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By Ken E. Baylis

Current over-capacity in coal production provides assured and relatively low-cost supplies to coal importers. At the same time, it is of serious concern to coal producers who invested considerable sums in the expectation that overseas demand would continue to grow rapidly. This paper assesses the reserves available for export, the export facilities, the coal supplies which can be put through them, and the market prospects for the future. It assumes, rightly or wrongly, that there will be no major and prolonged disruptions in supply from any major sources of coal. COAL RESERVES FOR EXPORT Economically recoverable reserves in the non-communist world amount to about 470 billion tonnes. These are sufficient to sustain current production levels of 2 billion tonnes a year for 235 years.

Jan 1, 1984

By William Gleason

"Speakers and attendees of the 2016 Cutting Edge Conference could not be faulted for keeping one eye on the presentations taking place at the Hyatt Regency at LAX in Los Angeles, CA on Nov. 7 and 8 and another on the results of the historic election in the United States that took place on Nov 8. While there was certainly interest in the presidential campaign, there was also a great deal of interest in Measure M on the California ballot. Measure M, which passed easily, is a half-cent sales tax increase that will fund the most ambitious transit expansion in Los Angeles County history.In the coming years, the ballot measure will transform a traffic-choked region by funding the construction of nearly a dozen new rail lines with an estimated $120 billion raised in four decades. Among the projects that could come to fruition are a twin-rail tunnels project through the Sepulveda Pass and new connections in the city.During the update on West Coast projects, Bill Hansmire summed things up with a slide asking “How much work is there on the West Coast,” and his answer was “Billions.”From Seattle, WA south to Los Angeles, there is already a lot of work for tunneling and underground construction experts, and Measure M ensures that there will be plenty of work for decades to come.Currently, The Los Angeles County Metropolitan Transportation Authority (Metro) has three rail projects underway that were funded by Measure R in 2008 — the Regional Connector, the Purple Line subway extension and the Crenshaw/LAX Line that are designed to alleviate the traffic pressure with an eye to more solutions.Measure M is the fourth sales tax increase to fund transportation in L.A. County, bringing the base sales tax rate to 9.25 percent. In some cities, which already levy their own sales tax, the rate would be higher, The Los Angeles Times reported.About 35 percent of the revenue will fund major new transit projects, such as the subway under the Sepulveda Pass, extension of the Gold Line to Claremont, extension of the Crenshaw Line to West Hollywood and acceleration of the Purple Line Subway construction along Wilshire Boulevard to finish in 2024, 10 years earlier than scheduled.About 17 percent would fund a dozen highway improvement projects, such as widening parts of I-5 in the Antelope Valley and southeastern county, adding bus lanes to the Sepulveda Pass section of the 405 freeway and adding truck-only lanes to a section of the 710 freeway."

Dec 1, 2016

By Benjamin Grunauer, Anthony Iannacchione, Taylor DaCanal

"In Pennsylvania’s rich mining history, various forms of room-and-pillar mining have been in use for over 150 years. Longwall mining, introduced in the late 1960s, occupies only the last 60 of those 150 years and now represents the dominant method of extracting coal in the Pittsburgh coalbed. The introduction of longwall mining allowed larger quantities of coal to be extracted in safer and more efficient manners than room-and-pillar mining. However, the associated formation of subsidence basins have elevated both the number and intensity of watersource and surface structure impacts. When these first longwall panels were mined the factors responsible for these impacts were poorly understood and regulations were focused only on surface structures. Today, with over 600 panels mined under a wide range of conditions, these factors are known and regulations have developed to help mitigate water supply and surface structure impacts.The cause and severity of surface effects are thought to be dependent on multiple factors, including the location within the subsidence basin, overburden, panel width, and orientation of the panel. The changing characteristics of over 600 longwall panels mined in the last 60 years are analyzed to determine factors important in subsidence related surface impacts. This study compares the location of the surface impacts with the longwall panel size, overburden, and maximum predicted vertical subsidence. The data shows that changing these characteristics are impacting surface features in a significant manner as measured by the number of company liable reported effects.INTRODUCTIONLongwall mining has occurred in Pennsylvania for over 60 years, and at the current mining rates, longwall mining is expected to continue in the Pennsylvania Pittsburgh Coalbed until the reserves are exhausted. Figure 1 shows all mining that has occurred in the Pittsburgh Coalbed, as well as the area that is left to mine. It is predicted that there are 40 years left of longwall mining on the Pittsburgh Coalbed, under the assumption that 50% of the total 280,000 acres will be mined at the current rate of 3500 acres/year."

