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By H. Fayed

Two-phase (water and air) flow in a self aerated WEMCO flotation machine has been investigated using computational fluid dynamics (CFD). A 0.8 m3 model is considered. The flow is modeled by Euler-Euler approach, and transport equations are solved using a commercial software ANSYS-CFX5 [1]. Because of the lack of circumferential periodicity in this machine, the entire machine is modeled and unsteady simulations are conducted in the whole volume of the bulb. Uniform bubble diameter is specified, and the effects of bubble diameter are determined by conducting simulations for three diameters of 0.5, 0.7, and 1.0 mm. The unsteady air flow rate through the machine is predicted as an outcome of the simulations. Air volume fraction contours and velocity field in different parts of the machine are presented and discussed.

Jan 1, 2012

Seven legendary figures of American mining will be enshrined in the National Mining Hall of Fame in ceremonies on Saturday, Sept. 7 at the Little America Hotel in Salt Lake City, UT. The 15th annual induction banquet will begin with a reception at 6 pm, followed at 7 pm by the dinner and the program. Of the seven inductees, one is living. He is Alexander Murray (Bud) Wilson, 80, of Los Altos, CA. Wilson led Utah Construction (later Utah International) to become one of the world’s most diversified and successful mining companies in the 1960s and 1970s. It was acquired by General Electric in 1976.

Jan 1, 2002

By Sunil Bodakunta, Sreenivasa Rao Islavath

The abstract highlights the importance of determining the optimum line of extraction in continuous miner workings for improved safety and productivity. The study investigates three extraction techniques (diagonal, straight line along strike, and straight line along dip-rise) using 3D numerical modeling. The dip-rise extraction technique is found to be optimal due to lower stress and displacement, leading to a higher safety factor. The research also develops a continuous miner stability index (CMSI) to predict working face stability based on mining depth and pillar width-to-height ratio.

Apr 28, 2022

By J. Chilton

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. Currently there are no techniques or instruments to accurately measure airflow inby the mouth of the ventilation curtain or tubing. Tests conducted in the NIOSH ventilation test gallery compare the data provided by one-, two-, and three-axis ultrasonic anemometers. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face.

Jan 1, 2007

By S. Assemi

Interaction forces between a hydrophilic silica particle and an air bubble were measured by atomic force microscopy using simplified model systems with deionized water and dilute KCl solutions. Contributions from the hydrodynamic force were minimized by using a low piezo speed. Particle-bubble separation distance and the bubble spring constant were calculated from linear regression of the piezo extension versus cantilever deflection. The bubble surface potential was then estimated from fitting the AFM-measured forces to the Hogg-Healy-Fuerstenau (HHF) model, using the surface element integration (SEI) method. Surface potentials obtained for the bubble at a low applied force were comparable with the literature data, suggesting that the simplified model used here can give a reasonable estimation of the bubble surface potential under moderate applied forces. Interaction forces between a silica particle and an air bubble were also measured at different locations on the air bubble surface. The force curves obtained at the edges of the bubble fitted very well to the theoretical force curves regardless of the applied force, while curves obtained at the center and halfway to the center, were more difficult to fit, in particular at higher applied forces (> 13 nN), suggesting that force curves obtained at the edges of the air bubble might be less prone to deformation effects.

Jan 1, 2008

By Nikolas K. Sokol

Underground construction often requires working within a very congested urban environment, including excavating shafts adjacent to highly sensitive and multistoried structures, sometimes even within such structures. Shafts adjacent to heavily loaded column footings are often required due to space constraints. Invariably, footing surcharges must be considered during the design of shaft rock reinforcement. Rockwedge stability evaluation reveals that column surcharges can greatly impact the ability to meet the desired factor of safety. Design methodologies and examples to deal with these special circumstances are presented.

