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By H. L. Zimba

Flotation involves the selective levitation of mineral and its transfer from cell to launder. The flotation rate is the rate of this transfer. It may be defined by the slope of a recovery-time curve for any cell in a bank or at any time in a batch operation. The objective in flotation rate study is an equation expressing the rate in terms of some measurable property of the pulp. This can be either the concentration of floatable mineral in weight per unit volume or a relative concentration, which will be a function of the recovery. A rate equation for an actual flotation pulp will contain at least two constants, both to be determined from the collected data. The data used in this paper were collected from bench-scale flotation tests on Konkola primary mill cyclone overflow at various pulp densities and pre-flotation thickener underflow at a pulp density of 35% solids by weight.

Jan 1, 2009

By J. A. L. Napier

Computer programs which rely on the assumption of linear, elastic rockmass behaviour have been used routinely for many years in the South African mining industry to determine the stresses arising in the vicinity of mining excavations. A description is given of the theoretical background and novel solution techniques used in the recently developed MINSIM-D boundary element program. Features of the program include the ability to analyse multiple interacting reef planes at arbitrary orientation to one another, slippage on fault planes and the effects of backfill placement in mined areas. Incremental mining sequences can be modelled, and digitizer and front-end routines have been written to assist in the capture of mining outlines and general problem specifications. A brief indication is given of design problems for which MINSIM-D is appropriate, as well as some future extensions of the system.

Jan 1, 1987

By A. C. Wingrove

The paper outlines the selection of a dewatered tailings backfill system for the Johannesburg Consolidated Investment Gold Division, and covers the following aspects: (i) 16 Shaft pilot testwork; (ii) engineering design problems relating to the Cooke 3 Shaft backfill operation; (iii) in-line mixing - applications with respect to the Randfontein Estates Gold Mine and Western Areas Gold Mine backfill operations; and (iv) pipeline friction losses.

Jan 1, 1988

By J. A. Maritz

Since the dawn of mining, pillars have been used as primary support to ensure stable workings. Early designs were based on trial and error, after which more scientific means developed over time. A vast amount of progress has been made, especially in soft-rock room-and-pillar design methodologies, from which hard-rock design theories developed with minor changes to constant parameter values. The commonly used Hedley and Grant method for hard rock and Salamon and Munro methodology for soft rock draw on the tributary area associated with the pillar, the width-toheight ratio of the pillar, and a back-analysed strength reduction factor. In these methods, only the vertical stress, or stress normal to the pillar influences the load applied to the pillar. This investigation considers the possible influence of shear stresses on pillars in a room-and-pillar layout in single reef planes and multi-reef environments, based on elastic numerical modelling methods. The possible shear stress poses a safety and financial risk to the design process, whereby an undersized pillar would lead to unstable working conditions, whereas oversized pillars could lead to an under-utilized ore resource.

Jan 1, 2014

By M. F. G. Bruce

Two backfill systems have been developed on West Driefontein, namely the centrifuge dewatered tailings system and the cyclone-classified tailings system. Modifications to the two systems since the publication of the original paper (Close and Klokow, 1985) are discussed in addition to the results obtained. Considerable experience has been gained from the operation of the centrifuge dewatering units as well as the placement of dewatered tailings in a difficult mine environment. The centrifuge dewatered tailings method has proved successful in the extraction of a highly stressed block of ground at No. 5A Sub-vertical Shaft. The utilization of backfill support in this area made it possible to dispose of a high-grade barrier pillar. This pillar was considered necessary prior to the introduction of backfill support. The recovery of the gold from this pillar made the use of dewatered tailings backfill cost- effective, despite high labour and maintenance costs. Current experience with the bagfilling method of placing cyclone- classified tailings indicates that it is viable and requires considerably less capital investment. Although expensive at present, it is envisaged that costs will decrease once cheaper bags and other forms of stope support are used. The placement of backfill in small-diameter sausage-type bags requires no change in mining cycle and allows the backfill to be placed close to the stope face. Both backfill systems are being expanded but preference is to be given to the cyclone-classified tailings system.

