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By K. C. Jordi

Many systems which are modelled mathematically result in a model where the relationships between some or all of the parameters are found to be non-linear. These systems are usually complicated further by a desire to make the system achieve multiple and often conflicting objectives or goals simultaneously. Rozwadowski (1970) developed a model to describe the total discounted net profit of a mine as a function of the amount of ore developed and of the grade of the amount of ore mined. Dynamic programming was used to determine the policy which gave the maximum net present value. In this paper it is shown that the relationships between the variables can be approximated by piecewise linear functions. This is amenable to solution by an algorithm based on the simplex algorithm of linear programming. The goals of maximizing the net present value, the total net profit and the total gold output are incorporated simultaneously into a goal programming formulation of the system. The resulting model is characterized by a large number of disconnected constraints. These are decomposed into several smaller problems and the problem solved. The solution is examined to discover the sensitivity of the system to changes in certain parameters. In particular the interaction between the three goals is analysed to determine whether there is conflict between any of the goals and, if so, what the trade-offs between the conflicting goals are.

Jan 1, 1979

By Robert W. Waytulonis

Miners working in underground mines where diesel equipment is used are exposed to exhaust pollutants. These include carbon monoxide (CO), carbon dioxide (CO,), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), hundreds of different hydrocarbons (HC) and particulate matter. Evidence from animal inhalation studies and limited epidemiological investigations have led the National Institute for Occupational Safety and Health (NIOSH) to recommend that ‘... whole diesel exhaust be regarded as a potential occupational carcinogen ...’ NIOSH further stated that ‘... the excess cancer risk for workers exposed to diesel exhaust has not yet been quantified, but the probability of developing cancer should be decreased by minimizing exposure…’ The International Agency for Research on Cancer(IARC) reached a similar conclusion, saying that ‘... diesel engine exhaust is probably carcinogenic to humans.’ Before these declarations, there was insufficient evidence concerning the carcinogenicity of diesel exhaust. It was well known, though, that diesel exhaust caused less severe problems, such as headache, eye irritation and unpleasant odors. In 1988, a milestone was reached in the Mine Safety and Health Administration (MSHA) regulatory process. An advisory committee recommended a three-tier approach to regulating diesels used underground-approval of diesel equipment, safety and health. Diesel particulate matter may be specifically regulated. In addition, ambient air quality standards are being proposed that will establish a new standard for CO2 and lower the permissible exposure limits for the NO2, CO, SO2 and formaldehyde emissions that originate from diesels and other sources. Additional safety and emission restrictions are also proposed for diesel engines in coal mines. The goal of the US Bureau of Mines (USBM) diesel engine research program is to minimize the health and safety problems associated with underground diesel equipment use. Part of this program is focused on reducing exhaust emissions from diesel-powered equipment used in underground mines.

Jan 1, 1993

By J. Cheung, H. Rabia

The traditional methods for predicting mine air temperatures are based on steady state heat transfer models as developed by Voss (1969) and Starfield (1983). These models are useful in providing approximate predictions of air temperatures in trunk and gate roadways. More complex models are required to provide predictions along faces. In practice, the heat flow in underground mines is of transient nature and recent observations in some British Coal mines show temperature variations of up to 5°C during a working week at any one point. In addition, the recent introduction of district recirculation of mine air in British mines requires a more precise prediction of air temperatures during start up of the system or during breakdown. A transient heat transfer theory based on the work of Jordon is presented. The method lends itself easily to computers due to the large number of calculations involved. The proposed transient model is validated using actual temperature data collected in roadways in Wearmouth Colliery in the North East of England. The transient results are compared with the steady state predictions of Voss (1969). Finally, predictions of air temperature in roadways for a recirculation system will be made using both the transient and steady state models. Temperature predictions along faces will be made using a separate model.

