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By Bo Kyung Sim, Dae Young Kim, Jae Won Lee, Ebrahim Farrokh

"The contract C931 of the downtown line 3 (DTL3) mass rapid transit system of Singapore includes half a kilometer twin tunnels running between Mattar and Macpherson stations. An EPB TBM of 6.6 m diameter was used to excavate both of these tunnels. The tunnels pass predominantly through a very stiff silty/clayey fine to coarse sand from the Old Alluvium Formation. In this paper, TBM selection procedure, TBM performance evaluation, and some of the tunneling operation challenges with the TBM in the Old Alluvium Formation are discussed. In this regard, soil conditioning trial tests were performed to resolve the clogging issue and low TBM performance. Thorough TBM operational data analysis was performed to detect high soil abrasivity, backfill grout leakage, and foam nozzle clogging. The results of some of the applied modifications are also discussed to show their effects on the TBM performance improvement. Finally, some of the challenging TBM design specifications are also discussed. INTRODUCTION Tunneling and underground construction in Singapore has been increased in the last 30 years due to the demand for public transportation systems and the limited space above the ground for the infrastructure development. Downtown Line Stage 3 (DTL3) Mass Rapid Transit (MRT) system has 21 km total route length and consists of 16 stations. DTL3 Contract C931 runs between Mattar station and MacPherson station. The construction works in this contract include twin bored tunnels of 6.6 m diameter and 450 m length and a TBM launch shaft of nearly 30 m depth. The tunnels run in urban area below Kallang Paya Lebar Expressway tunnel (KPE), Kallang River Canal, and Circuit Link. Figure 1 shows the alignment of the tunnels in between two subway stations. The tunnels were excavated by an earth pressure balance (EPB) tunnel boring machine (TBM) through the Old Alluvium (OA) formation, a challenging geological formation in the sense of its abrasivity and stiffness. The Old Alluvium Formation mostly includes stiff to very stiff clayey and silty sand. The soil is un-weathered cemented to semi-cemented dense, mainly with a low permeability coefficient of 10-7 m/s and high SPT values (almost 100). The soil is classified as “very high abrasive” according to NTNU SAT test classification (SAT value of 15 to 42). The construction of the first tunnel drive was slowed down due to a number of factors related to soil conditioning and TBM operation. In this regard, a thorough analysis of the TBM operational parameters from the excavated sections was performed to identify the problems in time to prevent unwanted construction delays in the subsequent sections. In the following sections, a brief overview of the criteria used for TBM selection is presented at first. Then, the results from the analyses and tests performed to assess soil conditioning, grout leakage, and soil abrasion are presented. The last section discusses some of the tunneling design features that challenged the TBM operation in this project."

Jan 1, 2016

By R. Casagrande, L. R. Moore, J. Sessoms, P. Macy

"A South American nickel mine has been producing a nickel concentrate that also contains copper and iron (15 percent nickel, 5 percent copper, 28 percent iron) for the end use of stainless steel production. A critical specification for the quality of the steel is the iron to magnesium oxide ratio (Fe:MgO), with a ratio of below 3.5:1 having a substantial impact on the nickel value. This nickel concentrate producer historically mined the sulfur-rich mineral pyroxenite but had been forced to move to a magnesium oxide/silicate (MgO/SiO4)-rich mineral harzburgite, resulting in nickel recovery being reduced to around 50 percent to maintain the required Fe:MgO ratio. In this study, ore mineralogy, water chemistry and the chemistries associated with the flotation process were evaluated in an effort to increase nickel recovery while maintaining the Fe:MgO ratio according to specification. New chemistry was introduced with the specific goal of complexing with the MgO and retarding its interaction with the bubble flow in the flotation process.IntroductionGlobal nickel production in 2011 totalled to 1,770,000 tons, according to the Raw Materials Group (2013). From 1950 to 2005 there was an aggregate 4.4 percent increase in nickel production, with a market-value high of $1,000/ton nickel reached in 1998 (Mudd, 2010). Approximately 65 percent of nickel production is consumed by the stainless steel industry, with 12 percent of the remainder used in super alloys or nonferrous alloys. Nickel imparts corrosion resistance, temperature resistance and other benefits to its alloys (Table 1) (Oberg, 1996; Cáceres, 2003). The dominant types of nickel-bearing ores are classified as either laterites (limonite: nickel-iron oxide; and garnierite: nickel hydrosilicate) or magmatic sulfide deposits (pentlandite: iron-nickel sulfide) (U.S. Geological Survey, 2013a, 2013b). In 2012, about 40 percent of the nickel ore mined was sulfidic-type ores and about 60 percent was laterite. The processing of laterite ore is expected to continue to increase as the availability of sulfidic ores continues to decline."

