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By B Jones, M Chappell

Installing ground support correctly is not an easy task, whether lack of operator training, poor ground conditions or underperforming equipment. Confirming the quality of installation can help with planning and remedial works and help to maintain a safe working environment. A 2?m bolt with 700?mm of encapsulation will pass a 10?t pull test (assuming ground conditions permit); however, it will not provide any data of the unencapsulated length and thus the ability to withstand corrosion. Complimentary testing in the form of non-destructive testing (NDT) can provide factual data that leads to the assessment of the quality of the encapsulation. By improving the quality of the encapsulation, the risk of corrosion is reduced, the ground support durability is improved and hence the asset life is enhanced.This paper presents a case study of a trial using the NDT system RokTel™. Installations of varying quality were installed and tested. The characteristics tested were corrosion, load and free length. These characteristics can be tested and assessed for cable bolts, thread bar bolts and split sets. The aim of this paper is to present NDT testing as a viable method for assessing installation quality and ongoing performance of the ground support.CITATION:Jones, B and Chappell, M, 2014. A non-destructive testing method for measuring bolt condition, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 307–314 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By H Utama, hi, A Suw

PT. Indo Muro Kencana (PT.IMK) is gold and silver mine located in Central Kalimantan province, Indonesia. Mining activities in PT.IMK is conducted in Bantian pit area by applying surface mining method and using combination of excavator and hauler (articulated dump truck and rigid haul truck) as the transportation for ore to the crushing plant and waste material to the waste dump. Current blasting practice is ore-waste blasting. Ore-waste blasting is the term where the ore and waste rock are blasted in the same blasting process. Blasting is conducted by using nonel initiation system. By multiple pits operation, monthly powder factor is varied from 0.23 kg/t to 0.27 kg/t. Emulsion blend with density 1.15 g/cc is used as bulk explosive. At this stage, the concept of geoblast is proposed as an engineering tool for Drill and Blast engineering practice in PT.IMK. In addition, there is a need to maintain rock fragmentation by blasting, to maintain monthly powder factor, and to maintain excavator’s productivity. Next, the concept of scaled depth of burial (Chiappetta and Treleven, 1997) and the concept of blastability index (Lilly, 1986) are proposed as geoblast’s tools to improve blasting practice in PT.IMK. It is expected that rock fragmentation by blasting, explosive consumption and excavator’s productivity will be maintained by integration of geoblast and drill and blast engineering. Furthermore, the objective of this paper is to integrate geoblast and drill and blast engineering in order to create an engineering guideline in PT.IMK. Additionally, blasting trials with air decking application is proposed in order to support the geoblast’s improvement. It is planned that these blasting trials will be conducted in 2022. In conclusion, it can be seen that integration of geoblast and D&B engineering in PT.IMK is relevant to improve current drill and blast current practice and applicable to maintain rock fragmentation by blasting.

Nov 29, 2022

The Wattle Dam gold mine, located near Kambalda in the Goldfi elds region of Western Australia has recently progressed to an underground operation and is now believed to be Australia's highest grade operating gold mine. At end of March 2010, the deposit had reserves of 132 000 t @ 20.8 g/t for 88 000 oz and by the end of June 2010 had produced 110 000 oz from open-pit and underground mining. The Wattle Dam main lode is characterised by very coarse gold mineralisation. Gold occurs as cm to decimetre fracture fi ll veinlets, shear surface coatings and erratic fl akey clusters. The gold has no quartz or silica association and lacks adjacent low-grade mineralisation or alteration assemblage. Geologically it appears atypical of Archaean lode gold deposits and may represent an extreme end member of the type. Definition of the lode is largely dependent on effective geological identification of the host lode zone and an understanding of the erratic distribution and grade behaviour of a high-nugget, coarse gold deposit. Dependence on assay data to defi ne the lode zone would result in the deposit being mined incorrectly and much of the deposit being left unexploited. This paper discusses the geology, coarse gold characteristics and defi nition methods which are used to successfully defi ne and mine the deposit.

