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The revival of the mining industry at Captain's Flat after a long period of years of inactivity has attracted attention to the importance of the ore-deposits of that field as potential sources of supply of lead and zinc. Mindful of the necessity for taking stock of the State's mineral resources, the Department of Mines of New South Wales as part of its programme of geological investigation, carried out a survey of the oredeposits and associated country rocks during 1938 and 1940.Surface geology was mapped in detail and all available exposures were examined and logged. Unfortunately, and this condition militates against the formulation of conclusions because of insufficiem.t data, some of the older workings, notably in Keating's Section, were inaccessible and the logging of levels and stopes is by no means as complete as could be desired. However, with the progress of development and exploration, further information of geological value will come to hand for incorporation in supplementary reports. It may be expected that, under such circumstances, modification of certain statements herein expressed may be necessary but it is not anticipated that any vital alteration will be occasioned.Within the State of, New South Wales, Captain's Flat ranks second to Broken Hill as a pqtem.tial producer of lead and zinc. In addition, large quantities of iron pyrites are available for the manufacture of sulphuric acid which finds application in the superphosphate industry.The mines are now controlled by an operating company known as Lake George Mines, Ltd., incorporated in New South Wales, the parent organisation being the Lake George Mining Gorporation Ltd., registered in London.Over £600,000 has been spent by the Company in exploration, mine development, surface plant, housing and water 'conservation, while the State' Government constructed a branch railway from Bungendore at a cost of £200,000. The various activities consequent upon these development and construction programmes and the prospect of employment in the industry has led to a rapid increase in the population of the township.The State, generally, has benefited to the extent of a substantial contribution to the relief of the unemployment problem, and it is hoped that reasonable permanency will be assured to some hundreds of workers for many years.

Jan 1, 1941

In North-West Nelson the Riwaka Complex, a linear basic intrusive complex, is exposed for approximately 45 kilometres. Some 500 kilometres south, across the Alpine Fault, a linear zone of similar but less well known basic intrusives that may be correlatives of the Riwaka Complex is exposed discontinuously for about 80 kilometres. The Complex was emplaced at several centers along a major tensional fracture zone that developed in upper Carboniferous to Lower Permian time. This fracture zone probably formed in response to the development of a west dipping subduction zone that gave rise to the Permian volcanic arcs in east Nelson and western Southland. The Riwaka Complex contains three rock suites. The Fractionation Suite, characterized by cyclic mineral layering and small scale cumulus banding is the largest and is divided into the Ultramafic, Hornblende and Plagioclase Series, each of which is subdivided into several units. The Cumulus Gabbros represent a restricted but important suite of unusual composition, while the third suite is the late phase Diorite Suite.

Jan 1, 1980

By D L. Reid, G Nwaila, J Petersen, J-P Franzidis, Y Ghorbani, M Becker, F C. de Beer, L C. Bam

Traditional methods of gold extraction have involved comminution and processing via cyanide leaching, all of which are associated with energy, cost and environmental implications. Subsequently, numerous opportunities for improvement and optimisation strategies in gold mining and processing have been explored, including heap leaching, which has significantly lowered comminution costs. This paper explores the effect of the more energy efficient high-pressure grinding rolls (HPGR) on the comminution behaviour (especially on the crack density) and cyanide leaching performance of laboratory reactors study on run-of-mine gold ore comprising the Ventersdorp Contact Reef (VCR) and the Elsburg Reefs (ER), sourced from Carletonville in the Witwatersrand Basin in South Africa. The ore was comminuted using HPGR at three different pressure settings (120, 90 and 60 bar). Large (-16/+11.2 mm) and small (-5.6/+4 mm) particles of the HPGR product where then mineralogically characterised using optical microscopy, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and X-ray computer tomography (CT) before cyanidation. The results of the leach experiments indicated a correlation between gold extraction, particle size and crack density. Mineralogical characterisation of the ore indicates that the Fe-sulfides present in the VCR are likely to be more reactive than those in the ER, thus having a more favourable influence on gold cyanidation. Overall, the results show promise for the heap leaching of Witwatersrand gold ores prepared using HPGR and demonstrate the value of a multi-disciplinary geometallurgical approach.CITATION:Nwaila, G, Becker, M, Ghorbani, Y, Petersen, J, Reid, D L, Bam, L C, de Beer, F C and Franzidis, J-P, 2013. Morro do Ouro geological model with a metallurgical view, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 75-84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