Jan 1, 1989

By Max John

INTRODUCTION One of the main advantages of the New Austrian Tunneling Method (NATM) is its adaptability to varying rock conditions. This method is therefore successfully applied when complex geologic features are expected which cause uncertainties in the prognosis of the rock mass behaviour, as was the care at the Arlberg Expressway Tunnel. Furthermore, by employing the NATM problems are avoided when encountering varying geologic conditions or even extension fault zones along the tunnel, as was the case at the Dalaaser Tunnel and Perjen Tunnel. The NATM can also be used for rock and soil. The following examples will show how various rock conditions can be mastered. In accordance with the NATM all tunnels which will be discussed are road tunnels having a cross section area between 70 and 100 m2. The construction consists of a primary support, which ensures stress redistribution during excavation (Figure 1). The primary support is reinforced shotcrete strengthened by steel arches, when necessary, and rock bolts. When encountering rock pressure, swelling rock or soil, the primary support is suplemented by an invert arch. The purpose of the secondary lining is to increase the safety of the tunnel with regard to long-term stress redistribution processes or changes in rock mass properties as well as to protect the insulation. The secondary lining consists of cast concrete without reinforcement and is generally 0.25 or 0.30 m thick.

Jan 1, 1981

By Joseph W. Kupfner

It is a recognized fact that a good maintenance program is a pre-requisite for minimum delay costs and maximum availability of equipment. To develop such a program and to make it effective, one must establish detailed instructions pertaining to inspections, lubrication, servicing, and/or replacing of various parts. A schedule must also be established for these maintenance checks, whether they be weekly, monthly, or whatever period is essential for the equipment. The number of tasks to be performed becomes monumental, and the administration is beyond error-free human capacity. It is for this reason that the computer must be an essential element in any efficient and economical preventive maintenance program. The evolution of a computerized maintenance program began some 18 years ago in the Mining Division of USSteel. It started with a manual system of preparing cards containing preventive maintenance instructions that had to be performed on some regular basis. We were very quickly overtaken by the massive task of administration and distribution of instruction cards to the users. The task became insurmountable as more mines were added to the system, mines that were spread over a large geographic area. It also became evident that the ability to make changes in equipment assignments and in the "what to do" instructions would require more time than had been anticipated.

Jan 1, 1986

By W. L. Fourney, D. C. Holloway, J. W. Dally

Introduction Improvements in the process of rock excavation by blasting involves better control of one or more phases of the fracture process immediately after detonating the ex- plosive charge. Total control of the process involves individual control of (1) The number of fracture planes. (2) The crack initiation sites. (3) The direction of crack propagation (usually radial). (4) The stress field driving the fracture front. Fracture plane control is usually accomplished today by using the smooth wall blasting method; however, investigations by the authors (1) indicate several areas where this method could be improved. These improvements include: a) generation of stress concentration factors at the location of the initiation sites; b) protection of the remaining region of the borehole wall to inhibit initiation of any cracks not associated with the fracture plane and fragmentation pattern; c) limit peak detonation pressures to avoid borehole crushing and maintain by stemming residual gas pressure in the bore- hole during the crack propagation period. This paper describes experiments con- ducted with a charge holding device fabricated from thin-wall steel tubing which was partially slit at fracture locations. The tube lined the bore-hole in laboratory tests to simulate smooth wall blasting. Results showed close control could be achieved relative to both the number and the location of the fracture initiation sites.

