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By C A. Locke, J Cassidy, J L. Mauk

The Waihi-Waitekauri region hosts numerous low-sulfidation epithermal deposits that both outcrop and occur at depth. Zones of intense hydrothermal alteration enclose the Au-Ag bearing quartz vein deposits. Hydrothermal alteration includes the destruction of magnetite by hydrothermal fluids, pervasive silicification adjacent to quartz lodes and potassium enrichment due to adularia and illite deposition. High-resolution airborne magnetic and radiometric, and new gravity data delineate distinct geophysical anomalies associated with hydrothermal alteration and mineralisation. Five magnetically quiet zones occur in the region varying in size from 3 to 34 km2 and in geometry from circular to irregular zones. These zones represent the near-surface extent of strong to intense hydrothermal alteration associated with fossil geothermal systems. All epithermal deposits in the region occur in magnetically quiet zones. Over 120 new gravity stations together with existing data across the Waihi district have defined a positive Bouguer gravity anomaly coincident with the magnetically quiet zone. Eastern and western gradients of 50 gu/km bound the anomaly that contains two flat gravity highs west and east of the Waihi deposit. Strong potassium signatures in airborne radiometric data correlate with outcropping zones of alteration and are consistent with the presence of adularia and illite minerals. Hydrothermally altered zones are represented by areas of low Th/K ratios as a result of low thorium concentrations in andesite and elevated potassium levels in altered zones.

Jan 1, 2003

By Jose Bengoa

Low metal prices and environmental restrictions are always a challenge for copper smelters operation and its productivity. Thus, in order to reduce production costs and control gas emissions, improvements of the Teniente Converter (CT) operation were made at 110 Smelter Plant of Southern Peru Copper Co" 110, Peru, and the main objective was to increase its capacity for smelting copper concentrates without affecting normal operation, The present work eorresponds to a recent study conducted during the normal industrial operation of the Teniente Converter in this plant and, it shows the effect of increasing air oxygen enrichment from 28 to 34% on its productivity. The results show an increasing of concentrate smelting rate from 800 to 1370 tpd and hence a notorious improving in copper production, and practically no effect on the refractory consumption. The increment of the concentrate throughput, increases also the SO2 concentration and the sulfuric acid production, showing the effort done by this operation in order to accomplish the environmental Peruvian regulation,

Jan 1, 2003

The design of solvent extraction plants has been generally based on the assumption of steady operating conditions in both the settler and the mixer units. However, recent experience in both large and small plants has shown this not to be the case. Mixer transients include start up aqueous locking and partial phase separation in secondary mixers, which both lead to reduced plant capacity or overflow of upstream mixers. Analysis of the hydraulic pressure profiles has generated new design methods to eliminate the effects of the partial or complete phase separation. Changes to the method of specification and selection of primary and secondary mixers have been made to eliminate the onset of partial separation during operation. The observation of settler operation has shown that it is also a dynamic process, even under "steady-state" conditions. Four transient phenomena have been identified that lead to internal circulating flows, poor disengagement of fine secondary haze and erratic and high entrainment levels in the discharges. A, first approximation analysis has shown that there are significant pressure differentials within settlers, and these change along the length and with the phase separation rates. A technique to control the effects of these transients was developed that allows plant performance to be improved beyond "standard" expectations. The design and selection of the settler internals is described. Key words: Solvent extraction, Mixer-settlers, Phase separation, Entrainment, Mixer transients

