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By A. L. Mular

Optimization has been defined as the procedure of locating the best of something or the best way of doing something (Mular, 1971). Several texts (Himmelblau, 1972; Ray and Szekeley, 1973; Box and Draper, 1969; and Lee, Adams, and Gaines, 1968) on the subject are available. Such techniques have been placed in two categories, namely, off-line optimization and on-line optimization. For the former, an optimization model is employed; for the latter, a black box approach is involved. The essence of an optimization problem becomes obvious, when a response surface is considered. Suppose that a response (in this case, a criterion of improvement such as profit per day; grade of concentrate per day) denoted by Y, depends only on two variables, X1 and X2, which can be manipulated and controlled. The relationship between Y, X1 and X2 may be represented graphically as shown in Fig. 1. The diagram is called a response surface and its height, Y, is determined by X1 and X2. Points associated with equal responses constitute response contours. The shape is that of a hill, and optimization is the procedure of ascending the hill to reach the top (maximum). In practice, a response surface is subject to disturbances which distort its shape and shift its location from time to time, so that the exact location of a maximum is imprecise. Generally, constraints (restrictions of some sort) on responses and manipulable variables serve to define a region of permissible operation.

Jan 1, 1979

By Holger Witthaus

Various seam conditions had been examined during longwall production at RAG German hard coal mines. Based on the field data a prediction method was developed considering separation planes as influencing factors for roof falls at the face. The characteristics, orientation, and density of separation are important factors on the occurrence of roof falls. In addition to geological influences, the performance parameters and geometry of support must be considered and optimized for the prediction and prevention of roof falls in a longwall face. Based on detailed macro- and microscopic investigations of e coal seams considering various ranks of carbonization, the origin and characteristics of separation planes are determined and a strata-specific influence on roof fall is interpreted. It was assessed that the coal face fracturing and displacement caused by the stress depend on the floor and roof strata conditions due to activation of the existing separation planes. Field studies are shown giving an idea of influences by advance rates of the longwall face, support delay and hydraulic pressure to the roof control in longwall faces in depth of more than 3000 ft. The analysis includes the application of specific software developed for longwall roof fall prediction as a result of a European research project. The software allows a laminar graphic display of roof fall probability, which is used for recognition of risk areas and risk management.

Jan 1, 2009

By R. D. Rein

The Henderson mine is a large continuous panel caving operation in central Colorado. The orebody is roughly 760 m by 910 m and will be extracted from two production levels. Each level is divided into three north - south panels 244 m to 317 m wide. The general arrangement of a production level and its associated undercut drifts is shown in Figure 1. The production drifts (3.6 m by 3.7 m) are spaced 24 m apart center to center and have undercut drifts (3.4 m by 3.8 m) 17 m directly above them. The production drifts are interconnected with drawpoint crosscuts (4 m by 4.3 m) driven on 12 m centers. Drawpoint crosscuts receive substantial brow steel and concrete support prior to undercutting. The brow steel is a 15 cm by 46 cm wide flange beam with a 2.5 cm wear plate to box in the 'cave' side of the beam. The concrete is a minimum of 0.3 m thick and the batch design results in 27 500 kPa strength. The finished drawpoint opening is 3.7 m by 3.2 m with a choke area of 3.7 m by 2.4 m. (Figure la) Undercutting and bell formation is accomplished by blasting rings of 7.6 cm holes drilled from the undercut drifts. The rings have a burden of 2.0 m and six rings develop one complete bell.

Jan 1, 1985

By J. Marts

Underground longwall coal mining sections are operated as sealed gobs if the coal is prone to spontaneous combustion. Sealing along the gate roads during longwall face retreat limits the flow of fresh air (oxygen) into the gob and thus deprives the spontaneous combustion reaction of oxygen. In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), researchers at the Colorado School of Mines have used computational fluid dynamics modeling to simulate the flow of gases in sealed longwall gobs. The models were validated using measurements and observations from the field and demonstrate that targeted injection of nitrogen along the gate roads inby the face can be used to control the size and location of explosive methane clouds within the go band to minimize or eliminate the explosion hazard resulting from the formation of flammable methane-air mixtures.

Feb 27, 2013

By Qingqing Huang, Aaron Noble

The Mineral & Metallurgical Processing Division (MPD) of the Society for Mining, Metallurgy & Exploration held the first MPD Student Video Contest during the spring of 2021. The event showcased the work of 18 graduate and undergraduate students from several U.S. and international institutions. The contest began in January when students submitted a onepage abstract for judging. Over the next several months, they developed a three-minute video that further explained their research findings. Both the abstract and video were evaluated by a panel of judges, and the top-placing participant was recognized at an MPD virtual event held on June 10.

