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By Mehmet Guney

During the last decade various modifications of room and pillar and sub-level methods have been tried in an effort to eliminate gob-fires, dangers from roof falls, surface subsidence and to increase efficiency of extraction in the Armutcuk Mine, Turkey. It was eventually decided that the most likely system to give maximum benefits in view of existing geological conditions and coal seam characteristics was a system of cut-and-fill stoping employing hydraulic stowing. This paper has attempted to examine the trends of working techniques of hydraulic stowing. In addition, the results achieved and technical problems involved are discussed.

Jan 1, 1968

By K. W. Grubaugh

The recently enacted federal surface mine law (P.L. 95-87) will increase further the complexity of securing a reclamation permit. This law intensifies the need to present the required reclamation plan in a thorough and comprehensive manner. One plan format, that used in construction performance contracts, offers promise of filling this need. Reasons for using the format of expressed, bilateral, negotiated contracts common to the contruction industry, and the salient aspects of an application which uses this format are reviewed. Advantages of this procedure are seen to be improved mine planning, awareness of the total design job, potential for improved speed of permit acceptance and improved cost control.

Jan 1, 1978

By Neal I. Rosenberg

There is an old education maxim that a good teacher "first tells 'em what he's gonna tell 'em, then he tells 'em, and finally he tells 'em what he told 'em. I'm sure this says something about me as a teacher, and therefore as a student as well, but I'm going to begin by violating that maxim. The first thing I'm going to do is tell you what I'm not going to tell you. I'm not going to tell you that my company has found the solution to frozen coal problems. I'm not going to tell you that there is a miraculous new formula, and your frozen coal worries are over. Actually, it is really questionable whether there is a single step or process which will provide the answer. On the other hand, I do believe that at Union Electric we have made significant improvements in our ability to deal with frozen coal over the last couple of years, and I propose to describe some of the things we have done, what conclusions we have drawn so far, and the direction in which we are now headed. It would be well here to give a brief picture of the Union Electric system and the frozen coal problems we face. Union Electric is an investor owned electric utility with headquarters in St. Louis, Mo. Total generating capability is on the order of 6800 megawatts, which snakes us 24th or 25th largest in the United States. Power generation is by steam (both coal and oil fired), hydro, pumped hydro, and combustion turbine units. Although that is a diverse power supply, by far the largest source is our four coal fired steam plants. One receives coal exclusively by barge, the other three by rail. It is at these last three plants that the frozen coal difficulties arise.

Jan 1, 1980

By T. Cohen

Technological innovation in the minerals industry must be driven by the need to improve performance according to social, as well as environmental, safety, efficiency and production criteria. This paper outlines the possibilities and rationale for incorporating constructive technology assessment into technology research and development within the CSIRO Minerals Down Under National Research Flagship (MDU). The paper develops a process of Social License in Design that attempts to address the future social challenges and opportunities of a technology during development by utilising forecasting techniques and accounting for the perspectives and values of decision makers and likely stakeholders. Interviews with senior technologists and social scientists within MDU reveal the institutional context into which the Social License in Design process is to be situated and highlight key factors that may inhibit or enhance its uptake.

