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By G B. Smith, G M. Marshall, A Querzoli

The South Australian mining regulatory framework has adopted a performance based approach to the management of risk. This approach has been in place in South Australia for more than 10 years and is increasingly being implemented in mining jurisdictions in Australia and around the world. Performance based regulation focuses on setting appropriate environmental outcomes to be achieved based on an assessment of the potential impacts associated with the development, operation and closure of mining projects. Measurable compliance criteria, including completion criteria, are set to demonstrate achievement of the outcomes. It is the responsibility of the proponent to propose designs and strategies that will achieve the regulated environmental outcomes and to demonstrate the implementation of their designs and strategies will achieve the outcomes into the future. Tailings Storage Facilities (TSFs) are significant elements of many major mines and each is unique with site specific factors such a materials to be stored, design, size, location, climate, sensitive receptors, operating history of the facility (i.e. changes to design), site culture and company capability amongst a range of other factors. Consequently a fit-for purpose approach is a key principle of best practice regulation of tailings management as it takes the site specific factors into account in setting appropriate outcomes for mitigating the identified impacts associated with a proposed development. Achievement of those outcomes through fit-for purpose, well designed management strategies would ensure safe, stable and economic storage of tailings in a manner that complies with all legislative requirements and presents negligible public health and safety risks. Tailings storage must also have acceptably low social and environmental impacts, both on and off site, during operation and indefinitely post closure. Achievement of environmental outcomes during operations and at mine completion can then be demonstrated to the regulator and community through public reporting of compliance with measurement criteria which establish the appropriate level of impact for each individual operation. A number of new mining proposals including tailings storage facilities (TSF) have recently been assessed and approved in South Australia. The location, size, design, sensitive receptors, public interest and therefore risk profiles of these TSF’s have varied substantially between these new mining proposals. These considerations were reflected in the assessment of the TSFs and the resulting mining lease conditions of approval including the environmental outcomes to be achieved over the life of the facilities. This paper and the accompanying presentation will provide case studies of recently approved TSFs within South Australia and the regulatory framework for each case.CITATION:Smith, G B, Querzoli, A and Marshall, G M, 2018. Tailings regulation – a South Australian perspective, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 166–177 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By J T. Sharp, M A. Styler, D McGowan, P W. Mayne

Static liquefaction is a geotechnical hazard in mine tailings facilities. Soils that are contractive in shear are susceptible to static liquefaction. Tailings facilities are dynamic structures, typically growing in height each year. Dilative tailings may become contractive under increased effective stress. In this paper we show that Cone Penetration Test (CPT) data can be used to estimate the future state of in-place tailings under changes in effective stress. Susceptibility to static liquefaction is typically evaluated with the CPT by using a clean-sand equivalent normalized cone tip resistance (Qtn,cs) or by estimating the state parameter (?). An alternative approach is to evaluate the soil-state using the yield-stress-ratio (YSR = ?’y/?’v0). If the YSR equals one it is on the normal consolidation line and the soil-state is contractive. YSR values greater than three are typically dense of the critical state line (CSL) and the soil-state is dilative. In this paper we review how to calculate Qtn,cs, ?, and ?’y; and how the YSR can be used to screen for contractive soil behaviour. Unlike Qtn,cs and ?, it is very simple to estimate how the YSR will change due to an increase in overburden stress. This YSR approach was evaluated at three locations that saw increases in overburden of 10 m, 20 m, and 25 m. We show that the ?’y calculations are consistent and the increase in effective stress moves the soil state towards looser soil states. CITATION:Styler, M A, Mayne, P W, McGowan, D and Sharp, J T, 2018. Predicting changes in static liquefaction susceptibility using cone penetration test results, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 317–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By C A. Cooper, G A. Suter

