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Geological mapping makes an important contribution to orebody knowledge during the evaluation of structurally controlled gold veins. Orebody knowledge comprises an understanding of mineralization characteristics relevant to evaluation, mining, processing and environmental issues and allows project expectations to be realistically set. Structural interpretation to define continuity and mineralization controls is a key part of geological risk reduction and the reporting mineral resources using the JORC and other codes. The Dolgellau gold belt is a small British field that produced an estimated 150 000 oz from narrow quartz veins. Historical records, recent exploration and production data, published material, and accessible surface and underground exposure provide a valuable case study. Previous mapping has shown the general geometry of vein systems, but tends to accentuate gross geological continuity. Recent work has attempted to determine internal vein architecture and examine the significance of the historical views of ore shoot controls. The work resulted in the definition of vein continuity scenarios for the gold belt and evaluation expectations associated with each. This has, in turn, led to a realistic view of what can be achieved from an evaluation and project development perspective.

Jan 1, 2009

Primary roof support represents the first line of defence against rockrelated falls of ground in underground mines, and improper utilization or misunderstanding of the applicability and behaviour of primary support can be costly from a safety standpoint. This is a major concern for underground mines, as roof support is the single most costly expense from a mining operational perspective. This is further backed by the evidence that, in the USA, hundreds of injuries and fatalities still occur each year because of rib, roof, and massive roof falls. Additionally, the fully-grouted passive rebar, fully-grouted tension rebar, and resin-assisted mechanical anchor bolts, which constitute a large portion (89%) of the 68 million bolts installed each year in underground mines in the USA can vary in cost quite dramatically. To mitigate this concern a study was conducted in 2010 by the National Institute of Occupational Safety and Health, in conjunction with Southern Illinois University of Carbondale, to assess the performance of primary roofbolts in underground coal mines for improved safety and cost. This was accomplished using underground roofbolt monitoring solutions, field data, and numerical modelling to better understand the quasi-static behaviour of underground coal mine roofs and the response behaviour of the bolts. In particular, over 170 instrumented extensometers, closure meters, shear meters, fully-grouted passive rebar, fully-grouted tension rebar, and resin-assisted mechanical roofbolts were installed at three coal mines across the USA. Of these three mines, two used the room and pillar extraction method and the other used the longwall extraction method. There was no evidence to indicate a difference in performance of the active primary roofbolts compared with the passive primary roofbolts. Additionally, in the initial loading phase, the active bolts showed no difference in loading, indicating that tension bleed-off is of more of a concern than originally thought. Lastly, for the initial computer modelling studies, challenges still remain in obtaining a good match to the in situ bolt measurements and replicating the discontinuous roof rock and in situ bolt behaviour over time.

Jan 1, 2014

By W. J. Kempson

As a result of the rising electrical energy costs in South Africa, a method was sought to reduce the overall electrical consumption of typical shaft systems. A typical shaft configuration was analysed and the primary energy consumers were identified. The ventilation fans for this system were found to consume 15% of the total energy of the shaft system. It was calculated that more than 50% of this energy is consumed by the shaft itself, more specifically, by the pressure losses that occur in the shaft as the ventilation air passes through it. In order to ensure that the theory being used for the evaluation of these shaft systems is accurate, a total of five shafts were instrumented and the actual pressure losses over the shafts plotted against time. These shafts were then analysed from a theoretical perspective. Finally, in order to ensure a thorough understanding of the behaviour of the ventilation air in shaft systems, the systems were simulated using computational fluid dynamics (CFD) techniques. There were significant discrepancies between the theoretical analysis and the CFD simulation during the initial comparisons. This discrepancy lessened as the complexity of the CFD models increased, until when the complete shaft was modelled using the full bunton sets, the pipes, and the flanges, the difference between the theoretical evaluation and the CFD simulation was small. This result demonstrates that the theory is insufficient and that the interrelated effect of the buntons and fittings has not been fully appreciated by current theory. The final phase of the work presented here was to evaluate the costeffectiveness of using different bunton shapes and shaft configurations. It is shown that the increase in the pressure losses and therefore the direct operating costs of the shaft can vary by as much as 80%, depending on the bunton configuration chosen. The placement of the piping in the shaft can increase the pressure losses, and therefore the direct operating costs of the shaft, by as much as 12%, depending on the placement of the piping in the shaft; this effect includes the use of flanges. The use of fairings on a large cage can reduce the resistance that the cage offers to the ventilation flow by as much as 30%. This, however, does not translate into a direct saving because as the cage moves through the shaft, the overall effect is transitory. These savings can be significant when the items highlighted in this work are applied correctly. Keywords shaft design, ventilation, energy consumption, modelling, CFD.

