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By M. B. Daza, B. Lattimer

"Even with modern detection and firefighting techniques, mine fires continue to be a safety concern. However, some underground mine fires can be addressed with the remote application of high expansion foam, reducing firefighter exposure to hazards. The flow of this foam can be numerically or computationally simulated in order to gain a better understanding of its behavior, but rheology parameters are needed as inputs to produce accurate simulations. For this reason, this work studies the rheology of firefighting high expansion foam using a foam generator and Poiseuille –Flow Rheometer. Rheological parameters for foams with expansion ratios between 250-1280 are represented by the consistency index (k) and the power law index (n) due to the results show a strong agreement with the Power Law model for non-Newtonian fluid viscosity. Furthermore, experimental results show that high expansion foam behaves as a shear thinning fluid with a power law index around 0.4 and viscosities in the range of s 0.1 Pa-s and 0.042 Pa-s under shear rates between 44 ??-1 and 187.3 ??-1. INTRODUCTION High expansion foams are called to foams with expansion ratio greater than 200. Expansion ratio (??) is defined as the ratio between the volume of foam produced (i.e. volume of foam solution and volume of gas) and the volume of foam solution used (NFPA 2014). Because of its high expansion ratio, one of the most important application of high expansion foams is to fill or flood large spaces such as hangars, storage facilities and underground mines for fire suppression. The foam can fill large structures using small quantities of foam solution within a short time (Sthamer 2012) (Martin 2012). Although the specific high expansion fire suppression mechanism has not been understood on a quantitative basis, a possible mechanism is fuel isolation when the foam act as a physical barrier between oxygen and the flame. Furthermore, as a consequence of this contact water is evaporated, causing cooling of fuel and surrounding air. Besides, water vapor as product of water evaporation causes a dilution of oxygen concentration available to the fire (Fleming and Sheinson 2012). High expansion foam can be applied remotely by means of conduit pipes or in situ close to the fire. In most of the underground mines scenarios, fires have to be addressed remotely to reduce miner and firefighter exposure to the hazards (Smith et al. 2005). Although high expansion foams should not be blasted and must be deposited directly on the area of application because of their low density (Harding et al. 2016) sometimes it is complicated to apply it directly to the fire due to complex access areas at underground mines. In these cases, foam has to be applied far away from the fire. Despite of this fact there is a lack of knowledge in terms of rheological behavior of high expansion foam under high shear rates (Gardiner, Dlugogorski, and Jameson 1998). Furthermore, there are a few attempts to simulate numerically the high expansion foam flow due to the ignorance of its rheological parameters and its complex behavior. (Weaire 2008)."

Jan 1, 2018

By R. E. Turner

Hamersley Iron Pty. Limited, one of the world's largest iron ore producers, operates a 3.0 million tonne per year pelletizing facility at Dampier in Western Australia. The plant produces pellets for the export market using a blend of natural hematite fines from the Company's two mines at Tom Price and Paraburdoo. Processing includes fluidised-bed drying of the ore feed, open circuit dry grinding, disc balling and pellet induration in a travelling grate furnace of Dravo-Lurgi design.

Jan 1, 1980

By Pieter-Jan Kleiterp

Highwall mining is a mining method to extract coal from a final boundary in opencut mining, trench mining or contour mining. This boundary may have been reached because of economic constraints (economic strip limit) or geographic constraints, such as spoil heaps and rivers. Coal is mined from visible, horizontal, or near-horizontal coal seams by making rectangular, parallel, unsupported drives with an unmanned cutterhead and coal transport system. This is controlled from a mining unit, or launch frame, positioned outside the drive, in front of the highwall. Removal of overburden is not required or is limited to small quantities only.

