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By M Hudyma

Open stope mining is the most common mining method employed in underground, hard rock mines in Canada. It is characterised by relatively small, single lift stopes (20 000 to 100 000 tonnes), and fast stope turnaround times. Host wall rock mass conditions, which are typically poor to fair, are the controlling parameter in stope dimensioning. Rock mass stability is maintained by designing all stope surfaces at a stable dimension, and through extensive use of cablebolting for stope backs and frequently stope hanging walls. Dilution control is a high priority. The typically small, high-grade, deep and irregularly shaped orebodies are incrementally developed, usually in a bottom to top direction. In many cases, high stress is encountered due to the depth of the orebodies. Overstressing of pillars and hanging pillars are avoided through the use of pillarless or early pillar recovery mine sequencing strategies. Stopes are invariably filled, and in higher grade and wider orebodies, cemented fill is commonly used. This paper generalises many of the similarities found in Canadian open stope mines.

Jan 1, 2000

By Badal R

Rock Discontinuities ("joints") affect blasting results. An investigation was carried out to understand if blast parameter such as spacing needs to be altered with the change in joint direction. Small scale laboratory studies in jointed limestone blocks have been carried out. It is shown that optimum spacing is variable with the "joint" orientations. Evidence is presented from field studies in four limestone quarries supporting laboratory studies. Reasons for success and failure of widespacing technique is also provided. Only with suitable orientations of "joints: widespacing is successful.

Jan 1, 1990

By Yusuf R

Many heap and dump leaching processes involve competitive, complementary and sequential reactions between multiple minerals and reagents. A comprehensive model has been developed to deal with these complex chemical interactions which is based on diffusion control of the reaction rates. All of the mineralogical and chemical data are obtained from representative samples of the ore or the chemical literature. These properties have been incorporated in a general way, making the model applicable to a range of ore-process systems. The simulation is used to predict the absolute reaction rates and can be used before any leach tests are carried out on the ore itself. The applicability of the model and some tests of its validity are presented.

Jan 1, 1984

Newmont Australia Limited has for some 15 years mined a number of large open cuts associated with the Telfer Gold Dome deposits. The principal ore body exploited has been the East Flank of the Main Dome where a very high grade gold reef deposit of mixed metal sulphides, grades in excess of 20gA Au, has been mined in conjunction with dissemi- nated mineralisation contained in the overburden material. The main ore body has been under review for some years as an under- ground mine, however due to the ore body widths of less than 1 metre and a dip generally less than 35 degrees and a very weak host rocks earlier studies all resulted in a continuation of open pit mining activities. In early 1988 it was recognised that open cast mining would not be able to mine all of this valuable resource and a feasibility study was commenced to come up with a practical and economic approach to underground mining.

Jan 1, 1991

By Bourgeois F

The population balance concept has provided a useful framework for the description of the operating behavior of the ball mill. This approach finds expression in the so-called selection breakage function model for batch and continuous mills. This model produces very good descriptions of the size distribution of the products from ball milling operations and the model is very useful for the description of batch and continuous mills and, when combined with models for classifiers and other unit operations, provides a solid basis for flowsheet simulation procedures. The breakage and selection function model is essentially descriptive and not predictive because the parameters in the model cannot as yet be related to the fundamental material properties of the material that is broken and to the fracture mechanics that govern the comminution of brittle particulate material during the rapid impact and compression events that occur with high frequency in a ball mill. The population balance approach smears over the individual processes and regards the ball mill as a continuum with breakage occurring continuously in time and space. New experimental techniques, particularly the adaptation of the Hopkinson bar as the ultrafast load cell (UFLC) to the problem of observing the extremely rapid impact fracture of particulate solids, have made it possible to make accurate and consistent measurements of particle strength, particle fracture energy and the single-impact breakage function. These quantitative measurements have been incorporated into a new conceptual model for the description of the ball mill. The model is based on identifying all events that give rise to particle breakage, and using the fundamental experimental data obtained on the UFLC and other single-particle fracture tests, the probabilities of these events can be independently determined. The distribution of impact energies that occur in the ball mill has been established by discrete element simulation of the media motion. The probabilistic description of the individual fracture events and the distribution of impact energies are combined to make a priori predictions of ball mill performance under a variety of operating conditions. The new model is used to calculate the selection and breakage functions for quartz in a small batch mill.

