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Open pit mine plans define the complex strategy of displacement of ore and waste over the mine life. Various mixed integer linear programming (MILP) formulations have been used for production scheduling of open pit mines. The main problem with these models is the inability to solve real size mining problems. We present a mixed integer linear programming formulation for the open pit long-term production scheduling problem. To reduce the number of binary integer variables in the formulation, we aggregate blocks into larger units referred to as mining-cuts. We present a semi-supervised clustering algorithm which aggregates smaller blocks based on rock types and grade ranges into mining-cuts without introducing an error in the grade estimated values. The cluster-based aggregation algorithm is fully integrated into an MILP mine production scheduling prototype software. We have implemented, verified, and validated our models. The efficiency of the new platform is evaluated through iron ore mine case study.

Dec 6, 2010

The Ediacara mineral field is classified as a Mississippi Valley type deposit with stratiform mineralization near the base of the Cambrian beds. Mineral deposition was contemporaneous with sedmentation and reerystallization, and mobilization took place after lithification of the sediments. Several mechanisms of deposition were possible.INTRODUCTIONThe Ediacara mineral field is located in the Mt. James Range approximately 300 miles north of Adelaide, about 12 miles west of Beltana railway siding and 10 miles east of Lake Torrens. It is isolated geographically from similar deposits of equivalent age and environment in the Flinders Range Province (Fig. 1). The climate may be described as semi arid with high summer temperatures and frequent dust storms. Occasional thunder storms are the main source of rain in the summer months.The exact date of discovery is unknown, but is believed to be about middle of the last century. Ulrich (1872) was the first geologist to report on the field. At that time only the southern portion of the field had been prospected (and abandoned). Although the prospects did not appear encouraging Ulrich advised prospecting of the shales and testing beneath the limestone.In 1888, Rosewarne, an Inspector of Mines, visited the Southern Workings and queried whether they were connected with some lode at deeper level or were merely bedded deposits. The first geological map with sections was drawn by H.Y.L. Brown (Brown 1892).Brown recognized three principal rock formations as dolomitic sandstone, kaolinised shales and sandstone, and quartzites and sandstone in descending order. These three basic units are still recognized. He recognized also the stratiform nature of the mineralization in the shales as a...

Jan 1, 1963

By S Winter, G Klenowski

During longwall mining in the Bowen Basin, open tension cracks formed by overburden subsidence occur to a height of about 175 m above the mining horizon. Within this zone, water in aquifers or inundated workings will flow into the mine.At the Oaky Creek mines Aquila seam, open cut pits containing pit water overlie German Creek seam longwall panels at a height of about 105 m. The highly saline water is classified as contaminated and cannot be discharged off-site. Because alternative water storage facilities were not available, innovative water management solutions were needed to allow longwall mining to proceed without underground flooding.Computer modelling and underground inflow measurements have been completed to accurately determine inflow rates into longwall mines from overlying water sources at increasing overburden heights. Research work has also included determining cost-effective blanket treatment of final voids and reshaping spoil piles to minimise downward seepage.Ponded water overlying the Aquila low, Grasstree south and A6 pits required remedial works prior to longwall undermining to prevent flooding. In the Aquila low pit it was necessary to partition the pit and remove water overlying longwall 32. Two in-pit bridges were constructed by dozing and track compacting low wall spoil. The final void above the longwall panel was kept dry during undermining. Maximum recorded underground inflow rate was 30.0 L/s.The Grasstree south pit final void, part of the ramp and much of the spoil piles were inundated prior to undermining of 308 panel. A bridge and blanket were required to prevent ponding above the longwall. Maximum recorded inflow during undermining was 23.2 L/s.The pit A6 south final void, which contained dumped, saturated rejects and inundated highwall mining entries was undermined by longwall 36 at the Oaky No 1 underground mine. Because mapping of highwall entries was not available, the maximum calculated inflow rate of 73.0 L/s was based on all design entries being fully inundated. The actual inflow rate during longwall mining ranged up to 20.0 L/s.Water management improvements that have been implemented include greater use of contaminated pit water to wash coal, use of evaporation fans, and installation of a 6 ML/day reverse osmosis plant for water purification.CITATION:Klenowski, G and Winter, S, 2017. Inflows into longwall mines from inundated overlying workings, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 183–190 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By Y Yang

