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By D. D. Howat, J. van der Colf

Slags of the system CaO-MgO-AI2O3-TiO2-SiO2at had been reduced in graphite crucibles for selected time Intervals were fully re-oxidized so that an assessment could be made of the rate and extent to which the titanium oxide had been reduced. The derived kinetic parameters were studied as functions of slag composition and temperature. The extent of reduction after selected Intervals of treatment could be correlated with the physical behaviour of the melt (in terms of viscosity and electrical resistivity).

Jan 1, 1979

By X. Chen, G. Wang, D. Wan

Computational fluid dynamics have been applied for detailed modelling of particle-bubble collisions. The most accurate approach in the previous work is using the point particle method to treat particles and bubbles. Nevertheless, the sizes of particles and bubbles are generally bigger than the Kolmogorov scale in the high turbulence of the flotation environment, which makes the point particle method inappropriate. This paper describes particle-resolved direct numerical simulation on the collisions between particles (denoted as heavy particles) and bubbles (denoted as light particles) in a homogeneous isotropic turbulent flow field, and a comparison with the point particle method.. A largescale stochastic forcing scheme was implemented within the mesoscopic multiple-relaxation-time LBM approach to maintain turbulence intensity at targetted levels. Both kinematic and dynamic collision kernels were evaluated to study the correlation of total collision events and turbulent kinetic energy (TKE) dissipation rate. The results show that collisions between particles increase with the TKE dissipation rate as radial relative velocities between particles increase with it. In the particle-resolved simulations, the dynamic collision kernels were found to not match with the kinematic collision kernels as in the point particle method. Quantitatively, they were approximately 4 to 10 times smaller than the corresponding dynamic collision kernels. Therefore, it is not reasonable to estimate the kinematic collision kernel in particle-resolved simulations as its rationales are not valid. However, the collision behaviour can still be accounted for by means of the dynamic collision kernel since it is obtained from the direct statistical analysis of the collision events. Keywords: Lattice Boltzmann Method; particle-resolved simulation; multiphase flow; collisions

Jan 1, 2020

By M. Saghaeian, R. Hejazi, L. Hosseini, M. V. Sheikhzadeh

HPGR equipment has been well proven to be energy-efficient in the first stage of grinding in iron ore beneficiation plants. Numerous advantages of utilising HPGR grinding prior to ball mill grinding, such as reducing the power consumption in a ball mill through generation of micro-cracks, has been thoroughly studied. Less attention has been paid to efficiency of the HPGR circuit rather than the downstream ball mill circuit. In this study the HPGR circuit has been optimised through feed size reduction by crushing, and feed iron content upgrading by dry cobbing. This optimisation leads to better operation of the HPGR, and a smaller product size which is expected to result in a lower wear rate of ball mill liners and balls. It is also expected that the top size of the ball mill balls be reduced. Additionally, by reducing the feed size of HPGR from 30 mm to 15 mm, it is possible to achieve similar K80 of HPGR product in lowered pressure, i.e. 2.5 N.mm-2 instead of 3.5 N.mm-2 which translates to ease of operation. Similarly in a given roll pressure, smaller feed sizes result in higher specific throughput of ~10% which means higher production capacities. The results also reveal that this optimisation increases the concentrate weight recovery by about 10%. It also results in slight increases in the Fe grade of the product iron concentrate. Keywords: HPGR, HPGR circuit optimisation, crushing prior to HPGR, dry cobbing prior to HPGR, ease of operation, concentrate grade optimisation, weight recovery optimisation

Jan 1, 2020

By F. H. Guise-Brown

Raise-boring experiences in the gold mines of the Anglo American Corporation Group by J. W. WILSON and P. C. GRAHAM Published in the Journal, October, 1972. Discussion by F. H. Guise-Brown., B.Sc. (Min. Eng.) (Member) INTRODUCTION Messrs J. W. Wilson and P. C. Graham are to be congratulated on an excellent paper containing several thought-provoking remarks. The concept of allocating a machine and equipment valued initially at some R300 000 on an experimental basis is courageous, and the results obtained could be of interest to the mining industry as a whole. The Gold Fields of S.A. Group approached this problem differently. In pioneering the start of this work in South African gold mines, they considered that expenditure of this magnitude would be warranted only if the proposition was viable right from the start. To this end, a Robbins R41 was purchased expressly to assist in the duplication of part of the No. 1 shaft system of the Doomfontein Gold Mine. Mr M. J. Koortsl has summed up the initial results of this work and given some preliminary costing, but inflation since that period has made these figures somewhat out of date.