Jan 1, 2019

By J. C. Motz

During the past five years, Rexnord has developed, tested and introduced the Nordberg Omnicone Crusher to the industry. When the Symons brothers invented the cone crusher over 60 years ago, they employed the principle wherein the length of the crushing stroke was related to the free fall of material by gravity. This permitted the material being crushed to fall vertically in the crushing chamber; and in effect, caused the particles to be crushed in a series of steps or stages as the particles got smaller due to the crushing action. This also helps to reduce the rate of wear of the liners since the sliding motion of the particles is minimized.

Jan 1, 1986

By Lloyd M. English

Accurate knowledge of the gas content of coal seams has always been important, according to the work of W. P. Diamond and J. R. Levine, 1981, but is becoming increasingly important for several reasons: Excessive gas emissions in the mine can create explosion hazards. Depletion of shallower coal reserves is forcing underground operations to greater depths where coal gas content is often greater. Natural gas prices and the need for new energy sources make naturally occurring coal gas a potential resource of economic interest. Information on coal gas content will impact mine designs, mine ventilation system specifications, and the effectiveness of methane control procedures used. Accurate resource assessment is needed for projecting and designing potential gas utilization enterprises. The emphasis upon methane hazards in mining operations, and upon potential methane utilization, has led us to improve upon the procedures used to determine coalbed methane levels.

Jan 1, 1984

By M. Manrique

Various pyrometallurgical methods for treating Ilmenite and Zircon concentrates are reviewed. Laboratory experiments, using a thermal plasma reactor, have been performed to evaluate: the conversion of ilmenite to TiC or TiC-Fe and the conversion of zircon to ZrC or ZrC-SiC. Results are examined and possible processing routes are identified.

Jan 1, 1996

By J. Partyka

Respirable dust produced during blasting operations in underground mines exhibits both diffusion and convection properties of the airflow. However, the application of the mathematical model presently used to calculate the change in time in the concentration of blasting pollutants is mostly limited to a single drift and cannot be easily utilized for blasts taking place in stopes. This paper discusses an analytical solution based on considerations that enable us to reliably identify the initial condition. Such an approach may be used for any blasting area regardless of its position, its size, or the ventilation system in use during blasting. In addition, a test procedure using field data is established to determined those parameters not measured directly. As well, equations are derived to find the diffusion coefficient, and the position and size of a dust source from the field data. Mathematical considerations The convection-diffusion problem, for a one-dimensional case, is described by the following partial differential equation (PDE): ct. = Dcxx - Vcx + source - sink(1) where C = the concentration of a pollutant T = time V = the mean air velocity in x-direction D = the diffusion coefficient X = distance away from the pollutant source source = any additional pollutant source specified by an initial value problem sink = decay of a pollutant inside the region specified by the boundary conditions. Respirable dust produced during blasting is best considered as an initial value problem (IVP). To derive a mathematical model, the following assumptions are made: •At time zero (t = 0), the dust source is at point x = 0 of an infinite drift. •The problem is considered a one-dimensional case. •The mean velocity of air and the diffusion coefficient are constant. •There is no source or sink of dust other than specified at point x = 0 and time t = 0. We have to solve the following problem [PDE ct=Dcxx-Vcx-m<x...m;0<t<m(2)] ICc(x,0)=f(x)t=0, the initial condition Where c = dust concentration in mg/m3 V= the average mean velocity in a drift in m/s t= time in s D= the diffusion coefficient in m2 /S x = distance coordinate in m. We observe that in problem (2), we have moved the boundaries to[ -m and +m] in order to have an initial-value problem. We introduce new coordinates, s = t and z =x - Vt. To rewrite the PDE in terms of (z, s), we use the chain rule ct = czzt + csst = -Vcz + cs cx = czzx = cz cxx = (cz)x = czz. We now substitute our computed ct, cx. and cxx into the PDE to get new IVP in terms of z and s :

