Search Documents

By Abishev D. N, Balakirev V. F, Davydov G. I

The problem of recovery of cobalt products from poorly oxidised nickel ores (Kempirsaisk deposit) and pyrite concentrates with a low content of cobalt (Sokolovsk-Sarbaisky deposit) has not been solved to the present time in Kazakstan. The balance reserves of nickel ore of the Kempirsaisky deposit make up more than 35 million tons with a nickel content of 1.13 per cent and cobalt content of 0.05 per cent; besides there are 110 millions tons of out-balance ores (Anon, 1995). In a tailing dump of Sokolovsk-Sarbaisk Mining and Productional Association more than 320 million tons of tailings of wet magnetic separation have accumulated, which contain 7.2 per cent of sulphur, 0.022 per cent of cobalt, 0.012 per cent of nickel, 0.094 per cent of copper, 0.079 per cent of zinc, 16.45 per cent of iron, and from which a high quality pyrite concentrate car) he separated through flotation, containing 48 - 50 per cent of sulphur, 44.15 per cent of iron, 0.141 per cent of cobalt, 0.07 per cent of nickel, and 0.10 per cent of copper. The well-known technological flow charts for cobalt and nickel recovery from the tailings of sulphide-magnetite ores dressing (to give pyrite concentrate) and from oxidised nickel ores, are not profitable at the existing prices for metals, but are not worthless and require significant capital investments for the realisation of their value. The flow chart `sulphate roasting - leaching - solution processing' is used widely for combined processing of cobalt-containing pyrite ores and concentrates.

Jan 1, 1996

By A Van den Bulck, K Verbeken, O Vergote, I Bellemans

Viscosity is one of the most important physicochemical properties during pyrometallurgical operations. In the sub-liquidus regime, an important factor is the presence of suspended solid particles, yet its influence is not well-described in earlier literature, despite the significance of this factor. This project aims to determine the influence of spinel particles (Zn(Al,Fe)2O4) on the rheology of a multiphase synthetic PbO-SiO2-ZnO-Fe2O3-CaO-Al2O3 slag system. Three data sets with a wellcontrolled methodology and three different spinel sizes (small (13 μm), medium (34 μm) and large particles (76 μm)) were published previously, using a custom-built high-temperature rheometer. This study presents an additional data set of slag viscosity measurements, performed using a different apparatus, the Anton Paar FRS 1800, to verify the consistency of the earlier determined viscosity behaviour. Within this data set, no consistent trend could be found between the predicted wt per cent spinel and the relative viscosity. Therefore, additional quenching experiments were conducted to identify the morphology and experimentally determined volume fraction of the spinel particles in the slag. These measurements revealed a difference in spinel size across the samples and corresponding viscosity behaviour, emphasizing the importance of spinel particle size on slag viscosity. Once the spinel size was taken into account, consistent viscosity results (relative apparent viscosity and flow index) were observed across the two devices. This study confirms that, once all parameters affecting slag viscosity are considered, the viscosity behaviour of a heterogeneous slag can be uniquely determined. The resulting optimised slag viscosity models can be used to predict viscosity before processing, addressing relevant phenomena such as slag tapping, slag foaming and copper droplet settlement.

Aug 21, 2024

By G Bournival, Y Saavedra Moreno, S Ata

Flotation frothers are heteropolar molecules that are preferentially adsorbed at the bubble interface to enhance the flotation performance by promoting the formation of small and stable bubbles. Frothers have different characteristics that can be used to classify them. A classification framework has been recently presented by Saavedra Moreno et al (2022) to classify non-ionic frothers by conducting a principal component analysis (PCA) and a hierarchical clustering analysis (HCA). However, for the purpose of the present research, only five frother characteristics, including molecular weight (MW), hydrophile–lipophile balance (HLB), critical coalescence concentration (CCC), the minimum Sauter mean diameter (DL), and foam stability index (DFI) were used in the PCA and HCA. All those characteristics were evaluated for a two-phase system in the absence of particles. Realising the important role that particles play in froth stability and behaviour, the effect of hydrophobic particles on the presented frother classification framework was investigated in this study. Four frothers with different characteristics, methyl isobutyl carbinol (MIBC), 1-pentanol, tri (propylene glycol) (TPG), and tri (propylene glycol) methyl ether (TPM), were chosen. The experiments were carried out in the presence and absence of silica particles esterified with 1-pentanol. It was evident that the results for 1-pentanol, TPM, MIBC, and TPG in the three-phase system agreed well with the frother classification presented for the two-phase system as frothers were clustered in the same groups. The findings from this research support the use of the frother classification system presented in two-phase system to select a specific frother for a particular application without the necessity of conducting laborious experiments in a three-phase system.

