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By CHENCHEN SUN, GUOPING LUO, GUOCHENG ZHANG

In this study, the conditions of raw materials and fuels were simulated for Bayan Obo iron ore concentrate by adding pure calcium fluoride (CaF2) in various concentrations to Australian iron ore. The mechanism by which the fluorine (F) content of the lattice influenced the reduction swelling properties of the iron ore briquettes during various stages of the reduction process was investigated. The results provide insight into the mechanism governing the reduction swelling process in Bayan Obo ore briquettes, which could be used to direct real?world production practices, particularly those related to the rational utilization of Bayan Obo ore resources.

By T. Cyrul

The Polish underground mining has its long lasting tradition. High production of coal, that has recently been approaching 200 milion tons per year, put this small country among the bigest world producers of coal. To achieve such a high production, which mainly originate from very unfavourable mining and geological conditions, Polish scientists and engineers have to introduce new and original solutions to the mining practice. Many of the solutions on mining methods, ventilation, stability, subsidence etc., have had the world wide reputation, however, insufficient translations from Polish cause , that many of the recent Polish mining achievements are not known to foreign specialists.

Jan 1, 1986

By L. P. Meade

Dimension stone and salt are two of the oldest industrial minerals utilized. Salt has been and still is a necessity to the well being of man. Dimension stone on the other hand has been utilized by man to glorify conquests - both in the battlefield and corporate arena. Both commodities are important, but dimension stone has an additional use in that the survival lessons learned by the domestic industry can be applied to other contemporary industrial minerals, Specialization in the market place and customer service have allowed domestic producers to survive: subsidized foreign competition, obsolete equipment, and lack of capital.

Jan 1, 1986

By Mike S. Ness, Allan G. Provost

High speed drilling, mucking, and hauling equipment was used in driving approximately 2.16 km(7100 ft) of lower power tunnel in quartz diorite for the Tyee Lake Hydroelectric Project near Wrangell, Alaska. The .91 m(36 in.) guage rail mounted equipment included a Tamrock 2-boom electric/hydraulic drill jumbo, a Haggl and 8HR mucker , and 3 Hagglund 115C shuttle cars. Several other innovative techniques allowed maximum advance rates of up to 17.5 m/day(57ft/day) in the 3 m(10ft) horseshoe section. Average tunnel advance was approximately 11 m(day(35.4 ft/day). The primary difficulties preventing full utilization of the equipment potential were the operators' "learning curve", the need for complete retraining of all personnel in the new methods, and minor sections of faulted ground.

Jan 1, 1983

The response of 174 domestic water supplies to longwall mining of the Pittsburgh coal seam was compared to various physical parameters. Sixty-four percent of domestic water supplies returned to service without the need for intervention, while thirty six percent required intervention to reestablish a suitable water supply. Domestic well response is strongly correlated with the topographic setting. Valley wells showed the least effect while hilltop wells showed the greatest effect. Well response was also found to be correlated to the location of the well above the mining with greater effects observed in zones of surface tension and compression, and fewer effects in zones which are stress neutral. Ground water supplies remained unaffected or were re¬established at 149 of 150 sites, indicating that ground water resources remain available to domestic wells after mining. Results of this study support the stress-relief model of ground water flow in the Northern Appalachian Basin. Longwall mining's effect on this system is to locally increase fracture connectivity in the near surface zone. This may shift the zones of saturated fractures to greater depths beneath hilltops and hillsides, and increase recharge and storage in valleys. General trends in well response are predict¬able utilizing the stress relief conceptual model, the topographic setting of the water sources, and their location over the mine.

Jan 1, 1986

By Christopher D. Henry

Environmental geologic maps of the Wilcox and Jackson-Yegua lignite belts of the Texas Coastal Plain delineate land areas on the basis of their natural characteristics. Criteria used to define map units include substrate, soil, topography, geologic process, vegetation, and land use. The maps are useful in planning and reclamation of lignite mines and in meeting the requirements of State and Federal surface mining laws. Specific applications include identification of land capability, recharge areas and geometry of aquifers, flood-prone areas, areas that may qualify for prime farmland status, and other areas sensitive to lignite mining.

