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By C. Sun

In this study, numerical simulations of yield pillars employing the finite element method with time-dependent Drucker-Prager material model are conducted. The stress control mechanism of yield pillars on weak floor strata is studied. The development of pillar yield zone, the distribution of pillar stress and the development of failure zone in the weak floor strata are investigated. The study indicates that a properly selected yield pillar size may significantly reduce the peak stress induced in the weak floor strata and effectively control the development of failure zone in the floor.

Jan 1, 1999

By P. Rambalee

A multiple coal fired boiler house provides steam for utility usage in various production plants. Maintaining stable header pressure and boiler availability is of critical importance for downstream consumers. Advanced Process Control comprising of a G2 based expert system and Model Predictive Control was implemented to improve the boiler house performance. The results yielded improvements in the main header pressure stability, reduction in boiler saturation and significant saving in coal consumption. All information used for this document is from a published whitepaper written and led by Prevlen Rambalee (Anglo Platinum) and Gustaf Gous (BluESP) titled, ?Control and Stabilization of a Multiple Boiler Plant: An APC Approach?.

Jan 1, 2012

By D. P. Harris

This paper examines recent developments and work in progress on the application of quantitative methods and computers to the appraisal of the mineral resource potential of discrete areas by employing reconnaissance geological information and general economic relationships. The perspective of this paper might be that of a firm planning a regional exploration program or of a legislative body seeking to choose between several alternative actions on the basis of their impact upon the regional resources. In addition to this general survey and commentary, an example is presented of the use of geostatistical analysis and computer simulation to evaluate the economic mineral resources of the Seward Peninsula of Alaska.

Jan 1, 1969

The modern theory of sampling of particulate minerals essentially consists of a recent generalization of the procedures for applying and calibrating the formula usually known as ?Gy?s Formula? for sampling variance control, in which the central concept is a parameter called the liberation factor l. A model which can be experimentally adjusted was proposed by one of the authors several years ago, based on geostatistical considerations. This new model, which relates the liberation factor to the sizes of the fragments and mineral grains, solves the usual difficulties faced in the past, and permits predictions that are well verified in practice. Unfortunately, an older, arbitrary and less general formula is still widely used. The vast majority of today?s misapplications of Sampling Theory of Particulate Materials can be traced back to the use of this antiquated and generally incorrect model. Following a brief history of the models used for the liberation factor and a description of its main variable, the liberation size, and to illustrate the importance of proper modelling of l, this paper presents demonstrative calculations of the absurdity of the incorrect model using the particular case of gold mineralization as an example, followed by some more positive examples of application.

Jan 1, 2002

The Metallurgical Development of an Enargite-Bearing Deposit

Sep 13, 2010

By C. Musingwini

Traditionally, mineral reserves management at most underground mines in Zimbabwe focus on maintaining large mineral reserves so that the time between development and production is as long as possible. Historical data at Shabanie mine, a Zimbabwean sub-level caving underground mining operation, confirms this practice. However, the high cost of underground development means that the luxury of large buffer mineral reserves cannot be justified. Furthermore significant increases in the costs of production, exacerbated by the current unfavourable economic climate, make the wisdom of extending development workings well ahead of use questionable. Poor ground conditions at Shabanie mine, mean that some development ends have to be re-mined two or three times due to partial or complete closure between the time they are mined and the time they are utilized. In order to reduce the inordinately high support costs associated with closure of development ends a new ?just-in-time? (JIT) approach that provides development ends as and when they are needed, has been adopted. Accordingly a model to determine an appropriate ?just-in-time? rate of development has been created. The JIT development model indicated that the mine could reduce development rates from 330 m/month in 2001, to 160 m/month in 2002 and achieve savings of about 50% on annual support costs, but still assure customers of a long-term product supply. The mine accepted the model in November 2001 and began implementing it in 2002. Results of the implementation will be reviewed in 2003.

