Search Documents

By Robert R. MacLachlan

New underground mining technology is evolving through the use of large-diameter bore holes containing individually restricted charge weights. This article presents summary observations on cube-root scaling trials using single and rows of charge blasting in sand and in frozen ground. These observations have some bearing on the evolving underground practice, especially where charges of appropriate geometry are used.

Jan 1, 1978

By T. G. Joseph

ABSTRACT: The Canadian oil sands provide some of the harshest mining conditions in the world. Asoperations demand ever bigger tools, the toll on large mobile mining equipment is high, with structural life often half of that expected. Soft ground conditions predominantly lead to fatigue failure scenarios, poor stability, and inconsistent payload evaluations. These challenges are not solely a concern for Canadian oil sands mines; there are far-reaching implications for surface mining equipment in any poor ground-operating environment. This paper focuses on the basics of payload evaluation, motion response, and a simple estimate of structural life for haulers.

Jan 1, 2011

By M. Ghamgosar, Erarslan N.

Rock cutting includes many unknown parameters which result in different consequences of the different cutting conditions. However, based on the current suggested models for rock cutting, there are some critical parameters that control the fracture initiation and propagation in the rock domain. In general, there are two major cutting tools are used in rock cutting: drag bits and indenters. Different mechanical attacks of cutters result in different fracture models. For example drag bits break the rock parallel to the rock surface, which is called ‘undercutting’ while indenters cut rocks by pressing normal to the rock surface. Both tools cause rock failure by inducing tensile cracks in the rock. However, drag bits induce more tensile cracks compared with the indenters. The full benefits of improvement in rock cutting efficiency will arise from a clear understanding of rock fracture mechanics principles. Therefore, fracture mechanics principles will be applied to the rock cutting as the rock fragmentation process is based on the rock fracturing. The Oscillating Disc Cutting (ODC) has more advantages than drag bits and disc cutters. The forces transmitted back through the cutting head are much lower with ODC. Although ODC attacks rock in much the same way as drag bits, a combination of the oscillating action of the cutter and the undercutting mode produces the lower cutting forces and causes rock fatigue. Fatigue phenomenon in rock has advantages for the rock breaking by applying less effort and energy due to the cyclic loading. The aim of this study is using the Extended Finite Elements Analyses (XEFM) numerical modelling for simulating the ODC cutting with different cyclic loading conditions. An accurate prediction of numerical investigation requires detail laboratory experiments. A series of laboratory tests were performed to obtain the fracture toughness values of our Monsonite rock samples under various cyclic amplitude and frequency values. The numerical results showed different types fatigue damage mechanisms due to the various cyclic loading conditions. Thus, modelling and understanding the crack propagation behaviour depending on different amplitude and frequencies are believed very important for the dynamic rock cutting researches and rock cutting machine manufacturers.

Jan 1, 2015

By Neda Zangeneh

Production efficiency from low permeability gas shales require techniques to optimize hydraulic fracture completions. One completion strategy involves the simultaneous or near simultaneous hydraulic fracturing of multiple horizontal wells to maximize the fracture network area and stimulated reservoir volume. However, changes to the in-situ stress field caused by an earlier hydrofrac on subsequent hydraulic fractures are not accounted for in traditional hydrofrac design calculations. Presented here are the results from a set of transient, coupled hydro-mechanical simulations of a rock mass containing two wellbores using the discontinuum-based distinct-element method. The results demonstrate the influence of stress-shadows generated by a hydraulic fracture on the development of subsequent hydrofracs from an adjacent well. It is shown here that these interactions have the potential to change the size and effectiveness of the hydraulic fracture stimulation by changing the extent of the hydraulic fracture around the secondary well.

Jun 1, 2012

By E. Ghali, B. Arsenault

Aluminum alloys play an important role in the manufacturing of air and ground vehicles. However, with such alloys, corrosion damage is often found on structural components subjected to fatigue loading. The alloying provides large benefit in terms of the high specific tensile strength (ultimate strength/density ratio) to the aluminum alloy but causes the aluminum alloy to be more sensitive to localized corrosion due to complex microscopic heterogeneities such as secondary phases. This paper investigates thermal spray coating namely arc spraying to evaluate the protection against environmentally assisted cracking (EAC) and localized corrosion on Aircraft structural 7075 T651 aluminum alloys. In particular, EAC and pitting corrosion at the interface coating-substrate are a challenge for thermal spray protective coatings on aluminum alloys under cyclic load and immersion. To address these issues, different surface preparation techniques prior to arc spraying were considered such as chemical de-oxidation, laser ablation, shot peening and grit blasting. Results indicate that surface preparation and improved coating process parameters play an important role to provide a coating conferring a protection against both localized corrosion and EAC.