Sep 13, 2021

By C. S. Caldwell, L. C. Thompson

Mine closure and reclamation issues have evolved over the past several years becoming further complicated by stricter standards and by the cmrent economic climate and price of gold. Many mine permits are calling for more stringent remediation of spent ore heaps and tailings. Leachate solution water quality must meet strict discharge criteria for multiple parameters besides cyanide at mine closure. Closure standards are more difficult to meet and most mines do not have an increased budget at the end of mine life to deal with the falling standards. These issues make additional gold recove1y at the end of mine life a critical problem in financing some closure operations. Another issue is the length of time that must be budgeted for heap rinsing operations. Innovative biological processes developed and applied by Pintail Systems, Inc. at numerous mine closures have indicated that bio-processes can significantly enhance gold recovery dur­ing heap cyanide bio-detox over the recoveries expected from rinse operations. If heap rinsing can be eliminated or reduced and if gold recovery can be improved at the end of mine life, many mine closures may be possible with processes that pay for themselves or generate profit. Additional advantages of the bio­detox technology is that it can be engineered to treat multiple contaminants besides Weak Acid Dissociable (WAD) cyanide. Other contaminants treated in heap process solutions include nitrates, ammonia, heavy metals, thiocyanate and total cyanide. At the Cripple Creek and Victor Mining Company Ironclad Mine near Victor, CO, 5 million tons ofrinsed, heap leached spent ore were biologically detoxified to reduce cyanide content, enhance gold recovery during bio-detox and to reduce dissolved metals in heap leachate solutions. During the bio-detox treatment period a substantial improvement in gold recovery allowed the detox oper­ation to operate as a profit center. Final gold recovery was at least twice what was expected from a normal rinse operation.

Jan 1, 1998

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By R. R. Dorfler

The existing regrind circuit at the Climax Operations uses sodium cyanide and Nokes reagent to reject pyrite, copper, and lead minerals. Laboratory flotation studies were performed using feed to flotation following first-stage regrinding. The effects of conditioning time, pH, and the concentration of depressants such as Nokes reagent and sodium cyanide on the rejection of pyrite, lead, and copper minerals were investigated. The metallurgical results indicate that, in the presence of depressants, the rejection of copper is strongly dependent on the pH. Preliminary mill testing confirmed the finding. The rejection of impurities is also dependent on conditioning time. The recovery of molybdenite is independent of the variables investigated.

Jan 1, 1981

By Todor P. Stefanov

The thermal draught within ventilation networks of underground mines depends to a great extent on the shafts depths and degree of change of ventilating air density. When the topology and space orientation of a ventilation network are constant, the dynamics of thermal draught is determined mainly by the variations of the heat- and mass-transfer processes in the openings. This conclusion follows from the well known basic theoretical notions about the thermal draught-aerostatics and thermodynamics [1]. Quantitative evaluation about the influence of heat- and mass-transfer processes on dynamics of thermal draught could be made through: direct mine measurements, special experiments and with the aid of mathematical models. The first two methods produce sufficiently accurative results, however it is very difficult to perform such studies, particularly when these processes are evaluated within a large scope and multifactor aspects. Mathematical models of thermal draught allow to overcome easily these difficulties. The degree of accuracy of results, obtained by this method, depends to a great extent on the degree of approximation achieved by the model to the real heat- and mass-transfer processes. In this paper, with the aid of Bulgarian developed method, algorithm and computer program V WT-4 - for complex evaluation of ventilation parameters in active mine ventilation networks [2], the authors investigate some changes in the thermal draught. Basically, the method is an iterating evaluation of an open set of equations, which represents relationships between the following basic parameters of a mine ventilation network: [ ]

Jan 1, 1980

By K. L. Kasperski, M. T. Ityokumbul

The effect of reaction conditions on the desulfurization of oil-sand coke residues was studied. The variables investigated were temperature, reaction time, heat transfer resistance and mode of caustic soda addition. The results show that oil-sand coke desulfurization increases with temperature, reaction time and heat-transfer rate. In an oxidative environment, coke combustion during molten-caustic leaching (MCL) commences at temperatures above 500 °C. The mode of caustic addition has no effect on coke desulfurization.

Jan 1, 1996

By Mutombo Nombe, Avimanyu Das, Rick Honaker

Enhanced gravity separators (EGS) provide a more efficient separation than froth flotation when cleaning coal in the 150 x 25 µm particle size range. To improve the performance of an EGS unit, air bubbles were injected into the feed stream in an attempt to decrease the apparent density of the coal particles due to the formation of bubble-coal particle agglomerates. Air injection had a significant impact on operating characteristics and separation performance. Coal recovery was increased by 10 to 20 absolute percentage points while a 2 percentage point drop in the minimum product ash content was also achieved.

