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Scenario reduction is designed for selecting a representative subset of geostatistical simulations out of a much larger set. Three steps are involved: measuring the dissimilarity between two simulations; finding a metric to measure the distance between any subset of k simulations and the full set of N simulations; and finding an efficient algorithm for selecting the subset that minimizes the metric. This paper focuses on the third question. We show that genetic algorithms are an efficient way of approaching the minimum when the population of subsets to be sampled is large. Two case studies based on the Walker Lake data-set are presented: firstly choosing k=4 simulations out of a total of 100, and secondly choosing 20 out of the same 100 simulations. In the first case it was possible to compute all possible combinations exhaustively and hence to demonstrate that the algorithm converges to the true minimum. This was not possible in the second case. Instead we demonstrate that it outperforms the random draw algorithm used in earlier work. A procedure for tracking individual selections during the iterative procedure was developed. This allows us to measure the evolution in the percentage of progeny resulting from crossing-over and from mutation that survived in the next generation. It gives valuable insight into how to choose the parameter values in the algorithm. Another key finding is that there is a trade-off between the number of individuals per generation and the number of generations required for the algorithm to converge.

Jan 1, 2014

Three complete connector assemblies and six separate contacts were submitted to a series of tests to establish the connectors permissibility and compliance with U. S. Bureau of Mines research Contract #H 0110423 D.C. portion. Test Procedure TPC-0118 was coordinated, and the test plan approved by the Bureau as fully complying with the intent of the contract for the direct current connectors. The components and connector assemblies have been demonstrated in testing that they meet or exceed all the requirements of the test procedure.

Jan 1, 1974

By J. J. Forbes

The activities of the Bureau of Mines include the development and testing of self-contained oxygen breathing apparatus and other devices for respiratory protection, the development and tasting of devices for detecting dangerous or noxious mine atmospheres, and the training of men in the mineral industries in the use and care of this equipment to enable them to render effective service in mine rescue and recovery operations following mine fires and explosions, or under other conditions where irrespirable gases may be found in mines or mining plants. The first use of self-contained oxygen breathing apparatus for com- bating mine fires and explosions in the United States dates back about 30 years. Previous to that time, exploration for any distance ahead of fresh air was virtually impossible without great risk to life; moreover, the men called upon to render service at mine disasters were not well-versed in the properties and physiological effects of gases likely to be encountered. It was also impossible to work ahead of fresh air to restore ventilation, and if many stoppings were blown out by an explosion, air had to be introduced into whole areas or sections at once without knowledge of the conditions ahead; moving an explosive mixture of methane and air over live fire had to

Jan 1, 1938

By R. C. Ellman

Since successful industrial lignite-burning equipment was developed in 1925, the commercial use of lignite as a fuel for power plants has increased. It has proved an entirely satisfactory fuel for generating power and can be burned efficiently by various methods.4/ Equipment to fire pulverized lignite was installed and used successfully at the Trinidad Station of the Texas Power & Light Co. as early as 1926. The lignite was predried in steam-heated grid driers before pulverizing.5/ This method of firing was used later in the Comal Station of the San Antonio Public Service Commission.6/ Both stations, however, have since been converted to use other fuels. Units for pulverizing and drying lignite are relatively new in the lignite-consuming region of North Dakota. The air which sweeps the pulverizer and transports the pulverized product to the burners is preheated to dry the lignite during pulverization. The first unit was installed in 1948 in one of the two boiler units of the Crookston Station, Otter Tail Power Co., Crookston, Minn.7/ In 1951 the 30,000-kw. W. J. Neal Station, Central Power Electric Cooperative, Inc., Voltaire, N. Oak., was designed and constructed for firing pulverized lignite exclusively. It is the largest lignite-fired, power-generating station in North Dakota. The 44,000-kw. Lewis and Clark Station of the Montana-Dakota Utilities Co., Sidney, Mont., is fired by a similar pulverizing system. Operation of this plant was begun in October 1958. At Fergus Falls, Minn., the 53,500-kw. Hoot Lake Station of the Otter Tail Power Co., also using a pulverized lignite-firing system, began operating in September 1959.

