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The Mobile Miner MM130 (Figure 1) is designed to tunnel or mine in hard rock. It has a 4.1 m diameter cutterhead mounted on a horizontal axis which in turn is perpendicular to the line of the machine. The cutterhead rotates at 15 rpm and is supported on a boom which swings the cutterhead through a horizontal arc.

Jan 1, 1993

By M DellÆAmico, K Vining

The iron blast furnace is the most widely used and efficient producer of liquid iron; however, emissions from sintering and coking cause environmental pressure for the integrated steel works. The combustion of coke fines (breeze) during sintering contributes to greenhouse gases (GHG) (eg carbon dioxide) and is a source of SOx and NOx emissions. Coking capacity is also constrained by environmental concerns and economic factors, such as increased coke consumption, and short supply is leading to high prices. Improved coking practices, which result in reduced production of fines, are also contributing to the tight availability of breeze for sintering. This combination of factors presents an opportunity to consider alternatives to coke as a fuel for sintering. CSIRO Minerals has been investigating the use of wood biomass/char as a substitute for coke during sintering. Wood biomass, or char produced from it, is an attractive carbon source as carbon dioxide liberated during combustion can be sequestered back into growing biomass. It has great potential to reduce the emissions from integrated steelworks and improve their environmental acceptability. Harvested biomass/char is also a renewable and sustainable resource and can be integrated with good land management practices such as remediation of salinity affected land. Weeds, especially woody weeds, can also be used as a source of biomass for charcoal, and integrating char production with weed management can help address a pressing environmental issue in Australia. Previous reported preliminary testwork indicated that the use of Red Gum char as a replacement for coke resulted in a product sinter of comparable quality, improvements in productivity and significant reductions in SOx and NOx emissions. In the latest testwork, CSIRO has examined the properties of a range of potential charcoals, and has conducted a further series of granulation and small-scale sintering trials with them in simulated Japanese Steel Mill iron ore blends. Sinter fuels characterised and evaluated include industry sourced coke breeze, commercially available wood char and a charcoal from prickly acacia (acacia nilotica). Prickly acacia has been declared a noxious weed, is widespread in Australia, and is classified as a æWeed of National SignificanceÆ. The results presented in this paper support the notion that charcoal outperforms coke in many aspects of iron ore sintering and factoring in environmental considerations makes the switch to charcoal even more favourable.

Jan 1, 2005

By Quast K

A series of laboratory flotation tests were conducted to evaluate the effectiveness of various depressants as arsenic (and zinc) depressants in the lead cleaner stage of the NBHC mill at Broken Hill. The depressants used included potassium cyanide, ferrous sulphate, sodium hypochlorite, potassium ferricyanide and two Cyanamid commerical depressants, Aerodepressants 610 and 633. A standard roughing stage was completed before the addition of the reagents in the cleaning stage. All reagents tested produced significant arsenic depression, with the best results being obtained with the addition of potassium cyanide and sodium hypochlorite. Some of the depressants activated the zinc in the process of arsenic depression. The best result was obtained with the addition of 90 g/t potassium cyanide at a pH of 10 when arsenic recovery was only 1/4 that of the value obtained for the standard test.

