Search Documents

One of the most important goals of the experiments is to determine deformation and strength of the rock specimen under applying triaxial load, the status of failure condition is one of the subjects which can be used in soil mechanic and foundation engineering applications. To investigate the effect of confining pressure on the triaxial test, the rock has been considered as bonded-particles method and has been simulated by particle flow code three dimensions (PFC3D). This model, does not have pre-existing microcracks and all the particles have the same size (2 mm diameter), equal to the real specimen shape. To compare the mechanical behavior and failure pattern of the numerical and experimental results at uniaxial and triaxial tests at the same conditions, the Young's modulus, Possion's ratio as well as maximum axial stress have been considered. On the other hand, the microcracks growth and change of failure pattern at the modelling of the uniaxial and triaxial tests with different confining pressures up to failure point were reported. According to the experimental work, the number density of microcracks decreases from starting value and remains almost constant up to the failure beyond that point. The comparison of the numerical and experimental results of maximum axial stress and the Possion's ratio revealed good accordance. The initial number density of microcracks at the model was zero and increased while microcracking. Also, the sudden increment around the maximum stress was observed which is because of unstable growing of microcracks near the maximum stress. In all uniaxial and triaxial tests with different confining stresses, the number density of microcracks during the failure remains almost constant which can be considered as a proof of failure occurring in the model. The experimental results indicate the similar trend as well.

Nov 25, 2010

By Neil R. Burns, Michael Doggett

Abstract - The Nanisivik mine offers a unique opportunity to examine the economics of a mining scenario from its original feasibility study through to closure. In the early 1970s, the Strathcona Sound project (exploration around the Nanisivik mine) had advanced to the point where a significant mineralized body had been defined and a feasibility study was initiated. The study supported development of the Nanisivik mine, with government investment in regional infrastructure, and the mine was constructed and operated for 26 years. Many elements of the feasibility study were difficult to estimate because the project was unique in its high Arctic setting. As a result, many differences were found when comparing the actual mining data to the feasibility study. The majority of these differences were the result of an actual mine life of 26 years instead of the planned 12.5 years. Most of the mining costs were higher than estimated and production occurred at a much higher extraction rate than planned. On a constant dollar basis, the metal prices were, on average, below the feasibility estimates. For the most part, these differences balanced out, with the actual mining being only slightly more profitable than anticipated in the feasibility study.

Jan 1, 2004

By A. Erickson

The effectiveness of a loader-mounted fan on diesel vehicles combined with natural convection for ventilation of a dead heading (the patented Janelid system) was investigated experimentally. The results were obtained using CO2 as a tracer gas in a 1/4 scale model heading. Buoyant forces were scaled to establish similarity with full scale. For a loader moving in a typical load-haul-dump cycle, the loader-mounted fan reduced the tracer gas concentration by 26 percent compared with a reduction of 32 percent for a jet fan of four times the flow capacity.

Jan 1, 1981

In recent years there have been significant advances in computing power and programming technology, enabling more complicated processes to be modelled in greater detail. This has led to increased understanding of these complex processes, including mineral processing circuits. JKSimMet was developed over the past 35 years, incorporating outcomes from various research projects conducted at the Julius Kruttschnitt Mineral Research Centre (JKMRC), part of the Sustainable Minerals Institute at The University of Queensland. It is a steady-state software program that allows the user to mass balance, model fit and simulate crushing, grinding and classification circuits. JKSimFloat has been developed over the past 20 years, incorporating outcomes from the JKMRC and other institutions around the world through the AMIRA International P9 project ? The Optimisation and Simulation of Mineral Processing Circuits. It is also a steady-state software program, similar to JKSimMet, but is focused on analysing flotation circuits. Both programs have been used in a wide variety of optimisation and design projects over many years. This paper provides an overview of both JKSimMet and JKSimFloat and examples of how both programs have been used to better understand, develop and optimise mineral processing circuits around the world.

