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By D R Van Eck

Western Deep Levels, a seismically active deep level told mine. stalled placing backfill in their narrow tabular workings as part of the regional support strategy in 1986. Over the years the percentage of working places being backfilled has been gradually increasing. At the end of 1995 the support efficiency and the labour productiveness relating to support installation were scrutinised to determine if resources were being optimised. Owing to financial, safety and productivity constraints it was decided to redesign stope support to be less labour intensive, safer and provide an integrated stope support system. This new integrated system will thus combine the previously used temporary, permanent and back area support consisting of mechanical props, hydraulic props and backfill respectively. Backfill previously formed an integral part of the regional support in conjunction with strike stabilising pillars. To design the integrated support system the backfill placement quality has to be exceptionally good and placement must be done as close as possible to the working face. The backfill to face distance was reduced by 30 per cent and in some areas by more than 50 per cent with an increase of square metres filled to increase the effect of the backfill even more. This paper addresses the design and successful implementation of an integrated stope support system based on the optimisation of backfill to he extent where installation of mechanical and hydraulic jacks could he Eliminated

Jan 1, 1998

The Southern Mines Rescue Station (S.M.R.S.) has been established for 55 years and in the past 15 years has had only 4 major call-outs. Whilst the mines rescue training program has continued to expand, the Station has become involved in other work which includes mine worker training and limited research. Notwithstanding, the prime role of the Mines Rescue Station has not been overlooked and the Station has only advanced with the many changes that have occurred in the coal industry. The Rescue Station activities are financed by contributions from Colliery proprietors and the aim of the S.M.R.S. Committee is to provide a service in which colliery management and mine workers will have a high degree of confidence.

Jan 1, 1981

Western Deep Levels, a seismically active deep level gold mine, started placing backfill in their narrow tabular workings as part of the regional support strategy in 1986. Over the years the percentage of working places being backfilled has been gradually increasing. At the end of 1995 the support efficiency and the labour productiveness relating to support installation were scrutinised to determine if resources were being optimised. Owing to financial, safety and productivity constraints it was decided to redesign stope support to be less labour intensive, safer and provide an integrated stope support system. This new integrated system will thus combine the previously used temporary, permanent and back area support consisting of mechanical props, hydraulic props and backfill respectively. Backfill previously formed an integral part of the regional support in conjunction with strike stabilising pillars. To design the integrated support system the backfill placement quality has to be exceptionally good and placement must be done as close as possible to the working face. The backfill to face distance was reduced by 30 per cent and in some areas by more than 50 per cent with an increase of square metres filled to increase the effect of the backfill even more. This paper addresses the design and successful implementation of an integrated stope support system based on the optimisation of backfill to the extent where installation of mechanical and hydraulic jacks could be eliminated.

Jan 1, 1998

The maintenance system for underground mobile equipment at Cobar Mines Pty. Ltd. has been modified from that originally planned as a result of experience gained in operating the equipment.Downtime due to breakdowns has been reduced by improvement of vehicle servicing and overhaul procedures.Frequency of breakdowns can be reduced by training operating and maintenance personnel to a high standard, ensuring adequate numbers of tradesmen and supervisors, good maintenance facilities and communications, a well designed mine layout, and a comprehensive stock of spare parts.A maintenance and downtime summary is compiled for each four-week operating period and this is useful in highlighting particular problems where corrective action must be taken.

Jan 1, 1969

By Whiten W. J

Data from ball mills of a wide range of sizes are analysed using detailed mathematical models and non-linear least squares fitting techniques. In this way model parameters are obtained describing the behaviour of ball mills over a wide range of mill sizes and operating conditions. These parameters define the flow and breakage of each size fraction of ore in the mill. Flow of coarse particles through the mill is found to depend on the proportion of coarse particles present. The breakage rates of coarse particles are found to decrease markedly with mill diameter for mills over 3 m in diameter.Simulation of grinding circuit throughput at constant productsizing for different mill diameters shows that throughput is proportional to theoretical mill power consumption for mills up to about 3 m in diameter. Thereafter the throughput gradually falls below that indicated by power consumption, the decrease becoming quite significant for large diameter mills. Simple qualitative physical arguments are presented to explain this behaviour. The models developed have applications to ball mill scale up. Work on their further development is continuing.

