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By A Tawadrous, D S. Preece

Cave mining is of interest to the mining community as it offers a chance to extract large, deep orebodies with low operating costs and high production rates. It allows for extracting large low-grade orebodies, which may not have previously been considered for mining. Cave mining is done either top down (ie sublevel caving) or bottom up (ie block/panel caving). Both approaches rely on gravity, stresses and weakness of the rock to fracture and achieve a controlled collapse.Block caving starts at the base of the orebody. It progresses upward and across through continuous collapse of the roof. To achieve this, a critical hydraulic radius must be exceeded. This is accomplished by blasting drawbells, through which the caved ore passes to the production level. An entire level above the drawbells (undercut level) is excavated to help initiate the cave. The undercut level ensures the connection between drawbells and achievement of the required hydraulic radius.Conventionally, drawbells are generated by drilling and blasting several times from the production level as well as the undercut level. Mucking between each shot is required to generate enough void space for the rock to swell. The need for several blasts necessitates some downtime between each blast. Also, the cost of developing and maintaining the undercut level can constitute up to 35 per cent of the cost of mining the panel.A new blasting technique was developed to create the drawbells in a single blast from the production level. The technique ensures the connection of the drawbell to the neighbouring ones, thus, the critical hydraulic radius is reached and propagation of the cave achieved without the need for the undercut level. The technique has the potential to reduce the capital cost of a block caving operation, increase its feasibility and reduce time to reach the ore and consequently the payback period. This paper presents the modelling of a traditional drawbell excavation process, the philosophy of the developed technique, the modelling of that new design and its implementation.CITATION:Tawadrous, A and Preece, D S, 2015. A novel blasting technique to create drawbells and eliminate the undercut level in block cave mining, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 617–624 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

This paper investigates the adequacy of current gas monitoring techniques to adequately detect spontaneous combustion in underground coalmines. Despite being in the 21st century spontaneous combustion continues to occur in underground coalmines sometimes being detected only at a very advanced stage. Control of the incident is often then very expensive and time consuming. The adequacy needs to be assessed not only from the point of view of the analysis technique be it tube bundle, gas chromatograph or real time sensor but also the number, location and sampling frequency of the monitoring locations. Recommendations are made to optimise monitoring processes and recognise limitations of current techniques.

Jan 1, 2005

By Trumpff H

Opencast Lignite Mining requires topwall strata of seams to be fully depleted and footwall aquifers sufficiently depressurized. To prevent a spread of the cone of depression into protected wetlands some distance away, alternatives had been investigated such as closing water works, underground slurry wall barriers and recharge by infiltration. As a result of these investigations, the infiltration method has been chosen and in a first phase during the next decade it will utilize as much as 55 x 106 m3/year. Using this approach, the survival of the wet lands is assured.

Jan 1, 1988

By N Jamson, T K. Rohde

The Mine is an underground zinc (Zn), lead (Pb) and silver (Ag) operation in central New South Wales (NSW). Broadly speaking the Mine has two domains that require rehabilitation, the mine industrial area (MIA) and the tailings storage facility (TSF). The MIA has been used for the handling and processing of ore and contains elevated sulfate, sulfide and metals (Pb, Zn). The TSF receives the by-products of processing, that is, potentially acid forming (PAF) tailings which also contain elevate sulfate, sulfide and metals. Typically, the rehabilitation of a TSF involves two controls. Firstly, controlling the potential for PAF tailings to form acid rock drainage (ARD) by limiting interaction with oxygen. Secondly, once the tailings are unsaturated, limiting interaction with water (usually as rainfall) to reduce the potential for ARD to be transported to the receiving environment. These two controls are often employed in the form of a cover.In semi-arid environments there are many Australian examples of covers that have been built to limit interactions of mine by-products with oxygen and water. Typically, the covers contain one or more layers and are built from soil and rock which may include run-of-mine rock. The Mine however has limited supplies of stockpiled soil; and run-of-mine rock is not generated in large volumes because it is used as backfill underground. A cover design strategy was developed to cater for these limiting factors. The strategy identified soil, ore and rock accretion (the accretion) below the MIA could be a potential source of borrow material for the cover. The purpose of this paper is to describe the cover design process, the method and results of large (2 m tall) column trials that were used as a cost-effective way to trial three cover options and finally, the paper describes the water balance that was developed from the column trial results and subsequent modelling using SVFlux.CITATION:Rohde, T K and Jamson, N, 2018. Making use of potentially contaminating mine waste in cover design, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