Jan 1, 2011

By H. Walqui, S. K. Kawatra, C. H. N. Jeltema, T. C. Eisele

"The literature contains many cases where the shape of hydrocyclone efficiency curves vary from the ideal “S” shape. These often appear as changes in slope, or inflections. These inflections can be divided into two categories: “coarse” inflections, which are caused by differences in the density of the minerals being separated, and “fine” inflections, for which there are a number of competing hypotheses concerning their cause. The existing literature addresses either the fine inflection or the coarse inflection, but no studies have reported both types of inflection occurring at once in a single hydrocyclone test. This paper presents hydrocyclone results from both in-plant studies and laboratory experiments that show both coarse and fine inflections. The industrial significance of both types of inflections is discussed. Hydrocyclone efficiency curves show the probability of any given particle reporting to the hydrocyclone underflow as a function of its size. Selectivity functions, S(d), are used to represent the fraction of the feed material in size fraction “d” that reports to the hydrocyclone underflow. Plotting this selectivity function against particle size leads to the standard S-shaped efficiency curve shown in Fig. 1. In the “uncorrected” curve, the tail of the curve does not go through 0%, because a portion of the solids are bypassing classification. This happens as a result of their being carried along by the water, and is most important for the finest particles. The curve can be “corrected” based on the fraction of the feed water that reports to the underflow, represented by the bypass fraction, Rf. The corrected curve then normally passes through 0%, as shown in Fig. 1.The act of correcting the curve shifts the value of the d50 size, which is the size that has an equal probability of reporting to either the overflow or to the underflow. Correcting the curve to account for the bypass fraction makes it easier to compare cyclone performance under conditions that cause the quantity of water in the underflow to change, but that do not alter the actual corrected cut size (d50c).The corrected efficiency curve can be expressed closely by equations such as Plitt (1976):"

Jan 1, 2015

By D. J. Crawford

The Lucerne Valley Operations of the Minerals, Pigments and Metals Division of Chas. Pfizer & Co., Inca, are located about 5 miles south of the town of Lucerne Valley, California. These operations consist of several limestone quarries, a whiting plant which produces finely pulverized limestone products, a-kiln which produces granular quicklime and lime products, and maintenance shops, warehousing, shipping, and office facilities. Construction of the Lucerne Valley plant began in 1961 as the result of a decision to utilize large undeveloped reserves of limestone in that area. Quarry development was started in the following year; and by 1965, Lucerne Valley had become the principle limestone and lime facility of the Western Operations of the Minerals, Pigments and Metals Division.

Jan 1, 1967

By John T. Cumberlidge

The Groveland deposit, in the Upper Peninsula of Michigan, consists of an E -W trending overturned syncline of Middle Precambrian Vulcan iron formation. At Groveland, the Vulcan formation can be divided into four units or facies. The total succession may be more than 550 feet thick, and consists of a basal unit composed of a lean chemical quartzite with traces of magnetite; a non-banded, partly clastic unit characterized by the preponderance of hematite over magnetite; a transition unit of well-banded magnetite-bearing iron formation interbedded with non-banded oolitic hematite; and a well-banded magnetite-quartz silicate unit at the top of the exposed sequence. The present magnetite-hematite ratios of different units within the orebody are considered to be a primary (post-diagenetic) feature of the original sediment. Subsequent regional metamorphism has increased the grain size of the original iron oxide minerals, but did not appreciably alter the oxidation state of the original sediment.

Jan 1, 1964

By Missy Isaman

"Mixed ground tunnels come in all kinds. In rock tunnels with possible faults and high pressure water, the challenges are many. With the advent of Crossover TBMs, contractors can minimize machine wear in such conditions while maximizing efficiency. The newest generation of Crossover is exemplified by two projects in Albania and Turkey. A 5.56 m Crossover TBM destined for Turkey’s Gerede Water Transmission will be assembled using Onsite First Time Assembly (OFTA) from within an existing tunnel. The unique machine will bore through 30 fault zones requiring the TBM to be sealable to up to 20 bar so pre-consolidation grouting can be done. If boring under pressure is required, the TBM will bore sequentially using the screw conveyor fore and aft gates. Skewing further towards hard rock, a unique 6.2 m diameter Double Shield TBM with Crossover features was designed for Albania’s Moglicë Headrace Tunnel. The machine features closure doors and a sealing system to contain inrushes of water until they can be grouted off. This paper will discuss the unique aspects of the Crossover designs, including their inception as based on past projects in difficult ground, and their utilization at the two current projects. INTRODUCTION Specialized tunnel boring machines have been made for years to tackle specific types of ground conditions. Traditional types of TBMs bore within a specific set of ground conditions. If a project is located in a competent granite face, then a Main Beam machine is a good solution. In soft ground, Earth Pressure Balance (EPB) machines are the method of choice. Years of experience and engineering advancements have made both types of machines fast and economical solutions for tunneling. Unfortunately not all ground conditions are a perfect swath of one material, and the need for a more diverse machine is apparent."

