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By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

By M. L. Smith, G. Karunatillake

Lead-zinc production at MIM, Mount Isa includes three mines, a lead concentrator, zinc filter plant and lead refinery. Lead production is vertically integrated with lead-silver bullion shipped from Australia to London for refining. Zinc is sold as a concentrate. All three mines have reached varying states of maturity mining a multitude of orebodies having significant variation in grades and metallurgical recovery for three metals. Based on current levels of measured resources, the remaining project life is at least ten years. The objective is to schedule production over the life of all three mines so as to maximize the present value of the complex. Additional scheduling complexity arises out of the implementation of long-term schedules, capital expansion projects for both mining and processing, the presence of substantial inferred reserves and interactions with MIM copper production. A large-scale, time-dynamic, life-of-complex Mixed Integer Program (MIP) production schedule was formulated to optimize lead/zinc cash flow based on a detailed life of project production scheduling study. The requirements for such a study are detailed herein. The operational feasibility of the MIP solution is compared against a non-optimal approach to strategic life-of-mine scheduling. The strategic planning emphasis placed on the MIP is compared to the implementation of a life-of-mine schedules at Mount Isa using spreadsheets and other popular commercial mine schedulers.

Jan 1, 2003

By D. Mjonono, S. T. L. Harrison, N. Maliela, A. Kotsiopoulos

The improvement of coal waste management practices, through the co-disposal of waste rock with sulphur-lean fine waste tailings (<1 mm in size), can potentially mitigate acid rock drainage (ARD). On exposure to natural oxidants, the sulphide compounds present in mine discards generate acidity, creating a cyclical oxidation process intensified by iron and sulphur oxidising microorganisms. To inhibit the emergence of ARD, a stable mine dump may be constructed that is structurally stable and incompressible through the mixing of complementary waste fractions that reduce voids and access to acid generating surfaces. However, large voids manifest as scale increases, due to decreased particle interlock, enabling the unrestricted access of oxidants leading to the early onset of ARD. To avoid this phenomenon, enhanced packing approaches based on geochemical and geotechnical characterisation tests were employed to improve bed stability. These were assessed for long-term prevention using aggressive oxidative conditions typical of heap leaching applications. Favourable results were obtained for both blended and multi-layered systems. However, long-term success was most notable in beds with alternating layers of waste rock and fine waste tailings with co-mingled systems being more susceptible to failure. Deconstructed co-disposed beds provided valuable insight into post-leach structural transformations. Results indicated that relative changes in initial coarse discards to fine waste ratios were most notable in blended systems. Mass fractions of the comparatively more mobile fine wastes increased axially down these test columns that ultimately resulted in increased contact of oxidants with the acid generating waste discards. Conversely, more consistent ratios were observed in multi-layered configurations. In these systems, near impervious hardpans were created by the moisture retaining fine tailings, forming stable structures with neutralising barriers sustained at each alternating layer. Consistent with post-leach geotechnical characteristics, static acid-base accounting tests showed that the uppermost sections of blended systems were more susceptible to oxidation due to structural failure with fine particles migration, while the more stable multi-layered configuration evenly maintained neutralising capacity. Keywords: Acid rock drainage (ARD), bed structure, mobility of fine particles

Jan 1, 2020

By T. Struminski

The paper is aimed to assess the possibilities of usage of pyrometers and thermal cameras to study ventilation and environmental conditions in underground mines. Surface and underground thermovision tests were carried out in the Rudna mine and included channels and diffusers of some selected fan stations, shaft crest closures, engines of central fans and their instrumentation. The thermovision underground tests in the Rudna mine consisted of ventilation barriers, underground fans, temperature of rocks, ventilation machines, parts of belt-conveyors and electric machinery.

