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By J. A. Marts, R. C. Gilmore, S. Saki, J. F. Brune

Computational fluid dynamics (CFD) modeling involves the creation of a computation domain called a mesh or grid to solve the equations defining the physics of fluid flow. This process often comprises the majority of time spent in modeling efforts. In a project sponsored by the U.S. National Institute for Occupational Safety and Health (NIOSH), researchers at the Colorado School of Mines used an innovative meshing approach, allowing easy adaptation of the CFD model to adjust to a variety of longwall bleeder-ventilated and progressively sealed (often referred to as bleederless in the United States) mining geometries, with gob porosity and permeability scalable over a wide range. This paper presents the methodology of the meshing and scaling approach along with recommendations for using CFD modeling in longwall gob ventilation applications. The new meshing technique was utilized to evaluate the function of a back return in a progressively sealed gob and a bleeder-ventilated gob.

Jan 1, 2014

By G. A. Doyle

The quality of water in mine pit lakes depends in part on the physical limnology (Le. stratification, turnover, and development of anoxic conditions with depth) of the lake. Limnologic data collected from four existing pit lakes indicate that pit lakes develop a thermocline, or temperature stratification, in the upper 10m to 30 m of the water column. Two of the pit lakes (26 m and 55 m deep) undergo seasonal turnover of the entire water column, whereas two deeper pit lakes (110 m and 240 m) undergo seasonal turnover of only the upper portion of the water column. In the deeper lakes, seasonal mixing does not extend through the entire water column and a distinct chemocline develops with depth.

Jan 1, 1996

By T. F. Tomb

Although the number of operating longwalls (approximately 100) has remained relatively constant over the last five years, longwall production levels have significantly increased and have in some cases more than doubled. As a result of the increase in production, control of respirable dust continues to be a problem. Therefore, the Mine Safety and Health Administration (MSHA), Pittsburgh Health Technology Center, Dust Division, initiated a study to investigate the availability and adequacy of technology for controlling dust on longwall mining operations. The study involved 23 longwall mining operations in three different Coal Mine Safety and Health Districts. Each operation was visited for a full shift. Respirable dust samples were collected on face personnel and at fixed locations along the face. Parameters in place to control dust were noted with special emphasis being placed on obtaining quantitative data relative to ventilation, headgate dust controls, cutting drum sprays, external machine sprays and cutting sequence. Attempts were made to correlate dust control parameters in place at the time of the visit to dust concentrations measured at the tail, on the tail shearer operator and to the average concentration of dust determined from averaging all the measurements from the occupations sampled. The parameters in place to control dust were also compared to the gamut of technology known to be available to control dust. This paper presents a discussion on the effectiveness of the parameters in place to control dust and on the availability of technology for the control of dust on longwall mining operations.

Jan 1, 1990

By Gunnar Thaning

The iron ores mined by LKAB in the north of Sweden have excellent beneficiation properties. This gives LKAB a favourable position as regards the production of low silica pellets for direct reduction. LKAB have concentrated on developing and marketing grades of pellets for the Midrex-Purofer-HyL process group, i.e. such D.R. processes which are carried out in a shaft furnace or a static bed using reformed natural gas as a reducing agent. The paper deals with properties and quality demands of iron ore pellets for such processes. Matters such as the effect of the residual magnetite in the fired pellets on the degree of metallization, the amount and composition of the slag phase in the pellets, the mechanism of the disintegration during reduction, the state of swelling of the pellets during the conditions prevailing in these processes, the importance of the porosity, the improvement of the reducibility and lowering of the sticking tendency of the pellets by small additions of suitable additives and the influence of the pellet size are discussed. A special test procedure for D.R. pellets has been elaborated by LKAB. Thus, three metallurgical properties are routinely determined separately, namely reducibility, reduction strength and sticking. The test methods are described. Finally the present and future LKAB pellets for direct reduction are presented with respect to chemical analyses and metallurgical properties.

