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By John Wiebmer

Six industry trends will have significant effect on the way mining equipment is designed and supported in the years ahead: 1. MINING IS MIGRATING TO LESSER DEVELOPED PARTS OF THE WORLD The global recession of the early 1980's drove down commodity prices and intensified cost competition. This caused a fairly dramatic trend in mining away from higher cost operations in developed countries to richer, lower cost deposits in developing countries. Miners operating in lesser developed parts of the world will place higher value on rugged, durable designs that can live in more difficult and sometimes abusive conditions. They need engines and power train systems that are more tolerant of a wide variation in fuel quality and oil specifications. They'll require machines that are simpler to operate, simpler to maintain, simpler to troubleshoot and simpler to repair. And they'll require creative means of support in getting technical information, parts and components to remote operational sites. Mining equipment in the future will be more durable and simple than it is today, and product support will grow in importance as purchasing criterion. 2. THE MINING INDUSTRY IS CONSOLIDATING An intense amount of corporate acquisition and industry consolidation activity is occurring, to the point that today just 50 mining companies account for 55% of the western world non-fuel mineral production. Consolidation will continue, leading in the future to an industry structure weighted heavily toward a few key global mining houses.

Jan 1, 1993

By Mike D. Adams

Testwork was conducted on loaded carbon samples from a small gold mine in South Africa. It was shown that a 75% saving in reagent consumption in the Zadra elution circuit could be achieved by adopting a cyanide-free elution approach, i.e. by cutting back the NaCN level from 1 % to nil, and the NaOH level from 3% to 1 %. This process change was also shown to result in a 20% improvement in the elution kinetics. Furthermore, it was also shown that a 50% enhancement in elution rate over the current situation could be achieved by use of an eluant containing 0.5% NaOH and 0.15% NaCN, corresponding to an 84% saving in reagent consumption. A further improvement in elution kinetics was found to occur by increasing the NaCN level to 3%, but this would lead to a concomitant increase in reagent consumption, due to the decomposition of cyanide at high temperatures. The presence of base metals loaded onto the carbon was also found to have a significant effect on the elution. Copper tends to adsorb as Cu(CN)2- during the adsorption stage, and acid washing converts this species to CuCN. Copper in this form is not eluted during cyanide-free elution, whereas it is eluted during a conventional cyanide elution, consuming the initial cyanide in the process. The elution data was analysed and the fit to a simple model was verified.

Jan 1, 1995

By J. C. Norman

The boron review arrived too late to appear in the June issue. The United States was the world's second largest producer and the largest consumer of boron compounds during 1991. According to the US Bureau of Mines, boron mineral concentrate and chemical production in the US totaled about 1.1 Mt (1.2 million st), yielding about 608 kt (670,000 st) of BO, in 1991. Total estimated value was $440 million. That level of production was equal to 1990 revised production figures. Value was greater by $37 million, however, reflecting a strengthening of boron product prices. The US continued to supply essentially all its own boron while maintaining a strong position as a source to foreign markets of sodium borate products and boric acid. Domestic employment in the mining and beneficiation of boron products in 1991 remained at 1100 people, about the same level as in 1989. The Bureau of Mines estimated total world production of boron in 1991 - mineral concentrate and chemical - at about 2.9 Mt (3.2 million st). That corresponds to about 1.2 Mt (1.3 million st) of BO ,. World production in 1991 was about equal to revised 1990 levels. US production Mines and processing operations in southern California were the only domestic sources of boron mineral concentrates and chemicals in 1991. US producers, in order of quantity of production, were US Borax and Chemical Corp., North American Chemical Co., and American Borate Co.

