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By R. L. Jones, D. D. Runnels, D. P. Dupon, D. J. Cline

To establish meaningful remediation goals and monitoring programs in areas disturbed by mining and associated industries, it is desirable to determine the natural concentrations of metals that existed in these areas prior to being disturbed. In mineralized areas, multiple natural populations of metals and associated components may be present. This paper describes a method for characterizing the natural background chemistry by means of probability distribution dia¬grams. The method can be applied to water, soil and other natural materials. In a study of a complicated hydrogeologic system at the Kennecott Utah Copper North and South Operational Areas near Salt Lake City, UT, probability distribution diagrams were used to differentiate between natural background waters and waters impacted by human activities. The probability distribution diagrams allowed a component-by-¬component interpretation of the chemistry of ground¬water and surface water over a large geographic area. Natural chemical background populations and anthro¬pogenic effects were identified Although the method is illustrated for mining-related sites, the same approach can also be used for other natural and anthropogeni¬cally impacted sites.

Jan 1, 1999

By Donald R. Irving

ALTHOUGH the quantity of material handled at metal and nonmetal mines in the United States in 1962 was 2.7 billion tons, the same as in 1961, a larger proportion was waste. At metal mines, crude ore production declined 1 million tons and waste output rose more than 18 million tons; at nonmetal mines crude ore production declined 6 million tons and waste output rose 36 million tons. Copper and iron ore producers increased their share of crude ore and material handled from about three-fourths to four-fifths of the national metals total, and sand and gravel and stone producers in-creased their share of the nonmetals total, also from three-fourths to four-fifths. Six States-Arizona, California, Florida, Michigan, Minnesota, and Utah-each handled more than 100 million tons of ore and waste, and together they accounted for 43 percent of the U.S. total. When the large-volume construction materials (sand and gravel and stone) were excluded from the totals, four States-Arizona, Florida, Minnesota, and Utah-supplied over half of the material handled.

Jan 1, 1963

By Kenneth L. Rubow, Virgil A. Marple, Bruce K. Cantrell

"In a cooperative study by the University of Minnesota and the U.S. Bureau of Mines, diesel exhaust and mineral dust concentrations have been measured for aerosols generated in the laboratory and in five underground coal mines. Three mines utilized diesel-powered haulage equipment and two used all-electric equipment. Two source apportionment techniques have been applied to differentiate between the mineral dust and diesel exhaust aerosol concentrations measured. The first technique, using a micro-orifice, uniform deposit impactor (MOUDI) for size selective sampling, is based on modeling aerosol size and the premise that the diesel exhaust portion of the aerosol is predominantly submicron and the mineral dust portion is mostly greater that one micrometer in size. The second technique, Chemical Mass Balance (CMB) modeling, was used to referee the analysis of diesel exhaust and mineral dust aerosol concentrations from the size selective sampling results.The MOUDI size distribution data were modeled to obtain parameters describing the fine and course fractions of the sampled aerosol and to estimate the contributions to each mode from both mineral dust and diesel exhaust aerosol sources. The results showed the size distribution of the mixed aerosols exhibited two definite modes with the minimum between the modes occurring at 0.8 µm. Less than 5 pct of the coal mine diesel aerosol was found in the coarse size fraction. CMB analysis confirms the original premise for using aerosol size to separate diesel exhaust and mineral dust aerosol during sampling.Based on the results from the size selective sampling, a personal diesel aerosol sampler has been developed for measuring diesel aerosol mass concentrations. Th.is sampler uses an inertial impactor to size separate the respirable aerosol at 0.8 µm. All material less than 0.8 µm is collected on an after filter for subsequent gravimetric analysis."

