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By Fabiano A. C. M. Passos, Vanessa P. R. Silva, Lillian M. B. Domingos, Fernanda A. N. G. Silva, Zuleica C. Castilhos, Roberto B. Faria

Wastes from gold mining need to be monitored from the beginning of mining activities until to the mine closure. Wastes from tailings dam were characterized by XRD, XRF, elemental analysis of carbon and sulfur and ICP-OES. In flotation waste (FW) were observed quartz, dolomite, pyrite, muscovite and chamosite were observed. Meanwhile, in cyanidation waste (CW), besides those described in FW, minerals such as sphalerite, galena, pyrrhotite, microcline and albite were detected, indicating a higher concentration of sulfide minerals in the cyanidation waste. In relation to C and S content, to FW and CW, they were 2.5 and 0.0% and 0.64 and 15.4%, respectively, confirming the majority of sulfides at CW sample and indicating the absence of the flotation organic reagents at the cyanidation waste. The analysis by ICP-OES indicated As, Zn, Pb, Cr and Cd content for FW and CW: 13.30 and 343 mg/kg; 399 and 7,900 mg/kg; 136 and 13,000 mg/kg; 130 and 260 mg/kg; 3.60 and 84.60 mg/kg, respectively. It was also verified significant levels of heavy metals, which indicates the necessity of performing wastes toxicity tests.

Mar 1, 2017

By Steve Klein

Weak rock is an important consideration in tunnel design and construction due to the difficult ground conditions that are often encountered. Nevertheless, when conditions are favorable high advance rates can be achieved leading to economical tunnel construction. Successful construction of a tunnel in weak rocks depends on correctly anticipating the behavior of these unique materials. The objective of this paper is to provide guidelines that can be used to accurately classify the performance of weak rock in tunnels.

Jan 1, 2001

The widely accepted kinetic model for the gaseous reduction of hematite is critically examined. The formation of the wustite layer during internal reduction cannot be explained in terms of solid-state diffusion. Present evidence indicates the existence of a micropore system in the wustite adjacent to the magnetite with the gas/solid type of reaction occurring not only at the iron/wustite interface but also at the wustite/magnetite interface. During the partial reduction of dense hematite pellets, in a controlled atmosphere, porous magnetite and wustite are formed as products. The mean pore size, as measured by mercury injection, increases with time at constant temperature and with temperature increase over the range 6500C to 950°C. The sizes of the pores indicate that Knudsen diffusion is the principal gaseous transport mechanism across thick layers of magnetite or wustite.The kinetics of the gaseous reduction to iron are consistent with a mixed control mechanism involving the interaction of gaseous diffusion effects with a first order reversible chemical reaction at the iron/wustite interface. Because of the larger pore sizes in the iron layers, ordinary molecular gaseous diffusion must be the principal transport mechanism. The usual experimental methods used for establishing the validity of chemical rate ~ontrol are incapable of differentiating between the mixed control- mechanism and exclusive chemical control.Some implications of mixed control kinetics are developed, including a predicted independence of rate on reducing gas pressure at higher pressures.INTRODUCTIONAn extensive literature review of the reduction of iron oxides has been compiled recently by Themelis and Gauvin (1962). From the large number of papers published and the widely divergent opinions of workers in this field, it appears that a simple unified quantitative analysis of reduction kinetics is not possible. The aim of the present paper is to show that a major cause of confusion is due to the attempts of many workers to interpret experimentally observed reaction rates in terms of a single rate controlling mechanism without due regard to other rate processes which must occur simultaneously.Some of the differences in behaviour reported for particles...

Jan 1, 1964

By W. P. Yant

The hazard to health from contamination of air by a noxious gas depends not only on the potential harmful response attending exposure, but also on the warning properties, which in effect may be termed the "accompanying warning response," This warning may be manifested as an odor, taste, irritation of the eyes, nose, or throat, or perhaps headache, vertigo, or nausea. These manifestations may be painful and even slightly harmful, but to a much lesser degree than the primary injury of exposure. The warning response mitigates hazards directly in proportion to the degree of Intolerability which accompanies injurious exposure, and accordingly its absence augments hazards. This accounts for the fact that the actual health hazards from a non-odorous or non-irritating gas or vapor of comparatively low toxicity sometimes equal or exceed the hazard from a considerably more toxic substance, but one which possesses a marked odor or produces eye, nose, or throat irritation in advance of harmful exposure. When a substance lacks the properties for giving warning, it is often possible to impart them by the addition of a small amount of another substance which has an exceedingly high warning intensity. The vapors of this substance, commonly termed a "warning agent" or "tracer gas," escape and mingle with the gas or vapor which lacks warning properties and thereby apprises persons of the latter's presence. The amount of the warning agent added is that which will give adequate warning in advance of serious physiological harm from the dangerous gas or vapor.