Jan 1, 2003

By J. Witley

"Narrow tabular platinum group element deposits in the Bushveld Complex of South Africa are typically evaluated by diamond core drilling from surface. Several short deflections are drilled from each mother hole in order to obtain multiple intersections at a close spacing (less than 1 m). Examination of the intersections from deflection drilling revealed the importance of these deflections in understanding the representivity of the borehole, obtaining an estimate of the nugget effect, and mitigating the undesirable effect of the high grade variability at the ultra-short range that is a characteristic of these deposits. The use of deflections in estimation was investigated by means of a number of techniques and scenarios in order to find the most appropriate way to use them in an estimate. A significantly improved level of confidence was gained from using multiple close-spaced intersections rather than a single borehole intersection. IntroductionThe Upper Group 2 chromitite layer (UG2 or UG2 Reef) is known for its remarkable geological continuity, being traced almost uninterrupted for tens of kilometres. However, what is often less well emphasized is the high variability in platinum group element (PGE) grade and thickness (and therefore PGE content) and internal reef stratigraphy over very short distances (several metres or even tens of centimetres).This paper examines the application of short drill-hole deflections in evaluating UG2 PGE mineral resources at Marikana in the western Bushveld Complex of South Africa."

Jan 1, 2017

By A. N. Clay

In recent times, there has been criticism of the minerals industry over the lack of quantifiable boundaries between inferred, indicated, and Measured resources. A recent initiative through the United Nations aims to try to converge the mineral resource classification systems. Since the oil and gas industry uses a probabilistic approach to defining reserve boundaries, it is appropriate to introduce a similar statistical methodology for minerals. The Venmyn Variance Tower has been developed based upon traditional statistics to utilize historical and ongoing information in order to quantify variance of geological and chemical parameters and the boundaries and logic for quantitative mineral resource classification. It is proposed that a less than 50% variance from the mean of all sample parameters is required to achieve the classification threshold to define an inferred Resource whereas between 20-10% is needed for an indicated Resource and less than 10% variance from the mean is needed to declare a Measured Resource. These limits are similar to those used by the oil and gas industry, and it is suggested that these thresholds be adopted as an industry standard to ensure consistent quantitative reporting. While this process is intended to use statistics of an orebody to provide quantifiable and defendable boundaries, it cannot be carried out unless the geology of the mineral deposit is understood and the borehole samples can be categorized into appropriate populations for which the statistics are valid. This means that competent geologists are always required to work with and understand the implications of the Variance Tower results. This paper is intended to form the basis of a series of publications that establish a process to take mineral projects along a quantifiable and logical development path. Hence, no specific field example of the practical application of this process is given here.

Jan 1, 2012

By E. Isokangas

A mine is essentially a series of operations, including drilling and blasting, crushing, milling, flotation, and leaching, that are interconnected and therefore interrelated, with the performance of one operation affecting the performance of another. Optimizing each stage separately without considering the whole system often causes potential economic benefits and energy savings to be missed. However, the PIO methodology is a thorough approach which considers these individual process activities within the context of the whole process. The basic principle is to optimize the process as a whole, rather than each process step in isolation from the others. Metso?s Process Technology and Innovation (PTI) group offers a global consulting service for the mining and construction industries. A significant amount of this consulting work involves process integration and optimization (PIO) studies. When conducting a PIO study, every aspect of the process is considered. In addition to drilling and blasting, transportation, handling and storage, crushing, screening, grinding, flotation, separation, and recovery, other aspects including equipment utilization and energy consumption and even greenhouse gas emissions are also included if necessary. In a PIO project, it is very important to understand what type of material is being processed at any point in time. That is, which domain or domains is the material part of? This is necessary in order to observe the effect of different ore sources (and the blending of sources) on concentrator performance. Linking the ore from the pit to the concentrator required the development of an ore tracking system. As a result, PTI developed a radio-frequency based material tracking system called SmartTag?. This system allows tracking of ore from its source through blasting, run-of-mine (ROM) pads, crushers, intermediate stockpiles, and finally into the concentrator. Using the SmartTag? system, definitive correlations can be made between the performance of the plant and the plant feed characteristics, including the domain from which the feed ore originated. Since its commercialization in 2007, SmartTag? has been used in the majority of PTI?s consulting projects and several permanent systems have been installed worldwide1. Successful applications of the SmartTag? system have encouraged development to allow the system to be used in a wider variety of plants, in particular plants with finer crushing and screening stages. This paper describes how the SmartTag? system is being utilized by PTI and the benefits being gained by its use in PIO projects, as well as presenting some case studies.

