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By T. R. Jr. McMillan

Introduction Examining the short- and long-term job prospects for engineers in the coal industry might include looking at coal tonnage projections, future export markets, federal regulations, and the decrease in overall graduates. But coal is the US most competitive basic industry. As such, why not go back to basics? That is, there are three basic challenges that need to be faced by students, faculty, and members of the coal industry. These challenges are counseling, career placement, and professionalism. Counseling Counseling can include elementary, high school, and college students, as well as individuals already employed. But what happens to students after they have selected a course of study at a particular university? As shown in Fig. 1, only 87,000, or 7.25% of our graduates have technical degrees. Generally, there is a strong market projected for these engineering graduates. However, many students who have majored in other nontechnical curriculums, have to scramble for jobs. This says something about our ability to make students aware of where the real job opportunities are. As a student spends four or five years pursuing a degree, he or she is looking for professional guidance. The student has the right to expect "real world" counseling - counseling that is not "the way it should be" but "the way it is." The influence of faculty members is significant. They should take this long opportunity to tell students not what they want to hear or what the problem's of academia or the industry are, but what the real job market is all about. If faculty do not use this opportunity, they in-advertently-through omission - mislead their students. Once a student graduates and is a working alumnus, faculty should take advantage of their relationship with the student and continue to stimulate conversation leading to a two-way exchange of ideas and information. Faculty should also encourage and solicit financial support for their mining departments from their alumni. These monies, in many cases, will be matched dollar for dollar or more, depending on the company the alumnus works for. In the private sector, the responsibility is to communicate with faculty and students. Alumni can be effective by participating in this two-way dialogue with their professors at meetings, technical seminars, and conventions. In many cases, alumni will employ summer or co-op students in their organizations. While getting to know these students, industry members should level with them on where the true opportunities are and what it takes to be successful. It is important to communicate with both faculty and students candidly on both the posi-

Jan 2, 1985

By Andrew Scogings

The current edition of The Australasian Joint Ore Reserves Committee (JORC) Code was published in 2012 and, after a transition period, the 2012 edition came into mandatory operation on Dec. 1, 2013. There is a significant change between JORC 2004 (Clause 44) and JORC 2012 (Clause 49) for the reporting of industrial mineral resources and reserves, which should be addressed by ASX-listed players in the industrial minerals space.

By Felicia F. Peng

One of the serious environmental problems related with the extraction of coal for carbon and energy resources is that upon preparation of coal a large quantity of fine coal has been discarded and/or lost to tailing impoundments. These problems present hazardous conditions to the local community. Also, the precious heating value of energy resources has been wasted and Left unrecovered in the tailing impoundments. Both RCR and SMRC ACTs recognize and mandate an investigation into slurry impoundment problems, including consideration of potential use of those coal fines in the tailing ponds. Bituminous coal producing district 46 encompasses the northern panhandle of West Virginia. The major producing seam in this district is the Pittsburgh coal, 1-7 meters thick. 75 percent of the coal producted in this district is deep mine. This district produces approximately 3 million tons of coal waste materials annually. One of the coal preparation plants in the district which we have visited has been processing Pittsburgh too. 8 seam coal for the past ten years. The characteristic data of the Pittsburgh raw coal is shown in Table 1. The raw coal produced in this district is characterized by its high heating value, high ash and high sulfur contents. The coal preparation plant flowsheet designed and used to process this Pittsburgh raw coal prior to 1979 is shown in Figure 1. It was a partial coal cleaning plant' with 1 092 mt/hr designed capacity, which consisted mainly of a coarse coal cleaning circuit. The rejected fine particles in the size range of -600µm which consisted of vorsiv underflow and cyclone underflow from clean coal streams and spiral classifier overflow from refuse stream were settled down in a thickener with the aid of anionic flocculant prior to being pumped to the tailing ponds for disposal. Figure 2 shows that the same coal preparation plant in Figure 1 was modified to a semi-complete coal cleaning plant and expanded its designed capacity to 1 820 mt/hr, when market of coal fines becomes feasible in 1979. Tabling in the clean coal circuit and thermal dryer in the dewatering circuit were added to the flow sheet. The purpose is to recover more coal fines, reduce more pyritic sulfur and ash contents in coal and also to reduce solid waste material to be stored into the slurry impoundment, giving them a Longer Life. The rejected fine particles fed to the thickener are clean coal fines from two cyclone overflows and the fine refuse from the rufuse cyclone overflow. The clean coal fines presently lost to the tailing impoundments are in the size range of -150 µm and constitute about 5 percent of the overall plant feed. Total amount of tailing waste material accumulated in a tailing impoundment is estimated at 1.3 million metricton for the past ten years.