Jan 1, 1982

By D M. Weedon

This paper introduces a novel roll crusher design, which incorporates non-cylindrical crushing rolls. The use of non-cylindrical rolls enables the crusher to achieve a greater reduction ratio than is possible with conventional roll crushers. Referred to as the NCRC (non-cylindrical roll crusher), the new crusher incorporates two rolls comprised of an alternating arrangement of plane and convex or concave surfaces. The two rolls are complementary and arranged so that when they rotate the convex and concave surfaces of each roll are substantially opposed. With the rolls rotating in opposite directions at the same speed, this arrangement produces a gap between the rolls that remains approximately constant. Discontinuities on the roll surfaces provide improved angles of nip, which increase the probability of larger particles being drawn into the crusher. Initial tests on a scale prototype of the NCRC have indicated that reduction ratios exceeding 10:1 are achievable.

Jan 1, 2000

By L Smith, R Beckie

An intermediate scale (8 m + 8 m + 5 m high) constructed waste rock pile experiment was built upon a contiguous grid of 16 gravity drainage lysimeters to investigate the flow of water in unsaturated waste rock. Average net infiltration to the uncovered waste rock pile is 55 per cent of precipitation. Large rainfall events have net infiltration of 55 per cent to 85 per cent. Net infiltration estimates range from 23 to 120 per cent of precipitation between lysimeters. Small-scale lysimeters of less than 4 m2 area are shown to be poor predictors of net infiltration for uncovered waste rock. The appropriate size for lysimeters increases with increasing flow rate. The residence time distribution has an estimated median value of 3.0 to 3.9 years under average infiltration conditions. Water flows within the fine grained matrix, within larger pores (macropores), and in matrix free areas of the pile. In situ tracer concentrations vary between pore sizes, and between spatially distinct areas of the pile, indicating water geochemistry may also be variable. Water samples collected from in situ soil water samplers are dominated by the most mobile water fractions. In situ measurements of water content and matric suction are compared to the measured outflow. The data indicate the focusing of flow in spatially distinct areas can make in situ instrumentation a poor (non-conservative) predictor of volumetric water flow.

Jan 1, 2003

By Godresse M, Turczynski G. P J, Driver I. J, Low G, Ozawa N

Geological evaluations of coal deposits have been traditionally undertaken in a somewhat manual manner. Information is collected downhole by chip sampling, coring and using downhole geophysical logging. This information is then interpreted by an experienced geologist to define the coal and noncoal lithological units. Coal units were subsequently correlated to provide data for structural modelling. In recent years a number of advancements in interpretation techniques have been made based on Artificial Intelligence. This paper describes an integrated geological interpretation system based on maximised use of Al techniques. The first part describes the lithological interpretation which uses a number of boreholes with both logged lithology and downhole geophysical logs. This information provides a learning set of data to the neural network. The second part concentrates on the correlation of both coal and noncoal units from borehole to borehole. Problems in this area, in a manual sense, are interpretation of correlation across weathering zones and other geological anomolies. The technique is based on pattern recognition and dynamic programming techniques where a correlation matrix is developed relating all holes with their maximum correlations.