Jan 1, 2012

By M. R. Samis

The great variability of mineral and energy prices has motivated some governments to incorporate a windfall profits tax into their mineral taxation regimes. Windfall profits taxes are a means for governments to capture additional mineral revenue when mineral prices are considered higher than some historic level. Governments need to be aware of the effects of such contingent taxes on the exploration, development and operating decisions of mining companies. Mining companies need to be able to calculate the full impact of windfall profits taxes on the economics of their projects. This paper examines the valuation of a multi-phase copper-gold project in the presence of a windfall profits tax. Real options Monte Carlo simulation is used to characterise the different exposures of the mine owner and of the government to the risky cash flow streams that they receive from the project. The results highlight that Monte Carlo simulation paired with the real option valuation method is able to account appropriately for the differing risk exposures, while the traditional discounted cash flow valuation model is not. Our key conclusion for governments and mining companies is that the impact of contingent tax and royalty terms can and should be assessed using advanced valuation techniques, and the results used to improve contract designs under the constraint of actual and perceived fiscal system stability.

Jan 1, 2007

By J J. Pretorius, G M. Hoffmann

Utilisation of lower-grade (<60 per cent Fe) resources, not utilised in the current products, is crucial to ensure optimal resource utilisation and maintaining/improving future profit margins by reclassifying low-grade material to ore. The purpose of the Sishen Expansion Project (?SEP?) is therefore to investigate the technical and financial viability of producing up to an additional 10 Mtpa of new products at Sishen from material currently classified as low-grade materials. Jigging technology has progressed to a point where Sishen?s 50 to 60 per cent Fe run of mine (?ROM?) material, once considered as waste, can be beneficiated to produce a saleable 64 per cent Fe product. This has been confirmed through appropriate beneficiation testwork. Consequently, Sishen can now produce saleable product from material not currently included in the resource definition, increasing the resource base of the mine significantly and ensuring higher resource utilisation. Mine Planning utilised the geological models to produce detail planning schedules, reflecting the current and SEP plants separately, optimised to comply with product specifications of both the current and SEP plants and to confirm the viability of the low-grade resources identified as SEP feed material. The SEP products specifications have been derived by optimally matching iron ore market requirements with the revised resource base. A 64.0 per cent Fe lump product and a 63.5 per cent Fe fine product are the optimal SEP products. The SEP plant will be able to produce 10Mtpa at an average yield of 60 per cent and a lump to fine ratio of 62 to 38. The plant consists of five major sections namely crushing, material preparation, beneficiation, final product handling and quality control services. Maximum integration with the current Sishen plant was considered. Kumba currently has an agreement with Transnet to rail up to 23.5 Mtpa through the Sishen Saldanha Iron Ore Export Channel (?IOEC?). Transnet and Sishen Iron Ore Company have signed a Definitive Agreement that deals with the expansion of IOEC?s capacity, which increases Kumba?s entitlement from 23.5Mtpa to 35.0Mtpa. The detailed enviro-legal impact assessments for the SEP indicated that the project has low enviro-legal risk as a result of it being a brownfields project incorporated into the current Sishen operations.

