Search Documents

By Satyam Tiwari, Sarat Kumar Das

Tailings from mines and industries impose danger to the environment as evidenced by the recent failures of tailing storage dams. The tailings are mostly non-plastic with silt-size particles, but their behavior is largely dependent on the extreme void ratios of the material. Hence, the critical state provides an appropriate perspective in explaining the behavior of these geomaterials. Based on a comprehensive dataset of non-plastic tailings and non-plastic soils, an attempt has been made here to correlate critical state parameters to extreme void ratios and stress parameters. A hybrid algorithm with multi-objective feature selection (MOFS) and extreme learning machine (ELM) was used to establish the correlation and to identify the most influential input parameters. Based on the information from the proposed hybrid algorithm, a comprehensive prediction model is proposed using multi-gene genetic programming (MGGP) algorithm to facilitate quick estimation of critical state parameters. The performance of both models has been assessed using several performance metrics. The results from the study indicate that hybrid MOFS algorithms perform very well in the prediction of critical state line parameters and the identification of influential features. The findings of the study have significant implications for future research on the safe management of tailing storage facilities.

Dec 22, 2023

By Mario SINNAEVE, Olivier LEMAIRE, Gisèle WALMAG, Sébastien FLAMENT

Many hot rolling mills worldwide face nowadays bonding zone fatigue problems before reaching scrap diameter of the work rolls. This phenomenon is nowadays known to occur in reversing roughing mills both in stainless steel and in carbon steel rolling. The phenomenon can be explained through longer rolling campaigns, inadequate backup or work roll maintenance, harder steel grades or increased throughput by reduced amount of passes to achieve the same thickness. In order to help users in optimizing the roll use, we developed a numerical tool to evaluate and optimize roll maintenance. This paper will review the influence of roll geometries on stresses generated at the roll surface but also at the bonding zone. We will also show how roll geometries can decrease contact fatigue damages by modifying crowning and chamfering procedures, shell thickness, material design or campaign length

Oct 1, 2019

By A. Y. Senchenko, Y. V. Kulikov

"In recent decades HPGR technology has proven itself in comminution circuits of mining plants. High technical and economic performance, lower specific energy consumption and reliability of HPGR equipment makes it an efficient alternative to conventional circuits using stage crushing and rod/ball milling, as well as to AG/SAG circuits. However, despite all the advantages of this technology the correct selection of key and auxiliary equipment is very important since errors at testing and design stages may lead to discrediting of the whole concept of HPGR application. There is a great variety of possible circuit configurations using HPGR, e.g. with circulation of edge product, with crushing of the whole discharge and circulation of screen oversize, successive two-stage crushing, etc. Each type of minerals will require its own optimal crushing circuit. In this context the testing methodology for selection of an optimal configuration becomes of prime importance. It is common knowledge that the best simulation of material crushing and softening within a HPGR can be obtained only in the course of a large-scale pilot test. The main approaches applied to this kind of testworks are described in this article. Special aspects of HPGR technology design and industrial operation are revealed as well. Some operational issues of HPGR equipment and of circuit as a whole were detected. They are related to regions specifics, plants location, and other factors. Process solutions proposed to deal with these issues are also indicated in the article. INTRODUCTIONDesign and construction of the processing plants involving High Pressure Grinding Rolls (HPGR) technology becomes more and more common in mining as this technology has specific technical and economic advantages against the circuits with autogenous/semiautogenous mills (AG/SAG) and other circuits. The main advantage of the technology is low energy consumption and low operation costs respectively. The presence of microcracks and increased content of fine size fractions in the crushed product contribute to reduction of energy required for further ball grinding. Besides, HPGR technology applies a special wear resistant liner that enables significant reduction of operation costs of grinding media and liner comparing with AG/SAG circuits."

