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By David Brown, Adrian St. John, John Comins, Mike King

"INTRODUCTION The Crossrail project provides an East-West link across London enabling an additional 200 million journeys each year linking up major business centres and existing transportation interchanges, while reducing congestion at street level and within the current underground system. The project has built major structures in Sprayed Concrete Linings (SCL), including 5 new stations, 6 crossover caverns and numerous passages, adits and ventilation tunnels. Construction has taken approximately 4 years, and has involved the spraying of over 200,000m3 of concrete. At the start of the project there was a lack of available records from previous projects concerning concrete falls, which hindered risk assessments and the ability to make meaningful comparisons around spraying or material performance. This paper redresses this lack of data by providing information on falls experienced on this project and makes recommendations to assist future projects. Construction Methods Table 1 below summarises the main contracts with elements of permanent SCL. The listed primary lining lengths include pilot tunnels, side drift tunnels and enlargements as separate tunnels.A range of construction sequences were used in order to deal with the design requirements, geometry, and the ground and ground water conditions. The following briefly summarises the build up by layers, with typical design dimensions provided for a platform sized tunnel (approximately 9m internal diameter), excluding tolerance allowances. Some linings were sprayed in more than one layer to allow for inclusion of reinforcement layers or to avoid a too aggressive build-up of thickness: •,Initial shotcrete, or sealing, layer (ISL) of 75mm followed by a Primary Lining (PL) of 300mm. •,Regulating layer of 40mm followed by a Waterproof membrane (Sprayed membrane, 3-6mm). •,Secondary lining (SL) of 250mm with a separate sprayed fire protection layer (FPL) of 50mm."

Jan 1, 2016

By Joseph G. Wargo

The purpose of this paper is to investigate trends in exploration expenditures of a selected group of mining companies for the interval 1968 through 1971. The paper also compares these trends with other financial factors that are associated with various groups of companies and comments on the implications of these trends. Although a four-year interval is hardly enough time to establish a long-range set of trends from which operating rules can be derived, the fact that the four years selected are in the immediate past gives some sense of relevance to the matter of exploration expenditures at the present time and in the near future. The sample under study here consists of 21 mining companies. Of these, 19 are listed on the New York Stock Exchange and 2 are listed on the American Exchange. Twenty are American, one is Canadian. All are fundamentally "mining companies" in that they derive the bulk of their income from the extraction, sale, and at times, fabrication of metals from their own mines. This is in contrast to companies which have mineral exploration departments but derive the bulk of their revenues from sources other than mining; for example, from oil and gas sates, Also, no companies which can be considered strictly as exploration companies are included in this study. Although this definition held up fairly well when studying this list in 1968, the strict application of this definition became more difficult through the years up to the present time. In 1971, three or four of the companies were changing their character in that they were phasing out of the mining business, and either deriving their income or planning to derive a substantial part of their income from activities other than mining. A study of

Jan 1, 1973

By Timothy J. Matthews, Ted Klemetti, Timothy J. Batchler, Daniel J. McElhinney

Unplanned tailgate collapses and difficult mining conditions in U.S. longwalls have necessitated the use of innovative tailgate support systems. Severe ground movement induced by longwall loading has caused operators to utilize secondary support systems that can match yield and strength requirements with expected ground reactions. Standing support performance requirements depend on the nature of the ground deformation behavior, and therefore require a good understanding of the interaction between the support and ground to achieve an optimum roof support system. Mining operations often employ standing support strategies that are unique to their mine. A support system that functions successfully in one situation could fail in another situation. It is important that the design and installation of the standing support systems provide the highest probability of preventing roof falls. Pumpable roof supports are currently being used to provide a safe working environment for longwall mining. A full understanding of the impact of these performance characteristics is necessary to optimize the support application and to provide a foundation for making further improvements in the support performance. Optimization of roof support applications helps to ensure the protection of mine workers by preventing roof falls due to inadequate support design. The load capacity and stiffness characteristics of a 27-in.-diameter pumpable support system was evaluated using the National Institute of Occupational Safety and Health (NIOSH) Mine Roof Simulator (MRS). Previously, tests to evaluate the performance characteristics were performed on a single pumpable support. The goal of this new research is to evaluate the performance characteristic effects of the pumpable support system and compare it to an individual pumpable test examination. This research of a pumpable support system configuration simulates the current installation practices in U.S. coal mines.