Jan 1, 1993

Increasing demands on quality of metallurgical grade alumina and for lower production costs led to the development of a new fluid bed calcining process. The process, jointly developed in Germany by Vereinigte Aluminium Werke A.G. and Lurgi Gesellschaften m.b.H., takes advantage of modern chemical engineering methods such as counter-current flow of combustion air and solids, direct heat-exchange between combustion air and fine solids and near stoichiometric combustion of oil in a fluid bed. Using a two-stage Venturi-type suspension preheater for heat-recovery from combustion flue- gases, the circulating fluid bed technique with internal oil combustion at 2.2000 F for the calcining step and 'a five-stage fluidized bed cooler for heat recovery from calcines, the process gives an outstanding heat- efficiency. In a first industrial plant for 560 sh. t. alumina per day heat consumption figures of less than 1.400 BTU/lb A12O3 were achieved.

Jan 1, 1971

By C Donnelly

Redpath Australia is using a unique mining method for the Australian underground coal industry at Kestrel Mine Extension in the Bowen Basin, Central Queensland.The project involves completing two separate drifts from the surface for access to the German Creek Coal Seam located approximately 230 m below the existing surface. The scope of work is primarily the construction of two drifts; the first is 1577 m at 1 in 6 gradient and the second 1874 m at 1 in 8 gradient. Each drift has been developed by a Mitsui S200 roadheader with modifications to allow for a continuous tunnelling/mining cycle operation. A shotcrete boom has been fitted to the left hand side of the machine with the operators console located at ground level. Another operators console is elevated on the right hand side of the machine to allow operation of the rotary drill boom which is mounted on a slide rail to allow flexibility of positioning depending on the stage of the cycle. In support of the roadheader activities, an integrated conveyor system mounted on a sliding floor arrangement is able to be advanced as the mining face progresses. This sliding floor consists of four 1.5 m × 6 m sections that utilise hydraulic rams to ‘walk’ inbye, allowing room for installation of precast concrete floor panels for final floor completion. This method borrows from the tunnelling and construction industries to eliminate place-change delays in the mining cycle by enabling complete ground support installation without retreat of the primary development machine from the face. The aim is to reduce the project duration with the completion of final floor and services to within 30 m of the operating face as it advances.

Mar 21, 2011

By Theophili CN, Kapenis AP

Seismic tomographic imaging has been applied to determine the blast induced damage zones in bauxite pillars in underground mining. At the retreating stage, when pillar dimensions are reduced from 8 x 8 m to approximately 5 x 5 m, the' seismic tomographies reveal, through measurements of the P-wave velocities which is a measure of the degree of fracturation of the pillar rock mass, the presence of three zones within each pillar. In the external zone, where velocities recorded are below 750 m/s. extensive pillar damage occurs which is attributed to both the growth and coalescence of pre-existing cracks and even the creation of new cracks in the rock mass. This effect is in agreement with literature, when considering the peak particle velocity as a criterion for rock failure in tunnels. In the intermediate zone, where velocities range between 7S0-1000 m/s, damage to a much lesser extent occurs which is due mostly to growth of pre-existing cracks and widening of their apertures. The inner zone, where velocities exceed 1000 m/s, is considered to be unaffected by blasting. Simple remedial measures of low cost, which are based on blasting mechanics are proposed to minimise the blast induced damage zone and consequently the transition zone.

Jan 1, 1995

By McKenzie C, Michaux S

Modern quarrying operations focus attention on blasting operations as a critical component in the overall cost-effectiveness of quarrying. Generally, optimisation of blasting has been linked to the processes of drilling, explosive consumption, secondary breakage, and product haulage to the primary crusher. This approach gives no consideration to the impact of primary crusher feed size distribution on downstream processes, or on the quality (ie shape and strength) of the final product. Blasting operations can be manipulated to produce a wide range of muckpile size distribution. This paper presents the results of studies into the impact of muckpile fragmentation on downstream crushing and screening operations, and includes measurements of primary blast oversize and muckpile fragmentation, together with measurements of size distribution, circulating loads and flakiness for various process streams throughout a quarry processing plant. This paper is an extension of other studies investigating the prediction and control of fragmentation from blasting, and the role of explosive performance in controlling muckpile fragmentation.

