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By J. -C. Roegiers, M. Thiercelin

Accurate toughness determinations are difficult to achieve in the case of soft or heterogeneous rocks. The existence of a large process zone ahead of the crack tip makes the determination of the apparent toughness crack length dependent, in the case of subsized specimens. In order to use practical size specimens, the authors propose a new toughness test, the Modified Ring Test, which pre- vents a largely developed process zone to form ahead of the crack tip. This test has also the advantage that its geometry is core-based. Numerical and experimental results are discussed.

Jan 1, 1986

By H. T. Mulryan

Talc is used as an essential ingredient in a variety of plastics applications ranging from polyester body patch compounds through polypropylene automotive, appliance and household furniture components to high performance parts made from liquid crystal engineering resins. This paper focuses on polyolefin applications, the three-tier market for talc in polypropylene, the effects of various tales in typical compounds and trends in each market segment. Emphasis is given to emerging markets, examples of which are polypropylene compounds that mimic higher cost resins, and polyethylene films. Customer requirements for tales for these purposes are discussed.

Jan 1, 1994

By Robert P. Mahoney, William J. Roe

Polymers of a wide variety of composition are used in coal and mineral beneficiation. Applications include flocculation and coagulation in thickeners, filtration enhancement, mill scale control, dust control, ore leaching improvement, and pond management. The proper chemistry of the polymer is determined by many factors, including the nature of the process, mineral type, and respective performance requirements. This paper provides an overview of the various current applications of polymers in mineral processing, and a description of the applicable polymer chemistries which find utility in these applications. Examples of structure/performance relationships are discussed.

Jan 1, 1994

By Nicolae Dobritoiu

From experience and scientific references it is known that during information processing, the following error types are transmitted: technical, analogy errors and method errors. For decreasing the value of these errors, especially of the method ones, old algorithms should be perfected and new ones should be developed for processing, interpreting and achieving the graphical layout by means of automatic data processing. In this respect, we propose a new deposit model based on numeric mathematical modelling which requires the use of automatic data processing. The utilization of the numeric model of the proposed deposit, allows the obtaining of the following advantages: • the model is used for any deposit form; • it is used for the calculation of deposit resources (volume, weight, and content); • it is used in design due to the facility of obtaining sections through the deposits area; • it eliminates at "0" the errors of graphical data transcription; • the use of the model imposes a uniform geological research; • the algorithm is transposed in a package of programs.

Jan 1, 2002

By R. A. Lohnes, S. M. Levorson

As part of research to develop a coal handleability index that predicts the ease with which coal will flow through a handling system, comparative tests were conducted with a Johanson Indicizer and a low-stress triaxial apparatus on 12 coals at a variety of gradations and moisture contents. The lndicizer test provides a rapid method for generating data associated with coal handling characteristics. The arching index measured with the Indicizer is a function of the geometry of the apparatus as well as the properties of the coal. The handleability index determined from triaxial data is a more direct measure of coal characteristics. The handleability index shows a wider range of values than the arching index and, therefore, appears to be more sensitive to coal variations. Neither the arching index nor the ratholing index, as measured with the Indicizer, agreed well with the handleability index. This is attributed to differences in sample preparation as well as to the tests themselves.

Jan 1, 1993

By V. Kontogianni

The underground extraction of coal is associated with ground movements extending from the mining area to the ground surface, which result in bowls of ground subsidence, with amplitude exceeding the amount of several meters and occasionally with important tilt and curvature of ground surface. Such changes at both the underground environment and surface topography lead to destruction of buildings, failure of utilities and transportation networks, and occasionally formation of areas vulnerable to flooding, or even small pools. Based on geodetic surface measurements of ground elevation changes, various theories and empirical models relating surface subsidence with the geometry of underground voids formed have been proposed, and predictions of expected subsidence in the form of contours have been estimated. In this study a case study of planning of a new highway network through areas in which coal extraction was also planned is discussed. This work is partly funded by EU. The optimum solution selected was a modification of the initial highway planning, so that the road is increased in length and by-passes the richest coal-field, where maximum post-exploitation subsidence was predicted, and only crosses either minor coalfields, which are not to be exploited, or even margins of main coalfields, in which minor post-exploitation subsidence is expected.