Aug 24, 2022

Traditionally trucks have dominated haulage in open pit mines. Only recently have conveyors begun to be used in the long haul and high lift duties of surface mines. Steep angle conveyors are proven versatile systems for elevating or lowering materials continuously at steep angles to 90¦. This paper describes the design of a bucket-type steep angle conveyor that was developed as a joint research project between the Western Australian School of Mines and the Maanshan Institute of Mining Research in China. The steep angle conveyor can be used as a viable option for transporting blocky ore from open pit mines. A pilot conveyor was constructed and tested to determine its technical and operational feasibility. Furthermore, a computer model based on Matlab mathematical modelling software was developed to simulate the performance of the pilot conveyor. The model enabled to determine the design parameters of industry-scale conveyors to yield satisfactory performance. These conveyors become very cost-effective for those mines having large mine lives and depths greater than about 500 metres.

Jan 1, 2003

The deep seafloor in Papua New Guinea's proposed Exclusive Economic Zone appears to be a gold-rich province in the same sense as the territory above sea level. Two significant sites with polymetallic massive sulphide deposits forming today are known on neovolcanic ridges in the Manus Basin. Their high precious metal contents have led to renewed interest in the issue of exploiting seafloor mineral deposits. The prospects of finding other, possibly larger deposits in the region appear substantial. This paper reviews current data on seafloor deposits in Papua New Guinea (PNG) and raises some issues relating to future commercial exploration and mining of the sea floor. One of the known PNG deposits could become a prime candidate for the trials needed to develop technology, establish costs, and minimise environmental impact.

Jan 1, 1994

The Broken Hill Proprietary Company Limited (BHP) started as a silver-lead-zinc mining company in Broken Hill, New South Wales, Australia in the 1880s. Since then it has diversified into the resource industries of steel, iron ore, coal, petroleum and copper. BHP World Minerals is a Business Group of BHP which is one of the worldÆs largest and most diverse mineral resource enterprises. BHP supplies raw materials for steelmaking, copper concentrate and other mineral commodities to customers in more than 45 countries. BHP World Minerals has operations spread throughout the world û in Australia, the United States, Brazil, Zimbabwe and Canada. Commodities produced by BHP World Minerals currently include silver, lead, zinc, titanium minerals, platinum group metals and coal. The BHP World Minerals Cannington silver-lead-zinc mine in Queensland, Australia is a return to the cradle of BHPÆs early silver-lead-zinc years. This paper compares the success factors and challenges at Broken Hill and Cannington.

Jan 1, 1998

By T Sparks

The Collie River catchment, located approximately 200 km south of Perth, covers an area of around 2830 km2 and is the source of run-off to the Wellington Dam, an important irrigation water resource for the Collie Irrigation District. The salinity of the Wellington Dam has increased due to historical clearing and irrigators currently use water with salinity levels approximately twice that of the Murray River in South Australia (Water and Rivers Commission, 2001). The Collie River Salinity Situation Statement (2001), released by the Water and Rivers Commission (now the Department of Water), identified realistic actions that could achieve the salinity reduction target. Subsequent benefit-cost analyses and prefeasibility studies recommended the diversion of the most saline flows in the Collie River away from the dam as an immediate intervention (URS, 2003). The East Branch of the Collie River above the locality of Buckingham (20 km east of Collie) contributes around half of the salt that flows into the Wellington Dam and the diversion and storage of the saltiest flows from the East Branch at Buckingham was identified as a viable option for reducing salinity in Wellington Dam. The proposal had one problem û the water could not be disposed of as quickly as it was diverted. However, in the vicinity of the diversion site were a number of coal mine voids and after preliminary discussions, the Government/Griffin Coal alliance was formed and from this the opportunities have continued. Diverted water would be stored temporarily in an adjacent mine void (Chicken Creek 4 void) and then disposed of to the sea. The disposal options included Western Power CorporationÆs saline discharge pipeline from Collie Power Station, or a new pipeline. The diverted water was also identified as a potential raw source for treatment and use in industry. This has opened up opportunities including desalination, water efficiencies in the power stations, increased reliability of water supply for the power stations, water for new industries, wastewater disposal options and extra water for PerthÆs water supply. In the process of solving the water storage problems the project introduced a range of mine water quality problems û heavy metals and pH û and the Department of Water (DoW) is now working with the mining industry and the Centre for Sustainable Mine Lakes (CSML) to develop treatment and management technologies. The project has received support and funding through the National Action Plan for Salinity and Water Quality (NAP) and it has been possible to accelerate and enhance this project as a result of NAP. The DoW has developed the proposal to an advanced stage and gained approvals for the capital diversion program to go ahead. The partnerships have expanded to include the second mining company, Premier Coal, the Water Corporation, Western Power and the Harvey Irrigation Cooperative. The proposal could feasibly result in a $90 million integrated water management initiative for Collie using the latest technology, mining operations and providing water for value adding industries in the local area. The DoW is not a mining company; however, our experience in managing water in times of shortage, environmental water quality criteria, competition for water and managing community expectations will have the same success factors:consultation and knowing your community and stakeholders, sharing issues and working in partnership can provide results far greater than the initial issue, even brackish water has value, every sector is in competition with each other and has to have a share of the water, an integrated approach can provide opportunities for development in areas of water shortage, and never think of water as wastewater.