Jan 1, 1990

By D. Sancho, M. Weber

"At the start of a new shaft project, a specific number of ground investigations are performed. However, it is not uncommon that the ground conditions during shaft sinking may differ from the designed ones. Therefore, it is extremely important to use tools which minimize discrepancies and to include a monitoring system in the shaft design to collect sufficient data. The paper presents an overview of existing monitoring techniques and discusses future works required to improve, not only the construction during shaft sinking, but also the lining design methodology. INTRODUCTION In most cases, the investigations performed at the start of a new shaft are based on the analysis of rock and soil probes obtained from boreholes. In practice, such analysis performed on a single core often leads to different results when conducted by various experts. The discrepancy in core analysis influences further rock mass assessment and design assumptions. It is not uncommon that the ground conditions during shaft sinking may differ from the designed ones, which affects the estimated stress and strain state of the shaft lining. Therefore, it is extremely important to use tools which minimize such discrepancy and to include into the shaft design a monitoring system to collect sufficient data, which enables control of important phenomena, not only during shaft sinking but also during the life of the shaft. Furthermore, the information collected during shaft sinking, while it is important for proper shaft lining design and updates to the shaft lining due to the local mining and geological conditions, it is also important after shaft sinking. In the whole shaft lifetime, it is not uncommon that the shaft lining is damaged and the liner needs to be renewed (Figure 1) due to various reasons. For this purpose, detailed information collected during construction can be extremely important."

Jan 1, 2019

By Konstantinos Komnitsas, Evangelos Petrakis, Emmanouil Varouchakis

The paper discusses the limitations of population balance modeling (PBM) in predicting particle size distribution in grinding systems. It introduces a nonlinear framework that transforms the batch grinding equation into the Rosin-Rammler distribution, providing more accurate analysis under different operating conditions. The study uses marble as test material and investigates the adaptability of the nonlinear model with different media sizes.

Oct 1, 2023

By Golaleh Riahi

An original method is used to obtain stable nanoparticles of gold-based mono- and bimetallic systems supported on an acidic zeolite. This approach has been applied to PtHY (1wt% Pt) and to bimetallic Pt-AuHY containing 1% of platinum to which is added the amount of gold required to give Au/Pt molar ratios of 20,40,60 and 80%. Metal clusters of Au or Pt-AuHY are formed inside the supercages of the zeolite framework by the thermal reduction of cations by the ligands (en = H2N-CH2-CH2-NH2) under inert gas flow at a temperature depending on the metal. The use of acidic zeolites favours the dispersion of the metal and the thermal stability of the particles. This stability is explained by chemical anchoring of metal clusters by the Brønsted sites of the support. Several techniques have proved that for a molar ratio of 20% metal particles of Pt-AuHY are bimetallic. The segregation of Pt and Au starts for molar ratio =?40%. The catalysts tested on the methylcyclopentane hydroconversion reaction reveal that the addition of gold to platinum leads to an increase in the activity and an improvement in the selectivity for isomerization of the skeleton (cyclohexane and benzene) to the detriment of hydrogenolysis. Similar results were obtained for the dodecane isomerisation to isododecane. These catalysts were also tested in CO, propene and propane oxidation. The activity of fresh catalysts is rather low. It increases after their pretreatment in oxygen or hydrogen atmosphere. In propene oxidation in the reaction mixture O2 ? H2, beside total oxidation of propene to CO2, also propene hydrogenation was observed, particularly at low temperatures. The presence of Au enhances the hydrogenation properties: high selectivities (> 90%) to propane and high propane yields on PtAu HY are observed up to ~150oC, whereas for Pt HY catalyst the selectivity and yield to C3H8 decreases rapidly with the temperature beginning from ~100oC.

Oct 1, 2003

By D. Harrington

"A tabulation is printed below showing the accident record of the thirty-two mines of the Anaconda Copper Mining Co., in Montana, for the years 1915, 1916, 1917, 1918, 1919 and 1920, with summation for the six years. The table gives the number of shifts worked by each mine with the serious plus fatal accident rate for each 10,000 shifts worked.It is seen that in a total of 16,460,767.5 shifts worked by employees of the company's mines during this six-year period, there were only 2,005 serious and fatal accidents and of these, 200 were fatalities, leaving 1,805 serious accidents (a serious accident being one in which 14 or more days' time are lost). This is at a rate of 9,120 shifts per serious accident and at a rate of 82,304 shifts per fatality. Hence, if 300 days be adopted as a year's work, there would be one fatality per 274.3 years of work in these mines and one serious accident for every 30.4 years work.According to Bureau of Mines Technical Paper 286, (Metal-mine accidents in U. S. in 1919, by W. W4 Adams), during the years 1916, 1917, 1918, and 1919, the metal mines of the United States worked a total of 210,548,640 shifts and had 39,705 serious accidents. During the same years, according to the following tabulation, the mines of the above-mentioned company worked 11,958,978 shifts and had a serious accident rate of 0.995 accidents per 10,000 shifts worked. If the metal mines of the United States, working these 210,548,640 shifts, had this company's serious accident rate of 0.995 serious accidents per 10,000 shifts, the total number of serious accidents would have been only 21,000 or the country's metal-mine serious accidents would have been reduced nearly one-half, and there would be 18,705 fewer serious accidents than actually occurred."