Jan 1, 2016

By W. B. Gogarty

With the use of polymer solutions in secondary recovery operations, the need has developed to understand the mobility control mechanism. This study investigated mobility control by considering both permeability and rheological effects. Experiments used a high molecular weight, partially hydrolyzed polyacrylamide polymer. Flow studies took place in reservoir and Berea cores having zero oil saturation. Effective size of the polymer flow unit was inferred from Nuclepore filter tests. Clay studies indicated the particle size capable of decreasing the core permeability. Flushed permeabilities measured the approximate core permeabilities with flowing polymer solutions. These permeabilities were considerably lower than original values. With mobility data and the flushed permeability, maximum effective viscosities were determined for polymer solution flow in a core. Effective viscosities showed that rheological properties play an important part in mobility control with polymer solutions. The study showed that permeabilities decrease and stabilize with polymer flow. At the lower permeabilities, high shear rates exist in the cores. Because of the pseudoplastic character of the polymer solution, the high shear rates caused low effective viscosities. This condition pointed to the inefficient use of the potentially high viscosity of the polymer solution at low shear rates. INTRODUCTION In the oil industry, a great deal of interest is being shown in the use of polymer solutions for secondary recovery and a number of polymer floods are being performed in the United States.1 Some of these floods have become commercial while others have been reported as failures. A number of floods are still in progress and remain to be evaluated. With the advent of polymer flooding, the need developed to understand the mobility control mechanism in porous media. Rheologically, the polymer solutions behave as pseudoplastic fluids. Investigators have studied the rheology for this type of non-Newtonian fluid in porous media?-6 Results have also been reported on the ability of polymer solutions to decrease mobility.7-10 Some investigators indicated that polymer solutions show a different rheological behavior in cores than on the viscometer.7,8 This study is representative of an initiatory investigation on mobility control with polymer solutions. Some effects are considered on a qualitative basis. Mobility control is considered from the standpoint of both permeability and rheology and, to the extent possible, permeability and rheological effects are considered separately. Results show that mobility control occurs from a reduced permeability caused by polymer retention and an effective viscosity determined by the average shear rate in the core. In this respect, rheological behavior is as important in mobility control as permeability. PROCEDURES A high molecular weight, partially hydrolyzed, polyacrylamide polymer was used in the investigation. Solutions of various concentrations were made with this polymer in different types of water. Some solutions used distilled water and others used tap water. The tap water contained approximately 500 ppm dissolved solids. As used in this paper, concentrations in ppm refer to parts by weight solute to one million parts by weight of solvent. In the tap water, calcium and magnesium accounted for from 60 to 80 ppm of the solids, the remainder being mostly sodium chloride. All solutions contained a bactericide, and anti-oxidants and antiprecipitants were added to the tap water. Capillary and concentric-cylinder* viscometers determined the rheological properties of solutions. The capillary viscometer is described elsewhere.6 Berea and reservoir sandstone were used as core materials for this investigation. Cores were 1 in. in diameter by approximately 2 to 3 in. long. Prior to mounting, the Berea cores were heat-treated for 3 hours at 850F. This treatment decreased the water-sensitivity of the clays in the cores. The reservoir cores were cleaned with solvent and

By Anton Gronningsater

AS we know, Sir Henry Bessemer introduced Bessemer converting in the steel industry about 1855. It was not until twenty years later that the principles were adopted by non-ferrous metallurgists. In 1880, Manés first produced blister copper from matte in a converter, a very important forward step in copper metallurgy. For thirty years, up to about 1910, bessemerizing of copper matte was carried out in the acid-lined converter. It is not necessary here to enumerate all the shortcomings of that operation, one of which was that it strictly limited the grade of matte that could be treated; a 35 per cent matte was low in those days. From the early days of copper converting, many and repeated attempts were made to use a basic converter lining, and the older metallurgists will remember the numerous reports and discussions in connection with such experiments. These make interesting reading. I quote from a book published in 1900: ?'The siliceous lining is as much a part of the process of copper converting as magnesia lining is in the basic bessemer treatment of phosphoric iron, and it is suicidal to attempt any other kind of lining, either water-jacketed or basic.' "Even if the silica could be introduced in this way (through the tuyeres), it would still produce another trouble in the converter. The small particles of silica, being cold, would combine very imperfectly with the iron oxide and produce granulated and pasty slags, which could not be skimmed or poured out of the vessel".