Jan 1, 1988

By Steve Konieczki

[ ] Great Basin Gold Ltd. (GBG) owns the Hollister Mine and operates it through the wholly owned subsidiary Rodeo Creek Gold, Inc. The property is located in northern Nevada on the Carlin Trend gold belt within the historic Ivanhoe Mining District. The mine is located on the western edge of the Northern Nevada Rift, a major north-northwest trending structural zone that has localized middle Miocene volcanic rocks and numerous epithermal gold deposits. The precious metal deposits are low-sulfidation epithermal systems characterized by banded quartz veins with electrum and silver selenides. The Hollister Mine will employ the selective underground mining method of cut and fill. This will be combined with split shooting (resuing mining method) to optimize recovery and reduce dilution. The focus of mining will be on extraction of ?ounces? from the narrow-veins rather than trying to maximize tons. The initial drifts will be excavated along the strike of the vein and then capped with a substantial concrete sill pillar. Back stoping with hand held drills will be used to selectively mine the vein. The stopes will be backfilled with waste rock material. With every lift, an 18 inch concrete cap will be poured onto the backfill waste rock to prevent gold values from being lost into the fill. Targeted ore production rate will be over 400 tons per day. With current ore reserves, project life is estimated to be around eight years; however, Hollister geologists view the site as one of the most prospective systems for bonanza vein deposits in Nevada. Approximately $14

Jan 1, 2008

By Y. -L. Chiang

Paper written on project work carried out in partial fulfilment of BSc (Eng) (Chemical) The generation and control of manganese sulphide particle size distribution using various mixing configurations were investigated. Specifically, this paper discusses how varying mixing intensities on a macro and micro scale affect the resultant manganese sulphide particle size distribution (PSD) at a constant concentration. The mixing variations were achieved using various Y- and T-mixers as premixing devices into a jacketed, agitated vessel. The reagents used to generate the seeds were aqueous manganese sulphate and sodium sulphide solutions. The results showed that the absence of micromixing resulted in very poor control of the particle size distribution, the particle size and the number of particles produced. This was due to the fact that the macromixing time is much greater than the corresponding precipitation time, resulting in different mixing regions existing within the reactor. From the micromixing experiments, the T?mixer was found to be the most effective mixing device at lower concentrations due to the T-mixer providing a faster mixing time than the other mixing configurations, thereby effectively localizing the supersaturation and hence controlling the precipitation. The results obtained from the direct addition without the extension pipe (i.e. short mixing time) indicated a general increase in mean particle size and decrease in total particle number at reagent concentration of 0.007 mol.dm-3as compared to the corresponding micromixing experiments. The phenomenon may be due to incomplete crystallization at the immediate exit of the mixing device. Further experiments need to be conducted before any conclusions can be drawn about the precipitation mechanisms.

Jan 1, 2007

By P. R. Mothemela

The objective of the investigation is to optimize the truck and shovel operations for pre-stripping at New Vaal Colliery by introducing campaign mining. The aim of campaign mining is to improve the efficiency of the loading, hauling, dumping, and maintenance operations which are critical to the success of truck and shovel operations. The current loading (single-sided loading method), hauling, and dumping operations at New Vaal Colliery were found to be inefficient. Time studies were used as a major indicator to highlight the inefficiency of the truck and shovel operations, and it is recommended that an improved loading configuration, hauling, and dumping operations be implemented by using campaign mining. It is also recommended that a service truck be used to maintain the pre-stripping fleet in order to reduce travelling times to the main workshop. As expected, the improved operating conditions will lead to an increase in pre-stripping production.

Jan 1, 2013

By U. W. O. L Vogler

"The behaviour of rocks depends on their material properties, and therefore it is important that these properties are determined by relevant and reliable laboratory testing methods. The ISRM Suggested Methods are very important documents in this regard, and a draft suggested method exists for the determination of the ’complete stress-strain curve for intact rock in uniaxial compression’. The method specifies the required geometry of specimens and the required testing procedures. The research described in this paper involved the determination of complete stress-strain curves for two materials, one exhibiting the Class I characteristic, and the other the Class II characteristic. To obtain a better understanding of the deformation behaviours in the post-peak region, tests were carried out on specimens of both material types with different length-to-diameter ratios. The results showed that the geometries of the test specimens influence the stressstrain curves in the post-peak region. The implication is, therefore, that the numerical values obtained for the slopes of the post-peak graphs are not material constants, but are geometry-dependent. Explanations for this behaviour are given. These findings have important implications regarding the use of post-peak data, for example for blast fragmentation considerations, and for evaluation of rockbursting potential. The research findings are based on a limited amount of laboratory testing, and should be confirmed by further testing. IntroductionThe most common approach for studying the behaviour of rock is by compression testing of cylindrical specimens in the laboratory. Rocks respond to forces by deforming and eventually breaking. The strength and the deformation characteristics are derived from the stressstrain curves produced. Standard shapes and sizes for the test specimens and standard loading rates are recommended in the Suggested Methods of the International Society for Rock Mechanics (ISRM) and the American Society for Testing and Materials (ASTM) standards. In spite of these standards, there remain certain aspects of testing which require further attention. The research described in this paper deals with deformation and failure behaviour of rock materials using stiff, servocontrolled testing equipment. The particular objective was to test the premise that the behaviour of cylindrical rock specimens in the post-peak region of the stress-strain curves does not reflect only a material characteristic, but is influenced by the height-to-diameter ratio (the geometry) of the rock specimen. An additional objective was to investigate the effect of the stiffness of the test equipment on the outcomes of tests."