Jun 10, 1921

By E. J. Koval

Practical miscible displacement processes will be characterized by lingering of the solvent into the oil. The lingering process is brought on by viscosity differences, and can be accentuated by channeling and longitudinal dispersion. The effects of these factors on the efficiency of unstable completely miscible displacements are combined in what is called the K-factor method. This method, analogous to the Buckley-Leverett method, predicts recovery and solvent cut as a function of pore volumes of solvent injected. Experimental data are included and show excellent agreement with theory for a wide variety of sandstone cores and viscosity ratios. INTRODUCTION Theoretical considerations,1 laboratory experiments,2 and pilot tests3 lead to the conclusion that miscible displacements in the field will be unstable In an unstable miscible displacement, the solvent fingers through the oil. This fingering leads to early breakthrough of the solvent and an extended period during which both oil and solvent are produced. For such a system, there appear to be four principal factors which bring about or accentuate the effects of instability: longitudinal dispersion (including geometrical effects), channeling, viscosity differences and gravity differences. Other factors, such as diffusion and flooding rate, can also influence the effects of instability, but at the flooding rates considered in this report, circa 15 ft/D, they are unimportant. Longitudinal dispersion can be thought of as a spreading of the solvent front caused by the presence of microscopic inhomogeneities. Channeling of the solvent occurs when a porous medium has macroscopic inhomogeneities; i.e., gross permeability variations. Viscosity differences lead to fingering of the less viscous solvent. This difference in viscosity accelerates the growth of fingers along paths previously developed because of permeability variations. Gravity differences lead to overriding by the usually less dense solvent. Al- though gravity effects are generally small at a flooding rate of 15 ft/D, they would, nevertheless, unnecessarily complicate the interpretation of flooding experiments. For this reason, all the experiments reported herein were done with matched density fluids. Fingering and the resultant poor areal sweep were recognized early as the dominant influences on the efficiency and the economics of miscible displacement processes. Much research effort has been spent on ways to minimize fingering and increase areal sweep such as the use of graded viscosity slugs4 or water slugs. Some researchers attempted to work out ways to prevent fingering completely; i.e., to achieve a stable displacement through gravity or latitudinal dispersion stabilization. l Others did not attempt to control fingering but obtained an economic process by merely recycling the solvent and sweeping pattern by pattern.6 During this period, all aspects of fingering came under close scrutiny. Some researchers reported on how fingering looks2 and how it is affected by viscosity ratio,7 geometry,7 and slug size.2,* Peaceman and Rachfordg suggested a mathematical approach to the prediction of unstable miscible displacements in relatively homogeneous sand packs, but their work cannot be extended conveniently to heterogeneous systems. Hence for a heterogeneous system, no method is presently available for predicting solvent cut and recovery as functions of pore volumes of solvent injected. The purpose of this investigation was to attempt to fill in the gap in our knowledge concerning the prediction of performance of unstable miscible dis placements. Necessarily, the system selected for study was a relatively simple one. The restrictions placed on the system were: (1) The system was linear; (2) The solvent was miscible in all proportions with the oil in place; (3) The solvent was continuously injected into the porous medium; (4) Gravitational effects were eliminated by matching densities and (5) All the flood rates were high and constant at 15 ft/D to avoid any small rate effect and to minimize any diffusion effects. To simplify and to indicate that both longitudinal dispersion and channeling arise from permeability variations, the effects which they cause or influence have been termed heterogeneity effects. The use of

