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By T. A. Ngcobo

Paper written on project work carried out in partial fulfilment of BSc Eng (Mining)degree The purpose of this report is to assess the risks faced by mines in dolomitic compartments in particular Kloof 8 shaft. The dolomites of the West Rand comprise one of South Africa?s most natural water resources, and overlie the reefs of the richest gold mines in the world. The pumping of water from the dolomitic aquifers to prevent flooding has caused the natural water table to subside, and the resulting cavities within the dolomite rock formations that overlie many gold deposits sometimes collapse, causing sinkholes. These impacts of the mining industry could worsen over time if preventative measures are not taken. This report discusses these impacts in detail, more specifically the risks to which operations in dolomitic compartments are exposed. A risk analysis was carried out to access the risks that the organization could face and it was this analysis that allowed one to examine the best methods to combat the problems. Other factors such as geological features and seismic events were also considered for the evaluation. To aid with the completion of this work various resources were utilized. A literature study was undertaken, information was gathered from various experts who specialize in dolomitic studies, evaluations were conducted and conclusions reached. The results from the project indicated that preventative measures should be implemented and correct procedures put in place to prevent any disasters.

Jan 1, 2006

By L. R. C. Cairncross

In this study, the general case of semi-batch precipitation of nickel hydroxide, Ni(OH)2, is modelled. In practical terms, this precipitation may occur at high ionic strengths, and therefore the model for solution chemistry requires a thermodynamic model that is applicable for these non-ideal systems. The activity coefficient model used is the ELEC-NRTL. The simulation of the solution chemistry is performed using AspenPlusTM, which is a steady-state process simulation program. This allows for rigorous evaluation of the solution speciation, and hence the degree of supersaturation which dictates the precipitation kinetics. The solution chemistry provides the basis for predicting the formation of solids. The model consists of a solution chemistry part and a solids formation part. The inputs to the model include the initial concentrations of the streams entering the reactor, kinetic parameters for the precipitation processes, and a particle size distribution obtained from experiments. The solids formation part of the model employs the method of moments for the evaluation of the population balance. The population balance accounts for total particle number, and the formation and increase in size of particles across the entire particle size range. This balance requires kinetic parameters for the processes of nucleation, growth and agglomeration. Using optimization routines inherent in AspenPlusTM, parameters for the rate of nucleation, growth and agglomeration may be extracted from experimental particle size distributions. These are then used in the model to extrapolate to other conditions. Once an understanding of the kinetics of the precipitation processes is gained, the model provides a predictive tool for optimization of these kinetics, in order to increase the overall particle size and therefore improve solid-liquid separation. The work is deemed to be significant as it sheds some light on solids formation processes involved in precipitation?including nucleation, growth and aggregation?and develops a predictive modelling tool applicable to solutions of high ionic strength. We argue that this dewatering of suspensions is affected significantly by particle size distribution and surface properties of the solids formed by precipitation. This modelling tool should facilitate the design of solids formation processes where downstream dewatering is enhanced.

Jan 1, 1997

By J. Engelbrecht

South Africa?s re-entry into the fast moving and competitive global economy calls for some careful strategic planning and a good deal of co-operation between suppliers and end-users. The issues that need addressing are generally well known and include: ?South Africa was ranked 45th out of 46 i.r.o. productivity ?SMMEs contribute 1% to exports compared to 40-60% for the ?tigers? ?High unemployment ?Limited skills of the majority of workers ?Slow growth rate of the economy ?The vast majority of suppliers are not world-class ?The vast majority of suppliers are not export or marketing orientated. In order to survive, all parties, i.e. government, labour and business, will have to play their part.

