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By R Chinamatira

Several technical and economic factors have to be taken into consideration in developing an optimal mining method. This paper describes some of the important factors learnt during the evolution of the sublevel cave mining method at Trojan Nickel Mine, part of the Bindura Nickel Corporation (BNC) in Zimbabwe. Sublevel caving (SLC) has been successfully implemented at Trojan mine since its introduction in 1994. The method has evolved over the past six years into a system that has brought about improvements in efficiencies and productivity. Although the original design parameters used were sound and provided a solid foundation for the system, they needed to be optimised to get the best out of the mining method. Improvements and changes have been made in areas such as the drilling process, charging and blasting techniques, ring pattern design, development size and shape, and the draw control system. This has enabled the mine to develop an SLC operation that is efficient and innovative. Experience gained, together with the theory available has given us a much better understanding of the system. This knowledge will be used in the future to enhance the system further. Given the low grades of the BNC Mines, management recognises that only through technical excellence and efficient mining can the mines reduce mining costs and maintain profitability and competitiveness on the world market. In the Zimbabwe mining industry reaction to technological change, mechanisation and advancement have been relatively slow, due to isolation and economic constraints, compared to the rest of the world. Economic difficulties prevail, with high inflation levels, a poor exchange rate, lack of foreign currency and other associated problems. Despite these constraints, the bold steps taken have transformed Trojan mine into a more efficient and competitive operation, presenting itself as the leading mine in the BNC group. Appendices give data to illustrate the benefits obtained.

Jan 1, 2000

By H R. Phillips

Fresh air intake in an underground coal mine is of critical importance to the occupational health and safety of workers due to the dynamic, confined and dangerous nature of the mining environment. In most coal mines in South Africa, belt road is not separated from the fresh air intake to the sections. Intake air to coal production faces generally contains dust generated by conveyor belts, transfer points and travelling roads. Long roadways (up to a few kilometres in some of the existing mines) to the coal sections are involved in the ventilation circuits of individual sections. This leads to a progressive increase in the dust levels in the intake fresh air and thus high dust levels in the air delivered to the working sections downstream. In the process of reducing worker exposure to dust in the face area, attention to the monitoring of fresh intake air is generally given a low priority. This paper summarises the intake dust levels measured in selected South African underground coal mining sections over the past five years and its use as a parameter in assessing worker exposure to dust through a newly developed model called the Dust Exposure Level Index (DELI). Based on the measured data of the South African coal mines, the average section intake dust level was 0.78 mg/m3. Approximately 60 per cent of the samples collected for the study have exceeded the 0.5 mg/m3. The intake dust level measured at a longwall face was much higher than in the CM headings. The measured section intake dust levels furnish the South African coal mining industry with the latest depiction of the level of face area dust contamination due to the intake air. Further, this paper demonstrates the use of intake dust level as a parameter in estimating exposure levels of workers, as it clearly plays as a corner stone in effective control of exposure to face area respirable dust. It must be borne in mind that intake dust is a base level to the mine worker exposed to dust without carrying out any additional work in the section. If the intake air is seriously contaminated by airborne respirable dust; then the exposure of the workforce in the section will constantly be elevated by that background dust level.

Jan 1, 2005

By K T. Mandisodza, T J. Cartledge

The principal objective of Geotechnical Engineers supporting operating mines is to provide safe working conditions and ensure that pit designs are geotechnically optimised to site conditions and pre-defined stability requirements. Pit slope designs are delivered in advance of pit excavations. Making changes to these designs is usually slow to enact and involves a layered sign-off before implementation, leading to unwanted delays in their adoption and subsequently increased production pressures. When unexpected ground conditions are encountered during the mining process, or short-term mining schedule requirements demand it, changes to these designs may not be easily feasible in certain situations. It is when these scenarios arise that Geotechnical Engineers need to be proactive and consider unconventional options to deliver safe operating conditions while satisfying short-term requirements to the mine schedule. Essentially, the geotechnical short-term strategic designs double-pronged approach supports the mine schedule while providing safe conditions and minimising geotechnical risks for people and equipment. Common short-term strategic geotechnical designs include; slope buttressing, over-steepening cut slopes to increase reserve recovery through unplanned or emergency cutbacks, and accepting risk threat and operating under unstable slopes. When implementing strategic design options, the Geotechnical Engineer must consider the broader implications for such designs. They must think of the plan’s long-term effects on the mine schedule and pit wall stability. Initiating aggressive designs to recover additional reserves to satisfy a short-term scheduling demand could result in-pit wall instability or suboptimal pit layout. Before and during the implementation phase, the Geotechnical Engineer must communicate and engage with relevant stakeholders to ensure that the plan is executed accordingly and geotechnical risks are effectively managed. Proactiveness to ground response and implementation of risk management strategies will improve safety performance and optimise mining schedules.