Jan 1, 1942

By Mark R. Svinkin

"Construction equipment and operations usually produce soil and structural vibrations which may harmfully affect various structures and also the content of buildings and houses. The level of structural vibrations depends on a number of factors such as characterized sources of vibrations, soil conditions, and susceptibility of structures. There are certain knowledge and experience for managing the effects of construction vibrations which require implementation of condition survey of structures, information on construction dynamic sources and soil conditions at a site, evaluation of possible vibration effects on structure, calculation of ground vibrations before construction, use mitigation measures to decrease vibrations, and a choice of appropriate vibration limits. The paper presents the application of known concepts for assessment of vibration effects on structures from bridge constructions.INTRODUCTIONVibrations producing by construction activities such as pile driving, dynamic compaction of loose soils, demolition work, heavy construction equipment and trucks can affect adjacent and remote structures. Vibration effects on structures, sensitive devices and processes may create significant practical problems. Legal actions are often required for solutions of vibration consequences. The level of construction vibrations depends on dynamic sources, soil conditions at a site in particularly availability of soils with settlement potential, distances from the sources, parameters of waves propagating at a site and susceptibility rating of adjacent and remote structures. It is likely that intolerable structural vibrations from direct vibration effects of impact pile driving and resonant floor vibrations from vibratory pile driving may be induced in adjacent structures to construction sites.Foundation settlements resulting from soil vibrations in loose soils usually occur in the proximity of dynamic sources, but it is important that dynamic settlement may happen at various distances from the source. There are such examples. First, Kaminetzky (1991) mentioned a case history of building settlements developed at a distance of about 305 m (1000 ft) away from a pile driving site. Foundations of the buildings were underpinned on piles down to the tip elevation of the new driven piles to prevent building settlements. Second, Lacy and Gould (1985) shows that the peak particle velocity (PPV) of 2.5 mm/s (0.1 in/s) of ground vibrations could trigger dynamic settlements at distances up to 30.5 m (100 ft) from driven piles."

Jan 1, 2016

By R. Llewellyn

"Wear damage is responsible for very high maintenance costs and significant production losses in the oil sands industry of northern Alberta.It affects all areas of operations and involves a panoply of wear mechanisms from low stress sliding abrasion at extremely frigid temperatures during winter mining, to elevated temperature erosion/corrosion in processes where bitumen is converted to lighter hydrocarbon products.There is no universal panacea to defend against such diverse attack and a wide selection of resistant materials and systems is employed. These range from relatively soft rubbers which rely on their elastic properties for their protective capability, to some of the hardest ceramics and cermets which are currently available commercially.Details are presented of the characteristics and forms of the variety of wear materials being used and how they relate to the requirements of their areas of application. The review focuses on the practices followed at Syncrude Canada Ltd., which is the larger of the two commercial oil sands plants."

Jan 1, 1997

Sishen uses a state-of-the-art tracking system to track material from its position in blast blocks through various stockpiles and crushers. Qualities are blended directly to the crusher as opposed to blending from stockpiles. This poses an interesting challenge to the planning department to simulate these conditions. The software used in these simulations are Whittle 4X and Maximiser for long-term planning, Xpac for medium-term planning and Mine Works Planner for short-term planning. Geological models and mine design layouts utilise Surpac. Sishen introduced Xpac a number of years ago; the system has developed and changed over the years. With the Sishen Expansion Project (SEP), which aims to utilise low-grade material, major changes to the planning process have to occur. SEP requires that the mine have two different plants, which utilise two different ROM feeds and have different beneficiation curves. Xpac is used to produce a rolling 18-month plan, which is as close to actual operations as possible. In order to do this, the simulations have to take into account the plants beneficiation curves, stockpile movements, hauling distance and equipment needs. On top of this, the schedule has to continually consider specifications for Fe and the contaminants. Plant yields also have to be kept within a certain bandwidth. Xpac is used to simulate the above parameters, as well as generate the raw data required to produce a mine budget. The paper will also show how the 18-month planning process and subsequent planning processes are measured and aligned. Xpac has proved to be an excellent tool to achieve these goals.

