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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

By M. Ashraf Mahtab

A feature of interest in stability of excavations in domal salt is the phenomenon of gas outbursts which has occurred in five of the six mines in Louisiana salt domes. Gas outbursts are sudden erruptions of salt and gas from the face or roof of a mine opening. They are associated with anomalous zones in salt, depth of mining, and the method of excavation. Potential risks from gas outbursts include an unplanned connection to a reservoir of water or hydrocarbons and, possibly, a loss of the mine. It is proposed that a gas outburst is initiated by disking in biaxial compression and propagates by spalling of the cavity walls and further disking. The outburst is terminated by a combination of dilatancy hardening, increase in stress along the cavity axis, and enlargement of the cavity to the boundaries of the pressure pocket. Identification of burst- prone areas will require research into in situ measurement of material characteristics and further under- standing of the mechanism of gas outbursts. Shock blasting in advance of mining appears to be a promising technique for controlling gas outbursts.

Jan 1, 1981

By G Gosson

An important requirement in every geological quality control program is that the identity and grades of the control samples (duplicates, certified reference materials (CRMs), and blanks) must remain æblindÆ to the analytical laboratory. Once the entity to be controlled is aware of relevant details of the control process, such as the identity of the control samples, the objectivity may be lost and the control may no longer be completely valid. Whereas the blind insertion of field duplicates and coarse blanks can be easily conducted at site, simultaneously with the sampling process, the rest of the control samples should be inserted into the batches during or after sample preparation and prior to assaying, in order to ensure a proper assessment of precision, accuracy and assay contamination, independent of the internal quality control of the laboratory. Such a procedure raises the concern that blind insertion of crushed or pulverised material in sample batches prior to assaying could represent a breach in the chain of custody principle, as samples would have to be temporarily returned to the custody of a non-laboratory person in charge of the insertions. In this seemingly conflict scenario, what should we give up? Do we maintain the strict chain of custody, knowing that the laboratory will be aware of the identity of some of the control samples, or that some duplicates will not be true same-batch duplicates? Do we ignore chain of custody issues to maintain the anonymity of the control samples and insert blind same-batch duplicates, CRMs and blanks? Is it possible to do blind insertions without breaching the chain of custody? Current NI 43-101 and JORC requirements, as well as real-world QA/QC and sample security practices, are discussed in light of AMECÆs approach to the solution of this apparent dilemma.

Jan 1, 2008

By J. M. Rios

This paper exposes the reasons that led the Empresa Nacional Minera del Sahara, S.A. (ENMINSA) to the selection of a conveyor belt system for the transport of phosphate rock over a distance of 100 kilometers. ENMINSA was created in 1962, with the main objetive of the exploitation of phosphate rock deposits in the Spanish province of Sahara, in North West Africa. Poor grade outcrops were known previously. A detailed geological research carried over the province led ENMINSA to the discovery of deposits not exposed, and of much higher grade. The sector known as Bu-Craa was chosen as the most promising, and was explored by means of drill holing and shafting. The important amount of information obtained permitted a detailed evaluation of the capacity and grade of the rich ore contained in the Bu-Craa area. Simultaneously with the systematic reconnaissance of the Bu-Craa deposits, ENMINSA developped the study of the technical and economical problems required for the beneficiation of the rock, which comprised five main groups of projects: rock exploitation; beneficiation plant; rock transport from the mine site to the Atlantic coast; storage, handling and loading facilities by the sea- side, and power plant. Once determined the location of the marine loading facilities, which to date are in an advanced stage of construction (figs. 1 and 2), the studies conductive to the selection of the best transport system from the mine to the ocean, along 100 kms. distance were undertaken.