Jan 1, 1991

By D. J. A. Chambers, J. M. Wempen, K. D. Koper, M. K. McCarter, K. L. Pankow

"The EarthScope Transportable Array (TA) of broadband seismometers (www.usarray.org) was deployed across southwest Wyoming from November 2007 through May 2009. During this time period the Array Network Facility (ANF, anf.ucsd.edu) detected and located a total of six seismic events near the trona-mining district. This lack of seismicity is atypical compared to coal mines employing similar mining methods. In this study, eighteen months of continuous seismic data from several nearby TA stations are reexamined using conventional and correlation-based methods to detect seismic events. Waveform cluster analysis and epicentral locations are used to discriminate between mining induced seismicity (MIS) and seismic energy generated from surface blasts at nearby coal mines. The locations and magnitudes of the 143 newly detected MIS events are compared to regional subsidence as measured by Differential Interferometric Synthetic Aperture Radar (DInSAR). INTRODUCTION An abundance of natural resources and a favorable political climate have made southwest Wyoming home to multiple large mining operations. Among these operations are five underground trona mines located approximately 50 km west of Rock Springs, Wyoming. The trona mines employ room and pillar, longwall, and solution mining methods over an area roughly 900 km2, and produce a sizable portion of the world’s soda ash (Brown 1995). Historically, in the Rock Springs mining district, several relatively large magnitude seismic events have occurred. These events are thought to have been related to mining activity and have caused notable subsidence (Case 1997). The largest event in the region recorded by seismometers, ML 5.1, has been confirmed as the 1995 Solvay Trona Mine collapse (Pechmann et al. 1995). In addition, blasting at surface coal mines near Rock Springs produces significant amounts of seismicity; approximately 50% of all daytime seismic events in the Mountain time zone from 2007 to 2009 locate near an active surface mine in this region (Astiz et al. 2014). Much of the current research related to surface subsidence and induced seismicity focuses on wastewater impoundment (Ellsworth 2013) and hydraulic fracturing. The observable seismicity in geological injection environments is widely variable and McGarr (2014) has argued that, in such environments, the maximum amount of seismic energy that can be released is proportional to the injected volumes. Like injection environments, in extraction (mining) environments seismicity is highly variable depending on many geological and operational variables (Boltz et al. 2012; Carnec and Delacourt 2000; Fritschen 2010; Iannacchione et al. 2005; Sen 2013) and does not always correlate well spatially with subsidence, a surface expression of extraction at depth."

Jan 1, 2015

By Pramod C. Thakur

During the past ten years, the US coal industry has experimented with various ways to extract methane from coal seams. Drilling long horizontal boreholes in solid coal from mine workings and vertical gob degas boreholes are becoming standard techniques for methane recovery from coal seams. Prime motivations for such work have always been safety and productivity in mines, but the commercial value of gas so produced is encouraging utilization. The paper reviews various ways to produce methane from coal seams and discusses some utilization projects extant in the industry.

Jan 1, 1984

By Carlos Álvarez, Sergio Sánchez, Michael Mains, Giuseppe Gaspari

Extensive record of tunnels excavated with SEM (sequential excavation method) in swelling grounds exists in literature: global experiences include successful tunnelling both through clayey and rock masses with time dependant deformation. However, TBM (tunnel boring machine) use in swelling conditions with high water pressures (EPB, earth pressure balance, machines or slurry shields) is much less documented, considering the lower expected impact due to the limited stress relief and operations under saturated conditions. This paper summarizes a number of studies conducted as part of the risk assessment and detailed design of a large diameter TBM tunnel in variable and challenging geological conditions. The tunnel alignment is driven through mixed face conditions including swelling soils and clayey soft rocks, prone to intense time-dependent deformations. The paper also describes the approach adopted for the design of pre-cast segmental lining subject to both swelling actions and high seismic loads, due to the regional active tectonic faults. The design of this lining included a detailed parametric study performed to handle the existing uncertainties related with ground characterization, potential deconnement and complex geological congurations.

Jun 23, 2024

By James J. Scott

In 1910 the United States Bureau of Mines was created. It was the outgrowth of a social problem stemming from the fact that 25,000 men were killed in coal mining accidents for the period 1900-1910. Something had to be done and congress responded to the people&apos;s demands by creation of this new regulatory agency. At that time mine operators felt the new agency was too strict but nonetheless new rules were developed and enforced and results were obtained by the industry which reduced fatal accidents to less than 250 per year by 1970.*Social reaction by the general public brought about legislation which created the Federal Coal Mine Health and Safety Act of 1969 This legislation was a direct reaction to the Farmington Disaster. Operators and miners alike said "we cannot operate under this law. It is too strict, requirements are unrealistic, production will suffer, .there will not be any improvement in health and safety, etc." Consider the facts: 1. Health and safety have improved. The 1972 frequency and severity rate was the best ever for the bituminous coal mining industry, Figure 1. 2 .Production per manshift has dropped in underground coal mines. For example, in West Virginia from near 16 tons/m.s. in 1967 to nearly 11 tons/m.s. in 1971-72. However, not all of this loss can be attributable to the Act, but certainly some is. (2) The betterment of the safety of coal mining was a prime motivation behind the coal law and from that standpoint the law has been partially successful, but the loss in productivity has been a real burden to the mine operator. Everyone should recognize that the law says little in regard to production--it only relates to health and safety. Production is management&apos;s responsibility.