Jan 1, 1982

By E. J. Duggan

In the course of the grinding experiments conducted at Climax over the past twenty years one interesting phenomenon was discovered. This was that balls made of certain types of steel grind more ore than some others. The most significant variation was found in the results secured with a hard alloyed forged bail compared with the forged carbon ball supplied by most ball manufacturers These findings were confirmed in many repeated controlled tests. The value of these tests depends on the methods used, the facilities available and the care with which the investigations were conducted. These are described in the following. This testing has largely been done in eight 91 x 81 low discharge ball mills in closed circuit with 7811 duplex screw classifiers. The mills run at 20 RPM on a feed approximately minus 3/8 inch. The ore is ground through 28 - 35 mesh in one stage. Each mill and auxiliary classifier is in a separate, parallel grinding and flotation section The, ore to each: section is the same in every particular and is fed to each mill bin from a common conveyor tripper. The ore from the bin to the ball mill is weighed on a conveyor scale. The power input to each mill motor is determined with a watt hour meter which measures the power to the mill motor only. Both the scales and meters are checked periodically by standard methods and have been found to give consistent readings. Automatic samplers are employed on each section to obtain accurate measurement of the size reduction. A size analysis of the classifier overflow is made each shift and a composite size analysis is obtained from a weighted average of the various shift analyses. The mills are driven by 450 horsepower synchronous motors so that there is no speed variation and shell liner age is kept as nearly the same as possible in mills under test. The same set of operators is assigned to a mill under test as to the control mill. In all other particulars such as ball load, mill density, liner design, etc., the mills are operated in precisely the same manner. This is an ideal arrangement for plant testing. From observations of ball mill performance over the past twenty years, it is the opinion of the operating staff that variations of as little as one to two percent in mill capacities may be determined if sufficient operating hours are devoted, to a test. Relations between mill capacities, fineness of grinds and power consumptions have been established with a high degree of accuracy. In Table I are given the figures for one test. These show that while the grind with the hard ball was slightly coarser, the tons ground per hour was 5.4 percent greater with the soft ball, and 6.1 percent greater on the basis of minus 100 mesh produced. The power consumed per ton with the hard ball was 4.4 percent greater on a tons per hour basis. The soft ball was inferior in wearing qualities and steel consumption per ton of ore was 24 percent greater with it. In this test the mills were charged with the two different balls for a period of three months to allow the ball loads to come to equilibrium. In Table II are given the specifications of the two balls. The difference in grinding rates may be accounted for by the nature of the ball surfaces. The surfaces of the soft balls after being worn a while are rougher to the touch. Enlarged photographs of the worn-in surfaces of hard and soft balls are shown in Figure I. These show the presence of scratches or skid marks on the hard ball surface which indicates less nipping effect. The Climax ore pulp has a pH of 6.0 and is in a dispersed state. The viscosity is low compared with most ores especially those that are conditioned with lime. This would lower the tendency of the pulp to adhere to the balls with a lower grinding efficiency as a result. It was also thought that the relative rates of wear from surface to center might affect the make-up of an equilibrium ball charge. This probably has little effect on capacity as shown by the size analyses of the two ball charges in Table III. This hypothesis was subsequently investigated by the use of rationed charges. The rationed charge did not overcome the advantage in