Jan 1, 1968

By D. Berkley

"The competitive pressure, the increasing energy costs and the environmental regulations impose substantial challenges to the definition of power plants serving industrial facilities. Primary mining and metallurgical facilities have even greater challenges because they are often located remotely, where the fuel supply can be a problem. The absence of a power grid imposes challenges on the reliability and quality of the electrical energy supply. In addition, the facilities usually require thermal energy too, not only electricity.This paper outlines these types of issues that have to be considered when defining a cogeneration plant integrated with a remotely located industrial facility. It is addressed to the “users” of cogeneration facilities rather than to “generators.” The focus is on analyzing various site-specific design considerations to prescreen the feasible cogeneration alternatives and minimize the number of options to be analyzed from the economics viewpoint. This approach could substantially reduce the engineering effort and schedule during the feasibility phase of the project.The front-end of the paper provides a basic understanding of cogeneration plants of various types to establish a common language. Subsequently, the paper outlines and analyzes specific issues that could be of help in the definition of cogeneration installations for remotely located industrial facilities, with a focus on mining and primary metallurgical plants"

Jan 1, 2003

By D. Berkley

The competitive pressure, the increasing energy costs and the environmental regulations impose substantial challenges to the definition of power plants serving industrial facilities. Primary mining and metallurgical facilities have even greater challenges because they are often located remotely, where the fuel supply can be a problem. The absence of a power grid imposes challenges on the reliability and quality of the electrical energy supply. In addition, the facilities usually require thermal energy too, not only electricity. This paper outlines these types of issues that have to be considered when defining a cogeneration plant integrated with a remote located industrial facility. It is addressed to the ?users? of cogeneration facilities rather than to ?generators.? The focus is on analyzing various site-specific design considerations to pre-screen the feasible cogeneration alternatives and minimize the number of options to be analyzed from the economics viewpoint. This approach could substantially reduce the engineering effort and schedule during the feasibility phase of the project. Part 1 of this paper (Berkley, 2003) provides a basic understanding of cogeneration plants of various types to establish a common language. Part 2 outlines and analyzes specific issues that could be of help in the definition of cogeneration installations for remotely located industrial facilities, with a focus on mining and primary metallurgical plants.

Mar 1, 2003

By Dolea Gabriel Gheorghe

In the present paperwork is proposed an economical-mathematical model (fuzzy) that aims optimize the technological variants of the mechanized coal face. By fuzzification, the issues to solve become more flexible and allow the decision maker to acquire more variants for the functions objectively established. The description of technological solutions is carried out by a set of controllable variables of "category" type by which the type of the machinery is defined within the frame of the actual geological & mining conditions. In the paperwork are used concepts of "successions graph" and "matrix of compatibilities"; with their help a methodology to choose between different technological variants of coalfaces is proposed. It treats the problem of developing the functions that express the membership degree in vague concept. In the end it is presented an assessment procedure for the technological variants of mechanized coal face.

Oct 1, 2009

The US Constitution provides for regulation by the states for protecting the public's safety, health, and welfare. Hence, in the eyes of the law of all states today, this is the sole justification for registration of professional engineers. Wyoming was the first state to register professional engineers in 1907, to correct abuses of incompetent or fraudulent practices in surveying and real estate. Public safety and health are most directly affected by civil, electrical, and mechanical engineering. Other branches of engineering have a profound effect on the public welfare, including investors, and safety and health of employees. No arguments, pro or con, are valid except in relation to the registration laws of various states. Code of Ethics Few would argue the desirability of requiring conformance with a code of ethics. A major problem lies in enforcing compliance, since protecting the public demands a high standard of competence, yet assessing competence gets confused with restraint of trade. Bidding engineering work on price competition can lead to pressure to cut corners on engineering quality, and was therefore discouraged by codes of ethics. The Supreme Court, in a suit against the National Society of Professional Engineers (NSPE), barred any engineering society from such bidding restriction. It has, however, upheld the right of states to impose codes of acceptable practice as part of registration laws. For example, Texas Canon I reads, "The engineer's paramount professional responsibility should be the safety, health, and welfare of the general public." Anything less makes the code practically meaningless, but there are potential conflicts of interest in many engineering organizations. How can conflicts be handled? Any corporation could improve its public image by adopting a policy that each employed PE should, without fear of recrimination, record in writing over his seal any problem or flaw in any design that comes to his attention. The policy should further require that his superior provide him a written reply pointing out that the "flaw" is accepted as requiring correction or as a calculated risk, or overruled as erroneous or as a difference of opinion. Errors in calculation of judgment are inevitable. Despite this, there are limits to how much time and money should be spent to eliminate them. It is difficult, however, to see any excuse for failure to conscientiously evaluate the opinion of a PE. This may be an impossible ideal, but how else can the profession or the industry have credibility? The National Council of Engineering Examiners (NCEE) has a code of ethics one presumably subscribes to by signing an application to write a Principles and Practices examination. However, NCEE has none of the power of enforcement that is available through state boards of registration. Registration Qualifications Qualifications are set by the laws of the states. In general, they require passage of an eight-hour examination in fundamentals, preferably at graduation, and, later, one in principles and practices. The examinations are compiled and distributed by NCEE. This system provides for a high degree of uniformity and reciprocity. States set the education and experience levels (typically four years after graduation) required by those desiring to write the principles and practices examination. Examinations The principles and practices examination calls for answering eight of 20 equal weight questions; one on engineering economics, 19 on engineering. Economics may enter into engineering questions, but only provided the question is not answerable by an economist without engineering training. In preparing examinations, NCEE strives to use questions that require some judgment and can be more effectively answered by someone with four years experience beyond college. The aim is to assess entry-level professional

