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By M Wimmer

LKAB operates two underground iron ore mines located in the northern part of Sweden, both using sublevel caving (SLC) as the mining method. Knowledge of the mechanisms of gravity flow is important since it affects both ore recovery and waste dilution. This paper describes results from a large-scale field test carried out at the Kiruna mine with a focus on gravity flow. It is part of Work Package 2 in the I2Mine project financed by the EU. A total of ten rings were blasted. Smart Markers based on radio frequency identification technology were used to monitor the gravity flow. An accurate delineation of the isolated extraction zone requires reliable detection of all recovered Smart Markers and precise knowledge of the 3D position of the markers within the burden. It was therefore necessary to carry out borehole deviation measurements (collar, alignment and trajectory). The blast performance was monitored by high-speed filming, near-field vibration monitoring and velocity of detonation measurements. Three-dimensional stereo images were taken from the drawpoint and the loaded bucket after each mucking cycle. Based upon that, fragmentation was assessed both in 2D and 3D. Furthermore, volumetric differences were determined at the drawpoint, which reflects the mobility of loaded material. For draw control, the Fe content is estimated by measuring weight and assuming a full bucket. The measured volume of rock in each bucket further improves this estimate. Possible flow disturbances occurring at the drawpoint were revealed by video recording. Two-dimensional laser scanning was carried out during mucking to track the position of the bucket and estimate the position and slope of the muck pile.The results from this test clearly show that the gravity flow in the large-scale sublevel cave in Kiruna mine is often of disturbed character. Standard draw occurred only in three rings and shallow draw in the remaining seven rings. In five cases, shallow draw developed towards standard draw, but occurred at rather late stages during extraction (70–125 per cent). The maximum width of the draw varied between 10 m and 13 m except for one ring (6 m). The draw reaches the cave rather early (5–25 per cent extraction) in shallow draw situations and much later (about 50 per cent) during standard draw. Waste originates from above in most cases, while more significant portions often occur at about 20–45 per cent extraction.All the results from this extensive field test are not yet fully analysed, and further field tests are planned. A more detailed insight into gravity flow in large-scale SLC and possible influence by drilling, blasting and the mucking procedure is expected in the future.CITATION:Nordqvist, A and Wimmer, M, 2016. Holistic approach to study gravity flow at the Kiruna sublevel caving mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 401–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By I T. Ross

Sampling drawpoints in block cave mines has been a contentious issue for many years. Doubts have been expressed as to the validity of the process used at most mines. This paper outlines the sampling practice commonly in use, discusses the resulting issues associated with reconciliation and drawpoint closure decisions. The paper also looks to the future and highlights issues for some block cave mining operations currently planned to have in the order of one thousand active drawpoints. It is likely that these operations will require a new approach to drawpoint sampling. There are several potential technologies currently available although some appear to be better suited than others to replace the current approaches. CITATION:Ross, I T, 2012. Sampling in block cave mines, in Proceedings Sampling 2012 , pp 81-86 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

Anticipating the increasing importance of establishing working conditions on a scientific basis, the Department of Labor created the Working Conditions Service. This service is distinct from that performed by the Mediation and Conciliation branch, which deals with working conditions and industrial relations as controversial issues between employers and employees. The work of the Service is conducted through three coordinated divisions; Division of Industrial Hygiene and Medicine, Division of Labor Administration, and Division of Safety Engineering. The Division of Industrial Hygiene and Medicine will develop standards of sanitation and medical practice in industries. The personnel of this Division is detailed from the United States Public Health Service. The Division of Labor Administration will advise employers as to employment systems and labor management policies, and assist in putting into operation standard policies.