Aug 1, 2010

By B L. Coulter, E Wightman, A S. Burrows

With their commitment to sustainable development in an increasingly carbon-constrained world, many resources companies are focused on reducing the energy required to create their final products. In particular, the comminution and smelting of metal-bearing ores are both highly energy-intensive processes. If resource companies can optimise the energy efficiency across these two processing stages, they can directly reduce their overall energy consumption per unit mass of metal produced and thus reduce their greenhouse gas footprint. Traditional grinding and flotation models seek to improve the efficiency of mineral processing, but they do not consider the energy used by downstream metal production, eg smelting and refining. Concentrators and smelters individually may be running efficiently, but are they optimising energy consumption of the overall system? A key step towards answering this question is to understand whether it takes less energy to remove an impurity in the concentrator or the smelter. Analysis of the complete concentrator û smelter process chain may show that there are times when the concentrator should use more energy to reduce the overall energy requirements across the mill and smelter. The new methodology discussed here will integrate downstream processing energy with mineral processing energy, to find the overall most energy efficient circuit design and operating strategy. The proposed methodology includes: determining what grade and recovery positions can be achieved in the concentrator by using different combinations and amounts of grinding and regrinding, thermodynamic calculations of the energy used to process the different concentrate grades to metal, and integrating the concentrating and smelting models to find the lowest total energy for the system. A case study which investigates the effect of increasing regrinding energy on the overall mineral processing û smelting energy consumption is presented. For the copper-nickel sulfide ore investigated the addition of regrinding results in 11 per cent less energy being used in the overall concentrator û smelter process chain per tonne of metal produced. Although regrinding is often seen as an energy-intensive process, in this case study the use of 1 kWh of energy for regrinding reduces the overall energy consumption by 12 kWh. The new mill to melt methodology will allow companies to model energy consumption from mill to smelter with a view to reducing the energy-intensity and greenhouse gas footprint of their processing and smelting operations.

Jan 1, 2009

By R Shaw

There are many small to medium carbonate hosted complex zinc containing deposits where the zinc is not economically recoverable either as concentrate or metal. High grade (>20% Zn) run of mine ore can be processed but even this material gives relatively poor returns. Considerable effort has gone into developing new technology for either upgrading the ore and/or recovering zinc metal hydrometallurgically but there has been limited success. Minetometal has developed a process capable of economically treating these deposits to give marketable lead and zinc products. This paper reviews alternative processes for these ores and gives a detailed description of the Minetometal Process. CITATION: Shaw, R, 2018. Processing carbonate hosted zinc-lead ores, in Proceedings Complex Orebodies Conference 2018, pp 130–131 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

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 M Randall, P Ebzery, F Burns, C Aisthorpe, P Blanz

SAG Mill process control classically maintains the SAG mill volumetric filling within a set operating range. Typically a SAG mill weight measurement, by either bearing pressure transducers or load cells, is used as an inferred measurement of volumetric filling. To maintain volumetric filling within a set operating range the SAG weight setpoint use for process control requires regular review due to changes in SAG mill charge density (rock:ball ratio) and the wearing of mill liners. At Lihir Gold Mine in Papua New Guinea, the use of SAG mill weight for process control is additionally complicated by compromised load cells and drifting bearing pressure measurements. The need for an improved method of measuring and controlling volumetric filling led to the recent installation of the Outotec MillSense, a SAG mill toe angle instrument. This paper presents the integration of the toe angle control in to the Lihir SAG mill process control philosophy as replacement for the traditional mill weight control.CITATION:Burns, F, Aisthorpe, C, Blanz, P, Randall, M and Ebzery, P, 2018. Toe angle measurement for SAG mill control at Lihir gold mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 59–76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

