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By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By D. Komljenovic, V. Kecojevic

Selection of the best possible truck type (model) is of crucial importance for the mine decision-makers. In this paper, authors contribute to the body of knowledge by developing a novel methodology for the selection of mining truck. Both the Coefficient of Technical Level (CTL) and Analytic Hierarchy Process (AHP) methods were used in this study. The CTL represents a mathematical function which takes into consideration the interrelations among the main technical parameters of mining trucks. The authors developed a hierarchical structure where both attribute categories and their importance, i.e. priority or weight in the selection process were determined. For each category, a number of sub-attributes and their priorities were assigned, and a pairwise comparison among them was performed using the AHP method. In the final part of the study, the CTL was integrated into the AHP and represents a holistic approach in the selection of mining trucks. A case study on 180 tonnes truck category offered by five manufacturers was carried out. A sensitivity study of obtained results was also performed indicating a very stable solution. The methodology presented in this paper may be used by mining operators to help in the selection of a specific type when acquiring a new truck. It may also be used by equipment manufacturers to help in analysis of potential benefits of envisaged modifications concerning an existing truck type and/or development of a new type.

Jan 1, 2007

By E. Nickel

"Bi- and multilateral banks as well as export credit agencies in the OECD countries, but also numerous commercial banks, last year committed themselves to compliance with the World Bank’s standards. These environmental and social guidelines, also known as the Safeguard Policies, are the strictest international standards in the area of financing of major investment projects. The Safeguard Policies are procedural and quality guidelines by means of which socially and environmentally relevant impacts can be taken into account in the planning and implementation phase of a project. Objectives of the Bank Safeguard Policies are to ensure that environmental and social issues are evaluated in decision-making, to reduce and manage risk of projects and programs, and to provide a mechanism for consultation and disclosure of information. They are often referred to as the "10+1 Safeguard Policies," since ten of the guidelines address environmentally and socially relevant issues, while one guideline is exclusively concerned with public participation ("Public Disclosure"). In the presentation, the transparency of risk management measures and emergency response plans in pipeline projects will be discussed as an indicator of sustainability. The discussion is to be carried out on the basis of the results of an evaluation of several major pipeline projects, which have been financed at least in part by multilateral banks over the past few years. The controversies surrounding some of these projects due environmentally and socially relevant impairments connected with the investments have also been addressed by the Extractive Industry Report of the World Bank. Pipeline construction was the investment type chosen for the examination to be presented here, since pipelines frequently start in remote, unspoiled regions, and their routes often cross various natural zones and areas with various social structures. The question of safety during construction and operation of the line is always central to these projects; not only for the responsible authorities but also for other societal groups involved, such as environmental associations."

Jan 1, 2005

By Joe Roby

Rolling disc cutters are the business end of hard-rock and mixed-face tunnel boring machines (TBMs). Since their first successful employment on a TBM more than 50 years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates are higher and cutter costs are lower than ever before, proving the value of investment in cutter development. Disc cutters are used on a range of tunneling equipment, from pipe jacked slurry micro-TBMs less than 1 m (3.3 ft) in diameter to 15 m (49 ft) in diameter, hard-rock boring TBMs. The geological conditions under which they are employed range from sands and gravels, with several bar of water pressure, to extremely hard, massive rock with UCS up to 420 MPa. Regardless of the type of machine or geology, one thing remains constant: changing worn out cutters is costly. When cutters must be changed in the middle of a tunnel, the contractor incurs the cost of downtime as well as the cost of refurbishing or replacing the cutters. In the case of catastrophic cutter failures, the project can be stopped completely for long periods, and the costs mount up rapidly while tunnel production is at a stand still. Catastrophic cutter failures include the occasion when hard-rock disc cutters are failed in groups (called a ?wipeout? phenomenon) and the operator fails to stop the machine, which results in severe damage to the cutterhead. The cause of this can be either an undetected failed cutter propagating damage to surrounding cutters or operator error in steering. Regardless of the cause, the resulting damage can take days or even weeks to repair. When cutters fail prematurely on EPB or slurry machines in certain geological conditions, it is impossible to evacuate the chamber and, therefore, impossible to get [ ] into the chamber to change the cutters. The solution is frequently an unplanned intervention shaft that must be sunk at great cost. The importance of being able to predict cutter life accurately, and in all geological conditions, cannot be overemphasized. For these reasons, cutters have been developed for specific machine types and sizes, as well as for specific geological operating conditions. Different size cutters are required for different size machines. For example, while 483- and 508-mm (19- and 20-in.) cutters are used on large diameter TBMs, it is impossible to employ cutters so large on a small micro-TBM. Also, the cutter must be designed for the specific geological conditions under which it will be operating. The disc cutter rings required to bore extremely hard rock are the most expensive of cutter rings. However, they provide little advantage in weaker rock formations where less expensive rings will do the job as well. It is important to choose the correct cutter for the machine and the geological conditions in order to get the best balance of cost and risk.

