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By Nico Bezuidenhout, André M. van Niekerk, Jan J. G. Vermaak

This paper documents empirical evaluations of geochemical data that was recorded during a seven year pilot scale experiment. The experiment was aimed at assessing the effectiveness of natural soil covers for rehabilitation of coal discard facilities. Ten test cells were constructed using different natural soil cover materials and configurations. Results of the evaluation indicate that, although a pH breakthrough was not recorded for the single layer soil cover cells as was the case with the uncovered cells, single soil covers were not effective in preventing ARD oxidation processes. Multi layered soil covers were found to be able to create anaerobic conditions leading to a reduction in ARD oxidation processes and an improvement in leachate quality.

Jan 1, 2000

By Klaus Rabensteiner, Klaus Chmelina

"INTRODUCTION Urban tunneling is often related with special geotechnical risks. Typical causes are difficult (hydro)geological conditions, a very low overburden and the presence of critical and vulnerable (infra)structures in the influence zone of the construction (e.g. existing tunnels, roads and pavements, sewer pipes, gas and power lines, landmarked buildings, historic monuments). To manage these risks appropriately, an early detection and warning of unexpected behavior of the affected geotechnical objects ground and tunnel, as well as existing structures are mandatory. To accomplish this, the design and execution of a dense geotechnical monitoring program is of high importance. In more detail, this means specifying and performing a systematic and continuous acquisition, processing and analysis of monitoring data to support decision making. In recent years the development of new automatic sensors and (wireless) data transfer techniques and the general trend towards an automatic acquisition of monitoring data has led to an enormous increase of data production frequencies and volumes. In order to handle this data explosion efficiently, information systems and geo-databases have been developed and used successfully in many projects. They represent IT tools that support the different tasks of a given geotechnical monitoring program including data acquisition, transfer, check, processing, backup, analysis, distribution, reporting and, last but not least, alarming. Meanwhile, some tools already have developed the capability to connect to other theme-specific databases used in the project and, thus, serve as a central data management system for all kind of digital data produced. This makes possible the implementation of further useful functions and services supporting tunneling tasks such as machine control, tunnel simulation, geological prediction, process optimization, etc. where data from different engineering disciplines must be combined and processed in an integrated way. In the following chapters our aim is to describe how monitoring data management, geotechnical monitoring, alarming and reporting are organized and technically implemented at the metro project Cityringen in Copenhagen (Denmark). We want to highlight the specific role and tasks of the used tunnel information system in the project, and particularly inform on the most relevant challenges."

Jan 1, 2016

By James C. Franklin

Companies are constantly searching for more effective methods of controlling and reducing costs. In recent years increased emphasis has been placed on cost reporting to the middle manager and down to the first-line foreman because this is the place where the money is really spent. Traditionally, operations management has been relegated to using cost systems designed by financial management for the use of financial management. They reflect the machinery necessary to produce profit and loss statements, and so-called cost reports emanating from these systems frequently have a heavy orientation toward product costing rather than the cost that an individual manager or foreman actually controls. In addition to direct operating costs by function or product type, they often include overhead allocations from local operations as well as from the home office. This type of full-absorption costing has many worthwhile uses but is of little or no use to operations management for cost control purposes. It is particularly discouraging to many supervisors because it includes so many categories of cost over which they have little or no control. It is for this reason that modern, aggressively managed companies are increasingly moving in the direction of responsibility cost reporting. It is the objective of responsibility cost reporting to report only direct operating costs over which the individual manager or foreman has complete control, thus facilitating cost control by fixing responsibility for cost.

Jan 1, 1979

By S. Atak, G. Bulut

The xanthate adsorption mechanism on pyrite was investigated with an emphasis on solubility studies. Additionally, adsorption studies, Eh and infrared spectrophotometer measurements were performed. Pyrite floats at pH levels between 3 and 6 using ethyl and amyl xanthates with a maximum at pH 4. The solubility of pyrite in the absence and presence of xanthate was investigated in detail with respect to pH and conditioning time. Experimental results showed that the solubility of pyrite increases from 60 to 120 ppm (10-3 to 2x10-3 mol/ L) in the presence of xanthate at pH 3. Fourier transform infrared (FTIR) spectra of ferric xanthate, dixanthogen and pyrite conditioned with xanthate indicated that dixanthogen is the only species that can be determined on the pyrite surface. Adsorption tests showed that the highest level of xanthate adsorption was in the acidic range; yet higher adsorption densities were detected in neutral solutions compared to alkaline conditions. Electrochemical data suggest that the doubling of the iron concentration is due to the reduction of ferric ion to ferrous by xanthate while xanthate is oxidized to dixanthogen. Dixanthogen formation together with the hydrophobic iron hydroxy-xanthate complex on the surface is proposed to be responsible for pyrite flotation. Key words: Flotation, Pyrite, Adsorption, Xanthate, Dixanthogen