Jan 1, 2003

By Qingsheng Liu

A new method of recycling aluminum dross for preparation Al-Si-Ti alloy was studied in this paper. This was carried out in two processes. first the aluminum doss was pretreated by leaching and calcining process, the fine purity and phase of the intermediate oxide powder up to electrolysis demands, then, could be obtained when aluminum dross after washing have been leached for 2h at 100? in 20% hydrochloric acid and calcined for 2h at 1200?, which was treated by cryoite-based molten salt electrolysis. Finally, the Al-Si-Ti alloy was successfully obtained through electrochemical co-deposition in the cathode shows a typical as-cast microstructure. This new recycling method can produce high quality alloy and may bring remarkable economic and social benefits.

Jan 1, 2010

By H. Yavuz

Physical modelling is one of the research tools in the understanding of the failure mechanisms and the deformations likely to be experienced by the strata during mining operations. Success of the physical models to predict the strata behaviour depends on satisfaction of the scaling requirements in modelling material used. This paper gives results from a laboratory work carried out into the factors influencing the strength and elastic properties of a physical model material to satisfy the scaling requirements determined from application of dimensional analysis to the pertinent variables affecting the deformation and failure of the underground structures. It was found that the conditions for preparing the material over its composition had a great influence on the final properties. The effect of different water quantities, sand size and mixing time upon the properties of modelling material was studied and water requirement for different proportions of sand/plaster to prepare the material was optimized. Various sand/plaster ratios of compositions were cured at three different levels of oven temperatures. Curing at low temperature produced material within the average modulus ratios ranging from 290 to 432, which are common to most rock types according to Deere?s rock classification, whilst curing at high temperature produced material within the low modulus ratios ranging from 64 to 140 depending on its composition. A combination of low and high temperature curing resulted with an increase in modulus ratio compared to high temperature curing. Curing the material at low temperature compared to other curing temperatures provided a satisfactory range of strength ratio. It has been shown that the relative amount of filler to plaster in the mix controls the frictional properties of the material and results with an increase in strength and modulus ratio of the material provided that suggested preparation and curing conditions were applied. Model material developed by curing at low temperature simulated modulus ranging from 241 to 343 and strength ratios ranging from 11.6 to14.8 of a coal mine rocks, satisfactorily.

Jan 1, 2003

By L. Andrews

Keywords: mineralogy, phase-chemical, chemical-looping combustion, XRD, SEM, EDS, QEMSCAN, PGM, slag, matte, ilmenite Mineralogy, traditionally associated with concentrator studies, is being increasingly applied to problems in pyrometallurgy. Such investigations commonly make use of a number of techniques, and the results are combined for a meaningful interpretation, which can lead to a successful solution. Mineralogical applications are described from pyrometallurgical operations. Examples are given of studies and investigations involving mineralogy in chemical-looping combustion, feed monitoring to platinum-smelting furnaces, and losses to slag in base metal and platinum smelting.

Jan 1, 2011

By A. Koski

A pond rehabilitation and environmental education project were proposed by Cleveland-Cliffs Michigan Operations (CCMO) and approved by the Michigan Department of Environmental Quality (MDEQ) and the United States Environmental Protection Agency (USEPA) as partial fulfillment of conditions for a stream mitigation permit. The goals of the project were the rehabilitation of a pond on a tributary of a local trout stream, enhancement of public access and appreciation, and the initiation of a site-based environmental educational curriculum. Cleveland-Cliffs undertook a suite of actions to rehabilitate a pond created by a previous mining operation in 1912 and make accessible to local schools the aquatic and riparian ecosystems. Cleveland-Cliffs partnered with the local governmental unit and two local school districts. The rehabilitated pond and riparian zone provide an accessible natural area that local residents can use for such activities as hiking, biking, walking, fishing and nature study. Vegetative enhancement includes the planting of native shrubs, wildflowers and showy herbaceous plants in the pond, on the riparian fringe and the surrounding area. An interpretive trail was developed around the pond with signs created by a local master watercolor artist. Local schools built and installed picnic tables, benches and a kiosk. Cleveland-Cliffs created pond lesson plans tied to the Michigan Curriculum Framework, developed inexpensive teaching kits and hosted a workshop for teachers from nine local schools. Classes regularly utilize the pond during the school year conducting environmental studies. Nesting boxes, wildflower gardens, bat houses, frog deformity surveys and water quality studies are a few of the activities that classes have conducted at the pond.