Jan 1, 1982

By Marco D. Boscardin, Paul A. Roy, Kevin J. DiRocco, Andy J. Miller

The North Shore Connector Project for the Port Authority of Allegheny County involves TBM mining a pair of subway tunnels through soil and rock under the Allegheny River and a narrow city street. Along the tunnel alignment are a historic building on shallow foundations and modern buildings on deep foundations, one constructed directly over the alignment during the latter phases of design. This paper provides an overview of the general site conditions, and technical basis for excavation support and tunneling decisions. Deformation limits, ground improvement, monitoring and mitigation plans, geotechnical baseline report development, and risk management will also be discussed.

Jan 1, 2007

By Aram Grigoryan

This paper addresses historical aspects and construction sequencing of the subway complex under Columbus Circle in Manhattan; the structural elements of the rehabilitation and new construction; and the challenges associated with design and construction. PB is providing engineering services to New York City Transit (NYCT) for the rehabilitation of the 59th Street/Columbus Circle Station Complex that services over 150,000 customers daily. The project involves structural repairs, modifications and new construction requiring underpinning and temporary supports, custom framing details, and construction staging procedures to meet stringent limitations within the operating transit station and around the Columbus Circle street intersections.

Jan 1, 2008

By Erika Moonin, Jim Nickerson, Claudio Cimiotti, Roberto Bono

"In response to the severe drought on the Colorado River basin and in order to preserve existing water capacity to the Las Vegas Valley, the Southern Nevada Water Authority contracted a new deep-water intake (Intake No. 3) located in Lake Mead. The current project (Contract No. 070F-01-C1) includes 5 km (3 miles) of tunnel with very difficult geological conditions and a 200- m (650-ft) deep shaft and marine works. This paper will present the current status of the design-build contract being constructed by Vegas Tunnel Constructors and the challenges and problems faced and the innovative solutions developed to handle the difficult conditions encountered during tunneling with up to 15 bars of pressure.ProjectbackgroundThe Las Vegas Valley receives the majority of its water from Lake Mead, which is located approximately 30 km (20 miles) east of the Las Vegas, NV metropolitan area. Due to the severe drought that has hit the southwest region of the United States, the water level in Lake Mead has receded from its high water level of 372 m (1,221 ft) above mean sea level (amsl) to a low of 330 m (1,076 ft) amsl in June 2015. Should the lake level continue to fall, at elevation 320 m (1,050 ft) amsl, the current water intakes will not be able to draw enough water to meet the needs of the local area. The risk of losing water capacity has prompted the construction of a new deeper intake. Not only is the new Intake No. 3 situated at a lower elevation in the lake at 262 m (860 ft) amsl, the new Intake No. 3 is also located to draw better quality (Fig. 1).Project challengesThe project has had several difficult challenges to overcome:• The work consisted of a 1.2 kt (1,300 st) structure constructed on a barge and lowered 100 m (330 ft) into Lake Mead anchored with 9,200 m3 (12,200 cu yd) of tremie concrete.• The drill-and-blast starter tunnel was impacted by three inflow events, resulting in a one-year project delay.• One of the main challenges was selecting the tunnel boring machine (TBM) and excavating the tunnel with expected hydraulic head pressure of as much as 17 bar (16 bar was the highest pressure recorded during the drive), crossing faulted areas, low rock cover and the risk of tunnel instability due to direct connection with the lake.• Extensive pre-excavation grouting with a constant head pressure ranging from 12 bar to 15 bar.• Structural repair of the cutterhead in difficult hydrogeological conditions [water inflow of approx. 800 m3/hr (4,000 gpm)].• Complete repair of the cascade sealing system for the main bearing and two replacements of the pinion bearings.• The TBM approach to the intake structure."