Feb 27, 2013

By Wayne I. van Drunick

"Energy balance modeling has recently been shown to be a competent tool in the estimation of SAG mill discharge rheology. Work performed by van Drunick and Moys (2001) validated the ability of an energybalance filter to estimate the slurry density from an operating SAG mill. The importance of rheological data is highlighted by several authors who show the effects on load behaviour and thus mill performance. Energy balance models were developed to account for the dynamic energies in the mill discharge sump. The models then made it possible to infer the mill discharge density. A sampling campaign was performed and the errors from the sump energy balance were within tolerable limits.Since the initial results were published, it has been decided to further develop the modeling techniques in order to focus on balancing the energies around the entire mill. The critical measurements for the energy balance will be the temperatures of all the streams entering and leaving the mill, including energy losses to the environment. Metso’s OCS© (Optimising Control System) currently controls the 3 SAG mills at Anglogold’s Mponeng Gold Plant (South Africa). The OCS has built-in Kalman filtering tools to effectively handle variances and noise in the models and the mill circuit data respectively. The new models are therefore constructed in the OCS platform, and will be run in parallel with Metso’s current modeling and filtering systems. The work is a collaborative effort between Anglogold, the University of the Witwatersrand and Metso. The benefits of energy modeling, compared to mass modeling, are that energy data are more accurately measurable than mass data. The inferred mill parameters can therefore be improved provided that a competent set of models is produced to process the (accurate) thermal measurements."

Jan 1, 2003

By C. J. Roos

Ground-engaging tools are used to prevent damage to the main components of earth-moving equipment. These tools consist of everything from shovel teeth to replaceable drill bits to dozer wear plates. The costs of these "consumable" items are increasing with the costs of raw materials. This project developed a tool to be used by Newmont Mining Corp. to predict the consumption of excavator teeth at a particular mine site. This paper presents the results of the Montana Tech research project in which an equation was developed to predict excavator teeth consumption based on production rates and rock properties.

Jan 1, 2010

By D. Bitzios, A. Gracia, V. Meggiolaro, J. D. Baker

Synthesis report on a project carried out under the EC-funded BRITE-EURAM programme. A large deposit in Spain and several smaller ones in Greece and Sweden were investigated. Beneficiation testwork, including the development of an innovative wet circuit, was undertaken in Italy. The Spanish Ilustracion deposit lies occurs in thin, white layers throughout a zone 35-40 m thick and 1.5 km long, in laminated calcsilicates. Total resources of more than 100 000 000 t include proven open-pittable reserves of 4 500 000 t averaging 35% wollastonite. The beneficiated product is suitable for various applications, including ceramics. The Swedish and Greek marble-hosted skarn deposits include Albatross, with 2 500 000 t of reserves at 30% wollastonite, and Panorama, with reserves estimated at more than 700 000 t

Jun 21, 1905

By Lee W. Abramson

Performing risk analyses on tunnel projects has become common place and on many projects it is required from an owner or regulatory perspective. After the project is planned, designed and constructed, the data concerning identified risks, assumptions, costs, probabilities and mitigations is generally long forgotten and buried in some file somewhere. A study was performed comparing predicted risks versus actual events on several recently constructed tunnel projects. Probabilities and costs for selectively common risks on tunnel projects have been studied and re-evaluated. Conclusions are presented that can guide future projects and the veracity of the tunnel risk analyses performed.

By Konstantin Fedotov, Victor Beloborodov, Anatoly Potyomkin

"There are areas in Russia, which cover huge territories and they are north, and Siberia. These difficult to access regions with cold climate are rich in a great number of distant deposits of valuable and rare metals, gold and platinum. The development of such deposits requires highly effective technologies of mineral processing which could be realized in modular and quick-built processing plants.The work presented includes the results of long term research in the development of new technologies of processing of zirconium (in the form of rare mineral Baddeleyite – natural zirconium dioxide) bearing ore of the Kovdor deposit which is located in the Polar region of the Kola peninsular and also in Siberia deposits of of ledge ores of gold."