By Nemcik JA, Gale W. J

The magnitude and orientation of the in situ stressfield has been determined as a key factor in controlling the stability of openings for both coal mine development and extraction. Monitoring of roadway and pillar behaviour in conjunction with numerical analysis has identified specific stress control measures that have been successfully applied to improve productivity in underground coal mining operations. The influence of the major horizontal stressfield on the stability of openings has been identified at a wide range of sites including mines in Australia, Britain, the USA, New Zealand and Japan. Stress mapping, stress measurement and stress monitoring techniques have been applied to define the in situ stress regime and, together with the correlation of measurements of rock deformation and rock reinforcement behaviour, has enabled appropriate stress control measures to be developed. Stress control measures for development headings have required the selection of roadway orientation, roadway sequencing, reinforcement density and pillar size. The monitoring of behaviour at a range of trial sites has confirmed significant improvements in development stability. Stress control measures for longwall extraction have required rational selection of longwall orientation and extraction direction. Where a mine layout design incorporating the optimum longwall layout design has not been possible, the use of sacrificial roadways has been successfully applied to protect key roadways from stress concentration effects. Comprehensive in situ

Jan 1, 1992

By J Elder

Magnetic separation equipment has long been used to upgrade and beneficiate a wide variety of minerals and materials. Over the years, significant advances in both wet and dry magnetic separators have improved their operability and separation performances, broadening their use.But no one answer exists to the question: what is the right type of magnetic separator? For many minerals, including ilmenite, both process routes may be viable. There are technical, production, as well as economic reasons for choosing wet versus dry. However, recent developments illustrate that a new generation of wet magnetic separators is approaching performance once seen only in dry magnetic separation. With quality and production performance becoming similar, the choice between wet and dry magnetic separation is not as cut and dry as it once was.

Oct 5, 2011

By Sorokin M. L, Komkov A. A

Flash smelting of nickel sulphide concentrate has been practiced at WMC's Kalgoorlie Nickel Smelter for 20 years. The mineralogy of the concentrate from the original mines was particularly suited to this process. However, taking a strategic view, potential new processing routes should be fully evaluated as possible replacements for the current technology. The Vanyukov process has been under development in Russia for the past 40 years and has been successfully applied on a large scale to the smelting of copper concentrates, at two locations - Norilsk and Balkhash. The potential for the application of the Vanyukov process to the smelting of nickel concentrates offers a number of processing advantages, including smaller reactor and decreased dependence on fuel oil. This paper reports on preliminary investigations into the application of the Vanyukov process to the smelting of nickel concentrates. At this stage the investigations are limited to semi-quantitative comparisons and modelling studies.

Jan 1, 1992

By H Beucher

The uranium grade in roll front deposits is the result of successive processes that can be summarised in two steps. First a sedimentary phase, which gives the deposit support, then an oxidation-reduction phenomenon, which leads to the uranium deposit itself. In order to simulate such a deposit, it is important to mimic these different phases. The final aim of such a study is to localise the uranium itself and to reproduce the internal heterogeneity of the orebody in order to simulate the recovery process. The idea in this paper is not to reproduce a genetic approach but to consider the final image of the deposit. Three approaches are proposed. The first one consists of simulating the facies of the sedimentary deposit. The second approach reproduces the distribution of facies resulting from oxidation phenomenon (reduced or oxidised facies). The third approach consists of simulating the mineralisation at the interface of reduced and oxidised areas using the definition of a new data set determined by the grade values. At the end of each approach, the uranium grade could be simulated facies by facies according to the corresponding distribution characteristics. The plurigaussian method dedicated to random set simulations is well-suited for the facies simulations of deposits resulting from several sedimentary processes whether correlated or not. In this paper, the benefit of this method is demonstrated in an actual case study.