Jan 1, 2015

PolyMet Mining is developing the NorthMet property near Duluth, Minnesota. Laboratory investigations had led to the development of the PLATSOL process to dissolve in one step the base metals (copper and nickel) as well as the gold and PGM’s. To complete the pre-feasibility study, a fully integrated ten-day pilot plant trial was undertaken, comprising of: high temperature (>220ºC) pressure oxidation in the presence of 5-10 g/L chloride (the PLATSOL process), followed by solid/liquid separation, gold plus PGM’s recovery from solution, conventional Cu SX/EW and recycling of the copper raffinate to the autoclave. The concentrate tested was a NorthMet bulk flotation concentrate assaying 14.7% Cu, 3.05% Ni, 0.14% Co, 26.7% S, 1.4 g/t Au, 2.2 g/t Pt and 9.9 g/t Pd. Laboratory results were fully confirmed and with minor adjustments of the laboratory PLATSOL® conditions, the following leach extractions were obtained during the pilot plant trial: Cu 99.6%, Ni 98.9%, Co 96%, Pd 94.6%, Pt 96% and Au 89.4%.

Jan 1, 2001

By R. K. Sinha, B. S. Choudhary, Desh Deepak, A. K. Mishra, Hemant Agrawal, Shankar Kumar

There are several methods (empirical, statistical, and machine learning tools) to calculate blast-induced ground vibration. Still, due to complications in the blasting procedure, under varying blasting loads and strata conditions, it is not easy to predict and simulate blast vibration precisely. Therefore, a study was conducted to simulate the field blast data in Ansys software using explicit dynamics. For this study, monitoring of ground vibration for 20 single hole blasts was carried out. The density of emulsion explosives was in the range of 0.9 to 1.15 g/cc. In the laboratory, rock properties were determined from the rock sample collected from the mine site before blasting. The in-hole velocity of detonation (VoD) and the density of the emulsion explosive were also determined. These parameters were used for numerical analysis to know the ground vibrations at specified points. The results of ground vibration predicted by the model are validated using field data.

By James J. Kabat, James A. McDonald

Impregilo/SA Healy JV recently completed this Project using the first slurry shield TBM’s in the United States. The Project used two TBM’s to mine 18,000 feet in sands, gravels, and silty alluvial materials under the Willamette River and downtown Portland, Oregon. This paper discusses alignment and geological conditions, equipment selection and plant setup, and tunnel excavation means and methods, parameters, and results. Extensive hyperbaric operations were required and will also be discussed.

Jan 1, 2007

By H. Sis, D. Dahlin, S. Chander, C. Summers

Bench-scale selective-flocculation tests were conducted on samples of Florida and Western phosphate process tailings. Physical, mineralogical, and surface characteristics were determined for both types of samples. The flocculation tests investigated dispersant and flocculant types and doses, pH, and slurry percent solids, while other parameters were held constant. Where selectivity was achieved, phosphate minerals remained dispersed, whereas silicate minerals flocculated and settled. In single-stage tests, flocculants having low to medium anionic character effectively upgraded products at moderately elevated pH. Multiple-stage tests, and tests in which flocculants of lower molecular weight were used as site-blockers, gave improved results.

Jan 1, 2002

By K. Oraee

Zarshuran gold deposit, with the total reserves of some 12.5 million tons of 4.18 g/ton ore, is considered to be an important gold mining project in the area. In this paper the feasibility studies of the whole project is carried out on the basis of several economic variables. Given that mining data are often of uncertain nature, these economic variables have therefore been estimated under the conditions of uncertainty. The resultant Net Present Value is hence also obtained under the same conditions. For this purpose, a model is first devised with the help of Excel and COMFAR software. The model is then developed that considers different scenarios which would result in different expected values for the economic variables. It is concluded that the NPV of the project is most sensitive to gold and silver price and that other variables such as discount rate, operating and capital cost all affect the feasibility of the project with lower degree of severity. Finally, risk analysis is also carried out using Mont Carlo technique, in order to estimate the most probable value of NPV. The average NPV calculated in this way is US$ 49.7 Million, whilst without due consideration of risk, this would be US$ 36.6 Million. The techniques used, together with the procedures adopted in this paper, can be used in feasibility studies of all mining projects. Such decision would result in more accurate Net Present Values than expected from other frequently used methods.