Jan 1, 2006

By P. R. Jochens, D. D. Howat, C. W. Wolhuter

Prof D. D. Howat (Member): I am a man with a grievance this afternoon. The other authors of the paper entered into a conspiracy to ensure that I presented the paper, and finally even had the audacity to say that this was the least that could be expected from me as I had done so little of the other work. Looking at the distinguished audience here that includes some figures who have forgotten more about cement that some of us have ever learned, I realise how right the other authors were. I feel very much cast in the role of the fool who was pushed in where angels fear to tread. I hesitate to say, Sir, that I would not use the word angels in any definition of the authors of this paper. In presenting the paper, may I try to put forward a few simple points about cement that are probably as little known to the majority of the audience as they were to me-at least until very recently. Concrete, made by mixing Portland cement, sand, crushed rock and water is the most widely used constructional material in the world. Generally the production of actual Portland Cement is about two-thirds that of steel and by the time this is formed into concrete the total is about five times the world tonnage of steel produced. A very rough approximation suggests that world consumption of concrete is about one ton per person per annum. Apart from fresh water mankind consumes no other material in such quantities. What mankind originally required was a mortar to be used for joining blocks of stone or bricks. Such mortar was originally made from limestone burned in a kiln and then mixed with water. Production of mortar of this type began over 5,000 years ago. Some samples from pyramids in Egypt have shown this mortar to be in good condition although over 4,500 years old. The progress of technological development was very slow until 1824 when an English bricklayer, Joseph Aspidin, patented a new mortar material which he made by burning limestone and clay together in his kitchen stove. Aspdin called his product &apos;Portland Cement&apos; because, in colour, it resembled a well-known building stone quarried in the Isle of Portland on the south coast of England. Aspid&apos;s same types of raw materials are used today in modern cement production and the product is still referred to as Portland cement. A lime-containing material such as chalk or shell and a clay-type material such as shale, slate or clay itself, are mixed in the required proportions, ground and fed to a kiln where the minimum burning temperature is about 1,500°C. The raw materials react to form hard chunks of a material known as &apos;clinker&apos;. About 5 per cent of gypsum is added to the clinker and the mixture is then ground to a very fine powder, the function of the gypsum being to control the rate of setting of the concrete. The key oxides in cement production are lime, silica, alumina and iron oxide. The possible reactions occurring during and the products of the burning process are shown in Table I.

Jan 12, 1968

The Mineral Density Separator (MDS) was developed by Mintek to predict mineral separation in a plant, evaluate efficiencies and develop scale-up parameters. This study investigated the influence of particle size on the results of the MDS, the misplacement of material in the MDS and the possibility of replacing heavy liquid float and sink analyses of coal with MDS analyses. Six tests were done with coal of different size ranges. Each MDS layer was subjected to a float-sink analysis whereafter each float fraction was screened to determine the particle size distribution. The results indicated that MDS results represent float-sink analyses when compared to an ash curve. There is some misplacement in the different MDS layers, but this does not seem to influence the results negatively. Keywords Mineral density separator, sink-float analyses, heavy liquid analyses, washability curve

Jan 1, 2006

By F. M. C. C. Vieira

Four mining alternatives for exploiting an ultra-deep orebody were assessed through a multidisciplinary evaluation process which involved: the generation of a 3D geological model; the design and scheduling of life-of-mine layouts; the analysis of anticipated ventilation and cooling conditions; the study of rock-related risks of mining in ultra-deep stress environments; the logistic implications of transporting men, rock and materials; and, lastly, the economic implications of each option. Once results from the integrated mine design assessment were available, mine planners were faced with an important problem to solve: how to identify the optimal mine design alternative when numerous assessment measures and multiple decision criteria needed to be considered simultaneously? To address this ‘multiple-attribute decision problem’ and arrive at the ‘optimal layout for ultra-depth’, a generic decision methodology that uses principles of ‘utility’ was applied. The methodology assumes that ‘single-value risk estimators’ do not account for the inherent variability of real conditions. Therefore, risk estimators were represented by statistical distributions of their incremental changes, where applicable. The stochastic variables, once defined, are used as inputs in the ‘utility’-based layout decision scheme. This ‘utility’-based decision methodology offers a framework for mine design decisions to be made objectively, when complex trade-offs between multiple risk domains need to be considered simultaneously. Upon applying it, one of the layouts emerged as the preferred alternative. Keywords: Utility; mine design; multiple-attribute decision; layout selection

