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By H. E. Goetzman

A cooperative research project supported by the taconite industry and the Minnesota DNR was undertaken to establish quality standards for carboxymethyl cellulose (CMC) based organic binders. The objective of this study was to identify the effect of CMC quality parameters such as degree of substitution, molecular weight, and purity as well as the effect of inorganic extenders such as sodium carbonate on performance. These factors have been evaluated by green-ball testing with two taconite concentrates followed by pot-grate tests. Balling tests with bentonite and Peridur were conducted to provide baseline data. At a constant DS the molecular weight as measured by viscosity had the greatest effect on green-ball drop strength. Dry-ball compression strength was most dependent on CMC addition rate and sodium carbonate content. DS was not found to have a major effect on green-ball quality for medium molecular weight CMC.

Jan 1, 1988

By Kevin Lundberg, Philip Sander, Daniel Weinberger, John Reilly

Since the early days of risk management, developments in technology and guidelines (ITA, ITIG, OGG, UCA) have advanced risk management and probable cost estimating, which are now widely recognized. WSDOT’s CEVP risk-based cost validation process is now established after 20 years. This paper traces these developments, summarizes advanced techniques, and presents examples of US and international projects with results. A particular case of using advanced risk evaluation to allow enhanced-capability TBMs to be considered in a competitive bid process is presented. Further advances, including the use of digital twin risk-based representation of complex projects, are described.

Jun 13, 2023

By Zong-Xian Zhang, Charlie C. Li

It has been observed that the rock debris of a strain burst event are often in the mode of tensile fracture. Seismic waves could create tensile fractures in the material nearby reflecting surfaces, such as at the boundary of the fracture zone and the rock surface of an underground space. The fractured rock could be ejected to the space when the seismic waves are powerful enough. The average ejection velocity of the ejected rock is a measure of the magnitude of a burst event. The ejection velocity is directly associated with the released energy from the seismic waves and with the strain energy stored in the rock prior to the burst. In some cases, the seismic wave induced tensile fracture and the energy conversion occur in successive moments during bursting. In this paper, tensile fracture caused by seismic waves is investigated through an 1D model. The relationship of the average ejection velocity of the ejected rock in a rockburst event is analytically established with the energy of the seismic waves and the strain energy stored in the rock.

Apr 26, 2022

By R. A. Haney

The Mine Safety and Health Administration (MSHA) has conducted studies both in coal and non-coal mines to evaluate methods for sampling diesel particulates in underground mines. The agency is investigating size separation techniques to distinguish between diesel particulate and respirable coal mine dust. Additionally, ashing techniques have been used to distinguish diesel particulate from mineral dust in metal and non-metal mines. As part of these studies, personal exposures to diesel particulate for various mining occupations have been measured. This paper describes the measurement techniques and summarizes the exposure levels for various underground mining operations.

Jan 1, 1993

By E. Zahl, J. Whyatt, H. Lawson

The U.S. Mine Safety and Health Administration (MSHA) issued Program Information Bulletin P09-03 in April 2008, providing formal guidance on using programs that model the redistribution of stress during underground mining of coal. A key part of this guidance is visual observation and mapping of ground conditions. If a correlation between ground conditions and model output can be established, the model is considered to be verified, and can be used to guide mine design in similar ground. A simple scale is recommended for ranking observed roof, rib and floor conditions. This paper discusses optimization and implementation of a ground condition rating scheme in the gateroads of a deep underground longwall coal mine. Roughly 80% of each gateroad length deteriorated in a fairly uniform manner. However, this manner varied between gateroads, as did pillar size. The implementation of a ground condition mapping program, similar to that recommended in PIB P09-03, was successful in characterizing the ground response to mining in gateroads of a longwall coal mine.