Jan 1, 2016

By S. L. Zhu, Brij M. Moudgil, J. L. Pinault

Prompt neutron activation probe (PNAP) was evaluated to determine chemical composition of phosphate rock slurry in-situ. The technique was able to precisely analyze Ca, Si and H using a 252Cf source. Direct measurement of P and Mg was not accurate due to interference by the rare earth elements associated with the Florida Phosphate Rock. The solids loading, particle size distribution and flotation reagents present in the slurry had no significant effect on the accuracy of the measurements. The technique was found to be reliable also under industrial conditions.

Jan 1, 1993

By J. W. Cooksley

Seismic methods provide an efficient and comprehensive approach to overburden studies pertinent to mining exploration and development, and to other mining and civil engineering problems such as rock mechanics, slope stability, and foundation engineering. For the purpose of defining geologic units and structural features, these methods are generally regarded as the most accurate, but most expensive, of the commonly-used geophysical exploration methods. Although the accuracy and cost of seismic work are generally affected adversely by rugged topography and complicated geologic conditions, it is in rough terrain and complex geology that seismic methods offer important advantages in overburden investigations. For example, to find the surface of rock underlying unconsolidated overburden at depths of approximately 200 feet, a 50-foot spacing of drill holes along the profile line would be required to yield a degree of resolution and accuracy similar to that obtained from a 50-foot spacing between seismic detectors along the same line. See Figure 1. In cases similar to that shown in Figure 1, a twelve-channel recording seismic system would be used. The main components of such a system would be: 1. detectors (commonly referred to as geophones) which convert the ground movement resulting from seismic waves into an electrical signal. 2. a multi-conductor cable which connects the seismic detectors to the amplifiers. 3. ampliiiers, amplify and filter the electrical signals . 4. oscillograph, records the amplified signal. 5. the blaster and firing line. A typical layout of the seismic spread and the components of the system Is shown in Figure 2.

Jan 1, 1968

By Arthur W. T. Grimley

Hydraulic coal mining is being successfully practiced in China, U.S.S.R., Japan and Canada and in each country, excepting Japan where suitable sites are not available, the system is being expanded to either existing conventional mines or new mines. Productivity levels and economics at these mines are in all cases better than the productivities achieved in conventional mines in the same general localities. In the U.S.S.R. face productivities approaching 50 tons per man shift have been reported while in Canada the latest statistics show average face area productivity levels are in the region of 200 tons per man shift production monitor. In the United States hydraulic mining has not been actively pursued to the same degree and consequently there are no full scale hydraulic coal mines in operation or construction. Because many of the coal measures in the Western U.S.A. are generally somewhat similar to those being successfully hydraulic mined in Western Canada and parts of Siberia it is realistic to believe that successful hydraulic mines can be designed and developed in the Western U.S.A. Particularly if the vast technological base that already exists is used to improve on other people's ideas, systems, methods and equipment.

Jan 1, 1983

By K. A. Natarajan

The relative significance of corrosive and erosive wear in magnetic taconite grinding is examined. The influence of different types of aeration, namely, nitrogen, air and oxygen on ball war was established for mild steel and high carbon low alloy steel balls. Ball wear data from dry and wet grinding tests are compared with those obtained in the presence of an organic solvent that does not promote electrochemical corrosion. 'Marked ball grinding, tests along with electrochemical measurements involving ball material and magnetite electrodes indicate that contribution from oxygen towards wear (corrosive wear) is relatively small and abrasive wear appears to be significant. Rheological properties of the slurry-appear to have an important bearing on the abrasive wear of grinding balls.

