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By G. Bloomsburg, R. E. Williams, S. D. Vincent

A modeling scheme is developed to simulate the hydrogeologic effects of mine design and development in unsaturated rock. Simulations are conducted using the UNSAT2 finite element computer program and hydrogeologic data from the site of a proposed mined-out waste repository at Yucca Mountain, NV. Results of the simulations are analyzed for: •variations in the direction of ground water flow and in the distribution of pressure head caused by the design of the mined out openings; and •mine design variables that affect the predicted rates of mine water inflow. Evaluating the hydrogeologic impacts of mine design and mine development in unsaturated rock is significant in several respects. Characterization of the preemplacement of wastes along the fastest path ground water flow system at the Yucca Mountain site has been a primary research effort. Ultimately, however, the degree to which waste isolation is achieved will depend largely on the post-mining hydrogeologic environment as altered by the mine design and on the radionuclide inventory and resulting heat effects of the repository. Therefore, an ongoing characterization of the proposed mined-out nuclear waste repository at Yucca Mountain, NV, is recommended. Modeling results indicate that: •mined out openings will affect the movement of ground water, both in rate and direction; •hydraulic effects of mine development depend on the hydrogeologic environment and on mine design geometry; •mine water inflow is possible in the unsaturated zone, even for mines developed in hydrogeologically homogeneous rocks; and •mine water inflow can occur at values of down ward flux that are appreciably less than the saturated hydraulic conductivity of the overlying rocks.

Jan 1, 1991

By M. Beus, S. Stewart, S. Iverson

Recent ore pass failures have underlined the need for improved designs, standards, structural monitoring methods and better hang-up prevention and removal techniques. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) are investigating methods to improve safety during the transport of ore in ore passes. Design criteria and hang-up prevention and remediation strategies involve studies of the effects of static and dynamic ore and waste-rock loads on chutes, walls, gates and support structures. Particle flow analysis methods were used to simulate the response of various ore pass designs to a wide range of ore loading conditions. A full-scale mockup of actual ore pass and chute assemblies was duplicated and tested for load response. Data from a particle flow code and the mock-ups were compared Loads on an active ore pass chute were measured

Jan 1, 2000

By K. Morsy, S. S. Peng

This paper deals with the causes and mechanisms of a massive pillar failure in a room-and-pillar mine. The mine employed a nine-entry panel system using supersection technique under a cover ranging from 91 to 168 m (300 to 550 ft). Chain pillar squeeze and large roof-to-floor convergence were first observed at the belt transfer point on the very inby side of the main entries. It propagated out by quickly, and, within 24 hours, it had covered an area approximately 1,250-m- (4,100 ft-) long by 762-m- (2,500-ft-) wide. The failure was caught and stopped by a solid barrier pillar. Using computer modeling, this study indicates that the massive failure was initiated because of a combination of undersized chain pillars in some panels and weak immediate floor. Also, the study shows that the massive pillar failure expanded to a large area because of the absence of barrier pillars between some panels and between mains and panels. Based on computer modeling, alternative mine plans were proposed to avoid such problems.

Jan 1, 2002

Minter's excellent recent paper (1990) on the great paleoplacer gold deposits of the Witwatersrand and its subsequent discussion (Cheney, 1991) and reply (Minter, 1991) provide an informative, interesting and up-to-date review of the geology of these unique ores and some long enigmatic questions regarding their origin. Clearly summarized by Minter (1990) are the compelling sedimentologic and stratigraphic relationships indicating that the Central Rand Group conglomerates are ancient placers and documenting the fluvio-deltaic conditions of their transport and deposition. As Minter (1991) indicates, Cheney's discussion broadens Minter's 1990 coverage of the subject by considering higher and lower stratigraphic units and by adding detailed comments concerning recently published information about metamorphic and age relationships. Cheney's discussion and Minter's reply also readdress the old controversy of epigenetic hydrothermal vs. syndepositional placer origin for these deposits. This controversy has been resurrected by: • recent recognition of hydrothermally-altered granites (HAGS) in the older Archean basement rocks that lie unconformably beneath the Dominion Group rocks north and west of the Witwatersrand depository; • recognition of greenschist metamorphic assemblages in the Witwatersrand strata; and • the presence of interpreted epigenetic mineral assemblages and textures in some of the deposits. These relationships are briefly discussed by Cheney who suggests they may result from later, superimposed metamorphism and deformation and do not prove that the gold was introduced by epigenetic/metamorphogenic processes. In his paper, Minter (1990) cited the 1986 abstract of a subsequently published paper by Hutchinson and Viljoen (1988) who also considered many of these aspects and attempted to integrate them all in a broad genetic hypothesis. In addition, they emphasized the additional important problem of determining the source for the Witwatersrand gold. Although this issue was partially addressed by Reimer (1984), Mossman and Dyer (1985) and Reimer and Mossman (1990), the question has been generally under emphasized in earlier work and was, therefore, not stressed by Minter and Cheney. Reimer (1985) also emphasized the importance of weathering of the basin's Archean hinterland and its affects on Witwatersrand sedimentation.

