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By Gerhard Mücke

Geothermal and operational reasons in the German coal mining industry make it necessary to an increasing extent to climatize coal faces and headings by means of refrigeration plants. Air coolers installed on coal faces as well as in gateroads play an important part in such climatization. They must transfer, under difficult conditions, the refrigerating capacity supplied by central or de-central refrigeration plants from the chilled water to the air in the workings. The performance data of two new types of coalface coolers and of two different types of gateroad coolers were measured in two testing stations under different thermo- dynamic conditions with dust-free fresh air. As air coolers must be installed particularly at working points with a high .dust load the heat exchanging surfaces are fouled for the most part causing an essential reduction of the refrigerating capacity. The investigations therefore were extended to measurements with a certain dust load in the intake air of the coolers.

Jan 1, 1980

By William E. Spence

Gold was discovered at the Haile mine in Lancaster County, South Carolina in 1827 or 1828, and since that time the mine has been worked intermittently by both open pit and underground methods until its forced closure in 1942 by World War II. Production figures are incomplete, especially for the early years, but the total gold produced is estimated to have been greater than 200,000 ounces. Thus, the Haile mine has been the most productive gold mine in the eastern United States. The upper, residually enriched ores were relatively rich, but the bulk of the production has come from the mining of lower grade ores.

Jan 1, 1978

By Joseph M. Hans

INTRODUCTION The decontamination of a uranium mill site is principally an earth moving task. The task can be completed effectively and efficiently by selecting the proper earth moving equipment and using that equipment within its particular constraints for decontamination work. A considerable backlog of experience concerning earth moving equipment selection and use was acquired during the decontamination work conducted at the former Shiprock, New Mexico, uranium mill site. This experience was acquired by trial and error while decontaminating over a wide range of depths and different types of terrain. Many different types of excavation equipment were available to the Shiprock decontamination project because the Navajo Engineering and Construction Authority (NECA) heavy equipment operator's school was doing the decontamination work and a variety of equipment was needed for training. The equipment is described and its general use for decontamination is discussed. Its on-the-job use for decontaminating the Shiprock millsite is presented. [EARTH MOVING/ANCILLARY EQUIPMENT DESCRIPTION AND DECONTAMINATION CONSTRAINTS] Tractor-Scrapers The most commonly used scraper is the bottom-dump type because it is highly mobile and can dig, carry, and spread loads. In this type a tractor is connected with a yoke to a scraper bowl (Figure 1). The bowl is essentially a rigid box that pivots around the rear axle, opening to the front. A hardened steel knife, or bit, is attached to the leading edge of the bowl. When scraping, the bit penetrates and forces the earth overlying the bit edge into the scraper bowl as the scraper moves forward. When the bowl is full, it is closed by lowering a closure or apron against the cutting bit. The load is dumped while moving, by raising the apron and forcing the load from the bowl with a crowd, or ejector. The height of the dumped load is controlled by adjusting the bit height when dumping. Scrapers of this type generally do not have enough power to scrape up loads unassisted. Loading assistance is generally provided by a crawler tractor that pushes from the rear against the scraper's push block. Some scrapers are made self-loading by adding an additional engine for the extra power needed for the load pick up. Another commonly used self-loading scraper uses a loading elevator (Figure 2). The elevator consists of two roller chains carrying crossbars. The elevator is rotated when scraping and the crossbars cut the earth above or in front of the bowl bit, forcing the load into the scraper bowl. No apron is used on elevating scrapers. The load is dumped by partially retracting the bowl floor and pushing with an ejector. Scrapers have some undesirable characteristics when used for decontamination work. One characteristic is that a clearance space exists around the apron when it is in its closed position. Part of the load (especially sandy soils) dribbles through the

