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By A M. Myrvang, B Nøst, N Q. Trinh, I S. B Bergh

The iron ore producer Rana Gruber AS is situated in northern Norway just below the Arctic Circle, and has been producing hematite and magnetite concentrates for more than 60 years. Since the late 1990s, the major part of the production comes from a sublevel stoping underground operation after many years of open pit mining. Despite moderate mining depth, the operations have experienced considerable rock stress problems due to quite high tectonic, horizontal stresses. To manage the problems, comprehensive rock mechanics investigations have been carried out by SINTEF, a major contract research organisation. This has included in situ rock stress measurements, laboratory investigations and numerical modelling. Based on this and practical experience, satisfactory design of vertical and horizontal pillars was achieved. At depth, the ore width increases from 30–40?m to more than 100?m. This, together with a major planned increase in production, called for a change of the mining method. After thorough investigations and considerations, it was decided to change to sublevel caving, very much like the LKAB system. The development of the new system has been closely followed up by rock mechanics measures, including 3D numerical modelling and comprehensive monitoring of deformations and rock stress changes. To achieve a satisfactory caving of the hanging wall, all vertical and horizontal pillars in the sublevel stoping area had to be removed. This has been a challenging task, and the development of the caving has been slow until recently. However, now the caving develops satisfactorily.CITATION:Bergh, I S B, Trinh, N Q, Myrvang, A M and Nøst, B, 2014. From sublevel stoping to sublevel caving at Rana Gruber, Norway – rock mechanical aspects, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 323–330 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

The Beaconsfield Gold Mine within the township of Beaconsfield in northern Tasmania has been established in recent years to exploit a known resource in the Tasmania Reef which was mined to a depth of 450 m below surface between 1877 and 1914 yielding 850 000 ounces of gold. Activity at Beaconsfield over the past 30 years has involved drilling to assess the resource and rehabilitation of the top 100 m of the Hart Shaft that had collapsed since the original closure. More recently the mine has been dewatered to the 375 m Level and work is well advanced establishing infrastructure aimed at recommencing production during 1998 - 99. This paper reviews geotechnical studies undertaken to-date and provides a brief overview of some practical methods of analysing ground conditions. It pursues simple observation and analysis as a tool for assessing mine design and ground support options without recourse to extensive monitoring and measurement and avoids the use of elaborate models before the basics are understood.

Jan 1, 1997

By B J. van Loggerenberg

The capital cost of major items of mining equipment is very high. The operating cost of such equipment is also high. It is therefore important that such expensive equipment is used productively. To this end mine management uses production data systems and management accounting systems to monitor events and provide data for analysis to enable management to make operating and business optimisation decisions. This could be done better if there was an understanding of productivity in terms of its utilisation and efficiency components. What has been missing has been a methodology to properly account for the productivity of equipment in terms of its contribution in dollars to the costs and profit of the mine. An explanation of the Productivity Accounting methodology will be given. It will then be shown that productivity has two components, that of capacity utilisation and efficiency. These are defined and the dollar contribution of each to costs and profit shown. The efficiency component tracks the effect of proportional changes in input cost quantities used in the mining process as mining production changes. The capacity utilisation component tracks the effect of step changes in the input cost quantities used in the mining process as mining production changes.

