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By H. Willenberg, J. S. Coggan

ABSTRACT: Although individually both continuum and discontinuum numerical analyses provide useful means to analyze rock slope stability problems, complex failures typically involve mechanisms related to both existing discontinuities (i.e. discontinuum) and deformation and brittle fracture of intact rock (i.e. continuum). One such example is the 1991 Randa rockslide in the southwestern Swiss Alps, where failure involved several complex mechanisms, which require the consideration of progressive failure and rock mass strength degradation. This paper presents results from a series of hybrid finite-/discrete-element models directed towards the explicit modelling of brittle fracturing in natural rock slopes, enabling the modelling of progressive failure, from initiation, through to the development of catastrophic failure, transport and deposition. RÉSUMÉ: Si les modélisations numériques de type continu ou discontinu fournissent des outils utiles pour l’analyse de problèmes de stabilité de pentes rocheuses, elles montrent de sérieuses limitations lorsque des mécanismes de rupture complexes impliquent des processus liés autant aux discontinuités préexistantes qu’au développement progressif de nouvelles fractures. Ceci se retrouve typiquement dans l’exemple de l’éboulement de 1991 à Randa dans les Alpes suisses du sud-ouest, où la rupture a impliqué plusieurs mécanismes complexes nécessitant la prise en considération de la fracturation progressive ainsi que de la dégradation de la résistance des masses rocheuses. Cet article présente des résultats provisoires d'une série de modèles hybrides orientés vers la modélisation explicite de la fracturation de pentes naturelles, permettant la modélisation de fractures progressive de leur initiation jusqu’à leur développement, leur rupture catastrophique, leur transport et leur déposition. ZUSAMMENFASSUNG: Obwohl numerische Kontinuum- und Diskontinuum-Berechnungen einzeln nützliche Ergebnisse zur Stabilitätsanalyse von Felshängen liefern, sind komplexe Felsrutschungen typischerweise mit Mechanismen verbunden, die sowohl durch bestehende Trennflächen (s.a. Diskontinuum-Ansatz) als auch durch die Deformation und das Versagen intakter Felsbereiche (s.a. Kontinuum-Ansatz) bedingt werden. Ein Beispiel für einen solchen Sachverhalt ist der Bergsturz von Randa 1991 im südwestlichen Teil der Schweizer Alpen, bei dem die Rutschung mehrere komplexe Mechanismen umfasste, so dass “progressive failure” und Verminderung der Gebirgsfestigkeit in Betracht gezogen werden müssen. Dieser Artikel beschreibt vorläufige Ergebnisse einer Reihe von hybriden Modellrechnungen (Finite-/Diskrete-Elemente). Diese haben zum Ziel, explizit das bruchhafte Versagen natürlicher Felshänge zu modellieren, wobei das progressives Versagen im ganzen modelliert wird, von der Anfangsphase über die Entwicklung zum katastrophalen Versagen und den Transport und die Ablagerung der Rutschmassen.

Jan 1, 2003

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By S. K. Murphy, S. M. Spottiswoode, A. M. Milev, D. Geyser