Jan 1, 1981

By W. E. Horst

Raw materials and mineral products are crushed, ground, or pulverized for a variety of reasons. Some of the most important reasons for size reduction are: to liberate marketable mineral species from a matrix of commercial minerals and gangue, to promote rapid chemical reaction through exposure of large surface area, and to produce a material with desirable size characteristics for handling, utilization, and storage. Comminution processes are currently used on vast tonnages of raw material annually. In the mineral industries where mineral products and other solids are processed, the various size-reduction unit operations represent a major portion of the manufacturing costs. The comminution process is an expensive unit operation from the stand- point of both capital and operating costs. Power consumption is large, and the energy conversion to useful work is very small regardless of the size-reduction system. In energy terms, about 1% of the all electricity generated throughout the world is expended in crushing and grinding operations by the cement industry alone. Comminution is a general term for size reduction that may be applied without regard to the actual breakage mechanism involved. General type of size-reduction equipment include crushers, tumbling mills of various type, impact mills, fixed-path mills such as a roller mill, and fluid-energy mills. Some comminution machines accomplish

Jan 1, 1985

By J. G. Henning, R. Edrissi

This paper describes a practical methodology, based on numerical modeling, for the prediction of progressive failure of underground-mine stopes having cable-bolt support. A case study of the 40-761 scope at the Kidd Creek mine, Timmins, Ontario, Canada is presented. Scope 40-761 was mined by blast hole open sloping in 1986 and was a lead scope within a mining block located between levels 36-1 and 38-2. Initially designed to peak at level 38-2, the scope back caved upwards =40 m towards level 36-1. After caving began, cable bolts were installed above the stope from level 36-1. The stope eventually stopped caving when the falling rock mass encountered a sufficiently high cable density. This paper provides details of the geomechanical data and modeling results of the case study. Numerical modeling of cable bolts around the mine stoke was carried out using a finite-element modeling software. The software, known as e-z tools, was developed by the first author.

Jan 1, 1996

By D. Harris, M. Osterberg

This paper examines the economics of acquiring mineral exploration rights by royalty-rate bidding when the royalty basis does not provide for full cost recovery. Bidding takes place prior to exploration and the documentation of actual tonnage and grade. Consequently, it increases considerably the risk to exploration capital when the fraction of cost recovered is small and the product price exhibits large fluctuations. Price and grade risk are demonstrated on a 360-Mt (400-million-st) porphyry copper deposit by Monte Carlo simulation of discounted-cash-flow analysis. Copper price is modeled as a stochastic price process, and costs are based on US Bureau of Mines cost models. When both grade and price risk are considered, the probability for a negative NPV is 0.54, given a royalty rate of 5% applied to a basis that allows the recovery of costs up to 50% of product price. Investment risk could be considerably reduced by defining the royalty basis to allow greater cost recovery. Although such a basis would require society to share in the risk, society would benefit from greater resource development.

Jan 1, 2000

Since first introduced, the coal mine roof rating (CMRR) has been widely accepted as a tool for geologic characterization and mine planning. This paper discusses the application of the CMRR to another practical ground-control problem: extended cuts. Extended cuts, i.e., cuts greater than 6 m (20 ft) in length, are commonly used with remote-control continuous miners. Extended cuts can greatly increase productivity, but they have been associated with a number of fatal roof-falls. When extended cuts are attempted in weak roof material, the roof may collapse before it can be bolted Until now, it has not been possible to predict where conditions may not be suitable for extended cuts. In this study, data on the CMRR and extended-cut experience were collected at 36 mines in seven of the United States. It was found that, when the CMRR was greater than 56, deep cuts were routine in nearly every case. When the CMRR was less than 37, extended cuts were almost never taken, and, when the CMRR was between 38 and 56, extended cuts were sometimes, but not always, feasible. The data also show that extended cuts are less likely to be stable if either the entry span or the depth of cover increases.

Jan 1, 2000

By A. T. Sapulek, C. S. Özveren, D. W. Dixon

The prediction of underground methane emission from longwall coal faces has been extensively researched for a number of years and numerous prediction methods have been devised. Many coal mines employ sophisticated environmental monitoring equipment which generates large amounts of data including, methane concentration, air velocity and barometric pressure. Presently this information is mainly used only to indicate alarm and danger levels of the monitored data for management purposes, however, the potential uses of this data are enormous[1]. This information could be used to good effect within a production/methane emission strategy as detailed in a previous paper[2]. The paper presents a practical application of artificial neural networks to underground methane prediction. Data on methane concentration and coal production has been obtained from an underground coal mine. The data is used in a neural network architecture and forecasts of methane concentration have been obtained. The forecasts are examined and there is a discussion of the potential use of the predictions from neural networks in the field of mining production control.