Jan 1, 1992

By R. V. Ramani, R. Bhaskar

The results of an experimental and theoretical research study into the spatial and temporal behavior of dust in mine airways is summarized. Experiments were performed in mine airways under both controlled and normal operating conditions. The controlled experiments included the documentation of the concentration and deposition patterns for two types of dust under three different velocities. Real-time dust concentration data were obtained using real-time aero- sol monitors (RAM-I) to determine the dispersion coefficient in a mine airway. On the theoretical font, a convection diffusion model of the dust flow phenomenon in mine airways was developed considering dominant mechanisms affecting dust transport and deposition in mine airways. Mechanisms modeled include turbulent and gravitational deposition, coagulation, and dispersion. In this paper, comparative analyses of results (8 the controlled experiments with the predictions of the mathematical model are presented. In addition to the overall validity, the adequacy of the individual components of the model, such as deposition in the total and respirable range, and dispersion are examined in light of the experimental observations. The experimental data from controlled experiments compared more favorably with model predicted results for similar conditions as opposed to the comparative analysis results for in-mine experiments. Specifically, the model predictions for an 800-m stretch of a mine airway reveal some significant differences from the behavior noticed in the mine. The deposition was lower than that predicted by the model. Consequently, concentrations were higher than those predicted by the model. The implications of these and other findings for further investigations are discussed in the paper.

Jan 1, 1987

By Hongjie Yu, Mike Mooney

Transitions between geological/geotechnical soil units have a critical impact on the operation and performance of a tunnel boring machine (TBM). Geostatistics-based probabilistic modeling is used to quantify the uncertainty in soil transition locations. This paper presents two unique soft-ground tunneling case studies where the results from the geostatistics-based probabilistic modeling are compared to the TBM data and as-encountered ground conditions derived from the actual TBM data. The assessment enhances the confidence in using geostatistics to improve ground awareness for efficient tunnel construction, minimizing different site condition (DSC) claims, and improving decision-making on tunnel projects.

Dec 1, 2022

By Ken A. Phillips

Like the Arizona jeans commercial says: Arizona's not just a state, its a state of mines. Nearly 300 mines operate in Arizona making it the largest nonfuel mining state in the nation. Although copper is king in Arizona's mineral complex, nonmetallic minerals play important roles both regionally and nationally. Throughout Arizona's mineral resource development history industrial minerals have dominated over the metals for most, but not recent years. The State's metal mining industry which makes Arizona the number one mining state in the United States is a relatively young phenomenon. Arizona was an important industrial mineral producer long before her metal mining industry got started. Salt, phosphates, silicates, and oxides as food additives, tanning chemicals, gemstones, components of aboriginal ordnance, pigments, and construction materials are among the minerals produced long before copper, gold, silver, and the other metals became important. Around 92 % of Arizona's mineral industry is made up of nonfuel minerals, 86 % of that is accounted for by copper. Another 4 % is taken up by copper byproducts of molybdenum, silver, and gold. The remaining 10% of the production is occupied by non-fuel, non-metallic minerals. Arizona's 1994 industrial mineral production of nearly $380 million ranks us among the top 25 in the nation and higher than the total mineral production of at least 15 states.