Jan 1, 2009

By John Marsden, Mike Botz

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scaleup factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

By John Marsden, Mike Botz

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scaleup factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

By John Marsden, Mike Botz

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scaleup factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

Sep 3, 2019

By William R. Yernberg

The Fifth International Conference on acid rock drainage (ICARD 2000) was held May 21-24, 2000, in Denver, CO. The three-day conference consisted of about 150 oral presentations and poster sessions that described the state-of-the-art of acid-rock-drainage (ARD) science and technology. The conference also featured a trade show. It included representatives from consulting companies and government agencies with interests in ARD, as well as other environmental issues related to mining. The conference also included field trips to ARD treatment sites and short courses on acid rock drainage issues. ICARD 2000 was planned and promoted by the ICARD 2000 Organizing Committee and the Society for Mining, Metallurgy, and Exploration, Inc. (SME). Financial support was provided by Barrick Gold, BHP Copper, Homestake Mining, Noranda, Phelps Dodge, PlacerDome, the US Bureau of Land Management, the USEnvironmental Protection Agency and the US Geological Survey. Since the original ICARD was held in Roros, Norway, in 1988, knowledge has improved of the behavior of mine wastes as have methods of environmental mitigation. The ICARD 2000 presented the latest advancements in the field of acid drainage.

Jan 1, 2000

By Thomas Novak, Sampurna Arya

Controlling dust generation and keeping it below permissible limits to meet federal dust standards at the working face of a roomand-pillar coal mine is a challenge for a mine operator. With the recent changes in federal dust regulations requiring lower worker exposure, maintaining compliance has become increasingly difficult. The current most effective practice of dust control at a continuous miner face in an underground mine is the use of a flooded-bed scrubber. A study carried out by the National Institute for Occupational Safety and Health (NIOSH) indicated that a flooded-bed scrubber could achieve cleaning efficiencies between 58 and 90%. But, the operation of such a system is maintenance intensive. The flooded-bed scrubber screen becomes clogged with dust particles and requires frequent cleaning to maintain performance. However, the dust control issue is not solely a mining industry problem. Other industries face similar issues. The University of Kentucky collaborated with Toyota Motor Manufacturing on the development of a novel wet scrubber, called the vortecone scrubber, for capturing oversprayed paint particles in automotive paint booths. The vortecone scrubber achieved a cleaning efficiency of 99% and required minimal maintenance. This study aims to assess the ability of this vortecone scrubber to capture respirable dust in an underground coal mine. The paper presents the results of computational fluid dynamics (CFD) modeling of this vortecone scrubber. It discusses the effects of air quantity and dust particle size on the performance of the scrubber.

By Congling Shi, Marek Borowski, Yue Wang, Jianwei Cheng, Xixi Zhang, Xuan Xu

As the first barrier to prevent accidents caused by explosions in underground coal mines, the integrity and stability of mine seals have great effects on mine workers’ lives and underground production safety. In this paper, the mechanical responding performance of typical mine seals under the impact load are studied by using numerical simulation method. By such simulation studies, the safety of different seals subjected to the explosion load is evaluated. Seals’stability are also investigated under effects caused by various influence factors including thickness of mine seal, cutting depth into surrounding rocks, rock type, and the roof-tofloor convergence under given the explosion load. The research results can provide theoretical basis and reasonable improvements for mine seal’s construction practices for improving its anti-explosion performance.