Jan 1, 1973

Water contact angles in the air/water/francolite, fuel oil/water/francolite and fuel oil/water/quartz systems were measured to describe the wetting characteristics of these minerals. It was found that white francolite is more hydrophilic than black and tan francolite both in the absence and presence of fatty acid addition. The contact angle measurement results do not correlate very well with the flotation response and it appears that kinetic aspects of the bubble attachment process play an important role in the francolite-fatty acid flotation system.

Jan 1, 1997

By Guy T. McBride

Mr. Chairman, Fellow Keynoters, Ladies, and Gentlemen: It is purposed to consider the theme of this meeting, "The 1970&apos;s - Pivotal Decade for the Mineral Industries," from the particular -- some would say peculiar -- point of view of one engaged in mineral engineering education, and this coign of vantage prompts the textbookish subtitle, "Problems and Solutions (?) in Undergraduate Mineral Engineering Education." Three interrelated problems, or problem areas, will be presented and discussed, and where solutions seem to be emerging or seem worthy to be suggested, they will be identified. The three problems are: 1. The goals, and therefore the course requirements, of the undergraduate curricula are in question, 2. The unit costs of undergraduate education appear excessive to those who bear the charges, and 3. The social ambience of the day affects for the worse the work attitudes and the career motivation of both prospective and in-course students. The Need. - Any discussion of these problems must bottom upon recognized national needs for minerals and a technologically sound minerals industry staffed by competent engineers, particularly at the exploration, development, and production levels, Fortunately, these needs have been recognized and to some extent quantified, and they are even now under further intensive study by some of the most competent members of our society and profession. The latter reference is, of course, to the current work of the National Commission on Materials Policy (U.S.A.) under the executive directorship of Dr. James Boyd. Predating this, and perhaps to some extent

Jan 1, 1972

By David S. Young

All pigments and extenders or fillers whether organic or inorganic fall into the following broad general classes: I. Colored II.-White III. Black IV. Metallic A pigment- is any particulate matter that is essentially insoluble and chemically unaffected by the media into which it is dispersed. According to this very broad definition, colored pigments, white pigments, fillers, extenders, and functional pigments would all be included. The particulate size range would also be quite broad ranging from very fine colloidal particles (~0.01µ) to relatively coarse particles (~100.0µ). This broad definition is usually subdivided into more practical divisions which tend to relate the classification of the pigment to its primary function in the system in which it is used. Hence, the word extender implies that its major purpose may be to extend the system.

Jan 1, 1985

By M. Sadegh Safarzadeh, Stanley M. Howard

The two-dimensional predominance area (Kellogg) diagram (PAD) surfaces bounding the three-dimensional Cu-As-S-O system were constructed at 900 K. The computations employed gases As4O6(g), O2(g), and SO2(g) as the independent coordinate species to generate diagrams of As4O6(g) − O2(g),O2(g) − SO2(g), and As4O6(g) − SO2(g), while the third gas (As4O6, O2, or SO2) was fixed. The results indicate that there is no shared boundary between enargite (Cu3AsS4) and copper sulfate (CuSO4); however, at PO2 < 10−6 atm, PAs4O6 < 10−10 atm, and PSO2 > 10−4 atm, CuSO4 is the stable phase at 900 K. The chemical driving force for oxidation of intermediate phases between enargite and copper sulfate is substantial except for basic sulfate (CuO · CuSO4).