Jan 1, 2006

Comparatively recent Tasmanian legisla tion established a series of rigid control standards for environmental protection just as ma spectacular expansion of the mining industry was nearing completion. Upgrading existing protection to obtain the necessary licence to operate under these new regulations required further major works and involved a considerable outlay of non- productive capital at a time when escalating costs and falling metal prices were straining economic efficiencies to the limit. Late in 1974 a major environmental protection scheme was commissioned by the Electrolytic Zinc Company of Australasia Limited at Rosebery on the West Coast of Tasmania. This 4 million dollar project was specifically developed by the Company ahead of and to meet the new standards for control of total effluents discharged from its zinc-lead -copper-pyrites mine and concentrator.

Jan 1, 1977

By Keyte SG

Gravity methods of recovering alluvial gold are not very efficient at particle sizes below about 0.1mm. Whereas such gold may not have been economic to recover in the past, the same may not be true today. Centrifugal concentrators, like the Knudsen and Knelson bowls, are showing promise after an inauspicious start, at least in New Zealand. The large proportion of heavy mineral in many auriferous beach sands and the natural hydrophobicity of fine gold should make flotation an attractive contender for its recovery. The conventional mechanical flotation cell is effective, but roughing, scavenging and cleaning are necessary to achieve both high recovery and low mass yield. More problematic is the difficulty of maintaining coarse and dense sands in suspension. The air sparged hydrocyclone is effective at recovering fine gold from a fine Colarado River sand, but is not effective for the coarse and dense beach sands of New Zealand. The flotation column shows much promise for these sands, when recoveries of over 80% and mass yields of less than 1% can be achieved in a single pass. The froth separator of the USSR and flash flotation could also be worthy contenders. It is felt that flotation could be limited to naturally and artificially de-slimed concentrates.

Jan 1, 1990

By H Fukaya T Miki, J Gamutan

Molybdenum disilicide (MoSi2) is a promising material for thermal applications due to its excellent heat and oxidation resistance. It can operate at temperatures of up to 1800°C as furnace heating elements and protect refractory metals such as molybdenum from rapidly reacting with air to form volatile molybdenum oxides at elevated temperature. In this work, the feasibility of forming MoSi2 on a molybdenum substrate by hot dipping in a silicon-saturated molten metal bath was investigated. This method is simple, predictable and can be used to coat large components and complex parts. It was found that tetragonal MoSi2 can be successfully synthesised on the surface of the substrate after dipping for 15 mins at 1000°C using molten tin (Sn), bismuth (Bi) and copper (Cu) baths. The growth of the MoSi2 layer was fast within the first 15 mins and then gradually slowed down with time. After dipping for 60 mins at 1000°C, the thickness of the MoSi2 layer were measured as 441.5, 19.5 and 13.1 μm for the copper, tin, and bismuth baths, respectively. The MoSi2 coating synthesised in this study provided oxidation resistance at 1150°C by forming a protective SiO2 layer on the surface. The SiO2 layer prevented the sample from rapidly oxidising by inhibiting direct contact between the molybdenum substrate and oxygen in the atmosphere. Compared to conventional methods, the proposed hot dipping method produces a MoSi2 layer more rapidly and at much lower operating temperatures. This makes it a more attractive option for coating large and complex components, with the potential to enable the use of MoSi2 in a wider range of applications.

