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By Charles H. Dowding

INTRODUCTION "On many projects, the tendency is to drop interest and support of the geological service as soon as it seems safe. That . . . is a short-sighted policy . . . It would be of further service perhaps to learn whether predictions were reasonably true to life." --C.P. Berkey, 1938 (3) This paper quantitatively compares predicted and encountered shear zone size and location and rock type for tunnels in the Colorado Mineral Belt. The Colarado Mineral Belt is composed of igneous formations with associated metamorphic rocks and faulting. As such, it represents the most complex of provinces for at-grade predictions (27). Shear zone and rock type data are assumed to be statistically homogeneous because of the common geology of the seven tunnels. It is often felt by geologists and engineers that the amount of information from which a geological model is created is so low that any statistical inferences are unstable. In other words, the addition of new data may drastically alter the means and variances suggested by the model. Therefore, predictions are rarely couched in quantitative statistical terms but modified with "probably," "most likely" or "possibly." Comparison of predicted and encountered data from past geological models will permit the "probably's" to be quantified and distilled from the art of geological prediction. To date, two other studies of the validity of predictions have been made (26 and 16). Together, these two studies indicate that

Jan 1, 1976

By A. Anttila, S. Persson

The grinding mill is probably the most common unit operation in mineral processing. There is, however, much that can still be done in the way of optimization. This paper discusses the results of a well-controlled pilot-scale test in which the performance of a tumbling mill equipped with a conventional rubber lining and lifter bars was compared to a tumbling mill equipped with a smooth rubber lining of the magnetic type. The results indicate that the smooth lining is about 14% more effective with respect to energy consumption. By optimizing the size of the grinding media, the mill capacity can be increased in many grinding operations. In this specific case, grinding with a -20-mm ball charge required 26% less grinding energy than grinding with a -30-mm ball charge. The energy savings can, in most cases, be converted to an increase in capacity. The wear of the grinding media is difficult to assess over a short test period, but the results suggest that the wear is somewhat less when a smooth lining is used. A determination of the wear of the linings was not included in this study, but it is generally accepted that the use of magnetic linings reduces the lining costs dramatically. Computer simulation using the Millsoft code developed by Mishra et al. confirms and explains the increased effectiveness of comminution when a smooth lining and smaller grinding balls are used.

Jan 1, 2000

By Y. Xi, T. M. Yegulalp

An availability approach for determining the capacity of a major Bucket Wheel Excavator (BWE) system to be used in the Yuabaoshan Surface Coal Mine in China is presented in this paper. Based on previous studies on other BWE systems for delay times due to internal and external causes and a four-level maintenance and repair schedule, a model was developed, taking into account all random failures, to present a fast and simple solution to this highly complex problem. A procedure employing the Markov renewal theory for determination of the distribution of random failure times and failure rate of the whole system, as well as some other factors useful for calculation of the overall system capacity, are discussed.

Jan 1, 1994

By W. J. Dolinar

The U.S. Bureau of Mines implemented the Fe2+ /Fe3+-SO2 anode reaction in a Cu electrowinning cell with full-size electrodes. Electrowinning was conducted using industrial electrolyte at 258 A/m2 (24 A/ft2) and 40 'C. Manifold injection of electrolyte provided circulation between the electrodes. Five-day operation using an optimized manifold gave an average cell voltage of 0.94 V at 89% current efficiency, which amounted to an energy savings of 2.82 MJ/kg (0.355 kW-hr/lb) compared to conventional electrowinning. Acid misting was completely eliminated, and SO2 concentration 23 cm (9 in.) above the cell averaged 0.06 ppm.

Jan 1, 1995

By Y. Luo, S. S. Peng

Several issues deserve further attention to improve subsidence prediction accuracy. These include: subsidence initiation and development over a setup entry area; subsidence development after face stop; and subsidence over chain pillar. An intensive subsidence monitoring program has been carried out over several longwall panels. A large amount of subsidence data has been collected, analyzed and solution techniques developed. In this paper, some of the measured data. data analysis techniques and the developed prediction methods are presented.

Jan 1, 1992

By Atta Ur Rehman, Kwame Awuah-Offei

This paper examines the effect of bucket geometry (cutting-blade profile, floor profile and blade thickness), speed, motor power output and muckpile particle sizes on bucket penetration and draft for rubber tire loaders. The work uses a 1:16 scale model of a load-haul-dump (LHD) in full-factorial experiments to examine the effect of the variables on penetration and maximum draft. The results show that speed and motor output are positively correlated with penetration and draft, and muckpile particle size is positively correlated with penetration and negatively correlated with draft (p < 0.0014).