Jan 1, 1991

By Boland J

Prediction of rock cuttability by various excavation machines such as tunnel boring machines, road headers, rippers, picks, roller disc cutters, excavators, etc is of major concern to both civil and mining engineers and rock mechanics. In principle, the design of a rock cutting tool is based on achieving maximum excavation with minimum input energy, minimum applied force, minimum equipment weight and volume and, more importantly, minimum tool wear. When a rock material is indented by the force of a cutting tool and then unloaded several material zones form underneath and around the tool. As the tool moves into the rock the volume of its associated rock cavity (ie volume of displaced rock) expands and depending on the indenter's shape various phenomena may occur. Immediately beneath the tool a small zone in which the stress state is more or less hydrostatic, is formed which is underlain by an inelastic, or damaged, material zone. Both size and shape of this damaged zone control the magnitude of the indentation force and the chip formation mechanism during unloading. The rock is unable to store the whole strain energy induced by the tool and consequently the extra energy is expended either in forming new fracture surfaces and/or in plastic deformation in the damaged zone. Therefore, it is not surprising to see that both perfect-elastic and rigid-plastic constitutive models are not generally suitable for modelling indentation of rocks. In contrast elastoplastic constitutive models are more appropriate as they can include both elastic and plastic deformations (Kral et al, 1993). Elastic solutions for several half-space indentation problems can be found in most text books on elasticity and in particular in Timoshenko and Goodier (1951), Sneddon, (1951), Poulos and Davis (1974) and Johnson (1985a). If a failure criterion, eg the Mohr-Coulomb failure criterion, is applied to delimit elastic solutions for indentation problems, a lower bound limit of the applied indentation force (for a given indentation depth) can be estimated. It may be noted that elastic analyses, without any delimiting failure criteria, normally overestimate the indentation force. Plastic solutions for a few indentation problems may be found in Hill (1950), Johnson, (1985a) and Alehossein et al (1992). When analysing the behaviour of indented rocks the choice of an appropriate constitutive model describing effectively the behaviour of the rock at various stages and phases during indentation is a challenging issue. Several questions need to be answered before starting an effective analysis. The first question is of course: Which one of these is more appropriate for modelling zones underneath and around a cutter, elasticity or plasticity theory, continuum damage mechanics or fracture mechanics, and what is the bridging link between these various theories? Which mode is more dominant in fracturing rock, tensile or shear mode? What governs the mechanism of chip formation? What is the function, shape and the behaviour of the pulverised zone that forms just underneath a cutter? Is the hydrostatic stress state assumption reasonable for this zone? How does the rock change during the absorption and dissipation of the input energy and how does the indentation energy vary with rock type and depth of penetration? How can we model the damaged zone under the indenter? Furthermore does a plastic material form beneath the pulverised zone? When and how do radial and ring cracks form around and under an indenter?

Jan 1, 1995

The InLine Pressure Jig represents a breakthrough in digging technology Its design incorporates a unique combination of features previously utilised in conventional jig design. In particular, a moveable screen and circular bed are used to excellent effect. However, a major design innovation is the encapsulation of the circular bed within a vessel - allowing the equipment to operate under pressure. This innovation eliminates free water surface, improves the dynamics within the separation layer (crossflow) and provides significant cost savings in the handling of slurries. Recent research results have indicated its capacity to achieve high recoveries and upgrade ratios in the gravity separation of Minerals.

Jan 1, 1997

By S Thomas, E Grimsey

Mining education in Australia has undergone another cyclical downturn over the past five years and several departments have been discontinued while others are still teetering on the brink of destruction. During this downturn Curtin UniversityÆs WA School of Mines (WASM) has managed to stay alive and well, but this has not been by accident. This paper outlines some of the strategies and experiences that have kept WASM in a strong position and offers hope to other departments and schools elsewhere that are still experiencing difficulty. This paper is also directed at all mining departments and schools that are certainly going to see it all happen again after the next mining boom turns to bust.

Jan 1, 2004

The Northland Peninsula of northern North Island, New Zealand contains a complex and diverse record of volcanism which reflects rapid tectonic changes during the late Cenozoic. The main volcanic associations observed on the peninsula are late Cretaceous- early oceanic crust obducted onto Northland at the end of the Oligocene, Miocene arc-type rocks and Pliocene-Quaternary intraplate basalts. This sucession of volcanic successions can be related to tectonic convergence developing into subduction and followed by a an environment of tectonic tension. While the volcanic activity is ultimately linked to specific tectonic regimes, because of rapid change magmatism was decoupled from the specific tectonic event. This decoupling of magmatism and tectonism appears to be a feature of the zones of plate interaction in the southwest Pacific region.

Jan 1, 1990

The provision of electrical power is an important consideration in project development. The first step to be taken in this area is to assess the power requirements of the project. The alternatives of laking a supply from a power authority or providing local generation can then be considered. This requires additional defmition of the probable characteristics of the supply.The availability of authority power in Australia is limited by the extent of the state power grids. Recent developments now allow these grids to be extended and their load capacity increased to meet major load increases at less cost than was previously possible.The options for local generation include diesel, gas turbine, steam, hydro, solar and wind, each having its particular performance characteristics and costs. The choice of fuel for diesel, gas turbine, and steam plant likewise involves consideration of a range of factors. The arrangements adopted for five recent Australian remote development projects indicate how some of these aspects influence the decision on power supply.