Jan 2, 1984

By Paulo von Krüger

O desempenho dos eletrodos nos fornos elétricos a arco, depende, essencialmente, de três grupos de fatores distintos. O primeiro é a sua qualidade intrínseca, expressa em termos de resistividade, densidade, porosidade etc., cujos valores são dependentes dos materiais e procedimentos empregados na sua fabricação. O segundo se refere aos parâmetros/procedimentos operacionais do forno elétrico, que são função do produto, da carga, dos recursos do forno, dos resultados objetivados etc. O terceiro é relacionado aos procedimentos praticados no manuseio, montagem, armazenagem etc., dos eletrodos, desde a sua recepção na planta, até seu consumo. Este trabalho se propõe a revisar e comentar alguns dos aspectos relevantes de cada um daqueles fatores, com ênfase no terceiro, assim como identificar o modo como cada ação influi no desempenho dos eletrodos.

Aug 16, 2017

By J. E. Gebhardt

Progress is reported on capturing the effects of gangue chemistry in the context of a comprehensive stockpile heap leach model for leaching copper sulfide ores, employing leading edge computational fluid dynamics (CFD) technology. The stockpile is a complex multi-phase process, comprising of a solid porous media, with complex fluid flow, gas and liquid phases, competing solid-liquid reactions, dissolution of minerals and transport through the heap. The model accounts for many of the challenging physical and chemical features of the heap, including transport and reactions kinetics for the important copper and iron sulfide minerals, ferrous oxidation, bacterial effects, thermal energy, acid and sulfate balances. In this contribution, the model has been extended to incorporate dissolution of various species from gangue reactions and precipitation of hydronium and potassium jarosite, ferric hydroxide, alunite, and gypsum. The effect of aeration on the simulation of a copper sulfide heap leach is provided as an example.

Sep 1, 2012

By L Maw

New ZealandÆs largest gold producersÆ OceanaGold Macraes Mine is characterised by a large tonnage and relatively low grade operation. To survive in diminishing real gold prices, the operation must focus on a culture of continuous improvement. This paper presents the outcome of a supplier sponsored continuous improvement project known as the Orica Advanced Mining Services project.   In March 2004 OceanaGold (then GRD Macraes) entered into an Advanced Mining Services (AMS) project with Orica Mining Services. The motivating factor behind OceanaGoldÆs need to improve bulk waste productivity and SAG mill throughput was the planned increase in production from five million to 5.4 million tonnes per annum. A stripping ratio of ten to one meant that optimisation of the drill, blast and production functions was paramount.   The primary focus of the project was to optimise the drill and blast parameters to suit the variable rock conditions throughout the mines main operating pit (Frasers Pit). Fragmentation of the ore for presentation at the SAG mill, and cost reduction on the mining of bulk waste movement, were the primary objectives. A number of additional initiatives complimenting the interface between drill, blast and ore production were also established. These included; +        reduced ore loss through delineation of ore boundaries to allow for blast movement; +        established blasting parameters for variable geological conditions, resulting in improved fragmentation; and +        improved asset utilisation by establishing a blasting regime that angled grade control holes to be used as blastholes in the stockworks area.   A year into the project, the philosophy of continuous improvement is now in-grained at the Macraes minesite. As the project continues, the focus is on the further refining of those procedures established, to ensure a continued focus on lower unit mining production costs.

