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By J. A. L. Napier

This paper presents an overview of work carried out by the CSIR Division of Mining Technology and formerly by the Chamber of Mines Research Organization (COMRO) to quantify the behaviour of the stope fracture zone near deep level goldmine stopes. The motivation for this work is first reviewed in the context of the unsatisfactory status of current mine layout design criteria. Numerical methods to represent failure processes are reviewed briefly. Specific studies of microfracture processes are described as well as physical modelling experiments that can yield insights into deformation mechanisms. Modelling of stope scale deformation mechanisms are presented and considerations relating to elastodynamic modelling of the rock mass are described. The implications of this understanding in relation to prospects for active fracture zone ?engineering? are outlined and finally, the directions of future research work are proposed.

Jan 1, 1997

It is predicted that vast volumes of affected mine water will be produced by mining activities in the Mpumalanga coalfields of South Africa. The potential environmental impact of this excess water is of great concern in a water-scarce country like South Africa. Research over a period of more than 10 years has shown that this water can be used successfully for the irrigation of a range of crops (Annandale et al., 2002)1. There is, however, continuing concern from the local regulators regarding the long-term impact that large-scale mine water irrigation may have on groundwater quality and quantity. Detailed research has been undertaken over the last three years to supplement the groundwater monitoring programme at five different pilot sites, on both virgin soils (greenfields) and in coalmining spoils. These sites range from sandy soils to very clayey soils. The research has included soil moisture measurements, collection of in situ soil moisture over time, long-term laboratory studies of the leaching and attenuation properties of different soils and the impact of irrigation on acid rock drainage processes, and in depth determination of the hydraulic properties of the subsurface at each of these sites, including falling head tests, pumping tests and point dilution tests. This has been supported by geochemical modelling of these processes to quantify the impacts. The results indicate that many of the soils have considerable attenuation capacities and that in the period of irrigation, a large proportion of the salts have been contained in the upper portions of the unsaturated zones below each irrigation pivot. The volumes and quality of water leaching through to the aquifers have been quantified at each site. From this mixing ratios have been calculated in order to determine the effect of the irrigation water on the underlying aquifers. Keywords: coalmines, irrigation, gypsiferous mine water.

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 J. Hadjigeorgiou, T. R. Stacey

This paper introduces the Quantified Value-created Process (QVP), a decision-making process for use in mine design and operation. The implementation of the QVP is founded on a ten-step rock engineering design process and a ten-step strategic planning process. The potential of this approach is demonstrated by examples of value created as a result of good research, design, and planning. The QVP is divided into two parts, namely, a ‘planning the process’ section and an ‘implementing the process’ section, and can be considered to be an extension of the risk approach. All costs, direct and indirect, associated with a significant mining decision (design, operational, investment) must be quantified in advance of committing to that decision, to determine the value that will be created in the short, medium, and long terms. Ethical values, associated with health, safety, the environment, public perception, and social aspects, may be difficult to quantify in economic terms, but must nevertheless also be considered. In contrast with a traditional risk approach, the QVP will identify the upside, and allow executives to make more informed strategic decisions. In this context it is essential to actively engage upper management in the decision process.

Feb 2, 2022

By A. E. Lewis

Particle morphology is a term that is used to describe the overall external shape and appearance of particulate solids. From the physical point of view, a precipitated solid is characterized primarily by the size and morphology of the particles (Sohnel andGarside, 1992). If the morphology of the crystal structures is to be related to the processing conditions, then the morphologies need to be quantified in some way. This can be achieved by using surface area measurements as well as fractal dimensions. The key idea is that rugged and indeterminate systems can be described by using a fractional number that describes the ruggedness of the system (Kaye, 1989). In other words, when the complexity of a structure, such as an agglomerate, increases with increasing magnification, it is useful to employ fractal dimensions to describe the structure. Fractal geometry proposes that, instead of attempting to measure the length of an irregular boundary, the rate at which the length of the boundary approaches infinity with increasing resolution should be calculated. Cross-sectional profiles of rugged particles can thus be quantified using the fractal dimension, and a measurement of the ruggedness of the morphology obtained. One of the additional uses of measuring the fractal dimension is that the measured value can be related to the physical properties and formation characteristics of the particle (Kaye and Trottier,1995). The morphology of nickel crystals was quantified with fractal dimension calculations of particle cross-sections. Particle cross-sections were obtained by mounting the particles in resin and polishing back. These were then photographed using Scanning Electron Microscopy and the resulting profiles analysed using the structured walk technique.

