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The optimum plant capacity for a new mine is usually based on empirical studies or ærules of thumbÆ, subject to confirmation by detailed scheduling of the proposed mining operation. The mining industry has a record of poor returns on investment and a high rate of project failure using these methods, with under-performance in grade being a common experience. The assumption that æeconomies of scaleÆ will result from increasing throughput rates needs to be balanced by an awareness of the adverse effects of increasing the rate beyond a level that issupportable by the resource. For each scale of operation considered, it is a reality that for any intended head grade, at the associated intended cut-off grade, the actual head grade achieved will fall as the mining rate increases. This effect is known to people at operations but is not recognised in current ore reserve estimation methodology. Once recognised, this dependency of head grade on mining rate can be quantified and used to establish the economically optimum mining and processing rate for a new project. A simple analysis is proposed, which may be extended to detailed spreadsheet modelling for financialoptimisation.

Jan 1, 2002

By R Young

Independent Project Analysis (IPA) is in the business of benchmarking the performance of capital projects on behalf of owner companies in the processing and extractive industries. IPA assesses between 500 and 800 projects each year. The projects are conducted globally and range in size from about $1 million to over $30 billion. Using the data, we are able to benchmark the performance of Australian projects against the rest of the world. This presentation focuses on the performance of large (greater than $100 million) projects that involve chemical or thermal processing.We regularly hear calls for more processing to be conducted in Australia but on the other hand industry leaders are concerned about the poor success rate of solids processing projects in Australia. Data gathered by IPA indicates that there is good reason for the concern. Out of a sample of 31 large processing projects conducted in Australia, 23, or 74 percent, were classed as failures. This performance is significantly worse than for similar projects in other parts of the world. The presentation analyses why the performance is worse and demonstrates that many of the reasons behind the failures were manageable by the project team. Furthermore, members of the project teams on at least half the failed projects knew that the projects were on a path to failure before the project was authorised but could not be heard.The presentation discusses how large projects that involve process design and, in many cases, new technology, need to be set up for success. *This is an abstract only. No paper was prepared for this abstract.*

Aug 8, 2011

By E J. B van Etten

Pit lakes may form when open cut mining leaves a pit void that then fills with ground and surface waters. This often replaces terrestrial ecosystems that existed prior to mining with an aquatic ecosystem, affording an opportunity to improve regional aquatic biodiversity values through targeted aquatic restoration (McCullough and van Etten, 2011). Restoration theory provides guidance when restoring disturbed systems towards landscapes that are of regional value and relevance. But how do we identify a restoration target for a novel aquatic habitat that only exists in the new post-mining landscape? This paper presents a process of first identifying and then surveying local representative aquatic systems, to provide a direction for pit lake restoration efforts and achievement criteria for pit lake relinquishment, using a case study from a sand mining operation amongst wetlands in south-western Australia.The company mines silica sands following mechanical removal of topsoil and then extraction of the ore from below the watertable by dredging. Assessment of wetland and riparian vegetation was achieved through the establishment and measurement of temporary monitoring transects across five natural wetlands in the Kemerton area. Several more regional wetlands were also visited and observations made to supplement and validate these data.Distinct vegetation zonation was found across each wetland, although typically wetland basins were unvegetated or filled with younger woody plants with patchy distributions. Fringing riparian vegetation consisted of few species (commonly the paperbark Melaleuca rhaphiophylla and the sedge Lepidosperma longitudinale), but community composition and structure were variable between wetlands. The pattern of vegetation seen across natural wetlands was best explained by topography and soil chemistry, with low lying wetland areas more likely to experience regular flooding and accumulate organic matter and nutrients.In conclusion, where they are available, regional natural waterbodies may constitute the best valid restoration goal. Nevertheless, the goal may need to consist of a range of closure design opportunities, rather than a single target.

