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By Bruno Bussière, Michael Aubertin, Robert P. Chapuis

Covers with capillary barrier effects (CCBE) have been used in recent years as gas barriers for the isolation of wastes, including reactive mine tailings. Capillary barrier effects help to maintain a high degree of saturation in the moisture retaining layer, which then reduces gas flux. Various factors affect the degree of saturation of the moisture retaining layer in a CCBE, such as the material water retention characteristics and layer thickness. Slope geometry can also influence the hydrogeological behaviour of a CCBE, but this factor has frequently been ignored in the past. In this paper, the authors show some results of a numerical study that illustrates the influence of slope on the behavior of capillary barriers made of different types of material. The numerical model calculations are based on an actual case of a CCBE constructed in northern Quebec. This investigation shows that the water content profile is greatly affected by the position along the slope. Thus, it is necessary to evaluate the influence of the geometry to properly establish the performance of a cover system.

Jan 1, 2000

By A. Kalogeropoulos, T. Michalakopoulos

The DEM has been used in several studies to numerically simulate the response of rocks to the cutting action with drag tools. In this research, the aim is to realistically simulate the rock material and the cutting process by controlling the grain interlocking of the numerical assembly and streamlining the calibration process while focusing on the cutting force and the failure mechanism.

Apr 1, 2023

By B. Yarar

Samples of coal from an adit in the Fording River District of British Columbia showed hydrophilic properties between depths of 0-24.5 meters and was naturally hydrphobic at higher depths. Laboratory experiments indicated that weathered samples (i.e., those mined at 0-24.5m) could be upgraded by froth flotation at pH<2 following slimes removal. The i.e.p. of samples varied regularly between pH=1.6-4.1, the weathered fractions being at the lower end of the pH scale. These values followed a pattern comparable with the flotation behavior of samples. A patchwise structure for coal surfaces determining the resultant disjoining pressure, which in turn determines flotation-non flotation relationships is postulated.

Jan 1, 1982

By Enrique Rubio Esquivel, Matías Fuentes Bustamante

The transition from open pit to underground mining represents a key strategic challenge in modern mine planning. This paper presents a multicriteria and multivariable methodology to plan such a transition, integrating technical, economic, environmental, and social considerations. The proposed framework focuses on risk reduction (de-risking) through the identification of alternative development paths, the use of stochastic simulation to model geological and technical uncertainty, and different mining strategies such as methods, production rates, sequence, etc. for ultimate underground implementation. The study summarizes the limitations of traditional planning methods—which usually treat the open pit and underground mine designs as independent processes—, also often it considers a single mining method and production rate for the underground option. Instead it is proposed an integrated approach that leverages synergies between both mining methods and scalable production rates. Also the proposed methodology incorporates the definition of critical variables (geotechnical, economic, and social, among others), the construction of multiple operational and technological transition paths, and the evaluation of each path under criteria of economic attractiveness and practical do-ability (capacity to be executed). Using simulation tools (SIMPLAN for operational performance and SIMVAL for economic evaluation), probabilistic distributions of the different path are obtained, enabling the quantification of the project’s Value at Risk (VaR). A subsequent multicriteria analysis weights the expected profitability against the feasibility of execution of each alternative, producing a decision matrix that provides a framework for evaluating the different project path. As a result, the proposed approach identifies OP→UG transition strategies that maximize business value by capturing remaining resources while minimizing financial and operational risks. Finally, strategic conclusions and recommendations for the industry are provided, emphasizing the importance of early transition planning even challenging the open pit sequencing of the latest push backs by introducing early underground operations. Future work includes strengthening the methodology—such as integrating real-time analysis and adaptive decision-making—and providing recommendations for its application in various mining operations. In summary, this paper delivers a technical and professional framework to guide mining companies on when and how to carry out a successful transition from open pit to underground mining, balancing resource recovery with financial, operational, and social security.

