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By Roderick G. Eggert, John E. Tilton

During much of the 1970s and 1980s, world metal consumption grew more slowly than during the 19505 and 1960s. The slowdown contributed to surplus capacity and low real prices because actual consumption was consistently less than expected as new mining and mineral processing capacity came on stream. Over the last year or so, however, world metal consumption has picked up noticeably, raising the question, Has metal demand returned to the long-run growth rates more typical of the 1950s and 1960s than of the 1970s and 1980s? This paper examines this possibility and, more generally, assesses the factors that will shape demand for the major metals over the longer term. TRENDS IN METAL CONSUMPTION The extent to which metal consumption has recaptured the brisk growth rates typical of the 1950s, 1960s, and early 1970s is shown in Figure 1. This figure traces the consumption of crude steel, primary aluminum, refined copper, refined lead, and refined zinc between 1960 and 1987 for the western world, consisting of the OECD countries (including the United States), and the developing countries. Consumption increased in 1987 for all five metals, and preliminary data for the first six months of 1988 suggest even more substantial increases, at least for the United States (U.S. Bureau of Mines, 1988). However, Figure 1 also shows that the recent increases in consumption are not untypical of similar surges during earlier periods of economic expansion and thus may reflect only cyclical or temporary factors. In short, the available data are unable to provide a clear indication of whether recent increases in metal consumption reflect the beginning of a new era of faster growth or simply a cyclical and temporary upturn associated with the expansionary phase of the business cycle. Consequently, to pursue this issue, we are forced to examine the underlying forces that will shape metal demand trends over the next decade. The approach we have taken involves two steps. The first examines the prospects for overall economic growth. The expectation is, the faster the economy expands, the faster the production of metal-containing goods grows.2

Jan 1, 1989

By Leonid Pevzner, Valerie Dmitriev, Yuri Babitchev

Performance of belt conveyors, service life of belts and mechanical elements can be radically improved if the automatic adjustment of the belt speed movement is made in such a way, that the unit load over the conveyor length be constant and close to the rated one under random input freight traffic. Such an adjustment is possible when the system of a controllable thyristor electric drive on the basis of induction squirrel cage motor is used. Computer-aided adjustment of the belt conveyor movement is effected via bicontour digital control of the main drive in order to redistribute loads when the loading of conveyor and contour of the control of tension drive are changed. The system envisages control and condition monitoring of the conveyor electromechanical system, as well as metering of electrical power and the amount of conveyor freight. The results of the simulation of speed control of the conveyor belt are given in the report. Mathematical model of the conveyor electromechanical system describes the movement of the belt with cargo and the tension drive. The input cargo traffic is assumed as stationary ergidic random process with the assigned characteristics. The solution of the problem of the synthesis of a closed-loop control system, the structure and parameters of adjustment, the conditions of asymptotic stability of the control back-up system and the condition of minimization of mean square error of shadowing are also given in the report. Microprocessor controller is used to realize the function of the adjustment unit. Under this control system standard mode of conveyor operation, different modes of start-up, operating mode with decreased speed when transporting people, service and emergency braking of a conveyor and some other modes are realized. The digital model of a conveyor as an instrument for decision making in case of emergency is used in those modes. MASTER TEXT Long-standing practice of belt conveyor operation in mines of Russia has proved their inefficient use with 40-70% capacity and 20-25% availability factor. It is associated with unreasonable power intensity and reduction of service life of mechanical components, and as a result, with the growth of total transportation costs. Low efficiency of conveyor application can be explained by the extremely irregular distribution of conveyor freight traffic. Usually, the width of a conveyor belt is identified in accordance with the possible maximum traffic value, engine power capacity for long-term operation under rated loads. However, actually a conveyor often runs without any load and its average load in most cases is lower than the rated one. The problem can be eliminated by way of the adjustment of the operational mode of a conveyor according to an actual input freight traffic via belt speed control providing for the conveyor regular linear load which is nearly equivalent to the rated one. Experimental research into freight traffic under working conditions of the operating underground and open-cast mines proves the fact that the actual freight traffic can be adequately presented through the model of stationary random function of time, for ex- ample, as a J (t) continuous random Gaussian process that is modulated with a G(t) elementary pulse flow:

Jan 1, 1996

By A. P. Cook

Methane drainage on a mine-wide scale is a relatively new technology to South African coal mines. Shallow seams and apparently low methane contents have been assumed to result in less methane problems than experienced in other countries. The introduction of deeper mines however, has now resulted in methane drainage taking on a higher priority. Methane contents in the region of 12 m3\t have resulted in one colliery introducing drainage as a ventilation support. Although a low seam permeability initially indicated reduced potential for drainage, early borehole flows of 90 m3\m\year have since increased to 450 m3\m\year. Rapid inflow of methane into goafs and sealed areas from seams surrounding the main production seam at another colliery have warranted extensive evaluation of the methane properties of these seams with the projected introduction of predrainage from surface. Methane pressures in excess of 1000 kPa and contents in the region of 10 m3\t again give methane volumes suitable for drainage. Coal seam drainage ahead of mining is becoming more significant and is likely to see an increase in the near future. INTRODUCTION Methane gas is an everpresent hazard associated with underground coal mining. Safe working levels of methane in the mine atmosphere are normally maintained by ventilation practises, ensuring sufficient dilution of the gas. However in some cases the ventilation must be assisted by methane drainage, either from the mined seam, or from adjacent seams and strata, or from goafed areas. South African collieries have practised only limited methane drainage until now. Relatively shallow mining depths, and apparently low in-seam methane contents have been assumed to result in fewer problems with methane than are the normal for other countries. This is now being shown to not necessarily be the situation. Work carried out by the Coal Mining division of COMRO (Cook and Erwee, 1991) indicates South African production coal seams have very similar methane retention properties to those of coals in other countries, with seam gas contents of up to 12 m3/t. This awareness, as well as greater mining depths, and higher degrees of mechanisation, has resulted in higher priority being given to methane emission problems throughout the industry. Increased levels of safety, as well as possible commercial applications, are the main reasons for the interest now being shown in methane drainage. Not only is there possible applications in the present production coalfields, but South Africa has vast areas of coal reserves which are presently non-mineable, now being seen as possible alternative energy sources. Limited methane drainage is practised within the industry, but only on collieries that have identified specific methane problems that can be alleviated by drainage. Historically this has been restricted to surface drainage of longwall goafs, reducing emissions onto the faces. More recently, horizontal in-seam holes have been drilled, until now for bord and pillar sections, but the results are being evaluated for later application to shortwall faces. Adjacent seams pose problems at some sites and vertical and cross measure boreholes are now being considered.

Jan 1, 1993

By J. L. Chakravatti

The movement of air from the surface, through the workings and then back to the surface, is the most important consideration in the ventilation design. The purpose of mine ventilation is seen as the maintenance of acceptable atmospheric environments wherever men work or travel underground; and acceptability is related to the risk of harmful biological responses associated with exposure to atmospheric environments in mines. In mine ventilation, a design engineer often has to contend with a number of problems not experienced to the same degree in other industrial situations; i.e. the vast extent of many workings - offering continuously moving work locations; the difficulty of predicting. inflows of contaminants to the airways which contain the micro-environment; and especially, the effect of mining activity within the duct system (e.g. mine roadways) carrying the airflow. Mining of uranium does not differ, in many respects, from the mining of other metals; the ore must be drilled, blasted and transported from the mine. Underground mining proceeds by the continous development and advancement of a network of passages and rooms or stopes from which ore is excavated. As in most mines, rock conditions and ore grades in uranium deposits very from area to area and between different mines. 1 In uranium mining, in addition to eliminating noxious gases from blasting, diesel equipment exhaust, and the control of dust, it is also necessary to dilute and remove radon, the gaseous element in the uranium chain and its decay products. Long term epidemiologic studies of United States uranium miners and that of miners in Czechoslovakia have confirmed that there is an association between excessive ex¬posure to radon daughters and an increased risk of lung cancer. The common practices for controlling these airborne contaminants are: (1) the circulation of large volumes of fresh air from surface to dilute these contaminants to a permissible concentration, and (2) the sealing of worked-out areas to prevent ingress of radon into ventilating air. 2 The sealing of worked-out areas can be easily and effectively accomplished, but the contaminants intro¬duced from the workings may raise the concentrations in the airways despite a good ventilation system and use of the maximum available amount of fresh air. The ventilating air can be strategically filtered to reduce dust and radon daughters to acceptable levels, and reused prior to final discharge. This strategy properly applied, will decrease the air colume requirements in certain marginal areas of the mine and thereby avoid an overall increase in the mine airflow. This is particularly advantageous in the cold climates of Canada, where the incoming fresh air must be heated in the winter months to a comfortable temperature, Thus, an economical and technically feasible air filtration system, strategically placed, can improve the underground mining environment and reduce the overall cost of ventilating the mines. In addition to affording flexibilty to the venti¬lation system, a potential saving of $1,500/m3/s/year would be realized if air is successfully cleaned and reused when compared with the conventional methods of generating an air current. 3 Denison is justly proud of its achievements in the air filtration technology development. This paper limits itself to an examination of the radiation control aspect of the air filtration strategy.