Oct 5, 2011

The Yanacocha district hosts the largest and most significant acid-sulphate, high-sulphidation deposits in Per· with total production, reserves and resources of over 27 million ounces of gold. Several other smaller high-sulphidation systems are also recognised in the Cajamarca region including La Zanja, Sipßn, Tantahuatay, and San Nicolas. These each have reserves/resources of between 640 000 and 800 000 ounces of gold. Gold deposits in the Yanacocha district are hosted in an extensive volcanic field. Flow domes have intruded precursor pyroclastic rocks and flows that are interpreted as part of an earlier intermediate multi-vent volcanic complex. The larger, contiguous Yanacocha Norte - Sur and Encajon gold deposits are spatially associated with late-stage diatreme breccias. At La Zanja extensive acid-sulphate alteration is associated with the margins of the small San Pedro caldera (6 +4.5 km), nested within the larger, less well-defined La Zanja caldera (19 +24 km). The inner caldera is resurgent with abundant magmatism expressed as several flow dome complexes located on the caldera rim, and shallow level intrusive stocks. Gold mineralisation is associated with a WNW-trending structural corridor that transects the southern margin of the San Pedro caldera. On the eastern side of the La Zanja caldera there are a series of younger andesitic eruptive centres, some associated with acid-sulphate alteration and gold mineralisation. The Sipßn deposit occurs in one such centre with structurally-controlled gold associated with a NE-trending silicified structure developed within a sequence of andesitic tuffs. In conclusion, although a number of high-sulphidation deposits are recognised in northern Per·, their settings and styles of mineralisation are all quite different. Smaller deposits generally have strong and obvious structural controls. In the larger Yanacocha deposits the structural controls are less obvious, and mineralisation is disseminated in porous or strongly fractured and brecciated silica. Erosional levels are probably a significant factor, with disseminated mineralisation at higher levels, and structurally-controlled mineralisation in more deeply eroded deposits.

Jan 1, 1999

The Malvern Hills coal project is now in an advanced stage of development with the stripping of overburden from above former underground workings in which a 3 m seam of subbituminous C coal with very low ash and sulphur was previously mined. The main seam dips at 45¦ to the south-east, along with other adjacent potentially recoverable thinner seams, and the strike extent of past coal mining in the Malvern Hills approaches 10 km with most extraction by underground methods. Overburden and interburden is predominantly weak mudstone, with only very minor sandstone, whilst a 1 - 2 m thick veneer of Last Glaciation loess covers the area. The coal product from the present mine site will supply the local industrial market, with production planned to peak at about 20 000 tpa. Settling pond design has been based on several different approaches, including an estimate of likely inflows from the contributing catchment of about 5 ha under predicted storms having a ten year recurrence interval. A pond of about 1000 m2 in area has been constructed with its invert in mudstone bedrock, and soil slopes have been lined with lime-stabilised clayey loess silt incorporating a gravel armour layer. The pond outflow takes place via a 2 m high 1.8 m diameter concrete dewatering tower, with a skimmer arrangement to lower the pond by approximately 500 mm between storm events. The overflow water discharges to the main stream above a natural wetland, which will act as a secondary polishing pond, and this is to be enhanced in conjunction with the neighbouring forestry company. Discharge consents specify turbidity and pH as the controlling criteria, and both will be monitored at the settling pond discharge point as well as at the entry to the main stream. Investigations to date indicate that the pH of water exiting from previous underground workings is in the range 6.8 to 7.2, and that acidic drainage will not be an issue with this mine site. No dispersive clays have been identified in assessing the overburden and batter materials, although erosion during storm events is expected and all drains will ultimately be routed through the main settling pond to ensure adequate control of runoff-generated sediment. Reestablishment of vegetation on cut and fill batters remains a priority, and ongoing monitoring will ensure satisfactory long-term performance of the pond system.

Jan 1, 2003

By J F. Seale

The design of the settling pond for the Malvern Hills opencast coal project was based on a primary requirement to control runoff and sediment generated from the immediate 6 ha mine catchment, which included two seepages from old underground workings. The pond has been particularly effective in controlling turbidity in the outflow water, with the consent limit of 50 NTU being met on all but one occasion and normal levels of discharge less than 10 NTU. Water quality testing carried out at the time of consenting indicated that there were no acid-generation issues with the proposed mine site in dominant mudstone strata of the Broken River Formation, and that water from the old mine workings was near-neutral in terms of pH and well-buffered. However, it became apparent over the very dry summer of 2003 - 2004 that slaking of the exposed mudrocks in the mine batters was resulting in significant acidity generation, and outflow pH levels were well below the consent limit of 6.5 during and following periods of rainfall. Although these acidity problems have been remediated in the short-term by the use of lime products, it is clear that a programme of lithotype characterisation for AMD should have been undertaken and this has now been implemented. Design of long-term acid drainage control measures is being carried out, and will probably be based around the use of hydrated lime for pH control with enhancement of natural wetlands.