By Congling Shi, Marek Borowski, Yue Wang, Jianwei Cheng, Xixi Zhang, Xuan Xu

As the first barrier to prevent accidents caused by explosions in underground coal mines, the integrity and stability of mine seals have great effects on mine workers’ lives and underground production safety. In this paper, the mechanical responding performance of typical mine seals under the impact load are studied by using numerical simulation method. By such simulation studies, the safety of different seals subjected to the explosion load is evaluated. Seals’stability are also investigated under effects caused by various influence factors including thickness of mine seal, cutting depth into surrounding rocks, rock type, and the roof-tofloor convergence under given the explosion load. The research results can provide theoretical basis and reasonable improvements for mine seal’s construction practices for improving its anti-explosion performance.

By K. Oraee

A comprehensive, harmonic and sustainable development has always been a real concern of state policy makers. To reach such development, regional planning is an approach which is widely applied. This paper deals with policies adopted by a given country with rich mineral deposits, in order to accomplish a mining growth as well as economic development in relatively poor regions. In this regards, first, some worldwide experiences belonging to China, with large scale mining operations and Nigeria with a small scale mining industry, are studied. The mining industry in Iran is then considered as a case study. The study continues by categorizing and prioritizing Iranian regions based on their mining potential and the degree of development, using statistical analysis and Taxonomy and AHP techniques. Results obtained serve to provide recommendations as to where capital investments in the mining industry would produce highest returns. The approach used, together with the practical policies suggested in this paper, can be used to adapt appropriate strategies for mining development in a way that contributes to regional development and a more effective income distribution.

Jan 1, 2012

By A. Duerksen

Surface coal mining in West Virginia has supplied energy to the eastern coast of the United States for over a century. The coal mining industry has been forced to adapt as societal demands regarding health, safety, and environmental impacts have changed with time. More recent pressure has called for another iteration of change: long-term post-mining sustainability. The research presented in this paper investigates one potential solution?or component of a solution?to improve mining sustainability in Appalachia: post-mining wind power. This paper intends to demonstrate and explain the feasibility of synergistic mine closure and wind development. Wind conditions at three reclaimed mine sites in West Virginia were monitored in order to develop representative case studies for post-mining wind power. This paper contains a summary of the literature consulted to plan the site assessments, the methodology employed to execute them, the analysis steps undertaken to derive conclusions, and a discussion of all findings. This research has found that significant cost savings can be yielded from synergistic mine closure and wind development, as compared to greenfield wind development. Though wind conditions themselves remain the primary driver for site feasibility, post-mining wind power is a practice with significant promise for improving project economics, contributing to renewable energy development, enhancing company-community relations, providing local employment opportunities, and exemplifying sustainable business practices in Appalachia.

Jan 1, 2012

By S. Frimpong

Cable shovel requires continuous monitoring through excavation to achieve reliability, longevity and economic usage. The operating environment and the stress and deformation fields on the front-end assembly must continually be monitored to avoid random fatigue failure. In this paper, the authors advance frontiers of cable shovel reliability through real-time stress and deformation monitoring during excavation. Cable shovel boom stress and deformation analysis are developed using a combination of flexible and rigid body approach. A virtual prototype is developed to simulate the cable shovel excavation in oil sands and to examine the motion, stress and local deformation of the boom. A numerical example is used examine cable shovel boom durability using stress and deformation fields simulation. The results show that stress and deformation are large around the joint between the upper body and the boom. The simulation of the effect of material properties on boom deformation shows that the deformation is larger in hard formation than in soft formation. The study provides a solid foundation for further study of failure life analysis of the cable shovel components.

Jan 1, 2006

By O. Schumacher

Guidelines for publication of information defining the amount and grade of resource material available in a deposit are well established in Australasia?s JORC Guidelines, Canada?s National Instrument 43-101 and similar documents in South Africa, Peru, Chile and elsewhere (Table 1). These guidelines provide standards to apply regarding the geologic and geostatistical basis for describing the level of confidence to be assumed for an estimate of the amount and grade of material. All of them provide for a strict distinction between material that has been demonstrated to be economically mineable and that which has not, and all of them provide terms such as ?resource? or ?exploration information? to be applied to data regarding material that has not been demonstrated to be economically mineable. It is not until an economic study has been completed that we are allowed to apply the powerful terms ?reserves? and ?ore? to our deposit material. Indeed, the application of these eye-catching labels immediately tells the reader that an economic study has been completed by a qualified person, and that the results of the study were positive. While extensive guidelines are established for describing the level of confidence in published geologic data, and the nature of the economic study that should be accomplished before using the terms ?reserves? or ?ore?, surprisingly little guidance is provided regarding the process to use, and the level of detail to attain, for estimating capital and operating costs for the study. The intent of this paper is to lay the groundwork for development of suitable guidelines for the cost estimating process. While the codes do not provide specific instructions for the cost estimate, they do provide numerous hints and clues to help determine the level of detail expected and the type of procedure to apply in preparing the estimate. This paper will first review the various codes to gain an insight into the thinking of the drafters of the codes regarding their unstated expectations for the cost estimating process. Based on this review, a series of guidelines are proposed for this purpose.