Jan 1, 1992

By Krishniah N. Murthy, James E. Monsees

BACKGROUND The development of public transportation in the Los Angeles Metropolitan area is, as in other cities, closely tied to the development of the area because of increases in population and commercial and industrial activity. Local transportation first appeared in the area in the 1870s when the population was fewer than 10,000 residents. Around 1910, after many consolidations of competitive interests, two large railway companies were formed: The Los Angeles Railway, which provided urban transportation in the Los Angeles City area, and the Pacific Electric Railway, which primarily provided suburban and interurban transportation. These two entities continued with their operations until after World War II, when the ownership passed on to the Los Angeles Transit Lines and the Metropolitan Coach Lines, respectively. By then the railroads needed new equipment, track rehabilitation, and, of course, more money-paying patrons. Lack of grade separation of railway facilities from other traffic increased commute times and encouraged travel by private automobiles. The romantic era of hopping on a Pacific Electric Company "Big Red Car" was coming to an end. As early as 1917, in fact, bus lines were substituted for unprofitable rail service. The Los Angeles Metropolitan Transit Authority (LMTA) was established in 1951 by the California Legislature to study and plan for improvements in the public transportation facilities in the Los Angeles area. In March of 1958 the Los Angeles Metropolitan Transit Authority took over the operation of the two lines.

Jan 1, 1989

In 1990, US mine production of barite increased 54.1 %. Barite consumption, sold or used by grinding plants, increased by 27.6%. Imports were about the same as 1989. World mine production in¬creased 12.3%, according to the US Bureau of Mines. The value of domestically produced barite, fob mine, decreased 12.7%, according to the Bureau. The declared value, cif US port, of all imported crude barite during the year 1990 increased from $40.27/t ($36.54 per st) in 1989 to $40.61/t ($36.84 per st). Nevada continued to be the leading producer of barite with 82% of the total, followed by Georgia and Missouri. It is estimated that 750/c, of the domestically mined barite was used as a weighting agent in drilling fluids. The remaining 25% was used in barium chemicals, glass or as a filler. Most of the production from Missouri, Georgia and Tennessee was used in the non-oilfield sector. Of the total barite used by grinding plants and chemical manufacturers, it is estimated that 90% was used in drilling fluids and 10% in the non-oilfield sector. This includes barium chemicals and fillers in paper, plastics, and glass. Tonnage consumed in the drilling fluids market increased due to the higher average rig count during 1990. The average number of rotary rigs operating, (1010), was 16.2% more than the 1989 average of 869 in the US.

Jan 1, 1991

To generate a most profitable ultimate pit limit is generally the first step in mine design. This paper presents a new graph theory oriented, optimum ultimate pit limit design algorithm which will maximize the total undiscounted net profit. This algorithm performs much better than the well known Lerchs-Grossmann algorithm, in terms of the reduction in computation time and computer memory requirements. This algorithm operates on many directed trees in a graph, where each vertex in a tree represents a block in the mine model. The formation of each directed tree is based more on the ore-waste support concept than the geometry constraints alone. The general procedures of the algorithm, programming considerations and two case study results are discussed in the paper.

Jan 1, 1990

By S. W. Arambur

INTRODUCTION "Mujeres Roca" is a program developed by OMA in association with the Chamber of Commerce Canada Peru inspired in “Women who Rock”, a Canadian initiative to promote a greater participation of women in the mining industry. The program includes a coaching workshop called “Kallpa Warmi”, that means “Woman Strength”, to reinforce basic skills and values and 8 mentoring sessions with top executives of the mining industry who share their experiences and knowledge with a group of 10 selected young professional women from around the country. HISTORY OMA is a nonprofit association founded in 2014 dedicated to contributing to the education of low-income university students with high academic performance in careers related to mining and earth sciences. Our mission is to empower the future professionals by strengthening their soft skills and enhancing their capacity to become leaders and agents of change in their own regions. The Chamber of Commerce Canada Peru has a long-standing commitment to gender equality and promotes women participation in male dominated industries. As it is well known, the mining sector is and has always been key to Peru’s economy, representing about 10% of the country’s GDP. Thus, mining can contribute significantly to our economic development and we believe that women can make a positive difference. A study prepared by PwC and "Women in Mining” provided indicators on the advantages that mining companies have when including women in their executive’s positions. These indicators sustain that when a mining company includes women in its management staff, its net profit increases by 6%. This information clearly shows that women participation is not only a matter of human rights and gender equality, but of productivity and profitability. Nevertheless, the mining sector has the fewer number of women on boards of any industry group in the world. Having this in mind, OMA decided to expand its activities and create together with the Chamber of Commerce Canada Peru, the program “Mujeres Roca”, in order to inspire and attract young women to the mining sector, a traditionally masculine industry. The program also aims to encourage mining companies to more actively recruit and keep women in their boards. The program was launched in 2016 within the framework of EXPOMINA PERU, the largest international mining exhibition that take place in Lima every two years.