Jan 1, 2003

By N Trabelsi, D Bakun-Mazor, Y Ben-Ari

As part of a comprehensive project to develop a remote sensing tool for evaluating the mechanical properties of rocks, one must obtain a rapid indication of these properties using conventional field methods. A common method for evaluating the mechanical properties of rocks in the field is to use a Schmidt hammer, a portable device that measures the rebound (R) of a spring-loaded mass impacting against the rock surface. Since the 1960s many studies have been made to find empirical correlations between the R value measured by the Schmidt hammer and mechanical and physical properties such as uniaxial compressive strength (UCS), elastic modulus, density, and porosity. Despite the existing correlations in the literature, this work is required to establish detailed empirical relationships for the carbonate rock units in Israel. To do so, 150 rock samples were collected from 38 different outcrops of carbonate rock units. In each outcrop, 20 impacts were made using a Schmidt hammer at different but adjacent points. The impacts were done horizontally perpendicular to the vertical rock walls. In the laboratory, we measured the density, effective porosity, water absorption, UCS, and elastic modulus. The rock samples we selected contained a wide range of UCS: from 7 to 270 MPa. Our empirical correlations indicate an exponential relationship between R and UCS and the elastic modulus, and linear relationships between R and density, porosity, and water absorbance. The most reliable index is the average of the five maximum impacts out of the 20 made in each rock outcrop. The correlation equations obtained from this work will make it possible to effectively evaluate the mechanical properties of the intact rock in the field, thereby aiding development of advanced tools for rock mass characterisation by means of remote sensing.

Nov 29, 2022

By M F. Navarrete

During 2003, different plastic stemming plugs (Cats«, Stemtite«, and Taponex«) were tested in EscondidaÆs Mina Sur, to determine the effect on gas retention time when used in conjunction with drill cuttings in production shots with a blasthole diameter of 10 5/8ö. Longer retention times were expected to provide greater fragmentation and muckpile looseness. In order to determine which plug showed the greatest enhancement of stemming retention, 17 trials were carried out û in the first seven tests, only the Cats were used, in the following five tests, a combination of Cats, Taponex and Stemtite were used, and in the last three tests, only the Taponex plug was used. In the last two blasts, drill cuttings were used without stemming plugs as a benchmarking exercise. Blasts were filmed with a high-speed camera, which could record the detonation times of holes using rolls of shock tube tied to stakes at the hole collars, to act as flash indicators. The camera allowed measurement of the time between charge detonation and the commencement of stemming ejection. In order to obtain the statistical parameters of each one of the stemming plugs used in the 17 trials carried out, the Minitab software was used and a data base was created for it, corresponding to each stemming configuration with the retention time obtained from the filming. Once it was determined which stemming plug provided the greatest enhancement of stemming retention, the impact on the fragmentation was analysed using the WipFrag image analysis software to estimate the muckpile size distribution.

Jan 1, 2004

By Buizen M

An investigation into the mechanics of sub-surface deformation caused by caving of the extracted area behind retreating longwall faces has been completed by the Subsidence Engineering Section of the New South Wales (NSW) Department of Minerals and Energy. Changes in strata bulk permeability were also measured by standard packer tests undertaken before and after mining. The strata movement was measured by a multi-wire borehole instrumentation system consisting of mechanical anchors installed at different horizons in a borehole extending from the surface to the coal seam. The mechanical anchors were collected to suspended weights on the surface by stainless steel multi-strand wires. The movement of these weights was monitored as the longwall face approached and retreated past the borehole. The anchors did not move significantly until the face went past the borehole. For subcritical extraction geometry with the extraction width to mining depth ratio of 124, the caving zone extended to roughly 9 times the extracted seam thickness above the seam roof. Tensile strains within the overburden tended to be much more closely related to stratigraphy than to the proximity to the extracted seam roof. Larger tensile strains were associated with layers of sandstone, siltstone and conglomerate, whereas layers of mudstones, claystones and coal underwent much smaller strains indicating subsidence in blocks. A beller correlation was observed between pre-mining Rock Quality Designation and permeability than between rock type and permeability. This correlation was less evident in the post-mining core logs. There was an overall increase in bulk permeability after mining.

Jan 1, 1990

By Ohga K, Isobe T

Basing upon many and long practical experiences of gas drainage from coal seam and results investigations on the gas flow through in si-tu coal seam using tracer gases,it became clear that solid coal itself is hardly gas permeable or has extremely low gas permeability. Almost all of gas flows from a coal seam into boreholes through fracture net- works intersecting with them.Primary and secondary fractures in coal seams differ in their size and continuity from place to place according to differences of the coal strength and the stress conditions. A lot of gas can be drained through boreholes which intersect with many and/or wide fractures. A mathematical model for gas flow from a coal seam to a borehole through a discoidal fracture is proposed. From the numerical analyses,the apparent radius of the discoidal fracture in this model is shown to be a good indication of the gas drainage ratio. In addition to this,an atempt to make fractures around a borehole using high velocity water jet(ca.lmm dia.,300-700atm., 100-200 1/min.) is introduced.