Jan 1, 1978

By E. A. Rychkun

Introduction Minicomputers have been gaining acceptance in mining. Low cost interactive processing and plotting can now be controlled by geologists or engineers needing rapid solutions and specialized mining software in formats that allow noncomputer personnel to readily interact with computer processes. User-oriented programs maximize the use of interactive display features and graphics, as shown by the HP9845 minicomputer, a unit with portability, processing power, graphics capabilities, capacity, and peripherals such as plotters, digitizers, disk drives, and printers. Application Coal exploration projects require that much effort be spent determining coal volumes within trial pit limits. This determines a prospect's viability and potential. Adapting volume calculations to a computer has been limited, since it was difficult to create reasonable representations of complex coal seam geometry with a digital process. So many of the simple mechanical procedures needed to produce pit reserves are still performed manually by geologists and engineers. But with new minicomputers and their interactive graphics, it is now practical to accurately model complex structures without tedious calculations. GEOSEM (Geomin Seam Oriented Exploration System) is a computer system designed to analyze coal prospects. The system shows how a coal prospect, with complex geology, can be quickly analyzed, modeled, displayed, and evaluated for mineable reserves. Its interactive graphics allow rapid visual presentation of data, high-speed tabular reports, and precision plotting. The system is most effective when used by a geologist or engineer who selects the required operations and specifies relevant parameters via screen and keyboard interaction. Rolling Hills The Rolling Hills prospect represents a typical Rocky Mountain coal deposit. Enough geological interpretation has been done to show a complex system of block faulting with coal seams following synclines of stratified lithologies. With the completion of initial drill hole exploration, questions arose concerning coal volumes and strip ratios involved with various pit limits. Quality information had been gathered on the coal intercepts. It was decided that coal vol¬umes and pit designs were of prime importance. The objective was to enter and display data, create a computer model based on interpretation, develop pit designs, compute seam/ waste volumes, and report various contents. The project, begun by entering data in the GEOSEM system, was completed in several days. Data Entry For modeling, the prime information was seam identity and drill hole intercept. Other information-rock type, Btu rating, and percent of ash, sulfur, and moisture-was also available. It, too, was entered into the data base through the computer keyboard and then reported, verified, and corrected. Various reports can be produced, according to user specified sort parameters. For example, from an analysis of available data, only 14 intercepts could be found with Btu value greater than 8000 and sulfur content less than 0.4%. The sort option can also be used prior to entry into the analysis routines. Data Analysis Though the objective was to create a seam model and compute reserves, it became necessary to project quality information into unsampled areas. Statistical analysis was then war-ranted. A typical analysis correlated the lack of relationship between percentage of ash and Btu. Although histograms were also produced, these typified a lack of samples and "ragged" distributions. A geostatistical analysis was also applied, showing the results of computing a 2-D variogram on the largest coal seam. Results showed an average range of 18 m, with a poorly defined variogram. Data Display and Drafting Scaled plans and sections were required so seam locations could be compared to hand drawn interpretations and drill coordinates verified. At the same time, topography could be interpolated from collar elevations to determine whether surface control points were needed for better definition. In addition, a new set of 50 final-scale drawings were required, showing new drilling information. By using the computer screen as a "scratch pad" device, various sections were displayed and then plotted on a drum plotter at the desired scale for overlay on original sections. Both lithology and seam name were plotted for the five main sections. Since the coal seams were striking north-south, sec-

Jan 11, 1981

By C. Hanson

Two modes of potential loss of oxime extractants in liquid extraction processes for the extraction of copper have been studied. In loss "by chemical degradation, two mechanisms of acid hydrolysis are possible, some reagents degrade primarily in the organic bulk phase, Others at the interface between the organic phase-- phase protects the oxime but salts added to the aqueous acid phase can promote the rate of degradation. The reagents reported on are the LIX series (Henkel Cpn), SME529 (Shell Chem.Co.) and P5100 (Acorga) Loss by organic entrainment in the aqueous phase leaving mixer-settlers has also been studied, parameters investigated including impeller/tank geometry and the phase inlet arrangements. The consequences of extractant loss by the above mechanisms...are commented upon. They include the direct economic cost, the possible environmental problems and the implications for downstream operations such, as electrowinning.

Jan 1, 1980

By C. Douglas Lee

This case study describes the work done at the University of Arizona on the development of a computer mine model for an irregularly shaped and spotty ore deposit. The purpose of the work was to develop techniques for modeling any highly irregular deposit, for which the regular 3D fixed block model is not well suited. The deposit contained complex geology consisting of sedimentary beds that had been faulted, thrusted, and intruded by igneous rocks (see Fig. 1). The physical dimensions of the modeled ore body were 1067 m (3500 ft) along the N-S direction and 914 m (3000 ft) along the E-W direction. Topographic relief in the modeled area was approximately 274 m (900 ft). The highest grade of ore was found near the surface with mineralization extending down to approximately 152 m (500 ft) below. Using a fixed bench height of 12 m (40 ft), the model required 25 levels with the highest elevation being at 1286 m (4220 ft). Fig. 2 shows a cross section of the developed computer model of the ore deposit. The particular modeling approach selected for this deposit was the 3D irregular block model.* This meant that only the dimension of bench height was fixed at 12 m (40 ft). Irregular size blocks in the form of polygons were adopted in the model to describe the ore zones and geologic contacts. The following sections of this chapter describe some of the techniques used in modeling.