Jan 1, 1996

By Frank E. McCall, John K. Marshal, Fred Garcia

Since the advent of longwall mining systems in the United States, mine operators are increasingly relying on methane drainage techniques to supplement the ventilation system. The most commonly used technique is the vertical gob borehole. The number and spacing of vertical gob boreholes per panel is generally based on experience and underground conditions. To design a more efficient methane drainage systems, mine operators must accurately determine methane gas produced. Thus, mine operators must monitor gas flow and methane gas concentration on every vertical gob borehole on active panels at least once or twice during each 8-hr shift. As the mine grows, it is possible to have more than one operating longwall and many vertical gob boreholes. Thus, daily visits to each vertical gob borehole site can become very time consuming. During weekends when methane gas concentrations typically drop because there is no mining activity, borehole sites may not be visited. To obtain accurate gas flow data, a gob borehole monitoring system was designed and constructed by the U.S. Bureau of Mines (USBM). Gas flow, methane gas concentration, gas temperature, barometric pressure, and vacuum pressure of the exhaust fan are the parameters collected by the system. The system also includes circuitry for automatic shutdown of the exhaust fan and an alarm system before an unsafe condition is created. Telemetry components were also integrated into the system to allow for transmission of borehole data to the mine office. As a test, the system was installed and operated on a vertical gob borehole for six months. Test results indicated that intermittent measurements with hand-held instruments from vertical gob boreholes were always higher than gas flows measurements made by the gob gas analyzer system. This paper describes the system components, operational characteristics, and the results of the test program.

Jan 1, 1995

By Jianmin Qin, R. V. Ramani

The major parameters affecting dust flow at a longwall face are dust generation rate, air velocity and quantity distribution at the face, and the characteristics of the dust such as particle size distribution, density etc. Previous studies have identified the longwall shearer as the major source of the airborne dust in the faces. In this study, the effects of dust generation rate and shearer speed on the levels of ambient dust concentration are investigated. A series of experiments were performed under controlled conditions in a full scale simulated longwall face at the Lake Lynn Laboratory mine of U.S. Bureau of Mines using characterized bituminous coal dust. A trickle-duster was moved up and down the longwall face to simulate the shearer. In each experiment, a known amount of dust was dispersed by the trickle-duster into the air and the average dust generation rate was calculated. At the same time, gravimetric respirable and total airborne dust samples were collected and air velocity measurements were made along the face. The experimental conditions, data, and results are presented and discussed in this paper. The airborne dust concentration and air velocity data indicate that the concentration increases and air velocity decreases with distance from headgate for the first half of the face. Towards the tailgate, the air velocity increases with increasing distance but the dust concentration levels off with some variations. The data show that a higher dust generation rate results in higher dust concentration levels. More importantly, the data show that the rate of increase of airborne dust concentration is higher than that of dust generation rate. For the same air velocity distribution and dust generation rate, lower speed of the dust source results in higher airborne dust levels at the face.

Jan 1, 1991

By Lynn B. Hales, Randy A. Ynchausti

Introduction There continues to be a large economic opportunity associated with improving process performance through advanced process control systems within the minerals industry. The basis for this opportunity lies in the inherently low efficiencies of many of the unit operations found in mineral processing plants as well as the continual variation that is present in the ores being processed. The ageless target of such control systems is improved recoveries and concentrate grades, higher processing rates and lower unit costs. Many plants are enjoying the benefits of modem, well functioning process control systems but few if any have achieved plant-wide optimization in an economical sense. As new process modeling and control technologies, such as neural networks, continue to evolve and develop, the potential for plant- wide optimization is becoming a closer reality. Neural network technology appears to have a significant potential in the general field of process control and control of mineral processing operations. Neural networks are an emerging technology that have been evolving out of the study of biological systems since the early 1940's. The first software simulation of neural computing networks was reported in 1956 by Nathanial Rochester of IBM Research during the first conference on artificial intelligence which was sponsored by the Rockefeller Foundation. Neural Networks Neural networks can be considered to be a class of computer program that perform their problem solving functions based on a rudimentary model of the human brain and how it solves problems. Traditional computer programs and even computers themselves solve problems or process data sequentially and in a deterministic manner. The human brain, on the other hand, processes data and solves problems in a massively parallel fashion. We think of computers normally in terms of having a single processing unit, sometimes a co-processor to assist in certain activities such as mathematical functions or communications, bytes of memory, processing speed and program/data storage size.