Jan 1, 2003

By A. Kapito

The formation of bainite in steel is dependent on the size of the casting, the heat treatment, and the alloying elements. It is difficult to obtain a fully bainitic microstructure in steels during heat treatment because of its close proximity to the martensite (a?) reaction. The ferrite (a) and pearlite reactions in steels are also rapid and shield the bainite reaction. Alloying elements therefore need to be added to separate the bainite reaction. Boron (B) and molybdenum (Mo) are key elements added to bainitic steels because of their ability to retard the a reaction. Other elements used in the production of bainitic steels are silicon (Si), chromium (Cr), manganese (Mn), and titanium (Ti). In this paper we investigate the effect of alloying elements on the bainite reaction through the use of dilatometry. Dilatometry is a technique that determines phase transformations in the steel and through which continuous cooling transformation (CCT) curves can then be developed. Some initial results are presented of an ongoing study on the development of bainitic steels for railway wheel applications.

Jan 1, 2013

By T. Soejima

In recent years, there has been a tendency in the field of foundation piling works to utilize piles of greater bearing capacity in order to meet increasing height and weight of modern building as a means of saving of piling cost. To satisfy these requirement, a new technique for large diameter bell bottom cast-in-place piling has been developed utilizing multi-head reverse circulation drilling system.

Jan 1, 2010

By Cameron J. Clayton

Cumberland Resources Ltd. is currently planning to develop the Meadowbank Gold Project located some 70 km north of Baker Lake, Nunavut in the eastern Canadian Arctic region. The Meadowbank Gold Project currently consists of up to 6 main gold bearing deposits within relatively close proximity to one another which are planned to be mined primarily as a truck-and-shovel open pit operation and using conventional gold milling and extraction. The mining plan indicates that approximately 20 million tonnes of ore will be mined over a mine life of 8 to 10 years. The operation will generate approximately 160 million tonnes of mine waste rock and about 20 million tonnes of tailings. The site is located in an area of continuous permafrost with mean annual average air temperature of -11 °C and average annual precipitation in the range of 100 to 200 mm. Lakes cover a large portion of the site, including some of the ore deposits. The location of the site, and the physical environment, pose challenges to development. This paper presents some of the designs considered to effectively manage and utilize the waste products of mining at the project.

May 1, 2004

By Wang Xiaotie, Yu Yongfu, Che Liping, Zhang Fuguang

The flotation process of native Rare Earth minerals such as bastnasite, monazite, mixed minerals of bastnasite and monazite, using the new effective collector Dh was studied in this paper, respectively, and the flotation properties are described. The good qualities of the new collector Dh were revealed through comparing with other collector of Rare Earth minerals. The test results of different ore samples show that at moderate pulp pH (8.5-9.5), Rare earth minerals can be effectively separated from barium, calcium and silicon bearing intergrowth minerals (barite, calcite and silicate minerals) and high quality Rare Earth concentrates can be obtained successfully by the new collector Dh, acid silica gel, turpentine and reagents fitting together rationally. In order to determine optimum technical conditions, the effect of pulp pH, pulp temperature, pulp density and the effect of dosage of reagents (Dh and acid silica gel) on the flotation were investigated in the test.

Jan 1, 2003

By Francis J. Kiessling

Energy and the conversion of potential energy into alternate forms is becoming a topic of household conversation for a larger segment of the world's population as mankind's desire for products derived from the vast array of technological developments continues to expand. The world's use of steel and the high energy consumption related to the production of steel promotes an awareness of the limitations of existing technology and a search for more economical alternates. Terminology such as (BF) Blast Furnace, (BOP) Basic Oxygen Furnace, (EAF) Electric ARC Furnace, (DR) Direct Reduction, (DRI) Direct Reduced Iron and (FC) form coke is becoming commonplace as alternates are being sought to alleviate the energy crunch. Coke production by various methods was developed as early as the seventeenth century in Europe to replace the disappearing hardwood forests that supplied the initial blast furnace fuel in the form of charcoal. In 1880, the Semet Solvay by-product coke oven design was introduced to the United States at Syracuse, New York, to supply coke for use in the production of soda ash, coke oven gas and its by products as the primary source of many organic processes. Although the Semet Solvay coke oven has not been marketed for decades, these coke oven batteries are in use today producing metallurgical coke, coke oven gas, and related by-products.