Jan 1, 1980

By V. Steinbach

Non-renewable mineral raw materials are grouped into three categories to investigate ways leading to sustainable use of natural resources: 1.) metallic resources, 2.) non-metallic resources with the exception of the fertilizer minerals, and 3) the fertilizer minerals for the nutrients nitrogen (N), potassium (K), and phosphorous (P). With the exception of minerals in Group 3 which are essential for plant growth, mankind does not need raw materials as such, only the intrinsic property of a material that fulfils a useful function. This is especially true for non-metallic materials. Metallic resources have the best chance to become renewable if one makes optimal use of the resources of the man-made technosphere. For the fertilizer elements K and N there does not exist a problem, because sea water or air respectively provide an inexhaustible source for them. This does not apply to P however. So P is serving as one of our apposite case studies for solving sustainability challenges. For all the challenges along the road from a non-sustainable to a sustainable resource economy technology can be envisioned to come to the rescue provided conditions that are considered to be essential for sustainable use for all natural resources-- affordable renewable energy and human ingenuity to find new solutions for functions, to optimize processes and to minimize losses-- are satisfied.

Jan 1, 2011

By Stanley Dempsey

INTRODUCTION The mining industry has been under- going a significant restructuring for the past several years. Some firms have been liquidated. Some have been merged with other firms. A number of mining divisions of larger firms have been spun off, in some cases in leveraged buyouts by management. Recently, there have been a number of spin outs of gold subsidiaries. There are also a number of start-up situations where new firms are emerging as significant gold producers through mine development or acquisition. This restructuring has created an attractive market for specialized mining finance firms, and a number of firms have recently entered that field in the United States. These firms provide financial advisory and valuation services to mining firms and project developers, and access to venture capital. In some cases, they invest for clients or for their own account. I have been asked to describe how our firm works, and what kind of information we expect to receive when mine developers seek our assistance in financing a project. HOW WE OPERATE Denver Mining Finance works for both mine developers and investors. We also provide expert advice on mining issues to governments and to firms who are in litigation over mining issues. A lot of our work involves valuing mineral interests for various purposes. Our principal expertise is in the technical, commercial, and financial area. We help put mining deals into shape commercially so that they can be financed, and we help investors get into mining deals that are commercially sound. We work on projects, but we also advise mining firms on the structure of their business and how to make the most out of one or several mines that they might own. In addition to our work for clients, we are also prepared to invest in mining projects for our own account, and to recommend gold properties for acquisition by our parent company, Royal Gold, Inc. We are, to some extent, a venture capital firm, in that we sometimes work with projects that are not "bankablerV1 and are prepared to invest in attractive early-stage situations in mining. However, I want to emphasize that our principal focus is on development of commercially attractive mining projects that can be brought into production in the best possible financial terms. If we can make a project qualify for a project loan from a commercial bank, we will not advise the developer to use high cost venture capital. For the purpose of this paper, I will focus primarily upon our functions with respect to development of precious metal projects. In a typical case, a firm with an advanced-staged project approaches us for help with financing the final feasibility study, and construction and operation of a mine. In some cases, the developer has already developed a financing plan and wants only our access to investors. If we agree that the project is sound and that the financing scheme will be attractive to investors, we will help the developer reach investors on a commission basis. In such cases, we are particularly insistent that the financing plan and our participation meet all regulatory requirements, particularly compliance with state and federal securities laws. In most cases, however, the developer asks us for advise both on how to structure the financing, and how it can be implemented. Here we work for fees based on hourly rates for advisory work,