Jan 1, 1995

By D. Veigel, J. D. McKay

Model enhanced Expert control has been implemented at the Newmont Lone Tree mill grinding plant as well as rule based Expert control for flotation and thickening circuits. The project has been successful in producing benefits but more importantly has contributed to an ongoing effort for continuous process improvement. This paper discusses how the control at Lone Tree has evolved and the part that Expert control has played in the overall improvements made. Specific examples of how the advanced control has integrated with instrumentation and stabilizing control are given and illustrations of how it has been effective in defining limitations and bottlenecks in the process or process control areas are provided.

Jan 1, 2002

By Michael J. Shulman

Outcrops of the Nubian Sandstone Series cover approximately 180,000 km2 in southern Egypt. Within the series, oolitic iron ore beds occur. The only comprehensive information available on stratigraphy of the iron beds is for the area east of Aswan, otherwise information is exiguous, sparse or unreliable. Based on this low level of information, the iron potential of the Nubian Sandstone Series was assessed and an exploration strategy formulated specifically tailored to the assessment. The area covered by the Nubian was divided into five regions, each comprised of 100 cells. A spatial distribution, i.e. negative binomial, was assumed adequate to describe the number of targets per cell and was indirectly calculated using a compound poisson distribution. Estimate of the only unknown parameter - the average number of targets per cell - implicitly/explicitly incorporated available geologic and economic information into the assessment. A probability distribution for the number of targets per region was then derived from the cell probability distribution. An allocation model based on the regional probability distribution assessment as well as on an estimate of the exploration effectiveness and on the exploration budget determines the optimal time to be spent in each region.

Jan 1, 1986

By Gordon D. House, J. B. P. Sawyer

The Bannockburn gold prospect is a new discovery in Ontario's oldest gold camp at Eldorado, eastern Ontario. Mono Gold Mines Inc. of Vancouver, British Columbia, acquired the property in 1980 and in 1984 discovered a previously unreported gold bearing quartz vein system to the northeast of the old Bannockburn Mine. Extensive diamond drilling carried out since 1985 defined a quartz vein system over 475 m (1 ,500 ft) of strike to a depth of over 105 m (350 ft). Limited underground exploration by decline to the 22.9 m (75 ft) level in 1988 confirmed the continuity and tenor of the quartz veins. Gold occurs as native metal with minor sulphides and bismuth tellurides in a quartz carbonate vein system within metasedimentary and metavolcanic rocks of the Grenville Province. Metallurgical test work on a surface bulk sample was favourable. Estimates of drill indicated reserves have been made as well as reserves based on the limited underground exploration.

Jan 1, 1989

By Robert J. Timko, R. Lincoln Derick

The Bureau of Mines evaluated the integrity of escapeways in a three entry underground coal mine. A center conveyor belt entry (secondary escapeway), was flanked by an intake (primary escapeway) and a return entry. Diesel equipment was used throughout the mine for material and personnel haulage. A carbon monoxide monitoring system, tied to a data recording computer on the surface, was deployed throughout the belt entry and at selected sites in the intake and return entries. Previously, the company had a fire of unknown origin in another mine, which prompted an interest in the performance of their escapeways. An initial, qua1itative evaluation was performed by burning approximately 14 kg of coal at the mouth of the intake entry. The first test was followed by a similar burn at the mouth of the belt entry. These initial trials showed a high quantity of leakage between entries. In several follow-up evaluations, simulated fires, using a tracer gas, were set in the intake and belt entries. Tracer gas concentrations were obtained in all entries at four different underground locations. The results of these tests showed that permanent stoppings could not guarantee isolated, contaminant-free escapeways.