Dec 1, 2013

By C. Musingwini, T. C. Sebutsoe

"The primary objective of any mining business unit is to make profit by extracting, processing, and selling minerals from a particular mineral deposit. It is important to optimize extraction of the mineral resource given time, capital, and space constraints. Mineral extraction is often associated with uncertainty due to variable technical and human factors. Technical factors such as grade distribution, ground conditions, and equipment reliability influence the performance of a mining production system (MPS). The performance of the MPS is also impacted by human factors such as employee skills, health, and attendance. Uncertainty associated with technical and human factors often leads to actual output differing from what was planned. Therefore an in-depth analysis of the significant causes of deviations from the planned outcomes is relevant.In this paper we investigate the empirical relationships between inputs and outputs in a MPS in order to assist management in directing efforts at key production drivers. Once a MPS has been empirically characterized, more effort and resources can be focused on the key decision-making variables (DMVs) in order to meet the planned outcomes.For a typical underground, tabular, narrow-reef conventional drill-andblast platinum mine the face advance, face length mined, number of teams, team efficiencies, and team size have a statistically significant relationship with the centares (m²) produced, which is a key performance indicator (KPI). The production function derived in this study can be used to align the physical, technical, and human factors together to predict the optimal output level. The most significant production lever of the MPS is the face advance. IntroductionA mining production system (MPS) is a result of an iterative process of design, planning, and optimization of mining input variables and decision-making variables (DMVs). The MPS exists within the mineral extraction link of the complete mining value chain. It represents the stage where mining companies have the opportunity, through production, to start generating returns on the investments undertaken. Returns on shareholders’ investments can be realized at this stage."

Jan 1, 2017

By J. Witley

"Narrow tabular platinum group element deposits in the Bushveld Complex of South Africa are typically evaluated by diamond core drilling from surface. Several short deflections are drilled from each mother hole in order to obtain multiple intersections at a close spacing (less than 1 m). Examination of the intersections from deflection drilling revealed the importance of these deflections in understanding the representivity of the borehole, obtaining an estimate of the nugget effect, and mitigating the undesirable effect of the high grade variability at the ultra-short range that is a characteristic of these deposits. The use of deflections in estimation was investigated by means of a number of techniques and scenarios in order to find the most appropriate way to use them in an estimate. A significantly improved level of confidence was gained from using multiple close-spaced intersections rather than a single borehole intersection. IntroductionThe Upper Group 2 chromitite layer (UG2 or UG2 Reef) is known for its remarkable geological continuity, being traced almost uninterrupted for tens of kilometres. However, what is often less well emphasized is the high variability in platinum group element (PGE) grade and thickness (and therefore PGE content) and internal reef stratigraphy over very short distances (several metres or even tens of centimetres).This paper examines the application of short drill-hole deflections in evaluating UG2 PGE mineral resources at Marikana in the western Bushveld Complex of South Africa."