The sizing of a starter dam for a Tailings Storage Facility (TSF) involves balancing many competing demands. It should cost as little as possible, be high enough to store tailings until the first raise can be constructed, it must be able to contain water safely, and it must be designed in such a way that the long-term integrity of the higher raises are not compromised, among other things. In addition to these demands there is the complication of the behaviour of the process plant, and the tailings during commissioning. Variations in slurry density, excess water in the TSF, initial settled density of the tailings, reliability issues, and beach slopes above and below water can all impact the way the tailings beaches are developed and ultimately impact the ability of the starter dyke to contain the required volume of tailings and water.The conventional approach to the design of a TSF starter dyke is to begin looking at the elevation required for a set of deterministic design parameters, find ways to reduce the size or volume of it as much as possible to reduce cost, and then possibly look at the sensitivity of some of the input parameters. This paper discusses a stochastic modelling approach for starter dykes that allows a wide range of design inputs to be simulated quickly, with an envelope of possible results produced. The sensitivity to different parameters can also be examined to understand which design inputs have the biggest impact on the required dyke sizing. By integrating the 3D TSF modelling tool Muk3D with GoldSim, it will be demonstrated how a wide range of scenarios can be evaluated and how that information can be used to make better decisions about the selection of design options.CITATION:Cooper, C A and Suter, G A, 2018. Starter dyke optimisation with Muk3D and GoldSim, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 466–475 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By J Li, H Hooi, D Payne

Caval Ridge Mine (CVM) is one of the newly established open-cut coal mines of BHP in Queensland, where no tailings dam is planned to be built in order to minimise environmental impacts from mining activities. The waste streams from the Coal Handling and Processing Plant, including fine tailings dewatered by belt filter presses, coarse rejects, and mixed plant rejects, are co-disposed within waste dumps built with pre-strip and dragline spoils. Due to high rejects output (35 – 60% of feed) and low spoil to reject ratio (< 5) the large quantities of rejects bring significant geotechnical and operational challenges to CVM, which are exacerbated by increasing annual production rates and additional rejects from washing coal from an adjacent mine. Further in-house geotechnical review commenced in mid-2014 based on the initial geotechnical studies during the project stage of CVM between 2011 and 2013. The outcomes have enabled rejects disposal at CVM by constructing large belt filtered tailings cells, coarse rejects only dumps, and co-disposal of the mixed plant rejects at dump tip-heads. This paper presents the rejects disposal strategies at CVM from both technical and operational aspects. It also discusses future projects for belt filtered tailings moisture reduction including assessment of tailings clay mineralogy, as well as mixed plant reject co-disposal verification and optimisation.CITATION:Li, J, Payne, D and Hooi, H, 2018. Plant rejects disposal strategies applied at Caval Ridge open cut coal mine, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 50–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By M Rafty, C Lane

Managing water is a key aspect of mining, whether a site is in water surplus or water deficit. Water in tailings storage facilities (TSFs) needs to be managed carefully to maximise the density of the solids, maximise the re-use of available water and to minimise the risk of water overtopping the spillway in the event of heavy rainfall. Developing a water balance models is a standard method for monitoring the major flows of water around a site. However, models created by specialist consultants are often overly complex and are not suited to being used by process plant personnel after they have been handed over to the mine operator. Models typically offer information on water management at the time that they are created, but then ‘sit on the shelf’ and offer no further insight or value for operating mines. Advisian has developed a customised water balance model for a mine in Sub-Saharan Africa, which can be adapted to other locations, to assist in managing water at the site and in particular to predict the current and future water level and volume in the TSF under various rainfall scenarios. The model was developed using Microsoft Excel and requires no specialist skills to operate. Site personnel enter in daily production, water transfer and rainfall data and then view the output dashboards to observe the current water level and volume, decant rates, licensed water abstraction and water supply versus demand. The output dashboards were developed in close consultation with the client to ensure that all of the relevant key performance indicators were included, from the perspectives of all the key stakeholders. This modelling approach focusses on the needs of the people who will actually use the model to actively manage TSFs with the need to involve the model developer as part of ongoing operations eliminated. The simplicity of this approach is now being embraced by other mine sites in Africa and Australia. CITATION:Rafty, M and Lane, C, 2018. Water balance management 101, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 485–490 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By B Miles, D J. Williams, J Ahn, T A. Vangsness