Jan 10, 1972

By A. K. Haines

Hydrometalurgy, particularly leaching, is a highly topical subject and always generates great interest in the mineral industry. This was evident right from the start of the organization of the SAIMM Colloquium on Leaching, which was held at Mintek on the 8th and 9th November, 1988. The response to the cal for papers was so good that the Colloquium was extended to two days, instead of the usual one day.

Jan 1, 1988

By S. J. Thomas, P. A. Lilly

With support from the Australian mining industry and the Federal Government, three Australian universities are collaboratively developing flexible-format, web-based course content and delivery in rock mechanics for undergraduate mining engineering students. This paper describes the educational philosophy behind the development and summarises other salient features of the Program. Mit der Unterstuetzung von der austlalischer Bergbauindustrie und der Bundesregierung, drei austlalische Universtaeten in Zusammenarbeit entwickeln flexibel Netzgengruendet auf Lehrganginhalt und Lieferung in Felsgestein fuer Bergbaustudenten. Dieses Schreiben erlautert das Unterrichtsphilosophie hinter der Entwicklung und Zusammenfassung anderer Hauptpunkte von diesem Programm" Avec l'assistance de l'industrie miniere australienne et du gouvernement federal , 3 universites Australiennes collaborent a la mise en place d'un programme de mecanique des sols pour etudiants- ingenieurs en mines. Ce programme serait a la fois flexible et accessible par Internet. Ce document decrit la philosophie pedagogique de ce projet et en souligne les characteres importants.

Jan 1, 2003

By Y. Wang

Arsenic-bearing acidic effluent from hydrometallurgical processes contains many harmful metal ions and must be appropriately treated before discharge. In the present study, arsenic, copper, zinc, aluminum, and magnesium were co-precipitated by means of the Fenton reaction. The precipitates obtained under different conditions were investigated to determine their stability. The results indicate that pH value and hydrogen peroxide (H2O2) dosage have significant effects on the removal of various elements. Arsenic, copper, zinc, and aluminum (but not magnesium) can be removed at pH 5–6 and anH2O2/As mole ratio of 2 at ambient temperature. The precipitates were mainly amorphous and granular with particle size in the micrometre range. The arsenic concentration in leachate from the toxicity characteristic leaching test was 3.6 mg/L, which proves that the precipitates are effective in fixing arsenic.