Jan 1, 2017

By T. Orupold

This paper covers the commercial development of gravity separation of fine particles using a Lamella High Shear Rate REFLUX? Classifier (REFLUX? Classifier), focusing primarily on coal applications. The REFLUX? Classifier is a fluidized bed device that incorporates a system of closely spaced parallel inclined channels located above the fluidized bed. These channels make it possible to achieve a significant suppression of the effects of particle size, resulting in a highly effective separation on the basis of density. The improved gravity separation performance is shown to be remarkably high, with a significant reduction in the variation of separation density with particle size, and a significant reduction in the change in Ecart probable error (Ep) with size. The first full commercial-sized units of the REFLUX? Classifier were field-tested in late 2009 in coal applications. More recently, the technology has been applied in fine particle separation in minerals applications and there are a number of full-sized units operating in chrome applications in South Africa. Initially, pilot-scaled units (typically the RC?300) were trialled in iron ore, mineral sands, and manganese plants amongst other minerals, typically after other technologies failed to achieve the desired results. Currently a number of laboratories globally are carrying out more testing in minerals applications. More than 50 RC? units are now operating in coal and minerals applications. This paper introduces the REFLUX? Classifier technology, identifies commercial applications, and gives some commercial results.

Jan 1, 2014

By C. A. Preece

Finsch Diamond Mine, part of De Beers Consolidated Mines (DBCM), is situated between Kimberley and Postmasburg in the Northern Cape, South Africa. The kimberlite pipe was discovered in 1960 and De Beers assumed full mining rights three years later. Production commenced in 1966 from an opencast mine, and the operation moved underground in 1990 by developing and implementing a new mining method of blast hole open stoping. A mechanized block cave was brought into production in 2005. While block caving was not new to DBCM, with productive caves having operated in Kimberley and Cullinan, from the outset, the Finsch caving operation was designed as the most advanced with a semi-automated ground handling system. The extraction level was laid out as a single sided herringbone system due to the very poor ground conditions on the south side of the pipe. These factors combined to create a unique environment, which necessitated a completely new approach to draw control. The required system was developed by a team consisting of DBCM personnel from head office and Finsch, GEMCOM and Sandvik-Tamrock, the equipment manufacturers. It was essential that the system could be run quickly, provide daily updates and issue calls directly to the LHDs. It was also important that the base data were obtained from the resource model, which was to be depleted on a monthly basis, thus forming a close link between mine planning and draw control. A further requirement of the system was that it would form a central database for the extraction operation where all data pertaining to delays and changes in conditions, be they production or ground condition related, could be recorded and analysed. The design brought together empirical rules and tables developed at Cullinan plus concepts from programming developed for the front cave at Koffiefontein so that the new system was based on sound practical experience. These facets were incorporated into PCBC (GEMCOM) and CMS and PCS (Sandvik-Tamrock programmes). The system has now been operational for just under a year and while modifications have had to be made, it has proved itself as a practical and reliable tool with which to manage the draw control at Finsch. The system is unforgiving and has forced the production team to focus on the specified drawpoints. Problems have been encountered but most of these have been related to re-educating a workforce, familiar with a flexible mining method, to the strict discipline required for a modern block cave.

Jan 1, 2007

By V. Matou?ek

The paper addresses pipe flows of aqueous medium-sand slurries at velocities lower than the deposition-limit velocity. Laboratory test results including measurements of particle concentration distributions are used in order to describe a flow with a (pseudo-) linear concentration gradient above a stationary bed. Particle dispersion within the flow is evaluated and a stratification-ratio equation is formulated, estimating a portion of contact load in the flow. The formula is incorporated in the proposed predictive model for the hydraulic gradient for a medium-sand flow above a stationary bed.

Jan 1, 2007

By D. Burrows

Traditionally, characterisation of the mineralogy and textures of ore and rock samples were based on observations of hand specimens and thin sections using an optical microscope. The extent of the data collection was limited by the available tools and thus variations in mineralogy and texture were generally not described by quantitative data. These qualitative to semi-quantitative approaches, even though well established over the years, resulted in variable observations and data sets. The data were unlikely to be representative of a sample and limited statistical validity meant the results could not be reliably used in modern digital mining design and planning. With recently developed SEM based quantitative mineralogy tools and the corresponding methodologies, ore textures can be quantified and compared numerically. The numerical data can not only enhance the understanding of an orebody in geological terms, but can also be used in the creation of metallurgical models for mine and mineral processing design and simulation. These capabilities provide valuable inputs to risk assessment studies and the evaluation of mineral projects.