The flooding of open strip coal mines in the Bowen Basin and Hunter Valley Coalfields of Eastern Australia has the potential to soften the spoil and floor materials to produce “mud”. This mud can act as a slip plane or weak zone when spoil is dumped into it, resulting in geotechnical instabilities. It is therefore important to understand the mechanisms and degree of degradation likely to occur within coal mine spoil of different qualities.To investigate this, five clay mineral-rich coal mine spoil samples were collected from the Bowen Basin, and each sample was subjected to wetting and drying cycles to simulate degradation that could be expected on wetting-up in situ, with their particle size distribution analysed both before and after degradation. These results were compared with the results of a modified slake durability test, in which the entire sample was tested.The paper presents the results of the accelerated degradation and modified slake durability tests on each of the five spoil samples. These results were related to the physical and geochemical characteristics of the samples, which highlighted their importance. The modified slake durability test may be used to rapidly simulate the expected in situ degradation of coal mine spoil on wetting-up, enabling susceptible spoil materials to readily be identified.CITATION:Vangsness, T A, Williams, D J, Ahn, J and Miles, B, 2018. Accelerated degradation and modified slake durability testing of clay mineral-rich coal mine spoil, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 83–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By K Seddon

Segregation of tailings on deposition can occur as a result of a) sub-aqueous deposition, and b) sub-aerial deposition at lower solids concentrations (i.e. when the solids concentration is less than the segregation threshold). The effects are likely to be more pronounced in the case of subaqueous deposition.This paper presents the results of an investigation of a sub-aqueous tailings facility.Data from the investigation show extreme variations in particle size and density compared to test results for non-segregated ‘all-in” tailings. The results indicate that on segregation both the fine and coarse splits tend towards a well sorted (poorly graded) mix, and both have significantly lower consolidated density than the all in tailings. This result is reasonably well known for the case of the segregated fines (“slimes ponds”) but less appreciated for the coarse fraction. The results suggest that if the effects of segregation are not allowed for, the overall density of the deposit can be seriously over-estimated at the design stage. Also the quantity of water retained in the tailings can significantly influence water recovery and water balance results.CITATION:Seddon, K, 2018. Segregating tailings – effects on density and water retention, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 299–308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By A Marta

Geomembrane (GMB) liners are being used more frequently for the storage or capping of mine waste due to stricter regulatory requirements relating to environmental protection. The longevity of any liner system will be a function of environmental conditions, design (including materials selection), construction and condition monitoring during operations or closure. Based on experience and case studies, this paper presents a review, from design to handover, of some of the smaller and often overlooked details that can have significant impacts on the performance of the GMB and the project overall.The topics covered will include approaches to selecting and testing GMBs to ensure they are suitable. Design considerations to aid installation and quality assurance during construction. Understanding action leakage rates and the consequences of leakage when it creates whales. Construction quality control and assurance procedures, including a brief discussion on non-destructive liner integrity testing. CITATION:Marta, A, 2018. Geomembranes – from design to handover and some of the lessons learnt, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 190–207 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By D Reid

The engineering properties of soils and tailings often exhibit significant anisotropy. One area where this has been well documents is undrained shear strength. Materials sheared in directions close to the principal stress direction in situ, i.e. triaxial compression, typically exhibit higher undrained strengths than those sheared in other directions such as simple shear. Importantly, along the most common critical failure surfaces relevant to tailings stability, whether primarily through tailings or a critical foundation layer, saturated materials are generally much closer to the simple shear loading direction than triaxial compression. Therefore, testing undrained shear strength of tailings or foundation soils in triaxial compression is likely to result in overestimation of the relevant strengths for design. Although these issues have repeatedly documented in the geotechnical literature for over three decades, they are not appreciated sufficiently across our industry. In an attempt to address and highlight these issues, a review is carried out of historical reference to the importance of simple shear loading. Attention is then drawn to the techniques applied in three recent post-failure investigations, where simple shear testing was applied. Finally, some relevant laboratory test results from a recent project in which the author was involved are outlined.CITATION:Reid, D, 2018. Importance of the simple shear loading direction to the stability of tailings storage facilities, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 274–284 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By E M. Gama, L Resende