Jan 1, 1977

By Dietrich F. C. Hudewentz, Alfred H. F. Lücker

For centuries tunnellers have made use of the experience of miners. In West German coalmining tunnellers have returned the impulses in recent years by giving the miners valuable stimuli with the result that a technology has evolved which benefits drill and blast heading, opens the door to TBM heading and has developed special measures for difficult strata conditions in deep coal mines. WHAT DO THESE ROCK HEADINGS LOOK LIKE? The main roadways dealt with in this paper have crosssections of 20 to 40 m2, big enough to allow the massive airflows needed to aircondition the mines. Because of the difficult strata conditions they have to be supported: in shotfired headings mainly with multi-element arches, in TBM headings with rings of 6 to 6.5 m diameter. In West German coalmining the majority of rock headings are blasted. The proportion of rock headings driven by TBM was 11 % in 1980 and 16 % in 1981, a rising trend expected to continue. Drill and blast headings Drill and blast headings are normally equipped with two or three-boom electro-hydraulic jumbos, electro-hydraulic crawler-mounted loaders with 1.2 m3 shovel capacity, a movable working platform and both chain and belt conveyors for dirt clearance to the minecar loading point. Fans and air-condition plant complete the equipment. Spacing between arches is usually 0.8 m. Investment for this type of mechanisation works out at around 1.3 m DM.

Jan 1, 1983

By G. Reed Marchant

In 1967 the US Congress passed the "Clean Air Act." This act was amended in 1970. As a result it soon became obvious that American industries were going to have to make significant changes in their methods of operation to be able to comply with quickly developing federal regulations. One of the first regulations developed was on sulfur dioxide. For this reason, the nonferrous smelting industry was immediately affected by these new regulations. This is true because the smelting process produces sulfur dioxide as a natural product of combustion when the sulfur-bearing ore is oxidized to purify the metal. The federal government's approach for setting standards included public hearings at which government, industry, and private citizens were allowed to make comments. For this reason, it was apparent to Kennecott's Metal Mining Div. that it was desirable to make a maximum effort in working with the agency to see that correct input was provided at the hearings to assist the government in setting fair and realistic standards. It was also obvious that more complete monitoring would be required. It soon became apparent that the efforts required input from many levels of the corporation from the chief executive to the plant operators. In order to accomplish both the administrative and the technical needs, an organization was needed that could respond quickly to these needs, obtain information from diverse sources, and bring it to focus in an organized approach to the problem.

Jan 1, 1979

By J. A. Finch, J. Yiantatos, A. R. Laplante

This paper re-examines the mixing conditions in the collection zone of flotation columns. These have in the past been characterized with a single uniaxial dispersion coefficient, E. The relationship between E and column diameter, Dc, is examined based on residence time distributions (RTDs) in columns of Dc ranging from 5.lcm to 184cm. Results agree with published correlations in chemical engineering, i.e. E a Dc '" , Data explain why pilot columns display significant upgrading between the feed level and the interface, whereas plant columns do not. It also suggests that, for plant columns, the full collection zone (up to the interface) can be considered when calculating the residence time. A mathematical model considering two regions of different mixing was compared to the single E model. Both models adequately fitted measured age distributions inside the column and overall RTDs. Measured and simulated mixing characteristics are compared to those of flotation banks, using a tanks-in-series approach; banks of comparable mixing to columns are identified.

Jan 1, 1988

By F. F. Aplan

Mineral process engineering is a small but important part of the nation's raw material industry. Minerals are usually processed in large plants of high capacity, at low cost, using few engineers and operators, and at an ever-increasing level of plant sophistication. The magnitude of the mining industry is huge, with about 4 Gt (4.5 billion st) of ore, coal and industrial minerals mined annually in the United States. Industries such as construction, manufacturing and power generation rely heavily on a strong US resource base to maintain a competitive edge. Though rooted in classical chemistry, geology, physics and mathematics, a mineral process engineer must be trained in the science and engineering required to process raw materials. A modern mineral processing program still stresses the traditional aspects of the profession. But it also emphasizes particle technology, applied surface chemistry, chemical processing of ores, solid-fluid separations, process and equipment modeling and optimization, materials handling, personnel management, maintenance and environmental and health aspects. In such areas as particle technology and some aspects of applied surface chemistry, mineral processing academic programs have taken a leadership position in supplying specialists to a variety of other industries. The objectives of a mineral processing program are: • to furnish personnel to support the basic raw materials industries (undergraduate programs); • to provide a research and development base for industry (graduate programs); and • to provide expertise in particle technology, applied surface chemistry and environmental programs for other industries (undergraduate and graduate programs). In the United States, mineral process engineering programs have historically been associated with mining and metallurgy departments. The recent movement of metallurgy programs away from primary processing towards materials science has created the need for a new accommodation.