Jan 1, 2003

By Virgil R. Huff, Ihor Havryluk

P. T. Pacific Nikkel Indonesia (PTPNI) was incorporated in Jakarta, Indonesia in February, 1969 by a group of Dutch and North American companies. At the same time, a Contract of Work with the Government of the Republic of Indonesia was signed, granting Pacific Nikkel all the necessary licenses and permits to explore and develop all nonradioactive minerals in two separate areas in Irian Jaya, eastern Indonesia. Nickel mineralization occurrences were confirmed by Dutch geologists in the two areas in 1952 and 1955, however, detailed exploration began in June 1969 after the Contract of Work was signed. Since that time, numerous studies and investigations have been conducted to determine the feasibility of producing metallic nickel in Irian Jaya. Four engineering studies, two bulk sample tests, an oceanographic survey, and a preliminary site investigation indicated that construction and operation of a nominal 100 million pounds per year metallic nickel plant on Gag Island were technically feasible. The fourfold increase in the price of oil in late 1973 without a corresponding adjustment in the price of nickel necessitated a reevaluation of the project, the results of which showed that the project required other conditions to be viable. Subsequently, analysis of: the future projected nickel supply-demand and cost-price relationships, the economics of treating a higher grade feed, and participation by the Government of Indonesia, indicate that the project will be viable. Therefore, planning of the Gag Island Nickel Laterite Project is continuing with the objective of commencing production to supply the market in the 1983-1984 time period.

Jan 1, 1979

By Ernest Koenigsberg

In 1961 Lerchs and Grossman presented a method, based on graph theory, to determine the optimum ultimate pit limits for an open-cast mine. At the same time they demonstrated a dynamic programming algorithm for the optimum pit limits for a two-dimensional open-cast mine. Since then many methods for determining optimum limits for three-dimensional mines have been programed, and even more have been reported in the literature. The methods include computer "simulation" of the manual methods used by engineers, the development of sets of conic sections and fitting to exclude overlap, integer linear programming (and its equivalent network flow model), and dynamic programming. Many of the methods do not guarantee optimal solutions but seem to satisfy the user. Other reported methods have never been applied, partly because they did not yield optimal solutions. We have developed a three-dimensional dynamic programming algorithm which requires a single pass through the data. Large problems can be solved on a small computer because only a small part of the data is required at any time. In this paper we will review the state of the art and to demonstrate the connection between linear programming (and network flow) models and the dynamic programming method.

Jan 1, 1982

By Ning Liu, Xuming Wang, Yongqiang Lu, Jan D. Miller

Bench-scale flotation experiments have been conducted to study the effect of nonionic polyethylene oxide (PEO) polymer surfactants on the flotation of Florida phosphate rock. It has been found that PEOs having a molecular weight from 1,200 to 8,000 are effective. Flotation results demonstrate that the addition of nonionic PEO has a favorable effect on phosphate flotation, especially on the flotation of coarse phosphate feed. At about the same collector level, phosphate recovery can be improved by 10-30% with PEO addition. The surface chemistry of phosphate flotation using the fatty acid/fuel oil/PEO system has also been studied to better understand the phenomena involved. The increase in phosphate recovery with PEO addition has been attributed to improved dispersion of fatty acid, which leads to better froth stability and a more hydrophobic surface state.

Jan 1, 1999

By Z. Zhang, R. G. Reddy

The viscosities of industrial lead slags of varying compositions were measured as a junction of temperature using a Brookfield viscometer. Based on the experimental data obtained from this study and based on other investigations reported in the literature, an expression was developed to correlate the viscosities of industrial lead silicate slags as a function of composition and temperature. The effect of each individual slag component on the variation of the slag viscosity is identified. The composition dependency of lead silicate slag viscosity is discussed. The calculated results using this viscosity expression are in good agreement with the measured data. Key words: Viscosity, Lead silicate slags

Jan 1, 2003

By Frédéric Flament, Daniel Hodouin, Claude Bazin

A control strategy is proposed to meet the following specifications of flotation control: minimize the variations of concentrate and tails grades and recovery while limiting the amplitude of variations of the manipulated variables. The strategy consists of determining future control actions which optimize a performance criterion over a limited time horizon. The desired dynamic behaviour of the controlled flotation plant is specified using reference models. The strategy is tested on a 2-computer plant simulator working in an environment which emulates the industrial conditions.