Feb 22, 2026

By Paul O. Knorr

The Bureau of Ocean Energy Management (BOEM), a bureau within the U.S. Department of the Interior, has responsibility over both energy and non-energy mineral development on the United States Outer Continental Shelf (OCS) under the OCS Lands Act (“OCSLA”). BOEM’s Marine Minerals Program (MMP) manages federal offshore mineral deposits through non-competitive, negotiated agreements for sand and gravel (“sand”) used in coastal restoration efforts and the competitive leasing of critical and hard economic minerals (“critical minerals”). As the steward of OCS critical minerals, BOEM MMP is responsible for understanding where critical minerals are located, identifying and understanding their environments, managing activities that affect these resources, and implementing pertinent federal policies. Fulfilling these responsibilities involves the collection and analysis of environmental, geological, and geophysical data; supporting the science needed to understand the impacts of resourcerelated authorized activities on the biological, physical, and sociocultural environments; encouraging emerging technologies that can reduce the environmental impact of activities; and communicating with stakeholders to foster an understanding of existing federal regulations and potential needs to revise the legal framework. Four U.S. federal rules in the Code of Federal Regulations (CFR) currently inform MMP’s procedures: 30 CFR 580 (prospecting for minerals), 30 CFR 581 (leasing of minerals), 30 CFR 582 (operations in the OCS related to minerals), and 30 CFR 583 (negotiated noncompetitive agreements for sand). Other federal laws and regulations are also pertinent, particularly those supporting the National Environmental Policy Act, Endangered Species Act, National Historic Preservation Act, Marine Mammal Protection Act, Coastal Zone Management Act, Clean Air Act, Federal Water Pollution Control Act, and Magnuson Stevens Fishery Conservation and Management Act.

Feb 22, 2026

By Stanley M. Moos

In reviewing available vacuum filtration equipment in this paper, several types of filters have been included which are probably not familiar to operators in the mining industry. However, it was felt that these units might be of interest in the event that an application should arise for the filtration of a product in the future that does not exist today. In addition, exposure of our industry to equipment used in other industries might have a tendency to be thought provoking and perhaps lead to the development of equipment and/or applications in our industry which do not necessarily exist at this time. Most innovations in filtration equipment have been confined to the improvement or design change of components and accessories, particularly reflecting the availability of materials of construction that have been developed. Recent developments in the application of horizontal belt filters have been innovative. The application of this unit as a substitute for or an adjunct to thickeners in a CO circuit can certainly be innovative and perhaps provide a basis for reduction in capital and operating costs in this area. For example, mill tails are generally pumped at the highest possible density that will adequately flow. Tailings ponds and dams with their attendant design requirements are based upon this estimated water volume. Availability of a much dryer, non-flowing filter cake opens up several new options for disposal. Considerable cost savings could result in the design and planning of disposal areas for containing dryer material. . No attempt has been made in this paper to provide a manual for the operation of all of the many types of equipment that are available. Rather, the paper tries to present an overview.

Jan 1, 1978

By G. L. Ploetz

The lanthanon compounds are becoming increasingly more important for ceramic and allied applications. As the supply increases and the cost decreases, further development of these interesting materials will undoubtedly lead to new applications and an increased demand. Recent improvements in separation processes have lead to high purity in the individual lanthanon oxides. This report includes short discussions on the mineralogy of the ores as raw materials, and on the separation processes required to produce the pure individual lanthanon oxides in useful quantities. To discuss the presently known applications of lanthanon oxides, this general review is divided into the following categories: A. Glasses, Glazes, and Porcelain Enamels. B. Refractories and Abrasives. C. Electronic Ceramics. D. Nuclear Ceramics.

Jan 1, 1960

By Inkap Choi

Asbestos is a broad term embracing a number of fibrous silicate minerals. These minerals look extremely fragile, yet their fibers have a tensile strength equal to that of piano wire. Chrysotile asbestos is the only mineral that can be woven into cloth, and its fibrous structure is, if anything, even more amazing than its remarkable ability to withstand heat. Because of its unique physical properties asbestos has achieved great industrial importance, and more than 3,000 current uses are known, ranging from use in the kitchen to use in space missiles. Because their minuscule fibers are eminently respirable, asbestos minerals have also found their way into the lungs of humans, where they apparently produce serious biological effects such as asbestosis and lung cancers. 1, 2,3 Because of both their usefulness and their hazardous properties, these minerals have attracted a good deal of attention from research workers during recent years. For example, the surface properties of asbestos minerals have been studied by many investigators. 4, 5, 6, 7, 8, 9 However, even for the important mineral chrysotile, the literature data are more or less conflicting. Pundsack4 measured a PZC (point of zero charge) of 10.1; Martinez and Zucker5 measured 11.8; Chwastiak reports 10.8-11.0; and Raddick measured three sepa-rate apparent PZCls at about pH 8.3, 10.0 and 10.9. More recently Trivedi8 reports 10.11. Naumann and Dresher9 have studied surface charge enhancement of chrysotile by metal ions, and describe how the mineral reacts with contaminantions. In the present paper, the mode of dissolution of magnesium and hydroxyl ion from asbestos minerals placed in water was studied by kinetic experiments involving rate at which these items leave the minerals. Also, some study was made of interaction between dissolved species.