A portable, stand-alone instrument especially designed for recording strong ground motion was used in this study to create a large database of peak particle velocities measured underground. A total number of 39 sites located in stopes mining Carbon Leader and Ventersdorp Contact Reefs were investigated. Peak particle velocities whith values up to 3 m/s were recorded at some sites. The data recorded on the skin of the excavations were compared to the data recorded by the mine seismic networks to determine the site response. The maximum site response was obtained for source radii of between 5 m and 30 m and events locating within 200 m of the site. The extreme values of peak particle velocities were obtained in cases were the face-area lay within the source radius. Un instrument portable unique spécifiquement conçu pour enregistrer les mouvements dynamiques des terrains, a été utilisé dans cette étude pour créer une base de données importante sur la vélocité maximum des particules, mesurée en souterrain. Un nombre total de 39 sites situés dans les excavations exploitant les récifs appelés ‘Carbon Leader et Ventersdorp Contact Reefs’, a été investigué. Une vélocité maximale avec des valeurs allant jusqu’ à 3 m/s a été enregistrée sur certains sites. Les données enregistrées sur le bord de l’excavation ont été comparées aux données enregistrées par les réseaux séismiques de la mine pour déterminer la réponse du site. La réponse maximum du site a été obtenue pour des sources de rayons entre 5 m et 30 m et des évènements situés dans les 200 m du site. Les valeurs extrêmes de vélocités maximales ont été obtenues pour les cas où la zone de face se trouve à l’intérieur du rayon de la source. Ein mobiles, alleinstehendes Instrument, speziell entworfen um starke Formationsbewegungen aufzuzeichnen, wurde in dieser Studie verwendet um eine große Datenbank von Partikelspitzengeschwindigkeiten, die Untertage gemessen wurden, aufzuzeichnen. Eine Gesamtanzahl von 39 Aufstellungsorten in den Schichtabbauorten vom Carbon Leader und Ventersdorp Contact Reef wurden untersucht. Partikelspitzengeschwindigkeiten mit Werten bis zu 3 m/s wurden an einigen Standorten aufgezeichnet Die an der Oberfläche des Grubenraumes aufgezeichneten Daten wurden mit jenen Daten verglichen, die vom seismischen Netzwerk der Grube notiert wurden, um die örtliche Reaktion des Standortes zu bestimmen. Die maximale Standortreaktion wurde für Ursprungsradien von zwischen 5 m und 30 m erhalten und Ereignissen die sich innerhalb von 200 m vom Standort befanden. Die extremen Werte der Partikelhöchstgeschwindigkeiten wurdenin jenen Fällen erreicht wo sich der Abbaubereich innerhalb des Ursprungsradiuses befand.

Jan 1, 2003

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements set out on pages 269 to 276. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to report on these financial statements. We have conducted our audit in accordance with generally accepted auditing standards. These standards require that we plan and perform the audit to obtain reasonable assurance that, in all material respects, fair presentation is achieved in the financial statements. The audit included an evaluation of the appropriateness of the accounting policies, an examination, on a test basis, of evidence that supports the amounts and disclosures included in the financial statements, an assessment of the reasonableness of significant estimates, and a consideration of the appropriateness of the overall financial statement presentation. We consider that our auditing procedures were appropriate in the circumstances to enable us to express our opinion presented here. In our opinion these financial statements fairly present the financial position of the Institute at 30th June, 1999, and the results of its operations for the year then ended in conformity with generally accepted accounting practice.

Jan 1, 1999

By X. J. Lyu, Q. Liu, M. J. Lian, X. Q. Cao, X. F. You, B. O. Erdenekhuyag, H. Y. Zang

The slag-tailings based artificial reef concrete (ARC) is made of CaO-CaSO4 activated granulated blast furnace slag (GBFS) as cementitious material and deslimed gold ore tailings as aggregate. In order to investigate the potential application of the material as ARC, the strength development, hydration characteristics and application performance were investigated under different preparation conditions. Results indicated that using seawater as the mixing water can effectively promote the hydration of slag and generate a large amount of hydration products such as ettringite, CSH gel, hydrotalcite and Friedel ’s salt in the early curing period and so render the material with good early compressive strength. Seawater curing can also accelerate the hydration reaction in the early stage of hydration. The hydration reaction of slag and the compressive strength of ARC can be effectively promoted by increasing the specific surface area of slag. The 28-day compressive strength of the slag-tailings based ARC prepared with 30-50% CaO-CaSO4 activated slag and 50-70% tailings can reach to 19.88-42.87 MPa. Also, the material has a low surface pH value, good resistance to chloride ion penetration, and sulfate corrosion. Keywords: Artificial reef concrete, granulated blast furnace slag, deslimed gold ore tailings, compressive strength, hydration characteristics

Jan 1, 2020

By H. Saroglou

Anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). Testing was used to establish the anisotropic behaviour of selected gneissic rocks. The effect of anisotropy on various mechanical properties (strength, deformation) and dynamic properties (wave velocity) was examined. The rock samples were also tested at successively higher confining pressures in order to evaluate the effect of anisotropic behaviour at high overburden pressures.