By Charles E. Reed

With the increasing importance of clay in drilling operations which demand more precise and exacting control over its behavior, there has come the realization that most of our present methods of control over many of its important properties still represent more of an art than a science. Such a situation with respect to a material of such industrial significance is unfortunate, and naturally many investigations have been conducted to improve our knowledge. In general, these investigations have revealed the complex nature of clay behavior and while sometimes they may not have seemed to contribute directly to a solution of the field operator's problems they have been of inestimable importance in bringing to light the broad fundamental scientific principles upon which must be based any effective working theory correlating the known facts of clay behavior and predicting profitable new lines of attack for its improvement. Major Facts Concerning Behavior of Clays In the study of clays, as in that of most other colloidal materials, it has been impossible to make progress by the study of isolated facts. On the other hand, analysis of large groups of facts, many of which seem at first completely unrelated, can lead to a deeper insight into the structure of clays and the mechanism of their behavior. It will be well to list the major facts on which the analysis here presented is based, starting with those that have emerged repeatedly from past investigations and which thereby constitute an impregnable foundation upon which must rest any comprehensive theory of clay behavior: 1. Clays consist of hydrated aluminosilicates of extremely fine and variable particle size. 2. Suspended in water, clays exhibit variable degrees of swelling, depending upon their origin and upon the chemical and colloidal nature of any other substances present. The magnitude of the swelling is a direct indication of the extent to which the clay has become dispersed.

Jan 1, 1938

By Christopher Mark

Mine planning for a new reserve is based on information obtained from exploratory coreholes. A critical component of an exploration program is the geotechnical evaluation. Poor assumptions about roof conditions greatly add to the risks of mining. Rock mechanics testing is central to a geotechnical exploration program. Typically, 3 to 5 uniaxial compressive strength (UCS) tests are made to characterize a particular roof unit at a given corehole. The average (mean) of these tests is taken as "The UCS" for that location. Isopach contour maps are then used to show spatial trends in roof strength. Two issues are raised by this traditional approach. The first is due to the large variability in UCS values that is typical even within a single unit from a single hole. The average UCS might be higher at Corehole A than it is at Corehole B, but the difference may not be statistically significant. The second issue is whether widely spaced coreholes can identify valid spatial trends in rock strength. The answer depends upon whether rock strength changes over distances that are longer or shorter than the corehole spacing. This is a classical geostatistical problem. While geostatics have been used to investigate many coal quality parameters, they have seldom been used to evaluate rock strength. This paper describes an extensive investigation of these issues conducted by the National Institute for Occupational Safety and Health (NIOSH) in collaboration with Peabody Energy. The study employed the Peabody Rock Mechanics Data Base which contains more than 10,000 individual test results. Data from four important roof units were subjected to statistical analysis: ? Brereton Limestone above the Herrin 6 seam (Illinois) ? Turner Mine Shale above the No. 9 Seam (Kentucky) ? Sandstone above the Eagle Coal (West Virginia) ? Shale above the Eagle Coal (West Virginia) The study did not find significant spatial trends in rock strength in any of the cases. Perhaps there are none, or perhaps the exploration coreholes were just too far apart to see them. These results have valuable implications for the design of geotechnical exploration programs.

Jan 1, 2004

By B. Andreaus

In spite of tremendous efforts in research and development of polymer electrolyte fuel cells (PEFCs), essential properties of the actual catalyst material, supported Pt or Pt-alloy nanoparticles, are not yet well understood. Fundamental understanding of the catalyst structure and the prevailing kinetic mechanisms is, however, of utmost importance for further progress. In the present study, we investigate catalyst activity for CO oxidation from a theoretical point of view. Electrochemical CO oxidation serves as an important test reaction for the study of the fundamental properties of supported Pt nanoparticles. Recent experiments have revealed strong effects of catalyst particle size and supporting material on catalytic activity. It was found, that the activity towards CO oxidation decreases significantly when the particle diameter drops below 2.5 nm. We perform kinetic Monte Carlo simulations of CO oxidation on supported catalyst particles to elucidate this particle-size effect. The simulations are based on the active site concept, highlighting the role of active site formation and finite surface mobility of adsorbed electroactive species for catalyst activity. For comparison with experimental results, potential step experiments were simulated. The Monte Carlo simulations consistently reproduce effects of particle size and electrode potential found experimentally. In comparison with our simulations, analytical mean field models and nucleation and growth models exhibit inferior agreement with experimental data. In summary, our findings support an oxidation mechanism via active site formation. The reason for the slow reaction kinetics on catalyst particles with diameters below 2.5 nm is a rather low CO surface diffusivity. The rates of active site formation, diffusion and CO oxidation via recombination with adsorbed OH can be determined from the simulations.