Jan 1, 1980

By Anuj K. Singh, Shuvranshu Rout, Manos De

"Foundation for tracks of coke transfer car and dust extraction pipe was designed as series of isolated foundations spaced at 11.0m along length of coke oven battery resting on soil at depth of 2.5m. In one region the foundations are close to adjacent 12m deep underground junction house. Five foundations in this zone were constructed on backfilled soil without proper compaction instead of engineering soil fill or concrete fill. The foundations settled under loads and the supported frame structure tilted after equipment erection and during trials endangering the safety of the structure and equipment operation. The distorted structure had to be rectified in-situ by arresting settlement. In order to stabilize the foundation and supported structure the supporting soil had to be strengthened in situ without any dismantling, reconstruction and adverse effect to equipment operation. This paper presents the case study on the evaluation of defects for the foundation failure and analysis of the problem, proposed rectification of the situation by appropriate soil stabilization scheme, monitoring of the stabilization operations and verification of effectiveness of the rectification work by measurement of settlements. The implemented solution has ensured safety of the structure and equipment without any adverse impact on normal operation.INTRODUCTION AND BACKGROUNDNew Coke Oven Battery was being installed for an integrated Steel Plant. The hot coke from oven is pushed out after completion of coking process through a coke transfer car onto a hot coke receiving car. The coke transfer car runs on rail track parallel to the line of ovens forming the coke oven battery. One rail is supported on the structure of the operating platform of the battery and the second rail rests on independent structure of track beams. A large diameter pipe for extraction of the dust emitted during coke pushing operation is also supported on the same structure that supports the track beams. The entire structure rests on columns spaced at approximately 11.0m along the length of the battery. The columns transfer load to ground through individual foundations resting on competent subsoil strata.Two sets of foundations for the rail track beam support and dust extraction pipe support are adjacent to deep underground junction house of coke carrying conveyor. The depth of the pit for the junction house is 12m. The layout and arrangement of the foundations in this region around the junction house (JH-1) is shown in the “Figs. 1a, 1b”."

Jan 1, 2017

By John E. Trombly

System objectives and design criteria for an in-mine ULF radio paging system are discussed Coding formats, frequency and bandwidth selection criteria leading to the system design are discussed. The prototype call alert transmitter and pocket page receiver is functionally described. The report includes circuit descriptions, schematics, parts lists, printed circuit fabrication and assembly drawings. The report concludes with an estimate of the manufacturing cost for each assembly.

Jan 1, 2011

By J L. Mauk

The Favona low-sulfidation epithermal deposit in the Hauraki Goldfield is less than one kilometre southeast of the world-class Waihi deposit. The veins are hosted by Miocene andesite of the Waipupu Formation, have a total strike length of over 900 m, a vertical extent of at least 350 m and are on average 1-3 m wide. Individual veins have been traced for 200 m with vein widths up to 25 m. The dominant vein textures are massive, crustiform and colloform banded veins and vein breccias, with subsidiary textures including comb, zonal, flamboyant, lattice-bladed, ghost-bladed, microbotryoidal, feathery, ripple and dune, and mosaic. Quartz is the dominant gangue mineral in the veins at Favona. Accessory gangue minerals include pyrite, chlorite, adularia, illite, calcite, and apatite. Electrum is the only gold-bearing mineral and is associated with acanthite, tetrahedrite, pyrite, sphalerite, chalcopyrite, and rare galena. Whole rock geochemical analyses indicate that gold grades correlate with textures/vein types. The highest gold and silver grades are associated with vein breccias and banded veins, with the former containing 28 g/t Au and 136 g/t Ag on average. To date, veins with significant base metal sulfide minerals, and massive and crystalline quartz veins lack significant precious metals (Au and Ag), except for one banded base metal sulfide-rich vein at Favona. An overall zonation of the veins exists, with base metal sulfide minerals dominant at depth (1050 m RL) of the system are characterised by massive quartz veins.Fluid inclusions from a total of 31 quartz, amethyst, and platy calcite veins reveal homogenisation temperatures of ~190-250¦C, with final ice melting temperatures between 0.0 and -0.8. Ice melting temperatures correspond to apparent salinities of 18O value of the water that formed these veins is approximately -4.3 per mil, which is similar to meteoric water-dominated, near neutral chloride fluids in geothermal systems in the Taupo Volcanic Zone.