Jan 1, 2010

By N. Djordjevic

Introduction The vibration energy that travels beyond the zone of rock breakage is wasted - all it does is cause damage and annoyance. Under favorable geologic conditions, this energy may travel many kilometers before it finally drops bellow the background noise level. This has forced the introduction of more restrictive limits to the allowable vibration levels. To maintain the profitability of a mine or quarry and to comply with environmental protection legislation, blasting needs to be performed in a more predictable way that will ensure that the final results are optimal in both mining and environmental terms. Minimization of ground and induced structural vibration is, therefore, a matter of good blasting practice -not just an attempt to avoid complaints from neighbors. A new approach to blast vibration minimization is presented. The method utilizes the existence of the local minimums in the frequency spectrum of single-hole blast vibration. The results are presented as a delay map showing maximum ground or structural vibration velocity for many combinations of interhole and interrow delays. A blast engineer can use this map to select an optimal combination of delays that will produce a low vibration velocity at a selected location and, at the same time, will be acceptable from the point of view fragmentation or muck pile shape. Response of structures A typical single-story building has two distinctive forms of vibration. The first form is a translatory vibration of the building superstructure (frame), and the second form is a flexural-bending vibration of the structural elements such as walls and floors (Siskind et al., 1980). Walls and floors will have several modes of oscillation. The most important is the fundamental mode of the vibration, as this mode will have the lowest frequency, the largest amplitude and will cause the largest deformations. The vibration of walls and floors is also a source of secondary vibration within a building, due to the movement of loose objects, e.g., furniture and wall fittings (Dowding, 1985). The subjective estimate of the amplitude of a vibration by the occupants of a house will be unrealistically high due to the effect of the secondary vibrations. It is now well recognized that human perception of ground vibration begins at levels that are far below those that will produce minor damage to the most fragile structures. In mining and quarrying operations, complaints regarding vibration levels tend to be determined more by human perception or annoyance rather than by observations of damage. Ground vibrations on the order of 0.08 mm/s (0.0032 ips) (Walter and Walter, 1979; Murray, 1987) can be felt, and they are often subjectively estimated to be about 100 times greater. Amplification of ground vibration in the structure depends on the amount of energy in the ground vibration spectrum that is in the vicinity of the structure's resonant frequencies together with the damping ratio of the structure at these particular frequencies. One way to avoid significant vibration amplification in a structure is to shift the dominant part of the ground vibration away from the resonant frequency range of the structure. The presented method allows for the selection of the optimum blast timing (interhole and interrow delay times) to minimize the resultant ground vibration amplitudes in a given frequency range. It also allows the selection of suboptimal, but still acceptable, blast delay times, which may be preferable from the point of view of overall blast performance. Determining frequency ranges of importance in structures In attempting to avoid amplification of vibrations in the structure, ground vibration amplitude of frequencies close to the resonant frequencies of the building needs to be minimized. The width of the frequency-minimization region is determined by the value of damping in the building. If the damping ratio is low, then the frequency-minimization region around the resonant frequency will be relatively broad. By shifting the dominant part of the ground-vibration energy into the frequency region much higher than the resonant frequency of the building (1.5 to 2 times), it is possible to achieve efficient vibration isolation of the building. In such cases, the structural dynamic amplification of ground vibration will be less than unity. The first step in this minimization process is the determination of the structural resonant frequency. From the frequency spectrum, it is possible to determine the resonant frequency of the structure. Sometimes the

Jan 1, 1998

By Manoj Kumar, Anil Kumar Singh, Prabal Patra, Ashish Agrawal, Souvik Ghosh, Subhashis Kundu, Kamma Ramakrishna Rao, Manish Kumar Gupta, Anindya Sarkar

The slag measurement systems in the cast house are very important. In the conventional method, the slag is granulated in a slag granulation system, and the slag flow rate is measured by the associated belt scale. However, in places where a slag granulation system is not available, the alternate approach is to deduce a theoretical calculation and develop the measurement because the commissioning of such slag granulation requires huge capital and has inherent geographical limitation. However, the theoretical approach suffers from several drifts and is far from the reality. In the present paper, we have innovatively engineered a sensor by designing the stellite-coated thermocouple that can measure the temperature of the slurry and placed it in such a way that the abrasive slag granules do not obstruct it, but we could measure the temperature of hot water, and further based on the thermodynamic approach, the slag flow rate is determined that can be compared with the theoretical approach. This approach of slag rate measurement is cost-effective and long-lasting.