Jan 1, 2005

By R. Peroni, J. Kopp

Mine planning and scheduling is based on using a geological model for the deposit. Blocks are used to discretize the deposit into mineable volumes where grade values are assigned. Traditional estimation techniques such as kriging or inverse distance weighting are frequently used for this task where an interpolated value is calculated within a discrete volume. This group of block grades is the input for sequence optimizers, which base their decision on the economical value of a given block. Ultimately, the economical value of a block depends on its grade, making mine sequencing sensitive to all estimated values. If one looks to a block not as a single grade but as a set of equally possible grades, its economical value will change as different grades can be assigned to it. Stochastic simulation is known to provide the tools to assess grade variability, which makes it possible to generate equally probable values in a block. Different grade block models can thus be built and multiple sequencing alternatives are observed by running the optimizer for these distinct inputs. The results demonstrate that the methodology is adequate for risk assessment and proves to be useful for mining project sensitivity analyses. Differences in the project net present value showed that there is little difference between the two simulation methodologies (sequential Gaussian simulation and sequential indicator simulation) applied. The process is demonstrated using a Brazilian kaolin deposit. Keywords: geostatistical simulation, mine planning, sequencing, risk assessment, open pit optimization.

Jan 1, 2003

By J .. F. Brownrigg

In the mining method used at O'Okiep Copper Company (OCC), vertical crater retreat, the prime requirement for the fill is that it should be sufficiently strong to be free-standing to a height of 150 m. Other requirements are minimal decant and drainage water, and high pulp density to allow large tonnages to be placed quickly and alleviate transport problems. The excessively high cost of cement precluded the use of a cement-based fill, and after three years of extensive investigations a backfill based on the smelter slag was produced. Currently a fill with a uniaxial compressive strength of greater than 1 000 kPa after one month is being produced. This is in excess of the design specification of 850 kPa after 2 - 3 months. The research and development which went into the slagfill is briefly covered; the production of the fill from the various raw materials is described; and the design and control systems of the backfill plant, the reticulation system and its monitoring are examined. Finally, the implications of this high- quality fill for the mining programme are assessed.

Jan 1, 1988

By Theo. Koulomzine

"The property of Consolidated Central Cadillac Mines, Limited, consists of 1,103 acres formerly held by Central Cadillac Mines, Limited, and Wood Cadillac Mines, Limited. Both mines have been partly developed to depths of 565 and 1,000 feet respectively, and from 1939 to 1943 they produced gold, with small amounts of silver and tungsten, having a total value of $2,208,528 from 377,489 tons of ore. The average grade of the ore was $5.85 a ton . Less than 10 per cent of the ore hoisted was discarded by sorting. New development work, carried out since the former Wood property has been purchased by Central Cadillac, has shown that the tonnage indicated by mine workings and diamond drilling exceeds 2,000 tons per vertical foot.The property lies between the claims of Kewagama Gold Mines, Limited, and Pandora Cadillac Gold Mines, Limited, and straddles the Cadillac 'break' for a length of nearly 1 ½ miles. The main workings are 1 3/4 miles east of the well-known O'Brien gold mine.GEOLOGYOutcrops are very scarce, with none at all of the most important horizons, so that the general geology shown in Fig. 1 is deduced mostly from underground workings and diamond drilling. Fig. 2 is a vertical cross-section and Fig. 3 a longitudinal section through the ore zone.The ore lies within a belt of Blake River volcanics which is approximately 600 feet wide and is flanked on the north and south, respectively, by Cadillac and Kewagama sediments. All the formations have a nearly vertical attitude. The Blake River belt consists essentially of well sheared volcanic tulfs, but associated with these in the northern part are a number of bands of iron formation and the central part, to a width of 100 feet, is occupied by talc schists, making the Cadillac fault proper. Intruding the volcanics south of the Cadillac shear zone are dykes of two types- finegrained aplite or quartz albitite, and porphyry; both consist essentially of albite and quartz and are distinguishable only by the grain size. They have the general east-west trend of the formations they intrude."