Jan 1, 1999

By H. T. Ozkahraman

It is important to know the breakage mechanism in materials since this knowledge influences the results of subsequent grinding operations. There are two distinct failure mechanisms in breakage: one is tensile micro crack generation at low stresses, which leads to macroscopic failure by disintegration, and the other is formation of shear zones under heavier dynamic impact forces, which generates more fines as seen in crush zones in blasting. Tensile fracturing simply breaks the material into fragments. It is seen as the disintegration of the specimen into two or more separate fragments. This happens under the absence of lateral stresses and the material is free to expand. On the other hand, compressive-shear breakage produces finer fragments due to shear stresses. The first mechanism is observed in laboratory tensile and bending strength tests and the second mechanism is observed both in laboratory brittleness tests and in situ blasting operations under dynamic impact forces. The friability of rocks and ores can be determined by a brittleness test. A test apparatus to determine the friability value has been designed to suit limestone strength characteristics used in cement production. The friability and stored strain energy values of barite, marble, limestone and bauxite have been determined and compared with the corresponding Bond work index (Wi) and grindability index (G) of these materials. The physico-mechanical properties of the tested materials have also been determined to investigate their effect on friability and grinding. The relationships obtained between the indices were in surprisingly good agreement, with high correlations (0.99 and 0.97). The Bond work index and grindability index can therefore be estimated from the friability value, which can be determined more rapidly than the Bond test. But for certain rock types such as andesites the relationships does not hold. Key words: comminution, tensile stress, shear forces, brittleness test, strain energy.

Jan 1, 2010

By Yijun Caoa, Xiuxiang Taoc, Zhongbo Hub, Yinfei Liaoa

A new preparation scheme for a difficult-to-float coking coal from the Kailuan Mine, Tangshan, China was investigated. The results showed that grinding followed by column flotation was beneficial for obtaining products with low ash content. The positive effect of grinding on the coal floatability is attributed to the liberation of intergrowths and coal surface improvement. Tests indicated that 10 minutes was the optimum grinding time, and over grinding resulted in a deterioration in flotation performance. With a grinding time of 10 minutes, conventional flotation had potential to yield a product with around 12.42% ash content and 69.15% combustible recovery. Column flotation can reduce the product ash content to 11.15%and increase combustible recovery to 74.47%. Consistently better flotation results reveal that column flotation is more efficient than conventional flotation for such fines.

Jan 1, 2015

By B. Samanta

A quality characteristic analysed through construction of the Shewhart control chart is required to be normally distributed. In mining applications, this assumption is often violated as many quality characteristics follow skewed or lognormal distribution. In this paper, two methods were investigated using a heuristic approach for setting up the control limits for a skewed population. Based on these approaches a Mode chart, and a Weighted Variance (WV) control charts were constructed. The performance of the proposed methods was compared with the normal based Shewhart method through a case study conducted in a surface mine supplying iron ore to a steel plant. A simulation study was also conducted to evaluate the effectiveness of the proposed methods over the Shewhart method. The study revealed that the Shewhart control charts generated more out of control alarms compared with the Mode and Weighted Variance control charts for a skewed population of Fe%. The simulation results also revealed that for extremely high skewed population, the WV control chart and Mode control chart provided higher probability of coverage than the Shewhart method; although the detection rate (probability of detection) of out of control condition for these methods was slightly reduced compared with Shewhart method.

Jan 1, 2004

By F. Sawyerr

A bubble population balance model is proposed for the prediction of Sauter mean bubble diameters in mechanical flotation cells. In the model, the flotation cell is treated as two separate, statistically homogeneous zones?the impeller zone, and the bulk tank zone. Balance functions for the rates of bubble breakage, coalescence, recirculation and inlet-outlet events are proposed based on classical chemical engineering research in two- and three-phase fluid mixing systems. An initial simulation of the population balance model shows trends in bubble size distributions comparable to measured distributions in industrial mechanical flotation cells.

Jan 1, 1998

By D. S. Richards

Computers have revolutionized the collection of data on modern mines. Never before has it been possible to collect data from all aspects of the mining value chain at rates now common. With this has come a new challenge. Deriving information from these copious amounts of data and disseminating it. This problem is being exacerbated by technical software systems, which use proprietary and binary data formats that severely inhibit the flow of data and information both across departments and the larger organization. Generally this had led to data duplication and data redundancy. The Gemcom Enterprise Mining System (GEMS) makes use of industry standard, secure and open databases for all its data objects. It manages multiple users accessing the same bits and bytes in the database, preventing data duplication and redundancy. Developed in the Microsoft BackOffice ® environment, GEMS is also able to leverage the enormous amount of tools available in this environment, whether it’s for e-mail notification, reporting or data capture. Microsoft’s® Active Server Pages are one of these tools. These are standards used to create dynamic and interactive web pages with links into databases and many other objects. The real example outlined in the text, demonstrates how a user anywhere in the world is able to login to a web page and run a query that returns a report with vector plots of performance for the user-selected time frame. As integration is tightened between the various components of the mining value chain, the importance and reliance on ASP pages will grow as the need for management information tools develops. Keywords: mines, computers, ASP, GEMS, integration, Microsoft, Management Information.