Jan 1, 1993

By K. Wangerud, B. S. Caruso

A water-balance model with deterministic and stochastic components was developed and used for the Gilt Edge Mine Superfund Site in South Dakota. The model was developed to evaluate the risks of contaminated runoff discharging to surface waters based on assumed water treatment plant (WTP) rates, for different remedial alternatives. The objectives of the modeling were to use a stochastic approach for the analysis of precipitation based on historic records and to make a probabilistic estimation of annual and monthly runoff from disturbed/mining activity areas that now require, or will need, treatment at the WTP, water storage and changes in a major pit, and risk of contaminated water bypass of the WTP to a downstream drainage. Subareas/source areas generating contaminated runoff requiring treatment were delineated. A simple water-balance model was used based on precipitation inputs and evapotranspiration and groundwater losses. Annual and monthly precipitation records for Lead, South Dakota, were used to estimate precipitation at the mine site. A lognormal distribution was estimated for monthly precipitation. The stochastic software package/ Excel add-in "@Risk" was used to generate random monthly precipitation values using a Monte Carlo method based on the distributions. The average annual and monthly distribution of pan and lake evaporation and of groundwater losses were also estimated for the site. Stochastic outputs from the model for the end of each month and year included contaminated runoff requiring treatment, water storage in mine pits and the risk of WTP bypass given different assumed WTP rates. The probability of the time required to dewater the pits was also modeled.

Jan 1, 2003

By V. Scovazzo

Cost-effective underground mine configurations have been designed in highly fractured rock masses where the stone possesses a high material strength. A limestone mine in the eastern United States is used to demonstrate procedures for the geotechnical design of one such operation. The mine discussed is located in both limbs and the axis of a recumbent fold that fractured the rock mass. In a highly fractured rock mass, where the host rock has high strength, a design can be developed to alleviate intact rock failure. This is possible because in most cases as the stress levels needed for intact failures are approached, the stresses are quickly dissipated due to movement along discontinuities, which represent planes of weakness. As a result most underground failures in highly fractured rock are due to sliding or toppling. Even when intact rock fails in a highly fractured rock mass, it is the movement along an existing joint or other weakness plane that often initiates or causes this failure. It is therefore important to obtain the characteristics of weakness planes that are the discontinuities within the mass. The required information on weakness planes, geology, and strength of materials is discussed and recommendations for obtaining this information are presented. A discussion is provided on failure modes and the use of developed information for their evaluation. The impact on geotechnical design is demonstrated through pillar sizing procedures; however, this approach can also be applied to mine roof and pillar foundations.

Jan 1, 2004

By J. J. Daniels

Advances in borehole geophysical research for mineral assaying and remote detection of mineralization away from the borehole are cited. Nuclear activation measurement research has provided accurate in situ assays of economic metals with neutron-gamma activation, using a high resolution intrinsic-germanium detector. Although nuclear activation analysis is the present "best hope" for obtaining in situ assays for some elements, gamma-gamma and magnetic susceptibility measurements can provide accurate assays for lead-zinc and magnetite, respectively. Borehole optical spectroscopy and X-ray fluorescence are being investigated as possible in situ assaying techniques for some minerals. More laboratory and field calibration research is needed before non-linear complex resistivity (NLCR) can be routinely used as a quantitative assaying tool. Field tests have shown that variations in the local geologic environment can affect the quantitative accuracy of assay values from downhole NLCR measurements. Deeply penetrating borehole geophysical methods are increasingly being used for mineral exploration as drilling costs and exploration have increased. Borehole electrical measurements have been shown to be useful for detecting conductive ore bodies that are not intersected by a drill hole. Hole-to-surface resistivity and surface-to-hole time-domain electromagnetics are demonstrated to be particularly effective for defining mineralized zones in a massive sulfide environment. Borehole gravity meters and three-component magnetometers have been developed and should prove useful for defining geologic anomalies away from the drill hole.