Jan 1, 1995

By Saghafi A

Spoil piles are produced routinely in open cut coal mines. Spoil piles may contain waste coal and other carbonaceous horizons. Coal and carbonaceous materials react with oxygen in the atmosphere, producing heat. If the rate at which heat is generated is greater than the rate at which heat can be dissipated, the temperature of the spoil pile rises. If the heating remains unchecked, spontaneous combustion can occur. Spontaneous combustion poses significant safety, environmental and economic problems if it should become established in spoil piles. Using the basic features of self heating in spoil, the use of model is directed toward developing quantitative prediction of spontaneous combustion in open cut coal mine spoil Piles.

Jan 1, 1998

The Central West of New South Wales is emerging as a significant metallogenic province. The development of Northparkes Mines (North Limited) and the Cadia Hill deposit (Newcrest) are establishing NSW as a highly prospective porphyry copper-gold province. Exploration in the area has been further buoyed by the Ridgeway discovery by Newcrest near Cadia. The fact that the Ridgeway prospect was discovered 300 m below surface under Tertiary basalt cover indicates that surface prospecting can no longer be considered alone as an adequate method to find significant new deposits.

Jan 1, 1997

By Merwin RA

The recent development of rare earth permanent magnets has revolutionised the field of magnetic separation. The advent of rare earth permanent magnets in the 1980s provided a magnetic energy product an order of magnitude greater than that of conventional ferrite magnets. This has allowed the design of high-intensity magnetic circuits operating energy free and surpassing the strength and effectiveness of electromagnets. New applications and design concepts focusing on the mineral and metal processing industries have evolved. This technology also led to the development of various magnetic separators specifically designed for mineral processing applications. Applications which were not previously considered are now being applied to primary mineral upgrading and recycling and secondary recovery.

Jan 1, 1993

The Northwest Territories (NWT) of Canada has emerged as a major new province for diamond mineralisation in less than three years. This is primarily the product of a diligent search in the form of a scientifically based exploration effort. However other factors, including positive aspects of the business and the legal environment have also been identified as assisting the exploration process. In my view these have increased the likelihood of diamond mining becoming a major new industry for Canada. The supportive role of various government agencies has been important. In addition, the character of many of the joint venture deals that have been done has provided an attractive setting for the capital intensive evaluation and development work that is now required to bring the diamond discoveries into production. Perhaps of equal importance is that with the recognition that is being given to the success of the NWT diamond ventures, Canadian explorers are continuing to attract new risk capital for further exploration. This paper attempts to model and quantify the probability of exploration success translating into successful mine development.

Jan 1, 1994

By Ueki S

Underground coal gasification (UCG) is a promising process for obtai- ning energy from coal, which is either unmineable with current mining techno- logy or uneconomic to recover, using conventional methods, in the present energy market situation. There are several coal fields, which could become new coal reserves, if the UCG process were successfully applied. In the 1960's Japanese researchers made a number of basic studies and field tests into UCG, although not all of them produced favourable results. This paper reviews Japanese research on UCG. This includs basic studies into coal gasification using a small, tube reactor fed by air and oxygen, and also large scale model stu- dies(reactor size of 8.Om x 2.4m x 1.5 m). Field test results from Akabira colliery in Hokkaido and a feasibility study of power generation using UCG from a coal field in Hokkaido are also Presented.