Jan 1, 2019

By James S. Browning

The principal uses of fine ground mica are as filler in wallboard joint cement, as a filler and surface coating for roofing, as an ingredient in paints, and in oil well drilling mud. The mineral has other uses in the manufacture of rubber, wallpaper, plastics, welding rods, electric insulation, house insulation, and textiles, and as an annealing agent in metal treatment. In recent years, more than 999 percent of the domestic mica produced has been scrap and flake mica (mica which does not meet specifications for sheet mica and is used for producing fine ground mica). There has been a continued increase in mica production for, several years, the 1963 production of scrap and flake mica totaling 117,251 tons.

Jan 1, 1966

By Gregory D. Savage, Bruce M. Everett

Introduction The growing role of Colombia as a major supplier of internationally traded steam coal has been widely discussed in the industry. Although Colombian coal has been produced and exported in small quantities for a number of years, the country's position as a major coal exporter began in earnest in 1985 with the first commercial exports from the Cerrejon North Block Project. The mine is located on the Guajira peninsula in northeast Colombia, about 145 km (90 miles) from the coast (Fig. 1). In addition to the mine itself, the project involves construction of a dedicated railroad and port. This forms a modern, efficient, and integrated system. The project is embodied in a 50-50 association contract between International Colombia Resources (Intercor), a wholly-owned subsidiary of Exxon, and Carbocol, the Colombian state coal company. Intercor and Carbocol share investment and operating expenses equally. Intercor has the additional responsibility of managing operations on behalf of the partners. Each partner is entitled to 50% of the coal produced, and each markets its share separately. The project is a multi-seam, truck and shovel operation, based on large reserves (2 to 3 Gt or 2.2 to 3.3 billion st) of high quality bituminous coal. Exports began in the first quarter of 1985, at modest levels through what is called Early Coal Facilities. The permanent coal handling system began operation in February 1986. Production will increase rapidly in each of the next few years, reaching the design capacity of 15 Mt/a (16.5 million stpy) in 1989. Based on available resources, however, the resource will support expansion, and continued growth in production into the 1990s is feasible. Importance of transportation The success of a new coal export venture, such as Cerrejon, depends heavily on efficient transportation. In the international coal industry, overland and ocean transport can in some cases account for 40% to 50% of the final value of the product. Many coals, such as western US subbituminous coals, cannot reach export markets at all because of their low heat content and great distance from export markets. By the same token, low-grade resources are often commercially attractive for local markets even in the face of competition with much higher quality coals from distant sources. Figure 2 shows the growth in steam coal imports into Europe, the largest trading market. Through

Jan 6, 1986

By Bezalel C. Haimson

Long before excavation begins, the in situ stresses in the horizon of planned underground chambers can be measured by employing the hydrofracturing technique in existing exploratory holes. Such measurements produce the stress magnitudes and directions required for the rational design of rock structures. Two recent case histories are cited in which preexcavation stress measurements for the design of underground powerhouses proved very beneficial in the orientation of the chambers and the estimation of the stability and required support. A third stress measurement case is related to the preexcavation design of tunnels that will house doughnut-shaped superconductive magnets for the storage of electric energy. In all cases, expensive later modifications were probably prevented by measuring stresses early in the design stage.

Jan 1, 1976

By Jan Wolski, Jack Barry

Ventilation ductlines with a single fan or with a series of fans are analyzed. The duct friction loss factors are discussed. Numerical solutions, presented in the paper, applies to any fan number and locations along a duct line. The findings are compared with formulas available in the technical literature. Values of the air leakage factors are presented in the SI, technical metric, and US unit systems. A method is shown of how to determine the leak- age factor for a given ductline. Optimum solutions for the sample duct lines with two and five fans in series are discussed and presented in a graphical form. Performance of fans in series is discussed in conjunction with both friction pressure loss and leak- age.