Jan 1, 2011

By C. D. Hebert, M. R. King

The 56,000' (17 km) long San Vicente Aqueduct Pipeline tunnel is being constructed using precast concrete rings to act as preliminary ground support through two sections of the bored tunnel with lengths of 9,450' (2.9 km) and 33,700' (10.27 km).The six segment bolted trapezoidal ring was manufactured using a combination of steel fiber reinforced concrete and self compacting concrete in vertical moulds. This paper briefly describes the design and function of the segments, and reviews the development stages of the concrete mix, and the advantages and disadvantages of the adopted manufacturing method.

Jan 1, 2007

By C. P. Kelley, T. J. McKeon

Several recent developments in fine screening technology have been implemented at the DuPont Starke, Florida plant allowing enhanced zircon recoveries while minimizing operator requirements and total operational costs. The total design concept came about through the efforts of engineers at Derrick Corporation (Buffalo, New York), DuPont Titanium Technologies (Starke, Florida) and Roche Mining (Carrara, Australia). The use of the Kelsey Jigs for zircon recoveries from the tailings stream requires two wet sizing functions in order to operate properly. The first wet sizing is required on the initial mineral slurry feed to the Kelsey Jig. This sizing is intended to protect the Kelsey Jigs internal screen basket from plugging with nearsize particles, thereby keeping production rates maximized. The second sizing function is intended to recover properly sized garnet ragging material, which inadvertently ends up in the tailings stream leaving the Kelsey Jig. The unique machine design developed by the three partners in this project incorporated both wet sizing functions (protection and garnet recovery) into a single patented high capacity wet screening machine fitted with patented screen surface technology. This screen surface technology allowed for high capacity slurry handling capabilities at separations as fine as 230 microns while experiencing no nearsize blinding and extremely long screen panel life. The high open area urethane screen surfaces utilized in the application typically last 20 to 30 times longer than stainless steel wire surfaces. The stacked machine design minimized total equipment requirements and screen footprint requirements, and reduced power consumption and overall installation costs.

Jan 1, 2005

By S. G. Malghan, J. P. Van Dillen

Introduction Some uranium minerals are paramagnetic and hence are amenable to concentration by high gradient magnetic separation (HGMS). This paper describes effects of the HGMS parameters-pulp velocity, field strength, matrix loading, and magnetic field gradient-on the product recovery and grade. Unsatisfactory separation of uranium minerals by HGMS is related to ore-specific properties, such as lack of liberation, fine dissemination of uranium minerals, uniform distribution of magnetic minerals throughout the ore matrix, and interference of fine-sized slimes. Experimental techniques to identify and resolve some of these problems are outlined. HGMS of Uranium Ores The mechanism by which uranium minerals are attracted to a magnetic field is either due to its magnetic susceptibility or its association with other minerals that are magnetic. Data on magnetic susceptibility of uranium minerals are scarce. The only reported data are for uraninite at 2360 X 10-6 cm3/mole. Povarennykh (Andres, 1976) concluded that the magnetic properties of minerals depend on: • Structure of the outer electron shell in a mineral with electropositive atoms; • Valence of the atoms; • State of the chemical bonds; • Type of coordination; and • Proportion of magnetic atoms (Fe, Mn, Cr, and Ni) in the composition of the mineral. However, information on the magnetic susceptibilities of the constituent atoms of a mineral alone does not suffice for evaluating the mineral compound as a whole. Most often, uranium minerals can be beneficiated by HGMS if they are associated with other minerals that are magnetic. This appears to be a more predominant mechanism by which the uranium minerals are beneficiated. Experimental A Sala-HGMS (Malghan and Subramanian, 1981), model 10-15-20, separator was used in the experiments. The matrix material-ferromagnetic stainless steel in the form of expanded metal or steel wool-was packed into a 38-mm (1.5-in.) diameter by 360-mm (14-in.) long canister. The matrix material occupied only a 150-mm (6-in.) length. The experimental set-up and slurry flow direction are described elsewhere (lannicelli, 1976). The response of uranium ores in the HGMS was studied by feeding well-dispersed slurry at 10% solids and examining the influence of process variables on selectivity and overall uranium recovery. The chemical and mineralogical characteristics of the ores under study are presented in Table 1.