Jan 1, 2004

The validity of a steady state assumption made by Adams and Nicol (1986) in the modelling of the elution of gold from activated carbon was investigated. It is shown that the accuracy of the steady state approximation is dependent, not only on the magnitudes of the solution flow rate and reactor volume, but also on the lumped elution rate constant. Under the experimental conditions used by Adams and Nicol (1986) the steady state assumption was inaccurate. This could be circumvented in this instance by applying a rigorous general model which accounts for unsteady state behaviour in the solution and in the activated carbon to the experimental data.

Jan 1, 1997

By R. P. H. Willis

For technology transfer to be successful a process, from research to full scale application, has to be followed. This paper describes such a process and how it is applied in practice. Some of the ?do?s? and ?don?ts? are highlighted. Recommendations are made on how to communicate existing knowledge and to ensure that a framework exists to effectively plan future projects with final technology transfer objectives firmly in place. The Impact Ripper System is used as a case study to illustrate lessons learned. Key words: Technology transfer, implementation

Jan 1, 2002

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements set out on pages 239 to 245. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to report on these financial statements. We have conducted our audit in accordance with generally accepted auditing standards. These standards require that we plan and perform the audit to obtain reasonable assurance that, in all material respects, fair presentation is achieved in the financial statements. The audit included an evaluation of the appropriateness of the accounting policies, an examination, on a test basis, of evidence that supports the amounts and disclosures included in the financial statements, an assessment of the reasonableness of significant estimates, and a consideration of the appropriateness of the overall financial statement presentation. We consider that our auditing procedures were appropriate in the circumstances to enable us to express our opinion presented here. In our opinion these financial statements fairly present the financial position of the Institute at30th June, 1997, and the results of its operations for the year then ended in conformity with generally accepted accounting practice.

Jan 1, 1997

By D. François-Bongarçon

When it comes to sampling theory, a bad sampler is a bad sampler, no matter what, and a sampler is either bad or good. It also is of critical economic importance to tell and understand the difference, especially in a metallurgical plant. In this paper, the grand principles of Sampling Theory are first recalled, then the most popular types of sample cutters for plants are critically reviewed. It is concluded that the industry has a lot of progresses to make in that direction, although improvements usually pay for themselves very quickly.

Jan 1, 2002

By M. G. Wimberger

The Merensky Reef zone, as developed on Impala Platinum?s Rustenburg Operations, displays a gradational mineralized zone, with grades decreasing from the Merensky Pegmatoid Unit into the footwall and hanging wall. A system of identifying a manageable method of defining the mining cut is introduced, termed the grade profile attenuation cut-off grade. Although horizontal grade selectivity is not applied in the mining of the Merensky Reef zone, low extraction of the orebody, due to manageable and non-manageable factors, can contribute to a reduction in revenue, even losses, due to fixed cost contributions in the mining and beneficiation of the ore. A model is proposed that integrates all variables affecting the revenue of the mining operation, including the grade profile attenuation cut-off grade, the extraction factors, commodity prices and exchange rates, utilizing numerical simulation techniques in a PC-based environment. A breakeven extraction factor for a specific cut-off grade is delivered for a range of market conditions. The breakeven extraction factor is a useful guide when designing mining layouts in structurally complex and low metal content areas. Incorporating distribution functions for individual commodity prices and exchange rates into the model provides mineral resource managers with a risk profile for individual mining areas. Shaft areas have varying grade profiles and each area should have individual models run, to prevent generalizations being made about acceptable risk levels on mining areas.