Jan 1, 2003

By I. R. Firth, D. L. Taylor

Metal mining operations, in particular gold mining operations, use intensive ore control procedures in order to manage the extraction of ore zones from benches containing both ore and waste material. Typical grade control procedures rely on blast hole samples to indicate ore grade. Statistical techniques and geological controls are then used to create two-dimensional polygons, which indicate zones of material designated as ore. These ore-polygons are calculated using pre-blast material locations and are generally not corrected for rock movement caused by blasting. This lack of correction appears to exacerbate the material mischaracterization problem of sending ore to the waste dump and/or waste to the mill. One Nevada gold mining company has estimated that this could be a $10 million per year problem for their operations. Using a simplified vector field algorithm, a method of taking point movement data and interpolating post-blast positions for all nodes in a polygon has been developed. Currently working in 2-dimentions (X-Y), this algorithm utilizes the movement vectors calculated from pre-and post-blast positions of targets placed in a blast, to generate a spatial transformation function for any point on the bench. This transformation is then applied to the nodes of the ore-polygons to produce modified dig lines ore polygons reflecting distortion and movement resulting from the blast. The method as implemented uses common mine planning routines and is performed using the Surpac software suite. The method may be adapted to use any pre-and post-blast point movement data available, and most mine planning suites include the simple interpolation algorithms used. Keywords: Blast movement; Ore control; Open pit blasting; Grade control

Jan 1, 2003

By G. Asbjörnsson, E. Hulthén, P. Papadopoulou, C. M. Evertsson

Crushing plant managers need to assess, manage, and communicate the environmental impact induced by their crushing plant operations as a step towards the sustainable development of the company. However, performing reliable environmental impact calculations of crushing plants can be challenging when the availability of operational and emission data is low, and when the company’s environmental expertise is not adapted and connected to plant operations (or does not currently exist). To address these challenges, this paper proposes a practical approach where the lifecycle assessment methodology (LCA) is combined with process simulations in a web-based tool. To describe what functionality such a tool should have to be incorporated into a company’s workflow, the system that surrounds a crushing plant is analysed. Further, a case study with a three-stage crushing plant is introduced to showcase how the simulated power draw results produced with the beta version of the tool can be compared to measured sensor data from the crushing plant for one operational day. The results indicate that the simulation tool can provide an adequate estimation of the specific energy for the different material fractions and give an overview of the environmental impact of the process caused by electricity and explosives consumption. Plant managers and operators can use this tool to calculate the environmental impacts of their plant and simulate how different operational strategies influence them. Keywords: LCA, environmental impact, coarse comminution, crushing plant

Jan 1, 2020

By L. Shoke

The aim of this study was to develop an in-house tensile testing procedure that would yield accurate and reproducible parameters as input material properties into computational models for numerical simulations of the mechanical behaviour of TM380 mild steel. To achieve this objective, we reviewed the ISO 6892:2009 tensile testing standard along with reported good practice guidelines. Tensile tests were conducted on a dog-bone shaped TM380 mild steel specimen with strain gauges attached on either side, to monitor alignment and measure strain, using three different types of tensile testing machines. Parameters quantified included yield stress, ultimate tensile strength, and modulus of elasticity. The values of these parameters were found to be in agreement with the values supplied by the manufacturer&apos;s specification and showed minimal variations between laboratories. Thus it can be concluded that the tensile test procedure used resulted in accurate and reproducible results. The strain values calculated as per standard were in disagreement with those determined from extensometer and strain gauges and resulted in lower elastic modulus values. This confirms that the current testing procedures require the use of long-range strain gauges or extensometer to determine the strain. A chemical analysis was conducted to verify the specification by the manufacturer. The specimen was found to be fairly homogeneous with minor sulphide inclusions. The micrographs reveal a pearlite and ferrite structure typical of mild steel, and the fractographs show a dimpled surface typical of ductile fracture, which is an attribute of mild steel.

Jan 1, 2013

By D. R. Hack

The complexity of commercial mining software has gained rapidly over the past decade as hardware developments have surpassed software capabilities at a staggering rate. Software users, recognizing the limitations of off-the-shelf applications, have adapted embedded scripting languages. Custom programming has always had a vital role in mine computing innovations, yielding a dynamic research environment in industry and academia. Fields such as industrial minerals can benefit from customization of existing software, since the majority of mine planning software was designed for large metal mines. Different customization approaches utilizing embedded scripting languages are presented, with examples of sand and gravel applications in development. Following implementation by Surpac and development of the Surpac Command Language, Tcl has been widely applied. Mintec introduced Python, also extensible and portable amongst various operating systems, for use in their MineSight products. In early 2000, Gemcom introduced the use of Microsoft Visual Basic for Applications, widely used customization tools for a decade. Datamine implemented a flexible multi-language approach, with all program commands and processes available through the COM Server Interface. This extends customization from the existing macro language to scripting in HTML, JavaScript, or any language that supports COM.