By L. Evrard, M. Van Camp, J. Y. Yen, R. G. Reddy, D. Mantha

Viscosities of two industrial lead blast furnace slags have been experimentally determined as functions of composition and temperature. A Brookfield viscometer with alumina rods and crucibles were used. Experiments were carried out between 1200 and 1573 K in an argon atmosphere with up to 5% addition of FeO, MgO, and SiO2 to the slags. Results showed that 1) the viscosities of two slags decreased with increase in temperature; 2) addition of FeO decreased the slag viscosities; and 3) addition of MgO and SiO2 increased the slag viscosities. Use of the above slag compositions with the addition of FeO is recommended for successful lead smelter operation.

Jan 1, 2005

By Paul R. Smith

The theoretical requirements for the flotation d large particles are discussed. A flotation machine is described which has components which meet many of the theoretical requirements for the flotation of large particles. The machine&apos;s salient features include multiple fine-bubble attachment, froth level feeding, quiescence, shallow depth, and short flotation time. Test conditions and results are presented for the laboratory flotation of 10 mesh phosphate, 4 mesh potash, and 1/2 inch coal. In addition, test conditions and results of pilot plant flotation of minus 14 plus 35 mesh phosphate and minus 14 plus 150 mesh phosphate are also presented.

Jan 1, 1969

By J. A. Marts, R. C. Gilmore, Jr. Bogin, S. Saki, J. F. Brune, J. W. Grubb

"Researchers at the Colorado School of Mines have studied the influence of headgate side ventilation controls near the longwall start-up room on the formation of explosive gas zones (EGZs) in underground coal longwall bleeder ventilated gobs. In a project funded by the National Institute for Occupational Safety and Health (NIOSH) researchers developed a Computational Fluid Dynamics (CFD) model to study the formation of methane-air mixtures in the gob, start-up room, and bleeder entries. The relative change in size and location of EGZs are examined in response to ventilation controls in the headgate side bleeder entries near the start-up room. Modeling suggests that adjustments to the ventilation controls can be made to minimize the size of the EGZ. However the EGZ may form in or around active working areas regardless of the ventilation control settings. Research found regulators on the crosscuts into start-up room and first entry inby can force air into to crosscuts outby the start-up room causing more air to flow through the gob. INTRODUCTION Underground longwall mine ventilation systems may operate with either a bleeder ventilated gob or a progressively sealed gob. Bleeder ventilated gobs must meet the standards for safe operation of the bleeder system by examining bleeder system effectiveness. As defined in the United States Mine Safety and Health Administration (MSHA) Program Policy Letter (PPL) No. P13-V-12 (MSHA 2013), the pillared area or gob is “any area where a reduction in pillar size has occurred during retreat mining” and includes the “caved and broken material, the interstices within the caved material, and the open spaces surrounding the caved material.” The PPL further states that the intended purpose of ventilating the gob is “to protect active workings from the hazards of methane accumulations …” The requirements for operating a bleeder system as stated in The United States Code of Federal Regulations (CFR 2013) Title 30 §75.334(b) is to pass ventilation air though the gob “and to continuously dilute and move methane-air mixtures [from the gob] away from active workings and into a return air course …” where the concentration cannot exceed 2 percent methane (CFR 30 § 75.323). Further clarification of the bleeder system as described in the PPL states the following: “A bleeder system includes the area from which pillars are wholly or partially recovered, bleeder entries, bleeder connectors, and all associated ventilation control devices that control the air movement through the area. Bleeder entries are air courses designed and maintained as part of the bleeder system.”"

Jan 1, 2015

By Donald R. Williamson

Statistical studies at Cyprus Pima Mine indicate that samples from 22 blastholes are necessary for determining average copper grades, within a desired range of precision, for mine-model blocks by arithmetic averaging. The average number of holes in such blocks is 14. Many considerations show that more holes will not be drilled for sampling. A way to determine block grades more reliably than by" arithmetic averaging was sought. Thus far arithmetic averaging has proven to be the best procedure for the particular operation characteristics despite the small number of samples. It naturally follows that expenditure of great effort in sampling blasthole cuttings is unwise.

Jan 1, 1977

By T. J. Close

The Silver Peak Range North Wilderness Study Area was deleted from the list of US Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the US Bureau of Mines mineral investigation of the wilderness study area which found indications of precious- and base-metal-resources. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Bureau examined 13 mineralized sites, most of which were previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak mining district to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz and calcite with gold, silver, and base-metals. At the surface, these veins are poorly defined. Exposures of the more than forty veins examined were as thick as 17 ft and as long as 1000 ft. Samples from these veins contained significant amounts of precious- and base-metals-as much as 0.02 oz per ton gold, 2.1 oz per ton silver, 1.0% copper, 2.6% lead and 0.4 % zinc. No vein large enough or of high enough grade to be classified a mineral resource was disclosed by the sample data. However, most do have indications of precious- and base-metal-resources at depth. Subsurface exploration of some of the veins is recommended.