The tailings are waste from mineral processing operations. The type of tailings of iron ore processing are classified into sandy tailings and mud. Already the overburden are showing significant levels of useful mineral. Both iron ore`s waste have in your composition phyllosilicates/clay that indicates the potential for use in niche markets as paving and cement. According to several studies, there are various technologies in bench and pilot levels that could be used on a large scale but there is not an economic environment, tax, regulatory and tax set. Many of these technologies are associated with the reuse of tailings and overburden in construction. All these factors influence for that so many initiatives remain in search formats and cannot advance to the new business format. There is no way to set goals of reuse of this waste, as already occurs in China, if there is not a fiscal, tax and economic structure to support such measures. The way to foster and ensure that reuse of tailings and overburden is an incentive for promoting a culture of circular economy that would allow the emergence of an ecosystem between the private, public and Government sectors with the objective of accelerating and subsidize the entire network of reuse of this waste. The closure of the mine could be the tool used to ensure and boost this ecosystem of reutilization to align it with the vocation of the area of the mining law. Following this model, the end of the mining activity could provide a financial return to the local population, a more effective environmental compensation and a reduction in costs related to the closure of the mine. In this study are shown how the Vale is working in the reuse of tailings and overburden.CITATION:Resende, L and Gama, E M, 2018. The challenges of the reuse of tailings and overburden, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 117–125 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By A M. Sardo, D E. Sinnett

This study uses the Q Method to examine how those living in former metal mining landscapes value this heritage and their preferences for the long-term management of mine waste. Such sites are often perceived as derelict or degraded, and of very little value. It is therefore assumed that their reuse, for example for development or recovery of metals, is likely to be beneficial. There are around 5,000 former metal mines in England and Wales, many of which are protected for their ecological, geological or cultural value. The Q Method is particularly suitable for issues where there is no consensus of opinion. We asked 38 residents of six mining areas in England and Wales to ‘sort’ a series of statements based on their resonance with the resident’s perspective; this is the Q sort. The statements covered a range of opinions of the mining legacy, its value and options for its management with a particular focus on the potential for metal recovery from the wastes. Analysis of the Q sorts revealed five perspectives on the mining heritage. All placed a high value on the cultural and ecological value of this heritage, however, they differed in their priorities for long-term management. For example, emphasis was placed on either nature conservation, cultural heritage, water quality or the opportunity for job creation through reworking the mines. Cutting across these themes there were also differing perspectives on the role of experts and local people in shaping the future management of the wastes. This research suggests that the views of local people are nuanced; they value their mining heritage but opinion is split on the most effective way to manage these sites especially where there is an impact on water quality.CITATION:Sinnett, D E and Sardo, A M, 2018. Former metal mining areas in England and Wales – local residents’ preferences for the management of wastes, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 126–134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By D J. Williams

The majority of surface tailings storage facilities continue to employ sub-aerial tailings slurry deposition. Surface TSFs are typically sized and operated in a way to minimise the initial capital cost of the facility, driven largely by the net present value approach to accounting. This generally leads to too small a storage, too fast a rate of rise of the tailings, and difficulties in managing supernatant water. In turn, this results in wet and soft tailings deposits of high moisture content and low density, and the need for frequent and costly tailings dam raises. Further, such tailings deposits often do not facilitate closure and rehabilitation of the facility. Globally, there are on average over two failures annually of such tailings dams, resulting in loss of life, damage to infrastructure and environmental impact downstream, and the loss of company shareholder value and reputation. Recent high profile tailings dam failures are threatening the mining industry’s financial and social licence to operate.Among the physical processes that tailings undergo on sub-aerial deposition are beaching, hydraulic sorting down the beach according to particle size and specific gravity, settling, consolidation, and desiccation on exposure to the sun and wind. Beaching and hydraulic sorting have proved difficult to test at laboratory scale and difficult to model, and are best assessed in the field. Settling, consolidation and desiccation may be assessed at laboratory scale, but to date there has been an absence of tests to form the basis for the design and management of tailings deposition, and ultimate closure and rehabilitation. The paper describes recent advances in tailings testing methods, including a purpose-built slurry consolidometer that tests the settling and consolidation of tailings from a slurry consistency, simulating increasing tailings depth to about 50 m; and a purpose-built instrumented column that tests the settling, self-weight consolidation and desiccation of a surface layer of tailings, also from a slurry consistency. Selected test results from these two apparatus are presented in the paper, together with brief descriptions of how they may be used to better design tailings slurry deposition. In addition, planned further advances in tailings testing methods are briefly described.CITATION:Williams, D J, 2018. Recent advances in tailings testing methods, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 8–37 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By C Armstrong, B Wentzinger