Jan 1, 1992

By Bruce W. Cavender

In an effort to lower production costs and improve profitability, mining companies have adopted a variety of management practices emphasizing productivity and cost containment. One set of practices that has been used successfully in the manufacturing and electronics industries is "world-class manufacturing" (WCM). It is applicable to mining as well. World-class manufacturing is based on the twin concepts of "just-in-time" inventory practices and total quality control. A few mining companies have implemented quality control programs that are similar to WCM in some ways and substantially different in others. This article considers the use of WCM in the processing environment, although the techniques are applicable throughout a mining operation. The article is also mindful of the variety of customers to whom mineral products are sold. Industrial minerals producers may sell brand-name products to specific customers with exacting requirements, while metals producers often sell their fungible output on a faceless commodity market. Customer requirements are emphasized in WCM, and so the range of these requirements must be recognized. World-class manufacturing In any milling process, specific goals are set for product and process characteristics - concentrate grades, minimum daily throughput, moisture content, etc. WCM has two overriding objectives: the reduction of deviation from these standards, and the reduction of variability in all aspects of the process and product. By definition, reduction of deviation also includes minimizing plant downtime for repairs or process changes. WCM plants use just-in-time inventory practices and total quality control. WCM plants use these techniques to simultaneously improve productivity and reduce costs.

Jan 1, 1993

By D. L. Schenk

The Navajo Mine is exclusively a multiple-seam surface coal mine located in the northwest comer of New Mexico. The property is situated entirely on the Navajo Indian Reservation. It is owned and operated by the Broken Hill Propriety Co. Ltd., of Melbourne, Australia. The mine began production in January 1963 with a long-term fuel supply agreement with the Four Corners power plant. The 2175 MW nominal generating capacity of the Four Corners powerplant consumes 7.2 Mt to 7.7 Mt/a (8 million to 8.5 million stpy) of coal. The Navajo Mine has estimated reserves totaling 1 Gt (1. I billion st) of strip minable coal. Only about one-third of that total is presently committed to the generating station. As development continued over the years, mining operations advanced into more complex geologic areas to satisfy the utility's demand for coal. To optimize the committed reserve and provide competitively priced coal to the customer, the Navajo Mine began developing a new pit in June 1986. The Dixon Pit boxcut development was completed in April 1987. About 6 hm3 (7.9 million cu yd) were stripped, uncovering 929 kt (1 million st) of coal. Strip ratio was 7.74:1 including 36.8% rehandle of prime yardage. This case study of the fourth production cut highlights a variety of dragline stripping techniques including highwall bench (overburden) side cast, intermediate highwall bench (parting-interburden) side cast and spoilside bench (partings-interburden) stripping methods. The Dixon Pit offers considerable challenges in the surface recovery of up to seven seams of coal within the 1432 m (4700 ft) of total pit length.

Jan 1, 1990

By J. Villeneuve, G. Fourniguet

Simulation of Mineral Processes is now commonly used by the Engineers in charge of plant design or optimization but a good knowledge of the simulation tool is still needed to conduct a project. A new level of algorithm has been defined above the simulator to answer directly to the user's questions. This level has been called the supervisor of simulation, which is using the automation concepts of sensors and actuators. At any place of the flowsheet (i.e., a stream or an equipment), the user may indicate which value could change by graphically implementing an actuator. Then, he can evaluate the effect of the variation of this value at any other place of the flowsheet by inserting a sensor. Thus, by example, it becomes possible to look at the evolution of the recoveries and/or the circulating loads when scanning an interval of the possible teed flowrates. This approach conducts to an increased facility in using a simulator and in analyzing the predictions. It is also a very valuable tool for permitting to characterize the sensibility of the simulation results to the variation of some settings (e.g., load of grinding media, rotation speed, water addition, etc.) or feed characteristics (e.g., flowrate, sizes, grades, grindability, etc.). Thus, the most important variables can be identified for design and pre-control optimization of plants. This new level of simulation will be implemented in a further version of the USIM PAC simulator and selected examples are presented.