Aug 3, 2023

By P. J. Bartlett, H. A. D. Kirsten

A two-dimensional numerical scheme for the simulation of the plastic stress-strain properties of rock, and the various components of rock reinforcement and shotcrete, was used to rigorously determine the characteristics of tunnel support under squeezing conditions. D-shaped tunnels varying in size from 2,8 to 6,5 m in height and width were considered. The four main mining stages in the BAS block cave on Premier Mine were simulated as alternative sets of field stresses. The rock reinforcement comprised 1,8 m long fully grouted rockbolts and 6,0 m long fully grouted cable anchors at various spacings, and of various tensile and bond strengths. Various thicknesses of shotcrete and footwall support configurations were also considered. It was found that shotcrete and rock reinforcement, owing to inherent differences in stiffness, do not function in unison. As monolithic application, shotcrete has an overriding avidity for the imposed loading and destructs itself unless of extraordinary thickness. Under squeezing conditions, it accordingly supports the excavation surface while the rock reinforcement contains on-going convergence. The loads in the various support components can be determined only by simulation of the shotcrete as a stress-relieved medium to represent its broken condition in the field. The loads in the rock reinforcement vary around a tunnel and are the largest in the sidewalls. The loads increase with an increase in tunnel dimensions, the increase in load in the sidewall due to an increase in height being larger than that in the hanging- and footwalls due to an increase in width. Depending on the strength of the rock, the loads in the rock reinforcement become prohibitively large beyond a certain size of tunnel. The reinforcement of footwall rock can be omitted without adversely affecting that in other walls, provided the tensile and bond strengths of the reinforcement are not limited. The resulting footwall heave may, however, result in undermining of the reinforcement in the adjoining walls. A relative depth of anchor of 1,37 provides adequate bond strength in the larger sizes of tunnel, whereas, in smaller tunnels, anchor length is determined by the allowable convergence. The lack of fun column grouting adversely affects the efficiency of rock reinforcement to a major extent. The loads in rock reinforcement are very sensitive to the strength of the rock. Owing to a lack in refinement and calculational rigour, empirical classification systems are an inappropriate means for the design of tunnel support in squeezing conditions and, as a result, grossly unclear-estimate the support requirements.

Jan 1, 1992

By D. Amariei, G. Bartolacci

Preconcentration of precious and base metal ore types is becoming more relevant with the discovery, the development and the operation of many lower grade deposits around the world. Ore preconcentration designates an operation consisting of sorting an ore to reduce the quantity of waste material sent to the concentrator. It can be seen as rejecting waste material as much as possible, without compromising the recovery, or as the recovery of as much valuable metal as possible into an optimum mass yield. Benefits of preconcentration are multiple: grinding energy savings, costs reduction, lower environmental footprint, extension of the reserves, etc. However, all of these benefits do not apply simultaneously and are not applicable to each ore type. Technologies employed for preconcentration are highly dependent on ore properties, especially on the particle size at which the gangue is liberated. Thus, from coarser to finer particle sizes, technologies such as screening, ore sorting, gravity separation (Dense Media Separation (DMS) and jigs) and coarse flotation could be used for the rejection of liberated gangue. The difficulty starts when a benchmark is needed to select a suitable technology, especially for low-grade gold deposits. This paper presents the challenges of comparing lab-scale technologies (DMS versus jig) for gold preconcentration. The experimental data will show to what extent comparing two lab-scale gravity technologies for gold preconcentration can be challenging. An attempt to evaluate the energy savings by assessing the hardness of the tailings after gravity separation will also be presented. Keywords: Challenges in gold preconcentration, gravity separation, jig, dense medium separation

Jan 1, 2020

By B. McFadzean, S. Pikinini, C. T. O’ Connor

Sperrylite (PtAs₂) comprises about 21% of the platinum group minerals (PGMs) in the Platreef ore and regularly reports to the tailings due to its poor floatability. Hence, improving its recovery will be of great economic value to the South African PGM industry. The reasons for its poor floatability are not yet clear. This paper seeks to understand the interactions occurring between PtAs₂ and common thiol collectors, viz. potassium normal butyl xanthate (PNBX), sodium normal dibutyl dithiophosphate (SNBDTP) and sodium normal mono butyl dithiocarbamate (SNBDTC). By understanding its interactions with these collectors, it is hypothesised that it will be possible to suggest ligands that may help improve the floatability of sperrylite. Mineral-collector interactions were studied by determining the molar energy of interaction using isothermal titration calorimetry and electrochemical techniques. The hydrophobicity of the mineral before and after adsorption of the collectors was determined by heat of immersion and its flotation response determined by microflotation tests. Microflotation tests using synthetic sperrylite at pH 9 showed low collectorless recovery of 34.8% and after adding the equivalent of one pseudo-monolayer of the PNBX collector, the recovery of 32.5% was obtained. Moreover, the addition of up to three pseudo-monolayers coverage of PNBX did not result in any increase in flotation recovery. A small recovery improvement was noted when synthetic plant water with the ionic strength of 0.0484 mol/L was used, but this did not hold for all collectors, with SNBDTP exhibiting higher recoveries in distilled water. Keywords: Sperrylite; flotation; recovery; adsorption energy; collectors; 2SPW (synthetic plant water)