Jan 1, 2006

By A. Ghasemi

An alumina-silica coating was deposited on a nickel substrate by sol-gel process, and the structures and composition were evaluated, The sols were made from aluminium and silicon alkoxide, and an acid catalyst including HCl, To produce adherent silica coatings on nickel, various additives such as surfactant, viscose additive and drying control chemical additives were introduced to the system, and appropriate drying and firing cycles were applied after dipping in solution. The hot corrosion and oxidation resistance of the coating at different temperatures were investigated, The structure and uniformity of the coatings were examined by scanning electron microscopy (SEM), The results indicate that a uniform coating of alumina silica can be produced on a nickel substrate by optimizing the composition and process variables of the sol. Coatings can protect substrates from oxidation and hot corrosion at different temperature up to 1000°C, but is not very effective for hot-corrosion resistance at 1000°C.

Jan 1, 2005

By W. V. McKnight

The paper discusses the equipment and methods used to establish some of the characteristics of a braking system. Some typical tests are described and an explanation of the approach used to derive information from the recorder charts is given.

Jan 1, 1966

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

"This contribution is concerned with adaptive processing decisions, where the process parameters are optimally adapted to the varying properties of the material input stream. Our starting point is the geometallurgical paradigm that the varying properties of the input stream are considered known e.g. from a geometallurgical model of the mined ore body, and optimal processing parameters are computed from them, by finding the parameter seaming optimal in a computer simulation.This approach however has to work with a lot of uncertainties: The prediction of the geometallurgical ore parameters can only be done with some geostatistical uncertainty. The parameters themselves are only proxies for true ore properties. Model prediction can differ relevantly from actual process results, due to model simplifications. Due to these uncertainties the computed processing choices can turn out to be inferior to simple non-adaptive processing. In this contribution we focus on the uncertainty of the ore properties and analyse this effect systematically, by modelling this uncertainty effect mathematically and in computer simulations. The most important findings are:(a) Processing choices not taking into account the uncertainty sometimes even perform worse than simple non-adaptive processing, for the sole reason of ignoring the uncertainty effect.(b) Ore properties, not adequately reflected in the ore description, might require different approaches, in which the observed processing behaviour feeds back into process control.(c) Bayesian decision theory allows computing optimal processing choices combining the information from the mine (geostatistical predictions) and from the process feedback. These choices give much more robust choices and do not suffer from the drawbacks described for the simple approach we started from.These new approaches can substantially improve the performance of adaptive processing in existing plants."

Jan 1, 2016

By John Lund

INTRODUCTION GOLD-BEARING placers of Alaska and the Yukon Territories are buried under a layer of permanently frozen alluvial overburden, or 'muck', which varies in depth from twenty to one hundred feet. The placers, and the decomposed bedrock layers upon which they are deposited, are also permanently frozen. During the summer, surface muck which is exposed to the sun will thaw, but only to a depth of a few feet. To reach a valuable deposit, the frozen overburden must be either penetrated with shafts, or stripped from the deposit entirely. In either case, before the placer can be mined, it must be thawed. At modern dredging operations, the frozen muck is stripped from the placer by powerful jets of water from hydraulic giants. The placer, and several feet of decomposed bed-rock, are then thawed by forcing water through narrow pipes which have been driven into the deposit. Other methods of thawing frozen placers were used extensively during the early years of the Klondike 'gold rush', but experimentation later proved that creek water at its natural summer temperature was a more effective and economical thawing medium than any other which had been used. EVOLUTION OF COLD WATER THAWING Early prospectors of the far north reached placers by digging shafts through the frozen muck. They then thawed the placer sand and gravel by building wood fires at the bottom of the shafts.

Jan 1, 1951

By G. T. Lapidus, O. J. Solis-Marcial

Currently, ores with high-grades of copper oxides and secondary sulfides have become increasingly scarce, which has encouraged industry to look for alternative raw materials to obtain copper. The problem is that primary sulfides are difficult to dissolve at near ambient conditions. Proposed hydrometallurgical processes have not been implemented beyond a pilot or demonstration scale. One of the principal disadvantages is that the majority of these processes are not viable with ores that contain less than 4% copper. One of the more recently proposed techniques involves the use of organic solvents in the dissolution of copper concentrates with a chalcopyrite content of between 20 and 30%, which has shown high efficiency. The present research explores the ability of this process to leach copper from low grade chalcopyritic ores (<4% Cu) at different temperatures ranging from 20 to 50°C. It was found that depending on the temperature, high percentages of copper were extracted in 40 to 100 minutes, using different oxidants. Additionally, distinct leaching behavior was observed with each oxidizing agent. In some cases, the extraction kinetics adjusted to the diffusion controlled shrinking core model.