Jan 1, 2015

By David Butts

Completion of a railroad to the high Tibetan Plateau in Central China has now made it economical to exploit its mineral reserves. Lead and zinc mines are now being established. A potash plant to produce 40,000 tons per year KC1 is now in operation. Plans to produce 200,000 tons per year by 1987 are being implemented. Pilot drilling for oil and natural gas have proved up reserves. Slaughter houses are being constructed to ship yak, mutton and beef from the endless grasslands on the plateau. Research Centers in Xining and Golmud have been completed for the sole purpose of increasing technology and exploitation of the Tsaidam Basin and surrounding area.

Jan 1, 1984

By T. R. Ellis

Many appraisers/valuers believe that the only valuation method available within the Cost Approach category for Real Property appraisal is the depreciated replacement cost method. Some valuation and financial reporting standards setters also believe the same. This paper introduces the minerals appraiser to a number of useful methods for mineral property appraisal that are based primarily on the principle of contribution to value, the predominant economic principle in the cost approach. Most of these cost approach methods discussed are primarily for use in valuation of exploration tracts and resource properties that have no defined reserves. However, the powerful rural cost method can be used to calculate the contribution of categories of resources, reserves, and other property components to the value of a mineral property. This method can be applied to mineral properties at all stages of development, including producing properties.

Jan 1, 2011

By Steve Karl

Introduction US steel production dropped 5% in 1985 to 79 Mt (87 million st). US operators are producing at only about 65% of capacity. More than 600 steelmaking facilities have closed in just 10 years. And McDonalds Corp. now employs more people than the entire US steel industry's 200,000. Not gloomy enough? Well, the North American iron ore industry can expect more plant closures and capacity reductions in the coming years. And don't count on the Federal government's voluntary restraint agreements with foreign steel producers to bail out the industry. In 1985, the first full year of the restraint agreements program, steel imports were more than 25% of domestic consumption, well above the 18.5% target. That's the grim truth, according to M. A. Hanna's Robert F. Anderson. Hanna's chairman was speaking to a group of iron ore, taconite, and steel industry executives at the Minnesota Section AIME meeting in Duluth in January. Despite those depressing facts, Anderson said he believes the domestic iron ore and steel industries can survive, although they will both be shadows of their former selves. But, he is giving them five years to make the necessary adjustments or both will die. Major steel producers during the last four years have added about $7 billion in losses to their books, he said. In Minnesota's Iron Range, employment in iron ore and taconite has gone from 14,000 10 years ago to less than half that today. Anderson explained that steel producers have more capacity today that more than meets their demand for iron ore. This places great pressure on iron ore producers to restructure to survive. Hanna, for example, has been forced to close or divest its iron ore interests in Missouri, Michigan, Canada, and Minnesota since 1980. The latest casualty was the company's Butler taconite project in Minnesota. "In just five years we've reduced ownership of active pellet capacity by 80%," he said. Technological ironies Improved technology is one cause of the industry's woes, Anderson said. While these improvements are welcome in terms of remaining competitive, the irony is that some of these technological improvements are coming at the expense of the iron and steel industries. There is a growing demand for lighter and less expensive substitutes for steel. Automobiles contain about 318 kg (700 lbs) less steel than they did 10 years ago. And, Anderson said Ford Motor Co. has indicated it plans to reduce steel usage an average of 50 kg (112 lbs) per car in the next few years. One leading steel analyst has predicted that steel usage in cars will fall another 40% in the coming years. Improved steelmaking technology has also decreased raw steel production. Continuous casting is more efficient than traditional forms of steelmaking, Anderson said. Continuous casting accounted for about 43% of steel production in the US last year, compared to 9% a decade earlier. And, Japan and Korea are producing more

