech, Iluka Resources, and a local leaseholder (Carraway-Winn family) agreed to jointly manage a 45-ha research demonstration farm where the effects of alternative soil reconstruction practices are being rigorously monitored for both row crops (corn and wheat) and forage production. All mined land crop yields are also compared to an adjacent undisturbed exceptional quality prime farmland soil. Corn and wheat yields in 2005 and 2006 were significantly above county average yields (regulatory target level) and approximately 75% of undisturbed adjacent prime farmlands. This cooperative effort allows all clientele groups to objectively assess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry.

Jan 1, 2007

By A. F. Klebanov, K. N. Trubetskoy, M. Yu Khoudine, V. L. Postnikov

The information system of monitoring of mine receive layouts is being created In the "ROSUGOL" Company for the prompt analysis of the state-of-the-art of mining operations at under- ground and open cast mines of the Company, rapid and effective decision-making and elaboration of recommendations on the basic directions of enterprise development. The data bank storing the digital mapping and attributive information describing the actual background of mining operations at the enterprises of the Company is the core of the system. The Oracle database management system and the ARC1 INFO geographic information system have been chosen as basic software packages for the Project realisation. The updating of the information will be performed on a regular basis via the transmission of actual digital data on under- ground and open cast mine layouts In ARCIINFO conversion to the central office of the "ROSUGOL" in Moscow. Centralised storage of digital mapping and attributive data, database administration and navigation is effected with the Oracle software package. Access to the data in the operation mode with an interactive display map will be effected with the use of the local computer net of the "ROSUGOL."

Jan 1, 1996

By Jake Coibion, Elmira Riahi, Dominic Reda, Walter Klary, Vojtech Gall

Progressive Design-Build is becoming a more common delivery method in the tunneling industry. This approach allows the Owner to select a design-builder primarily based on qualification instead of lowest price. The delivery method promotes flexibility and collaboration at all levels from the initial design stage through construction. Using the example of the Atlanta Airport Plane Train Tunnel West Extension, value-added risk management was added during the initial design phase with an independent reviewer. This paper presents the independent reviewer transitioning from constructability review in the very early stages of design to independent design verification to on-site supervision during construction.

Jun 13, 2023

By James R. Fahy, Lawrence A. Hansen, J. David Deatherage

A laboratory testing program was con- ducted to investigate the shear strength along specific soil-liner interfaces for five types of liners of varying thicknesses. Results indicated a bilinear relationship between shear stress and applied normal stresses ranging from 276 to 1000 pKa (40 to 145 psi). Friction angles along the soil- liner interface below the break point normal stress (7.5 to 19 degrees) were lower than those recorded above the break point normal stress (14.5 to 39 degrees ).

Jan 1, 1987

By W. Z. “Ben” Wu

The investigation provides a method of efficiency evaluation among several kinds of tools employed to cut different types of rocks. A ballistic test stand incorporated with a modified Hopkinson bar was used to simulate a percussive drilling tool. An Apple IIe microcomputer was employed for high speed data acquisition and numerical analysis. A newly developed method for remote monitoring the rock-tool interaction, including contact force, bit penetration and energy transmission,is presented in the paper. Theoretical predictions and experimental results appear in faily good agreement

Jan 1, 1986

By Samuel B. Romberger

During the formation of most epithermal precious metal deposits geochemical changes can be characterized by the introduction of large amounts of silica, minor amounts of sulfur, and trace quantities of gold, silver, and other metals. During the same process, large amounts of alkalis and alkaline earth elements, such as sodium and calcium, and sometimes aluminum are removed from the rocks. In deposits hosted by carbonate sedimentary rocks large amounts of carbonate may be removed before or during the silicification process. Small amounts of iron may be introduced by the mineralizing solutions, however, in most epithermal deposits this may be a relatively immobile component and is locally derived. The results of these changes are deposits consisting of up to 90 to 95 percent silica as quartz veins, breccias, silicified host rocks, and jasperoids containing a few percent sulfides, mostly pyrite, and a few parts per million gold and silver. Other minerals commonly but not always present are barite, arsenic, antimony, or mercury sulfides, and tellurides. Often gold shows a spatial, and therefore an apparent genetic, relationship to pyrite in primary ores. Alteration and gangue assemblages sometimes include sericite and/or adularia, and parts of the deposits may contain alunite and/or clay minerals. Even though the value of these deposits usually lies in their gold content, silver is usually present in larger quantities than gold (Romberger, 1990). Based on these general characteristics observed in a large number of epithermal deposits, together with processes occurring in active geothermal areas to which they are often genetically linked (Henley, 1985), a model is proposed whereby deposition occurs along a subhorizontal zone separating environments of contrasting chemistries. The upper environment is characterized by oxygenated acid waters and the deeper environment by a reducing near neutral aqueous system. The model describes the chemical changes occurring as a result of mixing and/or boiling within this zone. It builds upon the physical models proposed by Romberger (1988a) for disseminated gold deposits and Bonham (1988; 1989) for volcanic rockhosted deposits.