Jan 1, 1990

By Raudsepp R

Since 1991, the Porgera Joint Venture has processed refractory sulphide flotation concentrate by pressure oxidation with the subsequent gold recovery, from the washed residue, via a conventional leach/carbon-in- pulp (CIP) circuit. The capacity

Jan 1, 1997

Host minerals for gold have been of great interest to exploration geologists and metallurgists for a variety of reasons. The depletion of high grade ores in many parts of the world requires that greater attention be given to the study of host min-erals for gold. Some host minerals have been employed in exploration as traces for gold. They are also essential in the design of extraction processes for treating gold ores.This paper reviews the mineralogy of important gold deposits of Papua New Guinea (PNG), Indonesia and New Zealand and focuses attention on the ore minerals and rock-forming minerals that host gold.

Jan 1, 1994

By Cloutier JY, Quinn P, LeClerc A, Dube G, Agar GE

Gold dissolution by cyanide requires the presence of oxygen which is usually supplied by sparging compressed air into the gold containing slurry. For those ores that contain certain obnoxious substances that consume oxygen, maintaining the required minimum level of dissolved oxygen can be troublesome. One of the most economical solutions to the problem of low dissolved oxygen, especially in plants that have air compressors installed, is to enhance the rate of oxygen mass transfer. The oxygen mass transfer rate was measured in a two phase system using two different sparger arrangements, and with addition of a frother that is known to reduce the bubble size produced by the sparger. The common sparger system was shown to be inefficient compared with a readily available but under utilised method of gas dispersion which introduces air directly below the reactor turbine. Transfer of this technology to an operating plant confirmed the beneficial effect of the improved sparger system. The addition of the frother did decrease the bubble size, but it also reduced the oxygen mass transfer rate.

Jan 1, 1993

By S C. Sc, J Young, N Belluz, D Nicholas

The heavy sulfide zone (HSZ) of the Grasberg deposit has the geometry of a funnel and is located at the contact of the mineralised intrusive and the relatively barren sedimentary rock types. The geometry and the rock properties associated with the HSZ plays a significant role in pushback design and sequencing. Most of the HSZ has relatively low strengths which must be considered in slope design and management. This paper presents the open pit mine geotechnical and planning design considerations associated with the HSZ.

Jan 1, 2007

By Edmonds W, Giles C. W, Webb R. J, Gum J. C

Gold production from The Granites - Tanami Goldfield during 1993 is expected to exceed 8 t, eclipsing that of the traditional Northern Territory gold mining districts of Tennant Creek and Pine Creek. This is the result of dedicated and successful exploration, and the consequent discovery of new orebodies such as those at Dead Bullock Soak.Following granting of access to regional exploration areas in 1988 and identification of favourable host rocks in the Schist Hills area, North Flinders Mines (NFM) began a methodical exploration program of detailed geological mapping, rock chip sampling, costeaning and various types of drilling. The first resource of 600 000 t of 3.3 g/t gold was announced in mid-1989. This has grown progressively with systematic exploration to the currently published resource inventory of 6.6 mT @ 5.4 g/t, (as at 31.12.92) contained in six separate orebodies within the Dead Bullock Soak Mineral Lease at Schist Hills.

Jan 1, 1993

By Bruce See J

Oxidation of artificial Imperial Smelting Furnace lead bullion was performed during cooling between 1180 and 820°C in order to attempt to produce a tin-rich dross.The addition of sodium carbonate together with stirring increased the tin content of the dross when oxidation was carried out with air or PbO on zinc-free bullion.Zinc in the bullion during oxidation resulted in a decrease in tin concentration of the dross due to zinc oxidation and copper entering the dross.

Jan 1, 1987

By Lockyer PC, Reed MR Bartlett PM

Difficult ground conditions have plagued the underground operations at Mount Windarra since mining started in 1974.The ore at Mount Windarra consists of seven vertically dipping, sub vertically plunging ore shoots. The ore zone in which the shoots lie is characterised by moderate to heavy cleavage and the presence of serpentanite. The ore is known to extend to 1100 metres below surface.Long hole open stoping under cover of backfill has been used as the primary mining method at the mine, but its poor performance brought the mine near to closure in 1984. The mine had been closed from 1979 to 1980.