Jan 1, 2001

The current methodology to design stope support systems in South African gold and platinum mines is based upon the tributary area concept. The discontinuous nature of the hangingwall rock is not adequately addressed, and mechanisms leading to rock mass failures between adjacent support units are poorly understood. The work reported here aims to formulate a basis for quantifying support mechanisms and gain insights into the influence of rock discontinuities on stable hangingwall spans. Numerical models are used to qualitatively investigate the stress transfer from the support units to the discontinuous hangingwall. Stable hangingwall spans are quantified by considering two failure mechanisms, namely (i) beam buckling, and (ii) shear failure due to slip at the abutments. The output of the proposed design methodology is appropriate site specific support spacing, based on discontinuity spacing and orientation. The method is particularly suited to mines at intermediate and great depth, where typically the hangingwall is highly discontinuous due to face parallel mining induced fractures. Results of parametric studies show that with increasing in situ compressive hangingwall stress, beam thickness and friction angle, hangingwall stability is increased, leading to wider stable hangingwall spans between adjacent support units.

Jan 1, 2000

By M. Grodner

Underground excavations exhibit different hangingwall conditions in response to varying geotechnical and mining situations. These differences need to be quantified so as to accurately determine the effectiveness of the mining and/or support strategies. A useful tool for the quantification of these differences is hangingwall profiling. Two methods of hangingwall profile measurement are described?termed irregular and periodic methods. Several data analysis techniques are reviewed for these methods and the suitable ones are discussed in detail. For irregular data the suitable techniques are the determination of the length, the average of the profile and the average absolute deviation from the mean of the profile. All of these techniques as well as determination of the moving average of the height and examination of the spectral image of the profile can be successfully applied to regular data. The effect of preconditioning on the hangingwall is discussed as an example and it is quantitatively shown that it results in improvements of conditions. The techniques described allow the engineer to quantitatively identify the appropriate support type or mining strategy and thus represent a valuable decision-making tool. It is suggested that these techniques should be employed on a routine basis by the rock engineers on the mines as part of their geotechnical classification, as well as support manufacturers to quantify the effectiveness of various support types.

Jan 1, 2000

By M. Z. Emad, A. Khan, N. Abbas, K. G. Li

Probability-based empirical methods were employed as an alternative approach to predicting uncertainties associated with rock mass properties. The focus was on developing probabilistic spreadsheets to forecast rock mass classification indexes. Histograms were constructed to describe the best distribution in predicting rock mass properties. The developed models also offer utility in predicting the impact of discontinuities within the rock mass on rock strength and rock mass classification systems. Statistical analyses identified volumetric joint count, joint spacing, joint frequency, and rock strength as the most influential parameters. Moreover, the statistical analysis revealed varying degrees of correlation among different rock mass properties. While some properties demonstrated significant correlations suitable for modelling, others did not align well with any correlation model. The results highlight the need for a comprehensive approach to rock mass characterization, considering multiple factors beyond volumetric joint count. Geological complexities, including tectonic activity and weathering processes, may obscure direct correlations. These results emphasize the importance of empirical modelling and detailed site investigations for accurate assessment of rock mass quality and stability in the Himalaya.