Jan 1, 2005

By F. J. Schuh

The drilling industry long has been plagued by failures in the bottom few joints of surface and intermediate casing strings. This paper presents an analysis of the various possible causes of failure and concludes that failures are caused by short-lived, high-energy torque impulses delivered from the drill string through the bit while drilling out the cementing plugs, cement and floating equipment. The magnitude of these torque impulses is shown to be a function of the rotational momentum of the drill string, and a method is derived to calculate the magnitude of these impulses. The available methods of strengthening the bottom joints are reviewed. It is concluded that, while present methods are ineffective, a combination of improved procedures for strengthening and minor restrictions on drillout practices will prevent failures. Introduction In most cases, failure in the bottom few joints of casing strings is not discovered until electric logs record that the bottom one, two or three joints have parted from the casing string and slipped down the hole. However, in some cases the parted section of casing uncovers a high-pressure or lost circulation zone, or shifts laterally restricting the passage of drilling equipment. In these instances extensive remedial work is required to realign the parted pieces and seal the exposed formations. Several methods used to strengthen the bottom joints of casing strings include locking set screws in the couplings, putting wedges in special collars, welding straps across the couplings, welding the couplings and, most recently, using epoxy resin-based, thread-locking compounds. Since none of these techniques has eliminated the problem, this study was initiated to find the cause of failures and to evaluate the available methods of prevention. Mechanics of Casing Failures An analysis of the various possible causes of failure indicates that the casing is unscrewed rather than broken and that therefore failure must occur before the shoe is drilled. Since there is no general agreement as to the causes of casing failure, some possible mechanisms were ATLANTIC RICHFIELD CO. DALLAS, TEX. considered in this analysis. Failure of the bottom joints of casing can occur by only one of three types of stress: tension, torsion or bending. The possible mechanisms of failure were evaluated by determining the forces required to cause casing failure by each of the stresses; and, where applicable, the possibility of failure by fatigue was considered. For casing to part under tension requires a downward load of more than the tensile strength of the casing. The lightest API weight H-40 grade casing requires a bit load on the bottom of the casing of 27,000 to 34,000 Ib per inch of bit diameter (Table 1). Since maximum drill collar weights seldom exceed 10,000 Ib per inch of bit diameter, it is apparent that casing strings cannot be parted by the downward load of the drill string. The second mechanism considered was failure by bending. This mechanism requires that the lowermost casing joints be free to be deflected laterally until the bending stress exceeds the strength of the pipe. To fail, the casing (at a height L above the shoe) requires a force and deflection' at the shoe of To deflect the casing shoe with the drill string obviously requires a dog-leg at the casing shoe. This dog-leg must have a rate of change equal to or greater than the change in curvature of the deflected casing, which is given by