Jan 1, 1983

By M. K. Buder

Over the years, electric utilities have been faced with declining steam-coal quality, rising coal prices, and increasingly rigid and costly environmental standards. As a result, many utilities are beginning to show an interest in coal cleaning to upgrade coal by improving its heating value and reducing its sulfur content. Among the primary questions that must be answered for these electric utilities is whether the cost of coal cleaning can be offset by the potential cost savings in coal transportation and utilization in power generation. In search of at least a preliminary answer to this question, the Electric Power Research Institute (EPRI) engaged Bechtel to perform a case-by-case economic study to examine the cost effects of using cleaned versus raw coal to fuel new electric power plants. The results of two of the seven cases studied which involved western coals - one from Montana and another from Utah - are reported in this paper. Coal cleaning appeared to be a cost effective option for the Utah coal, but only marginally economical for the Montana coal. These cost results are expected to change to favor coal cleaning to a greater extent with the application of the final revised New Source Performance Standards regulating SO2 emissions just issued by the EPA. The study was based on the regulation originally proposed by the EPA under the 1977 Clean Air Act Amendments.

Jan 1, 1979

By Erle I. Shobert

In the comparison and consideration of synthetic and natural materials, graphites represent a situation in which natural graphites amount to less than 10% of the total carbon and graphite production by weight, and less than 5% in dollar volume, There are few applications where it could not be re- placed by synthetic graphite. On the contrary, synthetic graphite materials can be engineered to cover an extremely wide range of applications. These include electrographite brushes for rotating machinery, pyrolytic graphite, graphite-impervious pipe, nuclear moderators, high purity spectrographic graphite, power tube anodes, graphite rotary shaft seals, and rocket nozzles. The special qualities of natural graphite and its limitations are delineated and the almost unlimited possibilities in artificial graphite materials are discussed.

Jan 1, 1964

By Malcolm J. Robinson

Over 80% of Australia's population lives within 200 km of the coast, 70% in 10 major coastal cities. Potential cement raw materials are widely distributed but deposit size, quality, transport, market and environmental considerations are important in determining economic value. Major production locations are in a variety of geological environments ranging from Lower Paleozoic crystalline limestones to Tertiary and Recent polyzoal limestones and limesands, both onshore and offshore. Raw material transportation is by road, rail, sea, aerial ropeway and pipeline; road/rail transportation of the finished product is traditional but movement by sea of clinker and cement is increasingly a feature of the industry.

Jan 1, 1982

By Peter Zhang, Daniel Su, Berk Tulu, Bo Hyun Kim, Zoheir Khademian

Over 2,000 shale gas wells have been drilled in the Pittsburgh Seam longwall reserves. As longwall panels are laid out, some of these shale gas wells must be located in longwall chain pillars. With longwall mining on both sides and the constraint of chain pillar size, gas well in chain pillars are subjected to longwall-induced ground movements and stresses, which could induce deformations in gas well casings Casing deformations are associated with several factors such as overburden geology, surface topography, setback distance, and casing construction. Overburden geology is one important factor that largely determines the locations and levels of deformations in gas well casings Previous NIOSH gas well research has found that casing deformations above the coal seam horizon are smaller under deep cover than unde shallow cover and that casing deformations could occur at the coal seam horizon under deep cover. Recent mine-by cases have provided more insights into the locations and amount of longwall-induced casing deformations as well as the potential occurrence of a large casing deformation at the coal seam horizon. This paper presents three recent mine-by cases with shale gas wells in the chain pillars between two adjacent longwall panels under different overburden depths. Casing deformations were measured by multi-finger caliper surveys and predicted with numerical modeling. With the established numerical model, the effect of overburden depth was further analyzed to investigate the potential occurrence of a large casing deformation at the coal seam horizon under deep cover. These mine-by cases not only provide a general demonstration of how overburden depths can affect longwall-induced stresses and deformations but also give a good indication about the level of casing deformations that could occur under different overburden depths. The study concludes that (1) casing deformations reduce with increase of overburden depths at the gas well; (2) a cementing alternative with production casing uncemented is an effective means to eliminate production casing deformations; and (3) large plastic casing deformation could occur in the production casing at the coat seam horizon under deep cover. The experience and knowledge gained from these mine-by cases would help longwall operators and gaza companies to take appropriate measures to minimize the influence of longwall mining in shale gas wells in chain pillars.