Jun 22, 2022

This paper outlines the manner in which legislative control for tunnelling and allied operations has evolved, detailing Victorian experience. It examines the concept of mine managers as it relates to the industry and attemps to illustrate its benefits. The Victorian experience in relation to fatal and serious accidents is examined in detail, particularly in the allied art of trenching and examines the Krings system of trench lining support which is hoped will catalyse an increase of engineering expertise in this area. The paper concludes by demonstrating that safety awareness is not incompatible with production efficiency or economic viability.

Jan 1, 1981

By J Durbin

To effectively plan for closure, we must have an end-point in mind. To undertake meaningful rehabilitation, a post-mine land use (or uses) must be known. However, it is becoming more apparent that the end-point or “goal-posts” are shifting - and may continue to do so throughout the life of a mine. As well as being safe, stable and not causing environmental harm, post-mine land uses should always be sustainable, achievable within the given land capability, and they should involve stakeholders in their design and development.The majority of mines in Australia, and around the World, were historically expected to return disturbed land to either native ecosystem or agriculture/forestry practices. However, examples of highly successful final land uses suggest that today’s focus on closure includes not only minimising future liability and impact but also – and importantly – a move towards the creation of economic opportunity (Murphy and Heyes, 2016).CITATION:Durbin, J, 2018. Planning for (not so) final land use, in Proceedings Life-of-Mine 2018, pp 110–112 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By F J. van Zyl, C A. S Thomson

"Anglo American Thermal Coal conducted a high level study of all of its underground collieriesto determine if there were electrical power saving opportunities at the main fan stations.A systems approach to electrical power savings was used to identify potential savings in the various components of a primary ventilation system. Furthermore, only technological interventions were considered to obtain electrical power savings. From generic technological driven electrical power saving strategies four energy savings strategies were identifi ed, namely potential overall reduction in ventilation volume, improved underground air utilisation, optimisation of fan-set effi ciency and potential fan drift design optimisation. The study indicated the colliery (say Colliery D, Shaft A) that showed most potential in the four technology driven energy savings strategies. A detail study was undertaken at Colliery D, Shaft A to increase the confi dence level and the study confi rmed that up to 45 per cent of the main fan absorbed power can be saved (475 kW) with an estimated capital payback period of 18 months. The study clearly showed that an integrated approach to optimise the entire mine ventilation system has great potential for power saving, and that a clear, well -defi ned methodology will be applicable to similar underground collieries. This paper discusses the background to the study and the process followed to implement the energy savings initiative at Colliery D, Shaft A."

Jun 1, 2012

By Greenwood-Smith R, Ellis W. K

A bulk analyser based on the gamma-ray resonance scattering process can be used to give a rapid and accurate measure of the percentage by weight of copper or nickel averaged over a large mass of sample, typi- cally 20 kg. It is shown that for a bulk sample containing about 3 wt.% Cu, crushing to -25 mm is the only sample preparation requited for analysis to within an error of about 0.06 wt.% Cu (errors quoted are one standard deviation). A comparison of bulk analyser and con- ventional assays on the same bulk samples can be used to estimate the sample preparation errors in the conventional methods. The squared deviations between bulk analyser and conventional assays are approximated by the sum of variances in sample preparation, conventional analysis, and bulk sample analy- sis. The sample preparation error was esti- mated as 0.26 wt.% Cu for samples crushed to -2 mm before splitting, 0.08 wt.% Cu for samples crushed to -0.35 mm before splitting, and 0.04 wt.% Cu for the average of 15 grab samples from bulk samples which had been crushed to -2 mm. The average copper grade for each group of samples was about 1.7 wt.%. Results are presented which show that

Jan 1, 1976

By E Claridge

There are a number of major infrastructure tunnelling projects currently underway or proposed in New Zealand, including construction of new road and rail facilities and the refurbishment of existing road tunnels. These new projects have triggered a rethink of traditional practices in underground fire and life safety and local regulation.While there is a current surge in activity, tunnels have been a signifi cant part of New Zealand’s transport infrastructure for over a century. Despite this background, the new projects commonly face challenges that are symptoms of a national regulatory environment that has aspects that are inappropriate for underground environments. There are inconsistencies in local regional regulation and an absence of national guidance and standards relating to tunnel design. Historically, New Zealand has looked across the Tasman for guidance. Although recent overseas tunnel designs present learning opportunities, the adoption of international best practice and standards may not necessarily address local expectations or needs.This paper explores a number of specific matters affecting the design of road and rail tunnels in the New Zealand context, namely; the Building Regulations and associated local consenting processes and parties, and the responsibilities and needs of the New Zealand Fire Service.The discussion highlights the importance of a collaborative approach involving the designer, asset owner, regulators, emergency services, and other parties, and ensuring up-front clarity in design responsibility and ownership of residual risk.