Jan 1, 1972

By P. Mousset-Jones

The USBH Mining Systems and Ground Control Generic Research Center funded a project leading to the improved planning of airflow and refrigeration in underground mines experiencing hot working conditions. The project was broken down into approximately five phases: 1. Visiting some of the known hot mines in the U.S. and sending out a questionnaire to determine other mines which might be experiencing hot working conditions in the future. 2. Choosing two mines in which to conduct measurements to determine the insitu rock thermal conductivity and diffusivity, and comparing these values with laboratory determined values. 3. Investigating computer programs available for mine climate simulation, and testing these programs with case study examples from the two mines where the rock thermal properties were measured. 4. Considering improved ways of estimating the wetness factor and experimenting with the use of heat flux meters to more directly measure the rock heat inflow into the airstream. 5. Applying the results of these investigations to simulating the climate for future mine development and production areas at the two- mines. The project is approximately two thirds completed. At the time of writing, the insitu measurements at one of the mines are still being recorded. This paper will be describing the procedures and results of the insitu rock thermal property measurements, and give a brief description of some of the simulated results obtained for a mechanised cut and fill stope case study from the Homestake Gold Hine in South Dakota.

Jan 1, 1985

Because the Environmental Protection Agency has identified methane as a greenhouse gas, the importance of de gasification through gob wells has become more critical. It has been observed that the degree of methane emission is closely related to the geomechanical characteristics of coal bearing strata, roof, floor, and surrounding coal seams. Monthly production data from 250 gob wells were collected from the Warrior Basin in Alabama, and many interesting correlations were observed between methane production with longwall face width, face advancement rate, number of gob wells in a panel, and geologic columns. Extensive finite element analyses were performed to estimate the characteristics of the emission zone in an attempt to corroborate these findings. This paper describes an investigation for developing correlations between the geomechanical behavior of the methane emission zone with methane production.

Jan 1, 1996

By Leena Suopajärvi, Karin Käär, Marcin Szumny, Jari Joutsenvaara, Md Ariful Islam, Helmut Mischo, Georg Meissner, Ossi Kotavaara, Catalina Vrabie

This study outlines implemented tactics and results for community empowerment through participation in questionnaire surveys, educational programs, and discussion on sustainable sourcing from new critical raw materials (CRMs) projects. Utilising questionnaire surveys, including the Public Participation Geographic Information System (PPGIS), the research gathered public opinions from Estonia, Germany, Poland, and Zambia, receiving 1,068 responses. These responses addressed various social, economic, and environmental issues related to CRM projects. Feedback from educational courses with participants from over 25 nations and public events provided additional insights. The collected data and feedback offer crucial input for advancing sustainable and responsible CRM sourcing strategies in these regions.