Jan 1, 1958

By J. Weyer

"A lot of incorrect, dangerous and misleading statements about the effect of CO2 on the human body can still be found in the internet, the media and in books. It is a fact that already low concentrations can lead to critical reactions, higher concentrations cause a narcosis. The real effect is not a lack of oxygen but an inner suffocation. The breathing reflex is decreased and the transport of oxygen in the blood is reduced due to a low pH value of the blood. Furthermore a reduced oxygen content in the air can also lead to the failure of diesel engines. MOTIVE Different gases can appear in active mines as well in abandoned mines, adits and caves. The most dangerous gases are CO, NO/NO2, H2S, SO2, CH4 and CO2. Although the general danger arising from these gases is mostly known some aspects are underestimated. Furthermore misleading or wrong statements exist about the detection and the effect of gases on the human body. This is especially true for CO2. In the last years a couple of accidents happened with a great number of injured persons and unfortunately also some fatalities. As a result wrong information and comments about the effect of CO2 have been published in the media. A huge unexpected CO2 outburst in a potash mine showed again some additional problems and limits for rescue troops. ORIGIN OF CO2 AND MISLEADING STATEMENTS ABOUT THE EFFECT ON THE HUMAN BODYCarbon dioxide can appear as free gas in the earth crust. It is especially known in significant concentrations in some potash deposits, in hard coal mines and some caves. Furthermore it can be formed due to complete oxidation of carbon. It can appear in technical processes. It is also used for or in technical processes, as fire extinguishing agent, as cooling agent, it is contained (added) in sparkling water or other soft drinks and it is formed by fermentation processes. Up to today a lot of wrong information about the effect of CO2 on the human body is published or is still in the mind of many people and unfortunately even in the mind of members or leaders of rescue troops. On August 16th 2008 a faulty CO2 extinguishing installation in the city of Mönchengladbach/Germany caused the injury of 107 people and the evacuation of further 150 people /1/. People on the streets became unconsciousness and felt down. Fortunately all could be rescued due to the immediate rescue operation of local fire fighters. Furthermore the CO2 concentration on the ground was diminished by help of a helicopter. What could have happen with the engine will be discussed later. After 6 days a second similar accident took place /2/. In the news members of the rescue teams explained that CO2 leads to suffocation due to a lack of oxygen. This is wrong! Also cave explorers often say that a burning candle can detect a low oxygen and/or high Carbon dioxide content in the air. This is also wrong and deadly dangerous! Similar statements we find nowadays in the internet /3, 4 and many other/. In a forum “science and mathematics > chemistry” several people say that winegrowers go with a candle into the vine-cellar to detect CO2 /5/. Again: this can be deadly! Another dangerous statement is that CO2 in higher concentrations leads to headaches so people should leave such areas. A last example found in the literature is that at 3 % the breathing volume is doubled and at a concentration of 20 % one can felt some warmth on the skin. Both is not wrong but can lead to false conclusions. /6/"

Jan 1, 2015

By H. C. Lautenschlaeger

Let's start with a bit of History. Before the advent of woven wire screen cloth or perforated plate as we know it today, screens or sieves, as they were called, were probably made by the Greeks or Romans around the year 150 B.C. Coarse openings were made from bamboo or other woven reeds or with holes punched in leather hides, while fine openings may have been made using hair from the long tails of horses woven with small openings. The first metallic woven wire screens were probably produced by the Germans in the 15th Century. All of these screening devices were, of course, hand operated. The first records of mechanically driven shaking screens are found in "John Smeathon's Diary of His Journey to the Low-Country" in 1775. He was the English Civil Engineer who built the famous Eddystone Light House and discovered the formula for making hydraulic cements. He described a screen the Dutch were using as a wooden frame on which woven wire was mounted. This box was inclined at an angle and hinged on the lower end. The upper or feed end was equipped with a pulley so they could raise it up, say 5" or 6", and then let it drop abruptly onto a sill or stop plate, thus jarring the material deposited on the woven wire through the openings. Material that was passed over the deck was scooped up and redeposited on the woven wire for rescreening. This was an early form of what is today known as a recirculating load.

Jan 1, 1983

By A. Moergeli, Philip Sander, John Reilly

"SUMMARY While the basic elements of risk management, including probability, consequences, risk registers, mitigation measures, etc., are now well understood, the process to include correlation, dependencies and linkage of risks and risk scenarios is less well defined and not well understood. To perform accurate and complete risk analysis and risk management, it is necessary to include correlation, dependencies and linkage between risk events, as well as risks that may occur multiple times. In this way, owners and contractors can more accurately determine risk-based costs, risk impacts and risk mitigation strategies. This paper will outline methods to deal with correlation, dependencies and linkage and will consider risks that may occur multiple times. Practical result comparisons – with or without these elements – will be presented. INTRODUCTION We believe the reader is familiar with basic concepts of risk, risk management and mitigation and the use of probabilistic cost-risk processes versus deterministic ones (Reilly et al. 2015; Sander et al. 2015). The probabilistic approach, compared to the simpler and more common deterministic approach (unit prices times unit costs plus a contingency), offers more useful information with respect to the range of probable cost as well as cost “drivers” and better quantifies the effects of risks, opportunities and variability – which improves understanding, leading to a better potential for profit (or loss) for contractors and added value for owners. In this context, a valid and sufficient quantification of correlation, dependencies and linkage of risk events, plus the impact of risks that may occur multiple times, is essential. Components of Cost Estimates – Base Cost, Risks and Other Uncertainties The components of cost that need to be correctly addressed in an estimate include (Moergeli et al. 2015): •,Base costs – the costs that will result if “all goes according to plan” (Reilly 2004) •,Risk costs – the resulting costs of threat and opportunity events, if they should occur •,Escalation costs – costs resulting from normally expected inflation with variability •,Other uncertain costs – costs that result from other events, normally external to the project team’s control, which may include unanticipated events, politically related changes and “black swan” events (Talib 2007)"