Jan 1, 1979

By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By P. T. Bissert, T. J. Lutz, J. A. Yonkey, G. T. Homce

"The National Institute for Occupational Safety and Health (NIOSH) has been researching refuge alternatives (RAs) since 2007. Refuge alternatives typically have built-in pressure relief valves (PRVs) to prevent the unit from reaching unsafe pressures. The Mine Safety and Health Administration (MSHA) requires that the PRVs vent the chamber at a maximum pressure of 1.25 kPa (0.18 psi, 5.0 in. H2O), or as specified by the manufacturer. To facilitate PRV testing, an instrumented benchtop test fixture was developed using an off-the-shelf centrifugal blower and ductwork. Relief pressures and flow characteristics were measured for three units: a modified PVC check valve, an off-the-shelf brass/cast iron butterfly check valve, and a commercially available valve that was designed specifically for one manufacturer’s steel pre-fabricated RA and has been adapted for use in built-in-place (BIP) RAs located at one mine. PRVs used in tent style RAs were not investigated. The units were tested with different modifications and configurations in order to check compliance with 30 CFR regulations. BACKGROUND The Mine Improvement and New Emergency Response Act of 2006 (Miner Act) (1) was enacted in the wake of three mine explosions/fires that claimed 19 lives that year. Intended to help improve underground coal mine accident preparedness, the MINER Act includes provisions that target mine safety issues in areas such as emergency response planning, adoption of new technology, training and education, and mine safety standards enforcement. Section 13 of the MINER Act specifically directed the National Institute for Occupational Safety and Health (NIOSH) to provide for research into the effectiveness and viability of refuge alternatives (RAs) for underground coal mines, and the Department of Labor to act on the results of such research as appropriate. These mandates culminated in the 2009 adoption of changes to 30 CFR mining health and safety regulations, requiring underground coal mines to provide mine emergency RAs and associated components, to provide a life-sustaining environment for persons trapped underground. Such RAs can be either self-contained mobile units or built-in-place (BIP) facilities. The regulatory changes also include provisions establishing requirements for the Mine Safety and Health Administration (MSHA) approval of RAs and their components, and among these provisions are numerous criteria for providing a safe breathable atmosphere under positive pressure within the RAs. One specific criterion for maintaining a safe RA atmosphere requires the inclusion of an air pressure relief valve that will activate at a maximum of 1.25 kPa (specified as 0.18 psi, or approximately 5.0 in H2O), or at a pressure as specified by the RA manufacturer, above mine atmospheric pressure in the RA (2)."

Jan 1, 2016

By A. K. Sinha

Despite the tremendous efforts and costs incurred by the industry and regulatory agencies to prevent premature roof failures in underground mines, roof falls continue to occur frequently due to the very unpredictable geological conditions and dynamic nature of mining operations. In fact, roof falls continue to be the largest contributor to coal mine fatalities. The failure of a mine roof generally occurs following a prolonged, gradual degradation in its physical conditions. An electronic mine roof monitoring system has been developed and tested in operating mining sections. It monitors mine roof degradation on a continuous basis. The field test results are presented and discussed.

Jan 1, 1987

By Cory Bolen, Nadav Bar-Yaakov, Eric Zimmerman, Gregory Raines

The Chimney Hollow Reservoir Project broke ground in August 2021, constructing the tallest Asphalt Core Dam in North America, intending to improve reliability of drinking water supply to Northern Colorado communities. Aiming to expedite and streamline the geological mapping process in the tunnel, Stantec’s teams have developed a mobile and web-based GIS application for digital mapping input and rock mass evaluation, allowing real time decision making for assigning tunnel support class and resulting in a faster more efficient process. The following article presents and demonstrates the GIS mobile and web application-based process, the mapping results and review additional uses of the database created.