Jan 1, 1995

By Changhong Huang, Y. J. Wang

This paper describes the formulation of mine ventilation network optimization as a standard nonlinear programming problem and the solution of the problem using the generalized reduced gradient (GRG) method. In general, the GRG method is regarded as one of the most effective and efficient methods for solving large-scale nonlinear programming problems. The variables considered in the network optimization include air quantity, regulator pressure loss, and fan pressure for each branch. Each of the variables is constrained by lower and upper bounds. This facilitates proper assignments of ventilation requirements and provides a great flexibility to include various situations encountered in mine ventilation. The objective of the network optimization is to minimize the overall air power consumed by or supplied to the network; whereas the constraints are, in addition to the variable bounds, the two fundamental network laws: Kirchhoffs voltage law and Kirchhoffs current law. A computer program has been developed based on the GRG method for the network optimization. An example of network with 18 branches, 8 regulators and 3 fans is included for illustration.

Jan 1, 1993

By D. A. Norrgran

The term "secondary recovery" has recently brought on a new meaning in view of the depletion of natural resources, energy conservation, plant optimization, and the environmental consciousness that has led to hazardous waste management, recycling, and secondary processing. Many secondary recovery processes are being developed applying mineral processing technology. Gravity separation, magnetic separation, and flotation have all emerged as implicit methods for recovering residual values from various process streams and hazardous constituents from waste streams. Recently, a technique for concentrating metallics has been successfully reintroduced. Although the concept of the eddy-current separator was developed over a century ago, (Patent 400317 issued to Thomas Edison on March 26, 1889) it was not until this last decade that it gained prominent acceptance. The evolution of permanent magnets has provided a cost effective alternative for the generation of high intensity magnetic fields. High energy permanent magnets have substantially reduced the capital and operating costs over the electromagnetic circuits employed in antecedent eddy-current separators. Specifically, in recent years, the strength of permanent magnets has increased several fold with neodymiun-boron-iron rare earth magnets now providing an energy product of 35 million gauss-oersted. Figure 1 shows the evolution in the strength of permanent magnets. The development of these rare earth magnets has led to the design of circuits possessing a magnetic force an order of magnitude greater than that of conventional permanent magnetic circuits.

Jan 1, 1991

By DIONISSIOS T. HRISTOPULOS, JUAN DIAZ, Kray Luxbacher, Steven Schafrik, Zach Agioutantis

Explosions in underground mining due to methane gas have been the leading cause of incidents and fatalities in the mining industry. The main objective of this research is to develop a forecasting methodology for methane gas emissions based on time series analysis. Methane time series data were retrieved from atmospheric monitoring systems (AMS) of three underground coal mines in the United States. The AMS data were preprocessed and statistically evaluated to explore the potential autocorrelation of methane gas. It was concluded that the autoregressive integrated moving average (ARIMA) time series model used in the one-step-ahead forecasting mode provides accurate estimates that match the increase or decrease of the methane gas emission data.

Feb 1, 2023

By William Gleason

There was a time, not too long ago, when the most daunting challenges facing those in the mining and mineral processing industries could be solved through better technologies and better practices. But now the challenges that come from the actual acts of mining and processing are just part of the bigger picture. SME?s Colorado Section of the Mineral Processing Division (MPD) hosted its 63rd annual meeting at the Broadmoor Hotel in Colorado Springs, April 25-27 and, while the conference had its fair share or mineralolgy and processing presentations that were heavy on the technical side of things, this year?s conference was also focused on the issues of permitting, regulation compliance and legislative issues. The so-called ?softer? issues, that, if not addressed, can lead to very real and very hard challenges. Under the theme ?Mine your own business - permits, startups, expansions and resources,? even the most dedicated metallurgists were drawn into the discussions of politics and legislation, and how those issues affect their business. Fittingly, Colorado Mining Association (CMA) president Stuart Sanderson was honored with the Arthur C. Daman Lifetime Achievement Award. Sanderson, an outspoken proponent for the mining industry in Colorado and beyond, also presented the keynote address to the lunch crowd where he spoke about framing public opinion toward mining and the efforts of the CMA to move the public opinion dial in a direction more favorable to mining. Sanderson explained that Colorado, once a Republican stronghold, turned after 2002 and now is controlled by Democrats who are traditionally less supportive of the mining industry. Sanderson said the deciding factor in the power shift was money, as supporters of Democrats outspent Republicans in the most recent election cycles. CMA has done its part to keep mining going in the state with a broad marketing campaign that was outlined by Sanderson.