Jan 1, 1987

By Priscilla P. Nelson, Francis L. C. Fong

Introduction Fracture mechanics is the study of the behavior of cracks and their modes of propagation. During cracking, energy is consumed in creating new surface area. The more energy a material absorbs, the higher is its fracture resistance. This fracture energy is provided either by work done externally, by the release of elastic strain energy within the cracked body, or by a combination of these two effects. Fracture resistance is measured in terms of either the stress intensity factor, K, or the energy release rate (also referred to as crack driving force), G. For linearly elastic materials, these two quantities are related by the following equation: [ ] where [u] is Poisson's ratio and E is the modulus of elasticity. Both K and G are direct functions of the applied force and the crack length. The process of rock cutting with full-face tunnel boring machines (TBMs) involves the indentation of a rock surface by rolling disc tools. Excavation occurs as fractures, extending from the locus of chip indentation, propagate between concentric disc grooves and liberate rock chips from the intact rock face. Since disc cutting is achieved by a fracture process, it is logical to anticipate that differences in cuttability of a variety of rocks should be related to the variation of fracture material properties among the rocks. Such a relation has been demonstrated between the performance of full-face TBMs and the critical crack driving force for excavation in relatively high strength, brittle, low porosity, isotropic rock (Nelson et al., 1985). The objective of this paper is to report on the results of a continued investigation of the relationship between fracture material properties and the effectiveness of disc cutting. Additional reliable data on full-face TBM performance is difficult to obtain, so that the results of disc linear cutter tests performed by the Transport and Road Research Laboratory (TRRL) (U.K.) are utilized in this study. Fracture Material Property Evaluation If a crack tip is subjected to a perfectly plain strain condition, many materials will behave in a brittle manner, and the material resistance to fracture is constant during crack growth. This resistance is referred to as the plain strain fracture toughness, believed to be a material property. The standard testing procedure for this parameter is given in the American Society for Testing and Materials (ASTM) test designation E399. To ensure plain strain conditions, acceptable specimen geometries are specified. Unless these geometric specifications are adhered to, the measured fracture resistance is regarded as the apparent fracture toughness, and a subscript Q is used, as [ ]. The methodology adopted by ASTM E399 is within the framework of Linear Elastic Fracture Mechanics (LEFM). This approach assumes that material resistance against cracking is developed instantaneously, without initial stable or subcritical crack extension. Prior to crack advancement in rock, however, much of the crack driving energy is absorbed in a localized volume in front of the crack tip, referred to as the plasticity or microcracking zone. This capability for energy absorption substantially increases material resistance, and a crack may be arrested unless an increased crack driving force is applied. The LEFM or plain strain assumptions would underestimate the actual fracture resistance of such a material. Such a conservative approximation may be desirable in the design of structures against fatigue or brittle failure. In mining or tunneling, however, an underestimation of crack resistance can lead to the selection of underrated excavation equipment and a decrease in production efficiency. The development of fracture resistance in rock is best described by the material resistance curve, or R-curve, which is a plot of fracture resistance as a function of crack extension. Typically, peak resistance is only reached after a finite amount of subcritical crack growth. The