Jan 1, 2003

By W. G. Huang

To recover the coal resources of high-sulphur anthracite in Jincheng Mining Area, underground coal gasification (UCG) of No. 15 seam in Fenghuangshan Coal Mine was proposed. The feasibility of the project was confirmed by investigations of occurrence conditions, coal properties, and roof conditions, as well as experimental studies and theoretical analysis. It was found that UCG technology is appropriate to be adopted in the mining of the No. 15 seam, due to the stable rock conditions, simple geological structure and hydrogeology, the high carbon content of the coal, non-cohesiveness, medium-thermal stability, high ash fusion temperature, and weak reactivity with CO2. Further factors are the characteristics of the immediate roof, which consists of 9.11 m of limestone and mudstone with a compact structure and low permeability, and 4.27 m of dominantly mudstone with low permeability.

Jan 1, 2012

By C. Musingwini

The South African mining industry continues to be a major source of employment at a time when at least 25 per cent of the working age population is unemployed. At the same time the industry faces a skills shortage in many of the disciplines necessary for its future health. The University of the Witwatersrand, University of Pretoria, University of Johannesburg, and University of South Africa have historically produced mining graduates for the South African mining industry with any shortfall being met by the recruitment of overseas graduates. More recently, the global shortage of engineers and other mining industry professionals has seen a reversal of this trend and a very significant emigration of well-educated and highly skilled personnel. The traditional career path for mining graduates is in production and mine management. However, there is the parallel (and possibly more pressing) need for specialized skills in such fields as ventilation, rock engineering, mine planning, mineral resource evaluation, and mineral asset valuation. Chronic shortages in these essential areas continue to hamper the development of the industry and may well frustrate its ambitions to be safe, healthy, and profitable into the future. The permeability of skills across sectorial boundaries within the mining industry requires that skills shortages in the platinum sector are not looked at in isolation, but within the context of the entire industry. This paper reviews the efforts being made by the universities, at both undergraduate and postgraduate levels, to meet the needs of the South African mining industry in terms of the required numbers and the range of specialized skills.

Jan 1, 2013

By T. E. Pogue

This paper traces the co-operative initiative undertaken by South Africa?s gold mining companies through the Chamber of Mines Research Organization (COMRO) in development of hydraulic technologies. After a brief description of the structure of these technologies? development under COMRO?s stewardship, the paper turns to an overview of the structure of innovation within which these hydraulic technologies were developed. A central focus of this paper is systematic review on whether similar technologies are likely to emerge in the present system of innovation and the role played by innovation policy.

Jan 1, 2006

By P. J. van der Walt

Some 30 years ago exposure to dense-medium separation in South Africa, culminated in the adaptation of the process for the treatment of -0.5 mm fines. The first commercial plant at Greenside Colliery apparently operated for some 18 years. Three further plants followed, including one treating tin ore. It is gratifying to learn, therefore, that there is renewed interest. The objective of making the process easier to operate (?more practical??) is commendable but the cumbersome technical approach could be counter productive. Perhaps a brief outline of the original thinking might be helpful when analysing the problem.

Jan 1, 2003

O.F.S. Branch, Welkom Minutes of a Committee Meeting held in the V.LP. Lounge of the Welkom Club on Tuesday, 26th June, 1973, at 5.00 p.m. Present Mr C. J. Isaac (in the Chair), Mr D. A. Smith, Mr G. Young,

Jan 1, 1974

By D. A. Bruce

The paper describes the construction of 5 plugs to resist high water heads at depth within the South Deep Gold Mine, Randfontein, South Africa. A total of 20 segments were involved to create these plugs, which were 7.5 m long at the 58 Level and 6.25 m long at the50 Level. Emphasis is placed on the QA/QC and verification methods, which were developed and governed all phases of the work, from initial rock preparation and pregrouting through to the final grout tightening of the rock/plug interface and the surrounding rock. This paper is one in a series of papers detailing other aspects of the project, which was constructed largely between May 2001 and August 2003.