When, in 1985, Marty McFly is accidentally sent back to 1955 in a DeLorean ‘time machine’ in Back to the Future, he encounters young versions of his parents, and must make sure they fall in love or he will cease to exist. This Conference celebrates 40 years since the inaugural Mill Operators’ Conference in Mt Isa in 1978; over this period, great technological advances have been made in almost all aspects of mill operation, resulting in considerable improvements in grades and recoveries from ever-more complex ores. However, in 2018, the mining industry is facing challenges that might have been difficult to predict in 1978 (or were they?). The computer revolution, the information revolution, and the bio-technology revolution have all contributed to the increase in operating efficiencies, but, combined with the social revolution, they also call into question the existence of the mining industry as we know it. This presentation looks back at the ‘way things were’ in the 1970s, and at what was then considered to be the ‘basics,’ and attempts to sketch what the mining industry might be like in 2058. As Back to the Future Part II demonstrates so vividly, it is much easier to review the past than predict the future. It is difficult to know what form the mining industry will have in 40 years’ time. Nevertheless, as this presentation will argue, it is important to take action now, to ensure that it (like Marty McFly) does not cease to exist. Some courses of action are proposed, including going back to the basics of a very different past.*This is an abstract only. No full paper was prepared for this abstract.*CITATION:Franzidis, J P, 2018. Back to basics or back to the future?, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 3–4 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By X Hu, J Björkvall, L Sundqvist Ökvist

The metal production industry is a significant contributor to global CO2 emissions due to the use of fossil fuels such as coal and coke. To mitigate these emissions and meet climate goals, innovative and sustainable technologies are required. Molten salt electrolysis is a promising technology that directly produces metals from their precursor sulfides or oxides using electricity. When combined with renewable electricity and an inert anode, the electrolysis process can be carbon neutral. This paper presents the results of two pilot-scale studies on the electrolytic reduction of metal oxides and sulfides in molten salts. The first study focuses on the electrolytic reduction of chalcopyrite in molten NaCl-KCl salt. The results demonstrate that in situ separation of copper, iron, and sulfur is possible, enabling the extraction of all valuable elements without CO2 emissions. Furthermore, the findings underscore the capability to eliminate impurities like zinc, antimony, arsenic, and mercury from the electrolysis product. The second study investigates the electrolytic reduction of pure/synthetic chemicals of wüstite, hematite, and magnetite, as well as a magnetite-type iron ore in molten NaOH salt. The findings reveal a stepwise reduction of iron oxides from high valence to low valence, ultimately leading to the production of metallic iron electrolytically. Notably, this study underscores the challenges associated with the selection of an economically viable and durable inert anode material for efficient oxygen generation. These results indicate that molten salt electrolysis provides a sustainable and green route for base metal production. The use of this technology has the potential to significantly reduce CO2 emissions in the metal production industry, contributing to achieving climate goals.

Jun 19, 2024

By L Nicholls, A Parbhakar-Fox

Reprocessing Queensland’s historical copper tailings for critical minerals is an opportunity to circularise the state’s mining industry by converting waste liabilities into assets. Mine waste valorisation enables economic rehabilitation of legacy mining sites, improves environmental outcomes, and can establish a secondary resources sector that produces a sustainable supply of critical minerals to supplement growing global demands (Australian Government, 2023). The North-West Queensland Minerals Province (NWQMP) hosts numerous copper mines with known cobalt mineralisation (Degeling, 2020). Cobalt is a critical metal essential for green energy and battery technologies, however its global supply is at risk due to geopolitical and ethical concerns (Rachidi et al, 2021). Historically mining in the NWQMP has focused on copper, leaving cobalt to theoretically accumulate in the mine waste. First-pass geometallurgical characterisation of waste repositories by the Sustainable Minerals Institute identified Capricorn Copper as a key site for further investigation into cobalt deportment and recovery potential.