Jan 1, 2013

By Matthew Geary, Stephen J. Marino, Jordan A. Schreiner

"INTRODUCTION Project Overview The Southeast Collector (SeC) is a new 15km long 3.0m internal diameter wastewater tunnel designed by Hatch Mott MacDonald (HMM) that twins the existing 2.6m diameter York-Durham Sewage System (YDSS) tunnel. Both sewage tunnels are located north of the City of Toronto in Ontario, Canada. The SeC provides much needed conveyance capacity for the rapidly growing York Region population, supporting development until 2036 and increasing sewage system security (Hatch Mott MacDonald and AECOM 2011). Construction of the SeC will also permit flows of the twinned section of the YDSS to be bypassed in order to clean, inspect and carry out any essential maintenance within the YDSS tunnel. Although owned and operated by York Region, the SeC spans two regional municipalities beginning upstream from the intersection of Ninth Line and Rouge Bank Drive in the City of Markham in York Region to the downstream Finch Avenue and Valley Farm Road intersection in the City of Pickering in Durham Region. See Figure 1 for the SeC and YDSS alignment. The project includes 19 shafts and chambers with depths ranging from 8 to 48m in addition to seven facilities supporting the operation and maintenance of the sewer. The construction contract was awarded to Strabag Inc. in July 2011 for $291M CAD. Construction Management services were provided by a joint venture team of Hatch Mott MacDonald and AECOM. Existing York-Durham Sewage System The YDSS tunnel was completed in 1979 and was constructed using an open shielded TBM with ribs and lagging temporary support, followed by installation of a 380mm thick unreinforced cast-in-place (CIP) concrete final lining. The YDSS sewer system has numerous connections that accumulate flows from various urban areas within York Region. The section of the YDSS twinned by the SeC flows under gravity conditions and had been putting a strain on the municipality’s potential for population and development growth having reached its maximum capacity of 420 ML/d. According to the York Region’s Water and Wastewater Master Plan, the existing YDSS would not have been able to handle wet weather flows past 2016 (Genivar and XCG Consultants 2009). The dependability of this section of the YDSS is also of concern because it is the main and critical connection between the sewer systems upstream and the downstream Duffin Creek Water Pollution Control Plant (WPCP)."

Jan 1, 2016

By Joseph Githiria, Khadija Omar Said

Mineable material is defined using cut-off grade either as geological or economic cut-off grade. Both geological and economic cut-off grade affects the output generated in an open-pit mining operation. It distinguishes the amount of ore sent to the mill for processing and waste to the dump. This consequently affects the overall profits generated from the operation hence the need for cut-off grade optimization. There are several mining parameters that are considered in a typical cut-off grade model. They include economic, geological, and operational parameters. They have a significant effect to influence the cut-off grade selected in mining operations at any given period. Some of the parameters are stochastic in nature by having a random probability distribution that may not be predicted precisely. When selecting cut-off grades in a mine operation, the mining engineers must consider the dynamic nature of the operational parameters in order to maximize the net present value of the project. Modifying Lane’s cut-off grade model which was developed in 1964 to incorporate the stochastic parameters in the approach helps improve the net present value as shown in the paper. The modified Lane’s approach is developed into a stochastic computer-aided application code-named NPVMining. Using NPVMining, selected stochastic parameters are considered in this exercise to show the effect on the output (net present value). The selected parameters (price and grade-tonnage) are varied by ± 10%. NPVMining has a graphical user interface that makes it easy to use and displays results in a user-friendly way. It gives the user the choice to manipulate the data depending on the study being undertaken or any other factor affecting the specific mine. This paper analyses the effect of each of the selected mining parameters on cut-off grade using NPVMining to show the significance of monitoring their variance.

Jun 25, 2023

By David D. Gallagher, Edmond J. O’Donovan

It has been well accepted for many decades that hard starting of conveyors has associated problems. It is particularity damaging to the belt and splices. Recent measurements of hard starts on a long conveyor with a low modulus belt showed very unusual responses. These included violent accelerations and repeated "whip cracking" of the belt. Laboratory investigations of the very high strain rates experienced by the belt during the whip cracking, show mechanisms for belt damage that are not associated with normal usage. This paper outlines the measurement to show that for long, low modulus conveyors, constant torque controls are inappropriate and time ramp controls are really essential.

Jan 1, 1998

By E. Rubenstein, V. Gangrade, K. V. Raj, M. L. Harris

Underground stone mine ventilation is characterized by large openings with low resistances. These mines primarily face three challenges: moving adequate volumes of air, controlling and directing the airflow, and planning ventilation systems that work well with production requirements. Given these challenges, this paper examines the data collected by the Mine Safety and Health Administration (MSHA) to determine the extent to which respirable crystalline silica (RCS) and diesel particulate matter (DPM) are an issue in underground stone mines. Out of 522 sampled mines, there were 108 personal samples exceeding the RCS Permissible Exposure Limit (PEL) during 2000–2020. DPM were more prevalent than RCS in these mines with 382 personal samples exceeding the DPM PEL out of the 929 mines sampled during 2002–2020. Dilution of DPM is usually the defining parameter for design of mine ventilation systems in largeopening underground stone mines. With this knowledge, focused attention can be directed to these mines so that appropriate prevention and mitigation techniques can be utilized to prevent stone miners’ exposure to RCS and DPM and subsequent respiratory diseases.