Jan 1, 2005

By Nicolas Moscoso, Gerald Verbeek, Marcel Bielefeld, Rob van Dorp

Upon recently, most offshore foundations were based on a number of driven piles that were installed with an impact hammer. With the increase in offshore windfarms two major developments have occurred: the shift from jackets to monopiles, leading to increase of the diameter of the foundation piles, and a shift from impact hammers to vibro hammers. As the use of vibratory hammers is becoming more and more common practice, the need for accurate vibro-driving simulation software has increased, which requires that the soil modelling is enhanced to address soil fatigue during pile driving and to predict reliably the soil behavior and resistance during pile driving. In addition pile driving monitoring, which is routine for piles driven with an impact hammer, needs to become common practice. This paper addresses advances in soil modelling that allows more accurate pile driving simulation as well as the application of Vibro Driving Analysis (VDA) or Monitoring (VDM) to validate the simulation results. This is illustrated by a case study of the test pile for the Delft Offshore Turbine project, a 28 m long monopile with a diameter of 4 m that was driven 15 m into dense sand layers using a vibro hammer. After some 6 months the pile was extracted, and pile driving simulations and VDA were done both for the installation and extraction phase. 1. INTRODUCTION At the end of 2017, the total worldwide offshore wind power capacity was 18.8 GW [1]. The vast majority of offshore wind farms are currently in Northern Europe, which together account for over two thirds of the total offshore wind power installed worldwide, followed by East Asia, while developments in North America are still in very early stages.

Jan 1, 2019

By I. Y. Motovilov, S. A. Telkov, M. B. Barmenshinova, Z. S. Abisheva

As a rule, removing waste rock at the beginning of the process improves the conditions for the flotation of minerals, and also reduces the operating costs of crushing, grinding and flotation. Lead-zinc ores in the Shalkiya deposit of the Republic of Kazakhstan are classified as difficult for enrichment, but taking into account their significant reserves, they are one of the main potential ores for the production of lead and zinc. Under industrial conditions, for processing ores of the Shalkiya deposit, a selective flotation concentration scheme with the production of lead and zinc concentrates is recommended. However, according to the recommended scheme, it is not possible to obtain high-quality concentrates of lead and zinc, with high metal recovery. The paper presents the results of studies of preliminary gravitational enrichment of lead-zinc ore in the Shalkiya deposit. Based on the fractional analysis for the particle size range of -40+8 mm, Henri- Reingard enrichment curves were constructed, separation density (2730 kg /m3) was established to isolate the light fraction with the lowest possible lead and zinc content, and gravity enrichment indices (0.7-0.71) were determined. It was found out that when using gravitational enrichment of the original large-sized ore in the Shalkiya deposit, tails are released at the beginning of the technological process with a yield of up to 20% with the extraction of silica up to 30%, calcite up to 11% and carbonaceous matter up to 12%. As a result of the studies, it was found that the beneficiation of crushed lump ore could be conducted in heavy suspensions. One of the positive aspects of the use of gravitational enrichment is the reduction of energy costs for grinding the heavy fraction, which was experimentally proved in this article. Keywords: Lead-zinc ores, Shalkiya deposit, fractional analysis, gravitational enrichment, floating fraction, sunken fraction, separation density

Jan 1, 2020

By O. A. Carson

Introduction Although the equilibrium conditions of the copper-tin alloys have been the subject of a ?great amount of research, the equilibrium diagram is still in doubt. The first systematic investigation of the series was made in 1894 by Le Chatelier, who published a freezing-point curve. In 1895, Roberts-Austen and Stansfield published the complete liquidus and partial solidus curves, which they modified somewhat in 1897. Their liquidus as given in 1897 is essentially that accepted today (Figure 3). Haycock and Neville also published a liquid us curve in 1897. In 1898, William Campbell published a series of micrographs showing the changes in microstructure which accompanied the thermal changes of Stansfield? s diagram. The classic work on the bronze series was published by Heycock and Neville in 1903. Their diagram was based on both thermal and microscopic evidence, and is the first for this series of alloys which can be considered nearly complete. Further, it was the first bronze diagram in which any attempt was made to apply the phase rule in the interpretation of the thermal and microscopic results. That portion of Heycock and Neville's diagram covered by the present work is reproduced in Figure 7.