Jan 1, 2003

By A B. Richards

Time window analysis that limits the explosive mass fired within a specified time window (commonly eight milliseconds) has been used for many years in blast design by explosives engineers. Despite several warnings in the past that this technique has limited practical or scientific basis and, in many cases, does not effectively control vibration, almost every textbook and blasting manual refers to time window charge mass limits as a primary vibration control technique. It has become entrenched in some blast vibration management plans, despite being inappropriate for the particular situation. With the flexible initiation timing available with electronic detonation almost a practical reality, and the 8 ms constraints in-built into the signal tube initiation system thereby lifted, it is timely to review the significance of the 8 ms time window in controlling blast vibration. This paper re-visits the original research that led to the development of the 8 ms criteria and the non-supportive conclusion of the original researcher. Because airblast was not measured, the 8 ms time window was never intended to be applicable for airblast control. Examples of blast designs are given in this paper that comply with the 8 ms time window limit that result in substantially increased air and ground vibration, together with examples of blast design that does not satisfy time window considerations, which results in reduced air and ground vibration. Techniques that identify wavefront reinforcement, due to the combined effect of drilling pattern and delay sequence, can assist explosives engineers to avoid high blast vibration situations that result from the inappropriate application of time window techniques and other adverse delay combinations.

Jan 1, 2003

By Y. Mitani, M. Zhang, M. Takeda, T. Esaki

Despite their inadequacy, assumptions of isotropy and homogeneity are often applied to the analyses of in situ permeability tests. In this paper, we exam the effects of anisotropy and heterogeneity on Pressure Pulse Test (PPT) and Constant Head Injection Test (CHIT) by means of numerical approaches. Some new findings that offer practical considerations in properly interpreting in-situ permeability tests are presented. Malgré leur manque de précision inhérente, les assomptions d'anisotropie et d'hétérogénéité sont souvent utilisées lors de test de perméabilité in situ. Dans cette étude, nous examinons les effets de l'anisotropie et de l'hétérogénéité sur le test par pression pulsée et le test à injection à charge hydraulique constante par le biais de la simulation numérique. Des nouveaux résultats permettant une interprétation pratique et claire des test de perméabilité in-situ sont présentés. Trotz ihrer inhärenten Ungeeignetheit werden häufig Annahmen über Isotropie und Homogenität auf Analysen von in-situ Permeabilitätstests angewendet. In diesem Papier untersuchen wir die Effekte von Anisotropie und Heterogenität auf Durck-Impuls-Test (PPT) und Konstant-Kopf-Einspritztest (CHIT) mit numerischen Ansätzen. Einige neue Befunde, die zu praktischen Erwägungen zur richtigen Interpretation von in-situ Permeabilitätstests führen, werden vorgestellt.

Jan 1, 2003

By J. K. Mudge, T. Allen, P. B. Johnson

Approximately 6 years ago, Newmont Mining Corporation (Newmont) initiated reclamation/closure at its’ Hollister operation in Nevada. Reclamation/closure challenges existed at three primary areas within the operation. One the open pits had a small, low pH lake. The primary waste rock dump had a collection system for seepage of low pH solution. The heap leach had a typical inventory of process solution. In each of these three areas water quality and water quantity challenges existed. Reclamation/closure techniques were employed that utilized run-on controls, re-sloping, capping/topsoil placement, pit backfilling and vegetation for water quantity control. Water quality controls included installation of passive, anaerobic systems. These mechanisms have effectively limited water volumes that require treatment and effectively treated the water to meet standards.

Jan 1, 2003

By Ragnhild Aune

In fire refining of copper, the affinities of various impurity elements on dissolved oxygen is of great significance. Further, in the design of oxygen probes in liquid copper, the influence of solute interactions on the activity of oxygen need to be considered in order to evaluate the oxygen concentration in molten copper. The present paper presents a series of measurements of the activities of oxygen in liquid Cu-M-o alloys (where M stands for Mn, Zn, As, Se or Te) carried out by the present group employing the solid electrolyte galvanic cell technique. Extreme care was taken to control the oxygen potentials in the inert gas atmosphere, and to keep the oxygen levels very low in the molten metal. The oxygen content was determined by analysis of the samples taken out from the melt. The results obtained showed that Mn has a strong negative influence on the activity coefficient of oxygen in liquid copper. A similar, but less prominent effect was observed in the case of Zn. Arsenic had no influence on the activity of oxygen in Cu (liq.). Se and Te had slight negative effect on oxygen activities in copper at XO > 10-5, while at lower oxygen levels the interaction coefficients were found to be positive. The results obtained were compared with empirical models for the calculation of interaction coefficients available in literature.