Jun 10, 2024

By N. C. Gay

The quantitative evaluation of the performance of fill materials placed in gold mine stopes is achieved by (i) measurement of the in-situ load- displacement, or stress-strain, characteristics of the materials; (ii) an objective comparison between the observed fill performance and that predicted from suitable computer modelling techniques; and (iii) objectively comparing conditions in backfilled and conventional stopes. Considerable problems have been experienced with the development of sufficiently robust instrumentation which can be installed within filled pad- docks and give reliable information over a long period of time. However, at most mines where backfill performance is being monitored, it has been possible to correlate stress measurements within the filled paddocks with strain measurements adjacent to the paddocks. The resultant stress-strain curves agree relatively well with those determined in the laboratory. Measurements in the hangingwall strata of filled and unfilled stopes indicate that the placement of fill does reduce the amount of inelastic convergence due to bed separation. Moreover, in some stopes, the rate of convergence with respect to face advance does reduce to that of the theoretical elastic convergence. Quantification of changes in the conditions at the stope face due to placement of fill has proved difficult. Observations indicate that, provided the fill is placed close to the face (- 5 m), and adequate temporary face support is used, conditions in filled panels are superior. In addition, in filled panels the damage caused by a rockburst in the stope and, particularly, in gullies is generally much less than would be expected in an unfilled stope. To quantify these improvements, parameters such as stope height, face advance and the frequency of falls of ground are being monitored.

Jan 1, 1988

By H. White

The applicability of ground penetrating radar (GPR) in numerous qualitative applications has been demonstrated over the past five years in the South African mining industry. These applications include the delineation of faults and dykes, fracture mapping, delineation of shear zones, mapping of depth of weathering, and the delineation of contact between different rock types. The qualitative nature of the data collected using existing commercial GPR systems, often relying on expert interpretation, has however mitigated against the full scale routine application of GPR in the mining industry. The recent development of the RockRadar system by ISS International has, to a large extent, overcome these problems. The result is that quantitative rock-mass studies can now be performed with the RockRadar system.

Jan 1, 1996

By F. Essrich

A quantitative rockburst hazard assessment procedure was introduced on Elandsrand Gold Mine at the end of 1994. It is currently used to evaluate the seismicity-related risk in production areas on the mine. Six parameters related to seismicity, geology, mining layout, and production are rated and results are used as a planning tool on a regular basis. The applied assessment can be considered successful in that it promotes awareness of the seismic hazard and provides an opportunity to address seismicity-related mining problems. A comparison between high risk panels and those working areas with rockburst incidents showed that high hazard ratings reliably forecast the occurrence of larger events in the following month but they do not necessarily predict those working places with rockburst-related accidents. From this one may conclude that high levels of seismicity do not coincide with high rockburst rates.

Jan 1, 1997

By A. P. I. Popoola

Aluminium AA1200 was laser alloyed with a combination of nickel and titanium diboride using different weight ratios. Chemical reactions took place with the formation of different phases. The characterization of the alloyed surfaces was carried out by x-ray diffraction (XRD), optical and scanning electron microscopes. The alloyed surfaces are composed of the initial phase of Al-Ni dendrites and eutectics of TiB2/Al and TiB2/Ni distributed on the initial phase. Experimental results obtained showed that Al-Ni intermetallics brought about a significant increase in the hardness property of Al; however, these intermetallics are highly brittle and prone to fail by brittle fracture or stress corrosion cracking when put in service. The addition of TiB2 brought about a reduction in the formation of the seintermetallic phases. A microhardness increase of over 10 times the hardness of the substrate was achieved. Keywords Dendrites, intermetallics, metal composite, Nd: YAG laser.

Jan 1, 2011

By A. Kondratiev

A structurally-based viscosity model for fully liquid silicate slags has been developed and applied to the Al2O3-CaO-‘FeO’-SiO2system at metallic iron saturation. The model links the slag viscosity to the internal structure of melts through second nearest neighbour bonds concentrations taken from the quasi-chemical thermodynamic model. This viscosity model describes experimental data over the whole temperature and composition ranges within the Al2O3-CaO-‘FeO’-SiO2system at metallic iron saturation and can now be applied to other industrial slag systems.