Jan 1, 2007

The proper understanding of the functioning of ground support under dynamic loading and the current approaches to designing of dynamic support are plagued by a great deal of uncertainty and lack of knowledge. This applies equally to the understanding of the support capacity as well as the demand placed onto the support due to dynamic loading. This lack of understanding currently leads to a case of design indeterminacy. This paper does not aim to solve this problem of design indeterminacy but to explore some of the issues that need consideration to obtain a better understanding of the dynamic demand on ground support systems. Keywords ground support, dynamic loading.

Dec 1, 2013

By Kevin Peacocke

The future of Gravity ? Primary mineral recovery ? Enhancement of existing process efficiency ? Pre-Concentration ? Alternative? or ?New? production

Jan 1, 2006

By A. S. Macfarlane

Western Deep Levels (North) is a deeplevel, longwall gold mine. Severe strata control problems and high rates of elastic closure, resulting in high rates of energy release, are associated with mining at depths of up to 3 500 metres. To assist in controlling these aspects of mine design and safety, a waste backfilling system has been designed and commissioned. The integration of such a system into an existing, producing longwall brings many problems of logistics, organization, planning and control. It is the purpose of this paper to examine these aspects of fill management, and to describe some of the practical problems involved with the integration of this project into the mining environment. Although many of the rock mechanics and soil mechanics aspects of backfilling systems are common there are specific problems involved which apply to longwall systems. Very strict guidelines are required for planning personnel to design their backfilling systems for a particular situation. These aspects are examined, and basic models developed which can be used without the necessity of comprehensive input from rock mechanics. A summary of the financial implications is included, and these are examined with regard to possible future applications and expansion of waste filling.

Jan 1, 1988

The depletion of favourably located and higher-grade mineral deposits, combined with more favourable metal prices and higher capital costs, has stimulated research into heap leaching of lower grade ores and wastes. This has resulted in renewed interest in heap leaching of uranium ores, and in the development of processes for the bacterial heap leaching of low-grade chalcopyrite ores and the acid heap leaching of nickel laterites. A complete programme of heap leach testwork typically involves a sequence of bottle roll tests and column tests, followed by piloting on test heaps. The initial testwork is aimed at determining the amenability of the ore to heap leaching, which depends on the characteristic of the ore with respect to porosity and permeability to leach liquor, acid consumption, metal recovery and percolation. Subsequent phases of the testwork focus on the development of the process design criteria for the treatment of the ore. Basic techno-economic models have also been developed as a tool for the initial estimation of heap leach viability. Mintek has also developed in-heap monitoring probes, coupled to an operator guidance system, in order to assist the operator in achieving optimal conditions for bacterial growth and heat preservation during pilot-plant operation.

Jan 1, 2009

By P. S. Piper

In the 1960s it was suggested that the volume of stope convergence, and hence the rockburst hazard, could be reduced by the emplacement of backfill. Recent advances have facilitated the placement of large quantities of backfill underground, and a reassessment of its potential benefits as part of a regional support strategy is now timely. In this paper the principal criteria of effectiveness of backfill are taken to be its impact on face energy release rate (ERR) and average pillar stress (APS) levels, and maximization of acceptable ore extraction ratios. The possible effects of backfill on excess shear stresses (thought to modulate large seismic events) are also briefly reviewed. Analytic solutions describing backfill properties and their impact on ERR and APS in certain idealized geometries are also presented, and compared with the results of an extensive suite of computer simulations, in which parameter sensitivities are explored. Results indicate that a regional support strategy is required at depths exceeding 2 km in order to maintain acceptable levels of ERR, and backfill ribs can on their own fulfil this role at depths less than 3,3 km. At greater depths use of stabilizing pillars becomes imperative, but here too supplementary backfill ribs can reduce ERR and APS levels and permit significant increases in ore extraction ratios.

Jan 1, 1988

When designing coal mine roof support, it is necessary to account for the uncertainties and variability that inherently exist within the rock mass and support elements. The performance of a support system is affected by these uncertainties, which are not taken into account in the current deterministic design methodologies used in South Africa. The key to the design of a roof support system is a better understanding of roof behaviour and uncertainties that can been countered during extraction. This paper sets out to develop a method that takes all uncertainties that exist within the rock mass and the mining process into account and provides a quantitative risk-based design methodology.