Jan 1, 2008

By R. L. Zick, D. C. Finn

Introduction The high-density sludge process was originally developed by Bethlehem Steel Corp. for use on acid mine drainage (AMD) and diluted waste pickle liquor discharges requiring continuous chemical-treatment. This work began in the early 1970s and was first put into practical use around 1973. To date, there are approximately 15 operating systems that have been installed to treat mine drainage in the United States. In addition, there are another 10 systems installed outside of the United States. The dense-sludge process is an innovative and improved method for treating acidic metal-bearing streams in a manner that minimizes the volumetric generation of sludge for disposal. The technology utilizes a sludge-recycle process that forms particles with a low affinity for water. These particles are unlike conventional metal hydroxide solids that contain tightly bound interstitial waters. Typical acid mine drainage streams contain high sulfate concentrations that combine with calcium ions in lime-based treatment systems to form gypsum crystals. Compared to the form generated in conventional lime treatment systems, the physical form of the gypsum is radically altered when the dense-sludge process is utilized. The characteristics of the metals particles are also changed in this process, as the metal hydroxides are converted to metal oxides. The dense-sludge particles settle faster, dewater more readily, are more easily pumped and hold much less water than conventional precipitates. In some cases, because the metal content of the sludge is more concentrated, it can be economically recovered. In general, the conventional and dense-sludge treatment processes are very similar. The changes required to implement the dense-sludge process are minor, and, typically, much of the existing equipment can be utilized. The net results of the process are: reduced operational costs associated with sludge generation, improved process control (particularly pH control), reduced gypsum deposition (i.e., less scaling) on system components and reduced sludge generation resulting in less return water for treatment. Despite the relative simplicity of the process, the application of the technology requires careful discrimination, and the "experience factor" for implementation is an important consideration that should not be over looked.

Jan 1, 2000

By C. Demir, M. S. Celik, I. Gülgonul

Na-feldspar (albite) and K-feldspar (microcline or orthoclase) are major feldspar minerals with identical crystal structures and physicochemical properties. Flotation appears to be a unique method of separating these minerals. Fundamental studies on amine/feldspar system in the presence of monovalent salts showed that separation of these feldspar minerals by flotation is possible at certain concentration of monovalent salts in HF medium and natural pH. A comparison between natural pH and HF medium indicates that the latter provides a better selectivity at the expense of higher collector requirement. A general mechanism for both systems involving an ion exchange between the uncommon ions and adsorption of the common ions is proposed to be responsible for creating differences in the charge of albite and microcline unto which amine adsorbs.

Jan 1, 2002

By M. J. Sapko

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations) even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of current and future pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners? Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic, and safe mine sealing technique that can enable mines seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble in combination with a conventional mine seal so that the pressure resulting from a gas explosion is reflected, absorbed, and attenuated, so the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a ?Passive Mine Blast Attenuator? (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals. DISCLAIMER: This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the National Institute for Occupational Safety and Health (NIOSH). It does not represent and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By Michael Gilbert

In the world of tunneling the glamour is in the large diameter, long tunnels, but perhaps the number of projects for small diameter and short length tunnels are greater and generally have higher risk factors. Reasons for these higher risks include both the ?boiler plate? contract provisions used on these types of contracts, the technical specifications related to the tunnel work (versus the pipeline construction), the bid practices including measurement and payment and the construction. This paper reviews and comments on some of the key issues the authors have observed in recent major pipe-line projects that involve a small percentage of tunneling footage of the total contract.

By P. J. Doig

The LCLS project at SLAC will allow new insights into material properties, chemical reactions and biological processes. The project includes half a mile of new underground construction. Excavation in weathered rock is by NATM, using AM 50 roadheaders. Construction began in 2006 and is expected to be completed in 2008. This paper details the construction of the tunnels and cavern on the project.

Jan 1, 2008

By Miles T. Stephens, Felipe Calizaya, Jacob O. Kingston

Currently, the Bear Canyon Mine is facing the challenge of excessively high coal and rock temperatures in one of its headings. In Mine No.3, the air temperature at the 6th Right panel reached 36.4ºC and the coal 83.9 ºC. Due to these severe work conditions, the mining plan has been altered by changing the mine direction to avoid the high temperatures. To investigate the problem, drill holes were developed from the entries and the rock temperatures monitored using K-type thermocouples. The measurements confirmed the existence of localized “hot spots” in the mine. This paper presents a summary of ventilation surveys that were conducted in this mine. It includes the results of coal and rock temperature measurements from drill holes, interpretation of results using a heat flow simulator and the identification of hot spot areas. It also includes a summary of methods that were developed to reduce the hazard and control the problem.