Jan 1, 1961

By R. D. Begley

This paper will present detailed design drawings of a flexible single floor residential superstructure proposed for both longwall and room and pillar mining conditions. All efforts were made to provide an immediately available economical alter- native for future home builders on subsidence prone land. Based on this fact, a basement was not included in the design because additional costs and measures would be required to minimize cracking and leakage. A cost comparison with a traditional superstructure demonstrated that this would be a cost effective alternative. The criteria used to determine the design of the residential structure was as follows: 1. The appearance should not be different then a typical three bedroom residence; 2. Only commercially available devices and present architectural and engineering technology should be used to achieve the required "flexibility" of the super- structure; 3. The structure as completed would be capable of resisting a predetermined amount of vertical and horizontal movement; and 4. If the structure was to experience stresses beyond its capabilities, it could be easily removed from the foundation and releveled.

Jan 1, 1986

By M. Nyoka

Historically bauxite-based refractories have been used in applications where andalusite-based refractories could work. Bauxite-based refractories were chosen over andalusite-based refractories mainly because of the availability of low-cost Chinese bauxite and also because many furnaces were designed by international companies that cannot easily access high-quality products. Currently, the availability of low-cost bauxite is under threat as a result of high export duties and tariffs as well as restrictions on the amount of material that China allows to be exported. South Africa is a major producer of andalusite, and this guarantees stability with respect to both availability and price. Refractories based on andalusite have an added economic advantage over bauxite-based refractories in that unlike bauxite, which requires high-temperature calcination before use, andalusite is used in its raw state. This paper constitutes a literature study of the merits, both technical and economic, of using refractories based on andalusite compared to bauxite-based refractories. Keywords bauxite, andalusite, refractory, furnaces, calcination.

Aug 1, 2013

By Richard Mainiero, Donald A. Hurd, James H. Rowland

In previous conferences the authors have reported on toxic fumes generated by the detonation of ANFO. The research reported here extends the earlier work to include an emulsion blasting agent and ANFO/emulsion blends. Explosive mixtures were shot in 4-inch Schedule 80 steel pipe in a chamber in the experimental mine at the Pittsburgh Research Laboratory (PRL). Following each shot, the fumes in the chamber were analyzed using on-line instrumentation. A major goal of the research was to gain a better understanding of the factors that lead to the generation of toxic fumes in blasting operations. Earlier studies have suggested that the high nitrogen dioxide and nitric oxide concentrations in product clouds might be the result of the poor confinement provided by relatively weak ground strata or the exposure of the explosive to ground water prior to shooting the shot. Various mixtures of ANFO and emulsion were detonated in schedule 80 steel pipe and galvanized sheet metal pipe to evaluate the effect of confinement. Explosive mixtures were also allowed to soak in water for less than one day, one week, one month, and two months to determine which explosive mixtures would be degraded and observe what effect this degradation had on fume production. Results indicated that the production of nitrogen dioxide increased with low confinement of the detonating explosive and with exposure of the explosive to water.

By F. Halverson

"The theory of flocculation usually is in a state of flux, involves many diverse phenomena, and is complex and sometimes contradictory in details. Instead of attempting a general discourse, I shall discuss selected observations made at our Stamford Laboratories, which impinge on theoretical aspects in two somewhat distinct areas of flocculation. Since some of you many not be familiar with flocculation, and :.n order that we all attach the same meaning to the jargon used, I first would like to review briefly a generalized picture of what goes on.Assume we have a suspension of particles in water, with a distribution in the sizes of particles. The surfaces of the particles interact to some extent with the water--· tending to alter the extent of hydration, may generate some ion exchange, all being somewhat variable with time--developing a surface condition which is very complex in details. We refer to this suspension as the ""substrate.""In the usual situation, if the suspension is allowed to stand quietly, the large particles settle out first, with somewhat smaller particles settling more slowly, and then there is a portion of very fine material which takes a long time or doesn't settle out at all. This resistance to settling t~ the very fine particles results from many factors, but all relate back to the size and density of the particles, to their surface properties, and to the other components in the aqueous suspending medium."