Oct 2, 2023

By W. W. Mason

The United States began exporting coal in the late 1800'5, at first in very small quantities to Canada and beginning in 1897 and 1896, to the east coast of South America. Shipments to European countries began on a very limited basis in 1902 and these shipments increased gradually until World War One when shipments overseas increased from the 8 million tons per year level to 22 million tons. After the war exports dropped as fast as they had increased and, with the exception of exports to Canada, remained at very low levels until just after World War 11 when the United States again emerged as a major coal exporter. World War II left the coal industries of Europe in ruin. As the United States was the only country able to supply the large quantities of coal at reasonable prices needed for reconstruction of the European economy, the U. S. coal exports overseas expanded rapidly to 42.5 million tons in 1947. Additionally, we shipped 25 -2 million tons of coal to Canada In that year for a total export of 68.7 million tons. Unfortunately, that level was not reached again until 1957 when exports reached an all-time high of 76 .4 million tons- -a high I might add that has not been reached since.

Jan 1, 1980

By Hooman Askari-Nasab, AHLAM MAREMI, EUGENE BEN-AWUAH

In oil sands mining, tailings are voluminous unwanted byproducts generated from extracting the desired mineral from the mined ore. Dyke construction and backfilling activities require well-managed techniques to facilitate progressive reclamation at the earliest opportunity. This directly affects the sustainability and profitability of the mining operation. This research introduces a goal programming framework that simultaneously optimizes the (1) production schedule with limited duration stockpiling and directional mining, (2) dyke construction schedule, (3) size, shape and location of tailing cells and (4) mining and processing production targets. The results show that in creating in-pit tailing-cell designs, decreasing the mining-cell volume and increasing the number of mining cells improves the net present value (NPV) of the operation due to increased operational flexibility.

By S. Managi, M. C. Williams, N. H. Behling

Particle processing is a key to using solid particles in fuel cell applications. Selectivity with regard to reactivity, impurities, etc. is important feature and the treatment of particle surfaces could greatly impact the performance of direct carbon fuel cells. Solid fuel particles will become increasingly important in the future. Present energy conversion systems for solid fuels are too inefficient. New energy conversion systems for solid fuels with higher energy conversion efficiencies are possible. Fuel cell technology is a key-technology in these new conversion systems. The direct carbon fuel cell (DCFC) operates on carbon particles obtained from a variety of solid fuel feedstocks. The DCFC is the only fuel cell designed to directly oxidize carbon particles in a special anode chamber. The particles are generally graphite structure with high purity. The electrolyte used is the high temperature solid oxide, molten carbonate or hydroxide electrolyte. Since a pure stream of CO2 is produced the stream can easily be sequestered and disposed. Pure carbon dioxide produced as a by-product would also have a market in many industries. A well-defined technology roadmap identifying key research and development (R&D) issues is necessary to provide a framework for the development of these systems and to prevent entrenchment in inherently inefficient technologies. This review paper describes the direct carbon fuel cell and its system, how it works, the developmental status, the characteristics of the carbon particles needed, and the research and development issues for the technology. INTRODUCTION The DCFC has been under development for many years. It was researched as early as 18961), but an intense research and development is necessary to realize its potential. William W Jacques, a US electrical engineer and chemist, described a DCFC in 1896 in US Patent 555511 for a “Method of converting potential energy of carbon into electrical energy”. Jacques used coke electrodes in a molten NaOH electrolyte. Molten carbonate fuel cell (MCFC), solid oxide (SOFC) or hydroxide electrolyte (AFC) technologies can be used as the basis for the DCFC technology. A schematic of the direct carbon fuel cell in the MCFC mode is shown in Figure 1. The molten carbonate fuel cell operates at approximately 650°C (1200°F). The high operating temperature is needed to achievesufficient conductivity of the carbonate electrolyte, yet allow the use of low-cost metal cell components. A benefit associated with this high temperature is that noble metal catalysts are not required for the cell electrochemical oxidation and reduction processes. For the hydrogen reaction the half-cell electrochemical reactions are

Jan 1, 2019

By Matthew Goff, Russell Lutch

The Great Lakes Water Authority (GLWA) operates the largest regional water authority in the State of Michigan. Two of the tunnels supplying raw water to the system from the Detroit River are the Springwells and Northeast Tunnels. The existing 70- to 90-year old concrete lined tunnels have experienced distress and cracking over their life requiring non-structural repairs to sections of the tunnels. For the repair, an interior stainless-steel segmental liner plate system has been designed to restore the watertight capacity of the tunnel liner and resist the exterior hydrostatic groundwater pressure in a dewatered condition. The team is utilizing a “wet repair” approach to perform the necessary repairs while the tunnel remains fully flooded and operational. To test and validate the tunnel repair approach, a full-scale mock-up of the proposed repair has been performed using underwater equipment and divers.