Jan 1, 1987

By Winfield G. Wright, Philip L. Verplanck, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

The upper Animas River watershed is affected by metal-rich drainage from abandoned mines and by natural weathering of mineralized bedrock. To investigate the importance of natural metal sources, surface waters were sampled in a minimally mined but intensely altered area of the watershed. Water chemistry was strongly controlled by the degree of bedrock alteration. Propylitically altered rocks, which contain calcite, produced neutral waters with low metal concentrations, whereas quartz-sericite-pyrite alteration was characterized by acid-sulfate type waters with high metal concentrations. A mass-balance approach was used to estimate natural metal sources, which accounted for 56-905 of the dissolved metal load discharging from the study area

Jan 1, 2000

By Lijun Xu, Ragula Bhaskar

The transport of dust particles from a turbulent air stream on to the surface of a mine entry is mainly due to the effect of diffusion, sedimentation and inertial impaction. While the literature in aerosol science contains many references on particle deposition, most studies apply to smooth surfaces in small, short tubes. The deposition data from those experiments may not be applicable to deposition in mine airways that have large areas of rough surfaces and extend several thousand meters. This paper describes the mechanisms of mine dust transportation and deposition, specifically, by estimating the turbulent deposition velocity for coal dust in mine airways. Data from in-mine experiments on ambient dust concentration and dust deposition along a straight entry were used. A statistical model for dimensionless turbulent deposition velocity was developed, and compared with the models developed by other researchers. The model shows that the distance from the dust source is an important factor in the turbulent deposition of mine dust.

Jan 1, 1995

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

"The Analysis of Retreat Mining Pillar Stability (ARMPS) program was developed by the National Institute for Occupational Safety and Health (NIOSH) to help the U.S. coal mining industry to design safe retreat room and pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the “abutment angle” concept in calculating the magnitude of the abutment load on pillars adjacent to a gob.In this paper, stress measurements from U.S. and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 650 ft, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 650 ft, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases.The new abutment angle equation was tested using both ARMPS2010 and LaModel for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the LaModel program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.INTRODUCTIONIn the early 1990s, the Analysis of Longwall Pillar Stability (ALPS) was introduced by Mark (1990) as a chain pillar design software and was generally accepted and used by the U.S. coal mining industry. Following the success of ALPS, the National Institute for Occupational Safety and Health (NIOSH) developed the Analysis of Retreat Mining Pillar Stability (ARMPS) program for designing retreat mining pillars using a similar approach as ALPS (Mark and Chase, 1997). The Australian mining industry also recognized the success of ALPS, and Colwell, Frith, and Mark (1999) calibrated the program to Australian conditions. The ALPS and ARMPS programs draw their strengths from the large databases that are used to calibrate them (Mark, 2009). However, following the Crandall Canyon Mine collapse in 2007, NIOSH had to reconsider the pillar design criteria used in deep-cover retreat mining (Mark, 2010). The ARMPS overburden load prediction algorithm was improved to more accurately predict the loading of narrow panels with high overburden depths by implementing the pressure arch concept, and this new version is called ARMPS2010."

Jan 1, 2019

By William W. Wellborn

Abrasives are substances both natural and synthetic that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material usually by rubbing action (as in a grinding wheel), but also by impact (pressure blasting). Facts about the discovery, early use, adaptation, and development of abrasives prior to the 20th century are few. From the sparse, earliest information that is available, it would appear that the science of abrasives began when, to fashion his tools, man began to select certain kinds of rocks in preference to others because of their peculiar properties. There is evidence that stones were sawed by some sort of grinding machine as early as 4000 BC in Egypt. The real expansion of abrasives use coincided with the beginning of metallurgy in the Middle East around 2000 BC. The earliest confirmed use of abrasives for grinding metal comes from a steel dagger found along with a sharpening stone which was dated at about 1500 BC. Natural and manufactured abrasive substances play an important role in fashioning and finishing numerous products with a wide variety of end-use applications. The mining and preparation of crude, natural abrasives for their markets and the manufacture of synthetic and other abrasive materials contribute significantly to the US economy (Table 1). In addition, just as sawing to specific dimensions enhanced the value of the Egyptian stone, the use of abrasives in fabrication of modem products, and the addition of abrasives to others, add value. GENERAL CONSIDERATIONS The most important physical properties of materials that qualify as abrasives are hardness, toughness (or rigidity), grain shape and size, character of fracture (or cleavage), and purity (or uniformity). To fabricate bonded abrasive products such as grinding wheels, additional considerations include stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one singular property is paramount for any use. For some applications extreme hardness and toughness are needed, as in diamonds for drill bits. For other uses, factors of greatest importance are hardness and ability to break down slowly and, in the process, develop fresh cutting edges when grains become worn. In garnet sandpaper, for example, highly cleavable, friable, or extremely tough grains are not desirable. For other uses, extreme hardness may be objectionable. Abrasives for dentifrices and for glass-cleaning soaps are cases in point. For the most efficient uses in more critical applications, different types of abrasives are rarely completely interchangeable. While crushed quartz and garnet are both used in sandpaper, the two abrasives are not at all interchangeable in their applications. In the final analysis, the choice of a high-grade abrasive depends upon the quality and quantity of work performed by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive, but the artificial mineral may do so much better work and do it so much faster that the ultimate cost is less. It is for this reason that artificial abrasives have largely replaced natural abrasives.