Jan 1, 2004

Instability in rockpasses at deep levels often initiates as a result of stress induced fracturing of the rock on the walls of the pass. This may then progress to a stage at which the geological structure of the rock mass becomes dominant and permits large joint-defined blocks and slabs to become unstable. In this paper, a technique is described in which jointing parameters and their variabilities?orientations, spacings and lengths?are taken into account in estimating the extent of failure that may develop around a typical unsupported deep level gold mine rockpass. The results of this prediction are compared with the results obtained from a review of pass performance in the gold mining industry.

Jan 1, 2005

By J. S. C. Joubert

The Koidu Kimberlite Project is situated in the Kono District of Sierra Leone, approximately 330 km east of the capital city, Freetown. The mining lease area is 4 km2 and comprises 2 kimberlite pipes, 4 dyke zones and a number of blows off the dykes. Koidu Holdings established on the property and began dewatering and the removal of silt from the existing 30 m excavation of the No.1 Pipe in 2003. While the original planning for the pipes included conventional open pit operations, mitigating factors such as the proximity of the town, the presence of houses close to the perimeter of the pipe, the size of the pipe and the planned open pit depth with relevant stripping ratios, as well as uncertainties on the grades in respect of an underground operation, lent itself to the vertical pit concept. The vertical pit was established using an A-frame headgear for the hoisting arrangement, with sidewall support comprising a combination of 20 m and 40 m long cable anchors, rock bolts, wire mesh and pneumatically applied concrete. The pit reached steady state production in January 2007 and produced some 26,000 tonnes of head feed per month until August 2007 when mining reached a depth of 74 m below the pit collar (approximately 126 m below surface). Mining was suspended following a sidewall failure that disrupted operations. Now that the grades in No.1 Pipe have been validated, focus has been switched to an underground operation taking account of both No. 1 Pipe and No. 2 Pipe. While the mining costs for the vertical pit have been higher than for a conventional open pit, the concept did circumvent the social implications, the issue of grade consistency and diamond value at depth, as well as providing the time frame to carry out a full underground mining study.

Jan 1, 2008

The typical reactions which the reductants undergo during ferroalloy production are reviewed, and identified as reaction with CO2 and with SiO, and dissolution in metal. Available reactivity tests for these three reactions are reviewed. It is proposed that it is worthwhile considering dissolution kinetics as a reactivity parameter. Greater crystallinity of the reductant decreases CO2 and SiO reactivity, but increases dissolution rates.

Jan 1, 2002

By M. K. Elmouttie, G. V. Poropat

The analysis of structure using joint set statistics is well known. Other data such as the position of discontinuities and the contacts between rock mass units cannot be easily incorporated in simple statistical analysis based on orientation alone. Algorithms to model the structure of rock slopes using measurements of the orientation and position of discontinuities are being developed by CSIRO Exploration and Mining. These algorithms provide a capability to model the structure of a rock slope and estimate the likelihood of the formation of hazardous blocks in existing or proposed rock slopes and identification of the location and size of these blocks. The algorithms provide the basis of structural modelling to identify potential failure mechanisms in rock slopes.

Jan 1, 2006

By Marco Barla, Mariacristina Bonini, Giovanni Barla

ABSTRACT: The paper describes the characterisation studies of Tectonised Clay Shales at laboratory and in situ scale. The interest relates to tunnelling under squeezing and swelling conditions, in Italy, along the Apennines. The results of monitoring during full face excavation are presented in conjunction with numerical modelling. RESUME: Cet article présente la caractérisation, à l'échelle du laboratoire et in situ, des Argiles Chaotiques. L'attention est portée sur le creusement, dans ces milieux gonflants, des tunnels, dans les zones montagneuses des Appennini, en Italie. Enfin, on présentera les résultats de la modélisation numérique et la comparaison de ces derniers avec les mesures effectuées in situ. KURZFASSUNG: Die Arbeit beschreibt die Charakterisierungsstudien von tektonisierten Schiefertonen, sowohl im Labor als auch vor Ort. Das Interesse gilt dem Tunnelbau unter Quetsch- und Schwellbedingungen in Italien entlang der Apenninen. Die Überwachungsergebnisse des ganzflächigen Ausbruchs werden mit numerischen Modellen präsentiert.