Jan 1, 1978

By H. H. Wade, N. F. Schulz

The large quantities of iron-bearing materials, including taconite, semi-taconite,* and other low-grade ferruginous materials occurring in Minnesota and elsewhere, constitute an important potential source of iron. Satisfactory grade and recovery of iron ore concentrate cannot ordinarily be obtained from these ferruginous materials by simple methods of beneficiation. Iron is distinctive in that the free metal and two of its oxides [magnetite (Fe2O3) and maghemite (gamma-Fe2O3) ] are strongly ferromagnetic. The successful magnetic separation of natural magnetite from taconite has already been established on a commercial scale. The iron in semi-taconite, however, occurs largely as goethite (Fe2O3-H4O) and hematite (Fe2O3) which do not respond to ordinary magnetic separation methods. Magnetic roasting converts these iron oxides to magnetite, which can, after liberation, be magnetically concentrated. MAGNETIC ROASTING Hematite undergoes a stepwise reduction when exposed at moderately elevated temperatures to a reducing atmosphere containing hydrogen or carbon monoxide: Fe2O3? Fe3O4 ? FeO ? Fe Since the desirable product in magnetic roasting is Fe3O4, the conversion is halted after the first stage by controlling the reduction potential of the gas mixture with water vapor or carbon dioxide. The reducing gas mixture must be such that the oxygen partial pressure at the solid-gas reaction interface will be maintained intermediately between the oxygen partial pressures in equilibrium with Fe2O3 and Fe3O4 at the prevailing temperature. Because of the rapid increase in decomposition pressure of Fe3O4 with increase in temperature, the practical upper limit of useful reaction temperature is about 1400°F, above which over-reduction usually occurs in atmospheres containing hydrogen or carbon monoxide. On the other hand, useful reaction rates usually occur only above 800°F. Goethite reacts similarly except that the combined water probably has to be driven off thermally before the reduction to magnetite occurs. Iron carbonate must also be decomposed thermally to an oxide before conversion to magnetite. Iron silicates are apparently not amenable to magnetic roasting. The rate of penetration of the reaction toward the interior of a given ore fragment is dependent on the chemical composition and physical structure of the solid. Most ore fragments tested here reduced satisfactorily to 1/4-in. depth in less than 14 min at 1200°F. Some very dense fragments, however, were reduced to less than 1/32-in. depth under the same conditions. Determination of the optimum temperature, gas composition, ore fragment size, or time of exposure

Jan 1, 1961

By Sanford J. Douglas

This publication describes a study by the Federal Bureau of Mines of devices and methods used for testing and splicing 4,160-volt and 440-volt cables and for providing ground-fault protection for 440-volt circuits, as developed and used by the electrical staff of the Tecumseh coal mine, an open-pit operation at Boonville, Ind. The testing and ground-fault devices described should find ready application in other open-pit mines, and, with suitable modifications for voltages involved, in underground mining. The devices and testing methods are based on sound engineering principles and are time-tested and economically feasible, Four devices are used: A high-voltage tester, and a low-voltage high- current tester, both for testing 4,160-volt cables; a tester for 440-volt cables; and, electronic ground-fault protective device for 440-volt cable circuits. All the cable testers and the grounding device were designed and built at the mine from standard parts. They are inexpensive, dependable, and job tested, An attempt has been made here to describe them in enough detail so that interested persons can assemble duplicate units.

Jan 1, 1960

By Sam Ammermann, William Heasley

"The mining industry is on an ever accelerating path to complete mechanization. As companiesutilize more sophisticated and efficient methods of blasting, a more thorough look should begiven to the pros and cons of mechanized shaft sinking. Historically, Vertical Shaft SinkingMachines (VSSM) have been capital intensive, making it hard to enter lowest bidder marketssuch as the United States. As advances in safety and technology have occurred, VSSM methodsare becoming increasingly common in many countries outside the United States. Decreasedcapital requirements, a greater amount of competition within the VSSM market along withgreatly improved safety practices, have made it more competitive with traditional drill and blast(D&B) methods. However, VSSM technology has yet to be embraced by the United States. Alarge culture shift will have to occur before VSSM technology will become common in theUnited States. The history, and advent, of raised boring machines will be discussed and how itrelates to the current development of VSSM technology. The researchers will analyze the uniquerisks of D&B methods and how they compare with the unique risks of VSSM technology. Theresearchers will put an emphasis on risks directly affecting the safety of personnel working onthe shaft sinking operation. Many of these risks are identified by contracting companies withregards to geology, relative location of resources and the chosen shaft sinking method. Theresearchers will discuss specific risks a given shaft sinking company will want to consider whenchoosing between D&B and VSSM methods."