Jan 1, 1992

By C. V. Deutsch, J. B. Boisvert, J. L. Deutsch

Data used to build geostatistical models come from a wide variety of sources with potentially differing sample errors and volume supports. Typically all available sample measurements are pooled together for statistical analysis irrespective of the quality of the data. The sample data is used to assess spatial continuity, make local estimates and assess uncertainty. A new methodology is proposed to simplify accounting for samples of differing quality. The result is improved estimates with higher weights assigned to high-quality samples, while low-quality samples receive less influence in resource estimation. A new dimension, d, is introduced and calibrated to account for sample error and/or volume during estimation. The addition of an extra dimension can be easily incorporated in existing kriging or inverse distance workflows. The only additional parameters required are the sample error and volume for each datum. The methodology is demonstrated and the improvement in local accuracy is documented. Extending the dimensionality of the domain to four (three spatial dimensions and the additional d dimension) requires a valid 4D variogram model; therefore, the spherical variogram model is generalized to arbitrary n-dimensions.

Jan 1, 2011

A chartered bus with about 30 attendees of the just completed 1998 SME Annual Meeting headed toward Green Cove Springs, FL, which the author had been told was located somewhere south of Jacksonville, FL. In conjunction with the meeting in Orlando, RGC (USA) Mineral Sands provided a tour of its facility. The author had worked with heavy minerals on a laboratory scale, performing the usual gravity and magnetic separations, but had never been to a heavy mineral mine and processing facility. Years ago as a metallurgist, the author once applied for a job in a heavy mineral operation in Florida -it may have been the same operation. After turning north on to Highway 95, the endless billboards promoting beach-front retirement communities proved the Atlantic ocean was just a few miles away (although the author never caught a glimpse of it). After another hour, the bus suddenly turned west and continued inland for about 65 km (40 miles). The thought occurred, "We are talking about beach sands, what are we doing heading away from the ocean?" As the bus continued inland, the author was struck by the flatness of the land and by the lakes, rivers and wetlands. He was also impressed by the many fine stands of pine and hardwoods. The office of RGC (USA) Mineral Sands is located about 16 km (10 miles) south of Green Cove Springs. Upon leaving the bus, members of the tour were greeted by Graeme Sloan, general manager, and Elliot Mallard, manager of mining. They provided some general information about the operation, including a slide show. RGC's Florida operation produces four concentrates: zircon (ZrSiO,), rutile (TiO,), ilmenite (FeTiO,) and leucoxene (an alteration product of ilmenite containing 67% to 70% TiO,). With a work force of about 170, the annual production of the above products is about 23,27, 45 and 14 kt (25,000 30,000 50,000 and 15,000 st), respectively. RGC also has other mineral sand operations, in addition to gold and base metal mines, mostly in Australia.

Jan 1, 1998

By K. Nuttall, S. Vijayan, A. J. Meinyk, R. D. Singh

For conventional applications, there is limited demand for rare earth elements as well as yttrium and scandium. But the emergence of new high technology applications such as supermagnets, lasers, and superconductors should result in significant demand for some of these elements. This article examines the anticipated applications and demands for rare earth elements over the next decade. It also looks at the implications on the use of available resources. In the context of a growing demand, process methods are reviewed for the recovery of rare earth elements from conventional and unconventional resources. And the article also discusses the challenges facing the mining industry in meeting this opportunity. Reserves and reserve base The rare earths (RE) are a homogeneous group of metallic elements occupying the area from lanthanum to lutetium in group IIIB of the periodic table. Yttrium and scandium are also included with the rare earths because of their chemical similarities and common existence in nature. These 17 elements and their atomic numbers are shown in Table 1. The rare earths are widely distributed in low concentrations throughout the earth's crust (Hedrick, 1985). They occur in many rock formations including basalts, granites, shales, and silicate rocks at concentrations of 10 - 300 ug/g. They also occur in more than 160 discrete minerals. Most of these are rare, but may contain as much as 60% rare earth oxides (REO). More than 95% of the REO occurs in three minerals: monazite and bastnasite for the light rare earths and xenotime for yttrium and the heavy rare earths. Apatite and multiple-oxide minerals, such as euxenite and loparite, are also commercial sources of the lanthanides and yt-trium. Rare earths do not occur in nature in the elemental state. And, except for scandium, they do not occur in minerals as individual compounds. Bastnasite and monazite are the two major minerals used commercially to supply most of the rare earths (Hedrick, 1985). Bastnasite is a key raw material source for the cerium subgroup elements. The largest known bastnasite deposit occurs with iron ore minerals in China. The second largest deposit is situated in California. Typical rock analyses of the fluorocarbonate mineral bastnasite deposit in California show about 15% bastnasite. The REO content of that is about 50%. Monazite is present in beach sands in many parts of the world. This includes India, Brazil, Australia, South Africa, the