Jan 1, 2006

By M L. Muller, A R. O’Donnell

The Mount Isa Mines (MIM) Copper Concentrator has an extensive history of reagent trials, with different reagents coming in and out of favour over the years. The research and use of carbon depressants is particularly prevalent, as carbonaceous pyrite is a major source of concentrate dilution. Years of research led to the use of naphthalene sulphonate due to its excellent carbon depression properties. However, due to rising reagent costs carbon depression ceased in the late 1990s. This led to the loss of knowledge about the use and value of naphthalene sulphonate. Cyanide is used at the Copper Concentrator for the sole purpose of pyrite depression and over the years multiple projects have been devoted to finding alternatives to it. In 2012 the neighbouring MIM Lead-Zinc Concentrator replaced cyanide with naphthalene sulphonate which resulted in cost savings and the elimination of a hazardous reagent. In 2013, plant trials were conducted at the Copper Concentrator in hopes to replicate the outcomes obtained at the Lead-Zinc Concentrator. The results of the trials conducted at the Copper Concentrator showed that naphthalene sulphonate could not replace cyanide and this work was set aside to pursue more promising projects. Further research conducted in 2014 found that mineralogy and a better understanding of the depressing mechanism of naphthalene sulphonate held the key to improved pyrite depression at the Copper Concentrator. The findings showed that Mount Isa copper ore contains two forms of pyrite; euhedral pyrite (cubic pyrite) and framboidal pyrite (carbon rimmed spheres of pyrite), both of which require different reagents to sufficiently depress them. Naphthalene sulphonate was found to be an excellent carbon depressant, suitable for depressing graphite and framboidal pyrite, whilst cyanide specifically targets euhedral pyrite.In 2015 laboratory test work was conducted to examine the use of naphthalene sulphonate in conjunction with cyanide to selectively target both forms of pyrite. This work led to a full plant trial, the results of which showed a significant increase in plant performance, with higher copper concentrate grades and recoveries being achieved. This paper aims to focus on the benefits and importance of understanding past work and linking a detailed knowledge of feed mineralogy to reagent selection for improved plant outcomes.CITATION:O’Donnell, A R and Muller, M L, 2018. Selectively targeting hydrophobic gangue minerals at the Mount Isa Mines Copper Concentrator, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 413–421 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By D Cliff, K Bailey

Traditionally occupational health and safety (OH&S) has been managed for the direct benefits of reducing injury and illness to workers on mine sites. In the current skill shortage climate it is important to recognise the value that OH&S management can have in assisting mines in minimising their exposure to this issue. In times of skills shortage turnover is high as mines poach personnel from each other. This leads to loss of corporate knowledge and loss in productivity through the need to train new personnel in mine-specific operating procedures. In addition absenteeism can significantly disrupt production as there may be no ready replacements available for key jobs. Pressure will be placed upon workers to remain at work even though they are not completely fit for work, leading to presenteeism and consequently loss in productivity. In addition to the threats to routine operation, the loss of management and professional staff can significantly increase catastrophic risk through loss of experience and corporate knowledge. There is increased pressure to focus on events that occur regularly in the here and the now and underestimate the rare, or unlikely, events.The theme of this paper is that by properly addressing OH&S management at mine sites, companies can minimise their exposure to these problems. Put simplistically, a safe and healthy mine is a sustainable and productive mine. Case studies and relevant literature will be used to support this premise.CITATION:Cliff, D and Bailey, K, 2012. Health, safety and sustainability, in Proceedings International Mine Management 2012, pp 53-58 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By Baker G

Chromite was recorded among the rare minerals in the natural beach sand concentrates on the coast of Northern New South Wales by Whitworth(l) in 1931, and the commercial production of zircon and rutile from these beach sands has yielded concentrates of ilmenite with small amounts of chromium. The chromite is a detrimental impurity in the utilisation of the ilmenite, and the difficulties that attend the separation of the small amount of chromite from the ilmunite have raised suggestions from time to time that chromite occurs with ilmenite in composite grains. The absence of such composite grains and the nature of the chromite grains has been indicated by the following mineragraphic examination of magnetic concentrates containing chromite which were prepared by the C.S.I.R. Ore Dressing Laboratory, Melbourne University, from ilmenite concentrates from beach sands at Norrie's Head, County Rous, New South Wales and Stradbroke Island, Queensland.The magnetic concentrates from each locality are divided into five fractions, and the No. 1 concentrate is the most highly magnetic and the tailing the least magnetic. Chromium assays as determined by the Ore Dressing Laboratory are as follows:-