Jan 1, 2016

By Dina M. Aloi

In today?s evolving and globalized world, mining companies are being pressured to move beyond compliance towards long-term sustainability and sustainable development. Companies are expected to ?engage? communities without a clear understanding of ?how? to do this or to what end. This move, away from compliance, develops more of a focus on ?Community? Social Responsibility and sustainability. This shift leads to the development of world-class projects that provide sustainable development for people, reduce the incidence of costly delays, and promote good global citizenship for companies. The process of ?engaging? communities in mining project design and development leads to a stronger license to operate, and a reduction in social and political risk. To create this mutually beneficial relationship between communities and companies, communities must be ?engaged? in the project development and risk assessment processes as early as possible, preferably during the exploration or the concept phases. How to create this ?engagement? and manage this risk will be discussed.

May 1, 2007

Energy Dissipation in Long-Distance Slurry Pipelines

Sep 13, 2010

By S. Sinha, S. Ganguly

"In an opencast mine explosives are used for fragmentation of rock. Inefficient use of explosive energy in an opencast operation produces excessive ground vibration, which is measured by peak particle velocity (PPV). To mitigate ground vibration, it is essential to develop a model to predict PPV. At present empirical models are used. These models are based on only a few input variables, hence they fail to take into account the effects of the myriad factors that cause ground vibration. Due to lack of explicit knowledge about the complex mine blasting system the scope of application of mathematical and statistical modeling techniques is limited. The artificial neural network (ANN) technique is a learning algorithm that can remove some of these limitations and can be applied to predict PPV. In this paper an ANN model is developed for prediction of blast vibration using 248 data records collected from three coal mines with diverse geomining conditions. The correlation coefficient between measured PPV and model output was found to be 0.96 and the average error percentage 11.85. The ANN model output was compared with the output of three empirical models that are widely used for prediction of PPV. The correlation coefficient between the PPV predicted by an empirical model and measured PPV data was 0.63 and the relative error percentage 38.47. This result demonstrates the superiority of the ANN model compared to empirical blast models. By using site-specific structural discontinuities as input the model performance can be further improved. Sensitivity analysis and 3D plotting were used to gain further knowledge about blast-induced ground vibration. IntroductionIn an opencast coal mine explosives are used for fragmentation of coal and overburden. If the explosive energy is not fully utilized it causes blast-induced ground vibration, which may damage nearby structures. Ground vibration is expressed as peak particle velocity (PPV). During different stages of mine planning and operation, it is necessary to use a ground vibration prediction model for blasthole design. Selection of the modelling technique is crucial. Mathematical and statistical modelling techniques have limited application because of the lack of explicit knowledge about the complex mine blasting system. Vogiatzi (2002) highlighted the problem of multicollinearity in case of statistical modeling techniques. Mutalib et al. (2013) stated that mathematical models are unable to capture the nonlinear relationship between several blasting-related parameters due to the complexity of the model input data. However, the difficulty involved in modelling complex blast vibration problems can be removed by adopting an alternative soft computing modelling approach. One of the soft computing techniques is the artificial neural network (ANN). Ragam and Nimaje (2018) developed an ANN model for predicting PPV using six input variables. Kosti et al. (2013) stated that the conventional predictors fail to provide acceptable prediction accuracy. They showed that a neural network model with four mine blast parameters as input could make significantly more accurate on-site predictions. Sayadi et al., (2013), using a database from Teheran Cement Company limestone mines, found that a neural network resulted in maximum accuracy and minimum error. Khandelwal and Singh (2009) developed an ANN model using 150 data records from an Indian coal mine with site-specific rock characteristics and geomining setting. Khandewal and Singh (2007) built a ground vibration prediction model for a magnesite mine using four prediction variables with 20 data records. Kamali and Ataei (2010) predicted PPV in the structure of the Karoun III power plant and dam using an ANN. El Hafiz et al. (2010) evaluated ground vibration predictors using data from a single-station seismograph at a limestone quarry in Egypt."