Feb 27, 2013

By Tom Ireland, Tony Rock

The proposed 1.83km long twin bore A3 Hindhead road tunnel planned for contruction in 2008 is being delivered under a Highways Agency Early Contractor Involvement (ECI) contract. The proposed construction methodology is progressive mechanical excavation of a horseshoe shaped tunnel with shotcrete installed close behind the face using robotic spraying equipment. The tunneling medium is a ‘soft rock’ sandstone for which there was little previous tunneling experience, requiring extensive geotechnical investigations and an innovative approach to lining design. A 240m long portal section though sandy material utilising a steel pipe umbrella is also required. This paper describes the development of the tunnel planning and design including the most recent developments in UK road tunnels, and the innovation included in the ‘permanent’ primary lining design.

Jan 1, 2007

By David Hopkins, Steve Klein, Bradford Townsend, Ed Sum, Derek Penrice

INTRODUCTION The Transbay-Caltrain Downtown Extension (DTX) Project involves the construction of an approximately 1.5-mile rail line that will extend Caltrain commuter service and the future California High Speed Rail system into downtown San Francisco. The underground rail extension will be constructed by mined tunnel and cut-and-cover methods. Tunneling challenges include difficult ground conditions, low rock cover, the presence of historic buildings along the alignment, and the large tunnel span, ranging from approximately 50 to 65 feet. Three mined tunnel construction methods were evaluated: the Stacked Drift Method, the New Austrian Tunneling Method/Sequential Excavation Method (NATM/SEM), and Tunnel Boring Machines (TBM). This paper describes the challenges presented within the mined tunnel section, and summarizes the evaluation of tunneling methods that led to the selection of NATM/SEM. PROJECT OVERVIEW The existing Transbay Terminal opened in downtown San Francisco in 1939. This facility is antiquated, and does not meet current building seismic safety standards or the transportation needs of the Bay Area. For these reasons, San Francisco voters approved Proposition H in 1999, which proposed to construct a new or rebuilt regional transit center at the site of the existing terminal and extend Caltrain commuter rail ser-vice to the new transit center. The new transit center is the hub of the Transbay Transit Center (TTC) Program, which will greatly enhance regional transit service by providing connectivity for six Bay Area transit providers at one facility. The program will be the largest inter-modal centerwest of New York City. The TTC Program is comprised of two major projects, the Transit

Jan 1, 2007

By D. Loring, J. Almgren

Climax Molybdenum Company’s Henderson Mine is a large panel caving molybdenum mine located about 43 miles west of Denver, Colorado. Three Joy M120-72-880 fans are installed in parallel on the No. 1 exhaust shaft. Throughout the mine’s history, ventilation changes such as the completion of the No. 5 exhaust shaft have decreased the utilization of these fans. To optimize fan performance they have been run with the full complement of 16 blades, down to as few as four blades. Since the completion of ventilation upgrades associated with the Henderson 2000 project, one surface fan has been operated under normal conditions with 10 or 12 blades. With the completion of a new network model of the Henderson ventilation system, a tool was built to develop fan curves for possible future fan configurations and predict future fan performance. This paper describes the tool and its use at Henderson.

Jan 1, 2007

The failure of a seal in an underground coal mine can have devastating consequences. Traditionally seals have been constructed as flat walls. Large hydraulic dams, on the other hand, are constructed as concave arches. This paper presents an initial analysis of the potential strengthening of seals by concave construction as well as the impact of additional cost in terms of labor and material. A simple finite element analysis of three-dimensional solids under uniform loading allows comparisons between the strength of a flat wall and a curved arch. The models are examined for reasonable behavior and displacements at 20, 50, 100, and 200 psi loads.

Jan 1, 2007