Jan 1, 2016

By M. Gholinejad

Applying non-explosive expansion material (NEEM) is one of the safest methods for rock fracturing, especially in a hard rock quarry. An experimental study was conducted to determine the pressure exerted by NEEM in a hole, which is necessary for analysing rock fracturing, particularly in a numerical modelling. Stress distribution was developed in a thick-wall cylinder in order to measure the tangential strain on the external boundary. In the experiments, nine pipes of different materials and varying diameters were selected and then loaded internally with a general type of NEEM. Through electrical strain gauges, the tangential strains were recorded on the external boundary of the pipes. The results obtained from these tests and existing data from previous researchers were utilized for the statistical analysis. A new experimentally-derived formula is proposed for determining the pressure exerted by NEEM by multiple parameter regression with a high correlation coefficient. The proposed model has a nonlinear form with three independent parameters i.e. the hole diameter, the time, and the modulus of elasticity of the material.

Jan 1, 2012

Acid heap leaching has been extensively applied to the processing of copper oxide ores, with recovery of copper by solvent extraction and electrowinning. Heap leaching has also been extended to the treatment of secondary sulphide copper ores, where oxidative conditions are generated in aerated heaps by the bacterially-assisted oxidation of ferrous iron to ferric iron. The treatment of low-grade chalcopyrite ores has recently been the focus of research, with Mintek playing a prominent role. When processing chalcopyrite ores, more complex column test work is performed, which incorporates the prediction and simulation of temperature behaviour in pyrite-containing heaps. Mintek has devised a trade-marked column leaching apparatus (SmartColumn?) for the simulation of the natural temperature profile development in pyrite-containing heaps. As heap leach applications are becoming more complex, the parameters that need to be built into the design and operation of heap leach plants are growing in number, and the amount of data to be collected and processed, and the number of decisions to be taken daily, are also increasing. Mintek has therefore developed the HeapStar® administrative advisory software, as a guidance system to ensure that the correct protocols are implemented at various stages of the leach cycle.

Jan 1, 2012

By H. Jeram

The ilmenite, rutile and zircon processes of the mineral separation plant generate tailing streams, which still contain valuable mineral. This is due to a combination of factors, which include separator equipment efficiency, particle size effects and inefficient operating practices (equipment overloading, blockage, etc.). Recent developments by metallurgical equipment suppliers have led to increased mineral separator performance enabling recovery of previously lost valuable mineral. Mineralogical studies were conducted using QEM*SEM and MLA techniques to identify and quantify gangue mineral species and determine mineral association. Laboratory and pilot-scale test work was then conducted to develop suitable process flowsheets for the recovery of ilmenite, rutile and zircon from current and stockpiled tailings.