Feb 1, 2019

By D. F. Machuca-Mory

A change of support model consists of a procedure to change a stationary histogram at a small data scale to represent a larger scale; typically a distribution of sample drill-hole data is changed to represent a chosen selective mining unit (SMU) scale. Most grade variables average arithmetically. Thus, the mean stays the same for different scales, and the variance changes according to well-established theory using average variogram values. The longstanding challenge has been to predict how the shape of the histogram changes. The discrete gaussian model is widely used because it appears reasonable and introduces few artifacts; there are no artificial minimum/maximum values and the target mean and variance are reproduced exactly. The resulting distribution shape, however, is strongly dependent on a multivariate gaussian distribution. The authors generalize the approach by taking advantage of a property of the isofactorial model, which allows one to specify where the random function falls on the spectrum between a low-entropy mosaic model and a maximum-entropy diffusion model. A measure of dissemination (MD) is computed using a ratio of the madogram and the variogram. The change of support algorithm is developed that uses a variable measure of dissemination (VMD) that is easily calculated and fit to data from the deposit. The resulting VMD change of support model is very flexible to represent different mineralization styles encountered in practice; global predictions of recoverable reserves are more accurate and decision-making is improved. A number of real examples are shown to demonstrate the approach.

Jan 1, 2008

Spectrum Resources commenced operations as a public listed mining company in August, 1983, with a variety of precious metal projects in New Zealand. At that time the outlook for most mineral commodities, with the notable exception of precious metals, was decidedly gloomy. Metal prices were depressed and demand forecasts were universally gloomy. Against this background the company reviewed the non-traditional metals sector to try and identify a 'new' metal with an above average demand growth and market value. Lithium, a commodity with exciting new applications in storage batteries and alloys, met both criteria. Annual world consumption of lithium is around 7000 tonnes; current prices are around $NZ40/lb for lithium metal and demand growth is projected at five to seven per cent per annum. Geothermal fluids at Wairakei and elsewhere contain anomalous amounts of lithium and in May, 1984, the Chemistry Division of DSIR was commissioned to carry out a literature survey on the possible recovery of lithium and other minerals from geothermal waters. The survey results were encouraging and the company subsequently negotiated exclusive access rights, for research purposes, to geothermal discharge fluids from the Wairakei and Kawerau geothermal fluids. Most of the subsequent investigations reported here were carried out by Chemistry Division, DSIR, under contract to the company with some assistance from the Industrial Processing Division, DSIR.

Jan 1, 1986

By R. Emmett Hughlett

The Bureau of Mines has developed a statistical approach to the laboratory evaluation of response bias and precision in gas detectors. The techniques described employ a computerized analysis and a new method of data presentation called composite graphing. The underlying theory, its practical application to the data, and the experimental equipment and procedure are described.

Jan 1, 1982

By W. Barnett

The Limpopo Metamorphic Belt is a complex geological terrane with at least three major deformational events. Tectonically juxtaposed lithology, open to isoclinal folding, crosscutting and re-activated shear zones and metamorphic gneisses and schists make pit slope design and maintenance a risky business. Venetia diamond mine?s Cut 3 is planned to reach 360 m by 2011. The difficult rockmass created problems in the original pit and a new more comprehensive slope design was necessary. Nearly 9 km of geotechnical drilling were undertaken to produce a new geological model and provide geotechnical information near the final Cut 3 face. All existing data from the pit were brought together into a database. SRK Consulting were brought into the project to audit the process and provide most of the manpower for the data analysis. Existing failures were back-analysed and the geotechnical domains identified. Analyses of only the southern domains are discussed in this paper. Geotechnical engineers can design slopes at any angle, but it is up to the managers at the mine to decide what risk they are willing to accept in a slope design. Once the issue of risk was discussed and settled in respect of the consequences of failure, each of the main geotechnical domains were analysed to produce a slope design at5% probability of failure with 15% above the first ramp. A risk assessment of the design was then undertaken to determine what risk the design placed on the equipment, personnel and the profitability of the overall mining operation. The risk assessment indicated minimal risk to the operation. One of the main assumptions of the final design is that the pit slopes will be dewatered. A project was immediately put in place to determine a groundwater model for the mine and to thereby determine the best dewatering procedure. However, it should be obvious that it is practically impossible to prevent benches from getting briefly saturated with water during storm conditions. It was therefore necessary to look specifically at supporting the crests of the ramps in the problematic southern domains to guard against the possibility of crest failure during heavy rains. The data available were re-analysed toward this objective. Spiles were recommended as the most cost-effective support system, and a probabilistic approach was used in the design. The final design has a 5% probability of failure, and the analyses indicate a strong sensitivity of the required spile spacing to the strength of the reinforcement material that will eventually be used. The pit slope parameters derived as per the discussion in this paper have just begun to be implemented at Venetia Mine.