Jan 1, 2020

By A. Yañez, J. Yianatos, P. Vallejos, R. Grau

This paper presents an evaluation of the effect that the mineral feed characteristics have on the metallurgical performance in an industrial flotation circuit. Variables such as mineralogy, particle size, solid content and mineral grade were evaluated using a flotation simulator, which was previously developed and validated using industrial data from different concentrators. The metallurgical performance was evaluated not only from the point of view of recovery and concentrate grade, but also by analysing less common variables such as froth carrying rate, froth and collection recovery, water recovery and others. Then, new data from the industrial flotation circuit was used to complement this analysis and evaluate the simulator predictability by comparing simulated and measured data. The results allowed for the quantification of the significant effect that mineralogy and particle size have on recovery and/or concentrate grade. Therefore, the grinding stage and flotation cells design become important factors to avoid a significant loss in metallurgical performance when feed mineral characteristics change in an industrial operation. In this context, an evaluation of cells design and arrangement should be performed to compensate the loss in recovery and concentrate grade in order to find an optimal operating condition. Keywords: Flotation circuits, mineral feed, modelling, particle size, liberation, mineralogy

Jan 1, 2020

By S. Mohanta, I. D. Behera, B. Sahoo

"Run-of-mine coal contains particles of different sizes with different specific gravities, and when this coal is crushed, the amount of material present in a particular density class changes. This alters the washability characteristics of the coal, which affects the quantity, quality, and separation efficiency of the gravity-based coal washing process. The degree of difficulty in washing a typical coal at a particular specific gravity depends mostly on the amount of material occurring within ±0.1 specific gravity range, which is known as ‘near-gravity material’ at that particular specific gravity of separation. In this paper, two numerical indices, namely ‘near-gravity material index’ and ‘index of washability’, are used to quantify the distribution of near-gravity material in different density classes and to evaluate the degree of difficulty involved in the washing process. The results of this preliminary investigation indicate the uniform distribution of near-gravity material in all density classes for finer size fractions, whereas for coarser size fractions more near-gravity material is present in the lower density classes, making the washing process more difficult at a lower specific gravity of separation. IntroductionThe prime objective of coal beneficiation is to remove physical impurities as effectively and economically as possible. The beneficiation process includes various operations on the asmined coal to make it more suitable for enduse application without destroying the physical identity of the coal. There are several coal beneficiation processes, but gravity-based separators remain the most efficient unit operation for removing the undesirable gangue material from run-of-mine coal. These separators exploit the difference in density between coal particles and gangue particles to effect a separation. The feed is introduced into an aqueous suspension of ultrafine magnetite with a particular density. The feed particles with a relative density less than that of the suspension (clean coal) float to the top surface of the suspension, whereas particles denser than the suspension density (gangue material) sink to the bottom. When the difference in density between the particle and the aqueous suspension is large, the separation is easy, but when this difference is less the separation becomes much more difficult since the settling velocity of the particles is very low. This lower settling velocity increases the probability that particles that should report to floats report to sinks, and vice versa, hence increasing the amount of misplaced material. Therefore, the degree of difficulty in beneficiating a typical coal at a particular specific gravity depends on the amount of material occurring within ±0.1 specific gravity range. This is known as ‘neargravity’ material, also termed ‘near-dense’ material, at that particular specific gravity of separation."