Feb 1, 2025

By K. A. Smith, X. Cheng

Introduction The separation of minerals from complex sulfide ores by flotation requires careful control of the surface chemical behaviors of the minerals constituting the ores. When the minerals in the ore are finely disseminated, extremely fine grinding is needed to liberate the minerals. Fine grinding is not only an energy-intensive operation, but also influences the flotation behaviors of liberated minerals. Steel balls are commonly used for grinding. Galvanic interactions occur not only between sulfide minerals and grinding media but also among the different sulfide minerals themselves. The electrochemical characteristics of chalcopyrite and pyrrhotite when they are independently coupled with steel grinding media and the relevance of these characteristics to the flotation behavior of these minerals have been exten¬sively studied (Cheng and Iwasaki, 1992: Li and Iwasaki, 1992). These studies dealt with reactions in two electrode combinations, simulating mineral-grinding medium and mineral-mineral interactions. In practice, however, it is more common to involve more than one sulfide mineral. In a study of a pyrite-pyrrhotite-mild steel system, Pozzo et al. (1989) provided evidence that a mineral having an intermediate potential could behave differently, depending on the condi¬tion of galvanic contact. This investigation was undertaken to study a chalcopyrite-pyrrhotite-mild steel system to gain better in¬sight into the mechanism of multiple galvanic interactions. A three-electrode system was chosen to simulate a typical copper sulfide ore. The sulfide minerals were represented by chalcopyrite and pyrrhotite. The grinding medium was rep¬resented by mild steel. The nature of galvanic interactions involving these minerals and grinding medium in an oxygen atmosphere was investigated in a three-electrode combina¬tion, and an attempt was made to relate the laboratory flotation results of pyrrhotite-chalcopyrite ores. Possible implications to the differential flotation of complex sulfide ores are discussed. Key words: Electrochemistry, Flotation, Sulfide ores Experimental The pyrrhotite (57.74% Fe, 0.09% Cu, 4.84% Ni and 36.54% S) sample was obtained from Falconbridge Ltd.&apos;s Strathcona mine, Ontario, Canada, and the chalcopyrite (26.00% Cu, 28.57% Fe, 0.05% Ni and 31.52% S) sample came from Transvaal, South Africa. Mild steel (AISI 1020, 0.2% C) was chosen to represent grinding media. A conventional three-electrode cell was used in the elec¬trochemical measurements. The working, counter and refer¬ence electrodes were, respectively, sulfide minerals or mild steel, graphite rod and saturated calomel electrode (SCE, 0.245 V vs. standard hydrogen electrode). The exposed areas of the sulfide minerals and grinding medium electrodes were approximately the same (0.17 to 0.19 cm2). The preparation methods of working electrodes, the reagents used, the experi¬mental procedures and the instrumentation were the same as those described previously (Cheng and Iwasaki, 1992). Rest potentials of pyrrhotite, chalcopyrite and mild steel were measured individually in 0.05-M sodium sulfate solu¬tions. Combination potentials and galvanic currents of the sulfide minerals and grinding medium were measured in short-circuited two- and three-electrode systems. All poten¬tials in this study are quoted in volts with respect to the standard hydrogen electrode (SHE). To simulate the constantly abrading conditions in a ball mill, rest potentials, combination potentials and galvanic currents were also measured by rotating a porcelain ball against chalcopyrite, pyrrhotite and mild steel electrodes in

Jan 1, 2000

By Ray A. Rothrock

The in situ mining of uranium is the process whereby chemical lixiviant is injected by means of wells into, and flowed through, an ore body. The lixiviant reacts with uranium which has been previously oxidized making the uranium soluble. The solution is then brought to the surface by means of producing wells. In situ mining disturbs the ground-water quality in the immediate area. Since ground water is a natural resource used by man, care must be taken not to allow the lixiviant to escape the local mining area. Also, when the ore body is mined out, the area should be restored to as near its original state as is reasonably achievable. The return of ground-water quality to its original state can occur naturally over a long period of time or be enhanced using appropriate technological means.