This paper discusses various issues surrounding the metallurgical control for furnaces, especially focusing on processes with long time-constants and æmetallurgical memoriesÆ. Examples will focus on furnaces accepting particulate and sometimes ill-defined feeds, eg submerged-arc furnaces, blast furnaces, secondary scrap smelting operations, recycling operations, waste incinerators, etc. Generally, because of the usually higher metallurgical time constant of these furnaces, these reactors have to be controlled in a feed-forward manner by the use of a hybrid of æblack boxÆ or empirical and ægrey boxÆ semi-empirical first principles metallurgical modelling and simulation techniques in a supervisory metallurgical control capacity.

Jan 1, 2000

By G Boyd

The Nokomai Gold Mining Project commenced production in January 1992. The Project continues a history of mining in theNokomai Valley which extended from 1863 to 1942. L & M Mining Limited have held interests in the valley since 1980. In 1990 the Nokomai Joint Venture was formed with the Hore family, the owners of Nokomai Station, to mine a large alluvial gold resource in the valley. The mine is located adjacent to the Mataura Brown Trout fishery and required extensive environmental studies prior to granting of permits. The mine is budgeted to work for 20 months, processing 460 000 m3 of wash material. During this period, contract miners, Downer Mining Limited, will move in excess of seven million cubic metres of overburden from the deposit.

Jan 1, 1992

The Ministry of Commerce has been carrying out an evaluation of the resources of the Northwest Nelson region. In part this was to revisit the issues covered in the earlier proposal to close part of Northwest Nelson to mining under section 24 of the Mining Act (1971) initiated in 1990. In addition, the option of using GIS to integrate a variety of spatial data sets to aid policy formulation could be tested. The Northwest Nelson assessment would be a useful trial. The subsequent national park proposal provided a major impetus to the project and resulted in the scope of the study being broadened to include all energy and minerals resources.

Jan 1, 1993

As part or a programme to raise lead smelter capacity from 65.000 to 140.000 tons bullion per annum. one new 1000 sq. ft. updraught area sintering machine replaced eight small downdraught machines.The metallurgical specifications were based on and laboratory tests at Mount Isa. Existing practice filtering concentrate as part of the charge preparation system and discharging wet filter cake to mixing was retained. This dictated a hot return fines circuit to maintain the required feed moisture content at low return sinter ratios.The engineering specifications provided for cenlralized control of plant and process, minimum operating labour, high plant availabi;lity and highest standardsof hygeine. Crushing and conveying capacity was set to cater for the most optimistic level of sintering capacity.On start-up a number of major engineering and hygiene problems became apparent, in addition to normal teething troubles. These problems have largely been overcome and reliable operation. at less than optimum production rate is now being achieved.

Jan 1, 1968

By J Law, S Jahanshahi, R Holmes

Iron ore is AustraliaÆs largest commodity export and is vitally important to AustraliaÆs current and future prosperity. However, while major expansions are currently in progress to satisfy demand, the industry is also undergoing major transformations. Reserves of traditional high-grade Brockman ores that have underpinned the Australian iron ore industry since its inception are slowly being depleted and alternative ore types such as Marra Mamba bedded iron deposits, Yandi and Pannawonica channel iron deposits and magnetite deposits are now being developed. However, the impurity levels in some of these alternative ores are higher and they require blending and/or upgrading as well as an advanced knowledge of their downstream processing characteristics to facilitate cost-effective utilisation by overseas customers. The research challenge is to use advanced techniques for mineral exploration, ore characterisation, mineral beneficiation, agglomeration and sustainable processing to identify and develop innovative and breakthrough options for locating, unlocking and enhancing the value of AustraliaÆs iron ore resources. Furthermore, to sustain the steel industry and hence secure the demand for iron ore, there is a growing need to enhance the environmental and business performance of the industry through reductions in wastes and emissions. Therefore, cost-effective breakthrough and enabling technologies that massively cut waste generation, CO2 emissions and water consumption are also being developed. These include the use of renewable fuels and reductants, waste heat recovery and conversion of by-product slag into a saleable substitute for Portland cement. A number of examples of recent developments in the above areas are provided in this paper.CITATION:Holmes, R, Jahanshahi, S and Law, J, 2013. Research and innovation for the iron ore to carbon steel value chain, in Proceedings Iron Ore 2013 , pp 3-6 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

