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By Dan Ifrim, Andre Solecki

Tunneling could be a major challenge to tunneling contractors as tunneling operations can be seriously affected by the Tunnel Boring Machine (TBM) performance. Specifying the appropriate TBM methodology, selection of systems and features, is critical for managing tunnel risks and contribute to successful tunneling project. The paper analyzes tunneling records from the recently completed City of Toronto’s Ashbridges Bay Treatment Outfall tunnel project and underlines the righteous selection of the TBM type and associated TBM systems in achieving good advance rates during tunnelling and managing project risks. The paper intends to draw attention of a few aspects of TBM technical specification importance and highlight the lessons learned from this process.

Jun 13, 2023

By Igor Gonzales G.

Southern Peru Copper Corporation (SPCC) has recently completed the construction of copper leaching, solvent extraction, and electrowinning facilities at their Toquepala and Cuajone plants in Southern Peru. Much of the ore for these new operations is the result of the existing mining operations that have been in existence as early as 1959. At Toquepala, pre-conditioning and bacterial dump leaching of the sulfide ore that was too low in copper content to be processed through the copper concentrator began in 1987. The Cuajone heap leach operation is treating copper oxide ore that has been stockpiled since the Cuajone concentrator began operation in 1976. The pregnant leach solutions from the dump leaching at Toquepala and the permanent pad heap at Cuajone are combined into one plant feed solution. Adjacent to the large dumps at Toquepala, a solvent extraction and electrowinning facility has been constructed. The electrowinning facility has a planned annual production rate of35,000 metric tons per year Grade A cathode copper. Initial production of the cathode copper began in November 1995.

Jan 1, 1996

By D. L. Kiser

Conventional and advanced coal preparation technologies were investigated through both a literature search and through direct contact with investigators and developers. In addition to a brief description of each process, performance characteristics including feedstock type, ash and sulfur reduction, thermal energy recovery and cost are provided in a tabular form. Seven of the most commonly utilized conventional coal preparation processes, including those respectively accepting coarse, intermediate and fine coal feed, were reviewed. It was found that certain properly implemented and well maintained conventional processes were capable of better than 75 percent ash removal while recovering 90 percent or more of the inherent thermal energy. Almost 50 advanced coal preparation processes were investigated based on biological, chemical and physical principles. Physical processes investigated included cycloning, homogeneous heavy media, electrostatic, high gradient magnetic, flotation and selective coalescence. Using pulverized coal as a feedstock, some of these processes are respectively reported to be capable of removing better than 95 percent ash. 95 percent pyritic sulfur, and 50 percent organic sulfur while incurring energy losses of less than 5 percent.

Jan 1, 1986

By Hakan Uyguçgil, Beril Bayraktar, Adnan Konuk

In mining, which is one of the industries with the highest risk of occupational accidents, a primary goal is to enhance safety through the thorough investigation of accidents using reliable methodologies. In this research, the data from 13,653 accidents reported in the Karadon Hard Coal Enterprise between 2000 and 2011 were analyzed and compared using the life-table and Kaplan-Meier methods. Accident records were classified and analyzed into four categories: environment-related, equipment-related, person-related and other accidents. Findings in terms of survival time indicate that environmentrelated and person-related accidents had the highest risk in Karadon, with equipment-related accidents having the lowest. This study established the reliability of using survival analysis methods to investigate occupational accidents in the mining sector. Given that environment-related and person-related accidents occur in a relatively short period, such as one year after starting work, it is recommended that research be done to improve workplace and occupational safety measures and broaden the training given to miners. Additionally, it is determined that increasing the use of automation and mechanization in underground coal mines, combined with developing a thorough equipment safety training program to raise awareness of the danger, can help prevent person-related occupational accidents caused by the interaction between equipment.