Jan 1, 2004

By M. A. Kujoana

Following on the design of good mining layouts and regional support systems, and the implementation of sound strata control practices, stope support is the ultimate strategy to combat the hazards of rockfalls and rockbursts. The primary function of stope support in intermediate and deep level mines is to stabilize the rock mass immediately surrounding stoping excavations, that is, the zone of fractured rock which behaves in elastically around stopes. Support design is a process resulting in a support system which is both practical and meets or exceeds by a factor of safety the requirements for a particular geotechnical environment. The aim of this project was to design a support system, which accommodates the factors of rockfalls and rockbursts. The pack support unit must be easily handled, less costly and can be used in stopes without any significant convergence. The project tested the structural stability of packs to their expected deformation, in order to design a height to width ratio for stopes where little convergence is expected.

Jan 1, 2009

By A. Patri, D. S. Nimaje

Wireless sensor networks and wireless communication systems have become indispensable in underground mines. Wireless sensor networks are being used for better real-time data acquisition from ground monitoring devices, gas sensors, and mining equipment, whereas wireless communication systems are needed for locating and communicating with workers. Conventional methods like wireline communication have proved to be ineffective in the event of mine hazards such as roof falls, fires etc. Before implementation of any wireless system, the variable path loss indices for different workplaces should be determined. This helps in better signal reception and sensor node localization, and also improves the method by which miners carrying the wireless devices are tracked. This paper proposes a novel method for determining the parameters of a suitable radio propagation model, which is illustrated with the results of a practical experiment carried out in an underground coal mine in southern India. The path loss indices, along with other essential parameters for accurate localization, have been determined using the XBee modules and ZigBee protocol at 2.4 GHz frequency.

Jan 1, 2015

By G. Wendel

Uranium is a naturally occurring radioactive material in the earth?s crust. Geological processes have resulted in concentration of uranium into ore mined for its gold content in South Africa. This uranium is present in the form of discrete particles of uranium minerals, generally oxides, which are normally insoluble. Chemical and physical processes during gold mining and extraction, particularly when carried out in conjunction with uranium extraction and sulphuric acid manufacture, act on the uranium minerals and the radioactive decay products of uranium. This may result insignificant accumulations of radioactive materials in certain parts of the process. There are a number of naturally occurring radioactive materials in the earth?s crust, such as Uranium-235, Thorium-232, andPotassium-40. This paper focuses on Uranium-238, together with its decay products, and how they affect the gold mines. Water plays a significant role in the redistribution of radionuclides, both as a physical transport medium, and as a solvent in which chemical reactions take place.

Jan 1, 1998

By C Smit

SYNOPSIS A prototype collimated radiometric face scanner was tested in the Harmony Gold Mine. The results obtained during the pilot study indicate that in situ radiometric uranium assays are statistically indistinguishable from those obtained conventionally from channel chip samples. In addition, the study demonstrated that reasonably reliable gold estimates can be deduced from the radiometric measurements, by use of the ratio of gold to uranium within a mine. The instrumentation, calibration procedures, and background determination are described briefly.