Jan 1, 2005

By Günther M. Volkmann

Continuous developments in tunneling require knowledge transfer between designers and suppliers to optimize the application of support systems. This collaboration allows the designer access to the latest research results, technical innovations, and support specific measurement techniques as well as the supplier?s experiences on recent projects. Project specific requirements determine the information that can be used to increase support system efficiency, advance rate, degree of safety, or decrease costs. This cooperative effort results in not only an unambiguous tender document, but also an optimized design with reduced risk that is coordinated with safe and high performance construction techniques. This paper will address the benefits of an early collaboration to both the design and the specifications in the tender document by using the A3 Hindhead project (UK) as an example.

Jan 1, 2008

Arsenic (As) removal behavior from Changgoon mine tailings was investigated using Acidithiobacillus ferrooxidans (A. ferrooxidans) in well-controlled batch reactors by varying pulp density (0.5?4%, pH=1.8, temp=30oC), reaction initial pH (1.8?2.2, pulp density=0.5%, temp=30oC), and temperature (25?35oC, pulp density=0.5%, pH=1.8). The initial concentration of As in the mine tailings used for bioleaching tests was about 30000 ppm, and the size range of tailings used in this study was 63?74 µm. The reaction speed and initial cell concentration were fixed to 150 rpm and 107 cells/mL, respectively. To complement leaching experiments, pH, oxidation/reduction potential (ORP), and amount of ferrous/ferric ions in leachate were analyzed. Scanning electron microscopy and x-ray diffraction analyses were also conducted for the samples before and after leaching to see if any morphological and compositional changes in tailings took place during leaching process. The As leaching efficiency increased with decreasing pulp density, decreasing pH, and increasing temperature in the presence of A. ferrooxidans. Specifically, no significant change in As removal rate was observed when pulp density d 2% while the removal rate dramatically decreased at pulp density of 4%. Regarding pH effect, As removal rate was much more enhanced at lower pHs (i.e., 1.8 and 2.0) compared to pH 2.2. Increasing temperature was observed to tend to enhance As removal rate, showing about 20% enhanced leaching rate under 35oC compared to 25oC and 30oC at the elapsed time of 5 days. The results for As removal behavior at different conditions (i.e., pH, temperature, pulp density) were consistent with the change in pH, ORP, and ferric ion concentration in leachate, showing greater removal rate at the condition with lower pH, and higher ORP and ferric ion concentration in leachate. Furthermore, decreasing removal efficiency was likely in part due to the extent of the formation of by-product (i.e., jarosite) of ferric ions.

Feb 27, 2013

By B. K. Belle

The use of diesel engine locomotives in South African mines can be traced to Van Dyk Consolidated Mines Ltd on the Witwatersrand gold mines in 1928 as a replacement for battery locomotives. The advantages and disadvantages were recognized in those days, and surprisingly, there are no significant additions to this list, but only refinements. In the absence of any Occupational Exposure Limit (OEL) for Diesel Particulate Matter (DPM) in SA, the Mine Safety and Health Administration (USA) rule is currently being used as a benchmark for the ventilation engineering designs. This paper discusses the ongoing SA journey of measurement and limitations of exposure data for ventilation planning and regulatory purposes. The currently accepted DPM limits are based upon the belief that they are economically and technically feasible for the mines to reach and are not necessarily health based. For SA underground platinum mines, a median TC/EC ratio of 1.8 with a range of 1.2 to 5.8 was observed. For SA coal mines, a median TC/EC ratio of 1.44 with a range of 1.25 to 2.13 was observed. While it is common practice in the USA to use the ratio of TC/EC for metal mines to be 1.3, the ratio found in local platinum mines is 2.2 and for coal mines, the ratio was 1.53 which is lower than Australian studies, i.e., 1.96. It has been shown that a need for critical analysis of TC/EC ratios exists, and possible reasons for variance must be understood before stringent adoption of overseas recommended limits for DPM. It is hoped that the findings from this paper would provide input to scientific approaches in developing appropriate conversion factors, limits for DPM and also in ensuring appropriate error factors (currently 1.14 for TC and 1.2 for EC) for compliance determination.