Jan 1, 2002

By J. A. Organiscak

In the United States, respirable coal mine dust exposures are limited to a 2 mg/m3 time weighted average for a working shift. If the silica content of the sample exceeds 5 percent, the 2 mg/m3 standard is reduced according to 10- (% silica) to limit silica dust exposures to 100 µg/m3. Examinations of dust sampling data collected by the federal coal mine inspectorate showed that roof bolter occupations continue to be at risk for overexposure to respirable silica dust. Testing at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health assessed the effectiveness of a canopy air curtain for controlling occupational exposures to respirable silica and coal dusts. Initial testing found that zones of higher velocity airflow shrank as distance beneath the canopy increased. This suggested that protection from occupational dust exposures would likely decrease as distance beneath the canopy increased. Further testing revealed that coal dust reduction efficiencies were most affected by changes in interference air velocity and, to a lesser extent, changes in canopy air quantity. However, respirable silica dust percentages under the canopy were not affected by such changes and, in fact, were not significantly different from silica percentages measured outside the canopy. This implied that the air curtain was equally effective on both respirable coal and respirable silica dust particles.

By M. J. Ferrante

The Bureau of Mines investigated the applicability of the freeze-drying technique for preparing dispersion-strengthened tungsten powders suitable for conversion by powder metallurgy into materials which might have improved high-temperature strength. Extruded rods from compacts of tungsten-5 vol pct thoria had at 1,650° C a tensile strength of 30,300 psi and a 10-hour stress-rupture strength of 12,700 psi, These are slightly below those measured for swaged rods of commercial tungsten-3.7 vol pct thoria. Only those tungsten-thoria dispersions containing a stoichiometric deficiency of oxygen yielded a significant strengthening effect. A low-melting eutectic formed in extruded tungsten dispersions containing either zirconia or yttria, which caused a lowering of the tensile strengths. These tensile strengths were only slightly higher than strengths of elemental tungsten made from commercial powder having a particle size of 2.4 microns (Fisher subsieve). Sheet made from this commercial tungsten had a slightly higher tensile strength than tungsten made by freeze drying, but the freeze-dried tungsten sheet had a lower recrystallization temperature, a lower ductile-to-brittle transition temperature, and a higher purity.

Jan 1, 1971

This paper reviews rehabilitation, closure, and post-closure management of the Tui, Golden Cross, and Martha Mines, all of which are located in the Waikato Region of New Zealand. There was no requirement for rehabilitation of the Tui mine, which was abandoned in 1973. There was a requirement to rehabilitate the Golden Cross mine. Mining at that site ceased in 1997, and rehabilitation is now well advanced. When first approved, there were some requirements for rehabilitation of the Martha Mine, but when reconsented in 1998, those were extended, and in addition a requirement for post-closure management was included. As a result, a Trust, funded by the mining company, has been established to take long-term responsibility for the site following completion of closure. The different rehabilitation/closure requirements at each of these sites illustrates that we have learnt something from the experiences of the past.

Jan 1, 2003