Jan 1, 2014

By Hans Lundberg

Magnetic methods have been used for more than three hundred years in prospecting for magnetic ores. More recently magnetic methods have been used for finding salt domes and studying certain geological formations. A number of instruments have been developed and substantial improvements made as to their sensitiveness and accuracy. Papers and articles written on magnetic methods are generally elaborate and technical, and the average prospector finds it difficult to obtain the necessary information as to how to operate the simple magnetic instruments to the best advantage. The miner&apos;s compass, dip needle, and inclinator are, indeed, very useful instruments and are easy to handle, and a great deal of valuable information can be gained if the instrument is properly operated and the results correctly interpreted. The lack of knowledge of the fundamental principles, however, has caused a great deal of disappointment. Other and more elaborate geophysical methods have recently come into the limelight, and the prospectors seem to have lost a great deal of interest in the dip needle. This is much to be regretted, because magnetic methods have a particular field of use. The present article is an attempt to help the prospector regain interest in the magnetic instruments and to show the use and application of a simple magnetic survey. If the prospector expects some useful help in his work, he must, of course, know the instrument, know how to take the readings, and know how to plot and interpret the observations.

Jan 1, 1929

By A. F. Robertson

FOR several years, the rock-burst question has been given serious consideration by the operating staff at Wright-Hargreaves mine and, as a result of observations and experiences, several different methods of mining have been developed which are now in use in various parts of the mine. These are described in the following pages. It should be emphasized, how-ever, that these methods, and the views expressed in this paper, are based solely on conditions at Wright-Hargreaves mine. Such conditions may or may not be similar to those obtaining in other mines in the Kirkland Lake area, where ore occurrences, veins, wall-rock, faulting, intrusives, etc., may be entirely different. Size and shape of ore-bodies, composition of the ore-bodies and their surrounding rocks, locations of intrusives and sedimentary rocks, and direction, dip, and strength of faults, all introduce problems that are peculiar to each individual mine. Ground failure&apos; in coal and metal mines is not at all unusual. A variety of systems of mining have been developed to delay movement of large or small blocks of ground, or, in some instances, to take advantage of the fact that ground movement, due to mining operations, is unavoidable. Ground failure may be either slow collapse or it may take place with explosive violence. It is principally with the latter condition that we are concerned in the mines of the Kirkland Lake district.

Jan 1, 1939

By B. Schulz, T. Leißner, R. G. Merker

"Ores enriched in critical rare earth elements (CREE) keep on being of particular interest. The CREE are Nd, Eu, Tb, Dy, including Y. In conjunction with beneficiation tests on Y-mineral bearing flotation tailings of complicated mineralogy, the Mineral Liberation Analyses (MLA) was used to work out processing characteristics fraction-wise in terms of modal mineralogy, mineral recovery, locking and liberation, and particle size.Size fractions from mechanical sieving (“real fractions”) as well as fractions created virtually by using filters on the MLA-data of the unsieved head material (“virtual fractions”) were investigated comparatively thereby. The ""virtual-sizing-approach"" features a much simpler sample preparation procedure and considerably lower cost if a fraction-wise investigation of a head sample is needed. It can be conveniently applied to intimately locked ores needing a fine grinding to a particle size distribution (PSD) range below 25 microns for instance. However, its practical use is sometimes disputed in terms of the reliability of the results. Results are shown for the main Y-bearing mineral xenotime and selected main gangue minerals of a low grade REE-ore.The influence of sample representativeness, sample preparation and particle counting statistics turned out to be of crucial importance. Given that all preconditions for reliable results are met, locking characteristics, modal mineralogy, and even PSD trends can be read from virtual fractions.The authors encourage processing engineers to use the virtual approach. They propose practical measures to improve the reliability of the MLA results, identify and tackle conflicting results, and mitigate evaluation problems that may arise."

Jan 1, 2016

By B. P. Verma, K. N. Sinha, N. M. Raju, B. Singh

The paper describes a new method of grouting bolts developed at the Central Mining Research Station at Dhanbad in India. This method makes use of wire-mesh sleeve instead of the expensive metal tube to insert the cement mortar into the drill hole. The field trials confirmed that the method is cheap and an effective system of support.

Jan 1, 1972

By B. B. Adhikari, S. Alam, Ohto Kawakita, Abe Pangeni

Effective recovery of gold was investigated by using adsorption gels prepared from pure cellulose, cotton and paper by treating with concentrated sulfuric acid. Only gold was adsorbed with extraordinary high loading capacity from varying concentrations of hydrochloric acid separated from other precious metals and base metals. The formation of fine powders of metallic gold was visually observed, which is attributable to the selective reduction of gold (III) ion to metallic gold clue to its high oxidation-reduction potential. Recovery of gold from the leach liquor of hydrochloric acid of circuit boards from spent mobile phones was attempted using pure cellulose gel.