Jan 1, 2003

By K. H. Ho

This paper describes a simplified numerical model which is used to study the skull formation of liquid metal on a rapidly rotating disc in centrifugal atomisation. The skull formation is one of the problems limiting the wide use of centrifugal atomisation. The enlarging skull on the atomising disc reduces the yield of metal powder produced and produces a resistance to the centrifugal force which worsens the quality of the powder. It is costly and often difficult to study the flow behaviour by experiments due to the complex heat transfer and phase transformation during the processing. Computer modelling is therefore a powerful tool for mechanistic understanding of centrifugal atomisation. This paper investigates the flow pattern of the melt on the rotating disc as a function of initial temperature, melt flow rate and disc rotation speed as well as the physical properties of the melt, such as density, surface tension and viscosity using the commercial package Flow-3D. Keywords: Solidification, Rotating disk, Centrifugal Atomization

Jan 1, 2003

By A. V. Tarasov

In order to improve technical, economic and environmental performance of hydrometallurgical processing of intermediate products containing copper and nickel, the Gintsvetmet Institute and the IMET Institute of the Russian Academy of Sciences have conducted studies into the efficiency of the use of alternating current of industrial frequency on processes applied for hydrochemical leaching of various copper- and nickel-containing materials. It has been found that: 1.Imposition of alternating current over the process of leaching of softly reduced nickel oxide with recycled copper sulfate solutions resulted in an increase by 20 to 30% of the rate of the copper cementation process and reduced by 20% its activation energy. At the same time, the recoveries of nickel, cobalt and iron to the leach solution increased up to 82.2%, 78.5% and 57.1%, respectively, and that of copper to the cement precipitate up to 74%. Optimal process conditions have been identified with respect to the current density, electrode material, copper concentration in solutions and the process temperature. 2.In the process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides, the grain size, the phase form of sulfides, the solution composition (H2SO4, Cl?, Cu2+, Fe3+)and the current amperage had an effect on the nickel recovery to the solution, which reached 90%, while the degree of copper transfer to solution did not exceed 20%. The process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides with an addition of Cl? made it possible to selectively recover nickel into the leach solution along with concentrating copper in the leach residue. 3.When subjecting samples of commercial-grade magnetic fractions of converter matte to sulfuric acid leaching, the imposition of electric current, the concentrations of sulfuric acid and chloride ion in the solution and the duration of the reaction process had an effect on the process. The nickel recovery was 85% and that of cobalt and iron was 95% and the recoveries reached 97.5%, 98.3% and 99.8% as a result of repeated treatment of the primary residue under similar process conditions. Up to 75% of copper, 75% of sulfur and 99.0-99.5% of palladium was concentrated in the solid reach residues. The experimental data obtained indicates that the use of AC for hydroelectrochemical sulfuric acid leaching for separation of copper- and nickel-containing intermediate products has favorable prospects.

Jan 1, 2003

By Jim Truskoski, Alain Bouchard, Andy Kerr, Germain Labonté, Jim Barrett

"Improving mill grade recovery relationships is always good business. INCO’s Clarabelle Mill has just undergone a $16 million process upgrade that was designed to improve nickel recovery by 2%. The “Mill Redesign Project” was completed on time, under budget and delivered the promised improvement in recoveries.This paper describes the methodology of the Mill Redesign Team, details of the process improvements and the critical success factors that helped the team deliver on its promises.With a payback of under one year, the Mill Redesign Project will play a key role in ensuring a competitive edge as INCO embarks on its second century of operation.INTRODUCTIONIt is not uncommon in milling operations to encounter a crisis. That is the point when the process does not behave as expected and fails to respond to the increasingly desperate efforts of the metallurgists and operators. Flowsheet and process changes are attempted and abandoned. With luck, one or more of the changes achieves some mitigation of the original problem or more usually, the original cause of the problem disappears. Regardless, the metallurgist can sit back and bask in the apparent success of his or her endeavours.Less common is when a problem is carefully diagnosed, a team put together to explore all avenues and recommend a path of action that is implemented on time, on budget and immediately delivers on the promises which are sustained over time. This is one such story. It is the story of the Mill Redesign Project at INCO’s Clarabelle Mill in Copper Cliff, Ontario.BACKGROUNDThe Clarabelle Mill was built in 1971 on the southern rim of the Sudbury basin. At that time it was one of four mills operated by INCO in the Sudbury area. During the 1970’s, 80’s and 90’s, the need for increased process efficiency, higher levels of sulphur rejection to tails and the concurrent development of high capacity mills and flotation cells, resulted in the consolidation of INCO’s Sudbury area milling operations into a single, expanded facility at Clarabelle."