Jan 1, 1969

By G. P. Marino

The "conductivity ", Kr, of a spherical void in a linear temperature gradient due to radiation is calculated by integration of the general expression for diffuse radiation between two gray surfaces of arbitrary orientation. The spherical geometry allows an exact evaluation of the phenomenon without resorting to up-proximate expressions for the radiant heat flux. The resulting expression for Kr is three quarters of the approximate value obtained by Loeb. IN the determination of the thermal conductivity of porous materials such as sintered UO2 and ThO2 fuel pellets, the magnitude of the thermal conductivity in the pores due to radiative heat transfer across the pore, Kr, may be important in assessing the total conductivity of the pellets. Loeb' has calculated Kr for various pore geometries by approximating the net flux of heat between two surfaces of temperature difference AT as 4eT~AT and obtained: K,=4yoet3odp [1] where a is the Stefan-Boltzmann constant, E is the emissivity of the radiating surface, To is the average absolute temperature of the region across which radiation occurs, dp is the largest dimension of the gap in the direction of heat flow, and y is a geometric factor. That is: y = 1 for laminar pores and cylindrical pores with axes parallel to the heat flow direction, y = 2/3 for spherical pores, y = /4 for cylindrical pores with axes perpendicular to heat flow direction. It was the purpose of this work to obtain an exact expression for K, in spherical pores by integration of the general expression for the net heat transfer between two incremental areas on the surface of a spherical pore. This procedure yields a value of Kr 3/4 of that obtained by Loeb. I) CALCULATION OF Kr Fig. 1 illustrates the general geometry which defines the problem. The total emissive power for a gray body is given by: E = EoT4 [2] where E is the radiated energy per unit area of the radiation surface per unit time, T is the absolute temperature, o is the Stefan-Boltzmann constant (o = 5.67 X lo- '' watt per sq cm-"K1), and E is the emissivity of the surface. Although Eq. [2] gives the exact expression for the total emissive power of any gray body, all practical problems involve the net exchange of thermal radiation between a body and surrounding bodies. The two major considerations in the solution of such problems are a) shape and relative position of the surfaces and b) the emissivities of the surfaces. In this work it shall be assumed that all incremental areas on a pore have the same emissivity and, further, that little or no reflection occurs (i.e., the radiation hitting a surface is either absorbed or transmitted). Thus, the solution of the stated problem requires only that consideration a be satisfied. Consider two incremental surface areas dA 1 and dA2 of the same material in a general orientation to one another. Let dAl be at temperature TI and dAz be at T2. Fig. 2 illustrates the geometrical parameters involved. That is, 71, is the normal of dA, n2 the normal of dA2, r the line connecting the centers of each area, 81 the angle between nl and r, and Q2 the angle between 7,2 and r. Using Eq. [2] and the Lambert cosine law of diffuse radiation it is easily shown that:293 WdAf- dA, = ecr T*------^fpi------" dAidA2 [ 3a 1 and

Jan 1, 1970

By William R. Adamson, Carlos R. Scherpenisse

The successful development of surface mining operations depends, amongst other factors, on the successful creation of final pit walls which offer long term structural stability. The achievement of such walls will be much more feasible if the mechanisms of rock mass deterioration in the mine are well understood, permitting the control and reduction of this deterioration (or damage). The role of drilling and blasting in causing damage is widely accepted but rarely fully quantified. It is also true that the dependence of rock mass damage on vibration levels is only incompletely understood and little accurate field measurement is routinely conducted in the mining industry.

Jan 1, 1998

By D. Goossens

Quality control is a system which should guarantee that quality is achieved. It is the execution and verification of a project in an organised way, in order to obtain the maximum of certainty that the results meet the requirements. This concerns all stages of the project, from the soil investigation, over the design, to the execution. Quality control can and has been successfully realised for important projects by means of a quality plan. A quality plan is based on a number of general considerations, but should certainly be focussed on the particularities of a specific project. Practical examples of quality plans, which have been realised on sites in Belgium, are developed and the advantage of the system is shown by concrete case studies.

Jan 1, 1996

By S. K. Lahiri, K. C. Ghanta

Design of industrial slurry pipelines is usually performed by applying semi-empirical procedures, requiring a significant experimental study for each project. The mechanisms of suspension flow are not yet completely understood and existing predictive models cover only some aspects of uniform or closely graded particle slurry flows. This paper presents a computational technique for prediction of the velocity and concentration profile in slurry pipelines based on computational fluid dynamics. This model gives numerical solutions for the concentration and velocity distributions in the pipeline cross-section. The model prediction and experimental concentration and velocity profiles were found to be in good agreement. Keywords: pressure drop; concentration profile; particle diffusivity; slurry flow.

Jan 1, 2007

Papers presented at a U.S. Bureau of Mines (USBM) technology transfer seminar describe the causes of violent material failure in U.S. mines, measurement techniques for monitoring events that result in violent failure, and mitigation techniques for controlling failure. Specific factors contributing to violent failure are identified on the basis of geotechnical monitoring in 16 U.S. hard-rock and coal mines and on statistical analyses of 172 coal bump events. New monitoring and analysis techniques developed as tools for assessing violent failure; geotomographic methods that provide new capabilities for the study of material failure and stress changes over large areas; and seismic methods for determining source locations, calculating energy release, and determining source mechanisms are described. Fair correlations have been established among seismic parameters, elastic stresses, face support load, and violent events. USBM studies have identified the advantages using both yielding and stable pillars for coal bump control. A computer program has been developed as an aid for selecting room-and-pillar layouts. The practical aspects of implementing a destressing program is outlined for coal mines, while the importance of mine orientation and timely support installation in controlling buckling-type failure is identified for hard-rock mines.