Jan 1, 1948

By S A. Ravishankar

In heavy minerals separation, the titanium and iron oxide phases are separated from silicates in the coarser particle size range (80 - 150 mm) using magnetic and electrostatic separators. With the ongoing challenge of heavy mineral ore deposits getting increasingly finer in particle size, conventional separation equipment suffers from the ability to process this material at the same throughput rate as coarser particles. A variety of magnetic separation technologies were developed to perform at a much finer particle size range, down to 2 mm in the clay industries mainly to remove titaniferrous oxide particles. Complementing the developments made on the physical aspects of magnetic separation, Cytec Industries has recently developed a ‘bolt-on’ chemical enhancement technology for magnetic separation (CEMS). This is to enable separation of finer particles, and weakly paramagnetic titanium phases from diamagnetic silicates that are not amenable to magnetic separation. This paper will provide an outline of the technology, illustrate its ability to process a wide variety of ores, and also discuss plant limitations. The major advantages of chemical enhancement technology to magnetic separation includes: simple dosing equipment extension to existing magnetic separation technology; ability to produce product of comparable quality with improved cost effectiveness, when compared to incumbent flotation; removal of impurity minerals over wider size range; enhanced removal of non-magnetic impurities; and improving the process robustness. Furthermore, chemical enhancement technology for magnetic separation has also emerged as a platform for removing impurities at lower levels in other mineral systems as well.

Oct 5, 2011

FOR some time it has been recognised by the Metallurgical Staff that the presence of pyrite in the ore was adversely affecting the grades of the flotation concentrates.Following experimental work, it was decided to change over from the acid circuit in the mill to an alkaline circuit. The following description sets out the procedure adopted, -and the results obtained when such change-over was made.The Zinc Corporation ore consists mainly of galena, marmatite, calcite, and quartz, with smaller quantities of pyrite, fluorspar, and rhodonite.A clean specimen of marmatite picked from the ore assayed 53.4% zinc, and 10% iron, with no lead or insoluble. However, as zinc concentrates have been, at times, produced in the plant assaying over 53% zinc, and with only 8.7% iron, apparently the picked specimen of marmatite did not represent an average composition.The average would probltbly be between 8 and 9% of iron, and from 53.5 to 54.5% of zinc. It is obvious, therefore, that from this ore it is not possible to produce zinc concentrate of a higher grade than this average figure.In the Colorado School of Mines Quarterly for April, 1928, Vol. 23, No. 2, on page 47, we find the following statement:As the zinc in the ore exists as marmatite, which contains approximately 54.5% zinc and 10% iron, 49% zinc in the concentrate may be considered high.This statement refers to the ore treated in the Sullivan concentrator, owned by the Consolidated Mining and Smelting Company of Canada Limited.

Jan 1, 1930

Anodic stripping voltammetry is an analytical technique which has established some popularity for trace analysis of metals because of its sensitivity, selectivity and capability for simultaneous analysis of some elements. The technique can be readily adapted for field use because of its relative simplicity and low power requirements. This paper describes a relatively new instrument, the Portable Digital Voltammeter, developed by CSIRO, which utilises the glassy carbon electrode in a novel cell design and provides parts per billion (ug/L) sensitivity in an instrument which can be field operated. Ten elements, Zn, Cd, Tl, Pb, Cu, Sb, Bi, Hg, As and Au can be routinely analysed. Many of these elements are of interest to the mining industry, and to exploration geochemistry in particular. Case histories where the instrument has been successfully employed for stream and stream sediment analysis of Cu and Pb, for soil surveys of Cu and Au, and for Au in stream sediments and drill chips indicate there are advantages in having on-site data, during Exploration.

Jan 1, 1987

By H von Blottnitz, J L. Broadhurst

Eco-efficiency has been proposed by the World Business Council on Sustainable Development as an environmental performance indicator framework that contributes to sustainability by assisting corporate decision makers improve the environmental performance of their operations and processes, while also extracting additional economic value. Given that the recent engagement of the minerals industry with sustainability has highlighted the need for requisite tools and methodologies, it is therefore of interest to assess whether eco-efficiency indicators can drive sustainability performance improvement during process design within the minerals industry. Previous work indicates that the choice of sustainability performance indicators to be used for decision making needs to be governed by the decision context; ie the performance indicators need to be fit-for-purpose. Here, the strengths and weaknesses of eco-efficiency indicators are analysed using case studies. First, a more rigorous definition of eco-efficiency indicators for the minerals industry is proposed based on indicators currently offered in the literature. Two case studies are then selected to reflect typical decision situations encountered within minerals process design. For each case study, eco-efficiency indicators are computed and are compared to more traditional graphical representations of the economic and environmental performance of process design alternatives considered. The sensitivity of these indicators to various process design parameters is also investigated. Results confirm that the meaningful application of eco-efficiency indicators is strongly dependent on the decision context in which the process data is generated. Results also show that eco-efficiency indicators can be related to technical process design parameters to allow for richer communication of performance information for various decision trade-offs; however, in some cases, graphical approaches that provide more insights into the environmental-financial trade-offs should be preferred. The research thus contributes to guiding the selection of the appropriate tools for more environmentally sustainable design of minerals beneficiation processes.