Mar 2, 2022

By K. A. Natarajan, M. K. Yelloji Rao, P. Somasundaran

The bacterium Thiobacillus ferrooxidans triggers the surface modification of sulfide minerals to provide hydrophilicity or hydrophobicity for the flotation of sphalerite and galena. The effects of initial cell concentration, period of biotreatment and pulp density on the floatability of the minerals are discussed. With galena, flotation enhancement obtained through sulfuric acid treatment was retarded by biotreatment at all cell concentrations due to chemical effects. Such a decrease occurred for sphalerite only at cell concentrations sufficiently high for bacterial attachment to the mineral surface. The variables affecting surface modification (and, thus, flotation response of the minerals) include the cell concentration used for bacterial conditioning, the period of biotreatment and the pulp density. Although bacterial growth during biotreatment was observed even in the absence of nutrients, such growth was more common in the sphalerite suspension than in the galena suspension. Cell protein estimations suggest that more cells are attached on galena than on sphalerite. Probable reaction mechanisms associated with bacterial modification are discussed.

Jan 1, 1993

There has been some confusion over the selection of discount rates when performing stochastic simulations of a project's net present value (NPV) using risk- adjusted discounting techniques. Some argue that lower discount rates should be used when performing stochastic valuation simulations. This creates higher NPV values and improves the attractiveness of a project. Others argue that the discount rate should not be lowered for these simulations. This paper exposes the source of this confusion. It demonstrates that stochastic simulations do not remove the risk inherent in a project and, therefore-do not improve a project's value to the risk-averse investor. Risk-adjusted discount rates should, therefore, not be adjusted downward when performing stochastic NPV simulations. Stochastic simulations are, however, shown to he useful in several aspects of project valuation.

Jan 1, 1996

By A. Cecala, J. Noll, J. Hummer

"NIOSH has observed that many control rooms and operator compartments in the US mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room which had no cleaning system for intake air, a filtration/pressurization system originally designed for enclosed cabs was modified and installed. Eighty-seven percent of submicron particles were reduced by the system at static conditions, meaning that greater than eighty-seven percent of respirable dust particles should be reduced. The particle size distribution for respirable dust particles are greater than for submicron particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced which is an important component for an effective system and minimizes particles (e.g. dust) from entering into the room. The intake airflow was around 118 cfm, which is greater than the airflow suggested by ASHRAE for acceptable indoor air quality. INTRODUCTION Chronic overexposure to respirable silica dust (particle diameter < 10 microns) leads to a progressive lung disease known as silicosis. Workers who develop silicosis have an increased incidence of lung cancer and pulmonary disorders. In June 1997, the International Agency for Research on Cancer (1) found sufficient evidence to declare that inhaled crystalline silica in the form of quartz and cristobalite is carcinogenic. Mining is one of the leading industries for occupational exposure to silica dust (2-7). Control rooms located in dusty areas in some mines are of particular concern (8). Many mineral processing operations utilize operator’s compartments and/or control rooms to house workers who are performing particular job functions. Most industrial processing mills have rooms where a worker looks out over the facility and has direct control over the product flow throughout the entire building. In addition, primary crusher operators are often located in a compartment from which they are able to view the primary crushing function. Their job is to control when trucks dump into the primary jaw crusher and the rate of feed of the ore from the hopper into the crusher. Many of these control rooms and operator booths do not have filtration systems capable of cleaning air entering the control room or booth, which can result in elevated concentrations of dust in the room or booth. To reduce the dust concentrations in these rooms, it would make sense to clean the entering air with filtration/pressurization units similar to those proven to provide a clean environment in enclosed cabs."

Jan 1, 2016

By Frank H. Skelding

A new, large mine is about to be born. Many years and millions of dollars have been invested in exploration. An orebody has been found and proven. All necessary political and legal work to establish rights and conditions for development are complete. The feasibility studies are favorable. Financing has been arranged. Board approval has been given to proceed. The time has come to engage a contractor to design and build the new facilities in a location, as is the common case today, far re¬moved from the centers of advanced technologic development where the minerals will ultimately be used. A select list of Engineering and Construction (E&C) companies is asked to prepare proposals. At this point the common viewpoint among mining companies is that the company&apos;s sole remaining problem, a major one to be sure, is to select qualified contractors to design and build the project at the lowest cost and shortest time possible so that production can start generating a return on investment. The purpose of this discussion is to explore the viewpoint of the large E&C contractor toward such projects. It differs in important ways from that of the client mining company and it is these differences and the reasons for them that must be understood by the client if severe difficulties and misunderstandings with the contractor, starting at the beginning of contract negotiation and continuing through design and construction to final startup are to be avoided or minimized. Often enough, the difference is in degree, not kind, which only serves to obscure the fact that a difference exists.

Jan 1, 1975

By William L. Carter

Through your presence here this morning and your membership in the Society of Mining Engineers, you have shown that you are interested in keeping abreast of the latest technology and mining procedures, want to be part of the continuing progress made by those in your profession, and are looking for ways to participate in expanding your professional and personal experiences and skills. All of these factors are part of your continuing education, the need for peer identification or recognition, and the desire to make a specific contribution to strengthening your profession. However, you may be here with or without your company support and financial backing, unless you are self-employed. Whether you are here for the above reasons, or for many others, your presence reflects a recognition of the importance of participating in the organizational structure of your profession.