Jan 1, 2016

By H. Zhong, S. Wang, Q. Sun

The flotation performance of 2-(benzylthio)-acetohydroxamic acid (BTHA) to diaspore was first evaluated by micro-flotation tests. The adsorption mechanism was further investigated through adsorption experiments, molecular dynamics simulation, zeta potential and X-ray photoelectron spectroscopy (XPS). The results demonstrated that BTHA had a stronger ability to collect diaspore in comparison with another diaspore collector, benzohydroxamic acid (BHA), especially under the condition of weak alkalinity, the flotation recovery can reach 90%. The more negative interaction energy (ΔE) between BTHA and diaspore from molecular dynamics simulation results revealed that BTHA had an easier adsorption ablity onto diaspore than BHA, which matched with adsorption results. The zeta potential and XPS revealed that Al atoms might bond with -C(=O)NHOH by formation of Al-O bonds. Keywords: Diaspore, flotation; adsorption; 2-(benzylthio)-acetohydroxamic acid

Jan 1, 2020

By A. J. S. Benade, N. B. Strydom, W. H. Van Der Walt

The influence of two weeks of microclimate cooling on the state of heat acclimatization by N. B. STRYDOM, M.Sc., Ph.D. (Illinois) (Fellow), A. J. S. BENADE, M.Sc. (Potch.) (Visitor), and W. H. VAN DER WALT, B.Sc. (Potch.) (Visitor) Five volunteer Black subjects were acclimatized according to the climatic-room acclimatization procedure, and their states of heat acclimatization were determined by the usual heat-stress test. The subjects thereafter wore pre-frozen jackets in a somewhat higher environmental temperature (33,9/35,6 °C). stepping at the same rate as before for four hours a day for fourteen days. The heat-stress test was repeated and followed by a similar test at the higher environmental temperature. It was found that fourteen days of microclimate cooling in a very hot environment had no adverse effect on the degree of heat acclimatization. The sweat rates during microclimate cooling remained high, even though no sweating is possible beneath the pre-frozen ice-jacket. which indicates that there is an increase in sweat rate from the areas of exposed skin.

Jan 7, 1975

By A. Rahmanab, A. Torpy, M. I. Pownceby, M. N. Zaman, N. Haque, W. Bruckard, J. Tardio

Ilmenite is the principal feedstock for producing TiO2 - used in paints, plastics and paper and the production of Ti metal. The Brahmaputra River system in Bangladesh represents a potentially new source of ilmenite concentrated within sandbar placer deposits and the current study presents results from beneficiation and characterisation studies conducted on Brahmaputra River Fe-Ti oxides. Characteristic of fluvial systems, the ilmenite concentration is low (~0.5 wt-%), however extensive annual dredging for waterway navigation provides the economic impetus to recover saleable ilmenite. The Fe-Ti oxide suite derived from magnetic fractionation comprises homogeneous ilmenite, titanohematite and hematite, although many grains exhibit complex exsolution within the (Ilm-Hem)ss series. The textural variability results in difficulty generating a pure ilmenite feedstock with the bulk concentrate typically being low in TiO2, containing 31.0 wt-%TiO2 and 62.7 wt-% (Fe2O3). Results are interpreted via an analysis of the implications for producing a commercial-grade ilmenite concentrate suitable for TiO2 production. Keywords: Ilmenite, titanohematite, Fe-Ti oxide exsolution, TiO2 production

Jan 1, 2020

By G. Akdogan, S. M. Bradshaw, A. P. Van Wyk, T. Punt

Recycling has become an important part of the lithium-ion battery (LIB) life cycle due to the growing demand for energy storage in applications like electric vehicles and renewable energy. Recycling spent LIBs provides a secondary source for strategically scarce metals, like lithium and cobalt, helping to reduce the environmental impact of LIBs. Organic acids have been proven to be effective lixiviants with the benefit of reduced environmental impacts, amongst which citric acid has shown to exhibit similar extraction performance when compared to mineral acids. Leaching LCO and NMC batteries with 1.5M citric acid and 2 vol.% H2O2 at 95°C, 20 g/L for 20 minutes achieved 93% Al, 90% Co, 96% Li, 94% Mn and 94% Ni dissolution. The strong chelating property of citric acid affects the separation of the metals, providing unique extraction opportunities. The first extraction uses 12 vol.% D2EHPA at a pH of 2.5 and O/A ratio of 2 to separate 96.4% Mn and 100% Al from the PLS in two counter-current stages. Stripping the loaded organic with 1.25M citric acid at an A/O ratio of 3 allows for up to 91% stripping of the manganese in a single stage. The second extraction then separates 96.5% Li from the PLS in three counter-current stages using 20 vol.% D2EHPA at a pH 5.5 and O/A ratio of 5. The raffinate remaining after the second separation contains 48.4 wt.% Co and 50.3 wt.% Ni. Keywords: Hydrometallurgy, lithium-ion batteries, metal recycling, citric acid, solvent extraction