Jan 1, 2016

By Tomek Ulatowski

This article discusses four principal areas relevant to financing direct reduction facilities: (1) Lenders' differing requirements with respect to projected cash flows; (2) The impact of leveraging on project viability; (3) The importance of appropriate debt structure; (4) The significance of accurate and complete capital cost estimates. The overall findings emphasize the inseparable connection between the project economics and its financeability, and particularly how direcly intertwined they both are in the project planning.

Jan 1, 1978

By Andrew Hall

Many Latin American countries are facing a scarcity of water. As such, infrastructure decisions are quite different from those made in parts of the world that experience a positive water balance. In the latter case, the water treatment approach tends to be ?treat and discharge.? For Latin American regions facing the challenges that go with a negative water balance, the focus is on resource optimization and reuse. Historically, the water challenge has had a significant impact on economic development in Latin America, especially in sectors such as mining, where water usage is high. At the same time, countries such as Chile and Brazil are major development targets for mining and oil and gas operations. Given the water supply challenge, industry is increasingly turning to technologies and processes that maximize water recovery and reuse. With sulfide precipitation and ion exchange water treatment processes for example, it is possible to treat and recover more than 99 percent of water for reuse onsite. These technologies have been applied successfully in other regions of the world where water conservation practices are essential to economic survival.

Jan 1, 2012

By Louis W. Cope

The Compañía El Zapote Yacimiento Y Minas, S.A. has an ore body containing 650,000 tons of 0.185 oz/t gold ore in Mexico. Metallurgical testwork has been done to determine the response of this ore to several possible processing schemes. The paper describes the rationale for selecting the Silver State Mining Co. methods in Colorado. Plans for developing the mine and building the treatment plant are described in detail in the paper. Estimates of capital and operating costs are included.

Jan 1, 1984

By Eugie Kabwe

The velocity of detonation (VOD) is a significant property considered when rating an explosive, and it is quantified as a confined or unconfined velocity. The confined velocity is more significant as explosives are usually used under a definite degree of confinement. This study evaluates the stepwise increment of the air-deck volume from 10 to 30 percent, and its effect on the VOD. The VOD estimation in the 172-mm-diameter explosive column was conducted using the Dáutriche technique. The air-deck volume increment has an attenuation effect on the steady-state VOD, and detonation failure is high at 30 percent air-deck volume. This attenuation effect is directly linked to the explosive’s rating and efficacy. The air-decking approach in this study is different from conventional air-decking techniques in that it does not employ the fixed blasthole parameters, air-deck volume and specific VOD. 

By José Ricardo Lopes, Alaor Coelho, Marco Gomes, Alfredo Dacio Moraes Filho, Akira Koshima

"Very low strength alluvial peat soil was found under two old drainage galleries with just 4.3m cover above a twin tunnel due to be excavated by a 10.6m diameter EPB Shield for São Paulo Metro’s Line 5. Alignment was required to strengthen soil and drive the TBM through safely without damaging the galleries. The design included six levels of self-drilling forepoling with lengths up to 15m, using 100 mm-diameter SCH160 metal tubing and injection bulbs with estimated 0.20m diameter. Two 6m-diameter circular shafts were excavated along the shield-tunnel axis, one each side of the galleries, and forepoling fanned out under gallery foundations. Given the peculiar soil and confined working space, more data were needed for correct drilling geometry. Ground mass treatment was successfully designed and executed and galleries were fitted with instruments to enable the shield’s advance. DESCRIPTION São Paulo Metro’s Line 5 (aka Lilas or purple line) is adding 11 stations along an 11.5km extension and three EPB TBMs are being used simultaneously (three EPBs on the same job for the first time in Brazil) with one of them excavating a large cross- section twin-track tunnel. Currently the largest work-in-progress for São Paulo Metro, this project has been divided into seven lots and 9km are already operational. This study refers to Lot 6 where the 10.6m - diameter EPB shield excavation is only 4.3m below two galleries running through a 10m layer of very soft peat soil in an old alluvial riverside region ringed by major roads. After recent filling, this area (Parque das Bicicletas) was used for recreation, although temporarily it has become a construction site. This paper will describe the original basic design; precautions in relation to the structural condition of the galleries after inspection; the problem of absence of data for their foundations; subsoil bore tests; evolution of the engineering design for the galleries and conditioning and reinforcing the soft soil below the galleries to ensure safe advance of the EPB shield, and finally the successful outcome of the solution used."