Jan 1, 1981

By Tad S. Golosinski

The paper presents the computing stream of the mining engineering curriculum at he Western Australian School of Mines (WASM), a branch of Curtin University of Technology. Learning to use computers begins during the first semester of the initial year of studies and culminates in the Mine Design Project done during the last semester of study. It covers all areas of computing which are judged to be of importance to the graduate.

Jan 1, 1996

By A. C. Burrow, R. P. King

A dynamic model that predicts the variation of carbon content with time in the argon-oxygen decarburization (AOD) process has been developed. The model recognizes three distinct zones in the AOD vessel: the tuyere region in which the blown oxygen reacts very rapidly with the metal components in the molten alloy; a region in which bubbles of inert gas and oxide drop lets rise through the molten alloy; and a zone in which the slag layer can interact with the molten alloy. The process is dynamically controlled by the rate at which dissolved oxygen, produced on the surface of rising oxide droplets, and dissolved carbon diffuse through the molten alloy to react at the surface of the rising bubbles. The rate at which carbon and oxygen react on the bubble surface is assumed to be intrinsically very fast. Predicted decarburization rates compare reasonably well with rates measured in the AOD vessel at Middleburg Steel and Alloys. The model has been developed primarily to allow development of a time-optimal blowing stategy for the AOD vessel.

Jan 1, 1990

By E. Fahrenkrog

An intelligent supervisor developed using expert system tools and applied to a crushing plant is presented in this paper. The structure of this supervisor, based on a model of a human operator, consists of a Knowledge base containing a qualitative model of the process, and a Rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of systems to supervise the automatic operation of a plant.

Jan 1, 1989

By T. V. Shockley

The Gulf Coast, from New Orleans, Louisiana to Brownsville, Texas, is one of the largest high energy consuming areas in the United States. This region has areas of very high industrial density. The lower Mississippi River from Baton Rouge past New Orleans has a high industrial density. Lake Charles, Louisiana, the Orange-Beaumont-Port Arthur area, Houston (4 separate areas) and Corpus Christi all have the same high industrial density. This situation developed due to good transportation, good labor conditions, good weather and the abundance of cheap energy-gas and electricity. Obviously the latter had the greatest impact. The availability of cheap natural gas made Gulf Coast sites very attractive to energy intensive industry such as metals and petro-chemicals. The area was also very attractive to refinery development due to the large supply (endless?) of crude oil available. As we all know, the energy situation has changed dramatically in the last five years. The cost of a MMBTU has risen from the 17¢ to 19¢ level to a price of $1.95 to $2.10. The price of interstate gas, as defined by the National Energy Plan recently passed by Congress, was approximately $1.98/MMBTU escalated to October, 1978. It goes without saying, that this has had a major impact on doing business in the Gulf Coast. As fuel prices soared, different companies responded in different ways; but overall, industrial energy consumption along the coast was reduced 20% to 25% from 1974 to 1975. Since 1975 production and energy use has been increasing, however, production at some plants is still significantly below plant capacity.

Jan 1, 1979

By John Berney-Ficklin

Large scale grinding mills can reduce both capital and operating costs for concentrators. These mills can be effectively used, but they must be free from design and manufacturing deficiencies if they are to reach their full potential and avoid costly downtime. This paper presents the evolution of today&apos;s complex grinding mill specifications and discusses the most important items to look for when buying new equipment. It emphasizes the need to monitor specification requirements during design and manufacture. It also discusses the growing trend to have grinding mills fabricated in overseas plants, and the importance of recognizing this when preparing specifications.

Jan 1, 1987

By Walter Küng

The Henderson Coarse Ore Conveying System is a three flight belt conveyor system transporting primary crushed molybdenum ore 24 km (15 miles) underneath the North American Continental Divide. One of the conveyors is 16.8 km (55,200fi) in length with 8,200 kW (11,000 HP) of installed power. The overland conveyor contains 11 vertical curves and 9 horizontal curves, some with radii as small as 1,500 m. he system began full operation in December 1999 and is one of the longest and most complicated belt conveyor systems yet constructed. he design of this conveyor system utilized many innovative engineering concepts including low-energy belt covers, low-resistance idlers, torque-controlled tail drives, combined gravity and active winch take-up systems, small radius horizontal curves and belt turnovers. his paper reviews the start-up of the system, discusses the success of the design and addresses the lessons that can be learned from the first 4 years of operation of this unique conveyor system

Jan 1, 2004