Jan 1, 2006

By Ching Wu, David A. Sutter, Peter Frobenius

The MUNI Metro Turnback (MMT) Project includes a 256 m (840 ft) twin tunnel section, which connects to the Embarcadero Station, and runs under Market Street in San Francisco. The tunnels go through a mixed face condition of fill at top and Bay Mud at bottom, and a significant number of buried timber piles. This paper presents the selection of tunneling equipment, excavation methods, excavation support and chemical grouting; specification of timber pile cutting methods; and steel lining analysis and design. This paper also reports on the initial phase of the tunnel construction.

Jan 1, 1995

By Elza F. Burch

Feeding 600 pm X 0 raw coal to heavy media cyclones, along with the +600 pm size coal, produces an efficient separation of both the +600 pm and 600 pm X 150 pm sizes. Major advantages of the process include the elimination of desliming screens and secondary fines circuitry for cleaning the 600 pm X 150 pm size coal, and result in a very simple circuit. Incorporating four 660 mm diameter heavy media cyclones, the Providence Plant of Island Creek Corporation has operated efficiently for ten years with a magnetite consumption rate of less than 0.45 kg per ton of raw feed at a feed rate of 454 tph.

Jan 1, 1988

By R. Q. Honaker

Until recently, the application of the Jameson Cell technology in North America has been restricted to minerals processing. Recently, laboratory, pilot-plant and full-scale testing has been conducted to assess the Jameson Cell's ability to effectively treat fine coal. Based on the data, carrying-capacity relationships have been developed. In addition to its operational simplicity, the Jameson Cell has the ability to provide a separation efficiency near the theoretical separation performance on the basis of ash rejection while achieving a relatively high throughput capacity Tie results obtained from the various fine coal cleaning applications in North America is presented in this publication.

Jan 1, 1999

By Thomas W. Healy, David V. Boger, Yee-Kwong Leong, Lee R. White, Peter J. Scales

The concentration of mineral slurries by conventional thickening devices is discussed. The role of additives on the compression of mineral slurries is also examined. Results for a range of flocculation conditions are presented. The compression of flocculated mineral slurries is found to be highly dependent on the fundamental particle-particle interaction forces and hence, the rheology of the particulate fluid. It is demonstrated that a detailed knowledge of the properties of both the mode of operation of the thickening device and of the solid/liquid interface is required for improvement in the rate and in particular, the extent of dewatering.

Jan 1, 1995

By F. H. Mertens

The concentrators of Gecamines are fed by a great variety of ores and produce different types of oxide and sulfide concentrates. It is therefore important to translate the performances of each circuit in terns of dollars in order to reach cost optimization in each mine to product line. A new system has been recently implemented for achieving this objective. Technical data and expenses are collected, allocated and analysed on mainframe applications. On the other hand, optimization and simulations are carried out on microcomputers which are linked with the mainframe files. Various kinds of auditing reports can be produced, including those leading to investments and cash-flow pattern which are

Jan 1, 1991

By D. C. Torre

Ever since the introduction of the first successful continuous mining machines some twenty odd years ago, there has been an obvious, and steadily increasing, need for some form of continuous haulage machine, or system to work with them. There is universal agreement that the continuous mining principle, and the various continuous mining machines in particular, have done a great deal for mining. However, coal mining men, who have the longest and broadest experience with them, agree that continuous miners do not truly mine continuously. In fact, their estimates, and actual studies, show that the real mining time of these machines ranges, on the average, from 20% or less to about 30% of the available shift time. Part of the failure of the continuous mining machine to mine continuously may be ascribed to breakdowns in its intricate machinery. Most of the failure, however, is blamed on a variety of other factors. Of these, there are two which are given particular blame: face haulage and roof control. The relative importance of the two as the major negative factor in continuous mining is a moot point. However, there is an extensive concensus that haulage is the number one problem. Roof problems and their control are inhibiting factors regardless of the type of mining or mining machines employed. But the truth of the matter is that a continuous mining machine, like any type of loading machine, whether underground or on surface, is only capable of mining or producing in direct ratio to the mineable, or loadable, material that can be kept ahead of it and equally, if not more, important, that can be taken away from it. While the first commercially successful continuous miners were developed for, and proved successful in, coal mining, they were soon