Jun 25, 2024

By Richard F. Roethe

Surface coal mining productivity in the U.S. and Illinois has shown a general declining trend since 1969. The U.S. Department of Energy conducted an analysis in 1980 of the causes of declining productivity in different states. This paper presents a detailed analysis of changes in overall productivity and productivity in different functions such as overburden preparation, overburden stripping, reclamation, coal handling, etc. during the period 1970-1982. Statistical analysys techniques including multiple regression were utilized in the study.

Jan 1, 1983

By A. Moergeli, Philip Sander, John J. Reilly

"Estimating and managing the costs of complex infrastructure projects – in the planning/design and construction phases, for both owners and contractors – has been a challenge for decades. The more complex and technologically advanced the project, the greater the uncertainty, including potential risks that are important to owners and contractors, such as:• Cost risks to owners – meeting budget and schedule, maintaining public credibility.• Cost risks to contractors – profit, consequences of loss, impacts to reputation/future work.This concern has been addressed in various ways by the underground construction industry for some time (Reilly, 2001). In particular, while significant advances have been made in cost estimating for the planning and design phases (Reilly et al., 2004), that are important to agencies and political decision-makers, it is not apparent that these advances have been widely adopted for construction cost estimates. The reasons for this may relate to lowbid considerations – any method that tends to increase the contractor’s cost estimate, by including risk or likely costs, could lead to an erosion of the contractor’s competitive position – if others are not similarly required to include such costs.Different cost estimating methods produce different levels of information. Specifically, there is a large difference in the character and depth of information if a deterministic (quantities times price plus a contingency) and risk-based cost methods are used. It is this difference in character and depth of information that is the reason that risk-based cost estimating has potential value for owners and contractors. Figure 1 presents hypothetical cost results from deterministic and risk-based methods and illustrates some of these differences.In Fig. 1, the results for deterministic and risk-based cost estimates are given related to the potential profit or loss for a typical project. As is evident in this example, there is significant potential for costs to be realized that are higher than the proposal/bid value estimated using a deterministic approach, with a 15 percent probability of a loss. There is a 30 percent probability that the project will have a reduced profit. There is a 55 percent probability that the project will return a good profit. Using a risk-based approach, it is possible to better recognize this potential outcome in the bid phase and, as a consequence, develop a strategy to:"

Apr 1, 2016

By A. J. Kwitowski

Teleoperation is a technology that can provide significant health and safety improvements in mining, by relocating machine operators hundreds of meters away from the face area. The U. S. Bureau of Mines (USBM) has recently developed a teleoperation system for continuous mining and haulage equipment. This system features near-real-time closed-loop control. A prototype system was developed and demonstrated on the surface. This system could be used in thin-seam applications down to 914 mm. Details are provided on the developed teleoperation system, results of testing, and expected, future applications of this technology for improved safety.

Jan 1, 1994

By N. Oswald

As coal mines age and become more developed, ventilation modeling becomes more important for the planning and continued operation of the system. Numerous studies have been performed and presented that address the collection of data and measurement of airway friction factor and resistance per unit length values. However, a quantitative analysis of the resistance for stoppings in coal mines for different construction materials and methodologies has not been adequately addressed. In order to develop an accurate/realistic ventilation model both airway resistances and stopping resistance values need to be determined. Over the course of the past two decades Mine Ventilation Services, Inc (MVS) has measured the resistance of stoppings of various construction types in mines throughout the world. An analysis of this data is presented in this paper along with a discussion of measurement methodology.

Jan 1, 2009