Jan 1, 2016

By S. A. Saki, J. F. Brune

"INTRODUCTION Longwall coal mining leaves large areas where the coal has been made removed and the roof rock strata collapse, forming a zone of broken rock rubble called the gob. Figure 1 shows a typical longwall gob area along with the gate roads. The ventilation pattern for progressively sealed longwall panels follows a simple “U” pattern where fresh air is coursed inby to the headgate, flows along the face and exhausts through the outby tailgate as shown in figure 1(a). An important variation of this pattern is the back return (BR) arrangement where the exhaust air from the face is drawn inby and around the nearest open cross cut before it turns in the outby direction towards the exhaust fan. Figure 1(b) illustrates the use of back return. This arrangement moves the point of low pressure from the tailgate corner up to 60 m inby and thus maintains fresh air in the tailgate region that could otherwise be contaminated with gob air.The gob area may contain remnants of unmined coal or parts of overlying coal beds that continue to release methane, eventually filling the gob area with methane in concentrations far above the explosive range of about 4.5 to 15%. Many gob areas must be equipped with gob ventilation boreholes (GVBs) to extract methane, and GVBs often exhaust methane at concentrations from 50% to 90% (Saki, 2016). Due to oxidation processes occurring in the gob, the oxygen content is reduced to a low level, with nitrogen and CO2 making up the major remaining components of the gob atmosphere. FORMATION OF EXPLOSIVE GAS ZONES IN GOBS Since the longwall face area is ventilated with fresh air below 1% methane and the face and gob areas are not separated, an explosive fringe will form where the methane content lies within the explosive range and oxygen content remains above 12%. Figure 2 shows a typical development of such an EGZ. This figure is based on a computational fluid dynamics (CFD) model developed by CSM researchers to analyze gas concentrations and flow patterns in longwall mining. Figure 2(a) shows the formation of EGZ in the gob with a U type ventilation scheme, where EGZ lies right behind the shields in the tailgate corner. Figure 2(b) shows the formation of EGZ in the gob combining U type ventilation scheme with BR, where EGZ is pushed away from the face deep into the gob. The CFD modeling parameters and boundary conditions have been verified with field data from two cooperating, active longwall mines (see Worrall 2012, Marts 2015, Gilmore 2015 and Saki 2016). Other mine geometries, methane inflow rates and gob permeability distributions can be modeled to establish representative gob atmospheric conditions. Two GVBs were operating in the model, extracting 0.165 m3/sec each. The methane in the working areas and returns was kept below 1%. Methane flowing into the model from a rider coal bed above the mined seam was at the rate of 0.55 m3/sec."

Jan 1, 2017

By M. J. Hrebar

Surface coal mine design has traditionally relied on graphic and analytic approaches for pit layout and equipment selection. A number of interactive graphic microcomputer programs have been written which aid in the design process in the academic arena and should also have industrial applications. The programs described include a dragline cut diagram and production index calculation program, a downslope load scraper cut diagram and volume program and an overburden volume and coal tonnage sequencing program.