Jan 1, 1974

By William J. Francart, Edward J. Miller

The utilization of computer based monitoring systems for fire detection in underground coal mines has grown significantly in the past seven years. In 1984, an annual MSHA survey identified a total of 38 systems being used in U.S. underground coal mines, while a 1990 survey indicated the number has risen to 112. The applications for mine monitoring have also changed according to the annual surveys. From April 24 to June 21, 1990, investigations were conducted by personnel of the Ventilation Division, Pittsburgh Health Technology Center, in cooperation with Coal Mine Safety and Health, concerning the installation and operation of Atmospheric Monitoring Systems in underground coal mines. These investigations were conducted to gather information concerning the ability of the AMS to detect fires and heatings, false and nuisance alarm frequencies, information related to system maintenance, and information related to employee training on system operations. This paper addresses current applications of the systems, fire and heating identification rates, application of systems in dieselized coal mines, system maintenance, and employee training requirements. While deficiencies were identified in some applications, results of the studies and survey indicate the use of atmospheric monitoring systems can be effective in identifying mine fires and heatings.

Jan 1, 1991

By L. M. English, Y. J. Wang

When plotted as head vs. volume, fan curves start high and decrease with increasing volume, while mine head curves start low and rise with increasing volume. Their intersection is the system operating point. However, as every ventilation instructor knows, the fact that head loss is a negative number (debit) and fan head is an energy addition (credit) is often a stumbling block to student or audience comprehension since the curves seem to reflect the opposite. It is possible to use the intuitively correct curves- pressure losses as negative values and energy additions as positive values - and still obtain the correct operating point. Adding the two curves produces a third curve that intersects the x-axis at the operating point, the point at which the fan energy input exactly matches air circulation energy loss. Using this technique also makes it easier to account for outside influences on the system, such as natural ventilating pressure. With the standard approach, it is quite easy to add or subtract such influences to the wrong curve. This approach can be extended to the graphical solution of any series/parallel ventilation network. The results are the same, and the approach is logically consistent and less confusing.

Jan 1, 1999

By Steve Kral

When discussing stock market investments, a company's performance is important. But so is the financial community's perception of that performance. To be sure, a good product or service, coupled with sound manage¬ment, remains important but is no longer enough. How stock analysts view a company's performance has become equally important. A major task of a mining company's investor relations officer, then, is to build and maintain a positive perception of the company to mining analysts throughout the world. That's a tough assignment in any market. The subject here, though, is gold. And, with its weakened price, gold companies must work harder to convince analysts their company is still a good investment. The analyst, on the other hand, must see through the corporate hype and decide whether it's worth recommending to clients as an investment. No simple task, either. Annual reports, 10-K forms, and quarterly reports only tell part of the mining company's story. Site visits, complete with discussions (sometimes interrogations) with a mine's principals, oftentimes tell an analyst more about a company's investment potential than the annual or quarterly report. So it was that three of the nation's major gold companies arranged a three-day tour of their gold operations in Nevada for a group of 22 analysts and a pair of mining industry scribes. The analysts represented investment houses the US, Canada, and England. The host companies and mines visited included FMC Gold's Paradise Peak mine, Amax Gold's Sleeper and Wind Mountain mines, and Battle Mountain Gold's Surprise and Fortitude mines.