Jun 19, 2024

By T Baumgartl, T Huynh, K Tungpalan, E Wightman, M Edraki, M Tayebi-Khorami, L Huang, S Palaniandy, E Manlapig

With the increasing rate of tailing production worldwide there is a growing concern about the hazards of tailings storage facilities (TSF). Past and current mining, processing and waste disposal strategies that focus on the extraction of the valuable minerals, and an economic assessment only, are no longer suitable. Social implications and environmental legacies must be included for effective evaluation. This is possible by using an integrated assessment framework to evaluate more alternatives, including the production of additional saleable and benign streams, alternative tailings treatment and disposal as well as options for reuse, recycling and preprocessing of existing tailings. Tailings are not viewed as a final waste product but as part of the resource. From the sustainability perspective the models developed in integrated research programs will contribute to more effective methods for assessing different scenarios and potential processes and lead to better environmental management, increased production of benign tailings and improved efficiency of water and energy use and thus more responsible resource stewardship of the ore resource.This paper presents preliminary results from a multiyear research program on integrated tailings management at the Sustainable Minerals Institute (SMI), The University of Queensland, called ‘Designer Tailings’. The project involves the gathering of experimental and observational information on tailings biogeochemical processes to design and modify the range of activities within mineral processing plants, upstream characterisation ore and gangue, and downstream tailings management for desired tailings properties and outcomes. This information will assist the development of new total integrated value chain CITATION:Edraki, M, Huynh, T, Baumgartl, T, Huang, L, Andrusiewicz, M, Tungpalan, K, Tayebi-Khorami, M, Wightman, E, Palaniandy, S, Manlapig, E, Evans, C, Farrokhpay, S, Bradshaw, D and Vink, S, 2014. Designer tailings – an integrated model for tailings management, in Proceedings Life-of-Mine 2014 , pp 599–608 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By R Markoski, P Grealish

The requirement for rapid vertical development for underground ventilation is often a factor when dealing with dynamic mine plans, with short vertical developments being used to optimise ventilation systems. In an effort to increase the safety and efficiency of the constructions, a simple and effective sinking methodology is required that is both adaptable and repeatable. A modified shaft construction methodology is proposed that attempts to minimise risk to the personnel as well as be cost-effective. Readily available equipment is used to ensure adaptability to the various environments and shaft parameters.One of the greatest risks of shaft sinking is having personnel working suspended over open cavities or underneath suspended loads. Removing this risk, by ensuring all construction is done from solid ground, allows for safer sinking operations. As the process is repeatable, familiarity and confidence in its construction sequence will increase with each successive sink.A trial sink is performed with a 3.6 m diameter, 20 m deep shaft. The shaft was excavated using a conventional strip-and-line philosophy, with the shaft then being lined from the collar via the use of large diameter corrugated steel culverts. The annulus between the steel culverts and shaft excavation is then filled with a concrete mixture to secure it in position.The new process was successful, with no personnel at any time during the process being suspended above an open excavation. The installation had relatively low capital and operational costs and was completed faster than an equivalent, conventional concrete-lined shaft construction. Therefore when compared to conventional shaft-sinking methods, this process can be considered safer, more efficient and relatively cost-effective.Further research is required to determine whether this method can be expanded to larger vertical developments.CITATION:Markoski, R and Grealish, P, 2014. A new method for rapid vertical development of underground ventilation shafts, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 603–606 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By H Jalalifar, N Aziz

In the ten years since the University of NSW proposed a pillar design methodology for bord and pillar operations, the Australian coal mining industry has changed substantially. What was primarily a bord and pillar design approach is now being applied to chain pillar design in longwall mines where the requirements are substantially different. The dimensions of chain pillars can impact on tailgate conditions (roof, rib and floor), seal performance, and surface subsidence. The status of chain pillar design practice in Australia is reviewed, with a focus on defining pillar strength, chain pillar loading, and assessing the performance of the roof/pillar/system. A new pillar strength equation is proposed for Australian coal that applies for all width/height ratios. An alternative analysis of probability of failure of chain pillars is presented.