By Matthew Grzelak, Gulsah Erinc, David R. Chapman

"The third phase of the Bagram Drainage System project at Bagram Air Force Base in Afghanistan included construction of a shallow, 540-m long, 1.8-m inside diameter drainage tunnel. The tunnel penetrated mostly stiff to hard clayey and silty soils. The contractor’s Value Engineering Change Proposal (VECP) to use pipe-jacking with a microtunnel boring machine (MTBM) instead of the specified two-pass Earth Pressure Balance method was evaluated and supported using hand calculations. Contractor support was provided throughout the project by providing design reviews and instrumentation monitoring during construction. This paper compares the value-engineering proposal to the specified method and describes the construction conditions encountered. INTRODUCTION As part of a larger improvement project at the Bagram Air Force Base in Afghanistan, a shallow, 540-m long, 1.8-m inside diameter drainage tunnel was constructed to provide additional capacity for Coyote Creek to pass below several critical structures, including taxiways and the main runway, for mitigation of recurring flooding (see Figures 1 and 2). Overburden over the tunnel crown ranged from about 3 m to 5.5 m. An existing cast-in-place twin barrel concrete culvert runs approximately parallel to the new tunnel and is within about 8 m at its closest point. The contractor’s Value Engineering Change Proposal (VECP) to the specified two-pass Earth Pressure Balance (EPB) method (steel ribs and lagging or steel liner plate with a carrier pipe later grouted in-place) called for installation of the required drainage pipe by pipe-jacking (one-pass installation) using a slurry microtunnel boring machine (MTBM). The critical nature of the operations at the air base resulted in significant construction coordination challenges and a greater than usual need to avoid excessive settlements. Substantial restrictions were placed on drilling of investigative borings and installing instrumentation near runways and taxiways due to drill mast height. The prime contractor was SERKA TAAHHUT INSAAT A. S. (SERKA), the microtunneling subcontractor was Ludwig Pfeiffer Microtunnel GmbH & Co.KG (Pfeiffer), the jacking pipe designer was Gollwitzer Pipe and Shaft Technology GmbH (Gollwitzer), and the contractor’s tunnel engineer was Lachel & Associates, Inc. (Lachel). Lachel provided contractor support throughout the project including preparation of a VECP/Design Summary (including interpretation of existing and new geotechnical information), design reviews for jacking pipe, estimating settlement of an existing drainage structure above the new tunnel, and instrumentation planning, monitoring, and analysis during construction."

Jan 1, 2016

By M. Misra

The processing strategy for the effective separation of bitumen from low grade (< 10 weight percent bitumen) Utah tar sands by a hot water process differs significantly from that used for the processing of high grade (> 10 weight percent bitumen) Utah tar sands. Excellent separations (coefficient of separation = 0.9) can be achieved for high grade Utah tar sands by intense hot water digestion followed by a modified froth flotation step. Such a technique is ineffective for low grade tar sands. In order to change the characteristics of the low grade tar sand an attempt was made to enrich the bitumen content of the feed to greater than 10 weight percent by recycle of bitumen concentrate to the digestion stage. However the quality of the separation was not improved under these circumstances. Similarly feed enrichment by heat treating the low grade feed with recycled concentrate prior to digestion did not improve the separation. More successful separations of low grade Utah tar sands were finally achieved by modification of the viscosity of the low grade bitumen with controlled addition of diluent. These results of the hot water separation tests and variations in the quality of separation are interpreted in terms of the physical properties of the bitumen and the surface bonding forces operative at the bitumen-sand interface.

Jan 1, 1979

By M. F. Martin

Dewatering aids are chemicals which enhance the efficiency of mechanical dewatering equipment such as vacuum disc filters and centrifugal dryers. A new dewatering aid has been developed which significantly lowers the moisture content of the mineral concentrate and causes none of the undesirable side effects normally associated with dewatering aids. Highlights of product development from laboratory screening through field testing will be discussed.

Jan 1, 1985

By T. A. Ring

The bed filtration of colloidal particles has been modeled by performing a differential particle balance. The balance considered the localized particle deposition rate to be the sum of three rate resistances: 1) mass transfer to a region near the surface; 2) adhesion onto a partially filled surface; and 3) resuspension from a partially filled surface. The differential particle balance equations, one for the free particles and one for the adhered particles, were solved by a finite difference algorithm. The results of this model are compared to experimental filter breakthrough curves.

Jan 1, 1983

By J. B. Knaebel

I have been asked to discuss the "Development of the Twin Buttes Mine for Production." This property, which is a large low-grade open pit copper mine about 25 miles south of Tucson, Arizona, was recently brought into production by The Anaconda Company under a long-term lease agreement with the Banner Mining Company. Since the scope of this paper is limited to the subject broadly indicated by its title I will confine discussion of historical, environmental and other general matters to a brief summary sufficient, I hope, to establish a background of those conditions which influenced our approach to the technical and economic problems that faced us at Twin Buttes. The paper deals primarily with our studies and activities related to the solution of these problems and with the resulting engineering and business decisions that were taken - decisions which culminated last September in the initial commercial operation of another major open pit copper producer unique and interesting in several respects.

Jan 1, 1970