Jan 1, 1995

The Hunter Fracture Zone can be traced into the Fiji group, and onshore SE Viti Levu in the form of NE-trending morphostructures. NW- trending morphostructures offset the NE elements. Structural mapping of Suva Harbour indicates that the NE elements are grabens bordered by faulted monoclines. Faulting is characterised by block-rotations and dip-slip displacements. The NW morphostructures are faults displaying elements of both dip-slip and strike-slip movement. Structural overprinting suggests that the NW faults represent the youngest phase of deformation, and current seismic activity occurs on this trend. A conceptual, geomechanical model of the deformation invokes toppling and wedge failure at the edge of the Fiji platform, translating material downslope into the Hunter Fracture Zone. The interference pattern produced by the superposition of the NW on the NE structures consists of a series of circular features bearing superficial resemblance to volcanic centres. Known mineral deposits in SE Viti Levu correspond closely to these features. The formation of the circular features postdates mineral genesis, suggesting that the features provide a focus for the enhanced exposure of mineral deposits rather than a source of mineralisation. There is a close association between mineralised exposures and interference patterns in extensional structures in SE Viti Levu, and a correlation between these structures onshore, and the Hunter Fracture Zone cum South New Hebrides Trench offshore. Future mineral exploration in the SW Pacific will benefit by closer consideration of the geologic structure of Pacific islands bordering the extensional regimes of deep oceanic trenches.

Jan 1, 1987

By Glastonbury J. R

Commercial operation of the Sherritt Gordon process in Australia for the leaching of nickel sulphides has promoted an investi- gation of the factors which influence extraction kinetics. This portion of the investigation has been directed towards the physical and chemical nature of the concentrate and the physical evi- dence of the mode of extraction. Details of the particle size distribution, mineral composition and chemical composition are given. The dis- tribution of various minerals in different size fractions and magnetic fractions is discussed. An electron microprobe was used to determine the composition of individual grains in the concentrate. The solid residue from an ammonia oxi- dation leach was subjected to microphotograph- ic examination, X-ray diffraction analysis and scanning by an electron microprobe. Clear evidence was obtained for a shrinking core mode of kinetic extraction with an amorphous iron oxide product layer contrary to previous reports that the latter is pseudomorphic with the original mineral.

Jan 1, 1973

By Jacobsen L. K, Gross K. B

This paper, describing milling practice at Mount Isa Mines, is one of a series covering milling methods and costs that is being published by the Bureau of Mines, United States Department of the Interior.The Mount Isa concentrator began operations in May 1931, by treating a mixture of oxidized and sulphide ores. Since March, 1935, only sulphide ores have been milled; this change involved major alterations to the flow sheet. The maximum capacity on mixed oxide and sulphide ores was 2,650 tons per day; the present capacity is approximately 1,880 tons of sulphide ore per day. The installation of additional Grushing, grinding, and flotation equipment when completed early in 1939 will increase the maximum capacity of the concentrator to 2;240 tons of sulphide ore daily.All tonnages in this paper are expressed in tons of 2,000 pounds, gallon measurements in terms of Imperial gallons of 277·41 cubic inches, and costs in dollars at the rate of $4 United States currency to the Australian pound.

Jan 1, 1939

By Paine G. G

The Red Dome Gold/Copper Mine is located approximately 15 km west of the township of Chillagoe which itself is approximately 220 km by road west of Cairns, Far North Queensland. The deposit, with other mines in the Mungana region, was worked from about 1901 to 1927. Exploration by Amoco Minerals Australia in the 1970s and early 1980s outlined a geological resource of 15 million tonnes. A mining reserve of 9.3 million tonnes was identified and originally developed by Elders Resources Limited. The mine commenced operations in March 1986 and was the first large-scale gold project in Australia to be developed solely on the heap leach process. The mine operated successfully as a gold heap leach operation until 1989 when new grinding, flotation and carbon-in-leach plant facilities were installed to process the non heap-leachable component of the orebody including the copper rich -ore. In March 1991, Red Dome Pty Ltd became a wholly owned subsidiary of Niugini Mining Limited. After six years of successful operation and having excavated a 200 in deep pit, it became evident in 1992 that unless more open cut reserves could be identified the operation was limited to six to nine months of high grade ore and a further 15 months of low grade stockpile material. A preliminary feasibility study was carried out to assess the viability of deepening the open cut. This indicated that from a technical and financial point of view it was possible to expand and deepen the open cut. This presented the daunting challenge of developing a 300 in deep, single access, open cut between a high chert ridge, a government railway line and a National Park. The meeting of this challenge is the subject of this paper.