Jan 1, 1930

By Maíra de Paula Pereira de Lucena

Revestimentos de conversão nanocerâmicos são obtidos pela imersão de peças metálicas em soluções contendo íons de titânio, zircônio, cério entre outros. Esses revestimentos vêm sendo estudados como uma alternativa a outros processos de conversão que possuem inconvenientes ambientais, como a cromatização e a fosfatização. No presente trabalho foram formuladas diferentes soluções a base dos ácidos hexafluorozircônio e hexafluortitânio para a deposição de revestimentos nanocerâmicos sobre substratos de aço galvanizado. O objetivo é mapear os efeitos dos parâmetros de processo de obtenção do revestimento quanto ao desempenho contra corrosão. Os parâmetros estudados foram a concentração, o pH e o tempo de imersão nas soluções formuladas. Para avaliar os revestimentos obtidos foram realizados ensaios eletroquímicos de espectroscopia de impedância complexa. Os resultados indicam uma forte interação entre o pH e a concentração dos ácidos em solução e que concentrações mais baixas geram uma proteção mais eficaz O melhor conjunto de parâmetros foi para menor pH, concentração e tempo de imersão.

Aug 7, 2018

By C Rizos, A Ng

Land surface deformation can be caused by underground mining activities. The maximum subsidence normally occurs directly above the location of the excavation of the coal seam. In the case where the longwall mining technique is applied, the magnitude and shape of the subsidence bowl are constrained by the longwall structure (pillar). This paper describes the use of satellite radar interferometry for monitoring surface subsidence due to underground mining, as a cost-effective geodetic technique and complementary to conventional ground surveying techniques. This paper uses data acquired by the current generation of SAR satellites û the European ENVISAT and the Japanese ALOS û to monitor ground subsidence in the southern highland coalfield in New South Wales, Australia. An accumulated DInSAR subsidence mine map is produced using six successive ALOS acquisitions. The results are post-analysed with the aid of geographic information systems (GIS) and validated using ground survey data.

Jan 1, 2008

By Xiang-dong XING, Zhen-yang wang, Xing-le LIU, Jian-Liang Zhang

Experiments were carried out by adding CaF2 as catalyst in a Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from1473 to 1673K. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39kJ•mol-1 without adding any catalysts. Adding CaF2 of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95kJ•mol-1. In addition, temperature is an important factor influencing on reaction rate.

Jan 1, 2015

By Greg Shapiro, Paul Dr. Worsey

Mining, quarry, and construction blasts are becoming more and more dependent on bench profiling. The use of accurate profiling gives the blaster better data for the most efficient blast results. So, we ask the question: What is the best method for measuring and analyzing burden?

Jan 1, 2019

By D. E. Traut

A fluidized, countercurrent ion-exchange system was developed, operated, and evaluated by the Bureau of Mines in support of its objective to help assure an adequate uranium supply for future national needs. The system consisted of integrated multiple-compartment absorption and elution columns in which the solution flows are continuous, except for short periods when resin increments are withdrawn. The exchange of uranyl sulfate between a simulated acid-leach-uranium solution and a strong-base, ion-exchange resin was studied, together with subsequent elution using an acidified sodium chloride solution. The effects of the number of compartments, compartment height, amount of resin withdrawal, solution flow rate, and column diameter were investigated. Also examined were the kinetic and equilibrium relationships for the absorption and elution steps. The experimental data indicate a strong interdependence between variables. Solution retention time appears to be a major limiting variable in the absorption process, while resin residence time is the determining factor in the elution process. The columns system was efficient over a range of conditions, but close control was needed for optimum operation.

Jan 1, 1978

By J. P. Josien, Didier C.

ABSTRACT: France now faces the closure of most of its mining sites. Surface instability risk may sometimes remain, especially where large underground voids exist. This paper illustrates the importance of failure mechanisms identification in order to define properly how to manage the residual risk. RESUME: La France fait aujourd’hui face à la fermeture de ses exploitations minières. Des risques d’instabilités de surface peuvent persister, notamment lorsque des vides résiduels existent au sein des travaux souterrains. L’article illustre l’importance que présente la nature des mécanismes de rupture potentiels dans le choix des mesures compensatoires à adopter pour gérer le risque résiduel à long terme. ZUSAMMENFASSUNG: In Frankreich stellt sich derzeit das Problem der definitiven Schliessung des meisten Bergwerke. In manchen fällen ist die Stabilität der Oberfläche nicht garantiert, speziell wenn unter Tage nicht verfüllte Hohlräume verblieben sind. Dieser Bericht zeigt die Wichtigkeit, bei der Auswahl geeigneter Langzeit-Risikomanagementmethoden, der verschiedenen Mechanismen mit denen ein eventueller Bruch an die Tagesoberfläche geraten kann.