Feb 1, 2024

By J. Oliver, J. Cleason

"With maintenance costs rising and an increasing demand for higher production, the use of sealed spherical roller bearings can reduce maintenance costs while providing increased production uptime. The sealed spherical bearing has increased bearing life by slowing the ingress of contamination. This paper will describe how contamination and bearing wear is reduced by reviewing case histories from coal and metal mines that improved their production by decreasing downtime using sealed spherical roller bearings. INTRODUCTION The spherical roller bearing (SRB) is a robust rolling element bearing that can accommodate high radial loads, low to moderate axial loads, and misalignment with no loss in carrying capacity. (i.e. Figure 1) Because of these characteristics, it is a favorite in mining applications and many other heavy industry applications. Primary applications are the various pulleys on conveyors. Coal and hard rock mines have hundreds of miles of conveyor lines and countless head, tail, drive, and idler pulleys. Maintaining the bearings on these pulleys and replacing bearings that have failed can be a huge expense to a mine in components, labor and downtime. Ideally, the bearings are replaced when the pulley is changed out according to the maintenance cycle, about every 4 years. Reality, however, causes the bearings to be changed out every year, or sooner. These premature bearing replacements can cause production shut downs for as long as 8 hours. Conveyor pulleys have been targeted at many mines as the single biggest maintenance pain point.The primary reason for replacing conveyor bearings is internal wear from fine, solid particle and water ingress through the bearing housing seals. (i.e. Figures 2 & 3) Traditionally, the bearing is mounted in a split pillow block housing (SAF, FSAF, SDAF or SNL are typical industry styles) with only labyrinth seals (LER/LOR) for protection against the ingress of contaminants. The bearings are lubricated with grease. A common way to extend the MTBR is to purge the bearing system with large quantities of grease to flush out the contaminants. If the bearing, and thus the housing seals are not frequently purged with grease, fine solid contaminants enter the housing and bearing through the labyrinth cavities."

Jan 1, 2015

By Ben W. Burdett

Since the late 19701s, the use of microcomputers in the minerals industry has grown to the point where today they can be found in virtually every plant within the industry. Their use in every aspect of instrumentation and control has increased the ease of operation and control of every phase of mineral processing. Their incorporation in sensors, transmitters, indicators, and controllers in addition to their use in distributed control and computer systems has provided operators with more timely accurate information than they have ever had before. This has led to an increase in the operator's effectiveness and an improvement in overall productivity. The ultimate aim of plant control is to maximize recovery in the mineral processing operation, and the microcomputer has spawned many tools that are now making this goal attainable. This paper discusses individual use of microcomputers in the areas previously mentioned as well as their collective use in overall control systems. The incorporation of local control systems in total plant control including the communication of information throughout all levels of plant management is also discussed. Finally the role the microcomputer is playing in today's plants is illustrated with numerous references to current examples.

Jan 1, 1985

By Laurent Rus, Bakar Amara, Jean Habimana

The La Fontaine Tunnel in Montreal, Quebec is currently undergoing major structural rehabilitation work and systems upgrade work to comply with current codes, standards and best practices in fire life safety and to extend its lifespan of this 55-year-old immersed tube tunnel for at least another 40 years. The paper discusses design consideration of ongoing works that include structural analyses to evaluate repair strategies for the post-tensioned reinforced caissons, the scheme to repair two leaky joints between caissons, the design of passive fire protection that involved in situ and real scale laboratory tests, and other tunnel systems upgrades.

Jun 13, 2023

By R. S. Jurani

Sunshine Mining Company's Kellogg operation is the primary silver producer in the United States, and maintaining a comfortable working environment in this deep underground mine historically has been a complex and costly problem. To improve the ventilation and cooling systems at a time of declining and uncertain silver market, it was proposed to optimize the performance of existing facilities at minimum cost. This paper discusses a 2-year, $400 000 optimization program that resulted in increased total mine airflow, cooler ambient temperatures, reduced compressed air usage, and lower energy consumption by primary fans, air compressors, and refrigeration plants, thereby saving the company approximately $650 000 per year.