Jan 1, 2003

By S Robson, T G. Blenkinsop, S C. Dominy

Golden Pig mine is in the central part of the Southern Cross greenstone belt within the Archaean Yilgarn craton. The mine has produced approximately 2.5 Mt of ore at 5.7 g/t Au to yield approximately 450 000 oz. The majority of gold mineralisation is hosted within extensively deformed and quartz-veined BIFÆs. In addition to the BIF-hosted mineralisation, an increasingly important part of the resource lies in the Taurus Lode, which is a N-NNW-trending amphibolite facies shear zone. The Taurus Lode lies within a continuous shear-zone that has a moderate to steeply WSW dipping foliation, and a mineral lineation of biotite, amphibole and pyrrhotite plunging consistently 10¦ S. Drive faces, subperpendicular to the foliation and lineation, consistently show evidence for syn-mineralisation reverse shear. Exposures parallel to the mineral lineation and perpendicular to the foliation reveal both sinistral and dextral asymmetries. These characteristics suggest that the vorticity axis of the Taurus Shear Zone is parallel to the mineral lineation, and that the simple shear sense is reverse. This geometry can arise when there is a major component of flattening across the shear zone, which may be due to interference between two adjacent granite domes. The BIF-hosted lodes plunge consistently 15¦ NNW coincident with the intersection of the axial planar cleavage of the regional folds and the Taurus Shear Zone. However, where the penetrative shear characteristics control the orientation and geometry of the mineralisation, oreshoots plunge SSW, parallel to the stretching and mineral lineations within the shear. The SSW plunge of strike extensive and laterally confined high-grade, economic ore shoots within the Taurus shear is fundamental to defining the economic mineralisation within this lode. Identifying the zones of maximum continuity and establishing the optimal position for future development will maximise ore extraction.

Jan 1, 2003

The reported values of the standard reduction potentials of the Au(NH3)2+/Au(0) and Au(S2O3)23-/Au(0) couples are reviewed to emphasise the experimental difficulties associated with the measurement of reliable values for these quantities. The standard reduction potential for Ag(I)/Ag(0) in ammonia and thiosulphate solutions measured at ionic strength 0.1 and 25oCis used to predict the following relevant stability constants () for gold complexes based on the linear free energy correlations: Au(NH3)2+2 = 1013, Au(S2O3)23-2 = 1024 and Au(NH3)43+4 = 1033. The equilibrium constant ( 10-11) for the reaction Au(S2O3)23- + 2NH3 = Au(NH3)2+ + 2S2O32- based on these stability constants is in reasonable agreement with the measured value (10-9) based on potentiometric and spectroscopic data when excess ammonia was added to a solution of Na3Au(S2O3)2. This also indicates that the stability constant of Au(NH3)2+ is 9 to11 orders of magnitude less than that of Au(S2O3)23-. Relevant species distribution and Eh-pH diagrams based on the revised data are presented.