Jan 1, 2004

Hindered settling devices (teeter bed, up-current) are widely used in the mining industry to classify mineral streams into various size fractions and to separate minerals. In the coal industry these devices are extremely successful in separating coal of low densities from shale and pyrite. In the beach sand and in the iron ore industry, this equipment is used to beneficiate minerals either as stand alone units or lately as classifiers in spiral circuits. The challenge that these applications give to metallurgists is to be able to simulate the equipment by using mathematical models with or without the aid of small bench scale tests. In any green fields and many brownfields projects, limited amounts of samples make pilot plant tests difficult. Although there are mathematical approaches available, the accuracy is of such a nature that it can not be used for design purposes. This refers to the use of StrokeÆs law, NewtonÆs and the so called intermediate law as is widely published. Research done by the author indicates that in most applications none of the above laws apply. Using the original data as published by Perry and Chilton (Chemical Engineering Handbook, pp 5-64, 1973) and re-plotting it indicates that the settling velocity of particles is a function of (particle diameter)n where n varies between 1.2 and 1.6 which is different from that predicted by the intermediate law that suggests that n = 1.18. Another way of describing the relationship between the drag force and the Reynolds number is done by iterating between settling velocity and the Reynolds number. This needs more computer time but the accuracy obtained from this does add value to simulations. A small but simple test is suggested to determine the settling velocity of particles to enable metallurgists to determine variations from the theoretical calculations to determine the influence of viscosity and particle shape.

Jan 1, 2008

Several Approaches to Enhance the Bioleaching of Enargite Some approaches were investigated to enhance the recovery of Cu from enargite by bioleaching with Acidithiobacillus ferrooxidans using the galvanic interaction with pyrite and activated carbon, and with thermophilic bacteria, Acidianus brierleyi. Addition of pyrite initially enhanced Cu leaching by the Galvanic effect, but after that the formation of secondary minerals passivated the surface of enargite in inoculated batches. Activated carbon improved Cu recovery from enargite much better than pyrite, when it is contacted with enargite. Recovery of Cu from enargite has been recorded to at largest 2.4 per cent within 30 days in the presence of activated carbon when mesophilic bacteria were inoculated at 25¦C. The recovery of Cu from enargite was drastically enhanced by inoculation of thermophilic bacteria, Acidianus brierleyi, up to 60 per cent within 40 days at 70¦C and still not leveled off after 40 days unless the formation of Fe(III) precipitates occurred. After 40 days dissolved molar ratio of Cu/As is around 5.2, suggesting that metal-deficient sulfides and/or ferric arsenate might be formed on the surface of enargite.

Sep 13, 2010

The city of Kalgoorlie-Boulder is located 595 kilometres east of Perth in Western Australia, and has a population of just over 30 000. Western Australia's third largest city lies on one of the richest goldfields in the world, with over 45 million ounce

Jan 1, 1998

By J Graaf, R A. Murrell

Gold Fields Australia is constructing two major ventilation shafts at the Wallaby gold mine in Western Australia. The new ventilation shafts are required to facilitate the long term ventilation strategy for the mine, thereby allowing continued extraction of ore beyond 1000 m below the surface. The construction work has involved all of the challenges that shaft construction can throw up, including challenging geotechnical conditions, unexpected high water inflows and major circulation loss during pilot hole drilling for raise boring. An extensive geotechnical and hydrological investigation program was undertaken prior to awarding the shaft construction contracts. While most of the risks were identified, several proved to be much more challenging than expected. The shaft construction methods included conventional sinking into the fresh rock profile in each shaft, followed by raise bore pilot hole drilling and reaming. A headframe was constructed for the first shaft, which was sunk to 92 m with a stage suspended in the shaft to facilitate the concrete lining and provide rope guides for the kibble winding. Drawing from experience when sinking the first shaft, additional ground pre-conditioning was implemented for the second shaft, which was pre-supported with continuous piles to 28 m followed by sinking to 50 m using a crane instead of winders and a headframe. Following the conventional sinking through the weathered zone in each shaft, the shafts were completed using a raise bore. The first shaft utilised a riser pipe and rotary vertical drilling system (RVDS) with the second shaft having utilised a dual rotary rig for pilot hole drilling. This paper reviews the site investigations undertaken, construction methodologies applied, the results achieved and the lessons learnt.CITATION:Murrell, R A and Graaf, J, 2017. Shaft construction at the Gold Fields Wallaby mine, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 321–334 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