Jan 1, 1994

At moderate depths this question is of relatively small importance, but at depths over 2,000 feet it becomes a matter of some consequence. The rate of increase of temperature with the depth varies in different localities, but as a rough average we may take it to be about 1° Fahr. for every 50 feet of depth. The variation of temperature of the earth's surface from summer to winter penetrates to a comparatively shallow depth. At 50 feet the variation becomes practically insensible, and the temperature of the strata will be about the mean temperature at the given locality, from 60° to 75° F. in this country or the comfort of men working in the mines it is desirable to maintain a temperature of about 70° F. in the workings, or approximately the temperature of the strata near the surface.In order to obtain some idea of the magnitude of the undertaking involved in cooling a mine, I have examined the effect of placing in a long drive an apparatus by means of which we can abstract heat at a uniform rate from the drive, keeping, thetemperature nearly the same at all points of the drive at any given time.The lowering of temperature 70 F. at any distance feet from the centre of the drive (treated as a cylinder of the same sectional area as the actual drive), after an interval of time days from the commencement of the operation is given by the formula...

Jan 1, 1907

By E Villaescusa, C Drover

The stability of access tunnels is one of the main engineering challenges in deep underground mine construction. Many underground hard rock mining operations are now reaching depths where the induced stresses are such that sudden and violent failure of the excavations can occur very soon after construction. The loading conditions on the installed ground support schemes are often underestimated by conventional engineering design methods. Therefore, the actual loading conditions often exceed the installed ground support capacity. This can result in failure of the excavations and, in extreme cases, potentially closure of mining operations amounting to hundreds of millions of dollars in lost production. More frequently, violent excavation instability at great depth causes operational delays, costly and unplanned rehabilitation, as well as risks to worker safety. In order to address this challenge, this paper briefly summarises a modern, innovative approach to the design and construction of mine development at great depth. The process follows seven main steps. The first step is to characterise the rock mass strength, structure and stress. The second step is a stability assessment, which identifies the plausible modes of excavation failure, based on the rock mass characterisation. The third step is the definition of an excavation geometry which is harmonic to the high stress conditions. The fourth step is to prepare a site-specific face destressing drill and blast design which will reduce the potential for rock mass instability during the development construction cycle. The fifth step is to accurately quantify the expected loading conditions on the installed ground support. The method of doing so is uniquely analytical and probabilistic. It is based on the natural mechanical relationships between rock strength, structure, induced stress and the physical characteristics of the instability, including its mass and ejection velocity. The sixth step of the design process is to specify a ground support scheme arrangement with sufficient strength and displacement capacity to exceed the rock mass demand by a safe margin. The final stage is to install the complete ground support scheme using mechanised technologies which minimise the exposure of the equipment operators to unsupported ground at the tunnel face.

Nov 29, 2022

By S Bandopadhyay

The seasonal fluctuations of the dust content in Arctic mine environments and the environmental variables affecting the intensity of dust production are qualitatively well known, but quantitative models that allow simulation and prediction of dust generation and the effects of engineering control of thermal regime on the mine environment are still non-existent. In Arctic mines, the migration of moisture in the surrounding rock mass releases fine dust by freeing it from the ice matrix allowing it to escape into mine airway. The migration of moisture is the direct cause for the production of mine dust and heat is the primary driving force. This paper examins the heat and moisture exchange between the ventilation air and the surrounding rock mass in frozen ground, placer mines in the Arctic. Based on the simulated results of a coupled heat and mass transfer problem with phase change, methods of dust control have been identified for mines in the Arctic.