Jan 1, 1981

By William H. Wiese

Anecdotal reports of high rates of congenital malformations and spontaneous abortions at the Shiprock Indian Health Service Hospital in San Juan County, New Mexico prompted an interview survey, obtaining data from families of 26 former uranium miners and 30 controls. Results supported the possibility of increased fetal wastage and congenital malformations. However, definitive conclusions were obviated by methodologic limitations in terms of selection of cases and controls and interviewing technique, as well as very low numbers and lack of statistical significance. The Council of Environmental Quality (1980) published a report which singled out San Juan County, nationally, as having an extra-ordinary high rate of congenital anomalies reported from birth certificates in the years 1973-75. San Juan County is in the northwest corner of New Mexico and includes the northeastern edge of the Navajo Indian Reservation. It has been the site of uranium mining and milling and also of coal mining (Clement Associates, 1980). While much attention has been focused on lung cancer and chronic lung disease as health hazards to uranium miners, virtually no attention has been focused upon possible reproductive effects that may result from exposure to radiation. Could these reports indicate such an additional arena of health effect either on miners or on others living in the vicinity of the mines and mills? The biologic and epidemiologic literature does not lend much support for adverse genetic outcome. The UNSCEAR report (UNSCEAR, 1977) summarizes much of the existing data. For example, on the basis of many animal studies and what has been observed in atom bomb survivers in Japan, it has been estimated that mutation rates resulting from low LET radiation to paternal germ cells would be 60 X 10-6 recessive and 20 X 10-6 dominant mutations per gamete per rad. There would be a five-fold increase in the number of recognizable abortions. The doubling dose for genetic disorders in mice is estimated at 100 rads. The assumption has been that low levels of exposure, such as might be received occupationally from uranium mines and mills or environmentally will produce reproductive effects that would defy distinction from background rates. However, the possibility can not be dismissed. In man, spermatogonia are thought to be three-fold more sensitive than in the mouse. Also, the high LET radiation from alpha particles is as much as 20-fold more effective in inducing changes in meiotic and post meiotic stages of cells, compared with low LET radiation. There is some degree of localization of alpha emitters in testicular tissue after inhalation of radon and radon daughters (Blanchard, R.L. and Moore, J.B., 1971; Pohl, E., 1964). The slopes of doseeffect curves are affected by type radiation and rate of administration. Data on such curves are poorly defined and debated as to whether there may be increased or decreased effect per unit dose at low levels of high LET radiation. Increased rates of aberrations of chromosomes in peripheral lymphocytes cultured from uranium miners have been reported (Brandom, W.F., et al., 1978). At cumulative exposures of 100 working level months (WLM) or less, a range of exposure lower than the limit of current occupational standards, the aberrations were increased more than two-fold. Our interest has led us to pursue the question of reproductive effects along three separate paths of inquiry: studies of the secondary sex ratio, cytogenetic study of human sperm, and studies of rates of congenital anomalies. I will present the thrust of our findings, most of which remain preliminary, comment on their interpretation and limitations, and indicate directions needed for future research. The secondary sex ratio is the ratio of males to females at birth. In the U.S., the ratio averages around 1.05. Ratios in blacks are somewhat lower (1.025) than in whites (1.053). For American Indians, the data are less definite. Values from Oklahoma and California are similar to whites (1.05). Southwestern tribes have, as we shall see, varying levels. The theoretical effects on sex ratio resulting from irradiation of the zygote are based on the principles of sex-linked genetics, including differential effects of lethal dominant and recessive mutations on the sex chromosomes, complicated by possible non-disjunctional events. Observations have done little to clarify, confirm or refute the theories. The sex ratio of progeny of survivers of the atomic bomb showed little change (Schull, W.J., Otake, M., and Neel, J.V., 1981). Observations in children of uranium miners having been inconsistent. Most frequently cited is a study of miners in Czechoslovakia (Müller, C., Razicka, L., and Bakstein, J., 1967). Compared with children born to miners prior to the start of mining, the sex ratios of children born after the start of mining were decreased -statistically significant after correcting for birth order. The ratios in first-born children were, before the start of mining, 1.118, and, after the start of mining, .713. In the interview survey at Shiprock, the sex ratio in families of non-miners was 1.03, and in families of miners it was 0.73 (p < .05). Dr. Alan Goodman at the University of New Mexico has studied trends in the sex ratio in the general population in New Mexico and Arizona with particular reference to counties in the Four Corners area and the Navajo Indian Reservation, areas where uranium mining has been active_ His findings (unpublished) are as follows: (1) Beginning in the early 1950&apos;s, there has been a modest, but persistant and statistically significant decline in the secondary sex ratio for the state of New Mexico compared with the U.S., a decline that roughly parallels the emergence of uranium mining in the Grants mineral belt in northwestern New Mexico. (2) Data available for the 11 years since 1969 show that among the five counties with ratios significantly lower than the state

Jan 1, 1981

By Timothy J. Orr, Jami M. Girard

A NIOSH study on occupational deaths between 1980 and 1989 indicated that in the United States, mining had the highest average annual fatality rate (3 1.9 per 100,000 workers) of any other major industry. Since "lack of training" was often cited as the primary cause of accidents, NIOSH has been investigating new methods for effective training. One such method is the use of low- cost, desktop computers to simulate a virtual mining environment. Computer-based training offers several advantages over conventional training because the computer programs provide a three- dimensional environment that allows the trainee to practice using evacuation routes, encounter mining hazards, and view mining operations without being exposed to any real danger. One major focus of the project is mine escapeway multiuser training using desktop virtual reality programs. Researchers have imported mine maps into the software for the purpose of practicing actual evacuation routes and procedures. Various scenarios for evacuation can be practiced in a three-dimensional computer simulation of the mine in a disaster situation, complete with smoke, fire, and other dangers. Depending on the trainee&apos;s job description (i.e., foreman, shift boss, beltman, etc.), certain tasks need to be performed in addition to navigating primary and/or secondary escape routes. Each scenario allows for individual or team-based training and provides a means to educate mine workers in hazard recognition and hazard avoidance. Using this program, mine workers can practice evacuating various mine layouts without the danger and expense associated with escapeway training in an actual underground mine. Each scenario can be changed to test the trainee&apos;s reaction in a variety of circumstances and run many times so the trainee can practice concepts. This training experience will help reinforce the knowledge acquired during more conventional classroom instruction, and the inherent flexibility of the program allows training materials to be tailored to meet the specific requirements of individual mines.