Jan 12, 1983

By Bruce Watzman

"Few issues are more important to the National Mining Association (NMA), the U.S. mining industry and NMA’s MINExpo International 2016 exhibitors than safety.Global mining safety and health is a journey necessitating continuous improvement, collaboration and innovation on the part of both mining operators and their suppliers.MINExpo 2016, which takes place Sept. 26- 28, 2016, in Las Vegas, provides attendees with the opportunity to view technologies to help refine management of mining safety and health, utilizing NMA’s CORESafety system. CORESafety ‘One of the best’Launched by NMA in 2011 and moving forward ever since, CORESafety is driving continuous improvement in safety and health performance among participating industry companies by shifting from a command-andcontrol regulatory approach to a risk-based systems approach built on the Plan-Do-Check-Act model (Fig. 1).Considered an exemplary safety and health management system, NMA’s CORESafety system helps mining operators change their approach to safety and health management by enhancing the safety and health culture throughout their organizations. Although it is challenging to consistently and completely control all the factors and variables occurring in daily mining operations, experience has shown that applying systematic controls to as many variables as possible is the most successful approach for improvement in mining safety and health.When embarking upon the development of the CORESafety framework, NMA’s leadership set an ambitious goal to eliminate fatalities and reduce the injury rate 50 percent in five years, or the “0-50-5” goal. While the goal has not been met yet, the steady progress has been extraordinary with fatalities among participating companies dropping 45 percent during the period 2011-2015 (Fig. 2). Data also demonstrate that, as participating companies increase their level of implementation, total injury rates have also declined (Fig. 3).In a September 2015 interview with NMA, Penn State University mining engineering Professor Jeffrey Kohler praised CORESafety as “an inspired and timely program that brings together key elements to achieve safety and health goals.”"

Sep 1, 2016

By Hyung-woo Kim, Kiyoung Sung, Sup Hong, Jung-Yeul Jung

Many concepts for the commercial production of deep-seabed manganese nodules have been studied since the 1970s. However, the bearing capacity of the deep seabed is not strong because it is composed of fine particles with high moisture content. So it is impossible to carry manganese nodules in the collection system. Therefore, the validity of continuous mining by riser pipe from the seabed to the vessel is highly appreciated. A continuous mining system is composed of mining vessel, lifting pipe, buffer system, transport tube (flexible pipe), and self-propelled mining robot. A conceptual diagram of this system is shown in Fig. 1(a). Korea Research Institute of Ships and Ocean Engineering (KRISO) developed a deep-seabed self-propelled mining robot called "MineRo" to collect manganese nodules in 2012 (as shown in Fig. 1(b)). In 2013, real sea experiments at around 1380 m depth were carried out to evaluate the collecting and driving performance of MineRo. However, we found that the roller in MineRo did not work well at times. To elucidate the problem, we analyzed the rheological characteristics between the bushing and drive shaft under deep-water conditions.

Sep 1, 2014

By William A. Gibson, Kenneth P. Neumann

In 1967, development of the Cyprus Thompson Creek molybdenum deposit began near Challis, ID. The first mining claims were staked on an intrusive rock out-crop. Exploration continued for 14 years. In 1978, the decision was made to develop the deposit. In Dec. 1980, approval was received for the environmental impact statement and facilities construction and waste rock removal began. By the middle of 1983, 126 Mt (139 million st) of rock had been removed and all facilities completed. Location The Thompson Creek project is located about 58 km (36 miles) southwest of Challis in Custer County, in south central Idaho. The mine and mill are situated between 2.2 and 2.6 km (7,217 and 8,530 ft) in elevation. The project is located in an isolated area. Surrounded by mountains, it is adjacent to the Sawtooth National Recreation Area. The Salmon river is 8 km (5 miles) south of the project. The project claim block is lo-

Jan 1, 1984

By T. Burchett, F. Stanley, K. McGough, G. Luttrell

The vast majority of U.S. coal preparation plants utilize screen-bowl centrifuges to dewater their fine clean coal products. In light of this popularity, researchers at Virginia Tech have engaged in a variety of laboratory and industrial field test programs to develop technological enhancements that have the potential to further improve the performance of this important solid-liquid separation process. These enhancements, which include simple design modifications and new reagent packages, have been shown to significantly improve solids recovery and reduce product moisture in several experimental trials.