Jan 1, 2003

By I. V. Lunkin, E. B. Muhamedzhanov, A. B. Begalinov, B. R. Rakishev

Almost all the ore deposits of ferrous, non-ferrous and rare metals of Kazakstan, are exploiting by the open-cast method, are the complex-structural, multi-component ones. Their rational working requires precise organization of extracting works. In this connection it is necessary to set up the best intercommunications between drilling-blasting, excavating-loading and transport works. This requires the stable functioning of the quarry for dispatch of ore raw material of required quality with minimum of corresponding expenses. For this purpose, proceeding from the quarry’s ore output and the assumed parameters of the exploitation system, the first problem about rational arrangement of excavating-loading equipment in extracting faces is solved. By solving the problem the model with dynamic, adapting properties had been used. It was solved numerically by the method of statistical tests. By setting up the necessary link between type-sizes of excavating-loading and transport equipment, the minimum prime cost of loading and transportation of 1 ton of mining mass from the face to the receiving station was adopted as the criterion of optimality. Depending on the type of excavating-loading equipment, the efficiency function may be different. By using wheel loaders, their displacement between the faces is possible, therefore, the efficiency function of the problem may include expenses for their displacement. By using excavators like power shovel, the problem’s restrictions must exclude its displacement between the faces. The efficiency function consists of minimum expenses for loading, proceeding from set of volumes of extraction from the faces, satisfying required quality. The volumes of extraction from the faces, satisfying required quality of ore in output stream, are determined by the method of statistical tests. Sample range is given, proceeding from the restrictions for maximum productivity of the excavating-loading equipment. Volumes of extraction, not satisfying required quality, are cut off. The efficiency function meaning is then determined and minimized. Keywords: Excavating-loading equipment, its placing in extracting faces, optimal load-carrying capacity, specific expenses for loading and transportation of mining mass.

Jan 1, 2003

"In the UK, Ireland, and Western Europe, the mineral resource and reserve reporting standard is the PERC Code, developed and maintained by the Pan-European Reserves and Resources Reporting Committee, which is a standing committee set up under the auspices of a number of professional organisations which include the Institute of Materials, Minerals and Mining (loM3), the Geological Society of London (GSL), the European Federation of Geologists (EFG) and the Institute of Geologists of Ireland (IGI) to develop a Pan-European reporting code. The PERC Code supercedes the old IMMM Reporting Code 2001 and is recognised by the UK securities regulators and stock exchanges.""FOREWORD1 The Pan European Reserves and Resources Reporting Committee (PERC) Code for Reporting of Exploration Results, Mineral Resources and Mineral Reserves (further referred to as 'the Code') sets out minimum standards, recommendations and guidelines for Public Reporting of Exploration Results, Mineral Resources and Mineral Reserves in the United Kingdom, Ireland and Europe. The history of development of this code is summarised in Appendix 4.This 2008 edition supersedes all previous editions of The Reporting Code and the IMM Reporting Code.INTRODUCTION2 In this edition of the PERC Code, important terms and their definitions are highlighted in bold text. The guidelines are placed after the respective Code clauses using indented italics. They are intended to provide assistance and guidance to users in interpreting the application of the clauses in the Code. The same indented italics typeface formatting has been applied to Table 1, and to Appendices 1 and 2 which form part of the Guidelines.3 The Code has been adopted by the Institute of Materials, Minerals and Mining (loM3), the Geological Society of London (GSL), the European Federation of Geologists (EFG) and the Institute of Geologists of Ireland (IGI), and is therefore binding on their individual members.Appendix 1 contains a table of generic terms and their equivalents, designed to avoid unnecessary duplication or ambiguity in the textAppendix 2 provides Rules of Conduct for Mineral Resource and Mineral Reserve estimators that should be considered in addition to the Codes of Ethics normally applying to members of professional institutions."

Jan 1, 2003

By V. L. Zajakowski, J. D. Gargulak

The current political climate has forced multinational cement manufacturers to consider technology that minimizes GO, emissions. Along with this environmental issue, individual manufacturing facilities are under constant pressure to increase productivity and lower costs. The use of processing or functional additions can help address these difficult demands by maximizing the extender content in blended cements. Recently, cement standards have been modified such that additions can be employed to improve quality. By using these "cement performance enhancers," the cement manufacturer can maximize extender content of cement thus optimizing plant economics, while meeting local quality standards and minimizing greenhouse gas emissions.