Jan 1, 2011

By M. A. Golozar

Partially stabilized zirconia (PSZ) has been proven to be an excellent candidate as a thermal barrier coating (TBC) for hot sections in, for instance, heat or internal engines and gas turbine parts. The main functions of these coatings are reduction of heat losses, reduction of fuel consumption, increasing efficiency, and extending durability and life. One of the main problems involved is wear behavior in the development of such coatings for these applications. Using air plasma spraying (APS) technique, conventional and nanostructured 8 wt % yttria partially stabilized zirconia (Y-PSZ) coatings were deposited on austenitic stainless steel (AISI 304) disc-shaped substrates. The coated substrates were subjected to pin-on-disc wear tests, using 10 mm silicon nitride and zirconia balls as the pin. The coefficient of friction was recorded in real time. The weight loss of coated substrates was measured. Coatings were characterized before and after being subjected to wear testing by various techniques including optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD). Effects of various experimental parameters such as wear distance, test temperature, and counterface material were also investigated. Results obtained revealed that, regardless of experimental conditions applied, the nanostructured zirconia coating shows better wear and tribological properties than those of the conventional one.

Jan 1, 2005

By A. Bouajila1

Minerals processing organisations will be more and more under intense competitive pressure. Major changes are being experienced with intense respect to resources, processes, production strategies and markets. As result of international competition, only the most productive and cost-effective operations will survive. That is why operators in the minerals industry have always aimed to obtain better performance from their processes along the mineral extraction cycle starting from exploration up to the smelting step if any. A principal ingredient and perhaps the most important one in the process of evolution toward improved productivity is the achievement and implementation of an error-free production synonym of an ignorance-free operation. This is, at the same time, a guarantee for quality, a minimising factor for waste materials production, handling and disposal, and a maximising factor for labour utilisation. The notion of ?error or ignorance-free? -usually identified as a ?made in Japan? manufacturing mythology, will sound, at first impression, like a pious ideal, to be striven for but impossible to attain. Nevertheless, the introduction of measurement and detection technology in the minerals industry along the last century should benefit from the today?s sensors and control systems that explosively expanded beyond their traditional production base into far-ranging commercial ventures. The fastness and spread of those technologies will play an important role in the survival of innovative plants. Their role in information assimilation, and control of operations to maintain an error-free production environment, will help many plants to stay effective on their competitive course. In this paper the feasibility of the zero process ignorance concept as applied to the comminution circuits will be discussed and the challenge behind this ambitious move toward improved productivity will be outlined. Examples of pre-competitive R&D projects started at COREM in order to fulfil this prerogative will be presented.

May 1, 2001

By Martin Encinas, Jesús L. Valenzuela, Jose R. Parga, Salvador Aguayo, Roy G. Lewis

Continuous laboratory solvent extraction of gold from cyanide solutions using LIX?79 guanidine based extractant has been investigated. Different variables that affected the selectivity and extraction include aqueous pH, extractant concentration, and modifier concentration. The extraction isotherms of the aurocyanide complex with respect to the other cyano anions were compared, and the following order of selectivity Au > Ag > Zn > Cu > Fe was observed. According to the pH isotherms, aurocyanide can be extracted in an alkaline media, and a better separation with respect to the other cyanoanions was obtained in the pH range 10.5-11.2. From the McCabe Thiele diagrams, better recovery was predicted when using LIX?79 extractant and tridecanol modifier at 10 vol.%. Stripping of the gold from the loaded organic was carried out at pH > 12 using NaOH and NaCN solution. The continuous tests indicate that a two-stage extraction followed by a single stage strip is adequate to obtain an overall process efficiency of >90%. Better results were obtained using a copper wash stage before gold stripping.

Jan 1, 2014

By C. C. Li

Traditionally, strong and stiff devices, such as fully encapsulated rebar bolts and concrete lining and arches, are preferred for underground rock support. The attention is paid to the strength of the devices in such support designs. It has been observed in engineering practice that support systems composed of stiff devices are often subjected to premature failure in high stress rock conditions. In the past decade, yield support devices have been employed to improve the performance of rock support systems. A rock support system usually consists of both internal and external devices that are installed within the rock mass and on the free surface of the rock, respectively. Great efforts have been made to make support devices yieldable in the past years, but the efforts are focused on different aspects in the tunneling and mining branches. In the tunneling branch, the focus has been put on the development of external yield devices, such as Lining Stress Controller (LSC), Honeycomb element and compressible concrete, which are embedded in shotcrete liners, while in the mining industry the efforts has been on the development of yield rockbolts, such as the cone bolt and the D-Bolt. The internal and external support devices are not compatible in their deformation capacities in the current rock support systems even though yield devices have been employed. All the devices in a support system should be deformable and compatible in deformation capacity. With such a support system, premature failure of individual support devices could be avoided and the service life of the support system is prolonged. It is a trend at present to take into account the energy absorption capacity, instead of simply the strength, of support devices in rock support design.

Jan 1, 2015