Jan 1, 2006

By M. Kumral

Raw material fed into a processing or refining plant is required to be uniform in composition for several reasons. When the mined ore is highly variable in quality the only way to ensure consistency is to homogenize the ore prior to the process. The problem is more complicated in the case of multiple ore sources. The idea behind the research is that theoretical blending ratios can serve not only to meet predefined specific criteria but also to reduce grade fluctuations of variables under consideration. In this paper, the problem is formulated as a quadratic programming problem, whose objective function is in quadratic form and constraints are linear. A case study was conducted on a data set from an iron orebody to demonstrate the technique. The objective was to minimize the blend variability in terms of each variable (in this study, iron, silica, alumina and lime) grade of ores extracted in three different production faces. The stockpile capacity, lower and upper limits of each variable satisfying operational requirements and non-negativity were constrained to the model. A modified simplex method developed by Wolfe was used for solving the blending and homogenization problem. The promising results can be used as apart of the stacking and reclaiming design. Keywords: blending and homogenization problem, quadratic programming, Wolfe method.

Jan 1, 2005

By M. Vandewalle

What separates the support of mining openings from the support of similar civil engineering structures is the fact that mine openings have to survive large deformations as a result of changing stress conditions induced by progressive mining. Steel fibres impart to concrete and shotcrete a high degree of ductility which not only allows the shotcrete and concrete linings to absorb important rock movements but also to increase its bearing capacity by a redistribution of the loads. A range of applications will be discussed technically and economically.

Jan 1, 1998

By R. Altindag

The rock brittleness is one of the most important rock properties that affect the drill-ability of rocks. It is supposed that the increase in rock brittleness causes the increase in penetration rate. The drill-ability of rocks depends on many factors. These factors can be separated as two parts depending on a machine, bit type, rotational speed, thrust, blow frequency, flushing, and rock properties, brittleness, compressive strength, structure, hardness, etc. In this paper, the relationship between brittleness and drill-ability index, which is used in the prediction analysis of the penetration rate of rotary blast hole drills, were examined using regression analysis. It is also seen that significant correlations exist between brittleness and the drill-ability index.

Jan 1, 2002

By F. T. Cawood

The new South African Mineral Policy has major implications on the way mineral rent will be collected and shared between the stakeholders in future. Although the policy does not supply details on how this will be done, drastic departures from practices under the previous dispensation require a new approach. For example, there introduction of the ?right to mine? principle implies that the repealed lease consideration concept will be expanded to all minerals. The new policy also makes provision for predetermined standard terms and conditions for all prospecting and mining permissions. It also states that, regardless of whether the mineral rights are state or privately-owned, all prospecting fees and mineral royalties will be determined by state officials after consultation with the registered holder of the mineral rights. This paper proposes a standard mineral royalty formula that complies with the principles mentioned in the White Paper and has been shown to be internationally competitive.

Jan 1, 2001

By C. F. Vos

Small replacements of C12-trithiocarbonate (C12-TTC) for dithiocarbonate (DTC)/dithiophosphate (DTP) in a reagent suite for the flotation of platinum group metals (PGM) have significantly improved the rejection of gangue. Coupled to this is an improvement in kinetics, grade and recovery of PGMs. In a pilot-plant trial, after a 5 mole per cent replacement of the current DTC/DTP collector combination by C12-TTC, large opaque bubbles were replaced by small clear ones. In addition, a similar flotation response was realized with one-third of the current depressant dosage. During a preliminary plant trial on underground UG2 ore, the initial rougher concentrates were characterized by higher PGM concentrate grades and this was in part due to improved chromiter ejection. The concentrate produced from the TTC trial also exhibited a much finer particle size distribution. The overall circuit performance, which included secondary regrind and flotation, showed an increase in concentrate grade of approximately 44% while the tailings grade remained unchanged

Jan 1, 2007

Council for 1999/2000 President M.H. Rogers President Elect Dr L.A. Cramer Vice Presidents Senior A.A.B. Douglas Junior S.J. Ramokgopa Immediate Past President J.R. Dixon Honorary Treasurer J.A. Cruise [ ] Annual report In accordance with the current management policy, this report on the activities of the Institute is presented under eight main headings: 1. Interests of Individual Members 2. Technical Meetings 3. Publications 4. Regional Development 5. Engineering Science and Technology in South Africa 6. International Liaison 7. State Liaison 8. Management and Administration.

Jan 1, 2001