Jan 1, 1989

By Guy G. Jr. Granger

INTRODUCTION Due to the current depressed state of the mining industry, many mining companies have been forced to operate at less than maximum capacity. This paper will describe how the AMAX Henderson Molybdenum Mine and Mill near Empire and Parshall, Colorado respectively have utilized operations scheduling and budgeting to achieve production targets at minimum operating costs The AMAX Henderson Molybdenum Mine and Mill have been operating most recently at approximately sixty percent of maximum capacity. OPERATIONS SCHEDULING Production Targets. The production targets are tons, operating days, tons per opera- ting day, head grade, recovery, and pounds of molybdenum. One specific objective of operations scheduling is to meet the production target for pounds of molybdenum. Present market conditions dictate that production be adjusted to match sales of molybdenum. Over-production and creation of molybdenum inventories is unacceptable. In summary, the product ion target for pounds of molybdenum must be met, but not exceeded. Capacity. The AMAX Henderson Mill single stage open crushing circuit capacity is 48,000 dry short tons per day. The AMAX Henderson Mill single stage semi-autogenous primary grinding mill circuit capacity is 38,000 dry short tons per day. All other AMAX Henderson Mi 11 circuits such as rougher flotation, regrind, cleaner flotation, lead leach, filtering, drying and concentrate handling are sized to accommodate the 38,000 dry short tons per day and pro- ducts from same. The tailing delivery system is designed to accommodate tailing from a 38,000 dry short tons per day operation. Constraints. One mill production scheduling constraint is that the mill operating schedule must be the same as mine production, ore haulage and crushing. There is a total crushed ore stockpi1e storage capacity of 240,000 dry short tons. This breaks down to 60,000 dry short tons of crushed ore over the three reclaim pan feeders for each of the four primary grinding mill circuits. However, there is only approximately 10,000 dry short tons of live crushed ore available over the three reclaim pan feeders for each of the four primary grinding mill circuits. Dozers must be utilized to re- claim and push the other crushed ore. Primary grinding mill throughput is

Jan 1, 1986

By Franz Wilhelmstoetter, Christian Karner

"The Confederation Line is phase one of Ottawa’s light rail transit, which consists of 13 stops and stations. The project’s center piece is a 2.5 kilometer (1.6 miles) long tunnel with three underground stations leading underneath downtown Ottawa and is constructed within feet of adjacent buildings. The downtown stations, Lyon and Parliament, are caverns approximately 16.5 m (54 ft) by 18 m (59 ft) in a horseshoe configuration constructed in rock, while the third station, Rideau, is approximately 22 m (72 ft) by 18 m (59 ft) in an oval configuration and constructed in mixed ground. The paper will discuss design decisions made early on in the project such as excavation method, unique construction sequencing, and equipment selection, and go on to include corresponding progress rates. The paper also documents design and construction challenges of large caverns in very close proximity to existing buildings and varying ground conditions. Finally, an overview of achieved construction milestones and a current construction progress will be presented. Station cavern excavation is expected to be completed in early 2016. INTRODUCTION The number of urban metro construction projects has certainly increased over the last decades. Cities are growing rapidly all over the planet and many are striving to keep up with the increased demand for public transportation. One of the most feasible types of inner-city transportation with the capacity for large quantities of passengers are metro (subway) systems. Still, large construction projects in dense urban areas often affect the city’s residents in mostly negative ways. During construction, residents face the obstacles of road closures, noise, dust, economic loss for businesses, and property value losses are common. In other words, individuals are directly affected by the way new infrastructures are planned, designed, built and operated. The tunneling industry offers unique opportunities of keeping these side effects to a minimum and possibly avoiding them all together. Although challenged by a variety of constraints (some of which will be discussed in this paper), urban tunneling applications offer a chance to keep cities environmentally, economically, socially, and culturally sound during construction."