Dec 1, 2022

By Darold Woodward, Stefan Haydn, Petr Pospisil

Most fatalities in tunnel fires are caused by the spread of toxic smoke. Controlling the spread of smoke is crucial to provide a survivable environment for emergency egress. A properly designed and tuned feedback control loop is required to achieve a target flow that is slow enough to allow pedestrians to escape under different boundary conditions. Feedback control loops are also helpful in optimizing energy consumption under moving traffic conditions. A reliable feedback flow control system requires sophisticated engineering knowhow and experience, careful selection of instruments and controlled variables, and thoughtful implementation from design through field testing and commissioning.

Dec 1, 2022

By R. K. Mehta

An accurate, efficient and stable computation of the mill matrix function (eAt) is needed where mill matrix (A) is a real general matrix. Two important modeling cases in comminution where such need arises are: Heterogeneous comminution behavior of multi-component ores and ultra-fine grinding involving simultaneous attrition and fragmentation breakages. This paper presents the application of a novel splitting method in conjunction With similarity transformation technique in the form of "product formula" which is found to work in all cases and uses a most aggravating, yet interesting property of the matrix exponential in a restricted sense. Results are presented showing that this method can yield solution as accurate as those obtained With an analytical technique. The utility of this computational approach is demonstrated by parameter estimation analysis using a distributed component model in the liberation area through computer simulations.

Jan 1, 1992

By R. Wisniewski, S. Schafrik

Every underground coal mine in the United States must deploy and operate a wireless communication and electronic tracking system. This paper addresses the reliability and availability of an installed tracking system and the communications infrastructure that supports it. This paper assumes that the tracking system uses the communication system to perform its operation. A particular interest is the requirements for the systems to operate continuously without failure after a mine disaster for 24 hours, and the requirements in the MINER Act for the tracking systems to be “functional, reliable and calculated to be serviceable” and the communications systems “redundancy.” These requirements imply a certain reliability and availability. This paper describes a quantitative way to assess these systems requirements, using tools that are available to and commonly used by the reliability, maintainability and availability community.

Jan 1, 2014

By John T. Atkins

Utah International's Shirley Basin Mine is located in the Southeastern High Plains of Wyoming at an elevation of about 7,100 feet. The Shirley Basin area is a gently rolling semi-arid land. The uranium ore zone occurs at depths ranging from 270 to 350 feet below the surface. Overburden consists of poorly consolidated sandstones, siltstones, and clays. Underground mining was begun in 1960. Conditions were made difficult by high rates of water inflow and ground support problems. The development of a solution mining I or in-situ leaching technique allowed underground operation to be abandoned in 1964. Solution mining provided limited production from 1963 to July 1970. In January, 1969, large scale development of open-pit mining was begun. A 1,200 ton per day mill went "on stream" in March, 1971.

Jan 1, 1973

By James B. Lincoln

The Schaffer linear kimberlite complex and Aultman kimberlite diatremes comprise a major part of the State Line kimberlite district of Colorado and Wyoming, which encompasses approximately 200 sq mi (500 km2). The district is located along the eastern flank of the northern Front Range and is underlain prin- cipally by Precambrian granites (approx. 1.4 b.y.) which have been intruded into an older (approx. 1.75 b.y.) metamorphic complex. The kimberlite occurrences are Devonian in age and are related to older Precambrian linear structures. The Schaffer kimberlite complex is a dike or fissure system with enlargements or blows developed at the intersections of cross faults; the two Aultman occurrences are diatremes. Kimberlite within the Schaffer complex is predominately grey to green phlogopite-calcite kimberlite breccia and tuffisitic breccia. Carbonate is abundant in some phases. Inclusions of host granite are common and locally abundant. Upper mantle peridotite, pyroxenite, and eclogite and lower crustal granulite xenoliths are present at many localities. Four phases of tuffisitic kimberlite breccia occur in the Aultman diatremes. These breccias are characterized by high carbonate and serpentine contents. Xenoliths of upper crustal granite, lower crustal granulite, and upper mantle assemblages are abundant locally. Lower Paleozoic sedimentary rock xenoliths are also abundant in the Aultman diatremes but are absent in kimberlite of the Schaffer complex. From 1979 through September 1982, Cominco American, Inc., conducted geologic mapping, petrographic studies, geophysical surveys, geochemical surveys, and auger drilling in the Schaffer-Aultman project area as part of an extensive evaluation program of kimberlite occurrences. Forty bulk samples (approx. 8,000 metric tons) were excavated from the occurrences and then were processed for diamonds at Cominco American's heavy media separation and diamond recovery test plant at Fort Collins, Colorado. Indicated grades from the Schaffer and Aultman kimberlites range from approximately 0.5-1.0 carat per 100 metric tons and as such, the occurrences do not appear to approach economic viability at this time.