Jan 1, 1986

By Qinghua Song, Jianhong Chen, Shan Yang, Zhiyong Zhou

"The development process of Metal Resources Technical and Economic Evaluation Expert System (MRTEEES) is introduced in the aspects of requirements analysis, design of the expert system, main functions of the expert system and features of the expert system. The system is based on C/B/S mixed mode and uses ASP.NET technology with .Net Framework being chosen as the development platform and metal resources database providing data support at the bottom layer. The system is an auxiliary management system for metal resources technical and economic evaluation and has the basic functions of auxiliary decision analysis, metal resources database management, data management and comprehensive query. Technical and economic evaluation model can be set up by users independently according to at which stage a project is, mainly including exploration stage, development stage and production stage, and according to the mining methods, for example underground mining, surface mining and in-situ leaching mining. Then, the technical and economic evaluation parameters can be generated. By inputting the value of each parameter in a simple and convenient way, the evaluation results can be directly calculated out and shown in the form of diagrams among others, and feasibility evaluation report can also be automatically generated, making the technical and economic evaluation process accurate and efficient. As the system can achieve the functions of scenario analysis, sensitivity analysis, shareholder’s returns analysis, horizontal comparison of different projects, it can improve the ability of project senior decision makers for rapid response to the rival and meet the demand of pricing negotiations. IntroductionWith the arrival of a new round of industrialization upsurge in both developing and developed countries, growth of demand for metal resources is entering a new stage. Population involved in the new industrialized countries is about four times that of all previous industrialized countries, implying resource consumption increases dramatically both in speed and in quantity. It is a must to seize the strategic opportunity of developing and utilizing metal resources around the world to lay abundant resource base for national industrialization. Objectively speaking, global configuration of metal resources is an inevitable tend. Presently, many issues, for example, resources exploration, mining, merge of mining companies, metal trades, mining financing, etc., generally show the feature of globalization. For the reality that competition for metal resources is becoming fiercer, industry standards of mineral resources will undoubtedly be improved. Occupying large scale mineral resources with high grade and developing them with low cost is the base for the survival of mining companies and metal resources merchants. With the growing demand of global investment in mineral resources exploration, which is at the upstream of the industry chain, geological exploration industry is promising. Globally building market relationships for mineral resources exploration companies is key to their sustainable development. Developing large and super-large deposit with low cost is also an important approach to enhancing core competence of a country or an enterprise. Mining companies around the world are rushing to purchase mineral resources globally. However, in different countries, economic, financial and tax systems for mineral resources vary greatly, and mining and processing techniques, technical parameters and equipment selection also change a lot. Thus, pro-phase research work is necessary for feasibility evaluation of mineral resources projects and it can be time wasting if taken in the traditional way. It is necessary to accelerate the process considering the complex and rapidly changing international situation."

Jan 1, 2017

By Harold Stocker

INTRODUCTION This presentation is concerned with the administrative and technical capability of the Atomic Energy Control Board (AECB) to assure compliance with the individual exposure limit for radon daughters (currently 4 WLM per year). It is not concerned with the epidemiological bases for setting the exposure limit. Moreover, the intent is to show how sophisticated methodologies and advanced technologies, applied to radon daughter concentration measurements in uranium mines, convey the spirit of compliance by providing better estimates than do the historical methods. These better estimates mean that more accurate and more precise estimates of each worker's exposure are determined using these more modern methods and devices. The estimates so derived should provide more convincing evidence to an individual worker that his assigned exposure is a valid indicator of his true exposure. In addition, a perspective on the exposure estimate in relation to the exposure limit is given as further evidence that an exposure limit is not the dividing line between "safe" and "unsafe" exposures. A brief description is given of the compliance aspects of the Atomic Energy Control Regulations and of the limitations of purely statistical non-compliance procedures. Most of the emphasis of the paper will be placed on the uncertainties associated with conventional radon daughter exposure determination and the means being employed (and anticipated) to reduce these uncertainties. NON-COMPLIANCE Under current Atomic Energy Control Regulations (1978), the annual individual exposure limit for radon daughters is given without reference to the possible methods of sampling and calculation of radon daughter exposure and without any reference to possible uncertainties or their magnitudes. This is common in such statutes, the details of sampling, calculation, error analysis, and so on, being left for licence conditions or provided as a specific guideline to the licensee on the matter of compliance with the Regulation. Since the exposure limit is contained in the Regulations, compliance with it is absolute, as with any other law. In Canada, a state of non-compliance with the radon daughter exposure limit exists when an exposure (attributed to an employee) is reported by the licensee to exceed the limit. No uncertainty in the measurements or in the overall determination of exposure is reported nor is any requested. Removal of the worker and the loss of his services are the immediate and direct penalty suffered by the licensee for failure to maintain the exposure at, or below, the limit. A worker may be re-instated to employment for the balance of the reporting period only if the licensee can assure the AECB that further significant exposure to the worker will not ensue. In other jurisdictions, such as the United States, non-compliance is defined on a statistical basis. For example, NIOSH, the National Institute for Occupational Safety and Health presents procedures for calculating the 95% Lower Confidence Limit (LCL) in order to "compare the results of occupational environmental sampling to an occupational health standard and make a decision with a known chance of making an incorrect decision that a state of non-compliance exists" (Leidel and Busch, 1975). (In the nomenclature of this presentation, exposure limit would be used in place of "standard", in the NIOSH sense). Furthermore, it is emphasized in the NIOSH document that such numerical comparisons "are necessary only if the sample mean is greater than the standard". The NIOSH document points out, quite correctly, that the "statistical procedures presented below will not detect and do not allow for analysis of highly inaccurate results, i.e., systematic (non-random) errors or mistakes ... If a systematic error is known to exist in an instrument or analytical procedure then correct the sample mean of the data before analyzing for non-compliance". It is certainly not the purpose of this paper to criticize the sophisticated statistical approach to non-compliance as given in the NIOSH document or in similar approaches used in other jurisdictions. Rather, the purpose is to approach, with some introspection, the question of the determination of exposure by the employer for his employee and especially the employee's understanding of, and confidence in, the accuracy of the exposure determination and its relation to the exposure limit. DETERMINATION OF EXPOSURE Historically, in uranium mines, exposure to radon daughters for an individual miner