Jan 1, 1997

By Yoshihiro Kawarabata

INTRODUCTION The shield-driven method in Japan has been adopted widely in soft ground tunneling, namely, subway, water supply, sewer and utility tunnels, and recently this is an indispensable method in urban area. Since this method was started to adopt on a full scale from the beginning of 1960, construction achievements in length were about 830 km for 15 years until 1974 (1). According to the recent informations of the Japan Tunneling Association, the achievement in length under construction as of December, 1977, was about 350 km (2) and the extention of increase in shield-driven method can be guessed (Tab. 1). Tab. 1 - Achievement in Length by Shield-driven Method (As of December, 1977, Unit: m) (---): Achievement by Okumura Corporation [ ]

Jan 1, 1979

By Y. C. Kim

To generate a most profitable, ultimate pit limit is generally the first step in mine design. This paper presents a new graph theory oriented, optimum ultimate pit limit design algorithm which will maximize the total undiscounted net profit. This algorithm performs much better than the well known Lerchs-Grossmann algorithm, in terms of the reduction in computation time and computer memory requirements. This algorithm operates on many directed trees in a graph, where each vertex in a tree represents a block in the mine model. The formation of each directed tree is based more on the ore-waste support concept than the geometry constraints alone. The general procedures of the algorithm, programming considerations and two case study results are discussed in the paper.

Jan 1, 1992

By Carl E. Brechtel, Edward D. Thimons

Providing adequate airflow to effectively dilute and remove diesel pollutants in large mine working headings is a little researched area. A simulated diesel mucking operation was carried out in the Exxon Colony Pilot Mine in Colorado to establish expected levels of diesel pollutants in dead-ended working headings. This heading was nominally 15.3 m (50-ft) wide by 9.2 m (30-ft) high. Two face ventilation systems were tested using sulfur hexafluoride tracer gas to represent the diesel pollutants. The results of these tests showed that conventional face ventilation systems operating at high flow rates could adequately ventilate diesel equipment in the 447-522 kw (600-700 hp) range, even in a dead heading 91.4 m (300 ft) in length.