Jan 2, 1919

By M. Sephton

Slat-band chains, currently manufactured from Type 430 ferritic stainless steel, are used as conveyors in various industries. A process to strengthen these chains?with the aim of prolonging the lifetime of the conveyors?was developed recently. The process entails heat treating the cold-worked chain at 475°C,strengthening the material by precipitation of the Cr-rich phase a? at relatively long periods of aging. In the present work, it was found that increasing the interstitial content by solution heat treatments (at 880°C or 930°C) prior to cold rolling and aging, causes an increase in strength at shorter aging times as a result of the precipitation of chromium-rich carbides and nitrides. The solution treatments can introduce martensite into the microstructure if carried out at a sufficiently high temperature. This, along with the deformation caused by cold work, also increases the strength. Corrosion resistance is not affected by the treatments, but ductility is lowered. However, calculated critical crack lengths indicate that solution treatment at a temperature below the Ac1allows for a larger critical flaw size, and that the lifetime of the chains will probably be determined by fatigue. Although the duration of the service of the chains are reportedly controlled by wear, with these treatments the tensile strength of the material is increased to within acceptable limits for conveyor chains. The tensile strength is an indication of the wear or abrasion resistance of a material. It is expected that after the treatments, the wear resistance will be improved, but since embrittlement occurs, the fatigue resistance is lowered. It is concluded that the preferred processing route for the chains would be solution treatment at 880°C, fast quenching to trap the interstitial atoms, cold rolling and then aging at 475°C for 8 minutes.

Jan 1, 1997

By M. M. Botz

There are currently more that 460 mines worldwide that utilize cyanide for gold and silver extraction. Despite this large number of cyanide-related mining operations, there have been no published accounts during the previous 25 years of the death of humans due to cyanide as a direct consequence of major mining-related environmental incidents. All published accounts of human deaths due to mining-related environmental incidents have been the result of physical inundation with tailings or waste rock materials. It appears that major mining-related environmental incidents have not been concentrated in any geographic location, are likely to occur regardless of the size of the mining company and do not occur more frequently with a specific type of mining activity. Several cyanide treatment and recovery technologies have been widely demonstrated to reliably control cyanide levels in mining solutions. With proper use of these technologies, tailings cyanide concentrations can be maintained at levels protective of wildlife while reducing the potential for adverse environmental incidents. The development of an international cyanide code of practice or management plan is recommended and should take into consideration the adoption of a weak-acid-dissociable (WAD) cyanide standard that maintains the levels entering a tailings impoundment below 50 mg/L.

Jan 1, 2001

By R. A. Perry

DURING 1943, supplies of lead, like those of most base metals, moved from a position of scarcity to one of ample supply for all possible war requirements. The principal worry in the market, as 1944 began, was that surplus stocks might increase too rapidly to maintain price stability. The problem of postwar stockpiling had definitely entered the picture. The end of the year finds the lead industry having met all use demands, but not without depleting stocks to a critical low in spite of heavy importations. The principal reason for this dangerously reduced stock position is lack of adequate man power, which, without question, has become the lead industry's number one problem. This condition became obvious about the middle of the year, after Selective Service placed in effect orders that no deferments would be given employees under 26 years of age, and to a complacent attitude toward the industry assumed by the War Manpower Commission. It has become progressively worse since then. The WPB continued its policy, started during 1943, of easing restrictions on materials to be used for maintenance, repairs, and operating supplies. The policy of premium payments established by the Metals Reserve Co. was continued and, in spite of expressions to the contrary, has proved quite satisfactory. In short, the Government continued its program of stimulating the lead industry in practically all

Jan 1, 1945

By Frank J. Susko

The U.S. Bureau of Mines has developed a computer model to describe a flotation process. Coal data from conventional flotation has been converted to a simple, two-parameter kinetic model developed by Reuter and van Deventer (1,2)3. Each set of coal data was represented by two constants, a and ß, and an average flotation rate. The success of the model was demonstrated when the calculated and experimental recoveries showed good correlation. The two-parameter model allows complex data to be defined much more efficiently than traditional knowledge-based models.

Jan 1, 2010

By Dale Zacherl, Andreas Buhr, Rainer Kockegey-Lorenz

"The microporous calcium hexaluminate insulating material SLA-92 has been introduced as an alternative to refractory ceramic fiber and other insulating refractory materials. Key properties associated with this product include: high chemical purity, long term high temperature stability up to 1500 °C, low thermal conductivity up to 1500 °C, and high thermal shock resistance. The properties of the new material and various applications in the steel and ceramic industries have been reported in previous papers. The current paper summarizes the industrial application experiences with innovative refractories based on SLA- 92 and discusses potential new applications in various manufacturing as well as energyrelated industries.IntroductionSLA-92 was introduced to the refractories industry in 1998 by van Garsel, et al. [1] as a new insulating raw material for high temperature applications, followed by investigations [2] of long term temperature stability for this new lightweight aggregate up to 1500°C.SLA-92 was developed as an innovative alternative to commonly used refractory ceramic fibers. It has unique properties regarding chemical purity and mineral composition and is a microporous, silica-free calcium hexaluminate (CA6 – mineral name: hibonite)."