Mar 8, 2011

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

By Hendrix J. L, Nelson J. H

A model based on non-steady state has been developed for dissolution and diffusion in porous ore particles. Results from the particular model have been incorporated, as a rate term, into a global, heap-scale model based on a plug flow reactor at unsteady state. The global model can be used to consider leaching by aqueous-phase reagents in equilibrium with a gas- phase component, such as oxygen gas, as well as strictly aqueous-phase reagents, such as cyanide. The flexibility of the model even allows predic- tion of the outcomes of using reagent sideflow injection in large heaps. Data from column leaching tests are compared to the model, and their relationship is discussed.

Jan 1, 1991

By B Murphy

Safescape Laddertube provides an improved system for emergency egress in ventilation shafts. The addition of Laddertube in a rise has very little impact on ventilation flow, studies have indicated that the difference in flow velocities are difficult to measure due to the minimal impact. Due to the size and open-ended nature of Laddertube, the air velocity inside and out of the Laddertube is mostly linear. Laddertube can be used either permanently or during an emergency as a secondary ventilation duct. One project involved a 385 m ladder installed in a surface return air raise that could be made to bypass the primary circuit and supply fresh air to a sea container fresh air base at the bottom of the raise. Laddertube has been designed to be installed to any feasible length and can be fitted with a climb assist system ensuring enhanced speed and reduced fatigue during ascent. The climb assist used in association with Laddertube is a Tractelift system which applies a weight relief of up to 36 kg off the climber’s body weight when using the ladder. This system has successfully been tested for ladders up to 600 m in length and is currently in use for a ladder of 185 m length. The use of refuge chambers in underground coalmines has long been a contentious issue due to the concern that while it may provide temporary shelter, the risk of being exposed to high heat or the inability for rescuers to access them due to fire or explosive atmosphere means that they may be effectively trapped. The additional application for coal environments includes Laddertube installed alongside a refuge chamber concealed behind a blast proof door ensuring a secondary means of emergency egress. In certain operations designs may allow for this chamber to be provided withpositive pressure fresh air.

Oct 12, 2022

Mineral sands are different to almost any other commodity; however, it shares similarities with other commodity types, such as the importance of quality constraints of iron ore and coal or the importance of physical properties of diamonds. The mineral sands industry consists of two principal product streams; titanium dioxide minerals û in the form of rutile, ilmenite and leucoxene, and zircon. The principal valuable heavy minerals (VHM) include ilmenite, leucoxene, rutile and zircon. Variations of other titanium minerals occur between the end members of ilmenite and rutile, including pseudo rutile and anatase. Most mineral sands deposits are found in unconsolidated fossil shorelines several hundreds of metres to tens of kilometres and occasionally hundreds of kilometres inland from the present coastline. Mineral sands orebodies essentially fall into two categories based on the mode of deposition: alluvial or aeolian. Alluvial deposits are further split into marine beach placers (or strandlines) and lacustrine heavy mineral (HM) accumulations. Exploration for mineral sands involves the positive identification of key criteria leading to the focus of exploratory surface sampling, augering and drilling. Assaying is primarily focused around determining the percentage of HM contained within a given sample. Other results of interest include clay fines, sand and oversize. Metallurgical/mineralogical assessment is often undertaken via laboratory scale bench tests that replicate the wet concentration and dry mill processing routes. The most critical component in resource assessment for mineral sands is about quantifying HM grade, then mineralogical assemblage and then quality of those mineral species. This will determine whether a mineral sand final product is marketable or not. Mining of mineral sands is conducted either wet or dry. Wet methods are generally preferred for large tonnage, unconsolidated and low clay orebodies. Where ground conditions are hard and orebodies are small, high grade and discontinuous, dry mining techniques are generally employed. Concentration of mineral sands from the primary ore is carried out in two sections; wet, utilising sizing and gravity differentiation between HM, VHM, clay and quartz, and dry, exploiting the magnetic, electrostatic and to a lesser extent specific gravity (SG) properties of the minerals of interest. Mineral sands exploration, mining and processing faces the same operating challenges as the rest of the resource sector. Added to this are the issues that are unique to mineral sands and to which the industry devotes considerable resources to developing solutions.