Aug 2, 2023

By A Kobzev, C Robben

Sensor-based particle sorting of gold ores is the masterclass of preconcentration. The technical challenges of a grade in ppm scale makes a direct detection with currently available technology in milliseconds impossible. Consequently, the detection and classification of particles into ore and waste classes relies on detectable proxies which are the foundation for the classification. These must be reliable and repeatable across the ore bodies processed in future. A sensor-based particle ore sorting equipment must therefore be calibrated systematically by understanding the gold deportation in different lithological groups. Also, it must be in best operational state to minimise possible misplacement. The technical challenges are met by a stringent financial regime governing the business case. Many gold ore sorting projects require a stable grade of gold in the rejected waste significantly below 1gr/t. Two examples are introduced in this paper:  The pilot results and operational experience of X-ray transmission (XRT)-based particle ore sorting for pebble sorting of sulphide associated ore;  Laser-based particle ore sorting for pebble circuit of an orogenic, quartz associated gold ore. Usually, sensor-based particle sorters are installed in the crushing section of a plant. However, for large capacity plants, the number of equipment required, and the associated material handling costs result in significant capital and operating expenses for plants with 1200tph run-of-mine capacity. As a conclusion, it was decided to investigate sensor-based particle ore sorting applied to the pebble stream of two existing semi autogenous mills.

Nov 10, 2020

The objectives of mining grade control are presented and examples of the techniques used in various open pit and underground mines are used to define the attributes of good grade control. Reasons are discussed for the success of various improved practices. The progressive development of grade control is presented and the balance between quantitative and qualitative data is analysed. The skills and resources required for grade control on mine sites that are using best practice are also presented. A number of problems in grade control have been solved recently however there are still issues that need to be addressed. Examination of the grade control process frequently stops after sample quality has been examined. There is much more beyond this that can now be optimised using conditional simulation models. Other future directions of mining grade control are also suggested. An extensive bibliography of published papers on grade control is included that will be maintained and updated on a website.

Jan 1, 2000

The chief use of manganese ore is in the production of ferromanganese alloys for steelmaking. Manganese ores generally occur in tropical areas, which influences the type of treatment required. Present methods of treatment are relatively unsophist- icated but demands by customers for tighter specifications will necessitate the installation of gravity concentrator at many mines At present only limited tonnages of minus j in. product can be sold hence future development will centre around methods of producing an agglomerate satisfactory to the smelter.

Jan 1, 1969

The epithermal silver-gold Red Rock Deposit is hosted in the Late Permian inter- mediate to silicic composition Drake Volcanics of New England, N.S.W. This deposit represents one of the few low sulfur epithermal precious metal systems in eastern Australia, and differ! from epithermal models in that the hydrotherma: system which produced mineralization was active in a shallow water marine environment. The Red Rock Deposit has a resource of 180,000 tonnes of 66g/t Ag and 0.9 g/t Au, and a Ag:Au ratio of 70:1. Mineralization is largely associated with hydrothermal brecciation, and occurs as disseminations, vein stockworks, and struc- turally controlled lodes. Ore minerals comprise acanthite (argentite), electrum, native Ag, Ag- sulfosalts and base metal sulfides, Alteration minerals associated with ore are quartz, cal- cite, adularia, pyrite, illite, illite-mont- morillonite, chlorite and sphene (leucoxene). Illitic and propylitic alteration zones sur- round the hydrothermal breccia. Bulk rock analyses indicate that alteration is character- ized by the addition of Si, K, Fe, Mg and the loss of Na and Ca. Ore was deposited from a boiling fluid in a temperature range of 222- 295¦C, and of 0.5-7 wt. Z NaCl equivalent sal- inity. An upper hydrostatic depth limit of about 800 m is implied for the boiling fluid ii an open vein. Sulfur isotopes indicate a mag- matic sulfur source, and oxygen isotopes imply a predominantly marine ore fluid. Modern analogs of the submarine hydrothermal system that formed the Red Rock Deposit occur in the Taupo Zone, New Zealand, and southern Kyushu, Japan.