Jan 1, 2010

By D. K. Steele

The domestic primary copper industry generates in excess of 600 million t of mining and mineral-processing waste annually. Most of the waste poses negligible environmental threat, but a small fraction, because of toxic or corrosive characteristics, may be subject to regulation under Subtitle C of the Resource Conservation and Recovery Act (RCRA) or other pertinent regulations. Among the wastes generated by various copper producers are flue dusts, slags, refinery-bleed solutions, and. acid-plant wastes. The U.S. Bureau of Mines (USBM) has researched methods to mitigate the environmental threat posed by copper-processing wastes while recovering valuable metals from these materials. Acid-leach processing of flue dusts has been demonstrated feasible along with sulfide treatment of liquid refinery wastes and acid-plant-bleed and gas-cleaning solutions to precipitate dissolved metals. In, addition, the feasibility of removing copper and molybdenum from slag, as well as stabilization of precipitated sulfide wastes by vitrification, have been investigated.

Jan 1, 2010

By T. Smales, P. L. Wright, K. Barron

The results of field measurements using an air injection technique to investigate the integrity of three pillars in the Mclntyre Mines Ltd. 114 seam at Crande Cache, Alberta, are reported. These pillars are shown to be stable and an estimate is made of the strength of these pillars. Using these results, together with Hustrulid's pillar strength formulae, a general pillar strength equation for the 114 seam is developed. This equation takes into account the probability of failure that may be deemed tolerable within the design requirements. The variation of the minimum pillar dimensions with depth below surface for uniform pillar layouts is then examined for a range of tolerable failure probabilities. A general equation of the form B = 2.60 +B Z relates the minimum pillar design width, B metres, with the overburden depth, Z metres, where B is a parameter related to the tolerable failure probability. This equation only applies for 3.05m high pillars with 6.lm wide entries. Finally, the question of what failure probability is tolerable within the design of mine pillars is discussed. This will depend on the support role required of that pillar and the anticipated period over which the pillar must perform that role. Five categories of coal mine pillars are defined, each with a somewhat different role to perform. Tentative design criteria in the form of "tolerable probabilities of failure" are suggested for four of these five categories of pillar. The fifth category of pillar has no reliable support function to perform and support must be obtained by other means.

Jan 1, 1983

By J. L. Luo, D. G. Ivey, A. H. Adeleke

Double-edge-notched flat tensile samples of X70 steel were used for both slow strain-rate testing (SSRT) and cyclic loading testing with the notch located in the zone of interest, i.e., the weld metal (WM), base metal (BM) and heat affected zone (HAZ). By using both optical and scanning electron microscopy, the stress corrosion cracking (SCC) behaviour with respect to crack morphology and various forms of microstructure was investigated. In all the samples considered, the mode of failure was predominantly transgranular with cleavage facets around the edges of the fracture surface. The BM, with a bainitic microstructure, had the highest resistance to SCC when compared with the mixed microstructures of acicular ferrite-primary ferrite and acicular ferrite-grain boundary ferrite observed in the WM and HAZ, respectively. The effect of microstructure on stress corrosion cracking behaviour is discussed based on experimental observations.

Jan 1, 2005

By D. P. Schlick

The German experience in dealing with the health hazard of respirable dust in underground mines is reported from first-hand observation in this Bureau of Mines paper. The report covers-- 1. The control of dust by water infusion, water spraying, and ventilation. 2. The sampling devices (tyndalloscope , konimeter , and BAT-I) and methods used to determine the dust concentrations in mines. 3. The systems of classifying hazardous and safe dust levels in mines. 4. The research facilities devoted to theoretical and applied work on mine dust and pneumoconiotic disease. Tile major research projects on dust and disease now underway in West Germany are outlined in an appendix.