Jan 1, 1929

By Reinhardt Thiessen

Views and conceptions of the origin, composition, and general nature of coal differ so widely that to determine the real extent of actual knowledge is no easy matter. The chemist finds difficulty in attacking the chemical problems and the engineer lacks a broad chemical basis for the study of his problems. Thus the economical and efficient utilization of coal in the industries suffers from a lack of knowledge of the composition of coal itself. Most scientists interested in this matter, as has been brought out in discussions during the recent investigation of coal problems, appear to have only a vague idea of the components of coal and their origin. Some are even in doubt as to whether substances derived from the wood and resins of plants form a part of coal; and few seem to have more than the dimmest idea of what are the components of coal, the condition in which these now exist, and the transformations that they haye undergone. Although during the paiilt century or more many co.rrect observations have been made and recorded, these were falsely or inadequately interpreted, so that many of the interpretations rendered are contradictory. As a result there has been great confusion. Many of the observations made in the past, although accurate and correct, could not be explained, because the principles involved in a correct solution of the problem were not then known. For example, Parkinson, Hutton, Petzhold, Guembel, and others made valuable discoveries regarding the processes by which plant substances are transformed into coal, but as the principles involved are those of colloidal chemistry, a science not known to the scientific world of that time, the observed facts could not be interpreted and the solution of the whole problem was blocked. The explanation of the true meaning of the alternating bright and dull bands so familiar in all ordinary bituminous coals afforCls another example. This banding has been observed and recorded from the earliest times, and has led to the forming of many false theories. Some gAologists, for example, have endeavored to explain the bands as due to alternating climatic conditions during the coal-forming period. Had the geologists known the true nature of coal they could not have made this mistake nor many others made in the past. To fill in a few of these gaps and to clarify some of the existing confusion is the aim of this paper. The immediate cause that led the author to investigate further the composition of coal and the origin and structure of its constituents was that when an attempt was made to discover the meaning of the coking and noncoking properties of coal a more exact knowledge of the nature of coal was required than was then available.

Jan 1, 1920

By G Byrne

Long-term water management is typically ignored in mine closure planning. A review of 73 mine closure plans dating from 2007 to 2013 shows that, on average, relinquishment is proposed to be achieved in 11 years. A separate review of 57 mines in actual closure shows that only five have so far achieved relinquishment with an average closure period of 14 years after production cessation. The remaining 91 per cent of sites in closure have an average closure duration to date of 21 years - and still going.A common issue among those sites in closure is water management, with a further common issue being acid and metaliferous drainage (AMD). Of the closure plans that were reviewed only one site had allowance for long-term (>50 years) of water treatment. Of the sites in actual closure 25 per cent have reported that they expect such long-term water treatment, with many acknowledging that in perpetuity treatment is probable.Clearly there is a gap between what is being allowed in closure plans and the reality of closure. There are a number of factors leading to the optimism of the closure plans, including unrealistic assumptions, pressures to reduce closure cost provisions and the technical complexity of many AMD issues.Long-term water management is a reality that needs to be acknowledged and addressed. If addressed early in the mine life cycle the impacts for mining companies can be reduced.CITATION:Byrne, G, 2013. Long-term water management - the forgotten legacy of mine closure, in Proceedings Water in Mining 2013 , pp 163-168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By P. Zhang

Phosphate mining in Florida generates approximately 100,000 tons/day of phosphatic clays (slime). This waste slime not only creates one of the most difficult disposal problems in the mining industry, but also causes tremendous loss of P2O5. About 20-30% of the phosphate mined end up in phosphatic clays. Recovering the phosphate from this waste is difficult for two main reasons: 1) the slime is extremely fine in size, and 2) clay minerals account for almost half of the material. A half dozen dispersants were evaluated for keeping the clay minerals suspended for subsequent separation from non-clay minerals by either settling or cycloning. The separation efficiency and economics are discussed.