Jan 1, 1987

By Martin P. Corriveau

It is not news to anyone in the mining industry that federal action in the prevention and abatement of air pollution has seriously affected the industry both directly and indirectly. It is the purpose of this paper to review how the development of federal action is directly affecting the coal mining industry's number one customer, the fossil-fuel-fired steam generating power plants and, consequently, the industry itself indirectly. In essence, Public Law 84-159 of 1955 as amended by the Clean Air Act of 1963 and its revisions in 1967 and 1970 progressively tightened federal coordination and management of air pollution control programs throughout these United States. The Environ- mental Protection Agency (E.P.A.) set up to direct the programs was charged to establish National Air Quality Standards, Standards of Performance for New Stationary Sources, and National Emission Standards for Hazardous Air Pollutants.

Jan 1, 1973

By Jagannath Pal, Ammasi Ayyandurai

Hematite ore pellets require a much higher induration temperature than magnetite ore pellets because no exothermic heat is generated due to oxidation inside during induration-like magnetite pellets. Carbon is used as in situ heat source in hematite ore pellets which can reduce temperature requirement in the induration strand and hence decreases energy consumption. Many investigators have reported that a 0.8–1.25% addition of carbon in hematite pellets can improve the pellet properties also. However, to investigate the exact role of carbon in hematite pellets, its reaction mechanisms and kinetics study are required which have not been done so far. Therefore, the reaction mechanism and its kinetics have been studied in this investigation. It has been found that carbon reaction happens in pellets from the surface towards the center in a topochemical manner which is controlled by pore diffusion of gas, and its activation energy is around 52 k J mol− 1. It is also found that apart from in situ heat, carbon in hematite pellets enhances diffusion bonding which improves pellet properties. This study ascertains the exact role of carbon in hematite pellets which may help operators to use carbon effectively to reduce energy consumption and improve pellet properties.

Nov 6, 2022

By Peter B. Dowden, David T. Cass

A shield on a tunneling machine has two basic purposes. Firstly to provide temporary support in unstable ground, maintaining the integrity of the bore and protecting the operators, and secondly, in conjunction with other sealing devices, to prevent the ingress of water. In any specific tunnel, unstable ground and water may or may not occur together. Further, there are a number of different ground behaviors that may be termed unstable and these must be defined in order to determine the most suitable type of machine. Beyond the shield itself, the cutterhead and the mucking system design are critical in successfully traversing difficult geology. In any but the shortest tunnels, variations in the geological conditions and the requirement of an acceptable advance rate can impose increasing degrees of sophistication in the machine design. In this paper we will review current designs of shielded type machines and their application, and discuss new developments which blend hard and soft ground tunneling technology. We will also indicate that in some conditions, although first impressions seem to favor a shielded machine, in fact an open gripper TBM may be the wisest choice.

Jan 1, 1991

By R. A. Matuszak

Throughout the history of power excavating machines, engineers have continuously tried to shape the main drive speed-torque characteristics to provide an optimum performance from each main motion. Selection of prime mover for the various motions has been the subject of many engineering studies and most forms of energy conversion have been tried. A new form of electrical power conversion looms on the horizon' as the most optimum yet. Controlled frequency operation of a squirrel cage induction motor increases the reliability of the most reliable form of energy conversion (electrical) found thus far and at the same time improves the performance characteristics.