Jan 1, 2007

By H. E. Bartlett

This paper deals with the sampling and mass measurement for ore delivered from a shaft to a processing plant and the contribution of the data from these measurements to the metal balances from shaft deliveries to final metal production. Accurate measurement of the grade and tonnage of run-of-mine ore is important for four main reasons; ? It enables the measurement of the production from different profit centres to within statistically determined confidence limits for daily, monthly, or annual averages. The profit centres could be individual shafts within a mining complex or ore treated on a toll basis ? The monthly production at shaft head is compared to the grades and tonnage determined from underground sampling and mass measurement in terms of a shaft call factor ? The sum of the production from the shafts is the input to concentrators. This input is a major part of the total input into a complex with concentrators, smelters, and refineries. In terms of the Codes of Practice for Metal Accounting the inputs are compared to outputs and inventory changes to assess the efficiencies and unaccounted losses or gains at the various stages in the flow of metal from source to market ? On a daily or daily moving average basis, the grades and tons from shafts are monitored and compared against these quantities from underground measurements. This acts as a control on off-reef mining, dilution, and other factors underground. Accurate measurement of grade of ore at the shaft head has been a challenge because of the large particle size. The conventional wisdom has been that ore can be sampled accurately only after it has been milled to give a slurry that is sampled as feed to a flotation process. However, when the ore fed to a flotation plant comes from multiple sources each source has to be sampled separately. So, relying on the grades determined using the sampling of concentrator input with cross-stream slurry samplers is not an option for determining the grade from an individual shaft. Impala has developed a system for sampling and weighing run-of-mine ore from multiple shafts. The system involves sampling the inputs to the plants using cross-belt (hammer) samplers and weighing the deliveries using in-motion railway weighing systems. Many samples are taken. Individually they have a high variance but, as a consequence of the averaging effect of large numbers and as shown by statistical analysis, the mean results are fit for the purposes of daily grade control for shafts and for monthly accounting of production from individual shafts. In the metal accounting systems at Impala, the measurement of input, including ore and toll-treated material is compared to the output in the form of final metal and tailings losses, as well as any inventory change that takes place, in order to determine a final metal balance from mill feed to product. The calculated inventory is compared to that measured, and the difference, or unaccounted- for metal, is then reported as a percentage of input. The balances obtained over several years yields balances for platinum that are below 1% imbalanced. Keywords metal balancing, platinum mines, AMIRA codes of practice, metal accounting, sampling, run-of-mine ore, statistical analysis.

Jan 1, 2014

By J. Gholamnejad

Determination of the optimum cut-off grades is one of the most important aspects of mine production planning. A cut-off is a grade below which we choose not to process material. This material is treated as waste and dumped. Dumping waste is accompanied by the rehabilitation cost which will affect the overall cost of final production and also the optimum cut-off grade. Rehabilitation cost is the cost per ton of rehabilitating material of a particular type of rock after it has been dumped as waste. One of the most popular algorithms for determination of the optimum cut-off grade is Lane?s method. Lane formulated the cut-off grade optimization, but he did not consider rehabilitation cost during the optimization process. This cost item should be evaluated first, and then considered during the cut-off grade optimization process. In this paper the rehabilitation cost is inserted directly into the cut-off grade optimization process using Lane?s theory. The cut-off grades obtained using the suggested method will be more realistic than ones using the original form of Lane?s formulations.

Jan 1, 2009

By D. Farrow

Future development of kimberlite mines is now focused on mining at deeper levels. The consequences are increased difficulty and costs of the mining operations. The decisions on investments require accurate resource evaluation and quantification of the risk. In the decision process the first step consists in choosing the number of boreholes sampling the pipe relative to the level of uncertainty that can be accepted. The uncertainty in the volumes of rocks of different types can be assessed as soon as we can estimate these volumes from a given borehole layout and calculate the error by means of its variance for instance. In theory this can be achieved by using geostatistical techniques (‘transitive theory’), but in practice the calculation of the error on volumes can be achieved in very particular cases, assuming some regular sampling patterns. A different approach has been chosen based on simulations, giving maximum flexibility to reproduce the reality of the sampling procedure. The idea is to simulate the geometry of several ‘possible’ pipes with their internal geology and estimate them by kriging. Several experimental errors are obtained on which risk analysis can be performed. The aim is to find a feasible method to perform the simulations with reasonable chance to correctly represent the reality, without data on the pipe extension. The methodology applied is based on some hypotheses that can be assessed by the geologist as well as by the geostatistician. The procedure assumes a geological model based on current knowledge including appropriate geostatistical variation. What make these simulations specific and powerful in this case comes from the fact that the boundaries between the different rock-types can be simulated using a transformation of the real 3D space into a 2D space defined by means of polar coordinates. Ultimate transformations to account for smoother variations with morphological transformations allow the generation of realistic pipe geometries on which sampling pattern can be used to evaluate the estimation errors. By estimating the simulated pipe geometries with different boreholes layouts a risk curve expressing the uncertainty in the volumes of the different rock-types versus the number of holes can be developed.

Jan 1, 2003

By A. Cáceres, L. Navarro, N. Altmann, R. Betinol

Copper concentrate is produced in Chile in the high Andes and transported to the coast for shipping through long distance pipelines. The pipeline and fittings installed have to withstand the high abrasion and corrosion environment of the copper concentrate. To protect the inside tube wall against corrosion, high density polyethylene (HDPE) liner is used. While HDPE liners can protect the steel wall against corrosion, it has also been assumed that the low surface roughness of the HDPE liner also inhibited incrustation caused by calcium carbonate and sulphate deposition. Recent events have indicated otherwise in a couple of concentrate pipelines for which BRASS has provided consultant service. This paper delivers a case study which includes (i) formation of incrustation and adhesion to HDPE liner, (ii) the detection of the incrustation through hydraulic analysis, (iii) the mechanism of removal of incrustation, and (iv) the catastrophic effects of their presence in an emergency situation.