Real-Time Integration of Mining and Metallurgical Information for Efficient Use of Energy and Water

Sep 13, 2010

By J Zhang, O Ostrovski, C Zhang D Cai, Q Wang

The conventional CaO-SiO2-based mould fluxes are not suitable for high-Al steel casting because of the strong reaction between silica in the flux and aluminium in the steel strand. In the process of casting of high-Al steel, flux composition changes; with the decrease of the silica concentration and increase of alumina. Knowledge and understanding of the effect of the Al2O3/SiO2 ratio on flux structure and properties are useful for flux design for the high Al-steel continuous casting. This paper investigated the effect of the Al2O3/SiO2 ratio on structure, viscosity, phase composition of fluxes quenched at different temperatures and heat transfer of CaO-Al2O3-SiO2-B2O3-Na2O-Li2OMgO- F fluxes. It was found that flux melting temperature increased with the increase in Al2O3/SiO2 ratio. Viscosity of the flux melts increased significantly with the increase of the Al2O3/SiO2 ratio from 0.7 to 1.2, reaching the maximum value, and then decreased with further increase of the Al2O3/SiO2 ratio. Raman spectroscopy analysis revealed that the change of the Al2O3/SiO2 ratio led to the change of aluminate and silicate structural units. The turning point for viscosity was attributed to the change in the degree of flux polymerisation. X-ray diffraction (XRD) analysis showed that increasing Al2O3/SiO2 ratio increased crystallisation tendency of the fluxes. Heat transfer measurement by infrared emitter technique (IET) revealed that increasing Al2O3/SiO2 ratio led to the decrease in heat flux which is correlated well with the increased crystallinity of the flux. The results suggested that the flux with Al2O3/SiO2 ratio 4.3 is the best candidate among the studied CaO-Al2O3-based mould fluxes for casting of high-Al steel.

Aug 21, 2024

By D La Rosa, K Caron, H Mamani, W Valery, R Diaz

The Gold Fields Cerro Corona copper-gold deposit in Peru has heterogeneous rock characteristics in terms of its mineralogical, geological and geotechnical properties. Blast design variations in these conditions directly impact the run-of-mine (ROM) fragmentation, which in turn influences downstream process efficiencies. In particular, when harder ore is processed, throughput and circuit performance may be limited.To evaluate the potential to increase throughput and improve overall plant performance by optimising blasting practices and comminution circuit operation, Gold Fields La Cima engaged Metso Process Technology and Innovation (PTI) to conduct a full process integration and optimisation project at Cerro Corona. Blasting, crushing and grinding processes were reviewed to identify the potential to achieve substantial improvements in productivity when treating the most competent ore types.Site-specific models of the blasting, crushing and milling processes were developed using SmartTagTM ore tracking technology for calibration and validation. Ore tracking permitted locations in the blast volume to be queried against the geotechnical block model to determine the hardness and structural parameters of the feed to the comminution circuit. They also ensured surveys were conducted when ore from the audit blast was flowing through the crushing and grinding circuits.The predictive models developed enabled PTI to demonstrate how changes in blast design influenced both ROM fragmentation and the performance of downstream comminution processes. Outcomes of the project suggested changes to blast designs and comminution practices, and these were partially implemented for a validation trial. The trial demonstrated a 14.8 per cent increase in mill throughput for the specific ore selected for the study, and an average increase of 5.7 per cent for all ore types. There is potential to further increase throughput and process performance if all recommendations are implemented. This paper describes the methodology used and benefits to the operation from the mine to plant.CITATION:La Rosa, D, Caron, K, Valery, W, Diaz, R and Mamani, H, 2015. Blast fragmentation impacts on downstream processing at Goldfields Cerro Corona, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 333–342 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By B C Tanda, E A. Oraby, J J. Eksteen