Grey River Gold Mining Ltd commenced dredging alluvial flats in the Grey River Valley in 1989.Previous drilling indicated over 100 million cubic metres of gravels with some 90% of the gold in the bottom 7 metres.The dredge built by Rahco, Spokane, was innovative in a number of aspects but particularly in the fact that a separate ladder with a cutter and pump was used to strip the overburden and a bucketline to mine the gold bearing wash below.Metallurgical studies and exploration were initiated when the project commenced; Leasing and environmental considerations were investigated and action taken.While progress is being made, the operation at this stage is not meeting required production and performance. Main problems have been with the stripping system and wear.

Jan 1, 1990

By L Drowley

The Adelaide Desalination Plant (ADP) draws raw sea water into the facility and returns saline concentrate to the Gulf St Vincent via subsea conduits. This paper describes the detailed design and construction methodologies developed for the cross connection tunnel excavation. The paper concentrates on key design elements which include:· lateral breakout support of the segmental tunnel lining,· ground improvement grouting in the zone of the cross connection tunnels due to extremely variable and weak ground conditions, and· excavation methodologies and proposed support types of the riser to tunnel cross connections.The design process consisted of developing concepts, detailed risk assessment, three-dimensional (3D) finite element modelling and structural analysis for temporary support of tunnel lining; functional design of the ground improvement grouting and the temporary support; and permanent lining design of tunnel to ocean riser connections in a mixed soft ground/hard rock environment.The paper also presents conclusions of the design based on construction data available, and highlights the close collaboration between the design team and construction team.

Mar 8, 2011

Previous studies on the blast furnace raceway zone have been undertaken at three levels of scale, namely: laboratory models at low temperature, hot models which simulate coke combustion in the zone, and tests performed on operating and dismantled blast furnaces. This paper reviews the results of this published work on raceways in order to illustrate the factors which affect the raceway shape, size and combustion characteristics. As a result of the work it has been established that raceways are influenced by blast parameters such as velocity, temperature and chemistry, as well

Jan 1, 1981

By Perring CS, Vearncombe J. R, Ho SE, Groves DI

Large Late Archaean greenstone belts in Western Australia, Canada and Zimbabwe, contain abundant mesothermal gold, volcanogenic massive base-metal sulphide, and komatiite-associated Ni-Cu mineralization. These greenstone belts are similar in many respects to convergent and accretionary plate margins found in the Pacific rim; modem environments which are cor-respondingly rich in gold and base-metal mineralization. The giant gold placer deposits of the Late Archaean Witwatersrand Basin (the world's largest gold producer) formed in a foreland or retro-arc basin; in a similar tectonic setting to much modem placer mineralization around the Pacific. Gold and volcanogenic base-metal sulphide mineralization are abundant in Late Archaean terranes and the Pacific rim because1. gold mineralization is a product of convergent margin tectonics, and 2. accretion in convergent margin orogens provides the best chance of preserving base-metal mineralization related to submarine volcanism.It is therefore likely that the abundance of gold and base-metal sulphide mineralization in the Late Archaean reflects the widespread growth and sta-bilization of continental crust via tectonic processes broadly similar to those operating in the present Pacific basin.

Jan 1, 1990

By I Lamb

Past experience of ground settlement and groundwater monitoring for tunnelling projects in Melbourne has provided an appreciation of the value and importance to owners of establishing a broad baseline monitoring program of the ground surface movements and groundwater movements well in advance of the commencement of any excavation and tunnelling activities. For the Northern Sewerage Project (NSP) tunnels in the northern suburbs of Melbourne, a baseline monitoring network of ground settlement points and groundwater wells was established in early 2006, 18 months prior to the commencement of project construction, and has continued throughout the tunnelling and project construction activities. This baseline monitoring network provides insights into the superposition and interpretation of both tunnelling and non-tunnelling effects, such as seasonal effects, which result in ground settlement.In the case of the NSP the baseline monitoring and construction phase excavations coincided with several years of drought. The reduced rainfall developed overall downward settlement trends project wide that could easily be mistaken at the local site level to be construction effects if the baseline monitoring was not available to show otherwise. There are lessons to be learned from the NSP experience for tunnel projects where there are variable surface soil types and where project-specific settlement criteria are to be established for the protection of property prior to construction.This paper presents examples of the baseline monitoring, how the tunnelling-specific settlement was identified and determined, and what this means in terms of how settlement criteria should be established and set for project consenting and in the construction contract documents.