Jan 1, 2007

By Henry Rawdon

THE following note describing the behavior of copper under rather unusual conditions is offered here for its suggestiveness rather than as a complete study of the question. The examinations described were made because of a request for information concerning the embrittlement of copper when heated in a molten salt bath (sodium chloride) for the purpose of cleaning it, as well as for softening it. It is well known that metals may be rendered very brittle by electrolytic action, in aqueous solutions, in all probability by the action of nascent hydrogen, and it was suspected that perhaps the embrittlement of the copper by means of the molten salt was produced in a somewhat similar manner. It was found that the copper was in contact with iron (or steel) while immersed in the molten salt, through the occasional use of an iron stirring rod, iron forceps for handling the pieces, and an iron pot for containing the fused salt. In the electrochemical potential series iron and copper stand some distance apart, copper being electronegative to the iron. Assuming that the two metals bear a similar relation to each other, when immersed in a bath of molten salt, as they do in an aqueous solution, they would be expected to form a galvanic couple, the copper being the cathode. By this means the copper might be embrittled, as often happens in aqueous solutions, by the action of the liberated hydrogen. In this case, however, the embrittlement must be attributed to some other agent than hydrogen. To demonstrate how copper may be embrittled under these conditions, two small rods, one of copper and the other of mild steel, approximately 3/8 in. (9.5 mm.) in diameter, were immersed in a bath of sodium chloride that had been heated somewhat above its fusion point (melting point of sodium chloride is 819° C.) and an electromotive force of approximately 6 volts from a storage battery was impressed upon the system. The copper was made the cathode and the action was continued for

Jan 2, 1920

By Josef K. Alter

Crosshole Sonic Logging (CSL) of drilled shafts requires 1.5-in (38-mm) or 2-in (51-mm) I.D. sonic access tubes to be installed inside the steel reinforcement cage. The sonic access tubes do not contribute to the structural capacity of the drilled shaft. The proposed use of Ischebeck TITAN T73/56 CSL/Hollow Threaded Rebar for Cross Hole Sonic Logging Access Tubes Combined with Longitudinal Concrete Reinforcing in Drilled Shafts (patent pending) is discussed as an alternative method of construction and CSL probe access. The T73/56 hollow threaded rebar/sonic access tube performs as a high strength rebar while at the same time creating a 2.2-in (56-mm) I.D. sonic access tube. The deformed high strength hollow bar provides better adhesion to concrete thus reducing the problem of debonding associated with smooth PVC and steel pipe. A cost comparison using conventional rebar with added sonic access tubes is discussed. The use of T73/56 CSL/Hollow Threaded Rebar as a value engineering alternative can reduce both material and labor costs for drilled shaft construction and can provide an advantage where anchor bolt cages and longitudinal reinforcing create congestion.

Jan 1, 2011

By D Craw, J Pope

The Greenland Group, Westland, can be characterised with respect to environmental issues by the application of a GIS database (DAME), and specific sampling campaigns. Waters draining gold mineralised areas have a distinctive chemistry characterised by neutral pH and arsenic as a trace element. The acid neutralising capacity (ANC) from carbonates usually exceeds the maximum potential acidity (MPA) from sulphides resulting in circum-neutral pH. These waters are readily distinguishable from waters draining coal mine related areas, which commonly have low pH (~4) and low As concentrations (~0.1 ppm). In contrast, dissolved arsenic mobilised from Greenland Group historic gold mining areas is up to 2.4 ppm. This As mobilisation is controlled by the secondary As mineral, scorodite (FeAsO2+2H2O). Maximum dissolved As concentrations increase with increasing pH, corresponding to the increasing solubility of scorodite with increasing pH. Dissolved As is attenuated by dilution, precipitation of scorodite, and/or adsorption to iron oxyhydroxide (HFO). Adsorption to HFO is an important attenuation mechanism in and adjacent to many mine sites. HFO is abundant at mine sites where pyrite was abundant in fresh rock, such as where the mineralised zone is dominated by disseminated pyrite. Pyrite, and resulting HFO, are relatively rare where mineralisation occurred as well-defined quartz veins. Localised HFO occurs also where ankerite oxidises in host rocks. Arsenic output flux (ca. 25 g/day) from historic gold mine sites is commonly less than the natural background flux from mineralised rocks (>5000 g/day).