Jan 1, 2003

By M Norbert, P Mok

The mainline running tunnels for Legacy Way comprise of two-lane tunnel boring machines (TBM) driven tunnels. The length of the TBM tunnel section is approximately 4.2 km. The TBMs employed are double shield TBMs. Typical support to the segment ring while advancing a double shield TBM comprises of filling the excavated annulus between the ground and the segmental lining by injecting pea gravel, followed with primary grouting to fill between the pea gravel some distance behind the excavated face. The methodology adopted for the Legacy Way project, however, did not follow this typical approach, instead, two component grouting of the annulus was carried out.Where the annulus is typically filled with pea gravel, support is provided to the segment ring very close to the end of the tail shield, whereas in the case of two component grout this is not practical as the risk of grouting in the tail shield is high. The staging of the two component grout injection, the grout early age strength properties become key issues in ensuring that the segment ring leaving the TBM tail shield is stable and can support the necessary external loads.Two-component grout is a grout with two components, cementitious grout (component A) and accelerator (component B), commonly adopted for earth pressure balance (EPB) TBM. The grout reaches its thixotropic state in a matter of seconds providing initial support for the segment rings. Manual injection of two component grout to fill the bore annulus was carried out in stages leaving a portion of the segment rings unsupported. Ring stability during TBM advance was provided by a combination of ram thrust and the segment circumferential joint shear connectors.This paper outlines the design considerations such as rock load derivation by probabilistic analysis carried out utilising the software JBlock, 3D finite element analyses using the software Strand7 for ring stability and the testing and back analysis of the shear connector load bearing behaviour. In particular, the actual available capacity of the shear connectors against their published capacity by supplier was discussed.CITATION:Mok, P and Norbert, M, 2014. Tunnel boring machine excavation stability – double shield tunnel boring machine advance with partially grouted annulus, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 51–62 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By E. C. Grunsky, B. W. Smee

"The development of low-cost, rapid multielement analytical techniques has generated large geochemical databases in many exploration programs. When a sampling program consists of several thousand samples, the resulting data matrix is enormous and effective interpretation using all of the elements individually becomes burdensome. However, the application of multivariate statistical techniques can extract geochemical patterns related to the underlying geology, weathering, alteration and mineralization. Imaging the results over topography enhances the interpretation of these patterns. Examples of this approach are shown from mineral exploration programs in Canada and Mexico. IntroductionThere has been a dramatic change in the effectiveness of using geochemical survey data in the past ten years. This is mostly due to:• lower cost of geochemical analysis;• lower detection limits;• new methods of multi-element analysis;• a marked decrease in the turnaround time;and• the intelligent use of computers in presenting geochemical data.Geochemical surveys commonly have two objectives: locating abnormal concentrations of ore-forming or pathfinder elements and characterizing the underlying host lithologies. Geochemical surveys often employ a wide range of sample media that may typically include whole rock lithogeochemistry, various soil horizons, till and basal till sampling, stream sediments, lake sediments, and various forms of weathered regolith. Each of these sample media will exhibit a unique element distribution that must be factored in the interpretation phase of a geochemical survey study. This can become a cumbersome process if univariate data handling methods are employed."

Jan 1, 2003

By Qinghua Gu, BUQING XUE, XUEXIAN LI, JIANGSHAN SONG, Qian Wang

Updating the openpit vehicle transportation network has the problem of being time consuming and low precision. To address this problem, a high-precision road network model construction method for unmanned vehicles in openpit mines is proposed. This method can be divided into two steps. In the first step, an improved deep learning image processing model named DeepLabv3+C (DeepLabv3+Concat) is presented, and the road information extracted by the DeepLabv3+C network is used to construct a three-dimensional model of the openpit mine road network. In the second step, aiming at the time-consuming problem of unmanned vehicles meeting in openpit mines, a vehicle meeting strategy is proposed. This strategy is used to guide the navigation of unmanned vehicles in openpit mines. At the end of the study, vehicle running simulation was carried out on the road network model using Unity, a 3D visualization simulation software. The high-precision unmanned road network model of openpit mines studied in this work can further promote the construction and development of smart mines by acting as a high-precision map for unmanned vehicles.

By W. Y. Gao

Diaojuntai Concentrator adopts a process of low intensity and high intensity magnetic separation and anionic reverse flotation, with all the concentrate from magnetic separation being treated by re-verse flotation to obtain a qualified final concentrate. The high reagent cost and energy consumption of the reverse flotation have led to a high concentrate cost. The test research on reducing the feed to the reverse flotation was therefore carried out. Based on the study of the properties of the ore sample, the concentrate of low intensity magnetic separation was screened at 0.076 mm and the undersize fraction was concentrated by concentrator with gravity and magnetic field. The results show that a qualified concentrate can be obtained at various rising current rate, pulsating current and power-on style, with the operation rate over 85%. The extraction of some part of qualified concentrate from the concentrate of low intensity magnetic separation by magnetic separation can reduce the feed to the reverse flotation by about 35% so as to reduce the production cost of concentrate.