Jan 1, 1987

By Dennis S. Kostick

Sodium is a silver-colored metal that is so unstable that it reacts violently in the presence of water, and chlorine is a greenish-colored gas that is dangerous and lethal. Yet the combination of these two elements forms sodium chloride, commonly known as salt, which is a white-colored compound essential to life itself. Salt is perhaps the only mineral in the world that is used virtually by every human being in every country. Although its importance has diminished over time, salt has had a profound influence on history. Sources of salt have determined the location of cities, such as Salzburg, Austria, Salzgitter, Germany, Salt Lake City, UT, and Saltville, VA. Populations have migrated in search of salt, and wars have been fought to obtain or to protect it. Although there is no written record of when prehistoric man first discovered salt, he probably instantly appreciated its unique and distinctive taste and sought more of it. He noticed animals were attracted to salt springs and salt licks, where they satisfied their innate cravings. Man used this knowledge to hunt for food; where he found the salt, he would find the animals. Because prehistoric man was not aware of his physiologic need for salt, he automatically received his salt requirements from the meat of the animals he ate. A Mesopotamian tale tells of a wounded pig that ran into the ocean and drowned. After being recovered from the ocean, where it was saturated in the salt brine, the pork was found to taste better than unsalted meat. It was not until man graduated from a nomadic to an agricultural society when he introduced vegetables and cereals into his diet that he realized he needed additional supplements of salt. The Sumerians ate salted meat and used salt to preserve food about 3500 BC. In approximately 1000 BC, the Trojans learned to use salt for preserving fish. The maritime civilizations, such as that of the Phoenicians, engaged in an extensive salt trade throughout the Mediterranean. Many superstitions, customs, and traditions surround the religious, social, economic, and political aspects of civilization. Although some commodities have provided the basis of some ageless metaphors and cliches (i.e., heart of gold, strong as steel, etc.), none are more commonly used than those pertaining to salt. Being "the salt of the earth" referred to a person's worthiness, as referenced in Matthew 5:13 of the Bible. Someone "not worth his salt" reportedly was used in ancient Greece in bartering salt for slaves. When a laborer was worth his salt, he was paid a salary (sal is Latin for salt), a term still in use today that dates back to Roman times when part of a soldier's pay was salt rations. Fearing those around him, the Roman leader Pompey was known to add a grain of salt to his drinks as a supposed antidote to poison. Hence, "taking it with a grain of salt'' is to regard something with suspicion. The earliest known record of salt production was in China about 2000 BC when Emperor Yu decreed that salt had to be supplied to the court as a tribute. Because salt was a commodity that had universal demand, governments often intervened to control salt production and distribution to generate revenue for major national projects. State-run salt monopolies were common in history, such as in Rome about 506 BC. Revenue was also derived from taxes levied on salt sales. The word gabelle refers to the direct salt tax used in France. This tax was so despised that it was a major cause of the French Revolution. Although the tax was repealed in 1790, it was reinstated in 1805 to raise revenue for war. France continued to used the gabelle until 1945. Salt making was an important economic activity in many areas of the world. Archaeological evidence indicates that salt was quarried from hills near the Dead Sea before the Bronze Age. At Hallstatt in the eastern Alps of Austria, rock salt was mined as early as 1400 BC. Solar salt was being produced in the northern Yucatan peninsula by the Mayan civilization from about 50 BC to AD 300. Other than the prehistoric use of salt in the southwestern part of the United States by the Native Americans, the first production of salt by American colonists began in June 1614 on Smith's Island, VA, seven years after the founding of the Jamestown colony. The short-lived activity was in response to the high price of salt being charged by ship's captains who brought salt over as ballast from England. Although Nathaniel Loomis is credited with starting the first commercial inland salt production in the United States at Onondaga Lake in New York in 1790, salt had been made by individuals for private use years earlier. Indians had long known of the salt springs in the Kanawha Valley of Virginia (now known as West Virginia). In 1755, Mary Ingles, a white settler, was kidnapped by Indians and was forced to make salt from the saline springs. After her escape, she told other settlers how to make salt. At Saltville, VA, Arthur Campbell began making salt in 1782 by boiling brine obtained from salt springs. In 1799, William King sank a shaft about 3 m in diameter down about 61 m to the underlying Saltville salt deposits. The shaft flooded before he could extract any rock salt; however, King has the distinction of digging the shaft of the first salt mine in the United States. Fig. 1 shows the King site as it appears today in Saltville, VA. Production of brine from the shaft continued until 1892. Settlers moved into the Kanawha Valley in 1785, but it wasn't until 1806 that Elisha Brooks established the first commercial salt works in Kanawha.