Jan 3, 1986

By T. Yukimasa

Hachinohe smelter, a zinc-lead blast furnace complex with the annual capacity of zinc plus lead of 100,000 tons, had originally treated normal zinc and lead sulfide concentrates. However, it is currently handling a great variety of raw feeds ranging from complex sulfides to oxidic recycled materials in view of resource economy, most of which are unsuitable for zinc electrolysis. This paper reports on some significant efforts recently carried out on improving sintering operation, i.e., the increasing use of secondaries against harmful ingredients like halogens, and the substantial reduction in energy use as the results of various modifications and improvements.

Jan 1, 1982

By John C. Nixon

In 1959, The Australasian Institute of Mining and Metallurgy (Aus. I.M.M.) was asked by the Federal Government of Australia and the State Government of South Australia to join in the formation and management of a new contract research organization which was subsequently named The Australian Mineral Development Laboratories (Arndel) ? This body was formerly the Research and Development Branch of the South Australian Department of Mines which had been set up to develop the Radium Hill uranium deposit. It had then gone into contract R&D and the State felt that it would be more appropriate for the Branch to become a separate national organization. The Aus. I.M.M. decided that a professional institute could not participate directly in Arndel and, as there was no other suitable industry group to do so, it formed the. Australian Mineral Industries Research Association Limited (AMIRA). AMIRA held its first Annual General Meeting in September 1959 when the first Council was elected and the Memorandum and Articles of Association were adopted. The initial task of AMIRA was to raise guarantees of work or cash from its members to underwrite Arndel for the first five years of operation. The Federal and State Governments also provided guarantees and Arndel commenced operations in January 1960.

Jan 1, 1977

By Joseph A. Dos Santos

"The subject of this writing was first published in 1998 with the emphasis on the hardware cost comparison. Other costs, such as the required land area and spatial volume, were mentioned but not emphasized, as these were not deemed as important for new projects where the space was appropriated as required. During the last decade, these other costs have proven to be more than equal in importance. These costs are emphasized here through specific accounts of actual highangle conveyor installations that demonstrate the importance and the high-angle advantage An update on the progress in sandwich belt highangleconveyor technology is also provided.Origin and progress in sandwich belt conveyorsCover belts of the 1950s. Large volume, highangle conveying by “conveyors with cover belt, dates back to the early 1950s, when such systems were employed at the bucket wheel excavator boom conveyor in German lignite mines to increase the depth of cut without increasing the boom length. Various systems were developed, patented and built. These systems were not a lasting success for various reasons, which are noted by Rasper[1]. In his 1958 “Review of Cover Belt Systems,” Rasper summarizes the characteristics which are worth pursing and those that should be abandoned. The former are akin to good conveyor engineering. The sandwich belt conveyor model. The first sandwich belt conveyor model allowed calculation of the required hugging pressure to develop the bulk material’s internal friction and preclude material slideback. A modern, accurate version of the sandwich belt conveyor model is presented in Fig. 1. This model depicts accurately a derating of the material cross-section allowing an ample belt edge distance that can tolerate normal belt misalignment without material spillage. The calculations must thus recognize that only part of the hugging pressure is imparted onto the material with the remainder transferred belt edge to belt edge affecting a material seal. Mathematical development of the sandwich belt model is covered by Dos Santos and Frizzell in their 1983 article, “Evolution of Sandwich Belt High Angle Conveyors.”"