Jan 1, 1987

By J Cortinez, P Vallejos, J Yianatos, M Rodriguez

Nowadays, one of the main problems in current flotation plants and new projects is the significant decrease in feed grades and changes in the mineral composition, which has an important effect on the mineral liberation and associations. Additionally, flotation plants usually operate with feed throughput higher than the original design, which has a significant impact on the feed particle size. All these conditions affect metallurgical performance, and must be evaluated and addressed, by improving control strategies for banks optimisation. For this purpose, the flotation of valuable minerals along the circuits requires better understanding, considering the compromise between performance and selectivity in flotation circuits. This paper presents a characterisation of the different minerals recovered along industrial flotation circuits. Plant sampling campaigns, performed in a copper industrial concentrator in Chile, provided the data for the study. Two rougher flotation banks consisting of cells of 130 m3 and 300 m3 were analysed. All the samples from the industrial surveys were analysed by screening and mineralogy, and the mineral recovery along the circuits was evaluated per particle size class, liberation class, type of associations, and others. Additionally, operating data on froth depth profiles complemented the evaluation of the mineral composition of concentrate streams, along the circuit. The results allowed for identifying and quantifying the main factors that affect the copper recovery and concentrate grade along the flotation banks. It was found that minerals with liberation lower than 50 per cent have a significant impact on the recovery. On the other hand, the decrease in the Cu grade in concentrates along the flotation circuits is mainly due to the relative increase of middling minerals (less liberated), non-valuable floatable minerals, such as free pyrite, and gangue entrainment. The characterisation of the gangue entrainment flow rate along the flotation banks showed a strong relationship with froth depth, which becomes more critical towards the last cells of the banks.

Aug 24, 2022

By D Davis

The prediction of ground-borne noise levels from tunnel construction activities requires knowledge of the input vibration forces from the vibration source(s) into the cutting face, knowledge of the vibration transmissibility through the surrounding medium, and knowledge of the receiver building’s vibro-acoustic response. The conversion of this vibration energy into sound pressure within the receiver building depends upon the vibration coupling of the soil and the building’s foundations, the structure’s response including floor-to-floor attenuation and amplifi cation due to resonance, the radiation effi ciencies of the internal structural elements, and the room’s acoustical properties. Beginning with a known input vibration spectrum at the cutting face, it is possible to predict the resultant ground-borne noise levels within a receiver building using either analytical and/or empirical techniques, or by numerical modelling. This paper presents an overview of the various methods available to estimate ground-borne noise levels from tunnel construction activities and discusses the advantages and limitations of each.

Mar 8, 2011

By A K. B Opitz, M Becker, J L. Broadhurst

"One of the key drivers of geometallurgy is to define the ore characteristics and their variability to build a geometallurgical model. The inclusion of waste rock properties and their variability is just as important, given that the generation of acid rock drainage (ARD) poses one of the most significant environmental challenges facing the mining industry. Formed through the oxidation of sulfide minerals in the presence of oxygen and water, ARD generation is exacerbated through the regeneration of lixiviates by naturally occurring iron- and sulfur-oxidising micro-organisms. In order to manage the potential risk of ARD pollution, timely, accurate, reliable and robust characterisation and prediction of the ARD potential of waste material is critical from an early stage in the mining process.This study demonstrates the use of the biokinetic-accelerated weathering test developed at the University of Cape Town to characterise the ARD potentials of gold waste rock samples under microbial conditions. These tests are performed in conjunction with standard characterisation tests to provide an indication of the potential for ARD generation under both chemical and biological conditions. Results provided information regarding the relative rates of acid neutralisation and acid generation, with the contribution of specific minerals to the observed behaviour considered through use of a detailed mineralogical assessment. Overall, the addition of the biokinetic test to the current geometallurgical characterisation and prediction toolbox will allow for relatively rapid assessment of the bulk kinetics of ARD generation.CITATION:Opitz, A K B, Becker, M, Broadhurst, J L, Bradshaw, D J and Harrison, S T L, 2016. The Biokinetic Test as a Geometallurgical Indicator for Acid Rock Drainage Potentials, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 183–192 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By P Holtham, K C. Runge, E Tabosa