"Base metal and precious metal deposits are well known for their significant geometallurgical variation throughout the volume of the proven resource. At the metallurgical level, the plant normally processes an upper oxidised layer, a transition zone and a sulfide zone, often leading to different processing techniques for the different zones. A novel processing approach is presented whereby alkaline leaching with glycine is used to leach base and precious metals, using a copper-gold ore deposit as a case study. Glycine is a cheap, non-toxic, non-volatile, highly water-soluble crystalline solid produced industrially in bulk quantities. As a chelating ligand it forms a number of stable glycinate complexes with Ni, Co, Cu, platinum group metals (PGMs), Au, Ag, Zn, Pb, Hg and Cd, with broad stability regions over an extended temperature-pH-Eh range, allowing dissolution of these metals in the neutral and alkaline regions (pH 7–13). It has been shown that this lixiviant system can leach the metals from their oxide, oxy-halide, basic sulfate, carbonate, native and various sulfide forms, including refractory sulfides such as chalcopyrite. Extraction of the metals from their soluble glycinates is easily achieved using a range of solvent extraction and precipitation processes, and the glycine remains stable in aqueous solution for recycle and reuse. Minerals bearing metals in Groups 1 to 8 of the periodic table are normally unaltered. This technology therefore provides a highly selective leaching environment for the extraction of numerous scarce metals of economic interest, with minimal interaction with gangue minerals, whilst using environmentally benign reagents. Problematic leach residues such as jarosites, elemental sulfur and silica gels are averted through this processing approach. This technology allows hydrometallurgical processing that is much less domain-sensitive in the geometallurgical sense, and utilises essentially the same key reagents for the whole deposit.CITATION:Eksteen, J J, Oraby, E A and Tanda, B C, 2016. Developing Robust Hydrometallurgical Processes to Recover Metals from Deposits with Large Geometallurgical Variation, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 15–20 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By B Crowdey, J Wall

The particular underground operation relating to this paper is a gold producer and has an orebody predominately consisting of rhyolite and marcasites pyrite. The ore has been identified as being reactive to nitrates.Operations currently utilise two twin boom Tamrock™ Super-Drill Jumbos for development mining. Capital (waste) headings have a nominal size of 7 m wide × 6 m high, while ore headings are designed at 5 m wide × 5 m high, with the lower reaches of the mine narrowing down to a 4.5 m × 5 m design. Production drilling is currently undertaken with an Atlas-Copco L6 Solo. Due to the reactivity of the ore, inhibited emulsion phase bulk explosives are used for all blasting activities, with electronic detonators utilised in the production sequence.Sublevel shrinkage stoping is utilised when the orebody is stronger than the host rock. After blasting the ore, and during extraction, the surrounding host rock cannot maintain integrity and it ‘collapses’ on top of the ore. Gravity forces this collapsing rock to follow the blasted ore through the drawpoints.The highest risk involved with sublevel shrinkage stoping is the necessity for charge crews to work upon ‘rills’ at the drawpoints, which are occasionally unstable, to charge the next blast ring to be fired. To overcome this issue a loading technique called ‘precharging’ is used whereby two to three rings are charged, but only the first ring is fired. This technique can minimise risks by taking the charge crew away from the rill and brow.As this mine contains hot and reactive ground, strict guidelines from the Australian Explosives Industry and Safety Group Inc (AEISG) are adhered to. These guidelines relate to the sleep time for the precharged rings.This paper describes the issues faced with precharging in hot and reactive ground, the monitoring required and the systems and procedures that were put in place to enable a successful outcome.CITATION:Crowdey, B and Wall, J, 2014. Precharging sublevel shrinkage production rings in hot and reactive ground with electronic blasting systems, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 283–288 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By B Crompton, A Berghorst, G Knox