This paper describes the excavation of No. 1 Power Station Lift Shaft at the Kiewa Hydro-Electric Project. The advantages and limitations of the borehole method are outlined, and general principles of plant design are discussed.INTRODUCTIONFor many years, attempts have been made to reduce mine development costs by various methods. Some of the, techniques of tunnelling have been adopted in horizontal headings, and in main vertical shafts, mechanical plant has displaced hand labour with notable success. However, in the field of small rises and winzes, improvements have largely been effected by attention to details of procedure. The most promising avenues for' substantial reductions in cost relate to:(a) Long-hole drilling(b) The borehole method(c) Calyx drilling.Whilst each of these methods has its peculiar advantages, the borehole rising method is probably most useful, and capable of wide application.In brief, the borehole method of rising requires a, drill hole parallel to the axis of the rise. A hoisting rope is passed through the borehole, and is attached to a platform on which the rising crew are raised with their equipment to the drilling position in the rise.When properly planned, the method is particularly safe, and has generally received the approval of mine inspectors and safety authorities. Rising work is generally hazardous, even when special timbering methods are used. In...

Jan 1, 1959

By Mercer J. K

Shaft guide reaetions in No. 2 Ore Shaft, Mount Isa Mines Limited, have been reduced to a low order of magnitude by the use of self aligning slippers and spring loaded guide rollers. Before commissioning the new 4500 h.p. winder at No. 2 Ore Shaft in January, 1958, it was realised that the increase in hoisting speed from 1800 to 2650 ft/min. would cause high shaft guide reactions which would be increased further when the elongated 12 ton skips replaced the existing 7 ton skips.The Cambridge accelerometer was used to measure the shaft guide reactions and to confirm that progressive skip modifications were resulting in reduced reactions. The skip modifications were completed in 4 weeks.INTRODUCTIONIn 1956 an expansion programme was initiated to increase production from 5000 to 11000 tons per mining day. At No. 2 Ore Shaft the 1500 h.p. winder operated at 1800 ft./min. and hoisted a 7 ton capacity skip. The new 4500 h.p. winder operates at 2650 ft./min. and hoists a 12 ton capacity skip. No. 2 Ore shaft is equipped with two 5 ft. by 5 ft. hoisting compartments (Fig. 1) and any increase in skip capacity meant an abnormally long skip. This feature, coupled with the increase in hoisting speed, could have caused very high shaft guide reactions. Before commissioning the 4500 h.p. winder, a Cambridge accelerometer was borrowed from the University of Adelaide and was used to measure the shaft guide reactions. Rather than carry out an extensive shaft timbering programme, the skips were modified by fitting cushioned guide shoes and spring loaded guide rollers (Fig. 1). Testing commenced in February, 1958, and was completed in March, 1958.

Jan 1, 1961

By Y Wu, F-J Ping

Today, coal production accounts for about 65 per cent of the nationÆs gross energy in China. By the year 2010, the output of coal is planned to increase to 1.65 billion tonnes and by the year 2020 to 1.9 - 2.0 billion tonnes. To meet these energy needs the Chinese coal industry is developing underground coal production on a massive scale. The new drive introduced by using direct torque control (DTC) is now proven technology for mine shaft hoisting. The drive offers unequalled speed and torque control performance as well as a low impact on the supply network by controlling the power factor to unity with a minimum of harmonics distortion.

Jan 1, 2005

The safety of mine winder systems with regard to overwind, underwind, rope factors of safety, winder brakes and the like is discussed. Many misunderstandings and poten- tially unsafe practices are discussed as well as variations between requirements of various Mines Departments. Various methods to improve safety are suggested and the formation of an industry committee to review present practice and foster development of improved safety and economy is also suggested.