Sep 1, 2016

By John L. Stafford

The ROEMMC combustion system was originally conceived as a means of utilizing solid fuels that would otherwise have been wastes requiring disposal and convert these fuels into useful energy sources. This concept follows as an extension of the application of residual waste incineration with energy recovery practiced in the lumber, manufactured board, sugar cane, and other industries. The incineration of these wastes in the furnaces of steam generating equipment is thoroughly described (1, 2, 3, 4, 5, 6, 7). The fundamental principle of the ROEMMC system is temperature control which makes possible the maintenance of the non-combustible fraction of these solid fuels in a dry solid state and their separation from the gaseous products of combustion. This philosophy of ash removal and the "slagging" philosophy are compared. The ROEMMC equipment function and applications are described.

Jan 1, 1978

The most complete mining show ever held in the United States and the largest exposition of its kind to be held anywhere in the world in 1988. That's how the American Mining Congress is billing its "MINExpo International '88," to be held April 24-28 at Chicago's McCormick Place, the largest exposition facility in the country. MINExpo International '88 will combine for the first time two previously separate AMC-sponsored shows - the International Coal Show and the International Mining Show. Starting with the 1988 show, MINExpo International will be held every four years. The next show, in 1992, will be held in Las Vegas. The MINExpo in Chicago will feature more than 500 mining equipment and services exhibits covering 3 hm2 (320,000 sq ft) of exhibit space. Exhibitors will display products ranging from small safety devices to large earth-moving equipment. MINExpo is one of the few trade shows selected by the US Department of Commerce for its Foreign Buyer Program. Commerce is working with US embassies around the world to publicize MINExpo and to form delegations of visitors from many countries. Overseas visitors to the show will be assisted at an on-site International Business Center. It will provide currency exchange, translation, and other services to foreign buyers. Registrants at MINExpo will also be able to attend their choice of 27 morning-only program sessions. At these sessions, international mining experts from industry, government, and academe will analyze technical, strategic, and policy matters and discuss the outlook for the industry. "Toward the 21st Century" is the theme of this year's program. The technical workshops and managerial seminars are designed to assist mining executives, engineers, and geologists as well as mine superintendents, managers, and foremen in handling their responsibilities. Based on previous attendance at AMC international mining shows, the association says that more than 25,000 persons are expected to attend the Chicago show. It is expected that approximately 15% of the attendees will be from foreign countries. The Soviet Union will be among those exhibiting at MINExpo. The Russians have leased more than 2.8 dame (3000 sq ft) of space to display their mining machinery and equipment. It is the first time that the Russians have joined in an exhibition of mining equipment in the US. The two largest manufacturers of mining equipment in the Soviet Union, Setmash and Avtoexport, will put on display in Chicago a variety of Russian-made equipment. It will range from 100 t (110 st) heavy-duty dump trucks and diesel engines to drilling, hoisting, and conveying equipment. In addition to some 400 US exhibitors of mining equipment and services at MINExpo, nearly 100 companies will be present from other major mining nations such as Australia, Canada, Great Britain, Japan, the Netherlands, and West Germany. And, for the first time, a Chinese manufacturer will take part in the AMC show, participating with its US marketing partner.

Jan 3, 1988

By Ian Farmer, Nigel Glossop, Philip Garritty

Performance of tunnel boring machines - usually expressed in terms of penetration per revolution - is determined by relations between machine thrust and torque, head diameter and rock strength. It can be shown that for a given machine power and head diameter there is only one rock strength at which the machine performs optimally. In weaker rocks the available torque limits performance and in stronger rocks, the available thrust. Performance data shows that, historically, machines have been designed to cut weaker rocks. Optimization of thrust is required to improve performance in stronger rocks.