Jan 1, 1995

By Guangyuan Li

A 3-D block-spring model (BSM) has been developed for simulating the behaviour of jointed rocks. The model uses a discontinuous formulation and an iterative procedure to solve the large displacements in jointed and faulted rock masses. The 3-D BSM has been used to simulate mining excavations in jointed rocks around an open pit and underground settings. The applications have demonstrated that it is a practical tool to solve complicated problems of rock mechanics in civil and mining engineering. This model has recently been modified to incorporate complex geological conditions, such as underground water flow (seepage), unstable blocks and the time-dependent behavior of backfill materials. To demonstrate the capability of the 3-D model this paper presents the fundamentals of the 3- D BSM and its application for open-pit mining. A complete computer package BSM3D has been developed based on the 3-D block-spring model. The package consists of a solving engine for numerical analysis and a Windows based processor for mesh generation and results display. The multi-functioned pre-processor provides tools and menus to help users setting up models easily and conveniently. The fully featured post-processor allows users to view the results in different windows and orientations. The graphical results include contours, vectors, animation of rock movement, and the failure state of the rock structures.

May 1, 2001

By Joo Hyun Park, Kyu Yeol Ko

The viscosity of the CaO-SiO2-xMnO-yCaF2 slags (C/S=1.0; x=10, 40%; y=0 to 15%) was measured to clarify the effect of CaF2 on the viscous flow of molten slags at high temperatures. Furthermore, the Raman spectra of the quenched glass samples were quantitatively analyzed to investigate the structural role of CaF2 in a depolymerization of silicate networks. The critical temperature of the slags abruptly increased at 15%CaF2, which was confirmed to originate from a crystallization of cuspidine using XRD analysis. The viscosity of the slags continuously decreased by CaF2 addition in the 10%MnO system, whereas the viscosity of the 40%MnO system was not significantly affected by CaF2 addition. The effect of CaF2 on the viscosity of the slags was quantitatively analyzed using micro-Raman spectra of quenched glass samples accompanying with a concept of silicate polymerization index, Q3/Q2 ratio. A polymerization index continuously decreased with increasing content of CaF2 in the 10%MnO system, whereas it was not affected by CaF2 in the 40%MnO system. Consequently, the bulk thermophysical property of the CaO-SiO2-MnO-CaF2 slags was quantitatively correlated to the structural information.

Jan 1, 2014

By Laurentiu Nastac

"This paper describes the development and validation of a comprehensive multiscale modeling approach capable of predicting at the mesoscopic scale level the ingot solidification structure and solidification-related defects commonly occurring during the vacuum arc remelting (VAR) process. The approach consists of a coupling between a fully transient macroscopic code and a mesoscopic solidification structure code. The predictions from the multiscale model, including grain morphology and size, primary and secondary dendrite arm spacings, Laves and NbC phases, tendency for freckling and columnar-to-equiaxed transition, were validated against experimental measurements for a 20-inch diameter VAR alloy 718 ingots. The validated model was then used to investigate the effects of melting rate and ingot diameter on the solidification structure of VAR processed 718 ingots.IntroductionThe objective of this work was to develop a fully transient multiscale modeling approach to get an insight into the effect of processing parameters on the cast micro- and macro-structure during VAR processing. The developed model assists in achieving better control of the ingot solidification structure and to determine trends in the macrosegregation in these ingots. Another objective of this work was to analyze the transient effects of production rate and ingot size on the resultant ingot microstructures. This objective was met by first understanding the effects of the full range of processing parameters typically used in the VAR process. Processing parameters such as power input and heat extraction rate significantly influence the ingot liquid pool size and shape as well as the ingot structure, which in turn will greatly impacts the final ingot quality."

Jan 1, 2012