Laboratory-based dynamic testing provides an invaluable tool in the development of rock bolts for use in highly stressed, burst prone rock masses. While in most cases the laboratory-based test method is not a direct comparison to an in-situ installation due to the purely axial loading and variations in boundary conditions, it does provide an indication of the performance of the tendon system under dynamic loading. The aim of the research described in this paper is to provide an understanding of the effect of the impact velocity of the impact mass during a laboratory-based dynamic test. Understanding the effect of boundary conditions of laboratory testing will improve Geotechnical Engineers understanding of the performance in an in-situ installation. In addition, due to the limited number of dynamic test facilities, an understanding of the effects of the boundary conditions will aid in the comparison of test results for different products from different test facilities. The research was conducted using an impact tester, whereby a known mass is raised to a known height defining the kinetic energy and velocity of the mass at the point of impact with the test sample after release. The impact velocity was varied between 2.7 m/s and 5.4 m/s, while the kinetic energy of the mass was maintained at 11.5 kJ. While a correlation between the impact velocity and strain rate of the system tested was established, due to the properties of the system tested, the range of impact velocity on which dynamic tests were conducted was insufficient to result in a considerable change in the average impact load, the cumulative proximal displacement and the cumulative maximum energy absorbed over multiple impulse. However, due to the reduction in the momentum of the impact mass the impact duration and displacement during each impulse in the series of impulses reduced. CITATION:Knox, G, Berghorst, A and Crompton, B, 2018. The relationship between the magnitude of impact velocity per impulse and cumulative absorbed energy capacity of a rock bolt, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 160–169 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By J Thoma, W Skinner, W Stewart, R Smart

The acid neutralisation capacity (ANC) of rock sample containing significant iron carbonates and/or reactive framboidal pyrite can be a difficult parameter to determine. Results indicated that negative ANC results can occur if reactive sulfide minerals are present; and an over-estimation of ANC will result if significant Fe rich carbonate minerals are present during industry standard ANC tests. In this paper we investigate these problems. Results showed that a significant lag period may be needed (up to 432 hours) after standard Sobek ANC type tests of siderite for the complete hydrolysis of iron released from this mineral. This even occurred with standard industry modifications that included the addition of two drops of hydrogen peroxide. In this work we use a modified Sobek test that included filtering, and thence continued hydrogen peroxide addition until there was no subsequent pH drop, followed by back titration to pH 7.0. Results indicated that the ANC for the siderite (after zero hours) was immediately comparable to the ANC determined after 432 hours lag by standard Sobek type tests; and a calculated theoretical carbonate ANC. Investigations of coal waste samples containing significant framboidal pyrite indicated that standard Sobek ANC type tests can result in negative ANC values due to the oxidation of this reactive pyrite. Because sulfide acidity is already addressed by the MPA calculation, the inclusion of sulfide acidity as part of the ANC determination is effectively biased towards acid generation and thus positive NAPP values. Negative ANC values cannot be ignored or assumed to be zero as this masks any actual ANC available within the sample, which may possibly affect AMD categorisation. This sulfide acidity can be factored out using the quantity of S in the ANC digestion liquor and knowing the non-acid generating sulfate content of the sample prior to ANC testing. Results indicated that incomplete iron hydrolysis at the completion of the Modified Sobek ANC test is not only a function of iron carbonate dissolution, but is also related to the dissolution of Fe-sulfate salts, and the oxidation of reactive sulfides such as framboidal pyrite.

Jan 1, 2003

By I Zh Bunin, V A. Chanturia, V G. Minenko, M V. Ryazantseva, A L. Samusev

A promising source for the extraction of rare metals and REEs in Russia is the eudialyte ores of the Lovozero deposit, which do not contain active uranium components. The eudialyte ore reserves of the Lovozero Massif are considered virtually unlimited and therefore have the potential to become a primary source of a number of rare and rare earth metals. The goal of this study was to comprehensively examine the effect of the parameters of high-power nanosecond electromagnetic pulses (HPEMP) and dielectric barrier discharge (DBD) on the leaching performance of eudialyte concentrate and the selective separation of zirconium and REEs from productive solutions. Using scanning electron microscopy and infrared spectroscopy, the mechanism behind the intensification of acidic dissolution of eudialyte as a result of pretreatment with energy impacts was described. During the HPEMP treatment, weakening and destruction of the eudialyte surface was observed, which at the substructural level is expressed in the deformation and local destruction of Si10O27, Si9MO30 resulting in formation of microcracks. During the DBD treatment, the formation of characteristic defects was observed in the form of imprints of dielectric breakdown microchannels and individual mineral fragments. Pretreatment of eudialyte concentrate using HPEMP made it possible to increase the recovery of zirconium into the pregnant solution of leaching by 3.4–4.3 per cent (from 86.6 per cent to 90.9 per cent) and by 4.1 per cent (from 86.6 per cent to 90.6 per cent) when using DBD. The increase in the total recovery of REEs was 1.2–1.8 per cent (from 87.7 per cent to 89.2 per cent). The effect of pH values, solution temperature, initial concentrations of valuable components on the successive recovery performance of zirconium and REEs from the pregnant solutions nitric from the acid leaching of eudialyte concentrate by chemical precipitation was examined. The possibility of selective separation of the zirconium product and rare earth elements with a zirconium recovery of 99.95 per cent and a REE recovery of 87.5 per cent was established. REE loss with the zirconium product was 8.0 per cent and 4.5 per cent with the spent pregnant solution.