Jan 1, 1987

By A. M. Gaudin

In a recent paper we have reviewed principles and applications of measurement methods for contact angles and their hysteresis (22). In this paper we apply these methods to a system consisting of rutile, an organic liquid (benzene, decane, or dodecane) and water. Surfactant (dodecylamine hydrochloride) was used at various concentrations and various pH values.

Jan 1, 1964

By Nenad Spoljaric

Greensand, greensand marl, and green earth are names given to sediments rich in the bluish green to greenish black mineral known as glauconite. The word glauconite is derived from the Greek word glaukos, meaning bluish green. The term "greensand" as a rock name for a glauconite-bearing sediment is more appropriate than "greensand marl," a term that has been doggedly perpetuated in the literature. Because of its potash and phosphate content, greensand was mined and marketed as a natural fertilizer and soil conditioner for more than 100 years. The advent of manufactured fertilizers with adjustable nutrient ratios led to a decline in the use of greensand in agriculture. The material has since been recognized as useful in water treatment. Unfortunately, despite large reserves and world- wide distribution, glauconite has not been utilized to any significant commercial extent because no major application has been found for a substance with its chemical composition and properties. This is probably due mostly to a paucity of research on its potential commercial uses. Extraction of potash received considerable attention during and just after World War I. Because of relatively high extraction costs and a generally low potash content (viz., less than 8%), glauconite lost its appeal as a source of this commodity. Historical Background Greensand was used as a fertilizer in New Jersey in the latter part of the 1700s. During the early 1800s its use became more common; applications of as much as 22.5 kg/m2 were sometimes made, although recommendations for agricultural use suggested 4.5 to 11 kg/m2 (Tedrow, 1957). Many crops, especially the forage type, were said to improve with greensand application; however, because of its slow release of potash, large quantities were required. Certain greensands that contain sulfur and sulfide minerals are harmful to plant growth, and these were classified as poison, burning, or black marls. The availability of higher grade potash salts from other mineral sources and the manufacture of prepared fertilizers displaced the agricultural use of greensand during the latter 1800s. During the mid-1800s the greensand industry, centered in a small section of the eastern United States, grossed more than $500,000/y. Toward the end of the century, however, annual production had dwindled to less than $100,000 in value. By 19 10 there were only six or eight greensand producers grossing less than $5,000/y each (Tyler, 1934). There was a brief revival of the US industry during World War I because of the curtailment of foreign potash, especially from Germany. During the latter 1940s and early 1950s greensand was again recommended as a food nutrient for plants and farm crops. Agronomic studies discussed its potential as a soil additive that gradually releases potash and many trace element nutrients essential for plant growth (Tedrow, 1957). Greensand was sold with the idea that it would condition soil and absorb and hold water while its base exchange properties would release trace elements. For a short time glauconite was used in certain parts of New Jersey as a binding additive in the brick industry, and in the 1800s it was used for making green glass (Cook, 1868). In the early 1900s the base exchange properties of glauconite were recognized for water treatment and the mineral gained acceptance as a water softener. Mansfield (1922) does not mention base exchange even though this phenomenon was known in 1916 or earlier. From 1916 through 1922 several patents for the use of glauconite as a water softening agent were granted. A method was also patented for treating greensand to improve it for water softening and ready regeneration with common sodium chloride brine (Borrowman, 1920, Spencer, 1924, Kriegsheim and Vaughan, 1930). Treated glauconite, on contact with water containing magnesia or lime, takes up magnesium or calcium ions and releases sodium ions. This exchange is limited to the outer surface of glauconite grains, and when all the surfaces have absorbed their capacity, the grains must be regenerated. Regeneration, simply stated, consists of treating or backwashing the glauconite with a sodium chloride solution, which replaces the hard water elements with sodium, thus reviving the glauconite. The process has become more sophisticated due to competition among companies in the water softening business. Greensand products for water softening generally consisted of several different grades distinguished by the particular treatment the glauconite was given during processing. The standard greensand water softener was produced from natural glauconite that was only washed and classified. Its characteristics for water softening are given in [Table 1].