Jan 1, 2005

By B Liu, W J. Zhang, S Saydam, B Li

Rock bolts are commonly used to reinforce ground in underground mining and civil tunnel environments. Rock bolts serve two main functions: i) they suspend large, loose blocks of ground, and ii) provide a protective pressure arch to restrain the deformation in an excavated void. Automated and precise tracking of rock bolt positions can assist with the operational success of ground support by reducing the amount of labour required in current manual practices. A point cloud is a large list of x, y and z coordinates in three-dimensional space, that when visualised, show a precise 3D representation of a physical environment. Point cloud data can be collected using accurate LiDAR scanners. These scanners can be mounted on a stationary tripod or on a moving vehicle. A key way point cloud data is used is in the bolt detection project being completed in conjunction with UNSW Sydney, which aims to provide an automated location of underground rock bolts from LiDAR scans. The immediate challenge with identifying rock bolts is that they constitute a very small portion of the data set amounting to approximately 0.01 per cent of some of the collected civil tunnel data. The process of detecting rock bolts from point clouds therefore requires a quick elimination of large background data while still preserving the bolt data. A further challenge is that the geometry of underground environments can often be very complex and non-uniform. To overcome these challenges, a two-step coarse to fine deep learning approach is taken. The first step is a coarse background elimination step aimed at removing as much of the background data as possible. The second step is a finer classification method, which uses deep learning to further segment the bolts from the remaining background. Additionally, a computer vision module is being implemented, which is expected to increase the detection rate by adding another dimension to the training data set.

Nov 29, 2022

Reverse sensitivity is a critical issue for all extractive activities. Extractive industries can only establish in the location of the particular resource sought to be extracted. Avoiding a location near sensitive activities (such as residential activities) may, therefore, be more difficult for extractive industries, than for other industry (such as dairy factories).   This paper focuses on the following matters: +        principles to be derived from case law, +       district and regional council approaches managing reverse sensitivity effects, and +        avoiding, remedying or mitigating reverse sensitivity effects in the future.

Jan 1, 2006

By C Li

Removal of gangue minerals from ilmenite concentrates can be accomplished by relatively low temperature roasting in controlled gas atmospheres to selectively enhance the magnetic separation characteristics of the ilmenite. At roasting temperatures below 800¦C the magnetising reactions are often not consistent with phase equilibria considerations. Metastable phases can nucleate and control the roasting products. In weathered ilmenites the phase assemblages and microstructures in the altered ilmenite grains can influence the roasting reactions. In this paper we give an overview of the phase chemistry of chemically weathered ilmenites and of metastable phases formed by low temperature roasting. We also report the results of roast experiments conducted in a neutral gas atmosphere. Major increases in magnetic properties after short roasting times at low temperatures were obtained for a range of ilmenite concentrates. For example heating a secondary ilmenite concentrate from Western Australia for 15 minutes in nitrogen at 600¦C gave an increase in the three kilogauss magnetic fraction from three to 92 wt per cent. The solid state phase changes accompanying the inert atmosphere roasts were characterised by combining elemental analyses with quantitative phase analyses of the ilmenite concentrates and their roast products. It was found that the phase reaction that is principally responsible for the increase in the magnetic properties of weathered ilmenites involves a transformation of disordered ferrous-containing pseudorutile to an ordered ilmenite-hematite solid solution containing typically ten to 35 mole per cent of the hematite component. Examples are given of the application of the inert atmosphere roast to effect separations of ilmenite from gangue minerals.

Jan 1, 2001

With the sinking of the No. 3 Shaft at North Broken Hill Limited, it was necessary to construct adjacent to the shaft a new changehouse for mining and surface personnel.It was also probable that as the older sections of the North and British leases were worked out, all employees at present working in these sections would be transferred to the No. 3 Shaft area. This could ultimately result in all personnel employed by North Broken Hill Limited being concentrated in this area, requiring the construction of new administration offices, workshops, mine store, etc., also in this area.

Jan 1, 1957

By N Collins, A Woodley, A N. Danoucaras, C McCombe, N C. Kunz

Over the past decade, the mining industry has come to recognise the importance of water both to itself and to others. Water accounting is a formalisation of this importance that quantifies and communicates how water is used by individual sites and the industry as a whole. While there are a number of different accounting frameworks that could be used within the industry, the Minerals Council of AustraliaÆs (MCA) water accounting framework (WAF) is an industry-led approach that provides a consistent representation of mine site water interactions regardless of their operational, social or environmental context that allows for valid comparisons between sites and companies.The WAF contains definitions of off-site water sources and destinations and on-site water use, a methodology for applying the definitions, and a set of metrics to measure site performance. The WAF is comprised of two models: the input-output model, which represents the interactions between sites and their surrounding community, and the operational model, which represents on-site water interactions.Members of the MCA have recently adopted the WAFÆs input-output model to report on their external water interactions in their Australian operations, with some adopting it on a global basis. To support this adoption, there is a need for companies to better understand how to implement the WAF in their own operations. Developing a water account is non-trivial, particularly for sites unfamiliar with the WAF or for sites with the need to represent unusual features. This work describes how to build a water account for a given site using the input-output model, with an emphasis on how to represent challenging situations.CITATION:Woodley, A, Danoucaras, A N, McCombe, C, Kunz, N C and Collins, N, 2013. A robust methodological approach for mine site water accounting, in Proceedings Water in Mining 2013 , pp 335-342 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