Jan 1, 1989

By G. G. O. O. Uwadiale, E. G. Okafor

A study was performed to characterize the Ishiagu lead-zinc deposit prior to beneficiation. The study included the use of XRD, SEM and both reflected- and transmitted-light microscopy. The results showed that the ore consists mainly of galena (PbS), sphalerite (ZnS) and quartz (chert), with pyrite, siderite and chalcopyrite occurring as trace minerals. The textural relationships among the minerals, their grain sizes and their locking characteristics, coupled with the chemical analysis of the ore, indicated that the galena and sphalerite can be separated by conventional beneficiation methods.

Jan 1, 1998

By H. L. Hinds

Economic pressures to increase production to profitable levels reduced the Homestake's gravity recovery and overall recovery to un-acceptable levels. The operation of the Home-stake gravity gold circuit has increased gravity gold recovery to over 50%, improved overall recovery and increased mill availability for increased tonnage. The gravity circuit consists of three gravity gold recovery stages. The Circuit has four (4) duplex jigs, four (4) belt concentrating strakes and four (4) concentrating tables.

Jan 1, 1989

By K. Morsy, S. S. Peng

This paper deals with the causes and mechanisms of massive pillar failure in a room-and-pillar mine that employed 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 outby quickly and within 24 hours it had covered an area approximately 1,250 m long by 762 m wide (4,100 x 2,500 ft). The failure was caught and stopped by a solid barrier pillar. Using computer modeling, the study indicated that the massive failure was initiated due to 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 no barrier pillars between some panels and between mains and panels. Based on the computer modeling, alternative mine plans have been proposed to avoid such problems.

Jan 1, 2000

By A. C. Kunkie, C. J. Marshall

Highly delaminated muscovite mica products (WG-1 and WG-2) have been developed by J.M. Huber Corp. The micas are characterized as a 325-mesh product having high brightness and very narrow particle size distribution. At 40% loading in polypropylene, WG-1 mica provides substantial improvement in tensile modulus and equal tensile strength to unfilled polymer; in high-density poly- ethylene (HDPE), WG-1 provides four times the tensile modulus and a 50% increase in tensile strength over unfilled polymer. Surface modification of the water-ground mica (SM ™) provides substantial improvement in tensile strength over untreated mica at greater than 20% loading in polypropylene; in HDPE, tensile strength is twice that of unfilled polymer.

Jan 1, 1988

By Stephen W. Kline

Rock suitable for crushed-stone aggregate is almost entirely restricted to the Highlands region of Arkansas, mostly from Paleozoic sedimentary units, but also from a few Cretaceous igneous plutons. Reserves in the state are sufficient for local needs, and Arkansas is geographically well situated for export markets to the south, where resources for crushed-stone aggregate are lacking. A study of 423 quarries, test pits, and exploration sites in Arkansas has been completed to evaluate the relative quality of bedrock units for producing crushed aggregate. Of these, 274 sites have records of engineering tests for stone evaluation done by the U.S. Army Corps of Engineers and/or the Arkansas State Highway and Transportation Department (AHTD). Of the 1,775 sample records from these sites, the most commonly reported parameters are the LA abrasion test and the Na-sulfate soundness test. Many records also have absorption and specific-gravity data, and, for some, petrographic information helps identify the potential for alkali-silica reactivity in portland-cement concrete. By determining the bedrock sources of the tested samples, comparison is made between the various geologic mapping units as to their relative quality for crushed stone.

Jan 1, 1999

By Eung Ha Cho, Olufemi Olajide

A laboratory study of dense-medium cycloning with Redstone seam coal has been conducted. The investigation was performed using a 203 mm (8 inch) Heyl-Patterson dense-medium cyclone. Two underflow orifices of 31.8 mm (1.25 inch) and 44.5 mm (1.75 inch) in diam were used. The effects of feed pressure and particle size were determined on the cycloning performance. In addition, the cyclone performances with coal-rich and refuse-rich samples were also investigated. The results of the experiments were analyzed using basic hydrodynamic principles. The increase in the feed pressure increases the specific gravity of separation (defined as the specific gravity of a particle which has an equal chance of reporting to either the overflow or underfow) for both underfow orifices. The specific gravity of separation increases as the particle size decreases with the smaller underflow orifice. However, an opposite relationship has been observed with the larger under flow orifice. The separation becomes sharper with the smaller under flow orifice than with the larger underflow orifice especially for fine material. Also, the separation becomes sharper with an increased feed pressure for a coal-rich sample. However, this effect is less significant for a refuse-rich sample. This means that a high feed pressure is required for a coal-rich sample to maintain a good separation. It also means that applying a high feed pressure provides a good separation regardless of the type of feed coal in terms of ash content in the solid.