Jan 1, 2020

By T. Song, X. Wang, X. O. Xia, X. J. Luo, B. Chen

Interparticle breakage is the main crushing mode of an inertia cone crusher according to its working principle and feeding condition. In this paper the breakage behaviour of an inertia cone crusher is investigated, based on energy controlled compression combined with the vibration theory, rather than geometry controlled compression (form conditioned) which plays a major role in conventional eccentric cone crushers. The effect of feeding and operating conditions on breakage behaviour was described quantitatively from the perspective of energy consumption and product size distribution. The influence of feeding conditions, discharge size settings and vibration exciter speeds on the crushing process and product quality has been studied according to the results of laboratory crushing experiments. The results of the experiments show that the particle size of broken products becomes finer with the decrease of a discharge gap within the gap range selected by the experiment. The product size increases significantly when the gap approaches the upper limit of 6 mm. The variation of eccentric speed has a more prominent effect on reducing the product size compared with the change of discharge gap. The change in product size is not apparent when the eccentric speed rises to a certain level. The throughput of an inertia cone crusher is sensitive to the change of discharge gap, which increases linearly with the discharge gap and decreases with the eccentric speed. The change of feeding conditions has little influence on the crusher throughput. Keywords: Inertia cone crusher, interparticle breakage, energy consumption, product size distribution

Jan 1, 2020

By B. Moritz, W. Schubert, E. A. Button

ABSTRACT: Geological conditions associated with alpine environments in combination with high overburden in many tunnelling projects lead to squeezing behaviour. The main problems associated with such conditions include large deformations, overstressing of supports, and lack of face stability. In the past during Alpine tunnelling the problem of large displacements incompatible with rockbolt – shotcrete support systems have been solved by leaving gaps in the lining to accommodate excessive deformations. In the late nineties, yielding elements have been developed, which are integrated into the lining. The paper deals with the basic concept, the design and the application of that system, which has been successfully used in several Alpine tunnels. ZUSAMMENFASSUNG: Die geologischen Verhältnisse in den Alpen führen bei großer Überlagerung häufig zu starken Deformationen während des Baues von Tunneln. Die großen Verformungen führen in vielen Fällen zu einer Überbeanspruchung des Ausbaues und Problemen mit der Ortsbruststabilität. Früher ist man dem Problem der Unverträglichkeit des Ausbaues mit den hohen Dehnungen durch Freilassen von Deformationschlitzen im Spritzbeton begegnet. Vor etwa 10 Jahren wurden duktile Stahlelemente entwickelt, welche in die Spritzbetonschale integriert werden. Der Beitrag beschäftigt sich mit dem Konzept, der Planung und der Ausführung. RÉSUMÉ: Les conditions géologiques dans les Alpes conduisent fréquemment lors d'un grand recouvrement à des déformations fortes pendant la construction des tunnels. Les grandes déformations conduisent dans beaucoup de cas à une surtension du revêtement et à des problèmes avec la stabilité de front de taille. On a fait face plus tôt au problème de l'incompatibilité du revêtement avec les extensions élevées par libérer des rainures dans le béton projeté. Il y a environ 10 ans, des éléments sidérurgiques ductiles qui sont intégrés dans le béton projeté ont été développés. La contribution s'occupe de concept, de planification et de mise en oeuvre.