Mineral deposits in New Zealand whose origin can be ascribed to primary magmatic segregations are associated with mafic-ultra- mafic complexes related to two orogenic episodes which took place during Paleozoic and Mesozoic times. These mafic-ultramafic complexes are essentially of two types. One is ophiolitic and has podiform chromite mineralisation presumably formed below a spreading ridge. The other type occurs as intraplate layered intrusions in which Fe-Cu-Ni sulphides and Fe- Ti-V oxides have formed as a result of liquid immiscibility with the host magma, and have subsequently accumulated by gravity means. Generalised descriptions are given for some deposits in NW Nelson, Fiordland and Marlborough districts.

Jan 1, 1980

By S Williams, N McBride

The aim of these analyses was to utilise the latest available production information for the Wandoo operation to determine the optimal blasting parameters, costing information and predicted results (fragmentation, muckpile shape and vibration). Much of the data used as input was made available from the information gathered during the excavation of the test pits during 1995. As with any æplanning stageÆ analyses, many assumptions were required to fill gaps in the available data. The calibration of computer blasting models was conducted using data from the last of the test pit blasts (this blast was carried out in material that closely resembled rock expected to constitute the bulk of the base case design pit). This calibration was refined using observation and experience based judgements to extend the accuracy of the predictions as far as possible. All the simulations were performed assuming that the blastholes will be wet (as instructed by BGM). This has consequently determined that the appropriate explosive for the simulations and the actual blasting will be a pumped emulsion/ANFO blend. The following blast design parameters were derived by determining a likely range of powder factor (from other similar scale gold mines) with a median value of 0.62 kg/m 3 being the powder factor arrived at through the field optimisation process conducted during the test pit excavation. The total swell/displacement percentage (volume after blast/volume before blast) largely determines the diggability of a well fragmented muckpile. Consequently where fragmentation is good any reduction of total swell will probably reduce diggabilty. Any reduction of diggability can and should be traded off against increased gold recovery. In most gold mines, diggabilty will be substantially compromised at the balance which produces the most profit. When these considerations are combined with the cost to drill and blast material, processing costs and the achievement of æacceptableÆ diggibility, the analysis becomes extremely complex and qualitative. Many trends are evident including:the relationship between powder factor (for each blast design) and maximum forward displacement (throw), see Figure 1; and the relationship between powder factor (for each blast design) and drill and blast cost per BCM, see Figure 2. The following blast designs are matched to each of three ore-tonnage alternatives (as supplied by BGM) (Table 1). They are all based on powder factor of 0.62 kg/BCM and are considered optimum from a mining æpoint of viewÆ. The costing of each design includes drilling, explosives and labour cost to load, stem and tie-in holes. Using the available rock data and relying heavily on the wall exposures in the test pit(s), it is the opinion of the author that between 20 per cent to 40 per cent of the final walls excavated in the Wandoo pit would be likely to have the angle between the dominant foliation and the wall plane that is well suited to presplitting and be cost-effectively served by presplit technique. The drilling cost for 125 mm blasthole is about $11.40 per drilled metre and the cost of 40 mm presplit explosive is about $140 per 25 kg (17 metre) case. This implies that the cost to drill and blast presplit on the above parameters would be about $10.90 per square metre of presplit face. The remaining wall area would be most cost-effectively delineated using modified production blasting techniques. This requires the use of modified parameters such as smaller hole diameters, smaller spacing/ burden, higher powder factor, free face firing, less rows per blast and longer delays. These altered blast parameters would usually be applied uniformly across the entire blast fired adjacent to the wall and this ætrimÆ blast would relieve burden away from the wall, into the pit. In simplest terms, this method relies upon maximised burden relief to minimise blast energy applied to the wall. It is only applicable where the material to be blasted is waste since the throw achieved is inconsistent with ore dilution control. The largest charge weight per hole for these analyses is 360 kg and the nearest domestic structure to the proposed Wandoo pit is about 6100 metres distant. From these parameters and assuming a worst case example of rock controlled site factor, the predicted ground vibration is 0.5 mm/sec that is about five per cent of the lower limit set down in AS 2187 part two (1993). This suggests that for the current location of neighbours, ground vibration will not be an issue for the Wandoo operation.

Jan 1, 1999