Jan 1, 1981

By S. F. Walsh

The San Manuel Oxide Pit is located within the subsidence boundaries of Magma Copper Company's block caving operation. Ground conditions offer a constant blasting challenge and vary from hard, competent crystalline rock to widely spaced fracturing in a sedimentary conglomerate. A successful drilling and blasting program has undergone several changes since mining commenced in 1985 and continues to be developed. This paper discusses the site specific progress made with the drilling and blasting program from selection of feasibility parameters to current practice. Topics discussed include controlled blasting, use Of high energy blasting agents, charge decking, blast casting, as well as standard drill and blast techniques.

Jan 1, 1988

By D. Olsen

The paper discusses the legislative and practical approach adopted to problems of management of environment in relation to coal mining in a very sensitive area of the south coast of New South Wales. The environmental problems are complicated in this area due to multiple and very often conflicting land usages. The environmental approach in relation to water quality maintenance, noise control and air quality is discussed and methods adopted meet stringent requirements. Requirements of New South Wales Regulations on Environmental Impact Statements (EIS) are described.

Jan 1, 1988

By Ronald B. DeDiemar

It is generally held that cone crusher application technology is strictly an art and thus subject to the vagaries of emphirical and/or trial and error judgments. While this is basically true, certain factors have been identified which, when properly defined, can significantly reduce the element of chance. This paper will bring out these factors as well as pointing out other technologies available to predict and/or analyze cone crusher performance.

Jan 1, 1977

By John Fred Rivera

Since its inception during the hectic days of World War II, Kaiser Steel Corporation has developed and maintained a solid reputation as a progressive company with an incessant penchant for attempting innovative ideas to improve its stature in the American and world corporate framework. The very latest in technology is aptly demonstrated in the new Basic Oxygen Process recently placed into operation at Kaiser's huge Fontana Steel Mill. Daring ventures such as this and other developments on pollution control devices have propelled Kaiser Steel Corporation into the forefront as the largest steel producer in the western United States. Kaiser Steel's boldness and willingness to attempt new ideas and the very latest in technology is by no means limited to its steelmaking operation. It extends into every phase of Kaiser's corporate structure.