Jan 1, 2003

By F. Cihangir, A. Kesimal, K. Karaman, B. Ercikdi

Uniaxial compressive strength (UCS) and shear strength parameters(cohesion and angle of internal friction, Cand F) of rocks are important parameters needed for various engineering projects such as tunnelling and slope stability. However, direct determination of these parameters is difficult and requires high-quality core samples for tests. Therefore, this study aimed to explore the applicability of the Brazilian test (BT) - a simple, less sophisticated and inexpensive method for both specimen preparation and testing - to estimate the UCS and shear strength parameters of rocks. Thirty-seven rock types were sampled and tested, 24of which were volcanic, 8 were metamorphic, and 5 were sedimentary. Statistical equations were derived to estimate the UCS and shear strength parameters of rocks using the BT. The validity of the statistically derived equations was confirmed using predictive analytics software (PASW Statistics 18). A strong linear relation was found between BT and UCS values. BT and UCS values exhibited prominent linear correlations withthe cohesion values of rocks. The Mohr envelope was also used to determine the cohesion and friction angle of rocks using BT and UCS values. It is deduced from the current study that the BT values can be used to estimate the UCS and cohesion. However, no relation was observed between the angle of internal friction values and the UCS and BT for all rock types. Therefore, different approaches are suggested for the estimation of the internal angle of friction for application in the preliminary design of projects.

Jan 1, 2015

By W. Newcomen, D. Brox

The assessment of the stability performance of open pit highwalls has traditionally been based on consideration of surface movement rates. Although generally accepted in industry, this approach presents challenges for establishing appropriate threshold values to allow for safe mining operations and does not address the issue of total strain. Surface movement monitoring data from a limited number of open pit mining operations in North and South America has been evaluated in terms of highwall strain, rock mass quality and inferred mechanism of instability. Threshold strain levels for key stages of highwall stability proposed from previous work has been reviewed and are endorsed based on evaluation of additional data. An empirical highwall strain criteria for the assessment of highwall stability performance is postulated based on relatively consistent trends in highwall strain data. L’évaluation du niveau de stabilité des hauts murs de carrières a traditionnellement été basée sur les taux de mouvements de surfaces. Bien que cette approche soit généralement acceptée à travers l’industrie, elle présente des défis pour la définition de seuils appropriés concernant la sécurité des opérations minières et n’adresse pas la notion de déformations totales. Des données de mouvements de surface provenant d’un nombre limité d’opérations minières à ciel ouvert d’Amérique du Nord et du Sud ont été évaluées en terme de déformation des hauts murs, de qualité de la masse rocheuse et des mécanismes inférés d’instabilité. Des seuils de déformation pour différentes phases clefs de stabilité de hauts murs ont été revus et sont endossés, basé sur l&apos;évaluation de donnés additionnelles. Un critère de déformation empirique pour l’évaluation de la stabilité des hauts murs est postulé, basé sur des tendances relativement consistantes de données de déformations de hauts murs. Die Beurteilung der Stabilität von hohen Felsböschungen basiert traditionellerweise von Oberflächenbewegungen. Obwohl dieses Verfahren im Allgemeinen akzeptiert wird, stellt es jedoch gewisse Probleme für die Festlegung von Grenzwerten für die Sicherheit dar. Die totalen Dehnungen werden bei dieser Betrachtungsweise vernachlässigt. Eine beschränkte Anzahl von Oberflächenbewegungs Daten von Bergbauwerke in Nord- und Südamerika sind in Bezug auf die Dehnungen von hohen Felsböschungen, Felsqualität und davon abgeleiteten Bruchmechanismen untersucht worden. Grenzwerte für die Belastung von hohen Felsböschungen während den massgebenden Bauetappen aus bisherigen Projekten sind begutachtet und durch zusätzliche Untersuchungen bestätigt worden. Gestützt auf relativ konsitenten Trends, ist hier ein empirisches Verfahren der Dehnungen in hohen Felsböschungen zur Beurteilung der Stabilität vorgestellt.

Jan 1, 2003

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009