Mar 8, 2011

By M Hood, X S. L, W J. T Daniel, H Gurgenci

It is believed that disc cutter shape affects rock fracture and therefore cutter performance and cutter life. However, the current generation of disc cutters is made of hardened steel and these cutters wear rapidly and consequently they are unable to maintain their original shape in strong and abrasive rock. This wear problem could be reduced if the cutter was made from a harder material. Unfortunately as material hardness increases so does the propensity for brittle failure. In this study the optimum cutter shapes were identified by studying the mechanics of rock/tool interaction. The results showed that bevel and wedge cutters are better than cutters with dome and flat edges. A new cutter was designed, based on this result, using a harder material to increase the life by a factor of 20.

Jan 1, 1998

By M Behrens

The Melbourne Main Sewer Replacement (MMSR) is a major urban infrastructure project involving approximately 2.3 km of tunnelling and construction works. The works extend from Docklands Precinct, on the southwest edge of the city, southwards to connect with the Hobsons Bay Main Sewer in Port Melbourne. The tunnel boring machine (TBM) tunnelled section of the works terminates at the Yarra River where the delta geology and alignment requirements precluded the use of underground tunnelling methods. The 132 m long river crossing works involve a cut-and-cover excavation within a staged fl ooded cofferdam construction to construct an immersed tube tunnel as an extension of the TBM works.This paper reports on the development of the staged construction method and highlights the geotechnical and structural design aspects involved in building a new sewer in the Yarra River to close the gap between the new TBM driven and pipe-jacked tunnels.

Mar 8, 2011

It is very apparent that the hydrogeotogicat characteristics of mineral deposits in China be dominated by meteoric factors, terrain factors and the kind of karstic aquifers as a main source threatening the mining.The hydrogeotogicat characteristics of mineral deposits in dry areas are very different from that in non-dry areas.The rote of precipitation is very important to mine dewatering.The difference of water recharge condition of a mineral deposit located upper (or under) Local erosion basis is existing. There are more than two million square kilometers of carbonate in China.Many water-bearing deposits are distributed in it.According to the karst shapes the surrounding karstic aquifers of mines can be divided into three kinds including solution fissure aquifer,karstic cave aquifer and underground stream (karst stream) aquifer. Underlier invasion is a main feature of karst water-bearing coal mine and upper tier incoming is a main feature of skarn copper and ferro mine.Swatlor pillar and collapse is a special feature of karstic water-impregnated mine.

Jan 1, 1988

For the mineral industry, sustainability seems to mean socially positive and ecologically neutral mineral extraction. Mines are financed and developed in response to demand for their products. The purpose of my paper is to indicate the potential dimension of demand. As part of an unrelated study which I undertook ten years ago, it became apparent that there is a persistent relationship within communities between infant mortality and mineral use; greater mineral use corresponds to a lower rate of infant mortality. This comes as no surprise; sufficient potable water, a reliable supply of food, hygienic waste disposal, hot water and refrigeration all improve the chances of survival of the more vulnerable members of any community. The predictable provision of these facilities requires the application of minerals. This relationship is supported by a table (Appendix 1) included in the UNICEF publication, æThe State of the WorldÆs Children 2001Æ. This table lists regional infant mortality rate (IMR) statistics from around the world, including a listing for æindustrialised countriesÆ. Such countries experience an IMR lower by an order of magnitude than any other region. æIndustrialisedÆ inevitably involves the use of metallic and energy minerals. The principal use of copper is in the generation and distribution of power; it is fundamental to any industrialisation. IMR is a valuable connection because it quantifies caring for the young, a vital strategic driver of human behaviour independent of time, place, fashion or economic circumstances. I have tabulated the population, IMR and the copper demand per head of population for countries containing over 99 per cent of the population of the world in the years 1950, 1960, 1970, 1980, 1989, and 1999. These countries have been consolidated into four groups, Very High, High, Medium and Low rates of infant mortality (UNICEF has used this terminology; the Low group includes all the æindustrialised countriesÆ). The purpose of this consolidation was to reduce the volume of work, to dampen out the impact of regional wars and business cycles, and to dampen out the variable quality of information. Based on the pattern of the copper demand, population and IMR over the last 50 years, I have projected the likely copper demand in 50 years time. A dominant feature of my tabulation is the increase per decade in copper use per head and a corresponding reduction of the IMR. The word æuseÆ is preferred to æconsumptionÆ because it is estimated that over 80 per cent of all the copper ever mined is still in circulation There are two major influences at work; one is the absolute increase in population (UN estimates for 2050 are updated periodically) and the second is the movement of countries into a higher pattern of use and lower IMR. For example the Medium group in 1989 had an infant mortality rate approximating that of the Low group in 1960. With the population of the Medium group (which includes Russia and China) forecast to reach 2.6 billion in 2050, the world copper demand in that year will be significantly greater than the present figure. Nevertheless it will not be as great relatively as the increase of over 300 per cent in the last 50 years.