Jul 1, 2023

By A. Goulsbral, D. Harrison, R. Dunne

A programme to reduce cyanide consumption at the New Celebration Gold Mine, situated 32kms South of Kalgoorlie, Western Australia, commenced in the latter part of 1990. Cyanide speciation studies at the time identified that the major loss and consequently consumption was due to the hydrolysis of cyanide, The use of artesian hypersaline waters of high magne­sium content on gold plants in Western Australian Goldfields has meant that economically viable operating pH values during cyanide leaching are around 8.9 to 9.5. The high ionic strength in these waters does to some degree retard the hydrolysis reac­tion. Notwithstanding this, the formation of hydrogen cyanide and its loss due to volatilisation is the cause of the major loss of cyanide on most gold plants in the Kalgoorlie Goldfields. This paper discusses the aspect of oxygen addition during cyanide leaching to decrease cyanide consumption and increase gold recovery.

Jan 1, 1996

By Alfredo P. Vargas

Industrial flotation of sulfide ores is 80 years old. It has gone through many advances to date. However most flotation operations are still struggling to improve performance, which as a worldwide average is at the 90% level. What can be done to push the ceiling to 95% or better without performing finer primary grind, nor without duplicating flotation plant capacity? Such "unique task" can be performed by the low volume high capacity new flotation equipment known as the JAMESON CELL, when used as, "post-scavenger" of final plant tails. Improved efficiencies are obtained mainly from two cases: -Particles which never contacted a bubble. -Particles sheared-off by cell turbulence due to reduced number of hydrophobic sites. The application reverses conventional trend of using large volume mechanical cells by trade-in with smaller efficient equipment: resulting in reduced capital expenditures and operating costs. Outstanding "pre-rougher" applications are also presented.

Jan 1, 1993

By J. Maiti, A. Bhattacherjee

A literature review on quantitative analysis of mine safely studies revealed that numerous investigators explored a wide- range of techniques, including the investigation of bivariate and multivariate statistical models. Although these researchers addressed various issues of accident causation and prevention, they, in general, did not investigate through the use of quantitative models the multivariate relationships of several factors affecting mine safety in a causal framework. In this paper, systems dynamics and structural equation modeling are presented to simultaneously represent and study the effect of policy variables related to accident prevention along with the factors causing accidents and injuries. The application of these models to a group of mines revealed that current training practices at these mines do not appear to alleviate accident occurrences. It is inferred that the use of these quantitative techniques can provide a new direction of research in mine-safety studies.

Jan 1, 2000

By Camillo Premoli

Namibia is one of Africa's newest nations. A German colony until 1915, it then became a South African protectorate until 1990, when it gained independence after an armed struggle that lasted more than two decades. However, no trace of past bitterness can be found today in the capital, Windhoek, or in the countryside. Namibia is now one of the safest parts of Africa. Namibia's industrial base and infrastructure have been untouched by war. Swapo, the ruling party, has embarked on a successful policy of reconciliation and economic development. The GNP per capita is a surprising $1500 (from the World Bank), one of the highest in Africa. Namibia's population stands at 1.3 million, including about 100,000 whites. Namibia is a very sparsely populated country (1.7 inhabitants per km2). About 70% of the people are farmers. Namibia has a surface area of 824,232 km2 (318,261 sq miles), about the size of France and Germany combined. The semi-arid climate and generally flat morphology make the country well suited to mineral exploration. About 40% of the country presents abundant rock outcrops. The rest is buried under the Kalahari sands. However, this cover in most of the country hardly exceeds 200 m (655 ft), and Australian technology has shown that large mineral deposits (Roxby Downs) can nowadays be found at even greater depths. Mining is Namibia's largest industry. In 1991, it accounted for 22% of the country's GDP, about 70% to 80% of its exports by value and 25% of internally generated government revenues. The Ministry of Mines and Energy (MME) is responsible for formulating and implementing national mineral policies. This agency has recently introduced legislation aimed at encouraging new and long-term investment in the mineral sector. The variety of Namibian mineral resources, both metallic and nonmetallic, is rivaled by few countries worldwide.