Jan 1, 1998

The workshop on "Cyanide Effluents from Mineral Processing' was held on February 2-3, 1982, at the U.S. Bureau of Mines, Salt Lake City Research Center, Salt Lake City, Utah. The workshop was sponsored by the minerals industry, supporting industries, the National Science Foundation, and the U.S. Bureau of Mines through the Utah Mining and Mineral Resources Research Institute, College of Mines, University of Utah Prior to the workshop, a Working Paper was prepared and delivered to the participants. This paper was used as a guide during panel discussions and forms the basis for this proceedings document. The workshop focused on use of cyanide as it relates to the gold and silver mining industry and the froth flotation processes employed by mineral mining companies. Its intent was to discuss "state of the art" technology and provide information pertinent to cyanide use in the minerals industry. No attempt was made to advocate regulatory limits or set policy governing the use of cyanide. The principal topics of discussion included- (1) the chemistry and use of cyanides; (2) control and treatment of cyanide mining wastes; (3) toxicity of mining wastes; (4) fate of cyanide in the environment; and (5) the analytical chemistry of cyanide.

Jan 1, 1983

By Mi, Dong Liang, Jingyuan Bai, Victor Zhou, Xujun

Squirrel cage induction motors are the mostly used motors at present. Currently, the rotors of the squirrel cage induction motors are produced by aluminum die casting technique with the advantages of low cost of rotors. It is well known that the copper’s electrical conductivity is around 40% higher than that of aluminum. If copper is used to replace the current widely used aluminum in rotors, the total loss of motors will be reduced, hence increasing the overall motor efficiency. Copper rotors can be used to produce high efficiency and even super premium efficiency motors without enlarge the motor frame size. Considering the huge quantity of motors, the die casting process is the best solution to produce copper rotor with economic cost. Because of the characteristics of copper, it is difficult to produce copper rotors by casting similar to that done in aluminum rotors. In order to improve the die casting quality of copper rotor, a new tooling structure was developed and the casting process of copper rotor was simulated and analyzed by Any-casting software. The filling process, solidification process, inner gas distribution and residual melt modulus were analyzed. It was found that the design of symmetrical runner and inner runner on both sides was helpful to reduce the impact of molten copper to the cavity surface during the filling process. The use of Slag traps array can reduce die casting defects inside the end rings. That will be helpful to improve the rotor quality. INTRODUCTION Squirrel-cage AC induction motors are most widely used in the world. In 2017, the total installed capacity of AC motors in China has reached more than 1.2 billion kW, and the annual power consumption accounts for about 60% of the total national electricity consumption. To improve the efficiency of squirrel-cage motor will be helpful to energy conservation and environment protection. There are several ways to improve efficiency of induction motors, using copper rotor is one of the most effective solutions. It is well known that the copper’s electrical conductivity is around 40% higher than that of aluminum. If copper is used to replace the current widely used aluminum in rotors, the total loss of motors will be reduced, hence increasing the overall motor efficiency. Copper rotors can be used to produce high efficiency and even super premium efficiency motors without enlarge the motor frame size.

Jan 1, 2019

By G. Akdogan, P. Mutimutema, M. Tadie

The South African gold mining industry has a legacy of abundant tailings dams, which have attracted the attention of investors because of their potential as a cheaper secondary gold resource. In this we investigate study gold recovery from a refractory calcine tailings dam. Bulk mineralogy of the tailings silicates and iron oxides to be the most abundant phases. Scanning Electron Microscopy (SEM) showed gold to exist in submicrometre and micrometre sizes, as free gold, and associated with arsenic, sulphur, and silicates e.g. quartz and talc. Gold recovery by direct cyanidation was low at 17.3%. Mechanical (ultra fine grinding P80 -16μm) and chemical (alkaline, NaOH) pre-treatment and microwave roasting and microwave-assisted cyanide leaching were investigated to increase gold recoveries. Ultrafine grinding was the most effective, producing recoveries of 66.5%. NaOH pre-leaching of ultrafine milled material increased recovery to 71.5%. Alkaline pre-leaching overall increased recoveries for non-pretreated material, making this process the most preferred because it is less costly than ultrafine grinding. Microwave roasting and microwave-assisted leaching did not achieve higher recoveries than alkaline pre-treatment or fine grinding. The investigation highlights and confirms that chemical treatment with NaOH is a powerful tool for gold extraction from refractory tailings.