Jan 1, 2002

By Hendon G. W, Carr F, Jiang Y

A vast majority of the operating longwall sections use shield-type face supports to provide ground control in the United States. As a co-operative research program between the University of Alabama (UA) and Jim Walter Resources, Inc.(JWR), a joint research program is underway to study interaction of shields with surrounding rock masses. A series of analyses on the response of shields are performed using monitored data at a longwall face in a deep coal mine. In this paper, various effects of parameters, such as leg pressure, setting load, developing load, maximum loading rate, pressure in capsule, and convergence between canopy and base, are discussed and recommended as stability indices. A microcomputer program is being developed for instantaneous interpretation of the shield monitored data, and for giving warnings of potential problems. The preliminary results define the effects of the setting load, developing load, and rate of developing load or leg closure rate. The objective of the study is to understand the shield characteristics and their interaction with surrounding strata in real time, then develop a reliable program for maintaining longwall stability.

Jan 1, 1992

By Potter DJ, Firkin GR

The Imperial Smelting Furnace operated by Sulphide Corporation Pty. Limited at its Cockle Creek zinc-lead smelter was recently equipped with tuyeres angled at 25 degrees instead of the usual 10 degrees. This change was prompted by the results of model studies undertaken by tha Research Department of Imperial Smelting Processes Limited, at Avonmouth in the United Kingdom, and by the favourable results of operating trials on the Cockle Creek furnace using bent-tip tuyeres to simulate 25 degree inclination. The use of 25 degree angle tuyeres has made it possible to operate with lower zinc values in discard slag and has improved hearth stability over a wider range of sinter quality and composition.

Jan 1, 1981

By D A. Deglon

Solids suspension is important in the design and operation of mechanical flotation cells, and is a necessary precondition to particle collection. Most of the fundamental hydrodynamic research that incorporates some aspect of solids suspension was done by Arbiter, Harris, and co-workers, or Schubert and co-workers. However, a need for research into solids suspension in mechanical flotation cells exists, since very little has been done since the late 1980s; a time that also coincides with the advent of round mechanical flotation cells and the subsequent dramatic increases in maximum flotation cell sizes. In this work, concentration profiles and critical impeller speeds, Njs, were measured in a 0.124 m3, round cell fitted with a 0.150 m, Bateman impeller mechanism. Two solids size fractions (75 - 106 and 150 - 250 ¦m) were tested, in ungassed and gassed conditions (JG = 0, 1 cm/s) and at various impeller speeds (300 - 900 rpm). The effectiveness of solids suspension was quantified in three ways in terms of extent of off-bottom solids suspension, suspension height (extent of solids distribution), and variation within the solids distribution, which together present a complete quantitative picture of solids suspension and distribution within the cell. Consistent trends were found when these effectiveness criteria were considered against relative impeller speed, in terms of percentage of critical impeller speed, N/Njs. Off-bottom solids suspension is complete at or above 100 per cent of Njs, with significant sedimentation occurring as the impeller speed drops below 60 per cent of Njs. Suspension heights consistently reached a level equivalent to 90 per cent of the tank diameter at the critical impeller speed, and dropped off significantly as N/Njs dropped below 60 per cent. The variation in the solids concentrations within the sampled profiles showed consistent trends in two-phase but not under three-phase conditions. The paper concludes that the critical impeller speed, Njs, commonly used in the design and operation of standard stirred tanks, is a very useful solids suspension benchmark for describing all aspects of solids suspension in mechanical flotation cells and should be correlated to system conditions.