Jan 1, 2016

By T. M. Karppanen

Shotcrete is used both in mining and tunnelling for supporting rock. Both dry and wet processes are used for shotcreting, and each produces good quality concrete. Thick shotcrete layers function as a concrete arch supporting loose rock. Thin layers prevent relative movements between the blocks of rock due to the fine concrete in the cracks and joints. No progressive fallouts occur since key blocks are kept in place. Rockbolts are often used together with shotcrete in order to create an arch around the tunnel making the rock to support itself. Shotcrete is sprayed either manually or by means of mechanized equipment. The aim is to spray required the layer thickness in one pass and with a minimum amount of rebound. Sprayed layers should also be as even as possible. The tip of the nozzle should be moved in circular movements. The shotcrete should be sprayed at a right angle to the rock surface; the optimum distance from the nozzle to the application surface must be found by experiment. In a mine shotcreting forms a materials handling system which includes batching, transporting and the actual shotcreting. The equipment used vary depending on the spraying method, mining conditions and the location of the mine. Shotcreting is performed with a purpose-designed unit in most cases where operation is mechanized. The shotcreting unit consists of a spraying machine with a hose and a nozzle, an additive system, a manipulator and a mobile carrier with all the necessary controls and accessories. The key element of the unit is the shotcreting manipulator which holds and guides the nozzle as required. The manipulators currently in use are hydraulically operated, and their remote controlled booms are also often called robots. These manipulators have enabled users to increase their output capacities, to remove the operator away from unsafe areas and from the influence of dust and rebound. Furthermore, they improve the shotcrete quality and reduce shotcreting costs.

Jan 1, 1989

By Alena Conrads, Markus König, Markus Scheffer, Markus Thewes, Hannah Mattern

"INTRODUCTION In recent years, the development of tunnel boring machines has revolutionized the tunneling industry. The general structure of a tunnel boring machine (TBM) can be described as a multi-component system. To achieve high performance rates, machine elements have to perform reliably. Performance losses and interruptions of the construction process should be prevented or at least, reduced to a minimum. In order to achieve high advancing rates, cutting tools must be in good condition at any time. Furthermore, failure of individual tools might result in increased and faster wear of remaining structural components. For this reason, maintaining and replacing cutting tools is crucial to prevent project delays due to insufficient boring performance. Precise prognoses concerning the prevailing geology are infeasible and thus, efficient scheduling of maintenance actions is challenging. The intention of this work is to analyze different approaches of TBM maintenance in soft ground. Different strategies are analyzed by the use of a simulation approach. Cutting tool condition is regarded as performance limiting factor. The maximum operation time of the cutting tools is determined using the “Soil Abrasivity Index”. A case study serves to show the effects of different maintenance strategies on total project duration. SCHEDULING OF MAINTENANCE ACTIONS Scheduling maintenance actions of single and multi-component systems concerns numerous fields of industrial production. Concentrating on mechanized tunneling in soft ground, cutting tool maintenance represents the most common reason for intermission of advance (Köppl 2014). In literature, time-based and condition-based maintaining techniques are widely discussed. The following section outlines the principles of time- and condition-based policies. Furthermore, examples for their applications in recent research are given. Time-Based Maintenance In general, the time-based maintenance approach assumes that the failure behavior of the system components is predictable. Maintenance actions are scheduled according to predefined intervals (e.g., hours, days, weeks). A detailed analysis of preventive repair times or interval forms the basis for maintenance decisions. For this approach, an adequate quantity and quality of data is fundamental. Numerous studies deal with the analysis of time-based maintenance for production equipment. In fields of mechanized tunneling, unplanned machine downtimes restrict the applicability of time-based maintenance approaches. Thus, this paper mainly focuses on condition-based maintenance."