Jan 1, 2002

By VIVEK KASHYAP, EVODY TSHIJIK KARUMB, PATRICK TAYLOR

Zinc ferrite is considered an integral phase of zinc residues as their presence can render the processing of zinc and critical metals difficult. It is a refractory phase, formed at high temperature in the presence of zinc (Zn) and iron (Fe) during oxidative roasting in zinc processing plants. Because it is refractory to efficient leaching, unreacted zinc ferrite gets concentrated in the final zinc residue, making it a viable source of zinc and indium extraction. The refractory nature of zinc ferrite makes the extraction of associated critical metals difficult. In order to explore a potential economic and carbon-neutral zinc ferrite processing technique, our previous study proposed the partial reduction of zinc ferrite followed by sulfuric acid leaching of the roasting product [1-3]. As demonstrated in our previous studies, partial reduction of zinc ferrite results in a mixture of ZnO, Fe3O4 and FeO, which can be further subjected to leaching for efficient extraction of zinc and critical metals such as gallium and indium.

Dec 1, 2022

By Neil J. Dahmen, Howard J. Handewith

INTRODUCTION Tunneling machines were introduced into civil con¬struction in the 1800s, but their practical applications were not realized fully until the 1950s. As of 1977, tunneling machines were being used on most tunneling projects of substantial size. As in civil construction, the mining applications of tunneling machines have included long drives such as tunneling for long ore-body develop¬ment drifts, long haulage tunnels, longwall access drifts, and long crosscut developments. Tunneling machines ranging from 1.75-m (5.7-ft) to more than I1.0-m (36-ft) diam are available from several manufacturers; machines for mining applications generally have ranged between 1.75 and 6.0-m (5.7¬and 20.0-ft) diam. Tunneling machines usually operate at or near horizontal grades and are supported by a rail-haulage backup system. However, declines and inclines have been made using alternative backup equip¬ment. Either circular or shaped tunnels may be bored, depending upon the particular equipment used. Using tunneling machines to bore openings through rock offers several advantages over the use of the drilling and blasting technique. These advantages include a rapid advance, continuous operation, uniformity of the opening size, smooth walls, and safe working conditions. Compared to drilling and blasting, boring reduces the disturbance of adjacent rock, thereby reducing the ground-support requirements and the exposure to water inflows. The smooth walls provide natural arching and present minimum resistance to the flow of air. A tunneling machine should be considered a spe¬cialized mining tool that is well-suited to certain mining applications. Properly applied and sustained, a tunnel¬ing machine contributes to realizing substantial econo¬mies in the development of underground mines. All costs herein are expressed in 1977 US dollars, unless otherwise noted. The mention of trade names and manufacturers is not intended to imply an endorse¬ment of any specific equipment. TYPES OF TUNNELING MACHINES As listed in Table 1, five principal types of tunneling machines were being manufactured in 1977. Each type of machine offers a special solution to a specific mining problem. Although each of these types of machines is described herein, most of this chapter is devoted to the full-face rotary rock-tunneling machine that has demon¬strated the greatest production in both civil construction and mining applications. Full-Face Rotary Rock-Tunneling Machines As shown in Fig. 1, a full-face rotary rock-tunneling machine consists of a rotating head that is fitted with rock-cutting tools and is forced into the tunnel face. This head is supported by a bearing on a structural support member that, in turn, is held in place by a hydraulically positioned wall-gripping mechanism. Both torque and thrust are reacted from the cutterhead, through the structural support and gripper mechanism, and to the tunnel wall. The rock cuttings fall to the invert at the tunnel face, and they are removed by means of cutterhead buckets or scoops that transfer the cuttings to a conveyor belt. After advancing the cutter¬head through a preset boring stroke, the tunneling machine is advanced by hydraulically pulling the gripper mechanism in from the tunnel walls, stroking forward, and resetting the gripper to the new forward position on the wall; the machine then is set for the next advance stroke. Full-face machines cut only circular openings. Ma¬chines with diameters as small as 1.8 m (6 ft) and as large as 6.1 m (20 ft) have been used in mining applica¬tions, excavating rock with unconfined compressive strengths in excess of 276 000 kPa (40,000 psi). Although special machines have been designed to turn on a radius of 30 m (100 ft) in both horizontal and vertical directions, the conveyors and backup sup¬port equipment generally limit tunneling machines to turns with a radius of more than 60 m (200 ft). The full-face rotary rock-tunneling machines have provided the fastest and most reliable production of any mining method or machine. These machines can be equipped to place any of a variety of ground-support systems, and they can be provided as "open" machines, as shown in Fig. 1, or as "shielded" machines, as shown in Fig. 2. The open machines have the advantage of allowing the ground to be supported as near to the tunnel face as possible. The shielded machines have been designed principally to allow placing precast con¬crete segments. The shielded machines completely pro¬tect the equipment and personnel at the heading, but they are economically limited to permanent long-life haulageways where full lining is required. Partial-Face Rotary Rock-Tunneling Machines As shown in Fig. 3, the partial-face rotary tunneling machine is equipped with a cutterhead that rotates slowly at about 0.21 rad/s (2.0 rpm). The single-disk cutterhead produces the tunnel section shown in Fig. 4 by means of an oscillating motion. These machines work on the undercutting principle, and they are avail¬able in spring-line dimensional increments of 0.1 m (0.32 ft) from 1.5 to 2.1 m (5.0 to 7.0 ft); the vertical dimensions are 2.4 to 3.2 m (8.0 to 10.5 ft), respec¬tively. Depending upon the tunnel width, the cutterhead disk may be fitted with from 8 to 16 drag-bit cutters. Penetration is achieved by means of hydraulic rams that force the tungsten-carbide bits into the rock mass. The operation is cyclic, with cutting occurring only on the upstroke. On the downstroke, the rotating cutter¬head draws the fallen muck from the invert into the panzer-type conveyor for rearward transfer. This feature allows time to either reposition ore cars or to exit the tunnel with muck trains while the machine is cutting, as shown in Fig. 5. Boom-Type Rotary Excavators The boom-type rotary-excavator tunneling machines commonly are known as boom-type continuous miners