Oct 1, 2022

By P Dean, M Elmouttie

Radar monitors are now widely used in surface mining for monitoring slope deformations and predicting failure events. Their introduction has facilitated better management of risk associated with slope failure during mining and therefore protection of personnel and equipment. However, a wellrecognised problem is that radar monitors only measure deformation directed towards the detector (line-of-sight bias). This bias can lead to misinterpretation of deformation size, rate and failure mechanism, and therefore miscalculation of failure volume, which can significantly impact safety and productivity. This paper presents recently completed research and field trials into the feasibility of using low cost vision systems to mitigate this issue. It has been demonstrated that by integrating a computer vision system with an existing slope monitor, high precision tracking of features in the field of view can be performed. Combined with assumptions on the deformation characteristics, the true 3D deformation vector can be estimated. The applicability of using this technique for monitoring iron ore mine slopes is discussed.

Nov 8, 2021

By Garrett May

We present a periodic technique for measuring the thermal conductivity of thin, disk-shaped samples. In samples of this type, temperature measurements must be made across the sample faces and are therefore subject to large error due to the interface resistance between the temperature sensor and the sample. The technique uses measurements of the amplitude and phase of the periodic temperature across both a reference sample and the unknown material at several different frequencies. Modeling of the heat flow in the sample allows the simultaneous determination of the thermal parameters of the sample as well as the interface resistance. The technique is demonstrated on nanocomposite samples less than 1.0 mm thick.

Jan 1, 2008

By M. Deutsch

A common casualty of modern open pit mine optimization is the assurance that the resulting design is actually achievable. Optimized mine plans that consider value and a bare minimum of precedence constraints do not, in general, translate into practical, operational mine designs that can really be used in the field. Ultimate pits may come to a sharp point at the bottom. Schedules may require taking small parcels of material from many disparate areas of the pit in a single period. And grade control polygons may be ragged, narrow, and not minable with realistic equipment. In this paper all of these problems are addressed by encoding these three fundamental open pit mine optimization problems as maximum satisfiability problems. Maximum satisfiability provides a useful framework for problems that are non-linear and may guarantee the optimality that metaheuristics cannot. INTRODUCTION Open pit mines are large and complicated operations, which require significant initial and ongoing investment. A single mine may employ hundreds or thousands of people and creates substantial benefits for both the surrounding and global communities. Planning an operation of this magnitude requires a lot of effort and cannot be done optimally by hand. Mining engineers today rely on many techniques from operations research to guide decision making, and to maximize the value of the mine. Techniques including linear programming, metaheuristics, and network algorithms are all used to solve different problems throughout mine design and optimization. However, techniques based on Boolean satisfiability, including the optimization extension of maximum satisfiability, have not seen much use in mining despite being used in many other fields including electronics design, scheduling, and artificial intelligence. We claim that maximum satisfiability is a useful and meaningful way of expressing and solving optimization problems in mine planning. However, this technique does not come without challenges; the problem is NP-hard, and modern techniques for solving these problems can struggle with the number of variables and clauses that a typical mining problem requires. Also, some of the constraints that mining must contend with do not fit nicely into the satisfiability paradigm. Despite these challenges, we believe that maximum satisfiability provides a useful framework for considering operational constraints and expressing some problems that other techniques can't easily express. Maximum satisfiability can be solved exactly, yielding the true optimal answer which metaheuristics cannot guarantee. In this paper we show the applicability of maximum satisfiability to mining by specifying three fundamental problems in open pit mine optimization. We show how these fundamental problems can be formulated and how they can be extended within the framework of maximum satisfiability. For the remainder of the paper we first give a brief background on common elements between the three problems and an introduction to satisfiability. Then we tackle the three problems; the Ultimate Pit Problem, the Block Scheduling Problem, and the Grade Control Polygon Problem. In the Ultimate Pit Problem we specifically show how to extend the problem to support a minimum mining width – a coveted result for many mining engineers. We then discuss some of the complexities and shortcomings of this framework and possible research directions.

Jan 1, 2019