Jan 1, 2009

By B Robertson

Over the 40 years that the author has been engaged in the Australian underground coal mining industry, there has been a continuous improvement in safety performance as the sector has grown in size and productivity. The underground environment hosts many hazards with significant risk profiles that are kept in check by effective health and safety management systems that have evolved largely following major underground disasters. Observations are made on the changes observed for specific aspects of the underground coal sector, with particular reference to ventilation issues, and predications are made as to the needs of the future.CITATION:Robertson, B, 2013. Past achievements and future challenges in the underground coal sector, in Proceedings The Australian Mine Ventilation Conference , pp 27-32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By M Szwec, P Corbett, P Sheffield

Centennial Coal operates the Springvale and Angus Place longwall mining operations that extract coal beneath the Newnes Plateau in the Western Coalfields of New South Wales. Springvale and Angus Place mines have a history of difficult geotechnical conditions, where mining operations are conducted with a thick coal roof interbedded with numerous claystone units and relatively high levels of vertical and horizontal stress. The combination of a relatively high stress regime and weak laminated roof has led to numerous roof failures throughout the mine’s life.Following underground roadway development, the mine roadways can experience high levels of roof movement that can lead to roof falls. Two-point wire extensometers (known as ‘telltales’) are extensively used for roadway condition monitoring. Along with extensive other geological and geotechnical data, monitoring data is used to prepare geotechnical hazard plans that are then used in all areas of mine planning to allow for safe and efficient operation of the mine.This paper presents a case study of the use of a new software tool that allows time-scaled visualisation of monitoring data in the context of longwall and development face positions and installed strata support. It can be used in the identification of geotechnical risk factors and their interaction with the mining process to allow a more robust geotechnical hazard process. It interfaces directly with the widely used ExtoChart database software and can be presented with scale drawings of geological/geotechnical data to allow correlation of monitoring data with risk factors.CITATION:Corbett, P, Sheffield, P and Szwec, M, 2014. A new tool for extensometer data analysis and improved understanding of geotechnical risk factors, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 217–232 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

Digitally enhanced Landsat MSS images are being used'in delineating the structural and tectonic features in the Arabian Shield as part of a project funded by King Abdulaziz City for Science and Technology (KACST) of Saudi Arabia. The delineated features together with statistical modeling and structural analysis are to assist in an improved understanding of the evolution and mineralization of the Arabian Shield. Specific emphasis is to be given to relating the extracted linear features to the location of known mineral occurrences and areas of potential geologic hazards. A number of textural (spatial) and spectral enhancement techniques have been applied, to the MSS data covering selected areas, in selecting the most optimal enhancement product for visually delineating the structural geologic .features.

Jan 1, 1988

By D Lees, D Gilchrist

Sydney has hundreds of kilometres of sewer tunnels. Many of these are over 50 years old and some have been in service for more than 100 years. The tunnels are predominantly constructed in Hawkesbury Sandstone and many are unlined.Principles have been developed over many years for the safety factor required in designing and constructing new tunnels but these do not necessarily relate to the operation and maintenance of existing tunnels, and in particular those that do not necessarily require personnel access for anything other than regular inspections.Assessment of the stability of these established tunnels needs to take account of their size, their age, their function, and their method of construction, as well as the geology in which they are situated and any support measures which have been installed. More importantly a stability review needs to take account of the consequences of a collapse, with regard to the inspection process, carrying out of any required repairs and the long-term performance of the tunnel.This paper is based upon the authors’ experiences inspecting and reviewing more than 200 km of tunnel in the last ten years. It will show some of the procedures and methods adopted by Sydney Water, how these can be presented as an acceptable procedure in line with other safety standards, and how they might be adopted for other similar historic rock tunnels.CITATION:Gilchrist, D and Lees, D, 2014. The development of a procedure for the inspection of unlined rock service tunnels, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 543–552 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