Jan 1, 2003

By J. Hadjigeorgiou, G. Knox

There is a considerable wealth of information on the behaviour of rockbolts under axial loading conditions both in situ and under controlled laboratory conditions. However, there is comparably less data on the behaviour of rockbolts in shear. Several authors have contributed to the understanding of the behaviour of conventional rockbolts’ performance under shear loading. Much of this data have been gathered through experimental programmes conducted on sections of the rockbolt. Considering the continuous coupling between the rockbolt and borehole interface, the approach is justified. Due to the design premise of energy-absorbing rockbolts with discrete couplings, full scale testing is required to quantify the behaviour of the rockbolts. This paper reviews published results obtained from two testing facilities, which are the SINTEF rockbolt pull test rig in Trondheim, Norway and the Epiroc Combinations Shear and Tensile test rig in Johannesburg, South Africa, both capable of conducting full scale testing of rockbolts. Based on this high-quality database it was possible to identify three distinct responses of rockbolts in shear. The behaviour under load is controlled by the presence or absence of an encapsulation medium (resin/cement grout), the reinforcement mechanism, and whether the rockbolt is continuously or discretely captured. As a reference the results are compared to the performance in shear of conventional grouted rockbolts.

Nov 24, 2025

By L. Linzer, J. Oelofse, T. Rangasamy

Extraction of isolated blocks of ground with elevated levels of stress and/or seismicity is a common occurrence in South African gold mines. Isolated blocks of ground that are divorced from the main orebody and are bound by complex, dip and strike parallel, non-persistent geological structures dominate the Klerksdorp gold fields. No quantifiable methods exist to assess the risk associated with mining these and other classes of remnants. A case history, from a gold mine that planned to extract three remnant blocks hosted in a large complex fault system, is used to illustrate the decision making process based on a combination of underground observations, numerical and seismic techniques. Simple risk estimation matrices were developed and used to estimate remnant-mining risk and finally to quantify the decision on which of the three remnant blocks could be extracted at the lowest possible geo-mechanical risk. Il est courant dans les mines aurifères sud-africaines d’extraire des blocs de terrain isolés qui possèdent des niveaux élevés de contraintes et/ou sismicité. Les régions aurifères de Klerksdorp sont dominées par des blocs de terrain isolés qui sont séparés du gisement principal et qui sont retenus par des structures géologiques non continues, à parallèle de pendage et direction, et complexes. Il n’existe pas de méthodes quantifiables pour évaluer le risque associé à l’extraction de ce genre et autres genres de résidus. Une observation de cas, celle d’une mine d’or qui avait l’intention d’extraire trois blocs de résidus qui se trouvaient dans un grand système complexe de faille, est utilisée pour illustrer le processus décisionnel basé sur une combinaison d’observations souterraines, et de techniques numériques et sismiques. Des matrices simples d’estimation de risque furent développées et utilisées pour estimer le risque lié à l’extraction des résidus et finalement pour quantifier la décision sur lequel des trois blocs de résidus pouvait être exploité au moindre risque géo-mécanique. Die Extraktion isolierter Gesteinsblöcke mit erhöhtem Spannugsniveau oder Seismizität ist in südafrikanischen Goldminen üblich. Isolierte Gesteinsblöcke, die von der Haupterzader getrennt und durch komplexe, parallele abfallende und horizontale nicht persistent geologische Strukturen gebunden sind, beherrschen das Klerksdorp Goldfeld. Es gibt keine quantifizierbare Methoden die das Risiko welches mit dem Abbau dieser und anderer Klassen verbunden ist beschreiben. Eine Fallstudie einer Goldmine, welche die Extraktion von drei in einem großem komplexen Verwerfungssystem eingelagerten Einschlußblöcken plante, wird verwendet um den Entscheidungsprozeß zu illustrieren, der auf einer Kombination von Untertag Beobachtungen und numerischen und seismischen Techniken basiert. Einfache Gefahreinschätzungsmatrizen wurden entwickelt und angewendet um das Abbaurestrisiko abzuschätzen und letztendlich die Entscheidung zu quantifizieren, welcher der drei Einschlußblöcke unter dem niedrigst möglichen geo-mechanischen Risiko extrahiert werden konnte .

Jan 1, 2003