Jan 1, 2006

Queensland?s underground coal industry, as a whole, has arguably the best gas monitoring systems in the world. Each mine utilizes real time, tube bundle and onsite ultra fast gas chromatograph systems. Queensland?s mining legislation has specific requirements for mine gas monitoring but there is no requirement for all three techniques. Industry has however identified the need for all three and adopted this as a standard, resulting in over sixty thousand gas results collected each day. Automated monitoring systems are programmed to alarm for gas concentrations, gas ratios and explosibility. These alarms are then used to initiate predetermined actions to take control of the situation and prevent the compromise of safety to workers and the loss of resources. Dedicated software packages have been developed to assist in the interpretation of the large volume of results generated. The real time systems are used for real time warning, essential for incidents such as belt fires. Tube bundle systems suit long term trending used for identification of the onset of spontaneous combustion or for the determination of explosibility during the routine sealing of worked areas. Gas chromatograph analysis is used to provide a complete analysis and provides results for hydrogen and ethylene, key gases used in the assessment of spontaneous combustion. It is also crucial during significant spontaneous combustion events and coal fires to use gas chromatography to determine the explosibility status of the underground atmosphere otherwise the severity of the situation is likely to be under estimated. This paper outlines the need for all three techniques for assessing the underground status and outlines advantages and disadvantages of each.

Jan 1, 2009

By C. D. Elifrits, N. B. Aughenbaugh

Introduction Federal and state laws enacted to regulate coal mining and the accompanying public concern about the adverse effects that mining might have on land use have focused much attention on the subsidence of the land surfaces over underground mines. Some questions asked are: • Will abandoned mines subside in the future even though they have exhibited no surface adjustment to date? • If so, when will subsidence take place? • Can a specific surface area be affected by subsidence more than once? • What surface form will the subsidence feature take? • Is there any way to predict when subsidence will occur and end? An attempt is made here to address these questions insofar as it is possible with available data and experience of evaluation of subcritical extraction conditions. Mining that results in subsidence features can be classified as supercritical, subcritical, and critical with respect to the minimum span lengths of the worked-out rooms (Fig. 1). A complete basin will not develop fully immediately over subcritical conditions because the span lengths of the entries are less than the critical dimension (Wardell, 1983). Passageways, entries, and room-and-pillar panels are all included in the subcritical category. Because of the short span lengths, subcritical mining conditions tend to be stable over the life of the mine unless adverse geologic conditions exist (Gray et al., 1974; Dunrud, 1976). Various roof control and support procedures are employed to maintain entry stability during mining. Little information exists concerning the time factor of subsidence over areas of subcritical extraction. Data that have been collected relate to longwall mines, whereby the cavity sizes are designed large enough to induce caving behind the working faces so that complete subsidence at the surface occurs within a short period of time. The UK's National Coal Board (1975) has reduced the enormous amount of data it has collected to empirical correlations and has published these correlations in its Subsidence Engineers Handbook. The handbook states that "None of the foregoing remarks applies to pillar and stall working," with respect to the section discussing the time factor of subsidence caused by longwall mining (National Coal Board, 1975, p. 40). To understand and evaluate how time relates to subsidence above room-and-pillar mines, one must first recognize how mine cavities deteriorate and fail. The propagation of failure to the surface must then be studied, and, finally, the failures that are manifest at the surface in the form of depressions accompanied by both compressional and tensional movements must be investigated. Failure of mine cavities Any cavity beneath the earth's surface represents a condition of nonequilibrium and tends to close with time. Failure of cavities in a subcritical mine can be classified as failure of the roof, failure of the floor, failure of the supports (pillars, cribs), and elastic rebound of the rock. One mode of failure may dominate, but generally combinations of the four will occur. Also, initial instability of geologic materials and structural features and in situ stress may be unknown factors that can contribute to cavity failure. Roof failure is the most obvious opening stability problem in most operating mines. The bridging capabilities of the roof rock are dependent on the rock's material strength, geologic discontinuities, and reaction to humidity changes in the air of the mine. This type of failure may vary in magnitude from gradual flaking to massive roof falls. Mine floor instability can be manifest in the form of a general heave over a broad area or of individual pillar punching. The weaker and thicker the immediate floor material, the more prone a mine is to experience floor problems. Water seeping into an area can soften the underclay, reduce its bearing capacity, and precipitate failure of support for the overburden.

Jan 8, 1986