Aug 1, 2013

By Yi Luo, FENGLIANG WU

Mine gob has long been a safety concern in the coal industry due to the air flowing through the gob area. Therefore, knowledge of the airflow distribution and locations of hazard zones in longwall gob is important to prevent and control these hazards. Due to the inaccessibility of mine gob, many numerical studies have been performed to simulate gob air leakage using computational fluid dynamics (CFD) programs, but most of the studies isolated the gob from the mine ventilation network (MVN) with only predefined pressure boundary conditions. The MVN is, in fact, not static in a dynamic longwall mining process, and it consequently changes the boundary conditions and the gob flow field (GFF). Therefore, the MVN should be incorporated in the CFD model to prescribe the transient boundaries. However, it is very challenging to couple the 1D MVN and the 2D/3D GFF to make the mine ventilation simulation realistic. This research uses a proposed novel finite tube method (FTM) to couple the MVN and GFF. In the FTM, the GFF is discretized into a finite number of flow tubes, each of which is formed by two adjacent streamlines. These tubes connect the MVN into a new coupling network. Based on the FTM, a model for gas migration in gob is established for delineating the hazard zones of explosive methane concentration and spontaneous combustion.

By Miguel Reyes, Chenming Zhou, MATTHEW GIRMAN

This paper is aimed at helping the mining industry to better understand the challenges posed by electromagnetic interference (EMI) and to promote electromagnetic compatibility (EMC) in underground coal mines. The paper begins with a review of EMI standards in other industries, then presents some representative examples of EMI instances that have occurred in the mining industry, followed by a literature review of published EMI research in mining and, finally, a discussion on mitigation strategies and practical considerations related to EMI in mining.

By Wei Victor Liu, Omer Faruk Ugurlu, Chengkai Fan, Bei Jiang

Accurate prediction of truck productivity plays a pivotal role in improving the efficiency and profitability of openpit mining operations. This paper proposes a deep neural network (DNN) model to overcome the challenge of predicting truck productivity in openpit mines. The prediction model was built using eight variables and was optimized by considering different train-test split ratios, numbers of hidden layers and neurons, and activation functions. The proposed model’s performance was evaluated using various metrics and compared with other commonly used machine learning algorithms. The results showed that the proposed model outperformed traditional machine learning models by achieving higher prediction accuracy. Moreover, a single-variable sensitivity analysis showed that haul distance is the most influential variable for predicting truck productivity. This study marks a pioneering effort in employing DNN to predict truck productivity in openpit mining, signifying a notable advancement in the field.

Jul 1, 2024

By F. F. Peng, Y. Xia

In modeling of hindered-settling bed separators, the published separation mechanisms are based on differences of particle density and size distributions, without the details of complexity of particles-liquid interactions. A fluid dynamic model for the separator is developed using Euler-Lagrange approach of Computational Fluid Dynamics (CFD). Fluid motion is obtained from solving the movement of liquid governing equations. The damping effect on flow pat-terns caused by the movement of particles resulted in liquid-particle coupling is included in the model. Effects of particle size, and particle density compositions, feed rate, feed water flow rate, upward fluidizing water flow rate, etc., are simulated in the 2-D separation model. Flow pattern effects on the separation of fine particles in the separators with center downward-flow and side cross-flow feed systems are investigated.

Jan 1, 2004

By Verya Nasri, Behrouz Esmaeilkhanian, Mohammad Motallebi

Réseau Express Métropolitain (REM) is the new Light Rail Transit (LRT) network of Montreal, Canada. This new LRT network uses a century-old Mont Royal Tunnel (MRT) to connect Downtown Montreal to the north side of the Island of Montreal by passing through Mount Royal Mountain. This railway double track horseshoe tunnel is approximately 5 km (3.1 mi.) long, 8.8 m (29 ft.) wide and 5.5 m (18 ft.) high, with a constant 0.6% grade. Due to different geological characteristics of the surrounding ground, varied from hard rock to soft soil, different cross sections and excavation methods were adopted for construction of this tunnel. In order to use MRT in the modern transit system, the tunnel needed to be inspected, rehabilitated and be compliant to the recent safety standards. This paper presents a summary of history and characteristics of the existing tunnel plus the implemented steps to upgrade the tunnel. It includes the details of the structural inspection and rehabilitation methods of the tunnel. Further, this paper summarizes the procedures for the space proong, construction of the separation center wall, and the tunnel enlargement. It also describes parts of complications encountered during the construction and solutions implemented to tackle these issues.

Jun 23, 2024