Jan 1, 1994

By Richard L. Nielsen

Early Models In 1906, Daniel Jackling demonstrated that relatively low-grade disseminated copper deposits could be mined profitably using mass mining technology. The ensuing years saw a gradual increase in activity aimed at defining ore targets for large reserves of disseminated supergene enriched copper ores. Prominent organizations, such as Calumet and Hecla, Phelps Dodge, and Asarco, established teams of geologists. They focused on interpreting oxidized and leached outcrops over supergene chalcocite ore bodies. Techniques to evaluate oxidized cappings and predict the presence of underlying supergene chalcocite enrichment ores were developed and put to practical use by the late 1920s and early 1930s (Locke, 1926; Blanchard 1939, 1968). Oxidized capping evaluation centered on recognizing oxidation products derived from the various sulfide minerals found in disseminated deposits. Chalcopyrite, for example, oxidizes to a characteristic reddish pitch limonite that exhibits characteristic boxworks. Chalcocite is recognized by earthy, powdery, indigenous, hematite-rich limonite. Pyrite weathers to characteristic cavities and yellowish jarositic limonites. Evaluation of cappings is a systematic effort of noting and estimating the preoxidation sulfide mineral content and copper grade in an oxidized outcrop using mineral composition and morphology of oxidation products. Several complications were noted early in this technology's development. For example, the associated pyrite content of protore greatly influences mobility of copper and iron during oxidation. High-pyrite disseminated sulfide assemblages, upon oxidation, mobilize iron as well as copper. This results in oxidized rock with many leached cavities, poorly developed boxworks, and poorly developed indigenous limonites. This effect was noted and used in a general way to identify possible development of supergene chalcocite. Indeed, strongly leached outcrops could be present over enriched ore. A second complication is the manner in which associated gangue minerals influence the products of sulfide oxidation. Reactive gangue minerals, such as carbonates, neutralize acids formed by sulfide oxidation. Thus, copper cannot be moved from oxidized outcrops. Relatively nonreactive gangue, such as quartz-sericite-altered schist or porphyry, neutralizes supergene acid very slowly. This allows copper to move out of the oxidized outcrop. Recognizing these features was closely allied to an early understanding of the processes involved in oxidation supergene enrichment of disseminated ores. Field observations and mineralogic mapping of oxidized cappings were important in discovering many important porphyry copper ore bodies during the 1920s. These include Silver Bell, Miami-Inspiration, and Morenci in Arizona; Tyrone, NM; and Ely, NV. Capping interpretation like-wise led to discoveries at Mineral Park and Esperanza in Arizona during the exploration surge that accompanied high copper prices in the 1950s. In the 1960s, Kennecott research geologists refined and quantified some aspects of oxide capping appraisal (Anderson, 1982). The ratio of jarosite plus hematite to the total limonite assemblage was shown to be proportional to amount of copper leached from the oxidized outcrop. Thus, if the limonite assemblege in an oxidized capping consists of 40% goethite, 20% jarosite, and 40% hematite, 60% of the original copper is leached. The amount of copper remaining in the capping, together with the limonite mineralogy, can then be used to estimate original copper grade in the outcrop, amount of leaching, and chalcocite enrichment grade (in feet/% copper) in the underlying supergene chalcocite zone (Anderson, 1982). Evaluation of oxidized cappings and prediction of chalcocite blanket ore targets were successfully used in the western US and South America through the 1950s. Discovery of new porphyry copper provinces in other regions during the 1950s and 1960s, however, underscored some limitations of capping evaluation technology. Porphyry copper systems in Australia generally oxidize and weather to hematitic cappings. Presumably, the semiarid monsoon environment and the long time that the sulfide systems have been exposed to oxidation on that continent lead to development of relatively stable hematite. It is now recognized that jarosite and goethite persist metastably in the limonite assemblage in all areas once sulfide oxidation is complete and acid generation ceases (Brown, 1971). The assemblage eventually converts to hematite. But, climatic conditions in arid southwest US allows metastable limonites to persist for a long time, thus providing information on former sulfide assemblages. Another problem occurs when applying capping evaluation techniques in extremely humid re-

Jan 12, 1984

By R. V. Johnson

The review of mineral activities in Minnesota arrived too late to appear in the May issue. Minnesota continued to lead the nation in iron ore production in 1989 with more than 70% of the market. At no time in the past 50 years has Minnesota's iron ore market share fallen below 50%. 1989 production was provided by six iron ore pellet operations and one high-grade iron ore mine. Most American steel companies are represented in these operations through whole or partial ownerships in Minntac (USS), Minorca (Inland), Eveleth Mines (Armco and Rouge), Hibbing Taconite (Bethlehem), and LTV Steel and National Steel Pellet. A seventh iron ore pellet producer started up in 1989 when Cyprus Minerals acquired the assets of bankrupt Reserve Mining Co. This operation, with first production scheduled for 1990, will be the only non-steel company captive operation in Minnesota. Encouraging minerals development In an attempt to stimulate further and additional mineral development in Minnesota, the state's legislature established a Minerals Coordinating Committee (MCC). This committee is comprised of the Department of Natural Resources-Division of Minerals, the Minnesota Geological Survey, the Natural Resources Research Institute, and the Mineral Resources Research Center. The Committee has sponsored and coordinated various projects. Among these MCC-sponsored projects are glacial drift geochemistry with an emphasis on gold and indicator minerals, accelerated geologic mapping, continued aeromagnetic surveying of Minnesota, greenstone geochemistry, structure and stratigraphy of the Duluth complex, and drill core and exploration data acquisition from past exploration programs. Regarding drill core, the Division of Natural Resources completed construction of its third core library building in Hibbing. These data and core are available for public examination.