Jan 1, 1987

By M Miller

Operators of nickel laterite pressure acid leach and gold pressure oxidation technology frequently employ a series of steam condensing heaters to preheat the leach feed slurry. The heaters are an economic pinch point û although the thermal performance of the heaters is critical to overall process viability and operating cost minimisation, they are also a significant capital item and must be sized accordingly. Despite this, discussions of the factors underlying heater design are conspicuously absent from technical literature, and existing operations feature a conflicting range of heater sizes and configurations. This variety would suggest that at least some of the chosen heater designs are oversized. As part of its detailed design stage, the Ravensthorpe Nickel Project (RNP) constructed and tested a pilot plant heater to develop an understanding of the heating process and to ensure that the RNP heaters were appropriately sized. This testwork used RNP slurry at design density and viscosity on a 450 mm diameter, 6500 mm high column. The pilot plant testwork demonstrated the intrinsic efficiency of the direct steam condensation heating process, which was essentially independent of slurry density and viscosity. Presence of non-condensable gases in the steam phase decreased the heat transferred in certain circumstances, but heater performance remained consistent with thermodynamic limitations. Stagewise heat transfer within the column was rapid, and suggested either a very high slurry surface area or excellent heat transfer within the slurry phase. While the testwork did not set out to distinguish between these effects, physical evidence pointed to droplet formation in the inter-tray shower zone, giving a high heat transfer area. For scale-up purposes, the key facts were that the heat transfer rate was not limited by using high viscosity slurries and heaters could be designed using the principles applied to the smaller of those in existing operations. This paper discusses existing slurry heater designs, the current understanding from open literature, the pilot plant testwork, results and analysis, and scale-up to commercial sized equipment.

Jan 1, 2005

By Hodges D. A

The manufacture of steel from raw materials which have to be mined, transported and processed must affect the environment. Steelmaking, like almost every other stage of manufacture involves the unwanted production of dust and fume; thus a major part of the steel industry's effort to minimize changes to the environment is the collection, treatment and recycling of dust and fume to avoid pollution of the atmosphere and waterways. The paper describes how this achieved in the various steelmaking processes and shows the diversity of problems-and their solutions in this context. Particular emphasis is, given to basic oxygen steelmaking.

Jan 1, 1976

The major copper orebody at Mount Isa is being extracted at a rate of four million tonnes per year. The method used requires an equivalent rate of back filling with (mainly) cemented fill. There were three major incentives for developing this mining system. The first was the prospect of high ultimate recovery of the orebody. The target is 100% recovery. Also the proposed stoping layout appeared to offer significant advantages in development and production costs. Finally, extensive subsidence above the northern end of the orebody could have disturbed permanent surface installations and jeopardised a possible future open cut. The full implications of this ambitious strategy were not apparent in the early years. Now, after twelve years of production the benefits are being realised and they can be weighed against the costs. Probably the most interesting result which comes from this analysis is the significance of cutoff grades and dilution factors in balancing mining and filling rates.

Jan 1, 1980

A narrow (200-300m) zone of amphibolite facies metamorphic rocks underlies the Papuan ophiolite near the Musa-Kumusi divide, SW of Popondetta, Oro Province. The amphibolite rocks are bounded up-section, to the NE, by peridotite and gabbro of the ophiolite; and down-section, to the SW, by mafic greenschist, which in turn overlies blueschist facies mafic schists of the Emo Metamorphics.Amphibole compositions within the narrow contact zone show a strong chemical zonation which reflects a steep thermal gradient, with maximum temperatures >800¦C at the peridotite contact. The zonation is recorded in Ti content and A-site occupancy, relative to Al'¦

Jan 1, 1994

Ore Reserves estimation for the two producing copper orebodies at Isa Mine, Mount Isa, Queensland is discussed. The principal estimation techniques used and discussed are first, a computer based inverse power distance weighted assay meshing technique, and second, a manual arithmetic averaging technique. The principles involved in these techniques are compared, and their areas of application indicated. A general comparison of the estimation of reserves with eventual production is presented.

Jan 1, 1979

Traditionally, surface coal mines in the Western United States have been limited by economics to depths between 150 to 200 feet. Utah International Inc., however, is now planning to strip coal its San Juan Mine in Northwestern New Mexico to depths ranging up to 400 feet while uncovering 20 feet of steam coal. This method is cost-competitive with nearby shallower coal deposits and underground mining of the same property. How trucks and shovels can pre-strip for a dragline, along with results of the planning process, comparison with alternate systems, capital requirements, operating costs and comparisons with other coal sources are all detailed. Also discussed are the major problems anticipated, how they might be corrected, and potential improvements to the concept. Introduction The San Juan Deep Stripping Project will be situated at Utah International's San Jean Mine. The mine is in the Four Corners region, so-called because four states enjoy a common border point about 30 miles to the northwest.(see Figure 1). The area is a semi-arid plateau region with an average elevation of 5,200 feet, receiving an average of 6 inches of precipitation annually

Jan 1, 1981