Jan 1, 1994

By Pierre J. Wauters, Eddy J. Jacques

Starting up a fan or modifying its setting point either by rotational speed variations or blade angle changes, obviously results in new ventilation conditions in the network, which is, of course, the object of the operation. However, since transient phenomena may then occur, particularly in complex networks, there may be a need to simulate these situations prior to any action. This is all the more true, if we are dealing with a multiple interactive fan sys- tem. Simulations with a transient model have shown that the flow in certain airways could be temporarily reversed due to the pres- sure variations that reach both its ends with a different time lag. This phenomenon may cause dangerous situations to occur in cases of fire or outburst of methane. It is also true that the air flow could be reversed in secondary and less powerful fans, while still rotating in the normal direction. The study and the experimental investigation of the extension of the reverse flow characteristic is therefore justified from two points of view : • a numerical simulation model for transient flow conditions must be capable of handling temporary reversed flows, and thus have appropriate fan characteristic curves available over the entire operating domain; • while operating fans, reversed flows should be avoided or at least reduced. Therefore, the design of start-up procedures or real time control algorithms should take these phenomena into account. A particular interesting application is the operating of two fans in parallel. In order to investigate experimentally the characteristic curves of a fan under reversed flow conditions a small scale model was built. This facility was designed in such a manner that it was possible to carry out experiments concerning flow reversions and to try out sequential start-up procedures for two fans in parallel.

Jan 1, 1997

By Gregory Witte

This paper will explore the technology behind and applications of smart motor control centers (MCCs) being used today in mineral processing facilities. The two technologies to be discussed are solid-state motor controllers that can be installed in MCCs and the complementary digital communication networks that can transmit operational parameters of the solid-state devices to the supervisory system. The toughness and reliability of solid-state technologies have led to a dramatic increase in their usage throughout the mining industry. Products such as solid-state motor protectors, controllers, and variable frequency drives have demonstrated greater flexibility and performance in a variety of applications than their electromechanical and mechanical counterparts. The three key trends apparent in the solid-state devices are: 1. A shift to smaller, smarter, more integrated devices, which allows a single solid-state device to serve the purpose of multiple electromechanical devices but in a much smaller form factor. 2. Distribution of control logic in motor control devices rather than conveyed through a hard wired connection to a central automation system. 3. Embedded network communication that allows supervisory systems to have an expanded view into critical loads and sensors. In applications, the use of smart actuators and sensors with integral local intelligence and communication allow a supervisory controller to send high level commands and let the smart device coordinate its own work The ability of smart field devices to return noncontrolled, nonpoled information opens a whole array of new capabilities for preventive maintenance and diagnostics and forms the basis for an effective motor management program. The smart motor control devices this paper will explore are the smart motor protectors (SMP), smart motor controllers (SMC), and variable frequency drives (VFD).

Jan 1, 2000

By Donald A. Dahlstrom

If you have ever driven on the Autobahns of Western Germany, you are well acquainted with the "fast lane." There is no speed limit; there are only two lanes in the direction you are going, and if you choose to drive in the fast lane, you had better be prepared to drive faster than anyone or someone will tailgate you with a constant screeching horn until you move to the "slow lane." The prize for this mastery of the fast lane is some kind of a "macho" feeling and getting to your destination sooner than your competitor. This has some comparisons with today Is liquid-sol id separation. We've certainly had our moments in the fast lane but we've also had other countries forcing us into the slow lane at times. It can be very embarassing when someone almost runs over your back and then shakes a fist at you as you shakily scatter to the much slower and overcrowded lane. Because of necessity, there will be many new improvements and added requirements in the next decades into the 21st century and beyond. Those countries and industries that can maintain the pace in the fast lane will be successful while the others may well be relegated to the non-competitive lane. Before considering what will be the challenges in the future for competitive liquid-sol id separation performance, it would be wise to review progress over the past forty years in this area. The author has to admit his ancient age and believes he can act as an evaluator of these many advances. To place the beginning of the 40 years (the author predates his initiation into liquid-sol id separation by one more year), the United States was still building smelters and operating them with little or no sulphur dioxide removal , practically

Jan 1, 1989

By Lennart Malmqvist

Decision-making in exploration deals with experience, knowledge, and sometimes faith, but very often financing and profit, mineral resource aspects, employment, and general political ambitions are parts of the scene. At one end of this spectrum, there is the prospector and his decision on the actual project. The exploration business now expands from its pioneering phase for the benefit of a single company to a wider spectrum which includes the benefit of the large mining consortium and a national development program. Its objectives are also to maintain employment and to favor long-term stability in a mining district or a mining company. The prospector then has new aspects and questions to consider such as, what to do in mining districts where there is a shortage of ore resources but there are still useful investments in mines, processing plants, etc. To analyze the exploration process, therefore, seems to be of great importance in a time of rapidly changing conditions. As in other areas of complex decision-making, for example, in the fields of investments, of production, and of the armed forces, computers most certainly have an important role to play in future exploration decision-making systems. However, we must first analyze our own business as closely as possible to find out what kind of information we need, i.e., why we recommend an exploration program as a good or a poor one. An important part of the debate about exploration is the case study. Case studies on exploration are few and most of those written are only about successful exploration programs. Where are the case studies of the failures and the not so successful programs? Every prospector knows that the majority of exploration projects fail. Consequently, the most important experience seems to be hidden in the failures.