Jan 1, 1990

By C. Strachan

This paper presents an evaluation of the tailings dam incidents included in the 1994 US Committee on Large Dams (USCOLD) Committee on Tailings Dams report. Also, comparisons are made to water storage dam incidents from USCOLD reports, as well as to more recent tailings dam incidents. The evaluation results show that tailings dam incidents result from a number of factors, including overtopping, static and seismic instability, seepage and internal erosion, and foundation conditions. The results also show that no particular type of tailings dam or operational condition is more susceptible to incidents. In addition, the results confirm that tailings dams should be located, designed, operated and reclaimed with a thorough knowledge of site conditions, mill operation, site monitoring and tailings characteristics.

Jan 1, 2002

By Jiqing Zhang, Jon C. Yingling, Andrzej M. Wala, Richard Ray

The purpose of this paper is to present how Computational Fluid Dynamics (CFD) simulations can be used to study the flow across the main airways of a mine ventilation system. in particular, the flow through the transition zone between the upcast shaft and main fan ductwork was investigated. These studies consider potential design modifications of this transition zone to reduce the energy cost. Although CFD has many advantages, it does not completely eliminate the need for experiments, which are still needed to validate numerical solutions. For this reason, data collected during actual mine tests and CFD simulations are compared in this pa- per. This comparison allows a better understanding of the flow phenomena. Moreover, once the numerical solutions have been validated, CFD can be used with better confidence to predict the effect of changes in ductwork configurations on energy losses. CFD reduces the number and cost of tedious experiments, while enabling a broader scope of design comparisons.

Jan 1, 1997

By Roland Hoet

Mine operators, conveyor system designers, consultants, and manufacturers have had opportunities over the past decade to utilize various actively controlled technologies to drive complex underground conveyor systems. These technologies included several electrical drive solutions, mechanical drive solutions, and hydromechanical (fluid coupling) drive solutions. All of these technologies have their inherent advantages and disadvantages, and only after several years of operation can mine operators fairly evaluate the overall benefits (short term performance and cost vs. longer term operational and maintenance costs) of any particular drive. Far too often in today's world, decisions for new equipment are made with inadequate regard to issues concerning serviceability and maintainability. Many of the newer electrical technologies (primarily AC variable speed drives) which have been used in recent years were selected based on the perceived desirable benefit from variable speed operation. This technology, however, which differs sign8cantly between various manufacturers, is in a constant state of evolution which puts into question the manufacturers' ability for long-term product support. In addition, various forms of this technology have also generated some undesirable operational issues, including reduced motor life, harmonics for the power system, and mine communications problems. This technology is also extremely current-limited, which results in problems handling overload conditions, a frequent occurrence often resulting from a decline in the coal recovery rate (conveying more rock than coal). The fluid coupling, however, is based on a technology which has been used successfully in underground conveyor applications for decades. Although the base hydrodynamic technology is well proven and has inherently beneficial characteristics on conveyor applications, Voith has continuously improved on this technology to meet the increasing demands of today's challenging conveyor haulage systems. Recognizing a need in the market for a reliable, actively controlled drive system, Voith Turbo began development in 1996 of a new, actively controlled coupling which was targeted specifically for the higher powered, complex underground conveyors. Voith introduced the new TPKL Fill Controlled coupling product to the market in 1997, and the first two applications for this new technology were on multiple drive mpper booster applications on longwall panel conveyors. Since the successful startup of these two conveyor systems in 1998, Voith has supplied over 200 TPKL couplings to the mining industry worldwide, with over 150 in US coal mining applications alone. This paper will provide an overview of the TPKL's capabilities, performance, and reliability based on the TPKL's impressive installation base and operational history.

Jan 1, 2004

By W. M. Aubrey

Cobbing, as used in this; paper, refers to coarse dry magnetics separation. It is applicable when, by its practice, plant cost can be reduced or the value of its products increased by the removal of a barren or lean reject or a high grade final product. This paper attempts to describe cobbing as it is now being practiced, and also the problems that are of concern to the operator and design engineer. In preparation, 16 plants were contacted, all of which were very cooperative with their time and data.

Jan 1, 1958

By J. den Drijver, M. Opahle, R. Inderst

Safety reasons render necessary the advanced calculation of the amount of methane degassing from a longwall in the scope of the ventilation planning of mines. Today empirical methods, which are based on observations of operational procedures, are used for the calculation of the amount of methane. Despite of constant improvement those calculations are not always sufficient. In particular calculations which are based on operational facts but not proved by experience are not reliable. Most of all these calculation procedures lack physical-analytical descriptions of the procedure itself, presenting only the effects on important parameters such as the distance between seams in the roof or floor or gas pressure. Tschersich [Tschersich 961 developed an analytical model for an advanced calculation by analysing the degassing of seams in the roof and floor and the physical parameters of gasflow. This model might correct the lacks of existing procedures and improve the precision and reliability of additional calculations. The model simulates the emission record in seams of the roof and the floor. It takes into account not only a multitude of parameters such as the distance to adjacent seams and gas pressure but also the depth of seams, gas content, rank of carbonification, rock temperature, face advance rate, initial and succeeding mining and the face length. In order to comprehend and to verify those correlations we extended the model of Tschersich and programmed this enlarged model using the computer language C++. Aim of this research is to guarantee a much higher accuracy in calculating methane emission caused by mining. The improved planning is expected to result in more safety and better prevention of high methane con- tent in ventilation as well as in a better use of the capacity of the mining equipment. The application [Drijver, lnderst 961 of the ex- tended model will also be very useful in the course of research projects as it allows computer simulation, i.e. in-situ research can be extensively limited or even replaced.

Jan 1, 1997