Aug 24, 2022

By R J. Soriano, S Ciutina

The Masbate gold deposits are situated on the island of Masbate, 350 km south of Manila. A new plant was commissioned in April 2009. The grinding circuit consists of one semi-autogenous (SAG) mill Ø9.75 m × 4.27 m, two ball mills Ø5.6 m × 7.1 m and a pebble crushing circuit, which is usually called a SAG-ball mill-crusher configuration. The SAG mill was originally equipped with radial pulp lifters. The mill runs at fixed speed of 10.9 rev/min, which is approximately 80 per cent of critical speed (per cent CS). Due to the high speed of the mill the original radial design pulp lifters presented a high volume of recirculating load inside the chamber and consequently heavy wear on the outer circle (bottom pan).In order to address the high wear on the pulp lifters a number of avenues were considered in early 2011. The chosen solution was to change the geometry of pulp lifters from radial to curved design. The pre-existing drilling pattern on the discharge end of the mill was a major constraint. A number of designs were considered. The selection of the most suitable option was to be made based on 3D discrete element modelling (DEM) and smoothed particle hydrodynamic (SPH) simulations.The original radial design and two potential solutions for curved pulp lifters were simulated with 3D DEM and SPH software. The main three objectives were predicting the charge dynamics, the expected wear patterns and discharge efficiency. One of the solutions was chosen and implemented during 2012.Observations carried on after installation of the curved pulp lifters have confirmed, as expected, a reduction in wear intensity on the outer pulp lifters. In addition to this, at early stages of operation with curved pulp lifters, the mill operator noticed a reduction in energy consumed by the mill with no detrimental effect on mill performance.This paper is intended to further study the effect of curved pulp lifters on mill energy consumption.CITATION:Ciutina, S and Soriano, R J, 2014. Curved pulp lifters – can they save energy?, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 109–116 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By D Timms

The Kempfield deposit is located in the Hill End Trough, one of several intracratonic basins developed during Silurian–Devonian time, in the eastern province of the Lachlan Orogen, Eastern Australia.The deposit contains an oxide resource of 5.8 Mt @ 58 g/t Ag and a sulfide resource of 14.4 Mt @ 45 g/t Ag, 1.7 per cent Zn and 0.6 per cent Pb, classified and reported in compliance with the JORC Code. The deposit has been previously explored by a number of companies, including INCO, Shell, Jones Mining, Golden Cross Resources and recently Argent Minerals Ltd (Argent). Argent is currently completing a definitive feasibility study with a view to mining the deposit.The deposit is hosted at the boundary between the Molong High to the west, comprising Ordovician sediments and volcanic rocks and the Hill End Trough to the east, interpreted as a back-arc basin containing Silurian sediments and siliceous-feldspathic volcanic rocks. The boundary between these two strato tectonic units is an imbricate thrust fault zone known as the Copperhannia Thrust.The Kempfield deposit is hosted in felsic volcanic rocks known as the Kangaloolah Volcanics. These have been in-faulted and folded into the Middle Ordovician meta-sediments of the Coombing Formation of metasediments along the Copperhannia Thrust. The Kangaloolah Volcanics belong to the Late Silurian Mumbil Group, comprising submarine carbonate-shale facies interspersed with extensive felsic volcanic piles, which grade conformably upwards into turbiditic sandstone and siltstone sequences (interpreted to represent a deeper depositional environment). These turbiditic rocks are known as the Campbells Formation, comprising siltstone, sandstone and andesitic tuff. The rocks at Kempfield are metamorphosed to lower greenschist facies, reflected through the different type of schists.Silver, gold, lead, zinc mineralisation is hosted in barite-rich horizons, near the boundary to quartz-phyric tuffaceous rocks in submarine, immature, reworked felsic ash tuffs. Barite appears to be hosted in greatest concentrations by the coarser grained volcanoclastic sandstones and grits, whilst intercalated siltstones are volumetrically minor and tend to return low barite and silver. Mineralisation is hosted in stratiform and probably stratabound barite-rich horizons. A northeast-trending, steeply dipping, metamorphic cleavage (S1) occurs throughout the project area.