Jan 1, 1995

By Craig Cina

Transporting goods from producers to consumers is a fundamental part of the US economy. The demand for transportation closely reflects the economic health and well-being of the nation's industrial, commercial, and agricultural sectors. The inland waterway barge industry has traditionally played a key role in transporting needed commodities to industries on an economical basis. Barges account for 10% of the domestic intercity tonnage carried by all transportation modes. Water carriers operating on inland waterways hauled more than 450 Mt (500 million st) of cargo in 1980-up from 428 Mt (472 million st) in 1970. Inland Waterway Shipments Metallic and nonmetallic minerals comprise one of the largest commodity groups moved on inland waterways. As illustrated in Table 1, metallic and nonmetallic mineral shipments accounted for more than 69 Mt (77 million st), or nearly 15% of all commodities shipped in 1980. Putting this tonnage in perspective, coal and petroleum represent the two largest commodities moved on inland waterways. In 1980, petroleum and petroleum products accounted for 138 Mt (152 million st), or 28% of all commodities shipped. Similarly, coal represented 120 Mt (132 million st), or 25% or all commodities shipped. Even though shipments of metallic and nonmetallic minerals are smaller than coal and petroleum, they still account for a sizeable portion transported. The inland barge industry moves a variety of metallic and nonmetallic minerals ranging from manganese ores to building cement. Minerals transported by barge include: • iron, copper, bauxite, and manganese ores for metal production; • lime and limestone for construction and electric utility scrubbers; • phosphate rock, natural fertilizers, and gypsum for agricultural needs; • sand, gravel and crushed rock, clay, asphalt, tar, and pitches, and building cement for construction purposes; and • a host of other minerals to meet industrial needs. A few mineral commodities are responsible for a large proportion of waterborne mineral shipments.

Jan 10, 1982

By J. F. McDonald

On December 8th of last year, the new St. Clair River tunnel was holed-through to Port Huron, Michigan. The tunnel, commissioned by the Canadian National Railway, was needed to replace an existing tunnel that had been built between 1889 and 1890, and had remained in continuous operation until the new tunnel was opened to traffic in April of this year. The original tunnel, after more than 100 years of service, was still structurally sound, but was too small to accommodate the double stacked container cars and other advances in the railroad's equipment that had developed over the years. Prior to the construction of the first tunnel, all freight was barged across the river. It was a slow, expensive process, which in winter was sometimes impossible. The nineteenth century tunnel was built in twenty months, utilizing two shields that mined to the middle from each end. The lining, which is still in excellent condition, consisted of bolted, cast iron segments, with an O.D. of 6.4 meters. It was the first sub-aqueous tunnel built in North American, and it's use of compressed air under the river and hydraulic power on the shields may also have been firsts. The digging was done by hand, and the muck hauled out by mule drawn wagons. Boulders and methane gas were reported to be a constant problem during the drive, and compressed air sickness was common, but when the two shields came together in August of 1890, it was reported that the alignment was within 6 mm. The new St. Clair River Tunnel was constructed for basically the same reason as the original. The larger equipment which the railroad is using today would not fit through the old tunnel, and once more they were forced to ferry the cars across the river.

Jan 1, 1995

By Mario Eduardo Rossi

The Universal Kriging (UK) and the Ordinary Kriging (OK) systems of equations are variations of the well-known system of Normal Equations. They differ only by the number of constraints present in the system. The dual version of these sytems enables one to interpret kriging as the fitting, of an interpolation surface, whose components are a series of variogram functions plus a polynomial trend model. This trend model should account for any systematic decrease or increase of the variable over the study area. It is shown that modeling the trend is useful only when the locations being estimated are beyond the range of influence of neighboring data (extrapolation cases). A case study based on a public-domain coal data set is presented. The variable described (seam thickness) shows an actual trend of increasing data values towards the NW corner of the region considered. UK and OK are used to estimate coal thickness at locations within sample data range (interpolation cases). The UK algorithm that includes a model for the trend does not improve the estimation when compared to the simpler OK algorithm with no trend model. Thus, in interpolation situations, the simpler OK algorithm is recommended.