Jun 13, 2023

By Seokwon Jeon, Ho-Young Jeong

"Various numerical methods have been tried to estimate the cutting forces of a TBM disc cutter. In this study, SPH/FEM coupled method was newly employed to improve the traditional FEM analysis. The disc cutter and rock were modeled by Lagrange and SPH codes, respectively. The numerical cutting test was carried out for representative Korean rocks with different cutting conditions. The results show that the cutting forces obtained from numerical simulation had a good agreement with those from LCM tests, and that applying SPH method to rock cutting model has advantages and improvement compared to traditional FEM method. Erosion criterion and erosion limit were not required to simulate the rock fragmentation process, and the cutting forces from the numerical simulation was more stable and accurate. The results indicate that the numerical simulation can be successfully used to estimate cutting performance of a TBM. 1. INTRODUCTION Various numerical studies have been carried out to accurately simulate the limitations of linear cutting machine (LCM) tests. Numerical modelling methods have advantages comparing with full scale tests in terms of cost and time involved. Many numerical methods have been used to simulate rock cutting process by different cutting tools and the studies are summarized in Table 1.In 2D simulations listed in Table 1, because they do not take account of rolling force and horizontal rolling mechanism of a disc cutter, indenter was selected as cutting tool in their modelling. For these reason, 2D modelling is not suitable for rock cutting modelling using a disc cutter. In contrast, 3D numerical models can take account of the indentation process by thrust force and penetration processes controlled by rolling force."

Jan 1, 2016

By J. Richard Kyle

The Pb-Zn ore bodies in the Pine Point district are localized in paleo-solution structures that developed as the result of post-middle Givetian subaerial exposure of the carbonate barrier complex. Sulfides are concentrated in transgressive pale-solution structures that acted as natural bypasses between aquifers and loci for mixing of fluids of different character, one of which contained metals and the other reduced sulfur. Complex ore textures indicate rapid early sulfide precipitation followed by slower sulfide growth. Evidence for both sulfide-carbonate equilibrium and disequilibrium conditions suggest fluctuations in ore fluid composition. District and ore body metal distribution patterns may reflect the nature and movement of mineralizing fluids.

Jan 1, 1979

By Morris Loshinsky, George Ziegler

NEW ROUTES - 63rd STREET CROSSTOWN The New Route construction along East 63rd Street in Manhattan began in 1969 with the East River tunnel connecting Manhattan and Queens. The 63rd Street Line, once in Queens, is planned to connect to another new route called the Queens By Pass or Super Express (See Exhibit 1) which would connect to the Queens Boulevard Line at Forest Hills. The purpose of the Queens By Pass was to alleviate subway congestion to and from the Borough of Queens, whose population had rapidly expanded during and after World War II. The existing Queens Boulevard subway lines (the "E" and the "F" trains) are almost filled to capacity at their terminal stations with passengers from Long Island. Passengers boarding trains enroute from the local Queens stations have difficulty boarding crowded trains, and, at times, cannot board the trains. The New Routes, thus, were to give additional train capacity into Manhattan and thereby relieve the crowded conditions along the Queens Boulevard corridor. PROFILE - METHOD OF CONSTRUCTION The portion of the New Route passing east-west under East 63rd Street on Manhattan (See Exhibit 2) had to snake beneath intersecting structures running north and south, such as the Con Rail tracks below Park Avenue and the 80 ft deep Lexington Avenue Express track structure along Lexington Avenue. Further, the Lexington Avenue Local tracks are in a separate structure which has a high profile close to the street surface. Therefore the 63rd

Jan 1, 1981

By W. C. Shanks

Metalliferous sediments and/or saline brines have now been discovered in numerous sea floor deeps along 900 km of the axial rift zone of the Red Sea (Fig. 1). The Atlantis II Deep remains the most interesting of the the brine deeps both in terms of intensity of submarine hydrothermal processes and in terms of potential economic importance. In fact, successful completion of a pre-pilot mining test in 1979 indicates that the Atlantis II Deep may become the first deep sea base metal sulfide mine (Mustafa and Amann, 1980). Under the most optimistic scenario, the Atlantis II Mine might be established 4-6 years after completion of a year long pilot mining test in 1983-84. If established, mining would produce about 100,000 tons per day of wet mud with about 200 tons per day contained zinc, and proportional amounts of Cu and Ag. Expected mine life would be about 15-20 years (Anon., 1981). In addition to direct economic importance, the Red Sea brines and metalliferous deposits provide significant insight into exploration for sea floor brine-related ore deposits and for analogous ancient deposits. In this paper I will concentrate on the economic potential of Red Sea deposits and sea floor exploration for brine related deposits, but some ramifications of relevance to ancient deposits are extant.

Jan 1, 1982

Underground instrumentation and observations at longwall panels have demonstrated that the growth of main roof causes an extremely high roof weighting on the shields. It can sometimes result in catastrophic effects on the support when the roof weighting intensity far exceeds the support capacity. In this paper, a comprehensive study was conducted on characteristics of main roof breakage and its effects on shields at different locations, based on the monitored shield data, theoretical analysis, and finite element analysis. With the help of theoretical analysis and numerical modeling, stress distribution and redistribution in the main roof were analyzed in detail to define main roof failure modes and understand the maximum roof weighting intensity imposed on the shields. From this study, it was found that the effects of main roof breakage on shields are chiefly related to the shield initial setting condition and the final failure mode of the main roof.