Jan 1, 1989

By C. Cassios

EIA is a procedure aiming the elimination of adverse impacts to the environment from undertaken projects. Historically, it starts in 1969 when NEPA (Nat.Env.Prot.Agency) in the US initiated the EIA ? EIStatement. The EIA procedure was adapted by the European Union with the directive 337/85 and in Greece the Common Ministerial Decision 69269/90 enforced it to the Greek legislation. However, mining enterprises in Greece long before the implementation of the European Directive and in accordance to the legislation of the Public Law 998/79 for the protection of the forested lands were obliged to submit EIA?s and get an approval in order to operate in forested areas. The submitted and approved EIA?s and their implementation by the mining companies were among the positive aspects of the EIA procedures. This paper is examining the impacts of EIA?s in the Greek mining industry its positive aspects as well as their difficulties and their role for the reclamation procedure. The technical and procedural aspects which EIA presents for the mining industry are commented, while proposals, for a more flexible EIA implementation for the Greek Environment are also presented.

Jan 1, 2002

By M. A. Cocquerel

INTRODUCTION Davy McKee have developed and patented a combined mixer settler (CMS) which has undergone extensive trials and has now been installed in two commercial uranium plants in South Africa. Substantial capital and operating cost savings can be realized over conventional mixer settler in uranium extraction, especially from dilute feedstocks containing approximately 200 ppm U308. Pilot plant work has also been undertaken on other metal extraction systems and the results are very encouraging in most areas of interest. CONVENTIONAL MIXER SETTLERS The conventional plant in use at many uranium recovery facilities consists typically of a mixer box in which the aqueous and organic phases are contacted and a settler in which the two phases separate. The mixer box must allow sufficient residence time for the mass transfer kinetics to be satisfied for the particular species involved. The settlers are usually rectangular and take the form of shallow tanks of large cross sectional area.

Jan 1, 1984

By Todd A. Duex

The Richmond Hill Mine has recently completed a reclamation plan to mitigate Acid Rock Drainage (ARD) which was identified at the toe of the former waste rock pile in 1992. Reclamation activities began in 1994 with the removal of ARD material from the waste rock pile and placement of this material in the former pit. This material was then isolated from the near surface environment by a low permeability capping system designed to minimize water and oxygen flow into the material. The capping system consists of, from bottom to top, six inches of limestone, 18 inches of low permeability clay liner, 4 and one-half feet of thermal barrier/drain layer, and six inches of topsoil. This capping system was completed in 1995. An extensive program is in place to monitor the effectiveness of the reclamation plan, and includes measurements on moisture content movement, temperature, oxygen content, and groundwater impacts. Monitoring has been ongoing since the completion of reclamation. This monitoring plan is demonstrating the success in isolating the material from the near surface environment and minimizing the impacts to the surrounding environment.

Jan 1, 2000

By J. J. Davis, C. A. J. Fletcher, M. Li, T. Jancar

This paper summarises the experimental approach to spiral modelling at the Julius Kruttschnitt Mineral Research Centre, University of Queensland, involving the use of plastic density tracers to determine partitioning performance on three models of coal spiral. This work has led to phenomenological models of the three spiral profiles most widely used in the Australian coal industry. The results from a parallel computational fluid dynamics approach to spiral modelling currently underway at the University of New South Wales are also presented. The computational simulation has been successfully applied to generic spiral geometries and is capable of predicting the fluid phase three dimensional flow fields and corresponding free surface profiles for moderate Reynolds' number and Froude numbers. Simulation predictions are compared with experimental results from a Mineral Deposits LD9 coal spiral.

Jan 1, 1995

By Richard J. Adams

Coal jigs have played a predominant role in U. S. coal preparation for fifty years. Recently, an improved fine coal jig has been used to prepare the middle size range coal. These efficient machines are changing the historical thinking about jigs and is consistent with trends in coal preparation throughout the world. The performance achieved and operating cost savings are causing a change in fine coal cleaning strategy. With the exception of a handful of operators, fine coal jigs are generally not well understood by the industry. The objective of this paper is to provide some insight into the past use of fine coal jigs and their potential in the future. Improved Fine Coal Jig Since the mid 701s, an improved fine coal jig has been employed to an important niche in preparation, the 19 mm x 100 M range of cleaning. Several factors due to mining and liberation considerations have caused an expansion of this middle range of coal resulting in a host of challenges for coal preparation engineers. Fine coal jigs have been commissioned in several installations in North America to handle these important applications as shown in Table No. 1.

Jan 1, 1988