Jan 1, 1979

Two key strategies for a new generation of mining are developing domestic raw material production and doing so in an environmentally responsible way, according to presenters at the 83rd annual meeting of the SME Minnesota Section in Duluth (the 71st annual University of Minnesota Mining Symposium). From technical sessions detailing how to build com-munity support, to a short course on international perspectives in iron ore mining and processing, the two-day meeting emphasized the potential of Minnesota state deposits and the importance of maintaining productive community relations both locally and globally. The meeting of more than 300 mining industry professionals began on April 20 with a traditional convocation celebrating the values of northern Minnesota. The accompanying tradeshow, with a record 131 booths, showed the speed and vigor of the economic rebound. Keynote speaker Scott Anderson, vice president and senior economist at Wells Fargo, stated the prevailing mood of the conference: ?Wow, what a difference a year makes.? With metal prices and sales up and heading higher, he said, it was clear that the production-centered economic recovery is reaching the mining and the minerals industry. However, Anderson sounded a few notes of caution. Serious threats to economic stability remain, including the burgeoning national de?cit, high unemployment and the still out-of-control foreclosure crisis. Overall, he predicted a below-average recovery and stressed the importance of developing a long-term business strategy.

Jul 1, 2010

By Karel Rössler, Petr Vítek

"The Ejpovice tunnels in Czech Republic were built by EPBM in soft Clyashale, and in weathered profile with low soil overburden. The segmented liner at the cross-passage openings required support, which would not interfere with the EPBM clearance envelope during the scheduled pull back of the EPBM through both tunnel tubes. For that reason support frames or radial bolting could not be used. Steel rods inserted into the neighboring segments during the ring assembly, and later grouted were tested and realized as an innovative solution. The paper presents practical experience gained with the segmented liner support during cross-passages construction. INTRODUCTION An innovative solution using the grouted dowels was developed and realized for sixteen cross-passage openings of the twin Ejpovice Tunnels, whose construction was part of the railway track Rokycany – Plzen modernization. The following paper described practical experience gained with the innovative support of cross-passage openings, which was realized by short steel dowels grouted within the segments of the EPBM segmented liner. The paper is a continuation of the paper published in WTC 2015, which described the design aspects of the grouted dowels support, while the following paper concentrated on the production, and the performance of the dowel support observed during the breakout for the cross-passages openings. The connection by grouted dowels was patented by Metrostav, a.s. Company THE EJPOVICE TUNNELS CONSTRUCTION The Ejpovice tunnels construction started in 2013. The start of the high speed train operation through the tunnels was planned for 2018. The project was funded by the state government with the support of European Union funds of up to 70%.The tunnels were excavated with one EPBM (Earth Pressure Balanced Machine) with the external diameter of 9.89 m. The segmental liner inner diameter was 8.7 m, and thickness of 0.4 m. First, the South tunnel tube was excavated from the East portal, then the EPBM was pulled back through the South tunnel, and the excavation was started from the same portal for the North tube. After the South tube was freed from the EPBM excavation operations the cross-passage construction started. Due to the short time schedule, in the North tube the cross-passage construction started while the tunnel was still under construction. Therefore, the cross-passage construction was performed concurrently with the segments transportation, and with the EPBM pull-back through the tunnel. There were 8 cross-passages along the tunnels with a maximum distance of about 500 m, Fig.1."

Jan 1, 2016

By Lawrence R. Molsather

Certain hydrologic parameters are affected by development of a mine. These include the area, yield, and storage in a watershed. Alteration of these parameters results in variations in lake levels and stream flow rates and in changes in ground water elevations and gradients. These factors have become increasingly important in light of present environmental design standards and government regulations. Mitigation of adverse hydrologic impacts can be costly and can create operating constraints which complicate the mining process.