Jan 1, 2009

By K. H. Berget, V. Andersen, H. Tveit, R. Jensen

This paper presents some of the work carried out in order to improve the tapping process in silicon production, with special focus on the environmental and the safety standards. Some of the modelling work that has been done to improve the understanding of the process is described, together with the resulting implementation to improve tapping standards.

Jan 1, 2014

By S. A. Ziebold

There is often a need to increase capacity through existing mist eliminator installations without significant tower modifications. Often there is not enough extra space outside existing vessels unless more expensive changes can be justified. Also, plant downtime must be considered. The challenge in retrofitting is to overcome velocity limitations inherent in the design while at the same time extend performance capability. The solution most often is to create new ways to add extra filter area while remaining constrained to the existing space. This strategy, however, can dangerously backfire if basic design principles are not followed. Mist eliminator design is a complex integration of many conflicting performance parameters. Often the objective is to increase scrubbing capacity while maximizing collection efficiency and service life and minimizing operating pressure drop (energy cost), particle regeneration (re-entrainment) and overall maintenance costs. Results of plant retrofitting using mesh pads, impaction fibre beds and diffusion fibre beds are presented based on actual plant projects. Often the retrofit project can be more effective by increasing the scope and combining other new plant equipment with the upgrade such as new tower components. In some cases, the type of mist eliminators can be upgraded from impaction type (velocity dependent) to Brownian diffusion type (velocity independent) if additional downstream protection or reduced emissions are desirable, especially at turndown rates. Trade-offs between different fibre bed types and styles are discussed as they relate to performance and maintenance.

Jan 1, 2007

By H. Moslemi

Metal sulphides are usually semiconductor and their electrical conductivity is low; therefore they are sources of electrons and promote electrochemical reactions. This phenomenon is of significant importance in sulphide flotation. The formation of a hydrophobic surface on the sulphide minerals is the result of various electrochemical reactions. Potential difference in the mineral-liquid interface plays an important role in the kinetics of the reactions, and consequently, on the flotation behaviour of sulphides. The value of the potential difference is influenced by different oxidation-reduction reactions at the interface area, and is measured by a two-electrode system in which an electrode is applied as reference electrode. In this study, we attempted to measure open-circuit potentials of pyrite, pyrrhotite, and steel electrodes with respect to the reference electrode. To verify the results, two reference electrodes, saturated calomel and gold, were used. Time-potential relations with respect to both reference electrodes show that the potential of both pyrite and pyrrhotite increases with time; however, this trend decreases for steel except when at pH 12. The results show a potential drop by an increase in pH value, except for steel, for which the opposite holds. This paper discusses galvanic interactions between minerals and grinding media in the grinding circuits, as well as among other minerals in the flotation processes.

Jan 1, 2012

Hydrometallurgical processing of complex ores and concentrates is becoming increasingly important as the mining and metallurgical industry seeks to exploit mineral deposits that are difficult to treat using conventional mineral processing and pyrometallurgical technologies. Mineral processing is often challenged by the difficulty or inability to separate valuable minerals into marketable concentrates. Hydrometallurgical processing, using selective leaching technology, can often ?chemically beneficiate? such difficult deposits. Pyrometallurgical treatment of base metal concentrates is capital intensive and subject to ever more stringent environmental control. Hydrometallurgical processing is generally lower in capital cost for an equivalent metal production rate and avoids the gas and dust issues associated with pyrometallurgical processing. The possibility of by-product recovery may also increase with hydrometallurgical treatment. Two examples of new technology or flowsheet development for treatment of complex ores and concentrates are used as illustration. These include the El Boleo process of Baja Mining for recovery of copper, cobalt, zinc and manganese from a complex clayey ore and the PLATSOL? process for recovery of copper, nickel, cobalt, platinum, palladium and gold from a bulk sulphide concentrate.

Jan 1, 2009

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012