Jan 1, 2006

The new legislative regime applying to the mining industry has been in force for nearly two years. However the parameters for the permits required under the Crown. Minerals Act 1991 and the resource consents required under the Resource Management Act 1991 are still being established. Mining operators will benefit from participating in the development of policies and plans currently being formulated by local authorities. The Energy Legislation Amendment Bill currently before the House contains amendments to the Crown Minerals Act to clarify points of uncertainty and to reduce transaction costs where possible.

Jan 1, 1993

By Dr. G. R. Hoey

"Abrasive wear and corrosive wear of carbon-steel grinding balls occurred simultaneously during the wet-grinding of hematite iron ore, and Ni-Cu sulphide ore, in laboratory ball mills. Two corrosion control methods, the use of corrosion inhibitors and pH control, were investigated and found to be effective means of reducing or preventing corrosive wear. Up to 50 % reduction of total ball wear resulted from the use of these methods.Corrosive wear is caused principally by the reaction of oxygen in air with the carbon-steel grinding balls, probably by the following reaction: 2Fe + O2 + 2H20 - 2Fe2 + 40H-.IntroductionA survey of corrosion problems in Canadian sulphide ore mines was completed and the findings were published in 197l(l). The corrosion survey was used to develop the present research program with the objective to find more economical and effective ways and means to reduce the corrosion that occurs in the mining and metallurgical industry. The purpose of this presentation is to review the projects being done by staff members of the Corrosion Section, Extraction Metallurgy Division, on corrosive wear and its control in wet-grind ball mills.Both abrasion and corrosion contribute to metal consumption during wet grinding of ores. The total wear of grinding media in this study is assumed to be equal to the sum of corrosive wear and abrasive wear. A great deal of research and development has been reported in the literature on ways to improve the abrasion resistance of grinding media but only a small number of studies has been reported on the corrosion resistance of conventional grinding media."

Jan 1, 1974

By Eleanor Sonley

In October 2000, temporary seismographic stations were installed above the Trail Mountain Mine, Emery County, Utah, USA to supplement a regional network. Over seven months, 1826 mining-induced seismic events were recorded with a magnitude range of M 0 to M 2.2 (Arabasz et al., 2002, 2005). Routine event locations for this dataset cluster around the longwall mining activity during the recording interval. However, applying a double difference relocation technique to the routine locations significantly improves the correlation between mining activity and event location. The resulting relocations depend greatly on station distribution and the number of arrival time picks. We use this dense temporary array to assess station distribution requirements for applying the double difference technique at other mines by systematically removing data from available stations, thus simulating sparser networks. The insight gained using the Trail Mountain dataset is used to develop a metric for assessing the usefulness of above-mine networks and to develop a tool for expanding seismic network coverage. To verify the appropriateness of these tools for wider application, we examine data from two additional mines located in the western United States. Improving the relative locations of mining-induced seismic events highlights the association of these events with active portions of the mine. Clusters, regions of quiescence and relative timing of events can be used by mine operators to assess hazard, optimize production, and evaluate performance of mine plans. The lessons learned from this study may be used in future network design to improve accuracy of event locations at other mines.

Jan 1, 2009

By Taehong Kim

An accurate and reliable prediction of Tunnel Boring Machine (TBM) performances, in terms of Rate of Penetration (ROP), utilization (U), and cutter wear rate, is a critical element in the successful planning and execution of mechanical tunneling project. Three open hard rock TBM projects were studied to establish possible trends and correlations between rock mass properties and machine performance. Based on this analysis and literature survey, three geological parameters, including RQD, RMR, and groundwater inflow rate, were identified as having the greatest impact on TBM utilization level. Rate of Penetration (ROP) and cutter wear rate were also correlated with fracture spacing, alpha angle, and Cerchar Abrasivity Index (CAI).