Jan 1, 2003

By Y Potvin

Risk assessment in the mining industry is currently a topic of great interest with risk methodologies being increasingly applied beyond the traditional areas of finance and feasibility to analyses of risks due to various physical hazards including chemical, electrical, mechanical and geotechnical sources. The application of risk analysis and evaluation techniques to the management of personnel safety is being promoted by both industry and regulators but, particularly for geotechnical hazards, often there are inadequate databases for a meaningful quantitative calculation of risk. In Western Australia over the decade 1987 - 1997, the annual fatality rate for underground mining has averaged at approximately 1.3 in 1000 employees with rockfalls/rockbursts accounting for over half of these deaths (Prevention of Mining Fatalities Taskforce, 1997). Recent improvements have been made since this time, perhaps halving the annual fatality rate, mainly due to industry improving ground control measures and implementing various recommendations from the Prevention of Mining Fatalities Taskforce (1997). However there still remain a large number of unknowns when trying to address the complex area of geotechnical risk in mining. Risk calculations require information about the source of the hazard, the people or assets exposed to the hazard (the æelements at riskÆ) and the effects on these vulnerable elements if the hazard actually occurs (the potential consequences). To date, little information has been available on the exposure of mining personnel and equipment to underground hazards other than occupational safety studies on chemicals, heat, dust, etc. This paper concentrates on underground geotechnical risks and presents a data collection and rating system for the exposure of both the underground workforce and equipment to rockfalls and rockbursts. The methodology considers exposure times, personnel protection levels and hazard proximities to give exposure ratings for the major underground mining activities and hence rate different locations within a mine. This exposure methodology is then applied to the workforce and production/ development cycles in an actual WA underground mine, creating a snapshot map of differing levels of personnel exposure across the mine.

Jan 1, 2003

By Hiroyuki Matsuura

The effects of P20S or Na20 addition on the reaction rate of CO2 dissociation on the surface of FexO-base molten oxides was investigated at 1773K by isotope exchange methodl-6_ The rate constant decreased with increasing P20S content of molten oxides and the residual rate constant was observed at high P20S content On the other hand, the rate constant increased with increasing Na2O content for FexO-SiO2 melts. The rate constant was evaluated by the composition of oxides and the rate controlling step of CO2 dissociation was discussed.

Jan 1, 2003

By E. Swart

The purpose of this paper is to provide an overview of the current legislative framework for mine closure within South Africa as well as the new requirements in terms of the Mineral and Petroleum Resources Development Act, 2002. The roles and responsibilities of Government, the mining industry and other stakeholders and confusion caused are also highlighted.

Jan 1, 2003

By T. Proietti, L. Mongiovì, L. Simeoni

Reliable estimates of the kinematic characteristics of movements are obtained by using a statistical model SSM. This model represents a useful tool for the management of alert and alarm systems. L'élaboration des données du déplacement médian d'un modèle statistique SSM opportun fournit des estimations fiables des caractéristiques cinématiques du mouvement. Le modèle peut être ainsi utilisé pour la gestion des systèmes d'alarme. Die Bearbeitung von Bewegungsdaten anhand eines geeigneten statistischen Modell SSM ergibt vertrauliche Abschätzungen der kinematischen Eigenschaften der Bewegung. Das Modell kann also für das Management von Alarmsystemen verwendet werden.