Jan 1, 1982

Mining companies in order to compete and succeed in being viable business propositions must look to the future and select mining methods which guarantee improved efficiency and productivity as well as lower costs.A mining company in adopting a method of mining must now select the equipment most compatible. To some mines compatible equipment may mean the use of drilling jumbos to replace hand held rock drills or the use of load haul dump units to replace scrapers. To other more mechanized mines compatible equipment may mean the use of raise borers and road heading machines. The right decision will be where equipment compliments method in such a way that the working environment is improved, productivity is maximized, cost if reduced and all profit opportunities are optimized. An example of such is where the use of improved mining techniques in underground operations may see cut off grades reduced. By selectively mining these lower grade orebodies, smaller operation's ore reserves improve and the capacity for continued growth is enhanced.

Jan 1, 1990

By Duke J. H

Advanced computer aided geological modelling techniques are now available to the geologist to allow the rapid evaluation of a gold orebody at various stages of its development. The types of grade estimation techniques used change during the various stages as the density of drilling and knowledge of the deposit increases. At the prospect evaluation stage drillhole intercept selection techniques are coupled with preliminary 2D (vein or layer) modelling or 3D block modelling techniques to arrive at a geological resource estimate. At the prefeasibility and feasibility stages more sophisticated 2D and 3D modelling techniques, such as domain controlled grade interpolation with anisotropy, are used along with interactive open pit and underground mine design, to calculate recoverable reserves. At the production stage closely spaced blasthole sample data is modelled quickly and coupled with interactive grade control facilities. Shot volumes, tonnages and grade estimates can be databased to provide reconciliation figures. These modelling techniques are embodied in MINEX-3D, an Australian software system which, with the emergence of the 386-based PC and high resolution (VGA or better) graphics, makes a whole range of advanced geological modelling techniques available to most exploration and mine geologists.

Jan 1, 1989

By Aust M. I E

IT is the custom, I must admit, for a presidential address to be a review of the progress during the year of the institution presided over, and of the sciences and arts within its ambit. On this occasion precedent is departed from in favour of a subject by request.As man has at last, in employing gravimetric and electrometric methods of subsurface research, started on the rational use of divining rods with some knOWledge of their governing laws and principles, and with some ability to interpret the results obtainedfrom them, I was asked to add to the voluminous literature of the quack or empiric divining rod. James Mansergh, the author of Melbourne's sewerage system, in his presidential address before the Institution of Civil Engineers in 1901, admitted he was afraid touse the hazel rod lest in sinking on its indications to some solution.

Jan 1, 1928

By F A. Rosyid

Mineral resources are national assets which must be capitalised for national development. Those assets should be transferred into real economic capital and then into social capital to achieve national/regional prosperity. Successful development in the mining industry will depend on the correctness in determining the role of mining industries for regional development. Using the context of sustainable development, this paper will analyse the concept and process of mining industry development as an accelerator to achieve regional sustainable development, using the mining operations of PT Newmont Nusa Tenggara (PT NNT) in Batuhijau, Sumbawa Barat Regency as a case study. In the premining activity phase, Sumbawa Barat was dependent on the agricultural sector. Agriculture contributed around 40 per cent of the regional gross domestic product (GDP). Meanwhile, in the activity phase, mining became the sector with the biggest contribution to regional economy. From its operation in Batuhijau, PT NNT contributed around 70 per cent of the regional GDP per year since 2001. In year 2000, the GDP had increased 170 per cent from its figure in 1999. However, due to its depleting reserve, PT NNT will finish its activity in Batuhijau by year 2015. Consequently, the Government of Sumbawa Barat Regency must develop other sectors in the post-mining phase to sustain economic development. Based on location quotient (LQ) and input-output analyses, Sumbawa Barat should develop its priority sectors, ie agriculture, trading and hotel, services and construction to achieve sustainability after mining life. Development of these non-mineral sectors is expected to sustain economic growth in the region.