Jan 1, 1994

Iron removal using biologically produced organic acids was investigated as a treatment option for the production of refractory grade bauxite. A leaching solution containing 98mM oxalic and 67mM citric acid was prepared from a sucrose medium using for fermentation the fungus Aspergillus niger. The leaching capacity of the metabolic product was tested on a bauxite sample containing 16-19% iron (as Fe2O3). Aerobic and anaerobic leaching tests were carried out at pH 3, 50°C and in the absence of light. Results indicated that more than 80% of total Fe can be removed from the ore, when the sample is finely ground and applying a two stage treatment. The presence of oxygen was seen to affect adversely the kinetics of the process, suggesting that leaching follows a reductive mechanism. Experiments that were carried out with different particle size fractions indicated that for obtaining efficient removal of iron particles should be finer than 0.63mm. Reduction of the operating temperature from 50 to 30°C caused a decrease in the rate of iron removal by more than 10 times.

Jan 1, 2006

By S. K. Mishra, S. B. Kanungo

Because conventional (physical) methods of ore dressing are not suitable for reducing the phosphorus contents of high-phosphorous manganese ores from Andhra Pradesh (AP) and the adjoining area in southern Orissa, India, the adoption of chemical methods becomes imperative. An attempt was therefore made to reduce the phosphorus content of partially beneficiated manganese ores from AP by roasting with sodium carbonate and then leaching with hot water. However, due to the higher phosphorus contents of the manganese ores from Nishikhal mines in southern Orissa, and because of their apparent resistance to dephosphorization by roasting with Na2CO3 alone, a mixture of Na2CO3 and NaCl was found to be necessary to reduce the phosphorus content to below 0.15%. Free-energy calculations at 700°C and above indicated that Na2CO3 (or Na2O as the active component) is a more active reagent than NaCl. Various process parameters, such as the temperature and time of roasting, the amount of sodium carbonate and the temperature and time of leaching, were studied to arrive at the optimum conditions for dephosphorization.

Jan 1, 2000

By Ugo Preti, Gianfranco Ferrara, Mark C. Williams, Thomas P. Meloy

Theoretical and experimental lockedness profile curves are the same when the model assumptions are met. They appear different because of the way the data is presented. Continuous theoretical lockedness profile curves present all the data, including the wings of the curves giving them the deep U-shaped configuration. Experimental lockedness profile curves, because of the measurement methods, are discretized, obscuring the wings. If the continuous theoretical curves are discretized, they are similar to the experimental curves. When a float sink test is used to measure an interval of locked particles, the integrated averaging of the separation process obscures the wings of the continuous theoretical curve. To disclose the wings with experimental data, narrow density or measurement intervals must be used.

Jan 1, 1992

By WILLIAM M. CROSS, ALBERT ROMKES, BERNARDO MORENO BAQUEIRO SANSAO, Jon J. Kellar

In this research study, the interaction of particles with substrates of different roughness magnitude was investigated. Particle surface treatment, relative humidity (RH), and surface roughness levels were controlled in order to achieve separation of different particles by applying removal forces. Three different approaches to reproducibly roughen surfaces were used. Initially, glass disks were laser engraved to create a reproducible, controlled roughness substrate. However, the laser engraving method produced surface features that were much greater in scale than the particles. These scale differences were such that the substrates produced were not of value to this research. The second option investigated to induce reproducible substrate roughness was to scratch the glass disk using sandpapers of known grain size. A third approach to establish reproducible roughness was to use fine stainless-steel wire mesh substrates. In tests with sanded glass disks, the interfacial energy of plasma-cleaned (hydrophilic) glass beads had a high variation at 40% RH, showing non-uniformity of area of contact between particles and substrates. As the RH increased, it was expected that the interfacial energy of hydrophilic particles would increase, but this behavior was not observed. In addition, comparing the interfacial energy results of hydrophilic particles with hydrophobic particles, a region with significant interfacial energy difference was not identified. In the case of the stainless-steel mesh substrate, the mesh asperities and particle dimensions were comparable. Thus, the smaller particles had more area of contact with the substrate than the larger particles. For the plasma-cleaned (hydrophilic) beads, the recovery values had an average of 92.5% recovery when the RH was between 46 and 85%. For the hydrophobic beads, the average recovery was 19.0% when the RH was between 46 and 75%. Thus, the hydrophobic characteristic of the particle influenced its lower interaction with the mesh substrate. The difference in recovery can be exploited to achieve separation of particles based upon adhesive forces.

Nov 30, 2021