Jan 1, 2014

By M. O. Serbousek

To further investigate the potential of precast concrete sets as a support medium for underground mines, the Bureau of Mines designed an eight-piece precast reinforced concrete drift set for a small opening. Twenty-two sets of three different member sizes were tested to destruction under two loading conditions. A discussion of the test results and typical failure patterns is presented.

Jan 1, 1969

By F. F. Peng

The raw-coal feeding system and the upward medium current flow in a dense-medium vessel (DMV) are, in addition to the residence time of particles in the separator, important factors for efficient coarse particle separation. The feed material from a raw coal screen and/or pre-wet screen merge with the major volume of circulating medium as push medium, guided by an adjustable submergence baffle plate deep fed into the separator for effective separation. The remaining volume of the circulating medium enters from the purge and drain hoppers at the bottom of the DMV. This generates a gentle upward medium current flow in the separator, which prevents dense medium stratification/settling and merges as part of the push medium. A two-dimensional, two-phase model developed using computational fluid dynamics (CFD) is used to describe the flow pattern and evaluate the function of the dip plate for understanding the mechanisms of particle separation in the separator. The particle movement in the DMV is also tracked to investigate the major operating parameters affecting the separation performance of the DMV. The simulation results of the DMV separation performance are validated by in-plant test data.

Jan 1, 2007

By Georges Houlachi, Akram Alfantazi, Maysam Mohammadi

Manganese ions in zinc electrowinning electrolytes form a protective MnO2 layer that ultimately decreases Pb contamination in the zinc product. In this study, the effect of dissolved Mn2+ on the electrochemical performance of Pb, Pb-Ca and composite Pb-MnO2 anodes was investigated. The properties of the MnO2 layer formed on these anodes were studied and compared. Potentiodynamic polarization and cyclic voltammetry experiments were performed in 180 g L-1 sulphuric acid to study the electrochemical reactions occurring on the anodes. The anodes were subjected to galvanostatic polarization at 50 mA cm-2. The morphology and uniformity of the MnO2 layer on the anodes were examined using scanning electron microscopy (SEM). Experimental results revealed that the MnO2 layer formed on the composite anode was more compact and uniform compared to that formed on the Pb and Pb-Ca anode. It was also observed that the cell mud formation rate, and consequently manganese ions consumption, depended on the anode type. Although initial formation of the MnO2 layer decreased the oxygen evolution overpotential, its growth might negatively affect electrocatalytic activity of the anodes.

Jan 1, 2014

By R. L. Wise

Heat content studies were conducted on burned shale, spent shale, and three grades of raw oil shale from the Green River Formation. Corrections were made for product enthalpies. The results were compared with previous work, indicating good agreement below retorting temperatures, but some differences at retorting temperatures. A general equation was developed relating heat content to oil-shale grade and temperature.

Jan 1, 1971

By M. Troyer

A coal shuttle car equipped with a pulsed laser optical ranging system to provide guidance for an automatic steering system was tested in production coal mining. Test results are presented for the two mines where testing took place, and some operator's reactions are included. Automatic steering control keeps the car cantered in an entry, and automatic turns are made at intersections as signaled by the operator. All other controls-tram, conveyor, brake, etc, remain manual and require operator control. Complete override of steering while in the automatic mode is retained by the operator, who may grab the steering wheel at any time and turn in opposition to the automatic signal by applying about 10 foot-pounds of torque.

Jan 1, 1976

By Mohammad. M. Khajeh

Rock mechanical properties are important parameters in geomechanical simulation. Considering stochastic heterogeneous models rather than conventional homogeneous layer cake models leads to more realistic simulation results and uncertainty assessment. These heterogeneous models are usually fine scale models generated by geostatistical techniques. Although considering high resolution property models is desirable, geomechanical simulation with a fine scale model is not computationally feasible for full?field, coupled geomechanical-flow simulation. Upscaling of property models is necessary to move from fine scale/high resolution property models to coarser scale/low resolution models appropriate for simulation. Local numerical upscaling was proposed by Khajeh et al. (2012) to describe the macroscopic elastic behavior of complex heterogeneous media and is expanded upon in this work. This numerical technique is not restricted to specific geologies as typical analytical techniques are. Moreover, transversely isotropic deformation is considered rather than the usual assumption of isotropic deformation. To compare the accuracy of the upscaling methodology, in this study shear strain is considered as the geomechanical response of a synthetic facies model and the response of the coarse scale model is compared to other conventional analytical averaging techniques. It is found that the numerical upscaling technique better approximates the geomechanical response of the fine scale model.

Jun 1, 2012