Jan 1, 2008

By M G. Aylmore

Thiosulphate is an attractive alternative reagent to cyanide for processing gold ores. It is relatively cheap and non-toxic, forms relatively strong gold and silver complexes, and readily leaches gold ores in ammoniacal solutions, catalysed by Cu(II). It is particularly suited to carbonaceous ores where the recovery of gold by cyanide is poor. However research over the past 20 years has identified a number of issues and impediments that must be understood or overcome before an overall process can be demonstrated as practical and economic for typical oxidised gold ores. This paper reviews our current understanding of thiosulphate chemistry and mechanism of gold dissolution, and discusses the stability of thiosulphate and polythionates. It then reviews the results of leaching various gold ores that have been reported in the literature, discusses gold recovery options, and considers environmental and toxicity issues. Some of the issues that require further research include decreasing the oxidation of thiosulphate by Cu(II) or other oxidants, increasing the extraction of gold compared to cyanide, and understanding the variation in gold recovery between ores. More work is also required to minimise the effect of polythionates on gold recovery using resins or alternative absorbents, to improve the elution of copper and gold from resins, and to recycle or minimise the concentration of reagents.

Jan 1, 2002

By White A. H, Vihena M. T M B

Presently, orebody modelling consists basically of fitting a mathematical model to represent spatially a certain geological variable, generally grade. An orebody model is constructed from a set of sample data obtained from various locations in the orebody, thus it is only one form of representation of the true phenomena. Checking the compatibility of the data with the modelling procedure is the most important factor when assessing confidence in the orebody model. The level of confidence in the model will depend on the adequacy of the data set and the validity of the basic assumption required by the modelling method. Fractal geometry is one way of modelling the spatial distribution of a geological variable in an orebody geometry. Fractals can be used to interpolate the Z(x) geological variable at unsampled sites. The concepts of self similarity and self affinity that form the basic assumption of fractal geometry theory which areinvestigated. The population distribution of the geological variable in question must be examined to determine the appropriateness of both fractal geometry and geostatistical modelling methods. The selection of the most appropriate method depends on the available data. A researcher or a practitioner needs to understand the strengths and limitations of the various modelling methods before choosing the most appropriate method. This study investigates the fractal properties of grade distribution using the variogram and some proposed variations as techniques to measure the fractalness. The aim is to assess applicability of fractal geometry theory to modelling ore grade distribution in a deposit. A comparison of the results demonstrates the methods which better capture the spatial behaviour of the variable under study.

Jan 1, 1995

By Sterns UJ, Weller KR

Grinding to sizes less than 80 per cent passing 20 ¦m in both primary and regrind circuits is becoming increasingly important in processing metalliferous ores, as many of the remaining orebodies are very fine-grained and refractory. The process of very fine grinding, however, is expensive, and neither the performance nor the design criteria are well understood. This paper presents some findings from a collaborative research program, one of the objectives of which has been to better understand and improve the performance of very fine grinding circuits. Data from surveys of an industrial tower mill grinding circuit are reviewed and analysed using the population balance models of the CS]RO and 7KMRC. The performance of both models with regard to changes in feed size distribution, ball load and feedrate is assessed using these data. From comparisons between pilot and full scale tower mill operation a prototype scaling methodology is also presented which shows promise in allowing the models to be used to predict the effect of changes in mill Design.

Jan 1, 1993

By P T. Hick, T J. Cudahy, M S. Caccetta

Dust derived from mining and handling of ore has been identified as a major concern for the mining industry in Australia and may be critical to the future viability of some resource industries (CSIRO, 1999). Operational techniques to derive accurate measurements of anthropogenic dust on vegetation and infrastructure are necessary for the long-term management and monitoring of the environment surrounding mining operations. Airborne hyperspectral VNIR-SWIR systems can potentially provide these monitoring data. This paper outlines a method developed for deriving quantitative measurements of dust quantity on mangroves using remotely-sensed airborne hyperspectral data. The results show that it is possible to detect and quantitatively map iron oxide dust distribution using properly calibrated airborne visible to short wave infrared (VNIR-SWIR) data.