Jan 1, 1982

The vast coal resources of North Slope, Alaska can be expected to attract substantial interest because the nearly flat lying coal beds of the coastal plan are specially amenable to surface mining. Mining on a scale large enough to justify coal development in this area could have severe environmental effects. The mitigation would be uncertain because large scale coal mining and reclamation operations have not been carried out in the arctic The deficiency of the scientific data base is another factor that requires consideration if coal mining has to develop in accordance with the objectives of PL 95-87. The objective of this paper is to establish the interrelationship between the problems due to permafrost and factors in reclamation of post mining land in order to find ways to transform nature in a rational and purposeful manner and to suggest specific reclamation approaches that may be appropriate in this region.

Jan 1, 1986

By A. Aly Selirn

An economic simulation model was developed to predict the amount of copper recovered from copper oxide deposits and the cost of producing it as a function of the deposit parameters. The economic simulation model includes models of fragmentation design and cost, copper extraction, solution distribution and recovery, effluent solution cutoff grade, and financial analysis. Cost and price indices were also developed to evaluate the economic feasibility of in situ leaching operations as a function of their starting date. Application of the models to various properties having the same area and different ore thickness shows that the effluent solution cutoff grade does not vary with the ore thickness nor with its grade. The percent of copper recovery is, however, shown to increase with the increase in the ore thickness and is independent of the ore grade. it is also shown that while the profit per unit of extracted copper increases with the increase in ore grade or ore thickness, the rate of return on total investment does not show any correlation

Jan 1, 1977

By W. K. Collins, C. L. Dahlin, D. C. Dahlin, W. K. O’Connor, G. E. Rush

Direct mineral carbonation has been investigated as a process to convert gaseous CO2 into a geologically stable final form. The process utilizes a slurry of water, with bicarbonate and salt additions, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, resulting in dissolution of the mineral and precipitation of magnesium carbonate (MgCO3). Optimum results have been achieved using heat pretreated serpentine feed material and high partial pressure of CO2 (PCO2). Specific conditions include: 155°C; P002=185 atm; 15% solids. Under these conditions, 78% conversion of the silicate to the carbonate was achieved in 30 minutes. Process mineralogy has been utilized to investigate the appropriate feed characteristics, identify the process products, and interpret the mineral dissolution and carbonate precipitation reaction paths.

Jan 1, 2001