Upstream embankment raises often represent the lowest cost option for increasing the capacity of tailings storage facilities (TSF), but also pose the highest stability risk due to constructing on top of previously deposited tailings.This paper presents an overview of key aspects in the geotechnical investigation and design of upstream raises and some recent lessons learnt from experience across a number of TSFs in Australia. A summary of recommended field investigation and laboratory testing methods is provided with a focus on collecting quality information for design purposes. A strong focus is given in developing an accurate assessment of pore water pressures, which, if not correctly understood can have disastrous consequences on tailings strength parameter interpretation and wall stability assessment in static and post-seismic conditions.The assessment of the contractive or dilative shearing behaviour of the tailings material and rigorous interpretation of design characteristic values are presented. Some comments on stability analysis options and proposed methodology are also provided.CITATION:Wentzinger, B and Armstrong, C, 2018. Lessons learnt in geotechnical investigation and stability analysis for upstream tailings storage facility raise design, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 333–348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By T Alexieva

Since the early 1900s the geotechnical community has investigated every significant failure of a tailings dam, improved our knowledge of the behaviour of the tailings storage facilities, developed analysis methods, compiled lessons learned, and committed to zero failures. The rate of occurrence of tailings dam failures has reduced since the 1980s, however, failures continue to occur and continue to surprise us. At BHP, we have decided to take an approach to the tailings management that is similar to the approach to safety. We are looking at ways to eliminate, substitute, separate or engineer around the hazard (tailings dam failure). As such, our ultimate long term goal would be to eliminate the need for new tailings facilities. Unfortunately, we have not developed yet technologies for extracting many of the common metals and minerals without producing tailings. Our shorter term goal is to substitute the current conventional slurry tailings facilities with less risky dryer facilities. We are working with vendors and research organizations to develop technologies that can be efficiently applied on a large scale. At the same time, we are committed to using the best available engineering to reduce the risks associated with our existing and new conventional tailings facilities. The best engineering can be achieved by people with the appropriate education, experience, attention to detail, discipline and authority. We have implemented a system of governance to make sure, we have the best engineering applied to all our facilities, considering the specific conditions at each site.This paper presents the current tailings governance process at BHP, and the initiatives that were undertook towards achieving a zero failure goal. CITATION:Alexieva, T, 2018. Tailings governance, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 2–7 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By M Barker, H Li

The total number of tailings accidents has reduced from over 50/decade in the 1960s-1980s to less than 30/decade in the 2000s to 2010s. However, the rate of significant tailings dam failures has not been reduced. The significant tailings dam failures the mining industry experienced in the recent history include: Merriespruit, South Africa, 1994; Los Frails, Spain, 1998; Kolontár, Hungry, 2010; Mount Polley, Canada, 2014; and Samarco, Brazil, 2015. The conventional Factor of Safety approach itself may not be enough to further reduce the rate of significant tailings failures due to its limitations such as uncertainty. For example, the same factor of safety could have a vast range of annual probability of failure for different tailings dams, and insufficient consideration of failure consequence. This paper presents a risk based approach for design with the objective being to minimise tailings dam failures, especially those significant tailings failures with high consequence and low probability. This approach includes risk based design and risk management using bowtie tools. In the risk based design, quantitative analysis will be used to estimate the annual probability of failure and the tolerable failure criteria is linked to the consequence category. Bowtie analyses will be used to understand hazards and risks and identify and select independent controls that are effective in preventing and mitigating catastrophic failures. In this paper, examples of risk based design and bowtie analyses are presented and discussed. CITATION:Li, H and Barker, M, 2018. Risk-based approach for minimising tailings dam failures, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 397–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By William Gleason