Jan 1, 2005

Although the flotation cell has been under continuous development over the past 80 years, an understanding of the precise roles of a cell in produc- ing the flotation result had evolved slowly. In fact, detailed studies of cell dynamics began only in the 1940s when flotation practice had almost reached the half-century mark. The earliest generalizations related cell capacity to power intensity (hp/vol- ume) (Rose, 1946), and specific operating features such as aeration and power ' consumption to impeller submergence and operating speed (Read, 1933). In the 1950s hydrodynamic characterization of cells through power coefficients and air flow numbers began (Arbiter and Harris, 1961) and has continued to the present, with increasing industrial use of these concepts (Degner, 1982; Degner and Treweek, 1976). Liquid flow measurements in Wemco cells (Degner, 1982) made liquid flow numbers and turnover frequencies available for more complete under- standing of cell dynamics. The present overview of flotation technology is a critique of cell design. The cell process represents the interactions between cell dynam- ics, cell geometry, and ores, with the latter prepared for that interaction through size reduction and reagent treatment. While previous invest- igations of flotation cells have accepted all cell designs uncrit- ically, the present study considers the physical process components that an effective cell must provide, and then compares a limited number of

Jan 1, 1984

Economic and technical reasons forced the mining industry all over the world to increase the unit size of mineral processing equipment. in large flotation cells, this development leads to problems in areas of air dispersion and keeping solids in suspension. Outokumpu, an operating mining company, designed and developed a mixing mechanism for large flotation cells at its own concentrators and also studied problems related to tank design. Ideal conditions for flotation can only be achieved if the flow pattern created by the mixing mechanism fits well into the tank configuration and the risk of short circuiting is minimized. In large deep flotation cells, four different zones can be found which improve the behaviour of large cells when compared to small cells. Selectivity is increased and in some cases final concentrate grades can be produced from the rougher cell. The largest units have also been used as final cleaners in some installations. When modernizing old plants by installing fewer larger flotation cells, immediate and substantial savings in power consumption are achieved. Additional power savings are made in pumping costs because of simpler circuit design and decreased circulating loads

Jan 1, 1978

Segregation studies in ternary systems of glass ballotini, iron ore and coke particles (with size range of 1-8 mm in each) in filling and emptying a laboratory size Paul Wurth hopper are described. In-bin segregation is shown to be a function of the position in the hopper, the nature of the material and the feed composition. The in-bin results are correlated by the equation C = C0k, where C and C0 are the size compositions (wt per cent) in the hopper and feed respectively, and k is an experimentally obtained segregation constant. The results of now pallern measurements show that material discharges from the hopper according to the sequence; core now - wall now - scaffold now, where the latter represents stagnant material at the hopper wall that discharges last. Size segregation in the discharge stream from the hopper is shown to be a function of in-bin segregation and hopper now pallern. A method of predicting discharge segregation from these two sets of data is suggested. The results of the model studies are also compared with industrial data and these show satisfactory agreement. Discussion of the hitherto ignored effect of size segregation on hopper now rates, stoppages and other operating problems is also included.

Jan 1, 1985

By Bell LC

Overburden removal, mining and reclamation are now accepted as the basic operational steps involved in the winning of coal by open cut methods. To attain the lowest operational cost, the recontouring and revegetation of spoilpiles must be planned concurrently with the planning of overburden removal and mining. The earthworks associated with reclamation work on spoilpiles often account for 75 - 90 per cent of total reclamation costs. Experience at Callide Mine has shown that the way that spoilpiles are contoured does influence water retention and can reduce erosion from rainfall run-off. However, provided the recontoured slopes meet'Mines Department specifications, the quality of reclamation work is judged not by the quality of the earthworks but by the plant regrowth on the reshaped surface. Thus it is the quality of the revegetation which is of prime importance. For vegetation to be successful, time must be spent on planned research into methods of overcoming plant nutrient deficiencies and selection of suitable grass and tree species. The research programme undertaken at Callide Mine consists of three stages :- laboratory studies glasshouse trials field trials

Jan 1, 1978

When a thin film of volatile matter is deposited under vacuum on a polished coal surface, and the coated surface is examined microscopically in piano--polarized reflected light, colour changes are observed characteristic of the various macerals present. The colour changes appear to be mainly due to interference between light reflected at the upper surface of the film and at the film/coal interface. A variety of source materials for the volatile matter required have been tested, including powdered bituminous coal, coal tars, boron oxide, and certain resins.

Jan 1, 1969