Jan 1, 2013

By K. Rushdi, B. E. Abulnaga

The conventional Froude number is blind to the presence of solids, their density and their concentration in a stream of slurry mixture such as tailings flowing in an open channel. This often leads to rough approximations of subcritical, critical and supercritical regimes, based on one phase flow Froude number, limiting subcritical to a value smaller than 0.8 and supercritical to values above 1.4, as proposed in the past by Green, Abulnaga and other authors. While acceptable for small flows, such approximations can be uneconomical for the larger flows encountered in some modern plants that treat up to half a million t/day. A review of concepts of a densimetric Froude number sheds some light on the effect of solids on stratification prior and subsequent to a hydraulic jump. While the approach is heavily borrowed from modern sedimentology, it provides a useful tool to designers of large launders or open channel tailings systems. These concepts are reviewed with some practical examples.

Jan 1, 2013

By S. S. Klima, D. E. Pollock, J. A. Organiscak

"Airborne respirable coal dust capture by water sprays or wet scrubbers has been studied and developed over many decades as an engineering control to reduce dust exposure in coal mines and combat coal worker pneumoconiosis. Empirical relationships and deterministic models for particular dust capture experiments have previously been devised to show the key parameters involved in airborne coal dust capture. Many of the results from these models show that the significant parameters related to airborne dust capture are water spray pressure, water quantity, water droplet size, relative water droplet-to-dust particle velocity, and total operating air pressure of the scrubber. However, many airborne dust capture efficiency relationships and models developed for particular experiments cannot be readily applied to forecast the dust collection efficiency of different spray and scrubber design configurations, which rely on several key dimensional engineering measures. This study examines engineering measures from previous water spray and wet scrubber experiments conducted by the U.S. National Institute for Occupational Safety and Health (NIOSH) and the U.S. Bureau of Mines (USBM) to develop empirical models for wet collection of airborne dusts. A dimensionless empirical model developed for predicting airborne dust capture efficiency of water sprays and wet scrubbers is presented. IntroductionWater sprays have been one of the earliest mainstay engineering controls used to suppress respirable dust in underground coal mines. Some of the earliest reports of water spray usage on continuous mining machines indicated respirable coal mine dust reductions of 20 to 60 percent (Kobrick, 1970). Not long after the enactment of the 1969 Coal Mine Health and Safety Act, the U.S. Bureau of Mines (USBM) and others conducted extensive research into water spray and wet scrubber systems to control respirable dust in coal mines. The primary aspects of water spray dust control included prewetting for dust prevention, localized ventilation redirection and airborne dust capture, which are summarized in handbooks or best-practices guides (Kost, Yingling and Mondics, 1981; Kissell, 2003; Colinet et al., 2010). Initially, underground studies were conducted to identify the primary sources of dust during the mining processes and effective dust controls (Courtney, Jayaraman and Behum, 1978; Jankowski and Organiscak, 1983). Laboratory research systematically studied ventilation and airborne dust capture effects of water sprays and scrubbers to improve their application in underground coal mines (Tomb, Emmerling and Kellner, 1972; Divers and Janosik, 1978, 1980; Grigal et al., 1982; Ruggieri et al., 1983; Jayaraman, Jankowski and Kissell, 1985; Volkwein, Ruggieri et al., 1985; Jayaraman, Schroeder and Kissell, 1986; Divers, Jankowski and Kelly, 1987; Jones and James, 1987)."