Jan 1, 1980

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By A. D. Hammond

"INTRODUCTION Vanadium deposits in Arizona are distributed all across the state, from the rim of the Grand Canyon to the Tombstone mining district in the southeast corner of the state (Figure 1). The combined past production of vanadium from Arizona and New Mexico ranks second nationwide, after deposits in the Colorado Plateau In the northeast corner of the state, in the Carrizo Mountains and Monument Valley of Apache and Navajo Counties, vanadium was produced as a by-product of uranium in deposits of the Salt Wash and Shinarump members of the Morrison and Chinle formations, respectively. The production took place between 1943 and 1970. Another source of vanadium in Arizona occurs in vanadate deposits associated with supergene enrichment of base-metal vein and replacement deposits. The most important vanadate mineral is vanadinite, a chloro-vanadate of lead. Presently, there are no primary mines of vanadium in the United States. In 2012, a small production of vanadium pentaoxide (V2O5) was reported as a by-product of uranium at the White Mesa uranium mine in Utah1. This paper describes vanadate deposits in Arizona with emphasis in three districts, namely, the Mammoth, Globe-Miami and Banner districts.VANADIUM EPIGENETIC DEPOSITS: VANADATES Almost all vanadium epigenetic deposits occur as vanadates in oxidized zones of lead, zinc and copper veins and replacement deposits. Vanadinite, descloizite and mottramite are the most common minerals in vanadate deposits. Descloizite is a vanadate of lead, zinc and copper. Wulfenite, a molybdate of lead is also present. These minerals replace supergene base-metal minerals, form crusts on faces of open cavities, or are inter-grown with residual clays in pockets. The vanadium content in vanadate deposits is believed to have been leached from the country rock by ground-water and transported through porous rocks until precipitating as a relatively insoluble vanadium compound or until the solution evaporated. Precipitation was brought about by local concentrations of cations of divalent lead, zinc or copper. Lead is a constituent part of almost all of vanadate deposits and the vanadium pentaoxide (V2O5) content in vanadate minerals seems to have a direct correlation with the content of lead in the hypogene mineral. Vanadate deposits are restricted almost entirely to the oxidized parts of vein or replacement deposits. It is rare that oxidized zones extend past 100 ft from the surface. Vanadate deposits are largely restricted to tropical and temperate zones and regions of dry climate. Arizona and New Mexico have the largest concentration of vanadate deposits in North America."

Jan 1, 2015

By G. Jalkanen

Dealing with a trend in inverse distance estimation, IWD, is presented. A measurement is proposed to be consisted of a portion due to a mean and a portion due to a residual. The procedure consists of de-trending the measurement via a linear or nonlinear regression. Residuals are computed, and IWD parameter estimation is conducted on the residuals. Estimation at un-sampled points is then computed by estimating the mean and adding on the estimate of the IWD on the residual. A possible BOXCOX transform is also proposed.

Jan 1, 2010

By T. Rockley, B. Goertz, S. McDaniel, J. Brune, K. Bakhsh

"Researchers at the Colorado School of Mines, under a project funded by the Alpha Foundation, have developed a working prototype of a dust sample collection device designed to determine if sufficient rock dust has been placed in an underground coal mine to prevent coal dust explosions. When used in conjunction with the Coal Dust Explosibility Meter (CDEM), the device will provide near instantaneous results on the quality of rock dusting at the tested location. The sampling device applies a pulse of air to a testing surface and collect a representative sample of mine dust based on the pneumatic entrainment process during a mine explosion. The use of both physical testing and Computational Fluid Dynamics (CFD) modeling has allowed researchers to refine the design to accurately represent the particle entrainment and optimize the sample size collected for the CDEM. The prototype is being tested in a mine environment to produce information of usability and practical aspects of mine dust sampling. This paper is a progress report summarizing the current status of sampler development. Researchers expect to have a fully developed and tested sampler in early 2016. INTRODUCTION Underground coal mines face the danger of methane and coal dust explosions. The disaster at Upper Big Branch mine (2010) has demonstrated the impact of a violent coal dust explosion that fatally injured 29 miners. Reviewing the history of coal dust explosions, researchers found that that mine operators and mine inspectors do not have a reliable method of collecting dust samples to assure that sufficient amounts of rock dust have been places to inertize the coal dust. This is a problem specifically with small mines that do not have dedicated safety departments to track rock dusting work. The aim of this research is to develop a simple, portable device that can help underground mine examiners collect dust samples from workings and test the explosibility of the sample near instantaneously. Researchers determined that the current brush-and-pan sampling method required by MSHA (MSHA 2013) is flawed in several aspects: Mechanical sampling with a brush exerts forces on the mine dust that may differ significantly from those present during an explosion. Also, U.S Bureau of Mines research (Nagy 1965) has determined that only the top 0.125 inches of the mine dust layer will be entrained in a coal dust explosion. Using a handheld pan and brush, it is difficult to correctly and repeatably sample a layer of this exact thickness. The following will describe the CFD modeling and experimental testing for the development of the prototype sampler. Researchers analyze the accuracy and performance of the prototype during the course of the build process."

Jan 1, 2015