Jan 1, 2008

By Abouzar Vakili

Longwall Top Coal Caving (LTCC), as the most attractive method for thick coal seams, has been suffering from insufficient geomechanical understanding for the past few years. Cavability without doubt is the most critical geomechanical issue associated with the top coal caving method. A discontinuum method has been used for comprehensive modeling of LTCC operation by using the Universal Distinct Element Code (UDEC). In addition Particle Flow Code (PFC) and Phase2 were used as support for the caving mechanics analysis. Although the previous researches of gravity flow in caving operations neglected the effect of continuous span expansion, it has been observed in this study that face advancement has a great impact on roof symmetrical behavior. The amount of symmetry fluctuates between different face distances. Horizontal displacement seems to be the best indication for roof symmetrical evaluations. Two critical caving conditions have been modeled and parameters such as horizontal displacement, caving angle and recovery rate have been compared thoroughly. Results show that unsymmetrical behavior on the roof is closely related to face stability.

Jan 1, 2007

By A. E. Lewis

The emphasis of this paper is on the characterization and testing of the slag produced by a secondary lead refinery. This work forms part of a broader investigation aimed at reducing loss of valuable product from the process as well as minimizing the environmental impact of the process wastes. It was this work that led to a critical examination of the standard waste classification tests. Characterization of the slag was carried out using a number of complementary techniques. In the broader context, the slag characterization aided in identifying process deficiencies and thus was a critical tool in suggesting potential for process optimization. For this study, the slag characterization provided a relatively comprehensive picture of the composition and properties of the slag, which facilitated understanding the behaviour of the slag under batch test conditions. On the basis of quantity of hazardous components alone, the slag is hazardous according to South African Acceptable Risk Limits (ARL). However, when both the quantity and the leach potential of the hazardous components is taken into account, standard waste tests carried out by three independent agencies indicate that the slag should not be classified as hazardous according to local regulations. Also, according to United States Environmental Protection Agency (US EPA) limits, which are independent of the quantity of the waste, the slag would not be classified as hazardous. The standard waste tests used by the independent agencies was the Toxicity Characteristic Leach Procedure (TCLP), a test which was developed by the US EPA to classify hazardous wastes. One of the requirements of this batch test is that it should be quick, simple to carry out and that the results should be reproducible. Previously, the applicability of the TCLP test to mineral processing and metallurgical wastes has been challenged on a number of points. Additional testing of the slag was carried out using both the TCLP and the Synthetic Precipitation Leach Procedure (SPLP) recommended by the American National Mining Association as being more appropriate for mineral processing wastes. The particular physical and chemical characteristics of the secondary lead slag highlighted additional limitations of both the TCLP and SPLP tests as standard laboratory batch procedures. Keywords: environmental protection, secondary lead processing, slag, leach testing, TCLP, SPLP, ARL, hazardous waste, batch tests

Jan 1, 2000

The results of a series of physical model studies of the stability of jointed rock slopes carried out some years ago are described. These models were tested under centrifugal loading. Four ?geological? structures were tested; all had the same joint orientations and strengths, but the relative spacing of the joints was different. The results showed that the mechanisms of failure of the slopes varied for the different models, and the gravitational loads at which failure developed also varied. The following conclusions are drawn from the results of the physical model tests: ?the mechanism of slope failure is by progressive deformations throughout the slope ?the ratio of the spacings between the different sets of discontinuities exerts considerable influence on the slope failure ?in the models tested, the intact material strength had no noticeable influence on the stability of the jointed rock slopes(note that for hard rock, similitude conditions indicate a prototype slope height of 300 to 400 m, and therefore intact rock failure might not be expected under simple gravity conditions, i.e. no tectonic stresses) ?rock slope failures are three-dimensional and in general are not amenable to two-dimensional simplification ?knowledge of the orientations of discontinuities in the slopes does not allow prediction of a unique failure surface, nor of a volume of failure. The volume of failure is determined to a large extent by the plan configuration of the slope.

Jan 1, 2006