Jan 1, 2009

There are multiple stages in a mining operation that a mining engineer has to draw polygons to be used as operation guidelines. These polygons are drawn by hand and based on engineer?s experience. However, having automatic procedures for forming the shapes can increase the quality and decrease the efforts required. These shapes need to be homogenous in grades and rock types so that the quality and dilution of material sent to the plant can be estimated with the good approximation. In this paper, a clustering algorithm with shape control is introduced which can provide reasonable guidelines for all the aforementioned shapes by manipulating its parameters. At the end, implementations of the algorithm on a small part of a gold deposit with different mining strategies is presented and evaluated based on homogeneity of grade, rock types and determined destinations as well as the shape.

Feb 27, 2013

By T. Clarkin

This paper presents a hydrologic closure design concept to minimize the risk of water discharges from closed mine tailings facilities. It evaluates the applicability of U.S. Nuclear Regulatory Commission guidelines to develop acceptable designs for the closure of tailings facilities that have a calculated adequate surcharge capacity for environmental protection and an emergency spillway for dam safety. The guidelines provide a basis to estimate an acceptable surcharge capacity of a Probable Maximum Flood series for storage of surface runoff. To be conservative and for redundancy with respect to dam safety, an emergency spillway is provided to pass the Probable Maximum Flood. Depending on the annual water balance, the surcharge capacity may be used by surface runoff and minor amounts of sediment that accumulates in the impoundment from year to year. The emergency spillway crest is then set at this level or above the surcharge capacity, whichever is higher. An example is given of the active Red Dog Mine tailings facility in Alaska where this method was used for the preliminary design of the tailings main dam at its ultimate closure configuration.

Jan 1, 2012

In longwall mining, premining prediction of methane emission rate depends on a number of geological factors, geographical factors, and operational factors. These same factors also can impact the selection of a specific degasification system. This study proposes a principle component analysis (PCA) and artificial neural network (ANN) approach to predict the ventilation methane emission rates of U.S. longwall mines and the optimum combination of degasification boreholes based on the given characteristics of the mine. Artificial neural networks, more than conventional computer models, are adaptable systems that can solve problems such as non-polynomial or very complex relationships that are difficult to describe mathematically. Data on ventilation emissions and degasification system design were obtained from 63 longwall mines in 10 states and were combined with corresponding geological, geographical, and operational parameters for the period 1985-2005. PCA was used to determine the variables that most influence ventilation emissions and degasification system design. Different combinations of variables in the data set and network structures were used for network training, cross-validation, and testing. The resultant ANN models predicted ventilation methane emissions with a 90-95% accuracy and were superior to multi-linear and second order non-linear models. The ANN-based expert classification system was able to classify the design of the degasification system (no degasification, gob vent borehole, horizontal and gob vent borehole, and horizontal, vertical and gob vent borehole) with more than 80% accuracy. The models can be used as prediction and decision tools for the ventilation emissions and degasification system selection for specific site and mine-design conditions.

Jan 1, 2009

Draglines are one of the largest land-based equipment moving across the earth. They typically ranging in size from2.5 to 6.5 kt (2,750 to 7,100 st). Their size, though, makes them difficult to maintain. Recently, G&S Engineering Services used an Enerpac synchronous hydraulic lifting system to lift a 3.2-t(3,500-st) dragline at the Curragh Mine in Queensland, Australia’s Bowen Basin.

Jan 1, 2004

By S. Kittel, P. Galleguillos, H. E. Urtubia

The rougher flotation at Escondida consists of 80 cells of 100 m3 each, with injected air. Escondida has developed a system of automatic control of the rougher flotation using video cameras, which have been operating since 1997 for remote monitoring and manual control. Since 1999, an image processing software and a group of rules have allowed implementation of an expert system. To date, the expert system controls the superficial speed of each cell by adjusting the air flow and the froth depth of the flotation bank. Preliminary tests of the expert control on two of the eight rows gave 1.2% higher rougher recovery at a 92% degree of confidence. The proven benefits are already sufficient to move towards a complete plant implementation.

Jan 1, 2001