Jan 1, 1954

By Parviz N. Farsangi, Ferri P. Hassani, Allen G. Hayward

"Kidd Creek Mines places approximately 10 000 tonnes of consolidated rockfill (CRF) daily. Consolidated rockfill comprises sized aggregate mixed with different ratios and amounts of binders. Consolidated rockfill is employed to simplify subsequent pillar recovery and provide improved passive/active ground support.The consolidated rockfill is designed to sustain not only the gravitational loading of the overlaying fill material, but also to some extent the dynamic loading applied during blasting of the adjacent stopes and/or pillars. This paper describes the steps taken to optimize the pre-sent fill system at Kidd Creek Mines.The emphasis is on four areas which have high saving potential: lower cost alternative binders, structural design, quality control measures, in-situ testing techniques for back analysis. A consolidated rockfill design optimization chart was developed from these investigations."

Jan 1, 1996

By Jong-Jip Kim, J. G. Byrne, W. Kim, In-Ok Shim, John E. Flinn

"Two rapid solidification processes for 304 stainless steel were studied: centrifugal atomization (CA) in a helium atmosphere and atomization by exposing argon-containing melt to vacuum (VGA). Positron annihilation and x-ray line broadening measurements of explosively consolidated monoliths were used to clarify microhardness measurements as a function of annealing temperature. Interesting differences in positron response between CA and VGA materials are ascribed to more carbide formation in the CA material than in the VGA material in the 600 0C range. In addition, hot isostatic pressing of the CA material was examined as to the relations between mechanical behavior, pore shape, and relative density. A variable stress concentration factor is introduced into the theory to allow for changing pore shape as relative density increases.IntroductionThere are many potential advantages of rapid solidification processing (RSP), such as a high degree of matrix supersaturation, finely dispersed microstructures, improved chemical homogeneity, and retention of metastable phases, which have been studied extensively. To consolidate rapidly solidified material which is in powder form into useful shapes often requires subjecting the material to elevated temperature for extended periods of time under mechanical forces, as in hot isostatic pressing or hot extrusion. In such cases, some of the characteristics of the rapid-cooling step can be strongly affected. An alternative is dynamic consolidation (1), for example by explosive forming, where the time frame at least is extremely short.In the present work, effects of the consolidation processes of hot isostatic pressing (HIP) and explosive forming in a die are examined. The particular material is 304 stainless steel. The characteristics of both RS and VGA 304 stainless-steel powders were described by Wright, Flinn, and Korth (2) earlier."

Jan 1, 1988

By D J. Williams, S Islam

Worldwide production of black coal amounts to about 8 billion tonnes. Perhaps 20% of this annual production is washed to improve its quality, generating perhaps 250 million tonnes of coal tailings annually, generally in the form of a slurry. The coal tailings slurry is typically thickened to about 25% solids by mass prior to disposal to a tailings storage facility (TSF), and hence comprise mostly water (about 85% by volume), plus sand, silt and clay-sized mineral particles and carbonaceous material. While the tailings settle and consolidate on deposition in the storage facility, their high moisture content makes them prone to run-out should the tailings dam fail, and makes rehabilitation of the tailings difficult. Hence, it is important to understand the consolidation and shear strength of coal tailings. Laboratory consolidation testing of coal tailings from a slurry to a soil-like state has been carried out in a purpose-built, large-scale, slurry consolidometer, instrumented with load cells and pore water pressure (PWP) transducers. Laboratory vane shear testing of coal tailings produced at different gravimetric moisture contents has also been carried out. The test results have allowed a regression model to be developed relating the peak vane shear strength of the coal tailings to their gravimetric moisture content.CITATION:Islam, S and Williams, D J, 2018. Consolidation and shear strength of coal tailings slurries, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 62–71 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By L Bergin, D J. Williams, S Islam, T A. Vangsness