Jan 1, 1977

By Roger D. Sharpe

Oklahoma contains extensive resources of high-purity gypsum that were deposited in the Anadarko and Hollis basins during Permian time. The gypsum resources and reserves are estimated to be about 48 billion short tons and a; located in the western portion of the state. Oklahoma is the largest producer of gypsum products in the United States. The Blaine Formation and the Cloud Chief Gypsum contain several beds of minable thickness. Four stratigraphic units in the Blaine Formation are quarried in Oklahoma. The Shimer, Nescatunga, and Medicine Lodge Members are quarried in northwest Oklahoma. The Van Vacter Member, consisting of three gypsum beds, is quarried in southwest Oklahoma. The Cloud Chief Gypsum is quarried in the west-central part of the state. The gently dipping gypsum in the Blaine Formation generally crops out along low escarpments and is covered in the downdip direction by increasing overburden, consisting of sand, shale, and/or dolomite. Anhydrite occurs in the downdip direction under the thicker overburden. The Cloud Chief Gypsum crops out as hills, which are eroded remnants of a more widespread, massive sulfate unit. All of the gypsum produced in Oklahoma is extracted using quarrying methods. A variety of products are made from gypsum quarried in Oklahoma. The products are manufactured from uncalcined, calcined, and deadburned gypsum. Products vary from raw, ground gypsum used for agriculture, to high-value-added industrial plasters, cements, and fillers produced from calcined gypsum. A sampling of the many products manufactured from Oklahoma gypsumincludes: (1) agricultural-soil amendment; carrier for insecticides, pesticides, and herbicides; calcium supplement in animal feeds; (2) gypsum wallboard-common, fire-resistant, and water-resistant varieties; (3) industrialgypsum plasters-art and casting, pottery and ceramic, molding and tooling, crayons, wall patching; (4) industrial gypsum cements-oil-well cement, high-strength statuary, high-strength tooling, fiber-reinforced architectural, road and bridge repair; (5) food and pharmaceutical-filler and binder in aspirin and other medicines, yeast activator in brewing of beer, moisture absorbent in bread and pizza dough; and (6)portland-cement retarder-ground with clinker to control setting time.

Jan 1, 1999

By Ralph M. Stricklen

The need to move large tonnages of slurry has grown as mines have become larger. As existing tailing depositories are filled up, new mines developed, or environmental requirements dictate, it becomes necessary to transport tailing particularly over longer distances. A typical slurry transport system is shown in Figure 1A. Figures 1B, 1C and 1D show sketches of the system auxilliary components: feed box, receiving sump and drop box, respectively. There are two basic types of slurry transport systems, packed flow and slack flow. Packed flow is typified by a pipe running full; slack flow by a launder or pipe running less than full. Slack flow in launders or channels is also referred to as open channel flow. Generally slack flow slurry transportation involves a flow with less than 65 per cent solids, and there is an upper limit on particle size, depending on the slope of the system.

Jan 1, 1984

By Y. Wang, G. Xu, N. A. Amoah, A. Kumar

Mining-induced coal dust causes various respiratory diseases to mine workers, such as coal workers’ pneumoconiosis (CWP). Current available underground monitors are expensive, heavy and only measure mass concentration. These disadvantages limit them for regulatory sample monitoring purposes only while personal exposure levels for most miners remain unknown, risking miners to potential overexposures. Low-cost light scattering PM sensors offer a potential solution to this problem with capability of high spatio-temporal resolution PM characterization. However, these sensors require careful calibration before they can be applied in mining environments. There is basically no comprehensive study in the literature using a standard protocol assessing these sensors for coal dust monitoring. With the aim of calibrating the PMS5003 sensors for coal dust monitoring, we design the calibration method and system to calibrate these low-cost PM sensors coal dust monitoring. Working principles of present coal dust monitor and low-cost sensors are presented in detail. The linear regression calibration model which is used for the sensor calibration is further described. Sensor calibration and evaluation protocols are comprehensively compared and discussed. This investigation reveals the feasibility of low-cost sensors for real-time personal coal dust monitoring in underground coal mines.

Mar 2, 2022

By Steve Kral

"Liebherr, as most anyone involved with the global mining industry knows, is one of the world’s largest makers of mining and construction heavy equipment. The familyowned company has been around since the 1940s and, according to Stefan Heissler, by the end of next year, will employ about 44,500 people worldwide. Heissler is a member of the board of directors of Liebherr International AG.It all started for the Switzerland-based company when Hans Liebherr first recognized a need for heavy equipment in the construction industry, Heissler said. His first product, introduced in 1949, was the TK10, a mobile crane that, at the time, was a groundbreaking innovation to the heavy construction industry. From there, the company began its growth into a world-leading heavy equipment manufacturer that always relied on innovation.In October, Liebherr gathered a group of mining and construction magazine editors in Leoben, Austria to take a look at the company’s latest addition to the global mining and construction markets. On the mining side, Liebherr provided a demonstration of its T-236 100-t (110-st) haul truck and the PR- 766 50-st (55-st) crawler tractor. The one-day demonstration took place at the Erzberg iron mine near Leoben, where both machines are being proven.The Erzberg Mine, operated by VA Ersberg, has been in operation for about 1,300 years and is said to be Europe’s largest surface mine. It employs about 230 people and mines about 12 Mt/a (13,200 million stpy) of ore, producing about 3 Mt/a (3.3 million stpy) of fine-grained iron ore.T-236 rigid-frame truckThe new T-236 rigid-frame dump truck, with a diesel electric drive system, is Liebherr’s entry into the 100-t (110-st) class and is the first in this class with a four-corner, oilimmersed braking system. The haul truck was first introduced during the 2016 MinExpo in Las Vegas, NV. The unit has since successfully completed its testing phase and is currently in its first field operation trials at the Erzberg iron mine in Austria."