Jan 1, 2005

By Wayne P. Myers

Electricity, as normally thought of by a layman's definition, is a man- made force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by Mine Safety and Health Ad- ministration (MSHA), as well as the various state departments of mines.

Jan 1, 1981

The National Mining Association’s (NMA)MINExpo International ’96 is shaping up to be the organization’s largest. About 30,000 mining industry business and technical professionals are expected to descend on Las Vegas, NV Sept. 9-12 to take part in the 25 technical sessions and visit the more than 900 exhibitors who will be showing off their products and services. MINExpo will be the largest mining equipment and services exposition in the United States this year. Exhibits at MINExpo will fill the Las Vegas Convention Center, parking lots and part of the Hilton Center, located next door to the convention center. NMA estimates that this year’s show will cover more than 46,450m2 (500,000 sq ft) of exhibit space. Some of the exhibits on display will include haultrucks, hydraulic shovels and excavators, conveyors, continuous miners and tunneling machines. In addition, an array of computer equipment and software will be demonstrated. A new feature this year will be a helicopter pavilion, located in the Hilton Center. Helicopters and fixed-wing aircraft have become indispensable to many remote mining operations. NMA said that at least one full-size helicopter will be on display.

Jan 1, 1996

In 1996, O&K Orenstein and Koppel Inc. announced big plans to increase its presence in the US mining market. Even though the company, a part of Ger- man-based O&K Mining GmbH, has been in the United States for about 100 years, it has lived in relative anonymity. That despite being one of the largest makers of hydraulic mining shovels and excavators in the world. The plan must be working. In the 14 months through December 1996,O&K increased its sales to surface mines and quarries in the United States by 250'70, according Rolf Weber, company president. "In the next five years, we anticipate total revenue from our US operations will grow from the current $50 million to $200 million," he said. "Toward that end, we have concentrated our efforts on the supply of reliable, high-output machinery and responsive service after the sale."

Jan 1, 1997

By Robert Rautenberg, Ted Budd

The paper will discuss the successful construction of the largest dollar value ($194.5 million, U.S.) TARP (Tunnel and Reservoir Plan) project built to date for the Metropolitan Water Reclamation District of Greater Chicago. The mining and lining of the 18.5km (11.54 miles) tunnels will be emphasized. The tunnels were driven utilizing three TBMs ranging in size from 9.85m (32.33 ft) to 3.70m (12.16 ft) in diameter. The operations surrounding the 11,546m (37,876 ft) long 9.85m (32.33 ft) diameter tunnel will be highlighted. A total system concept was utilized to attain mining rates up to 29.3m (96 ft) per shift and lining productions of 58.5m (192 ft) per day. The reliability of these systems was instrumental in the completion of the project more than a year ahead of schedule.

Jan 1, 1995

By Robert L. Runkel, Kenneth E. Bencala, Briant A. Kimball

Thousands of abandoned and inactive mines are located in environmentally sensitive mountain watersheds. Cost-effective remediation of mining sites in these watersheds requires knowledge of the most significant sources of metals to surface waters. The significance of a given source not only depends upon the concentrations of a toxic metal, but also on the total mass, or load of metal added to the stream. To determine loads, we combined tracer-injection methods, to provide reliable discharge measurements on a watershed scale, with synoptic sampling, to provide spatially detailed concentration data. The resulting load profiles indicate which sources have the greatest effect on streams, where natural attenuation of metal loads occurs, and where ground-water inflows are located. This is part of the information needed for planning remediation of mine-drainage effects. The approach is illustrated by comparing zinc loading curves from three watersheds affected by mine drainage.

Jan 1, 2000

By Jim Merza

The recent heightening of environmental issues has forced more and more mining operations to focus on developing new methods to control dust problems encountered at their concentrate dryers, stock piles, tailings ponds and during the loading, transportation and unloading of their products. The development of dust control agents requires a quick reliable and most of all accurate method to evaluate the performance and to optimize the formulation of these products in the laboratory, thus avoiding expensive field trial evaluations. This paper gives an overview of the industry requirements for specialty dust control agents, application techniques and current laboratory evaluation procedures. The paper will also outline the development of a unique dust suppression testing apparatus called the "Dust Box, which is used to evaluate chemical dust suppressants at the laboratory level. Laboratory results from two test programs on different substrates are presented in the paper.