Jan 1, 2016

By R. N. Chakravorty

It is well established that coal can react with oxygen in air at ambient temperature and as a result heat is produced. If the heat is not fully dissipated the temperature of the coal mass will increase, thereby enhancing the rate of oxidation with a greater production of heat. If this phenomena continues, the coal mass can ignite under favourable heat accumulation conditions. A number of mine fires are caused each year due to this phenomena, commonly known as spontaneous combustion. The early detection of spontaneous combustion is of prime importance to mining engineers since any fire which could be detected at an early stage may save the mine from considerable damage and subsequent loss of production. Obviously, there is no single general criteria by which one can assess whether the under- ground mining of a coal seam will result in liability to spontaneous combustion. This has made it imperative to develop systems for the early detection of heating and to follow its development. In recent years considerable advances have been made in the design and development of methods for the early detection of spontaneous combustion. The Mining Research Laboratories (CANMET) is presently investigating the problem of spontaneous combustion in coal mines with Kaiser Resources Ltd. at their hydraulic mine at Sparwood, B.C. on a co-operative basis, and some of the work was described earlier in the Canadian Institute of Mining & Metallurgy Bulletin (1,Z). This paper summarizes and updates the work done by CANMET on the detection of spontaneous combustion in coal mines.

Jan 1, 1980

By R. C. Babcock

Exploration for mineral deposits in the western United States is increasing annually, and the data generated by this effort are increasingly complex, diverse, and abundant. It is obvious that to make full use of this data base, which is both private and public, the technology of the computer must be involved. To lay out the framework for discussion of the particular uses of computers in all steps of exploration, this chapter will discuss the various approaches to the reconnaissance program which might be considered, the types of data to be acquired, the interpretation of these data, and the generation of recommendations based on this interpretation. Where possible, some of those areas where computer technology is now used will be pointed out. The discussion will cover the extent to which the computer is now utilized in those areas or where it should be brought into the program to aid in these activities. However, this chapter will not present an exhaustive evaluation of this technology, but will stress the exploration job and its requirements, so that subsequent discussion of the technology itself can be placed in perspective.

Jan 1, 1979

By H Sohn, R. R. Fernández

Microscopic gold inclusions in sulfide minerals cannot typically be extracted by conventional cyanidation. The gold ore must be pretreated to oxidize sulfide minerals associated with gold and to remove other minerals and chemical compounds that interfere in the cyanidation leaching process. The recovery of gold from refractory sulfidic-carbonaceous ores after roasting pretreatment was studied. With the addition of an oxygen-containing gas (e.g., air or oxygen-enriched air), sulfides of iron, zinc. copper and other metals are tramformed into solid oxides or sulfates and gaseous sulfur dioxide at elevated temperatures (e.g., 400° to 800°C). When the sulfides are oxidized, individual particles lose internal volume and become porous, allowing leaching solutions access to the gold. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent on the roasting conditions and roasting method. The optimum combination of particle size, roasting temperature, reaction time and oxygen concentration in the off-gas was determined for a typical refractory sulfidic-carbonaceous ore from the Carlin Trend in Nevada. The tests were run using a 150-mm laboratory rotating tube furnace and 160- and 200-mm.fluid-bed pilot roasters. Laboratory results indicated that the maximum gold extraction was 92%, with the head and the leach residue containing 5.7 and 0.4 g/t (0.166 and 0.013 oz/st) Au, respectively. The maximum extraction was achieved under the following roasting conditions: a top particle size of 150 yin, a residence time of 2 hrs, a roasting temperature of 475°C and with 40% oxygen (by volume) in the off-gas. Similar results were obtained from circulating fluid bed (CFB) pilot-plant testing. The maximum gold extraction was 90%, with the head and leach residue containing of 5.1 and 0.5 g/t (0. 149 and 0.015 oz/st) Au, respective) v. These results were achieved with the same particle size and oxygen concentration as in the laboratory testing but with the roasting temperature of 500 ° to 525°C and a residence time of 30 min.

Jan 1, 2000