Jan 1, 1985

By Y. H. Suh, H. C. Lee, D. S. Kim

A progressive karst formation and its influence upon engineered structures in the ‘phil-karst’ rock mass draw a tunnel engineer’s special attention to a long-term stability and the maintenance issues. Karst sinkholes of any size beneath the railway bed cause train wrecks or long interruptions in train traffic during rehabilitation work. The collapse of cave roof, called a ‘doline’, is in general connected to the cave by the gradual dissolving of the rock, developing into subsidence and sink-holes. The principal conclusions obtained from the field experiments are as follows: It is found that the development of karst cavity shows a relationship with a structural geological line and it is necessary to define the dominant directions of joint and geological layer (formation). The relation-ship between the water flow and joint direction can be used as an indicator of cavity presence in their direction. In addition the direction of in-situ stress can play a role in the development of karst cavities. A risk map of karst scenario is produced for the tunnel supporting systems with rock type classifications in water-soluble karstic rock mass. Eine fortschrittliche Karst-Formung und sein Einfluß auf angelegten Strukturen in der Phil-Karst-Felsenmasse wecken einem Tunnelingenieur eine besondere Aufmerksamkeit zu einer langfristigen Stabilität und der Wartungsausgaben auf. Karstensinkhöhlen in irgendeinen Größen unter dem Eisenbahnbett sind die Ursache der Zugeszerstörung oder der langen Unterbrechungen in Zugverkehr während Rehabilitationsarbeit. Der Zusammenbruch von Höhlendach, d.h. ein “doline”, ist im allgemeinen an die Höhle, die durch das allmähliche Auflösen des Felsen zu entstehen ist und sich in die Subsidence und Sinkhöhlen entwickeln, angeschlossen. Die Hauptschlüsse, die von Feldenprüfungen erhalten wurden, sind folgendermaßen: es wird gefunden, daß die Entwicklung von Karstenhöhlung eine Beziehung mit einer strukturellen geologischen Linie zeigt und es notwendig ist, die vorherrschenden Richtungen von Gelenk und geologischer Schicht (die Formung) zu definieren. Die Beziehung zwischen dem Wasserablauf und der gemeinschaftlichen Richtung kann als ein Anzeiger von Höhlungsanwesenheit in ihrer Richtung benutzt werden. Zusätzlich kann die Richtung von In-Situ-Spannung eine Rolle in der Entwicklung der Karstenhöhlungen spielen. Für das Tunnelunterstützungssystem, welches mit Felsentypenklassifizierungen in wasserlöslicher Karstic-Felsenmasse, ist eine Risikokarte von Karstenszenar hergestellt. Une formation progressive de karst et son influence sur les structures tracées dans la masse de roche "phil-karst" retiennent l'attention particulière des ingénieurs de tunnel aux problèmes de la stabilité à long terme et du maintien. Les creux de karst de toute la taille sous le chemin de fer causent les accidents de trains ou de longues interruptions pendant le travail de réhabilitaion. L'effondrement du plafond de caverne qui s'appelle "doline" s'est, en général, connecté à la caverne par dissolution progressive de la roche, en devenant l'affaissement et les creux. Les conclusions importantes venant des experimentations sur le terrain sont suivants: d'abord, le développement de la cavité de karst montre le rapport avec la ligne géologique de la structure et il est nécessaire de définir les directions dominantes du joint et la couche(formation) géologique. La relation entre l'écoulement de l'eau et la direction du joint peut être utilisé comme un indicateur de la présence de la cavité dans leur direction. De plus, la direction sur place peut contribuer au développement des cavités de karst. Le plan risqué de karst s'est produit pour le système d'appui du tunnel avec les classifications du type de roche dans la masse de roche karstique qui est soluble dans l'eau.

Jan 1, 2003

By S. A. Lorentz, Y. Xu, C. Theron

The failure of tailings storage facilities (TSFs) results in the discharge of significant quantities of hazardous waste material into the natural environment. Research studies relating to slope instability have identified physical mechanisms such as rainfall-induced erosion, liquefaction, and shear failure as the main triggers. The generation of transient pressure waves and the mobilization of pre-event water in the unsaturated zone have been found to trigger shallow landslides in natural hillslopes. In this paper we review these physical mechanisms, known as groundwater ridging (GWR) and the Lisse effect (LE), from other studies. Previous researchers have explained both these phenomena through field and laboratory observations, numerical modelling, as well as conceptual discussions. These case studies demonstrate the impact of rainfall characteristics on the generation of transient pressure waves that rapidly increase the phreatic surface and change pore water suction. Reference is also made to the influence and behaviour of physical porous medium characteristics on the establishment of a continuous water phase that facilitates the transmission of an induced pressure head. However, previous studies fail to recognize the possibility that the pressure increase in pre-event water through pore air propagation could cause slope instability in tailings dams. The authors suggest that the physical properties and hydraulic behaviour of unsaturated porous tailings media make it susceptible to GWR and the LE, resulting in the creation of a potential failure plane.

Feb 2, 2022

By Richard J. Robbins

Raise and shaft drilling, a continuing development RICHARD J. ROBBINS* (Visitor) Although the past decade has witnessed many improvements in large-diameter drilling machinery for the boring of raises, there is still room for improvement both in operational use and in the design of equipment. Some of the available machines are described and illustrated, and it is concluded that the possibilities of new systems and designs should continually be re-assessed since the factors that determine their feasibility, such as bore diameter, cutter costs, and penetration rates, are changing rapidly.