The flooding of open strip coal mines in the Bowen Basin and Hunter Valley Coalfields of Eastern Australia has the potential to soften the spoil and floor materials to produce “mud”. This mud can act as a slip plane or weak zone when spoil is dumped into it, resulting in geotechnical instabilities. Once mud has formed, typical handling techniques include its costly removal by mechanical means, or its isolation and capping.There are little data available on the moisture state and shear strength of the capped mud. To investigate the effectiveness of isolation and capping, research has been conducted using a large slurry consolidometer (150 mm in diameter by up to 410 mm in height) to simulate capping in situ. Once consolidated, the mud was subjected to shear strength testing in a direct shear box measuring 60 mm by 60 mm by about 20 mm high. The shear strength of the consolidated mud was compared to that of competent, fresh spoil, a mixture of spoil and mud, and to completely degraded spoil (mud alone).These results have been used as inputs in stability calculations using the commercial computer program Slide 7.0, which demonstrates the strong influence of consolidation of the mud on overall low wall slope stability. The results provide insight into the design and construction of capping to isolate in-pit mud.CITATION:Vangsness, T A, Williams, D J, Islam, S, Smith, A and Bergin, L, 2018. Consolidation and shear strength testing and stability analysis of coal mine spoil degraded to mud, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 97–109 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By F. E. Bedale

STUDY of several severe mine explosions that occurred during the winter of 1907 led to the belief that coal dust was a definite explosion hazard. The Consolidation Coal Co. was a pioneer in the early work to' eliminate this hazard and to combat the dangers incident to poor ventilation and the presence of methane. Maintenance of high humidity throughout the mines was one of the first measures adopted, later to be superseded by rock-dusting. In the twenty years from 1907 on, many safety measures were developed and adopted, and several prizes were won, though the practice was crude by present-day standards. But in 1927, the company went to work in earnest, and organized a Department of Safety with adequate personnel and with authority to enforce all approved rules for the prevention of accidents and the preservation of company property. All plans for new construction work, changes in mining systems, and proposals for the purchase of new mining equipment had to receive the approval of this Department. A set of operating- and safety standards was written to govern the activities of all employees, and physical examinations for them were required.

Jan 1, 1938

An experimental study of the soil mechanics of brown coal showed that brown coal consolidates in the same manner as does a clay and that the theory of consolidation for soils may be applied to brown coals. Moisture content is a function of the coal type, the existing effective stress, and the stress history of the coal.The effective stress in a brown coal seam is a function of the overburden pressure, the pore stress and tectonic stresses. Stress history may be deduced from geological evidence and determined by consolidation tests. Application of these principles to the brown coal seams of the Latrobe Valley shows that the distributions of natural moisture contents are consistent with consolidation.INTRODUCTIONThe nature and geology of the brown coals of Victoria, particularly of the Latrobe Valley, were discussed in some detail by Edwards (1945, 1948), Thomas and Baragwanath (1949) and Gloe (1960). A salient feature of these studies was the distribution of moisture contents in the brown coal seams. Recent experimental work, part of a soil mechanics study of the structure and strength of brown coal, showed that moisture content variation is a reflection of consolidation phenomena in brown coal and application of the results to .field condItions verified and modified the conclusions of Edwards in his pioneer work. Further detail of this experimental work is recorded elsewhere (Rosengren, 1961).EFFECTIVE STRESS AND CONSOLIDATIONEffective stresses in soilsA saturated soil is a two-phase system, consisting of a compressible skeleton of rigid soil particles and pores filled with water, an incompressible fluid. (In this context, the terms compressible, incompressible, and rigid are relative only and refer to orders of magnitude). If this system is subjected to stress we define...

Jan 1, 1963