Jan 1, 1985

By William Gleason

"More than 6,300 people converged on the Colorado Convention Center for the 2017 SME Annual Conference and Expo and 119th National Western Mining Conference in Denver, CO on Feb. 19-22. Many of them crammed in to hear Douglas Silver deliver the keynote address to the conference.Silver is a portfolio manager for Orion Mine Finance, a private-equity fund focused on providing funding to advanced-stage base and precious metal projects and is one of the most respected voices in the field of mineral economics. Prior to joining Orion, he served as chief executive officer and chairman of International Royalty Corp., a global mineral royalty company, which he founded in 2003 and sold in 2011.Those who were hoping that Silver would deliver at least a bit of optimism during his 90-minute presentation got what they came for from the talk titled, “When are commodity prices going to rebound?”It marked the second time Silver has presented the keynote address to SME, the first was in 2008 and was delivered during the height of mining’s super cycle (ME, June 2008). In his 2017 address, Silver looked back on the previous 10 years and the massive contraction of the global economy that resulted from the great recession that began near the end of 2008.It has been a challenging time for the mining industry. About US$1.4 trillion was lost in the global mining stocks from 2011 to Jan. 6, 2016. Major mining companies exceeded $60 billion in write downs between 2012 and 2013 and investors lost confidence in the sector, putting the global mining industry into a bear market that has taken mining equities to historic lows.However, that was then and this is now.Using numerous examples, including rising commodity prices, a steady decline in the U.S. unemployment rate, increases in discretionary income and the Dow Jones Industrial Average, which topped the 20,000 mark for the first time ever in February, Silver theorized the current down cycle is near its end and the demand for metals and other commodities will see a sharp increase by 2025. He also noted that investors are beginning to rotate back into mining equities."

Apr 1, 2017

By A. M. Marabini, V. Alesse, Belardi. G.

An alternative flowsheet was designed for the flotation treatment of a complex sulfide ore from the Sotiel Mine in Spain. The ore contains 0.71% Cu, 2.24% Pb and 5.63% Zn. Two specially developed synthetic collectors, methyl-mercapto-benzoxazole (MMBO) and 6n-propoxy-mercapto-benzo-thiazole (PMBT), were examined. MMBO exerts a specific action on copper and zinc minerals after treatment with copper sulfate, and PMBT exerts a specific action on Pb minerals. Flotation operating variables (pH, frother type, frother quantity and feed particle size) were examined by means of rougher flotation tests to determine the optimum conditions for the new collectors. Once the optimum conditions were determined, a series of open flotation circuits were run on feeds of various particle sizes (obtained by different types of grinding). The objective was to obtain high-grade Cu and Zn concentrates. The results of the open-circuit tests demonstrated that a Cu concentrate grading from 18% to 23% Cu and a Zn concentrate grading from 40% to 48% Zn can be produced.

Jan 1, 1996

By Petr Salak, Adrian St. John, Angelos Gakis

"INTRODUCTIONCrossrail will provide London and the South East of England with a world class, high-capacity railway to ease congestion on London’s public transport system and enable better access between business, residential and entertainment districts. At the heart of this £14.8bn scheme lies Farringdon Station, which will form a major interchange between Crossrail, Thameslink and London Underground. The £400m Farringdon Crossrail station was awarded to a joint venture of BAM Ferrovial Kier (BFK) in 2011, and comprises two ticket halls, two platform tunnels and a multitude of connecting tunnels all constructed using open face sprayed concrete linings (SCL). BFK appointed Dr. Sauer & Partners (DSP) as their specialist SCL designer. As the main contractor for both C300/C410, the Western Running Tunnels and Station Caverns, and also for C435 Farringdon Station, BFK were in a unique position to develop strategies to reduce cost, time and risk for the Client. One such innovation involved the continuation of the TBM drives for the running tunnels right through the length of the new Farringdon platform caverns. This created large diameter precast concrete pilot tunnels for the subsequent platform enlargement using SCL. The benefits of such an approach are described in detail by St.John et al 2015. BFK also introduced another alternative strategy to reduce cost, time and risk, by proposing to abandon the TBMs in the ground (“Turn & Bury”) permanently rather than recovering them through the ticket hall shafts. This de-risked the programme, enabling critical ticket hall construction to proceed unhindered. However, one consequence of this revised strategy was an area of increased underground congestion, with two SCL tunnels (RTE2 and ES2) and a bored tunnel (complete with abandoned TBM) in close proximity to a ticket hall excavation (see Figure 1) and a sensitive, listed railway structure. Faced with this complex geometry, and combined with challenging geotechnical conditions (Gakis et al 2015), the team chose to install enhanced monitoring to study the behavior of tunnel RTE2 and provide additional assurance that the tunnels were performing as predicted. Applying advanced 3D numerical modelling and taking into account the residual tensile strength of the SCL helped avoid unnecessary reinforcement installation in primary lining and/or early installation of a secondary lining in RTE2 prior to ES2 construction."

Jan 1, 2016