Jan 1, 1994

By T. D. Kaufmann

When Dr. David Gully solicited this paper last spring a few questions basic to commodity trade between the U.S. and world markets appeared perplexing. Why, for example, when the demand for aluminum was at a peak and when little expansion of capacity had taken place, was the dollar price half of what it had been at the previous peak? Or, why in 1984 when imports surged by 50% as the U.S. economy pulled out of its recession did the dollar not fall, but rather rose by 35%? And, why when the experts all seemed to agree that the dollar was grossly overvalued did the price of gold continue to decline? Surely these were extraordinary times for the mineral economist. When this paper was written in late July, 1985 the answers seemed clearer. The prices of many commodities were not low - the dollar in which they were denominated was too high. In other currencies many commodity prices were indeed high. The dollar was overvalued in trade terms by some 40% caused by an influx of short term coupon investments made by foreign money managers to take advantage of the higher short term interest rates in the U.S. relative to other international banking centers. With a decline in the relative difference in interest rates, an unhealthy buildup of foreign bank accounts and a perception that the dollar would fall, the dollar did start to decline rapidly.

Jan 1, 1985

By R. L. Virta

Four companies mined ball call in four states in 2009, H.C. Spinks Clay Co. Inc. (owned by Lhoist Group), Kentucky-Tennessee Clay Co. (owned by Imerys Group), Old Hickory Clay Co. and Unimin Corp. Production, on the basis of preliminary data, was 820 kt (904,000 st) with an estimated value of $39.4 million. That was a 15-percent decrease in tonnage from 967 Mt (1.1 mil-lion st) with a value of $44.3 million that was produced in 2008. Tennessee was the top producing state with 59 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 71 percent of production was airfloat, 18 perc

Jun 1, 2010

By J. D. McAteer

It is widely agreed throughout the mining community that federal mine safety and health legislation administered by the Mine Safety and Health Administration (MSHA) deserves significant credit for the past quarter-century's remarkable improvements in miner safety and health. Recently, however, it has been suggested that the mining industry in the United States has now evolved to a point that current mine safety and health law may be obsolete. This proposition deserves attention. Today, I propose to give it the close logical scrutiny that is its due. I conclude that the obsolescence of current mine safety and health law is not supported by the evidence. The existing mine safety and health law continues to serve as a critically important supplement to mine operators' safety programs at a modest cost to the taxpayer. At the same time, trends in a changing industry do call for responsive adaptations in the Federal mine safety and health program. I will argue that timely and appropriate responses to changing needs can be accomplished within the framework of existing legislation, provided federal officials avail themselves of the flexibility provided by existing law.

Jan 1, 1996

By Burton H. Boyum

The paper generally reviews the iron ore occurrences and regional geology of Western Australia, but features in particular the mesa deposits of PJasic Materials - Cliffs International. Initial production is planned from a aeries of mesa deposits of Eocene-Oligocene age. The ore is oölitic to pisolitic goethite and hematite. Source of the iron in the mesa deposits is thought to be from the Precambrian iron-formations. The geology and occurrences of the mesa iron ore deposits are summarized and illustrated.

Jan 1, 1964

By J. G. Groppo

A beneficiation process has been developed to provide selective separation of unburned carbon from high loss-of-ignition (LOI)fly ash. Using froth flotation to achieve selective separations requires long residence times and high reagent costs. A proprietary reagent system has been developed to address these limitations. Based on the results obtained from laboratory and pilot-scale investigations, a flowsheet design has been developed to produce two distinct usable products from class F fly ash — low LOI ash and a high-carbon product suit-able for reburning or further upgrading.