Jan 1, 2001

By K. L. Paciorek

The aim of the present study is to determine on a gram per gram basis the toxic products of the thermal oxidative degradations of selected compositions. Four families of materials were investigated under the subject contract namely polyvinyl chloride and neoprene compositions, rigid urethane foams I and woods. Three methods were employed to conduct the thermal oxidative degradations: a sealed system (quiescent environment) I a stagnation burner arrangement (dynamic environment) I and a flow-through apparatus (dynamic I but less severe than stagnation burner conditions). The majority of tests were conducted using the first two systems; only limited experiments were carried out employing the third decomposition procedure. All decomposition was done at temperatures of 370 -4000C I the higher temperature being used in the stagnation burner. It has to be stressed that the nature of the products and the relative product concentration are temperature dependent. Thermogravimetric and differential thermal analyses were performed to supplement and extend the above delineated studies and to explore the feasibility of using these analyses as a method for material differentiation.

Jan 1, 1973

By K. Liu

"In the present work, two-step heat treatments with preheating treatments at different temperatures (175, 250 and 330°C) as the first step followed by the peak precipitation treatment (375°C/48h) as the second step have been performed in Al-Mn-Mg 3004 alloys to study their effects on the formation of dispersoids and evolution of elevated-temperature strength and creep resistance. During the two-step heat treatments, the microhardness is gradually increasing with increasing time until to a plateau after 24 hours when first-treated at 250°C and 330°C while there is a minor decrease with time at 175°C. Results show that both the yield strength and creep resistance at 300°C reach the peak values after the two-step treatment of 250°C/24h+375°C/48h. The formation of dispersoids is greatly related to the type and size of pre-existing Mg2Si precipitated during the preheating treatments, in which that coarsened rod-like ß’-Mg2Si strongly promotes the nucleation of dispersoids while finer needle-like ß’’-Mg2Si has less influence. Under optimized two-step heat treatments and modified alloying elements, the yield strength at 300°C can reach as high as 97 MPa with the minimum creep rate of 2.2×10-9 s-1 at 300°C in Al-Mn-Mg 3004 alloys, enabling them as one promising candidate in lightweight aluminum alloys for elevated-temperature applications.INTRODUCTION Due to the rapid demand from weight-sensitive automotive and aerospace industrials for the light alloys, such as aluminum alloy on the elevated-temperature applications, Al-Mn 3xxx alloys has been developed to obtain the good properties at both room temperature (RT) and elevated temperature, in which the dispersoid-strengthening mechanism plays a significant role (Li & Arnberg, 2003; Li, Muggerud, Olsen & Furu, 2012; Liu & Chen, 2015, 2015). In our previous works (Liu & Chen, 2015, 2015; Liu, Ma & Chen, 2017), the yield strength and creep resistance at 300°C of Al-Mn-Mg 3004 alloy were further improved by modifying the alloying elements, such as Fe and Mo, to optimize the characters of dispersoids, including the size, distribution and the dispersoids free zone (DFZ). For instance, Mo was introduced in aluminum alloy to further improve the volume fraction of dispersoids and reduce the area of DFZ, leading to increasing on both the strength and creep resistance at 300°C (Liu, Ma & Chen, 2017). On the other hand, the mechanical properties became worse at higher Fe content due to its consumption more Mn to form Al6(MnFe) intermetallics, resulting in less available soluted Mn for the precipitation of dispersoids (Liu & Chen, 2015). Therefore, optimizing the characters of dispersoids is always the key to improve the elevated-temperature properties of dispersoid-strengthened aluminum alloys for elevated-temperature applications."

Jan 1, 2017