Jan 1, 1990

By Wenhua Li, Tsuyoshi Adachi

Resource nationalism is essentially mandatory government intervention in natural resources businesses by political or economic means in order to benefit the nation and the people. It is attacking the mining industry more and more rampantly by all kinds of means since the twenty-first century. Poor countries who count on a resource-led economic growth usually find themselves trapped into “resource curse”. The harmfulness of resource nationalism for investors is that one event can quickly escalate and lead to a chain of events which make projects commercially unavailable. In spite of historical and theoretical social investigations in the causes of resource nationalism, rare studies engaged in quantification of dominant parameters of it. The objective of this study is to find significant factors that dominate the occurrence of resource nationalism for important metal and energy resources producing countries and quantify their marginal effects. The study applies binary choice logit model for panel data using pooled method. One feature of the research is that binary data set of occurrence of resource nationalism are sorted out by authors referencing U.S. Geological Survey’s reports. The results indicate that high-technology export (% manufactured export), ores and metals exports (% merchandise exports), rule of law (world governance indicator), trade (% GDP), and natural resource rent except forest (% GDP ) dominant the occurrence of resource nationalism for high and upper middle income group countries; government effectiveness (world governance indicator), policy perception index (The Fraser Institute), high-technology export (% manufactured export), and mineral rent (% GDP) dominant the occurrence of resource nationalism for lower middle and low income countries. According to our model, probability of occurrence of resource nationalism in 90 countries are predicted. Top 10 risky countries in 2012 are estimated to be North Korea, India, Honduras, Indonesia, Kazakhstan, Burkina Faso, Mongolia, Cuba, Bolivia, and Peru. The study is a primary trial of researching on resource nationalism and provides some insights for theoretical building and simulation on the issue.

Jan 1, 2017

By Zbigniew Hladysz

INTRODUCTION In the Polish coal mining industry, the Upper Silesian coal basin has an important position. It contributes over 98% of the total coal production of Poland which reached 193 mt in the year 1979. In view of the significant urbanized area in this region as well as the industrial potential, it is important to protect the surface by stowing the mined out underground workings. Approximately 18% of the total production is mined from longwall faces with stowing. However, caved longwall faces are most popular. In the upper Silesian coalfield, approximately 337 highly mechanized longwall faces are in operation. Out of these 337 faces, 301 longwall faces are caved. One of the main requirements for effective and safe coal extraction is a suitable method for strata control. We can divide the complex process of strata control into four steps: 1. Strata investigations 2. Selection of supports for roadways 3. Selection of supports for longwall 4. Rock bursts and other hazards protection STRATA INVESTIGATIONS Estimation of the structure and physico-mechanical properties of the rock mass surrounding the workings is an important constituent of strata control. These factors definitely influence the rock stability, support load, working conditions as well as the mining technology. Complex methods of strata investigations involve a set of indicators enabling the estimation of the stability of the roof rock, strength of the coal seam and load bearing capacity of the floor. The basis for the evaluation of roof stability for a coal seam is the classification according to the resistance to bed separation (1). The bed separation resistance is equal to the strength of the rock in tension perpendicular to the bedding plane. In order to properly classify a rock, it is indispensable to make continuous profiles of the bed separation resistance from the immediate roof up to a distance of three times the thickness of the coal seam. The profiles are developed by utilizing mine roof investigations with the hydraulic borehole penetrometer. (Fig. 1) The penetration resistance is determined by the critical pressure required to cause crushing of the rock by the penetrometer indentor (2). The classification of roof rocks and their ability to cave spontaneously during longwall mining is shown in [Fig. 2]. The measurement of the critical pressure also allows for the determination of the compressive strength of the rock, the index of workability and roof fissuration.

Jan 1, 1982