Jan 1, 1984

Shaft sinking through an amphibolite-granite rock mass experienced rock bursts on the shaft walls and benches. However, rock burst phenomena was exhibited only in granite, which is e1asto-brittle with ability to store strain energy caused by orogenic and man made stresses. To improve ground conditions, blasting of destressing holes at shaft corners was carried out. By this technique rock burst during shaft sinking was minimized, but not eliminated.

Jan 1, 1982

In the plumbing of vertical shafts the methods employed and equipment used, are generally made to best suit existing conditions. Undoubtedly, there is no method that can be called standard or that can be used with equal ease and success on all shafts. At the Mount Isa Mines Limited property in Northern Queensland, Australia, local conditions have presented no major difficulties to be overcome in shaft plumbing work. In fact, compared to those at many shafts, the problem has been rather simple. There are three vertical shafts connecting main mine workings, with the greatest plumbing depth for any single lift, 350 ft.Other conditions pertaining to plumbing work have been generally normal.The method we have employed is, in principle, similar to the Weisbach orientation method with a variation that does not necessitate damping of the wires to bring them to rest. Although conditions encountered have not been such that damping the wires would have been inconvenient, we feel we have saved much time and eliminated unnecessary...

Jan 1, 1940

MR. E. J. HORWOOD wrote: In view of the difficulty of obtaining accurate results when using plumb lines in shafts, owing to the effect of currents of air, the writer, over M years ago, devised a method of transferring oearings from the surface to, the underground workings independently of plumb lines.An attachment was procured for the theodolite consisting of a 45° prism enabling a view of a fine line stretched across the shaft at the surface to be observed from the bottom of the shaft. The instrument was set up in such a position that.a view of the portion of the surface line could be obtained as close as possible to the shaft timbers.By candle light signals an assistant at the surface moved his line so that the portion close to the side or end of the shaft coincided with the cross wires of the theodolite. The theodolite was then swung to enable the crosswires to traverse the surface line. It was a simple matter to transfer the bearing of the surface line to points in the drive extending from the shaft. Similarly the relation of the bearing of the surface line to the shaft, with which a connection was intended, was easily obtained.The success of this method was demonstrated at Broken Hill in making connections many hundreds of feet from the shafts from which these were driven.

Jan 1, 1940

Since the discovery of coal of the Southern coalfield (Illawarra 1797, Burragorang 1806) coal mining has grown progressively to the thriving industry of today. Early shallow escarpment mining required no serious access development, but with extension of mining to further and deeper areas, sinking became necess- ary. Now, with 17 major shafts and 7 decline drifts in current use, new mining activities involve several current sinking and drifting projects, with more in prospect. Conventional sinking and drifting, using blasting and mucking techniques proven in recent years are normally in use, with attempts, recent and current to accelerate advances by boring techniques. With export and to less extent local market unpredictability, it is vital to produce mine establishment times to allow advantage to be taken of market upswings and there is great need for research and improvement of mine access construction as the major aspect of establish- ment.

Jan 1, 1976

Western Mining Corporation began shaft sinking operations at it's Foster orebody, south of Kambalda, on the 20th June, 1984. The top levels of the orebody are currently being mined via a decline some 1.5km away.Long term plans require the shaft and decline to combine and produce 400,000 tonnes of nickel ore per annum. Eventually all of the ore produced will be hauled up the shaft.The shaft is 4.5m in diameter and the target depth is 760m. Ground conditions to date suggest there will be no further need for concrete lining beyond the oxidised zone. As such, the sink is an open-shaft development in competent basalt rock. Shaft furniture will be installed on completion of the excavation to the target depth.This paper summarises the experience in the project to date, along with comparisons to conventional shaft sinking methods employed in previous years at Kambalda Nickel Operations.

Jan 1, 1985

By Doyle P, Mulroney D

The Cassidy Shaft was sunk to access the Mount Charlotte and Reward Orebodies below the Flanagan Fault. The 1,184m deep shaft is concrete lined to 6.5m diameter for its full depth. The initial 590m was excavated by stripping into a 1.8m diameter borehole and hoisting the broken material through the existing mine. The remaining 594m was excavated by conventional shaft sinking methods. The shaft was sunk through 3 existing plats and an additional 8 plats cut. 1,800 tonnes of steel and 8 cables were installed during the furnishing of the 4 compartments.

Jan 1, 1985