Jan 12, 2017

By M. J. Gula

In the solvent extraction -electrowinning recovery of copper from oxide or sulfide ores there is a continuous transfer of iron and other impurities from the primary leach solution to the copper electrowinning electrolyte via chemical transfer or mechanical entrainment. Iron is the principal impurity that has to be controlled in the electrolyte by a "bleeding" of the electrowinning solution. This bleeding transfers copper and sulfuric acid back to the primary leach circuit along with the iron. Copper is recovered via the solvent extraction process and generally the sulfuric acid is used as a reagent in leaching. Unfortunately, cobalt, which is added to the electrowinning solution to modify the anodic process, is irreversibly lost through the bleeding operation. This cobalt loss represents a significant operating cost to SX-EW copper producers. DiphonixTM ion exchange resin contains diphosphonic acid and sulfonic acid functional groups on a polystyrene-divinyl benzene matrix. This resin has been found to strongly and selectively extract ferric ion from copper sulfate -sulfuric acid solutions containing cobalt. Thus, an ion exchange process using DiphonixTM resin for the control of iron has been developed to replace the conventional bleed stream process. The new process minimizes the loss of cobalt from the electrowinning circuit and strips the iron into a sulfate based solution suitable for leach solution makeup. In addition, this process can effect a lowering of the total iron concentration in the electrolyte circuit with an associated increase in current efficiency. In this paper, data on the loading and elution of iron are presented. Laboratory and pilot scale data will be discussed along with information on process design and comparative economics.

Jan 1, 1996

By Moussa Wone, William Levy, Christopher Caruso, Zachary Spera, Thomas Hennings, Richard Stacy Kinchen, PE Joel Kantola

"Owners constructing new combined sewer overflow (CSO) systems increasingly seek to have project design lives of 100 or more years in response to the growing size, complexity, and cost to construct and operate these systems. However, a codified and universally accepted approach to achieving this goal in the United States does not currently exist since service life prediction is a relatively new technical field. This paper discusses how the 100-year design life requirement was met for the design of tunnels, drop shafts, and diversion structures in the DC Clean Rivers Program (DCCRP). The authors identify some commonly referenced publications, present the testing framework used by the program manager to characterize the CSOs, review the design criteria used to guide the 100-year design life development, and establish guidelines to be considered by program managers and designers when implementing similar extended design life requirements in other CSO control programs.INTRODUCTIONLike many older cities in the United States, the sewer system in the District of Columbia consists of both combined sewers and separate sanitary sewers. When the capacity of a combined sewer is exceeded during storm events, the excess flow, which is a mixture of sewage and storm water runoff, is discharged to the District’s receiving water bodies (Anacostia River, Potomac River, and Rock Creek) and tributaries through outfall structures. This excess discharge during storm events is called a combined sewer overflow or CSO. A total of 53 CSO outfalls for the combined sewer system are listed in DC Water’s National Pollutant Discharge Elimination System (NPDES) Permit issued by the U.S. Environmental Protection Agency (EPA). The DC Clean Rivers Program (DCCRP) will reduce the number of CSO outfalls into the Potomac and Anacostia Rivers and decrease flooding in DC neighborhoods during extreme rain events by capturing, storing, and conveying diverted CSOs to the Blue Plains Advanced Wastewater Treatment Plant."