Jan 1, 1990

Overview In 1992, US coal supply and demand were shaped more by weather conditions and the export market than by the economic recovery. Preliminary data compiled by the Energy Information Administration (EIA) (Table I) show that coal production declined slightly to 902 Mt (994 million st). Consumption, though, rose by about 1 % to 811 Mt (894 million st), trailing the 2.1 %growth in Gross Domestic Product. Contributing to the decrease were a sizable drop in coal exports and some coal stock withdrawals. Consumption increased largely because electric utilities turned to coal to offset a shortfall in hydroelectric generation caused by a drought in the Northwest. Apart from this, the demand for coal-fired generation was dampened by a mild winter in the northwestern and northcentral United States, and a cool summer in the central and eastern parts of the Nation. Coal use by other consumers was about the same as in 1991. The average delivered prices of coal to all consuming sectors decreased slightly in 1992, reflecting soft coal markets (Fig. 1). US coal exporters experienced a set-back in 1992 mostly because of losses in the European market. Total coal exports fell by 6% to 93 Mt (103 million st), the first decline since 1987. Coal stockpiles at the end of 1992 were about 1.8 Mt (2 million st) below 1991, despite stock buildups by some electric utilities in the East. Stocks were built up as a hedge against possible coal miners' strikes after the Feb. 1, 1993, expiration of the contract between the United Mine Workers of America and the Bituminous Coal Operators' Association.

Jan 1, 1993

By Charles L. Kimbell

In 1989, worldwide total mineral industry activity registered advances from 1988. The advances may not have been as noteworthy as in 1988, but they can be regarded as a worthy theme for this article. The momentous political events throughout the centrally planned economy world had only a modest impact on actual 1989 industry performance. But these events have such potential for worldwide changes in economic activity in future years that they dwarf the actual happenings of 1989 in the minerals industry. Perhaps most significant factor here is the rapidity with which these changes have occurred. The end of World War II saw the almost immediate division of the world into major economic blocs. Since then, mineral industry activities and other industrial operations have been governed, to a considerable extent, by this partitioning. The developed market economy nations have operated as a group, the centrally planned economy states as another group. And these two groups essentially have vied for recognition in mineral industry operations in the developing economy states of Asia, Africa, and Latin America. The boundaries of these country blocs were fixed in the late 1940s and early 1950s. They were not markedly altered in the ensuing 40 years. We have seen the establishment of the Organization of Petroleum Exporting Countries, the continued Arab-Israeli confrontations in the Near East, the upheavals surrounding the rise of Moslem Fundamentalism in Iran, and the establishment of Soviet-oriented governments in Cuba and Nicaragua. These events have had notable effects on the world economy. But they have done little to change the pattern of market economy states functioning as a competitive bloc with the centrally-planned economy countries.

Jan 1, 1990

By Alastair R. Biggart

ABOUT BENTONITE TUNNELLING Much has been written and many learned papers given on this subject whose generic term is Slurry Tunnelling. This paper is about the particular form of slurry tunnelling known as the Bentonite Tunnelling System. This method. of tunnelling was invented by J.V. Bartlett of consulting engineers, Mott Hay and Anderson in 1964. The general principles are incorporated in British Patent No. 1083322. It was not until the early 1970's that serious experimental work was started to prove the technical feasibility of the process. In the U.K. in 1971 Edmund Nuttall Limited started on an experimental length of 3.8m diameter tunnel at New Cross in London. In Germany at about the same time Wayss and Freytag were starting on a 3.7m diameter collector sewer tunnel in Hamburg. In Japan early slurry tunnelling work was carried out in the 1960's. In the early 1970's a large number of slurry tunnels of various diameters were carried out in that country. This paper is being presented at a time when this system of tunnelling has become an accepted method throughout the developed world. As a result of the work carried out so far there is now a large amount of data existing regarding the effects on the ground in the immediate area of the tunnel, settlement at the surface and the ability of the system to cope with ground varying from clays to coarse gravels and containing large erratics such as granite boulders. The decade of the 1970's has therefore seen a very rapid pace

Jan 1, 1979