Jan 1, 2005

By M Grinceri

The New MetroRail City Project was completed in 2007 in Perth, Western Australia. The project included construction of two underground stations, twin bored rail tunnels of 1.4 km combined length and cut-and- cover tunnels and dive structures of about 1 km total length. It is the first major underground construction project within the Perth central business district (CBD). This paper provides an introduction to the project and describes the geology and hydrogeology of the area. Ground conditions varied significantly along the alignment from soft estuarine muds in an area of reclamation to very dense cemented sands and very stiff to hard clays. Deep foundations for the project extend down into the bedrock below the CBD, a Tertiary siltstone/sandstone. Key geotechnical hazards encountered during the project are discussed. The building protection methodology on the project is described, including damage assessment, condition surveys, monitoring and protection of key structures.

Jan 1, 2008

Before proceeding to the main portion of the above subject, a few remarks as to the general question of our mill slimes seem called for, and, with this in view, it is intended to briefly refer to the salient, points connected with their production, treatment and disposal at the mills.It is well known that, owing to the inticate mixture of the constituents of our sulphide ore, 'a very great deal of crushing and grinding is required to detach the particles of galena from the zinc blende and gangue of the ore, and it will be readily understood that, in this operation, a considerable amount of the material is converted into a slime which consists of minute, but ,(as can be see~ under a glass) well definied particles of all the constituents· 6f the ore arid combinations thereof, the relative proportions of which depend on the dual characteristics of hardness and abundance of the different constituents. An analysis of the slime shows the contents to be as follows :-Galena (PbS)Blende (Zn S)Pyrites (Fe Sll)Ferric Oxide (Fell Os)Ferrous Oxide (Fe 0) contained in garnetsOxide of Manganese (Mn 0) contained in rhodonite and garnets

Jan 1, 1903

By McGuckin P. H

The Cadjebut orebody is a MississippiValleyType (MVT) zinc-lead deposit, and is located approximately 80 km southeast of Fitzroy Crossing in the Kimberley region of Western Australia. It is one of five zinc rich orebodies discovered by BHP Minerals in the region.The participation in the Cadjebut Joint Venture is BHP Minerals limited (Manager), 58 per cent and Billiton Australia Limited, 42 per cent.The mineralisation is contained in gently dipping dolomitised limestone sediments (part of the Lennard Shelf carbonate sequence) with an orebody width of between 60 and 120 m and a strike length of approximately 3 km. The deposit consists of two thin, stratabound shallow dipping orebodies, one overlying the other, to provide discrete but not independent mining areas. The orebody contains approximately 2.1 million tonnes of recoverable ore at an approximate grade of 12 per cent zinc and four per cent Lead.

Jan 1, 1992

By G McKay, M Erskine, S Macklin

The City of Sydney is currently investing in a number of infrastructure projects that require tunnel excavations within the Triassic Hawkesbury Sandstone. It is generally accepted that this formation has high residual stresses of ‘tectonic’ origin, so much so that these stresses have been implicated in a number of well-known failures and problems for tunnelling. These include failure of ‘roof beams’ comprising discrete beds in the crown of tunnel excavations; stress-induced spalling and ‘slabbing’ of tunnel walls; shear displacement between beds causing the failure of rock bolts; strain in adjacent infrastructure and, the necessity for re-grouting of high conductivity fractures due to stress relief dilation after excavation. Whilst there is an extensive published database of in situ stress measurements comprising ‘hydrofrac’, ‘over-coring’ and ‘slotter’ stress measurements, these data indicate a considerable spread of results. The traditional approach to interpreting this data has been to attempt to fit linear correlations to stress versus depth data, based on personal experience and ‘back-analysis’ of monitoring data during construction. However, there are a number of such correlations in the literature and there is divergence of opinion regarding the assessment of ‘background’ in situ stress and appropriate upper and lower bound values for design. This paper provides a brief review of the published data; suggestions on an alternative ‘risk-based approach’ to assigning in situ stresses for design; and, proposals on how in situ stress tests may be conducted in future to improve the quality of the database available to designers.CITATION:Macklin, S, McKay, G and Erskine, M, 2014. A review of the in situ stress database for tunnel design in the Hawkesbury Sandstone, Sydney, New South Wales, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 171–178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014