Jan 1, 2016

By Chris Laughton, Bernhard Spoerr

"Tunnel inspections are increasingly needed to ensure that aging infrastructure does not fail in service. To this end the time between inspections is being reduced, the thoroughness of each inspection is being increased to provide for a more detailed assessment of conditions and inventory defects. The conventional Tunnel Report, containing hand-drawn maps and/or photos, and a log describing observed defects and areas of deterioration, is being increasingly replaced by LiDAR generated 3-D surface maps. The data collection process that traditionally supports development of a Tunnel Report is labor-intensive, taking crew-days of engineering effort, and requires partial or full stoppage of tunnel operations. In an urban setting, such multi-day interruptions in service are difficult to countenance for a near-capacity tunnel operation. Under time pressures, the detail and accuracy of the manual inspection process will inevitably be compromised, resulting in a high cost, low quality product. As the tunnel inspection window decreases the argument for incorporating laser scanning in to the inspection process is increased dramatically... The 3D scan technology allows detailed and accurate data to be collected within the tight time frames demanded by the owners and operators of critical infrastructure. Not only does the use of laser scanners improve the 3D accuracy of the data collected, it also, enhances the efficiency and safety of the inspection process, reduces data collection and processing costs and enhances the reliability of results over time. The paper will also demonstrate the value of adding photogrammetric data to the 3D Model to show surface defect discoloration. The accurate and detailed data collected by a combination of LiDAR and photogrammetric techniques provide superior data needed to inform critical asset management decisions related to maintenance, repair and replacement."

Jan 1, 2016

By Erika Moonin, Jim Nickerson, Claudio Cimiotti, Roberto Bono

"In response to the severe drought on the Colorado River basin and in order to preserve existing water capacity to the Las Vegas Valley, the Southern Nevada Water Authority contracted a new deep-water intake (Intake No. 3) located in Lake Mead. The current project (Contract No. 070F-01-C1) includes 5 km (3 miles) of tunnel with very difficult geological conditions and a 200- m (650-ft) deep shaft and marine works. This paper will present the current status of the design-build contract being constructed by Vegas Tunnel Constructors and the challenges and problems faced and the innovative solutions developed to handle the difficult conditions encountered during tunneling with up to 15 bars of pressure.ProjectbackgroundThe Las Vegas Valley receives the majority of its water from Lake Mead, which is located approximately 30 km (20 miles) east of the Las Vegas, NV metropolitan area. Due to the severe drought that has hit the southwest region of the United States, the water level in Lake Mead has receded from its high water level of 372 m (1,221 ft) above mean sea level (amsl) to a low of 330 m (1,076 ft) amsl in June 2015. Should the lake level continue to fall, at elevation 320 m (1,050 ft) amsl, the current water intakes will not be able to draw enough water to meet the needs of the local area. The risk of losing water capacity has prompted the construction of a new deeper intake. Not only is the new Intake No. 3 situated at a lower elevation in the lake at 262 m (860 ft) amsl, the new Intake No. 3 is also located to draw better quality (Fig. 1).Project challengesThe project has had several difficult challenges to overcome:• The work consisted of a 1.2 kt (1,300 st) structure constructed on a barge and lowered 100 m (330 ft) into Lake Mead anchored with 9,200 m3 (12,200 cu yd) of tremie concrete.• The drill-and-blast starter tunnel was impacted by three inflow events, resulting in a one-year project delay.• One of the main challenges was selecting the tunnel boring machine (TBM) and excavating the tunnel with expected hydraulic head pressure of as much as 17 bar (16 bar was the highest pressure recorded during the drive), crossing faulted areas, low rock cover and the risk of tunnel instability due to direct connection with the lake.• Extensive pre-excavation grouting with a constant head pressure ranging from 12 bar to 15 bar.• Structural repair of the cutterhead in difficult hydrogeological conditions [water inflow of approx. 800 m3/hr (4,000 gpm)].• Complete repair of the cascade sealing system for the main bearing and two replacements of the pinion bearings.• The TBM approach to the intake structure."

Jan 1, 2015