Traditionally, comminution and flotation have been surveyed, analysed and optimised separately. This often results in less than optimal outcomes because of the complex interactions between the two processes. Flotation recovery is a strong function of the valuable mineral particle size distribution with lower recovery of ultra-fines due to poor flotation kinetics, optimum recovery for the intermediate sized particles and lower recovery for the coarser particles due to poorer liberation. Thus, to optimise flotation recovery and grade it is usually best to grind to a fine size. This requirement needs to be balanced by the cost of grinding finer and the revenue that results from an increase in grinding throughput, which often results in a coarsening of the flotation feed.This paper demonstrates a technique which can be used to predict the effect of a change in feed grind size on flotation performance. It can be used to determine the optimum grind size for a particular operation which optimises total circuit profitability. Analysis is relatively easy to perform, as a minimum, requiring only size by assay data of the feed and product streams of the process. Case studies will be presented that demonstrate the usefulness of this technique in feed grind applications. Potential use of the technique for regrind evaluation is discussed. The limitations associated with this technique in certain circuit scenarios will also be outlined.CITATION:Runge, K C, Tabosa, E and Holtham, P, 2014. Integrated optimisation of grinding and flotation circuits, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 77–84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By S Gillies, H W. Wu

A study has been undertaken into mine ventilation systems currently in use within Australian modern coal longwall (LW) extraction mines. It reviews systems and discusses evolving changes being adopted to address the more complex challenges. There is a strong move to longer panels, wider faces, greater extraction heights, increased production rates, more efficient ventilation and decreased personnel. Each of these changes is motivated by improvement in productivity and generally leads to cost reduction. In addition, mine workings are moving deeper, which results in increased ventilation control issues such as higher total and respirable dust levels, greater seam gas contents in parallel with lower in situ permeabilities, spontaneous combustion and heat management issues. A comprehensive database of Australian LW ventilation practice is analysed. Currently there are a variety of LW panel ventilation circuits used in Australian underground coal mines due to various combinations of seam characteristics, gas emission rates, spontaneous combustion, geological features and surface constraints. The main issues usually addressed in the designing and planning of ventilation circuits for LW panels are airway velocity, gas concentrations, LW cutting methods (eg Bi-di, Uni-di or half web), ventilation of control devices, pressure differentials and leakage paths and understanding gas concentrations across the length and width of the goaf. If the ventilation circuit can manage the applied contaminant load (gases, heat and dust) at an acceptable cost and circuit duty, then supplementary controls, such as gas drainage, refrigeration and dust sprays and scrubbers, may not be required. CITATION:Gillies, S and Wu, H W, 2013. Review of Australian longwall panel ventilation practices, in Proceedings The Australian Mine Ventilation Conference , pp 87-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By K Henley

One of the greatest practical difficulties of measuring airblast occurs when a significant wind is blowing onto the microphone. Small windscreens are usually used to mitigate the wind noise on the microphone, but in some wind conditions, sound pressure levels (SPL) of over 120 decibel (linear) are frequently recorded. There are no specific procedures to mitigate the effect of wind noise when measuring airblast in any of the standards or guidelines pertaining to the measurement of airblast from blasting operations, other than the requirement to use an effective windscreen. A search for relevant literature was undertaken and measurements were taken over a period of six months at a test site using alternative microphone measurement methods. Previous researchers’ experiments with windscreens in silenced wind tunnels showed that wind noise can be reduced through the use of large diameter windscreens, and that at low frequencies, the windscreen size and the material type makes no difference to measured SPL values. Other researchers found that wind turbulence caused significant SPL measurement problems. A comparison with field data failed to explain the extremely high SPL recorded by the field microphones at wind velocities much lower than those used in wind tunnel testing. It has been concluded that turbulent airflow over and behind the microphone is a significant contributor to extraneous noise in airblast measurements in windy conditions. This turbulence can be generated by objects upwind of the microphone or by the microphone itself if the windscreen is ineffective. Reducing the wind speed over the microphone by placing it on the ground is the approach required by the international standard for the measurement of noise from wind turbine generators (IEC 61400–11). This paper presents data that illustrates the extent of the problem, reports on the trial of three different microphone mounting locations for measuring airblast from blasting and concludes that in windy conditions, microphones placed on the ground substantially avoid wind problems and do not reduce the measured SPL of the airblast.CITATION:Henley, K, 2015. Reducing the effect of wind on airblast measurement during blasting, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 485–492 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015