Traditional in situ fan flow test methods under accepted standards require determinations to be made of both static pressures and total pressures during testing. This is to determine the resultant velocity pressures, which are vital in the accurate determination of the final fan airflow. These crucial velocity pressure (Vp) determinations are normally determined using simple manometric instrumentation such as an electronic manometer or an inclined liquid filled manometer. There is relatively little noise or fluctuation in the static pressure determinations and they can be quite easily and accurately recorded. There is almost always considerable fluctuation in the velocity pressure determinations though due to the highly turbulent and irregular velocity profile normally found in such in situ installations. This velocity turbulence means that the recording of such data is subject to random human error as the observer tries to average such fluctuations mentally during the observation period. Worse than this, and in the extreme, the recording of such velocity pressure data could actually easily be misreported if, for some reason, persons chose to do so.The author has devised a field method using highly accurate quartz crystal logging barometers to objectively record these velocity pressures. The method eliminates the ability to either mistakenly or intentionally misreport these crucial velocity pressures and is carried out in parallel with the recognised methodology, so result comparisons can be drawn. As such, a far greater level of confidence can be achieved in the final flow performance results than using the traditional more subjective method. Further to this it is difficult and almost impossible to refute the results using this ancillary substantiation method.The accurate determination of fan flows due to the impost of the carbon tax has taken on much more significance given the financial impacts in Australia at this time. The methodology detailed herein can be applied equally for both fan flow compliance testing and the verification of mine airflow data for greenhouse gas emission evaluations.The paper utilises the results of one 24-point pitot traverse to demonstrate the various findings. These include the very wide range of velocity pressures, which were logged at most of the measuring stations. It also illustrates how the method is utilised and compares the results derived from both this method and the more subjective traditional method along with the benefits of logging the velocity pressure results during the testing process.CITATION:Rowland, J A, 2013. Removing some subjectivity from traditional BS 848 and ISO 5802 in situ fan flow tests, in Proceedings The Australian Mine Ventilation Conference , pp 155-162 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By C J. Moran

All mines face water management challenges. Adopting leading practice water management strategies can help reduce both operational and strategic risks. While many of the water issues faced by underground mines are the same as other operations, underground mining presents some unique water management challenges. In this paper we review trends in underground mining, water use and associated water issues. We then compile a structured set of strategic and operational risks that are pertinent to underground operations. The causes, threats, opportunities and measures for controlling or mitigating the risks are summarised. The risk compilation could provide an addendum for underground operations to the Australian governments leading practice water management handbook.

Mar 21, 2011

By S Mitchell

Jetcrete Australia Pty Ltd, shotcrete contractor took the initiative in 2008 to discontinue the use of ‘road registerable’ concrete trucks for all underground works in Australia and internationally.The rationale for this decision was basic, safety. Historically these vehicles have been and still are involved in far too many accidents; this obvious trend needs to be addressed by engineering out the root cause of the problem which in this case is suitability for purpose.Road registerable concrete trucks have been widely used for the delivery of concrete in Australian mines for many years prior to and after the inception of wet shotcrete as ‘in cycle’ ground support in underground excavations around 1992. With this inception came a wide interest in the shotcrete process and an influx of new shotcrete contractors, all using road registerable concrete trucks to deliver the large volumes of Shotcrete required for these services and in turn largely increasing the use of these vehicles underground. The road registerable concrete trucks were difficult to control and each trip underground required the operators to maintain good management of the inherent risks. We virtually had no reasonable alternative for the industry and could only encourage the operators to drive with soft controls such as, reducing overall speed to a maximum of 15 km per hour when declining, regardless of the road conditions, coming to a complete halt prior to turning into any sharp corners, remaining in the same gear both inclining and declining.

Mar 21, 2011

By A Noack

Today underground infrastructures, like tunnels and especially wide spread underground mines, are often equipped with ethernet based communication systems. These networks are used for the unified communication of data, voice and video. As these networks stretch along the major tunnels and in increasing scale also into the production areas, a high degree of coverage can be reached. For wireless coverage, standard IEEE 802.11 WLAN access points are being used. In order to provide a maximum availability and reliability, the active components are equipped with battery backup power supplies and the network infrastructure is set up in a redundant way using ring or meshed topologies. This provides a much higher availability compared to traditional phone systems or dedicated data links using a conventional star topology.Distributed computing intelligence that is installed on active network nodes throughout the whole network, additionally supported by a central server system, creates the basis for new mine safety functions introduced in this paper for both coal and non-coal mining. These new safety functions cover the detection of potential emergencies, using the status of the network as a æsensorÆ, as well as dynamically guiding people to safe exits or rescue shelters in case of an emergency. Furthermore, these functions are of important benefit for improving the efficiency of search and rescue operations following a major incident or accident underground.

Sep 26, 2011