Jan 1, 2009

By Higuchi K, Sekimoto Y

In this report,the results of the large diameter drilling tests in coal seams assisted with water jet are described. The stress relief in coal seams by this new method is as effective as by the conventional method and the penetration speed by this method is 1.5 times as fast as by the other method. 1 Introduction The average mining depth of Japanese coal mines has already attained about 700m from the surface. Almost all coal mines are suffered from occurrence of coal and gas outbursts. To prevent outbursts, some countermeasures are taken generally. In particular, large diameter stress relief borings have been carried out quite often at Akabira coal mine located in the northern part of the Ishikari coal field in Hokkaido,JAPAN. These borings have had successful results but the drilling work of such large diameter

Jan 1, 1987

By N Schofield

For the sampling of particulate materials in mineral exploration and mining, the fundamental sampling error (FSE) introduced by Gy is a measure of the constitutional heterogeneity of the sample lot and is expressed as the relative standard deviation of subsample grades of a particular mass. The FSE is presently regarded as an important indicator of quality for samples used in resource estimation. Constitutional heterogeneity describes an ideal state of heterogeneity with respect to all constituents of the lot such that the fundamental error among subsamples of a particular mass is minimised.In this paper, the term ‘sampling precision’ used in relation to mineral resource sampling usually refers to a statistic based on the assay results drawn from pairs of separate subsample splits of multiple sample lots. The pairs of splits are extracted after the lots have been prepared by crushing and pulverising to meet specified criteria of grain size and subsample mass. There is presently no generally accepted method of calculating the ‘sampling precision’ from such paired data but some form of the relative standard deviation that is consistent with definition of the FSE is preferred here. The work of Thompson and Howarth in the 1970s on geochemical analytical precision, which has been subjected to extensive examination and criticism by Stanley and Lawie (2007), and that of Francois-Bongarçon since the 1990s forms the background to the discussion in the paper.A significant aspect of the application of Gy’s sampling theory to sampling in gold deposits is the requirement that the fundamental error be maintained at less than ±20 per cent. The most important reason for this is to ensure that the effects of other sampling errors such as the grouping and segregation, and increment delimitation which can cause local and global biases in sampling are kept as small as possible. This paper is focused mainly on the quality of sampling in gold deposits and looks at an alternative to the use of a constant sampling precision applied to a collection of lots with varying average grade. A theoretical model for the FSE based on duplicate sampling is presented and the simulated results of the model are compared to practical outcomes of real duplicate pairs drawn from multiple sample lots. The goal of the work is to present a more informative analysis of duplicate sample data from multiple lots which may allow a more informed view of the potential for bias generating errors during sample preparation and processing.

Aug 22, 2011

By T N. Little

The aim of any rock breaking activity is to achieve success by developing designs that are blasting objective-specific and geology-specific, and then implementing such designs. This paper targets mining geologists with the aim of extending their knowledge of the rock fragmentation processes and providing insights to the significant relationships between geology and blasting. There are two main relationships, and if mining geologists appreciate both these relationships, then they can play a key role in optimising production. The business risk continuum is introduced to support this understanding. The first relationship is between geology and potential blasting hazards, and the operational complexity required to manage those risks. The risks associated with eight different ground types are discussed in terms of ground conditions, hazards and controls. These types are: reactive ground, hot ground, geothermal ground, fibrous ground, cavernous ground, combustible ground, pyritic ground and conductive ground.The second relationship is between the bench geology and blasting results. The blasting results discussed include: muckpile characteristics, remaining rock faces and blasting emissions. In this regard, some detailed insights and graphical examples are given for the influence of geology on blasting emissions, in particular, vibration, airblast and flyrock.A detailed description of the geological materials themselves can convey much useful information for blasting operators provided they are able to utilise this knowledge. Geologists are ideally suited to provide this description more effectively if they are familiar with the blasting process and the rock mass properties that influence blasting hazards and blasting results. It is also important to have clear statements of blasting objectives and associated operational targets, and this will maximise the likelihood of achieving the desired outcomes. The main aim of the paper is to highlight that geology is currently not fully utilised in the blasting process. In this regard, geologists are often not entirely aware of the blasting process and how they can contribute. The two significant relationships discussed above are integral parts of this process, and thus they are discussed as separate issues in the main body of this investigation.