Jan 1, 2003

This is an abstract from Environmental Service and Technology (Vol 32 No 20 1998) which will be o finterest to South African Mining and Metallurgical Scientists, involved in chromium mining and Metallurgical processing. Maybe the scourge of our dams and reservoirs?the water hyacinth can be put to good use! The novel technology of phytoremediation embraces plant accumulation processes for the cleanup of toxic heavy metals and organic chemicals. Several plant species have been identified that are excellent hyperaccumulators of a number of heavy metals, e.g., Brassica juncea (Indian mustard) and Thlaspe caerulescens (Alpine pennycress). Other speciesincluding Myriophyllum brasiliense(Parrot?s feather), Salixsp. (willow), and Popullussp. (poplar) have also demonstrated phytoremediating abilities.

Jan 1, 1999

By M. F. Handley

Sequential grid mining has been employed as the primary mining strategy at the AngloGold West Wits Elandsrand Mine since the inception of stoping operations from the sub-vertical shaft system in 1988. Little has been published on sequential grid mining as a mining strategy since, and the purpose of this paper is to describe sequential grid mining, its history, its implementation at Elandsrand, and the outcome to date. The results obtained using sequential grid mining have been evaluated from seismic data, productivity statistics, and rock related accident statistics. Comparisons with neighbouring mines namely Western Deep Levels and Deelkraal, have been made to substantiate the improved conditions observed at Elandsrand, and to compare sequential grid mining directly with longwall mining in similar conditions and at similar depths. Sequential grid mMining is shown to be cost-effective, more flexible, and safer than long wall mining in similar conditions, at least on the Ventersdorp Contact Reef in the western part of the Carletonville Goldfield. More work is necessary to establish it as the favoured mining strategy at depths exceeding 3000 metres, and for reefs other than the Ventersdorp Contact Reef.

Jan 1, 2000

By J. L. van Niekerk, J. Gunaselvam

This study investigates the use of appropriate seating systems for the control of whole-body vibration exposure in vehicles used in the SA mining industry. Six suspension seats were tested with six test subjects to determine the most suitable seat for an articulated dump truck based on the EM1 requirement in ISO 7096 (2000) standards. Transmissibility functions were measured in the laboratory using the newly commissioned Dynamic Seat Testing Facility with two excitation levels of 1m/s2 and 2 m/s2 r.m.s. in the 0.5 - 30 Hz frequency range. SEAT values were calculated for two input spectrums, the EM1 input spectrum specified as in ISO 7096:2000 and measured road vibration data measured on a typical articulated dump truck. The averaged SEAT value calculations indicated that not one of the seats will qualify as an ISO 7096 (2000) suspension seat but that it is possible to select a seat that will significantly reduce the vibration the driver will be exposed to.

Jan 1, 2003

The Gordonsville Operation of Pasminco US Inc. along with the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of germanium and gallium. This paper describes the joint testing and engineering program that culminated in this successful process. 1. Introduction The Pasminco US Inc. (PAS), Gordonsville Operation, has been producing zinc concentrate continuously since 1975. Within the zinc concentrate, several byproduct elements were found to be significantly concentrated including gallium and germanium. The gallium and germanium replace zinc and other metals within the crystal lattice structure of the zinc mineral (sphalerite) and are concentrated in the same manner as the zinc mineral. This concentrate is then sent to the Pasminco Clarksville Zinc Refinery for further processing. Within the hydrometallurgical zinc-processing plant at Clarksville, a residue is formed that contains a majority of the impurities that would otherwise contaminate or hinder the zinc process. Approximately 5,000 tons of residue is formed annually containing approximately 0.80% gallium and 0.60% germanium along with significant quantities of iron, zinc, silica, and lead. Pasminco currently sells this residue for the germanium value. Until recently, no revenue for the gallium was obtained from the sale of the residue.

Jan 1, 2008