Jan 1, 1985

It is often assumed that geotechnical investigations or studies for open pit mines are confined to providing a slope design. However in an operating mine, the design is only one component of a mine geotechnical program. Reviews of slope designs are ongoing throughout the mine life. The concept of Pit Slope Management has been formulated because the design only entails one component of a total program that contributes to a safe, efficient mining operation. Risk is a normal part of mining. Effective management allows the risk to be contained or controlled. If the slopes are not effectively managed there will be increased risk for the operation. Experience has shown that utilisation of Pit Slope Management coupled with a broad base of experience to define the key controls on stability, provides a pro-active, objective approach. The reasoning is deductive and relies on the behaviour of the ærocksÆ. Once the key aspects are defined, studies are well focused, implemented as required and the risks can be effectively managed. When the key controls on stability are poorly understood reasoning is typically more ægut feelÆ. Under such circumstances studies, if carried out, may meet short-term objectives but often ignore the long-term objectives. Hence the risk to the project is greatly increased. This paper presents several case studies highlighting the above aspects and present elements of the Pit Slope Management Program approach which have been successfully utilised by the author to manage risk in mining projects.

Jan 1, 2003

In coal room and pillar, and pillar extraction panels, the sidewall conditions were investigated based on underground measurements and numerical simulations. Three-dimensional linear elastic models provided a useful and quick prediction of the amount of sidewall spalling. However, more complex constitutive models were required to simulate more accurately the extent of fracturing and its effect on the stress re-distribution. The input parameters of a Mohr-Coulomb model were determined by back-analysis of underground measurements, and the effect of the depth of the workings and the time dependent occcurrence of coal pillar fracturing were analyzed.

Jan 1, 1992

This paper describes the programing and specification requirements which affected the choice of excavation methods on the Melbourne Underground Rail Loop (M.U.R.L.). The various methods that were chosen are briefly described, and the three most used are compared in more detail. Excavation rates, cycle times and other statistics are compared for full face tunnel boring, full face drill and blast, and heading and bench using a road header excava- ting machine. The length of tunnel excavated is sufficient to enable meaningful statistics to be presented and the significant specifi- cation and geological factors are described to weight the statistics where necessary for purposes of comparison. Average tender prices are given for excavation and primary support to indicate the reimbursement sought by contractors to carry out this type of tunnelling.

Jan 1, 1981

By Billingham R

The Department of Mines Tasmania employs a Drilling Section for specialised drilling re- quired by government and semi-government bodies. The section has a complement of nine crews oper- ating auger, cable tool, rotary and diamond drilling plants. For some years the Department has been involved in site investigation drilling of the Derwent River. The experience gained indicated that drilling methods should be altered. In 1976 an urgent programme was requested and the opportunity was taken to solve many problems associated with previous investigations. Equipment and methods are discussed in detail. The improved technique contributed to the suc- cessful completion of the Phase 1 site investi- Gation.

Jan 1, 1977

By Lee M. F, Guilfoyle K

A large hard rock rib pillar was recently preconditioned at Mt Charlotte mine using a novel blasting technique. The motivation for trialling this procedure was a history of past pillar failures, with associated seismicity. Design studies had shown that a new proposed pillar would be at risk of violent failure, and preconditioning was used in an attempt to reduce this risk. Preconditioning by blasting involves physically modifying a selected zone of ground in advance of mining, then forming the pillar so that it incorporates that zone of ground. The modified rock in the zone is intended to allow extra closure (yield) of the pillar in response to mining-induced stress changes. The ground modification was done by tight firing a blasthole array to fracture the rock. The blast design comprised pairs of pre-split blastholes to create a series of short cracks across the target zone, followed by main blastholes to fracture the rockmass between each pair of cracks. A monitoring program was used to establish whether or not the preconditioning was effective. It included conventional extensometers, stress change cells and closure stations, plus a seismic monitoring system. To-date, stoping is complete on one side of the pillar and has just commenced on the other. Results show significant movements within the preconditioned zone and on geological structures in the pillar, as well as lower stress in the pillar compared to an adjacent non-preconditioned site. The preconditioning technique can be applied elsewhere, provided its purpose, mechanism and side effects are understood. Benefits are likely to include more assured production, and successful pillar recovery even in high stress situations.

Jan 1, 1995