Jan 1, 1989

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

During the past decade, international mining companies have descended on South America. Countries like Chile, Brazil and Peru have seen billions of dollars in exploration and development funding turn their once meager mineral industries into mining giants that have become the envy of the world. Part of this outpouring of foreign investment in those countries has been because each has privatized its state-owned mining companies and has liberalized its foreign investment laws. In addition, they have rewritten their mining codes to encourage minerals development and passed new tax laws that have made natural resource development more attractive. Now these same international mining companies are turning their attention to Argentina. This a country that, like Chile, Brazil and Peru, has a wealth of largely un- tapped mineral resources. And Argentina wants its share of the foreign investment that its neighbors have enjoyed. With that in mind, ministers of Argentina's natural resource agencies came to Denver, CO to meet with mining executives and pitch their country's mining industry. The meeting, attended by about 200 people, was sponsored by the US Trade and Development Agency and organized by the World Trade Center Denver. Others involved were the Colorado Mining Association, the Colorado International Trade Office and the Secretariat of Industry, Commerce and Mining of Argentina. The following is a summary of a report on Argentina's mining industry. It was prepared by Anderson & Schwab Management Consultants and distributed to attendees as part of the meeting's program.

Jan 1, 1998

By B. Rao Pothini, Julio H. Thaler, W. L. Finlay

The White Pine room-and-pillar mine started in 1955 from a suboutcrop, down gentle dips, and with a competent sandstone roof. As mining depths increased, extraction decreased 1% every 35 feet. Moreover, roofs became shaly and less competent, and regions of high fault and joint densities, sometimes with and some- times without high lateral stresses, increased the tendencies towards roof falls. Instinctive reactions towards narrower openings did not alleviate the problem. Careful consideration of rock mechanics principles culminated in the development of two variants to the conventional room-and-pillar mining system based on the concept of stress relief through load deflection. The two systems-EquiAdvance Cave, and PressureArch Panel Mining-are complementary. The objective of the former system is to provide relief from lateral stresses through advance caving and in the process also to achieve higher extraction at depth. Where surface subsidence cannot be allowed, the alternative PressureArch Panel concept is utilized to provide stress relief and moderately high extraction ratio. Both systems have been under trial for over three years and, together, produced over three million tons of copper ore. These two systems, and their production test results to date, are described.

Jan 1, 1977

By J. W. Oberholzer, C. F. Meyer

The increased use of continuous miners to extract thicker coal seams has necessitated the use of enhanced ventilation systems in the headings. Due to the increased face size, more ventilation is required to effectively dilute the liberated methane down to acceptable levels. If more air is directed to the face an increase in the entrainment of dust creates an increased potential for workers to be exposed to dust. To enable the ventilation systems to reduce the methane levels and the levels of the airborne dust the ventilation systems in the heading have to be carefully designed. The matter is made more complicated through the use of other ventilation methods like jet fans, air-moving sprayfans on the continuous miners and high capacity scrubbers on the continuous miners. To enable the design of a balanced ventilation system in seam heights of over five metres requires methods that consider the system in a three- dimensional manner rather than in a two-dimensional fashion. Through the use of computational fluid dynamics (CFD) coupled with appropriate methods of taking underground face ventilation readings these problems can be solved in a cost effective way. Using computer modelling, ventilation methods can be designed and assessed instead of using costly underground trials to test the alternatives. Use of this system has led to a higher level of ventilation design as well as a more effective method to combat the health and safety hazards in coal mine headings.

Jan 1, 1995