Jan 1, 2002

By Firkin GR, Allen RJ

Sulphide Corporation Pty. Limited has roasted a number of different zinc sulphide concentrates on its sinter machine which pro- duces zinc-lead sinter for an Imperial Smelting Furnace, and results have varied widely. The differences are considered to be functions of !concentrate particle size and reactivity. Amdel have used differential thermal analysis to examine these concentrates and two major effects have been found. Firstly, in concentrates 1containing small quantities of pyrite and chal- L [copyrite, heat is liberated at 400¦C to 650¦C [by oxidation of these two sulphides. Secondly, as particle size decreases, heat release from the oxidation of zinc sulphide commences at flower temperatures and rate of heat release In a sinter bed, the presence of some rite and chalcopyrite would help to heat the cc sulphide to ignition temperature in a orter time, while a finer concentrate would sult in roasting being completed more ickly. Both of these effects result in a arper flame front and minimise the chance heat and combustion fronts being mismatched. is theory is supported by sintering results tained by Sulphide Corporation. As a result

Jan 1, 1975

It is not often that mines have as much warning of the approach of bad ground conditions as was the case at the Western Mining Corporation, Kambalda Nickel Operations Lafranchi/Schmitz Decline. Most aspects of this operation are in fact quite unique and like the best solutions, the answer to the problem of weak and foliated ground conditions was relatively simple; requiring the use of readily available explosives although the idea of using it in this manner may not be the most obvious.The use of high shock energy POWERGEL 2131 cartridges proved to be the correct answer, in conjunction with small changes in drill pattern design. The resulting lack of overbreak bears testimony to the success of the concept and the commitment of the miners to achieving a safe working environment.

Jan 1, 1992

Electronic Detonators have made significant strides over the last few years, both in quality of product and performance in different blast applications. The precision and flexibility of the SMARTDET units provides the mines with a powerful means of controlling blast results, giving both cost and productivity improvements. The SMARTDET Electronic Detonator System, robust and easy to use, has been successfully deployed over the last 18 months in improving mine productivity and creating safer working conditions in both quarrying and long-hole stoping. The key to the improvements has been the precision and flexibility of the electronic timing, and the ability of the mine personnel to grasp the concept quickly and use it effectively.

Jan 1, 1999

The process of refurbishment is not a precisely defined one. It is under- stood to mean an upgrading of a plant which is normally performed only once. The application of refurbishment in the field of materials hand- ling equipment poses particular problems because complex plants con- sist of individual components having quite different remaining service lives. For this reason, a systematic, proven procedure is proposed for the refurbishment of large materials handling equipment, designed to ensure economic implementation in accordance with the company goals. Rheinbraun2 has been using materials handling equipment since 1900, the largest units today being bucket-wheel excavators with a daily capacity of 240,000 bank cubic metres of overburden and a service weight of up to 13,500 t (metric tons). Since 1975, more than 50 large-scale refurbish- ment projects have been carried out in the company. In the process, refur- bishment has turned out to be the proven alternative to replacement of large materials handling equipment. Rheinbraun Engineering,3 a Rhein- braun subsidiary, carries out planning, consulting, and supervising work in the implementation of refurbishment projects in Germany and abroad. The most recent example is the refurbishment of Dredger 11 of the State Electricity Commission of Victoria in cooperation with Krupp-Australia, Melbourne.

Jan 1, 1989

By U E. Sibilski

A pilot plant evaluation of the Savmin process, for the purification of mine water was commissioned by Anglogold and conducted at the Stilfontein Gold Mine, Margaret Shaft at Stilfontein in the North West province of South Africa. The purpose of the project was to obtain the operating conditions and operating costs, to produce different qualities of product water, as well as design parameters for upscaling to an industrial plant. The project was undertaken by AngloGold and Mintek of South Africa.

Jan 1, 2003