Jan 1, 2007

The special mixing requirements for backfilling are discussed, and the problems associated with the mixing of coarse and deslimed slurries, as well as the tailings from the gold plant are outlined. The mixing of binders which are used to strengthen backfill and the parameters for the scale-up of mixer pilot plant work are also discussed

Jan 1, 1988

By C. -I. Lee

Since the early 1970s, Korea has constructed many large-scale tunnels and underground storage caverns in response to the rapid industrial development. The rock mechanics engineers have accumulated valuable experiences in the area of underground space technologies. But they still face technical challenges in environmental and safety aspects. To discuss those challenges in Korea, a brief engineering description of underground space projects including oil and gas storage, food storage, pumped storage power plant, transportation tunnels, waterway tunnels, and radioactive waste disposal is presented. Mechanical and hydrological stability analyses of the storage caverns in Korea are also introduced. Depuis le début des années soixante-dix, le développement industriel rapide en Corée a entraîné la construction de nombreuses galeries et cavernes de stockage souterraines. Les ingénieurs de mécanique minière ont donc accumulé des expériences précieuses dans le domaine de la technologie de l’espace souterrain. Cependant, ils font toujours face à de nombreux défis techniques en ce qui concerne les aspects de l’environnement et de la sécurité. Pour présenter ces défis en Corée, l’étude présente décrit les projets d’espace souterrain, y compris le stockage de pétrole et de gaz, de nourriture, centrales de stockage pompé, tunnels de transport, tunnels navigables, et évacuation des déchets radioactifs. Des analyses de stabilité mécanique et hydrologique des cavernes de stockage en Corée sont aussi présentées. Seit Anfang der 70er-Jahre, baute Korea in Folge raschen Industriewachstums viele lange Tunnelsund unterirdische Lagerungsräume. Fachkräfte im Bereich Gesteinsmechanik sammeltenwertvolle Erfahrungen über unterirdische Raumtechnologien. Dennoch stehen sie auch heute nochvor technischen Herausforderungen im Bereich Umweltschutz und Sicherheit. Zur Erläuterungdieser Herausforderungen in Korea folgt eine kurze technische Beschreibung der Projekte zurSchaffung unterirdischen Raumes für beispielsweise Öl- und Gaslagerung,Nahrungsmittellagerung, Pumpspeicherwerke, Straßen- und Wasserstraßentunnels, als auchLagerung radioaktiven Mülls. Mechanische und hydrologische Stabilitätsanalysen derLagerungsräume in Korea werden ebenfalls dargestellt.

Jan 1, 2003

Namakwa Sands, an Anglo Operations Limited subsidiary, is a world-class producer of heavy minerals. A layer of duricrust imposes a pseudo-stratigraphy to the primary deposit and has sterilized part of the generally unconsolidated ore in the open cast mine. The bulk of this ore cannot be treated by the present infrastructure, which employs conventional mineral separation technology. The mineralogy of the cementing agent consists of magnesium and calcium silicates and minor carbonates in addition to clay minerals such as sepiolite and those from the smectite group. Although the duricrust ore is friable and can be easily crushed, the significant clay-sized slime fraction produced, in particular the highly sorptive sepiolite, adversely affects mineral separation. The geometallurgical challenge is to cost-effectively remove the slimes from the ore before it is delivered to the concentrator.

Jan 1, 2007

By G. R. Sawyer

Although backfilling has been in operation for many years, the methods for selecting appropriate slurry dewatering aids have, in some cases, been rather unsophisticated. This has led to many misconceptions regarding the role of the dewatering aid and its various means of application. Testing procedures employed in the correct selection of any practically applied dewatering aid must mirror the actual working processes in which they are to be used. This constraint necessitates the development of complex testing methods when applied to backfilling. The current testing procedures were scrutinized and their various merits noted. From this study a series of testing methods was evolved which incorporate the best aspects of these testing procedures with novel ideas which would eventually result in the correct selection of the dewatering aid. A major consideration in the application of any of these methods is the modus operandi of the backfilling process, and the relevance of the tests to the process. This work attempts to consolidate the testwork performed in the past and suggest new approaches in the correct selection of acceptable dewatering aids for backfilling.

Jan 1, 1988