Jan 1, 1970

By Robert M. Becker

This investigation (in five parts) extends the theory of sample reliability from a sample consisting of a fixed number of items to a sample consisting of a fixed amount of items. Examples of a fixed amount of items per sample are samples consisting of a fixed weight or a fixed volume of unequal size particles. The extension of the theory is confirmed by experimental laboratory sampling using standard procedures. The probability distribution functions (the binomial, hypergeometric, multinomial, generalized hypergeometric, and those here called the compound binomial and compound multimomial functions) are developed from fundamentals. Their distributions are generalized to include some measured characteristic of the items. Infinite population moments are derived from moment-generating functions, and finite population moments are developed from corresponding infinite population moments using a newly defined mathematical operation. The first three experimental moments in laboratory sampling to given weights of particles are compared with the theoretical moments of their corresponding compound mult.inomial distributions. The agreement is striking. The study is divided into five parts. Part 1 deals with probability or random sampling to n items and with all sampling to n items per sample from some one probability distribution. This is the area of sampling covered by well-known theory. Accordingly, the procedures may be different but many of the results are well known.

Dec 1, 1964

By Timothy Barton

The uniaxial compressive strength (UCS) is the most fundamental measurement used in geotechnical rock characterization for mine design. While there are standardized procedures for how to conduct UCS tests, there are no firm guidelines as to when to conduct them. However, it is well known that the strengths of at least some rocks can change during the time between when the core first comes up out of the hole and when it is prepared and tested in the lab. The goal of this NIOSH (National Institute for Occupational Safety and Health) study was to evaluate UCS changes occurring in a broad range of weak coal measure rocks over a one-year time span. The study found the highest moisture contents were measured when the core was fresh, immediately after it was taken from the hole. The specimens then dried rapidly over the next few weeks. Subsequently, sample moisture contents decreased slightly in the winter and increased in the summer in response to the ambient changes in humidity. The measured UCS of the core also changed during the year, apparently in response to changes in the moisture content. The UCS values from the dry, winter months were, on average, 60% higher than the values obtained when the core was fresh, and the summer UCS was approximately 11% lower than the winter UCS. These findings have implications for the use of UCS as an input parameter for both empirical and numerical mine design methods. UCS values of unprotected core tested weeks to months after drilling can be significantly stronger and indicate stronger roof sequences than warranted. In order to obtain the most representative and reliable UCS value, it is necessary to test the core, or wrap and seal it, at the drill site shortly after recovery.

Jan 1, 2008

By J. Engesser

A research project was undertaken to determine if coal addition tofluxed-magnetite pre-fired pellets would reduce nitrogen oxide (NOx)emissions during pellet induration. Iron oxidation rate tests, coal oxidation rate tests and calcination rate tests were conducted in a laboratory furnace to determine the amount of coal necessary to provide adequate heat for limestone calcination without producing detrimental effects to magnetite oxidation. Pilot scale pot-grate tests were then performed with and without coal in the pre-fired pellets to verify pellet quality parameters and nitrogen oxide emissions. The off-gas during each pot-grate test was analyzed for NOx, CO2, CO, SOx, and O2. There was approximately a ten percent reduction in NOx emissions with coal addition during the normal pot-grate firing cycle. There was a 75% reduction in NOx emissions during firing cycles that used 25% to 75% excess air during firing rather than the normal 300% excess air.

Jan 1, 2003

By W. D. Freeborn

Slim-hole drilling and completion techniques were first used in the Cynthia area of the Pembina field, Alberta, by the Texaco Exploration Company in the summer of 1957. Prior to that time, eighty-eight wells had been drilled and completed in this area in a conventional manner. Subsequent to the initial four-well evaluation programme, twenty-one additional wells have been drilled using slim-hole techniques. No difficulty was encountered in the drilling and completion of slim-hole wells, or in obtaining production from them. A comparison of drilling and completion economics and practices has been made for slim-hole and conventionally completed wells. Penetration rates for both bit sizes (614 in. and 9 in.) were relatively equal. The shorter life of the smaller bits required the use of 15 per cent more bits per well, but the total trip time to change bits was similar for both hole sizes because of the higher hoisting speeds possible with the lighter drilling strings used in the slim holes and better hole conditions. Completion costs of the slim holes were reduced by 37 per cent as compared to the costs of conventional-type completions. This was made possible through the use of smaller well equipment, the elimination of tubing, and a reduction in rig time for completion operations.