Jan 1, 1996

By John E. Bailey

The advent of Nuclear Energy has caused a phenomenal growth in the uranium mining industry. To keep abreast of this surge the mining industry has located many ore bodies, determined the best types of mining adaptable to this particular type of ore and developed a highly specialized type of operation. But, has the mining industry gone far enough in the planning? Has ?built-in? safety been included in the efficient methods of operation? Preplanning safety in the mining industry, as in all industries, takes engineering and ingenuity combined with the experience and cooperation of all concerned. A system of mining can be planned on a map and it will look good. However, when the actual mining takes place, conditions may be such that deviations from the original plans may be required because of excessive water faults or other conditions encountered. With safety we may also be required to change, to conform to the characteristics of a particular operation. People in the mining industry are well aware that loose back has killed miners each year. This condition occurred in practically all types of mines. The condition is not new to us. It is also known that explosives, haulage, machinery and conditions common to all types of mining have taken a heavy toll of human life in mining. In addition to these hazards in the uranium mines, the hazard of radon is also present, Radon is a radioactive gas liberated from ores containing radium. This gas is released into the active workings by the blasting or breaking up of the ore. Sometimes it is caused by radium contaminated water seepage from abandoned workings or from the ore body itself. Until the action of this gas on the human was known, many miners were affected. Un- less adequate precuations are taken to protect the people in these mines,, they may be exposed to this hazard, Health researchers made a study of this substance to determine how it would affect the health of the men, They also studied men who had worked in previous years, in mines known to have contained radioactive materials. All of this research contributed to the present knowledge of radon and its daughter products. It is not flammable nor explosive, but, if allowed to enter the body through the respiratory organs it can cause serious damage. Mines have been operated in the past and are still being operated, which were known to contain explosive and noxious gases, indicating that this problem can be controlled. Several states have instituted laws that make it mandatory to provide adequate ventilation and use of monitoring devices to limit radon and its daughter products to a maximum of 300 micro-microcuries per liter of air. This is considered a safe limit for sustained periods of human exposure. While the findings of research do not prove conclusively that the inhalation of excessive radon or its daugher products cause lung cancer, indications point to this as a possibility, particularly radium A and radium C1 of the daughter products. The threshold limits set by law in most uranium producing states are believed to be safe. In a few years, when tests and data now in the process of collection by interested state officials and laboratories is complete, these limits may be found to be ready for revision. Studies such as these take time. At present, the limits that are used are based upon estimates. The permissible limits of exposure to radon and daughter products include a large safety factor. It is considered that a good supply of fresh air delivered to the working places, adequate dust control, the sealing of unused or abandoned workings, the removal of mine water which is generally contaminated and a safe waiting period after blasting, will hold to a minimum the dangers from this source. There are, of course, problems accompanying each of these procedures. For example, the ventilating of untimbered raises and bringing fresh, uncontaminated air to the working places may be a problem. However, a good mining man can solve these problems as they apply in each particular operation. From the information available at the present time, the daughter products containing polonium and emitting alpha radiation, may be a health hazard. Fortunately, the half life of most of the daughter products is short, however, radium D has a half life of 22 years and presents a problem of contamination in the storage of old tailings. So we can see that failure to comply with the accepted good mining practices may have harmful effects on the health of miners. It is gratifying to note the interest in this potential hazard by the officials in the uranium ore producing states, who are making extensive studies and keeping records of the men who work in this type of mining. This all provide information necessary for preplanning safety. By contrast, little has been accomplished to control the injuries and deaths from some other factors connected with most underground mining operations. I would like to discuss briefly one of the hazards which take an annual toll in our underground mines, this is falls of back and walls. This problem or hazard is present, and will be

Jan 1, 1958

By M. Zuckerberg, E. Mader, R. Pasyar

We describe a new software product designed for the net present value optimization of multi-open-pit blended ore operations in which it is desired and/or necessary to dump some or all of the waste rock produced in the course of operations back into the voids created in the process of ore extraction. The software product simultaneously decides over the entire life-of-mine which material to mine in which year, once mined what to do with it, and where to put that material which it has decided to waste, all subject to annual blend and capacity constraints.

Jan 1, 2007