Jan 1, 2003

By Y. H. Hatzor

ABSTRACT: A fully dynamic, two dimensional, stability analysis of a highly discontinuous rock slope is demonstrated in this paper. The studied rock slope is the upper terrace of King Herod’s Palace in Masada, situated on the western margins of the seismically active Dead Sea Rift. The dynamic deformation of the slope is calculated using a fully dynamic version of DDA in which time dependent acceleration is used as input. The analytically determined failure modes of critical keyblocks in the jointed rock slope are clearly predicted by DDA at the end of the dynamic calculation. It is found however that for realistic displacement estimates some amount of energy dissipation must be introduced into the otherwise fully elastic, un-damped, DDA formulation. Comparison of predicted damage with actual slope performance over historic time span window of 2000 years allows us to conclude that introduction of 2% kinetic damping should suffice for realistic damage predictions. This conclusion is in agreement with recent results of Tsesarsky, Hatzor and Sitar (2002) who compared displacements of a single block on an inclined plane subjected to dynamic loading obtained by DDA and by shaking table experiments. Using dynamic DDA it is shown that introduction of a simple rock bolting pattern completely stabilizes the slope. RÉSUMÉ : On présente dans cet article une analyse bidimensionnelle complète de la stabilité d’une pente rocheuse très fracturée. La pente rocheuse étudiée est la terrasse supérieure du Palais du roi Hérode à Massada, située sur la rive Ouest du Rift sismiquement actif de la Mer Morte. La pente est constituée de blocs de dolomite raide présentant une stratification sub-horizontale et des joints sub-verticaux. La déformation dynamique de la pente est calculée en utilisant une version entièrement dynamique de l’Analyse de Déformation Discontinue (DDA) où l’accélération dépendant du temps est utilisée comme donnée. Les modes de rupture déterminés analytiquement des blocs clés dans la pente rocheuse fracturée sont clairement prévus par l’approche DDA à la fin du calcul dynamique. On trouve cependant, que pour obtenir des estimations réalistes du déplacement, il faut introduire un facteur de dissipation énergétique sans lequel la formulation DDA serait totalement élastique et sans amortissement. En comparant l’endommagement prévu avec les caractéristiques de la pente sur une période historique de 2000 ans, nous pouvons conclure que l’introduction d’un amortissement cinématique de 2% suffit pour obtenir de prévisions réalistes. Cette conclusion est conforme aux résultats récents de Tsesarsky, Hatzor and Sitar (2002) qui ont comparé les déplacements d’un bloc isolé sur un plan incliné sous chargement dynamique obtenus avec l’analyse DDA et à partir d’essais sur table vibrante. ZUSAMMENFASSUNG: En utilisant une modélisation DDA dynamique on montre que l’introduction d’un système simple de boulonnage stabilise la pente.In dieser Veroeffentlichung wird eine vollstaendig dynamische, zweidimensionale Stabilitaetsanalyse eines hoechst diskontinuierlichen Steinhangs dargestellt. Der untersuchte Hang ist die obere Terrasse des Herodespalastes in Massada, welche in den westlichen Randgebieten des seismisch aktiven Toten Meer Grabens liegt.Die dynamische Deformation des Berghangs wird mit Hilfe einer vollstaendig dynamischen DDA-Version berechnet, in welcher als Input die zeitabhaengige Beschleunigung eingegeben wird. Die analytisch bestimmten Versagensarten kritischer Schluesselbloecke in diesem zerkluefteten Steinhang werden durch Anwendung von DDA am Ende der dynamischen Berechnung klar vorausgesagt. Es zeigt sich jedoch, dass fuer realistische Dislozierungs-Abschaetzungen ein gewisses Mass an Energieverlust in der sonst vollstaendig elastischen, ungedaempften DDA-Fassung einbezogen werden muss. Der Vergleich des vorhergesagten Schadens mit dem aktuellen Verhalten des Berghangs waehrend einer historischen Zeitspanne von 2000 Jahren erlaubt uns zu schliessen, dass ein Zusatz von 2% kinetischer Daempfung fuer eine realistische Vorhersage des Schadens ausreichen sollte. Diese Schlussfolgerung steht im Einvernehmen mit neuen Ergebnissen von Tsesarsky, Hatzor und Sitar (2002), welche die Dislozierung eines einzelnen Blocks auf geneigter Ebene unter dynamischer Belastung – unter Anwendung von DDA und “shaking table”-Versuchen – verglichen. Mit Hilfe der dynamischen DDA wird gezeigt, dass der Steinhang durch Anwendung einer einfachen Steinschraubenstruktur vollkommen stabilisiert werden kann.

Jan 1, 2003