Aug 22, 2011

By D J. Kilkenny

Work practices involved in shaft construction can be aligned with current industry standard operating practices. However, the working environment during conventional shaft construction introduces unique conditions which can not always be overcome by hard engineering controls. To provide an improved working environment, future shaft diameters will generally be greater than has historically been the case for the Australian hard rock mining industry. This paper aims to explore both what can be constructed from the contractors perspective, and how does an owner extract maximum business efficiency from an asset that in many ways is likely to be larger, more complex and more expensive than initially envisaged.Newcrest Mining Limited, or an associated company, has constructed two major shafts over the last seven years. In both cases, Byrnecut Mining, or an associated company, was the contractor engaged for the shaft sinking activity. The first is the 1127 m deep, 7.0 m diameter production and intake airway at the Telfer Gold Mine, the second is a 295 m deep, 5.5 m diameter split shaft at the Gosowong Gold Project in Indonesia that was primarily designed as both an intake and exhaust airway. Importantly both shafts are designed to provide emergency egress from the respective underground operations.From an Australian shaft sinking perspective, the construction of these two shafts resulted in the following learnings: •constructability is of equal importance to desired functionality;•allow six months of interactive design between the owner/engineer/contractor/regulator to get it right;•shaft sinking and equipping are intimately entwined, therefore engineering of both needs to be complete prior to any activity commencing; and•the mobilisation of both equipment and experienced personnel to a new shaft sink takes up to eight months.Shaft sinking is not extinct in the Australian hard rock mining industry. But, if you are considering constructing a shaft, approach it as a long life asset, front end planning to a high level of detail is required to unlock its full value. Think – plan – think and remember it’s going to take 12 months to get from the whiteboard to firing the first cut.

Mar 21, 2011

By C Harrison, A Bowskill

The Ambuklao hydroelectric dam was originally constructed in the 1950s in the remote and mountainous region of the northern Philippines. Following its construction the dam has suffered heavily due to siltation and a partial collapse of the intake structure due to a 7.8 magnitude earthquake that struck the region in 1990. Between the years 1990 and 1999 the power station progressively lost its capacity to generate power. In 1999 the owner took the power station out of commission. The power station remained idle over the next 12 years. In 2008 the power station was sold to a new owner who commissioned the rehabilitation works.The rehabilitation project restored the operating status of the power station in June 2011 and increased its capacity from 75 MW to 105 MW. The civil contract of the rehabilitation project required the construction of a new intake structure behind an in situ rock coffer dam on the edge of the existing reservoir, new 6.2?m diameter × 124?m deep blind sunk shaft behind the intake structure, which connects to a new 6.8?m horseshoe profile headrace tunnel that ultimately connected onto the existing vertical penstocks which feed three No 35 MW Horizontal Turbines rated at 155?m head.The unique challenge in rehabilitating this existing hydropower station involved finding solutions that would conclusively deal with the challenging geological and hydrogeological conditions associated with excavating new tunnels and a drop shaft beneath a live dam.McConnell Dowell was awarded the civil works package for the rehabilitation works in August 2008. The Ambuklao rehabilitation program took 33 months to complete.Over 600?m of tunnels were excavated in highly weathered and often challenging geotechnical conditions via drill and blast with the extensive use of high-pressure fissure grouting to control groundwater ingress that was surcharged by the dam.This paper focuses on the use of high-pressure fissure grouting that took place to enable the excavation of the new waterway system and intake structure.CITATION:Bowskill, A and Harrison, C, 2014. High-pressure fissure grouting for drill and blast tunnelling, Ambuklao, Philippines, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 141–152 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014