Jan 10, 2018

By A. Moergeli, Philip Sander, John Reilly

"SUMMARY While the basic elements of risk management, including probability, consequences, risk registers, mitigation measures, etc., are now well understood, the process to include correlation, dependencies and linkage of risks and risk scenarios is less well defined and not well understood. To perform accurate and complete risk analysis and risk management, it is necessary to include correlation, dependencies and linkage between risk events, as well as risks that may occur multiple times. In this way, owners and contractors can more accurately determine risk-based costs, risk impacts and risk mitigation strategies. This paper will outline methods to deal with correlation, dependencies and linkage and will consider risks that may occur multiple times. Practical result comparisons – with or without these elements – will be presented. INTRODUCTION We believe the reader is familiar with basic concepts of risk, risk management and mitigation and the use of probabilistic cost-risk processes versus deterministic ones (Reilly et al. 2015; Sander et al. 2015). The probabilistic approach, compared to the simpler and more common deterministic approach (unit prices times unit costs plus a contingency), offers more useful information with respect to the range of probable cost as well as cost “drivers” and better quantifies the effects of risks, opportunities and variability – which improves understanding, leading to a better potential for profit (or loss) for contractors and added value for owners. In this context, a valid and sufficient quantification of correlation, dependencies and linkage of risk events, plus the impact of risks that may occur multiple times, is essential. Components of Cost Estimates – Base Cost, Risks and Other Uncertainties The components of cost that need to be correctly addressed in an estimate include (Moergeli et al. 2015): •,Base costs – the costs that will result if “all goes according to plan” (Reilly 2004) •,Risk costs – the resulting costs of threat and opportunity events, if they should occur •,Escalation costs – costs resulting from normally expected inflation with variability •,Other uncertain costs – costs that result from other events, normally external to the project team’s control, which may include unanticipated events, politically related changes and “black swan” events (Talib 2007)"

Jan 1, 2016

By Y. V. Vasylchuk

This paper presents an algorithm for optimizing the classification of surface mine material subject to excavating constraints. High-resolution expected profit models are input and optimized to classification maps subject to site-specific rectangular excavating constraints. This optimization problem defies traditional closed-form analytical solutions; a practical heuristic algorithm has been developed to quickly determine the optimal final destination for the material subject to realistic constraints. The optimization is fast and generates results that achieve up to 98–99% of the total expected profit achieved with free selection. This algorithm provides a fast viable option for practical application in short-term grade control and in managing multiple realizations in long-term resource estimation.

By K. Sasaki, H. Miyakoshi, K. Mashiba

A ventilation analytical system adapting nodal pressure method using skyline modified Choleski's decomposition scheme for network-flow analysis and a new practical system to estimate various thermal air conditions has been developed. The quasi-linear equations for solving steady-state network airflow have been described using the connective function in general forms. The skyline modified decomposition scheme has an advantage on rapid convergence and the sake of computer memory space com- pared with other schemes. The key part of the analysis for climatic conditions through network airways is how to estimate the temperature of the airway rock-surface with partly or full wet condition. A practical and simple solution without any iterative calculations for its estimation has been proposed. This new solution is applicable to practical ranges of airflow temperature, humidity, rock thermal properties and wetness. The present analytical sys- tem have been successfully applied to a ventilation simulator named "M1VENA"developed by authors.

Jan 1, 1996

By R. Hogg, T. F. Dumm

Procedures for particle size analysis on respirable dust from coal mines have been evaluated. Using respirable dusts dispersed in a laboratory dust chamber, size distributions measured using cascade impactors have been com- pared with the results of a variety of laboratory sizing methods performed on samples collected on filters placed side-by-side with the impactors. The laboratory techniques included centrifugal sedimentation, laser diffraction/scattering and automatic particle counting. The general agreement among the various methods was very good, with systematic differences which can be attributed to the different definitions of size used. Simple conversion factors have been obtained which can be used to transform the laboratory data to equivalent aerodynamic sizes. Similar comparisons have been made on samples collected in underground coal mines. Again, the results are in quite good agreement although small discrepancies were observed in some cases. These have been attributed to some degree of agglomeration in the airborne dust, leading to slightly coarser apparent distributions in the impactor samples.

Jan 1, 1987