Jan 1, 1979

By David Pentz, Paul Hodges

GENERAL INTRODUCTION The object of this paper is to discuss those aspects of open pit mine design which are affected by geotechnical factors. The temptation exists for some practitioners of geotechnical engineering to believe that this relatively new engineering discipline is the ‘be all and end all of mining.’ In the opinion of the authors, this is fallacious but, as our ability to put numbers to the behaviour of rocks and soils improves, it is clear that geotechnical engineering will become an integral and important part of designing and operationg mines success- fully. Open pit mines in the context of this paper also includes open cast mines, where the 'ore" is extracted and the waste material is immediately replaced or ' backfilled in the mined portion of the pit. Open pit mines operating today move from very small tonnages a day to in excess of 400,000 tons per day. Several mines are operating and are being designed to capital expenditure for such projects in some cases exceeds five hundred million dollars and in a few cases will exceed one billion dollars. The size of this investment means that financing will have to be provided from banks or joint partnerships. This financial environment means that planning will be carefully scrutinized by experienced representatives of financial institutions or other mining companies. All too often a project has been put in jeopardy because the personal desire of one or two men to make a project proceed has caused incomplete planning or perhaps in some instances deliberately leading observers 'down the garden path.’ In our opinion the day is rapidly arriving when the quality, logic, practicability and completeness of the planning will make the difference between securing financing or not and, in the cases of existing open pit mines, of the difference between survival and closure.

Jan 1, 1977

By H. Mercado G., J. R. Parga T

Mexico continues to be one of the main producers of silver, lead and zinc; although this leadership is ending because of the use of obsolete technologies, which is reflected in low recoveries of these processes. The country therefore requires to develop on new technologies in the field of nonferrous metallurgy, particularly be'cause it is the second most important source of foreign exchange. A novel method, presented in this paper, demostrates that refractory gold and silver can be extracted from a complex sulphide concentrate by a one stage pressure oxidation in an alkaline cyanide solution, this is achieved by simultaneous liberation_ and solubilization of the precious metals. Both gold and silver extractions are greater than 97%. Factors affecting recovery efficiency, such as: pH, lixiviation time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density, were investigated. A summary of actual plant operations is also be included.

Jan 1, 1993

Accidents that resulted in 16 deaths in three West Virginia coal mines, two in Kentucky and one in Utah have government and industry re-evaluating current safety regulations. Even though U.S. mines continue to improve on their safety records, the deaths reminded the industry and state and federal agencies that mining remains a dangerous business. Even so, data from the U.S. Mine Safety and Health Administration (MSHA) show that new technologies and a highly trained workforce has allowed the nation’s coal mines to increase production while providing safer workplaces. Since 1970, coal production at U.S. mines has increased by about 83 percent. During the same period, fatal injuries have fallen by 92 percent. And more than half of the U.S. coal mines operate each year without a lost-time injury. In 2005, there were 22 deaths in U.S. mines, a record low.

Jan 1, 2006

By Paul D. Tomlingson

Editor's note: This is the second of two articles on maintenance. Part one: "Downsizing maintenance to improve performance: Defining the downsizing task," appeared in the September issue of MINING ENGINEERING, pp. 1065-1066. Part one explained that downsizing must he an organizational change in which the mine moves to a more efficient, smaller maintenance organization. But the new, smaller organization must operate more productively. Determine initial reduction targets Reduce the workload - The initial reduction target can be determined by projecting manpower reduction as a result of discontinuing or deferring work. Start these reductions by not replacing personnel who retire or are disabled. Observe the right craft mix during this initial reduction. Improve productivity - Further reductions can come from better productivity. But achieving the higher productivity level will require a year or more. During this transition, the efficiencies of a well-defined program and a team organization must take hold.