Aug 22, 2011

By J Vann

The philosophical context of many activities in mine geology can be an important lever in adding value to operations. For mine geologists (including resource and grade control geologists) we argue that the tasks of problem formulation, observation and data collection, interpretation and modelling invoke various philosophical considerations whether the practitioner is aware of them or not.Constructing testable models to explain reality is the definitive aspect of any activity claiming to be ‘scientific’. A primary goal of mining geology is to build models that accurately predict reality to an acceptable degree and these include litho-structural, stratigraphic, grade control, resource or reconciliation models. What’s more, in mine geology we are often able collect additional drill samples or access new underground openings, for example, that can provide relatively rapid feedback on how predictive, and therefore useful, our models are. In this paper, we describe the key philosophical frameworks proposed for conducting scientific investigations, including falsification, the method of multiple working hypotheses and structural concepts of scientific theory. The strengths and weaknesses of these approaches are discussed and an attempt is made to relate them to activities undertaken by mine geologists. Common perceptions of what constitutes the scientific method have been dominated by how scientists do experimental physics and chemistry in particular. There are very important differences in the types of problem confronted in these experimental sciences compared to the ‘historical sciences’, such as geology, where the processes studied are unique and only evidential traces of past events are available. The philosophical implications of attempting to validate numerical geological models, such as resource estimates are also briefly considered.Some practical conclusions are drawn about how mine geology activities can be better implemented if practitioners are cognisant of the importance of philosophical considerations when attempting to gain new knowledge through a scientific investigation. We believe that the implications for creating additional value to a project or operation can be very significant when geology is applied by a practitioner with an understanding of the philosophical basis of the activities we think of as constituting a scientific investigation.Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful? (Box and Draper, 1987, 74 p).The demand that theories be highly falsifiable has the attractive consequence that theories should be clearly stated and precise. If a theory is so vaguely stated that it is not exactly clear what it is claiming, then when tested by observation or experiment it can always be interpreted so as to be consistent with the results of the test. (Chalmers, 1999, 67 p).

Aug 22, 2011

By Upfold RW, Nguyen VU

The extraction and utilisation of metals and materials is the basis of modern civilisation, and will remain so for many decades, Traditional metals are facing some challenges and research is needed in specific areas, to improve metal extraction processes, to develop processes for newer metals and minerals, and to develop new applications, The shortage of metallurgists now becoming apparent in Australia is a further significant problem that needs urgent attention, and much more publicity is required for the Mineral Industry, as well as for the utilisation Industries,

Jan 1, 1986

By P Craig, M Holden, C Zhang, D Foster, J Oh, S Saydam, J Liu, H L. Ramandi, S Akdag

High stress in rock masses can cause significant instability problems such as squeezing deformation in soft rock and rock bursts in hard rock. The support system applied in burst-prone areas in high-stress conditions is required to be able to carry high load and accommodate large deformation of the rock mass without experiencing any serious damage. Yielding support systems are promising to provide support for both squeezing and burst-prone rock mass encountered in mining or tunnelling at depth. They are ideally strong and stiff initially and then ductile after yielding (Potvin and Hadjigeorgiou, 2020). With respect to support design, a ground support system has to create a safe working environment under both static and dynamic loading conditions by providing the functions of reinforcing, retaining, holding and connecting elements (Cai and Kasier, 2018). Rigid rock bolts and cable bolts perform reinforcing and holding functions of a ground support system. In highly fractured ground or with large excavation spans (eg at roadway intersections or in caverns), unstable ground depth can exceed the length of typical rigid rock bolts (ie greater than ~3.0 m). In such cases, flexible cable bolts are needed to tie the reinforced and retained rock mass back to deeper and more stable rock. The flexibility of cable bolts allows anchor lengths greater than the tunnel opening that would otherwise restrict rigid bolts. Cable bolts also offer higher strength to weight ratio, with tensile strengths 2–3 times that of standard rebar bolts. This high strength comes at the cost of lower strain tolerance, typically around 5–7 per cent at break. Despite the lower strain tolerance, cable bolts are often used as dynamic support in demanding burst-prone ground conditions. The lower strain tolerance is compensated by allowing sufficient free length for stretching or incorporating a yielding device. There are a number of dynamic cable bolts available on the market and a number of testing campaigns have been undertaken to quantify the dynamic performance of these cable bolts. This paper reviews the existing range of dynamic cable bolts and discusses the potential areas for improvement and further research.

Nov 29, 2022