Jan 1, 1994

By J. W. Wilson, S. Nakajima, B. D. Singh

According to the Project Independence blueprint, a 270 percent increase in coal production is expected from western coal fields compared to an increase of 100 percent for the nation as a whole. Furthermore, 30 percent of the total United States coal reserves lie in the western states, which are classified as beyond the strippable limits and can be recovered only by underground methods. In view of the fact that the majority of the seams in the West are thicker than those presently mined in other parts of the country, it is important to consider the parameters that relate to mining thick seams and the factors that affect such mining systems. Apart from thick seams, a common feature of many western coal fields is the occurrence of multiple seams that lie in close proximity to one another. These multiple seam deposits present difficult mining problems that have not been encountered to any degree in other U.S. coal fields; for example, ground pressure changes in one mine level caused by mining in the other, sudden water or gas influx from the adjacent levels, the danger of spontaneous combustion in gobs and large and complex subsidence displacements on the surface. Perhaps equally important is the fact that the country can ill afford the present systems of underground mining that attain only 50 to 60 percent coal recovery. With the probability of increased thick seam mining, conservation shall be a focal point in future mine design systems. It is possible that in the future it will be forbidden to adopt the present day wasteful mining methods to ensure that coal can be conserved for future generations.

Jan 1, 1977

By Carl E. Nelson

Shallow epithermal stockworks hosted by maar eruption craters contain over ninety percent of the bulk mineable gold identified to date in the Circum-Caribbean region. Pueblo Viejo (Dominican Republic) and Santa Rosa (Panama) contain combined gold reserves of over 600 tonnes. Bulk mineable gold deposits are also being discovered in and around veins that were formerly mined underground. Bellavista, El Recio and San Martin (Costa Rica) contain combined announced gold reserves of over 50 tonnes. Representative rock suites collected at 8 bulk mineable gold deposits include 291 samples of veins and vein stockworks, hydrothermal eruption breccias, sinter, variably altered host, unaltered host, nearby intrusive rocks and basement. Analyses completed to date show that Circum-Caribbean epithermal ores are enriched in arsenic, mercury and antimony as well as gold and silver. Exploration efforts in the region naturally focus on districts with past production. However, an order of magnitude more bulk mineable gold has been discovered in shallow epithermal stockworks outside of the old bonanza vein camps. Exploration guides include basal island arc volcanic sequences, hydrothermal and hydrovolcanic (maar) eruption breccias, thinly-bedded carbonaceous maar sediments, and hot spring-related silicification and argillic alteration.

Jan 1, 1990

By S. Chander

The fundamentals of flotation are reviewed with an objective to understand the limitations in predicting the performance of a sulfide mineral flotation system and in its scale-up from laboratory studies to plant practice. The difficulties can often be traced back to complex interactions between chemical and physical parameters and nonequilibrium effects. The physical and chemical changes that occur during the long sojourn of sulfide minerals that begins with mining, continues through crushing and grinding, and ends when they emerge from the flotation cell as a concentrate, are reviewed. The benefits of new techniques that have become available in recent years to identify and estimate the amount of surface species are discussed.

Jan 1, 1999

By R. S. Sheeta, C. J. Bise

The search for a more effective means of coping with methane liberation has resulted in the expanded use of seam degasification. Its advantages are measured not only in reducing the hazards due to methane, but also in producing a marketable commodity, the gas itself. However, the success of a methane drainage system is the culmination of many complex factors, the most important being the coal seam permeability. The two most popular drainage techniques used in mining today are the vertically stimulated borehole method and the in-seam horizontal borehole method. The objective of this paper is to determine the permeability range in which the selection of the degasification technique is based primarily on equipment and economic analysis. A discussion of the equipment involved will be incorporated into examples evaluated by the Pennsylvania State University coal methane simulation model.

Jan 1, 1990