Jan 1, 1994

By M. Carvalho, R. Bicallho, M. Queiroz, R. Gomide, V. Silva, R. Toubes

Since it is becoming increasingly important, from an environmental viewpoint, to minimize blast vibrations induced in urban dwellings and improve rock fragmentation in order to reduce costs with loading, transportation crushing and grinding, a cooperative research project was established between Companhia Vale do Rio Doce - CVRD and the Blasting Research Group in the Department of Mining Engineering at Escola de Minas - UFOP to investigate which elements interfere on ground vibration, air blast, flyrock and rock fragmentation related to rock blasting activities at Conceição Mine, located in Itabira city, state of Minas Gerais, Brazil. This research also involved development of a new explosives formulation in order to minimize the total blasting cost. This paper presents the general scheme of the research running from May 1995 to May 1997 and a summary of the results obtained in the field tests that were carried out in this mine.

Jan 1, 1998

By Christopher P. White, John R. Wagner

This paper will discuss the complex and difficult soil conditions encountered in the sinking of 15 shafts of 18m to 27m depth and the excavation and lining of 6700m of 2.74m dia. interceptor sewer on Staten Island, New York. The complex soil profile consists of dense glacial till and sand outwash strata overlying the much older cretaceous sand, silt and clay strata. The tunnel varies from 8m to 14m below the nearby sea level. A significant amount of boulders were anticipated in the till. therefore, a decision was made to excavate the tunnel with a digger shield installing bolted, gasketed concrete segments. The bid documents stated the soils were dewaterable. Several conditions occured in this complex soils matrix which required modifying the planned means and methods including the necessity to use compressed air. The conditions encountered and the equipment used will be described.

Jan 1, 1991

By Tim Cleary, Steve Skelhorn

The 9th Line / 16th Ave tunnels are part of a $700 million expansion of the York Durham Sewage System, north of Toronto. The 15 km of tunnels presented many challenges, including glacial and postglacial deposits, at depths up to 55 m. Due to high hydrostatic heads, the Owner specified EPB tunnelling, however, an alternate was proposed utilising rib and lagging tunnels, combined with a de-watering scheme. State of the art technology was utilised with a new Lovat TBM, incorporating PLC control, soft start water-cooled motors and a head designed to tackle the mixed ground expected. The 9th Line tunnels were completed in 2002. Subsequently the second section of tunnel along 16th Avenue has been awarded to the Joint Venture. This paper presents a case history of the soft ground tunnelling, including design elements, tunnel systems and TBM operations.

Jan 1, 2003

Jan 1, 1998

By A. Simon, J. Weyer, J. Brune, V. Zhiteneva

"Reiche Zeche is a lead-zinc-silver deposit in Freiberg, Germany, that was mined for over 800 years. Since 1969, Reiche Zeche has been a teaching and research mine with numerous adits for dewatering large amounts of inflowing water. Infrequent metal water quality monitoring in the 1980-1990s and flooding of the mine in 2002 led to a lack of relevant data. New measurements were taken at different level adits and ore veins for comparison to historical values, revealing pH levels as low as 1.95, conductivity as high as 22000 µS/cm, and an overall trend towards less acidic waters. INTRODUCTION Reiche Zeche is part of the Himmelfahrt Fundgrube, a former iron ore mine in Freiberg, Germany, in the Erzgebirge mining region of Saxony. The polymetallic sulfide ore found in Freiberg was mined from 1168 to 1969, and though it is no longer producing ore, Reiche Zeche remains as a teaching and research mine for the Technische Universität Bergakademie Freiberg. The most important ore minerals mined were sphalerite, galena, pyrite, chalcopyrite, and silver, and important gangue minerals include calcite, fluorite, barite, siderite, and quartz (Zänker et al 2002). Over one thousand ore loads were mined from this region during operation, which was ceased in 1969 after the lower part of the 700 meter depth was flooded, leaving only the top 200 meters under the surface open for research and teaching. Mined materials from this region can be separated into high grade ore and waste rock. High grade ore, composed of pyrite, sphalerite, galena, chalcopyrite, and arsenopyrite, was brought to surface for smelting during mine operation, and spaces were backfilled with waste rock, which is the primary site of sulfide oxidation and acid mine drainage (Haubrich and Tichomirowa 2002). The waste rock includes remnants of ore from ore loss, veins which were too small to mine, or ore minerals within host rock. Waste rock is primarily composed of biotite gneiss, with sulfides including jarosite, gypsum, minor anglesite, scorodite, and sulfur (Haubrich and Tichomirowa 2002). When weathered, the gneiss forms clay minerals such as illite and kaolinite (Haubrich and Tichomirowa 2002)."

Jan 1, 2016