Jan 1, 1994

By J. G. Smith, L. P. Sheets

Introduction Potential applications that exploit the electrical properties of coal measure rocks include: (1) radar sensing of coal face, floor, and roof for automated mining operations; (2) underground wireless communications; and (3) sensing extent of subsidence, blasting operations, coal gasification bums, and moisture migrations. Impediments to exploitation of electrical properties include: (1) a lack of reliable electrical properties data for in situ conditions and (2) a lack of correlation data between electrical properties and other relevant physical properties. In this paper data are presented for electrical conductivity and permittivity for Appalachian and Illinois shales for a frequency range 2 x 10 to 2 x 10 Hz. These data are useful in establishing in situ electrical property variability, lower limits, and anisotropy. Electrical proper¬ties measurement and values for other coal measure rocks are discussed as well. Laboratory measurement For the frequency range investigated, a capacitance bridge and Q-meter were employed. These instruments are designed to yield bulk values of permittivity and conductivity. Disk samples of thickness 0.396 cm (0.156 in.) and diameter 2.54 cm (1 in.) were machined from cores obtained from the two coal basins. While both the capacitance bridge and the Q-meter must be balanced manually, the bridge has an analog-to-digital interface and an attached computer specifically designed to expedite data collection and interpretation. Sample holders are critical components in the measurement process. A Hartshom-Ward holder was employed with the bridge and a Marconi micrometer jig was used with the Q-meter. Neither commercial sample holder was designed to regulate ambient humidity conditions. Because water adsorbed on sample faces may cause errors approaching 100%, special enclosures were designed for both holders. Each enclosure contains a flush-mounted externally-manipulable carousel, an externally-manipulable rigid arm that can accomodate translational motion and three-dimensional rotation, a compartment for humidity regulating solids or liquids, and a humidity sensor. Each enclosure will accomodate several samples that can be manipulated within the enclosure without opening it. Experience gained during this research demonstrated that humidity regulation was necessary to obtain repeatable results. Grinding and polishing shale to a very thin thickness (about 0.4 mm) was shown to cause changes in electrical properties as well. These latter changes were attributed to alterations in the water content. Theoretical considerations A very comprehensive discussion of the electrical properties of sedimentary rocks is available in literature (Sen and Chew, 1983). These authors reviewed the work of others and proposed modifications to better explain the frequency dependent behavior of the permittivity and conductivity of rocks. A large portion of their article was devoted to explanations of large relative permittivities at low frequencies such as observed in this research. They noted that the electrical properties of formations containing shales and clays are the most difficult to explain. Sen and Chew noted the need for additional experimental data and further refinements in theory. Results Shales, limestones, and sandstones were examined for a single 150-m (492-ft) core from Pennsylvania and for a dark shale from a southern Illinois coal mine. Figures 1 and 2 illustrate the conductivities and relative permitivities for the southern Illinois dark shale at a single location. The differences in electrical properties clearly

Jan 1, 1987

By Yutaka Mochida

OUTLINE Beginning in 1946, a careful geological survey was made of the Tsugaru Straits. In 1964, excavation of the exploratory tunnels were started to observe the characteristics of faults and rock formation directly, and to study construction methods of excavation and sealing water inflow. In March 1971, the investigation stages were over, and in April 1971, the construction project was authorized from the government. The geological features in the straits may be divided into three broad classes. One third consists of andesite on Honshu side. The other two thirds consists of tuff. The middle of the straits consists of tuff, so-called Kuromatsunai-layers. On Hokkaido side, it consists of tuff, called as Kunnui-layers. There are nine noteworthy faults on the route. Prior to the excavation of the main tunnel, the horizontal pilot tunnels and service tunnels are made. Exploratory borings are taken to confirm the geological conditions and the presence of gushing water. Groutings for sealing water inflow are carried out when necessary. In geologically bad conditioned sections such as disintegrated or fractured zones, special methods are applied. In geologically good zones, the tunnels are bored through using the same methods as for a mountain tunnel driving. The pilot tunnel being constructed at the sea bottom is under direct control of the Japan Railway Construction Public Corporation. The service tunnel and the main tunnel are being excavated by contractors.

Jan 1, 1981

By C. Anderson, D. Kolstad, M. Unger

Operators are often challenged with the management of water throughout the life cycle of a mine. High water levels can lead to physical or chemical instability of water-retaining structures. Operators need to predict changes in water levels to make timely operational decisions and plan for contingencies, particularly in remote legacy mines. A closed mine in northern Canada with no permanent on-site personnel had a simple water balance model that was effective for decades to inform annual water treatment operations. In recent years challenging water quality and more stringent effluent quality criteria has strained those treatment operations and led to more water being stored. Additionally, the region has experienced more precipitation and higher water levels, which have triggered emergency response activities. A calibrated probabilistic model was used to provide enhanced prediction capabilities and to identify key sensitivities in the water balance for monitoring. A several-year case study shows the value that this modelling tool provided for mobilizing personnel and performing response actions, particularly the inclusion of probability paired with forecasted pond water levels. Annual drawdown targets were subsequently established which provided more certainty in scheduling of annual treatment operations

Mar 2, 2022