Jan 1, 1958

By S. B. Patton

To fully utilize a ventilation simulator as a planning and production tool, the network database must keep pace with mining progress. By using AutoCAD's attribute-definition function, the branch data and node coordinates can be stored as part of the branch-diagram file, and updated with the drawing. Attributes are drawing entities that contain text which can be extracted in a standard spreadsheet format or as an ASCII text file. The data can be subsequently loaded into a ventilation simulator with plotting capabilities, such as VNETPC. This paper presents the methodology for using AutoCAD's attribute feature in a ventilation simulation.

Jan 1, 1994

By M. Murphy

The multibillion dollar cost of cleaning up thousands of environmentally contaminated sites across the country created by decades of inadequate disposal of hazardous waste has led to a search for "deep-pocket" sources of cleanup funds. The resul1:: is the emergence of a growing body of law that could have a profound impact on commercial financing transactions and other investment activities when present or past owners of contaminated property are involved.

Jan 1, 1988

By Sarah Beutner Mavrogenes

The mineralogy of three slags from a domestic secondary copper refinery were studied by applied mineralogical techniques to determine the: 1) phases present, 2) phase chemistry, 3) phase abundance, 4) associations, 5) crystalline habit, 6) grain size, 7)microtextures, and 8) causes for certain metallurgical problems, such as metal losses to the slags. The slags were produced by skimming the bath prior to melt-down to allow heat from the flame to reach the bath. The first slag is highly viscous and all three slags contain a large amount of copper. The "first slag", which is skimmed prior to treatment of the bath with fluxes, contains metallic copper, cuprite, delafossite, magnetite, Mg-hercynite, common spinel-chromite solid solution, picrochromite-chromite solid solution, common spinel-picrochromite solid soiution, gahnite, cassiterite, silica-rich glass, and corundum. Its abundant solid refractory phases make the slag difficult to skim. The "soda-rich slag", skimmed after the treatment of the bath with sodium carbonate flux, contains cuprite, delafossite, magnetite, cassiterite, Na-Al-silicate, and Na-Al-Ca-silicate. It contains less metallic copper than the first slag and lacks the refractory minerals. The "phosphorus-rich slag", skimmed after treatment of the bath with a copper phosphide flUX, contains metallic copper, cuprite, delafossite, berlinite, cassiterite, silica, apatite, Cu-Fe-rich apatite, copper phosphate, Cu-Fe-phosphate, and a Pb-phosphate. In contrast to the above three copper-rich slags, recent charges have produced a silver-copper-rich slag. The "silver-rich slag", skimmed after the treatment of the bath with a copper phosphor ide-borax flux, contains, cassiterite, delafossite, cuprite, a Na-Al-silicate, magnetite, metallic copper, MgO, common spinel-chromite solid solution, and wollastonite. Silver ranging from 0.05 to 2.02% was found by atomic absorption and inductively coupled plasma spectrometry analyses in the metallic copper phase.

Jan 1, 1989

By Greg Beckstrom

Minnesota is a major mining state. This statement is not a dream or stretch goal but is a fact. As reported in a recent edition of Mining Engineering magazine, Minnesota ranks as the third largest state in terms revenues generated from nonfuels mineral production. The vibrancy of the mining sector in Minnesota can be attributed to several factors. The northeastern corner of the state is home to Minnesota?s iron range, one of North America?s largest deposits of iron ore. Iron ore from Minnesota is a strategic resource that has been [ ] instrumental to the nation?s development ? 90 percent of the iron used to build ships and planes during World War II came from Minnesota. Taconite pellets now produced from openpit mines on the iron range are shipped to steel mills worldwide. The growing appetite for steel in China and India has reignited once moribund mining operations throughout the iron range.

Jan 1, 2012