"Technology of all forms has experienced exponential growth in recent years, and there is no sign of it slowing down. This growth has presented amazing opportunity and significant challenges in nearly every aspect of daily life. Some of these changes are seen and experienced every day as we turn to our smart phones, tablets and smart watches to help with us with everything from directions to the store to managing our health. And other technological growth takes place far away from the public view but can have as much of an impact on our daily life as does shopping at Amazon or connecting with friends on social media.At the “THRIVE 2018, Innovations Advancing Mining” conference presented by SME on Sept. 27 at the Sheraton Pittsburgh Hotel at Station Square in Pittsburgh, PA, the focus was on innovation and how it affects the global mining industry.More than 100 people were on hand for the inaugural event, and they were treated to a unique program that focused on the cutting-edge innovations that will carry the mining industry into the future while increasing safety and productivity along the way.2018 SME President Barbara Arnold was the driving force behind the conference and put together the technical program with a focus on innovation through the entire mining life cycle and into the future. Talks ranged from more efficient and safer ways to extract minerals to some of the most advanced end uses of minerals and metals, including the use of 3D printing to create precision parts for machines and humans from advanced metal alloys.“We need to adapt new technologies to our industry and develop additional technologies as we provide materials and metals for infrastructure and energy development in the United States, around the globe, and to the Moon and beyond,” Arnold told Mining Engineering. “Our inaugural THRIVE conference sets the stage for these innovations to be applied and to continue to be developed. Our mining industry can only continue to thrive with these advances.”"

Jan 11, 2018

By T. P. Weldum, W. Conger

"The objective of the study conducted by the authors is to determine what media size(s) addition will maximize any given plant ball mill’s grinding efficiency (Fig. 1). The functional performance parameters “mill grinding rate through the size of interest,” and “cumulative mill grinding rates” from both plant and smallscale tests are applied to this task. A plant media sizing methodology, and industrial case studies, are provided.BackgroundA previous article (“Ball mill classification system optimization through functional performance modeling,” Nov. 17, McIvor et al., 2017, Mining Engineering) described circuit classification system efficiency (CSE), equal to the percentage of coarse (plus circuit P80 target size) material in the ball mill. It can be measured and then increased through pump and cyclone adjustments. By so transferring the application of ball mill power from fine (minus P80 product size) to coarse material, circuit efficiency is increased and overgrinding is decreased.The other factor that determines overall circuit efficiency is how well the power that is applied to the coarse material grinds it. This is affected by design and operating variables like the media sizing and mill percent solids. From circuit functional performance (McIvor et al., 1990):Circuit production rate of new fine material (t/h) = Power applied to coarse material (kW) x Mill grinding rate of coarse material (t/kWh) (1)The power applied to coarse material is the total mill power multiplied by the CSE. Therefore:Circuit production rate of new fine material (t/h) = Total mill power (kW) x CSE (%) x Mill grinding rate of coarse material (t/kWh) (2) Production rate, mill power and CSE can be measured during a plant circuit survey. The mill grinding rate of coarse material is then calculated. At the circuit target P80 size, this is the mill grinding rate (of coarse material) through the size of interest. The objective is to maximize this rate. The mill grinding efficiency can also be calculated by taking the ratio of the mill grinding rate over the material’s grindability as measured in the lab. Mill percent solids optimization has thusly been achieved (McIvor et al., 2000). For media sizing, maximizing the mill grinding rate on a given ore is equivalent to maximizing the mill grinding efficiency. Ores of different grindability will be part of the discussion."

Jan 11, 2018

By J. F. Burr, D. P. Snyder, G. W. Luxbacher

"The Mine Improvement and New Emergency Response Act (MINER Act) of 2006 (PL 109-236, 2006) established the Office of Mine Safety and Health, functioning as the Office of Mine Safety and Health Research (OMSHR) within the National Institute for Occupational Safety and Health (NIOSH) and provided authority for awarding contracts related to the development and implementation of new mine technology and equipment. The OMSHR external contracts program was formed in accordance with the MINER Act and has since issued more than 150 contracts focused on worker health and safety. Initial funding for this program was provided by the United States Congress through two emergency supplemental appropriations and was focused on emergency oxygen supply, communications and tracking, and refuge chambers (also referred to as refuge alternatives). Since the MINER Act, Congress has continued to fund the program through the annual NIOSH mining appropriation. The program was supplemented starting in 2009 with an academic capacity building program directed toward developing university tenure-track faculty and facilities and supporting graduate students in the area of mine ventilation. Ground control was added as an additional focus area in 2011. A short synopsis of each contract is published on the NIOSH Mining website (www.cdc.gov/niosh/ mining/researchprogram/contracts/index.html) and final reports are available in digital form on request. A summary of the progress OMSHR has made over the 10-year period since the Act was published previously (Snyder et al., 2016).External contracts are broadly classified by the following areas:• Communications and tracking.• Emergency response.o Self-escape and breathing air supply.o Refuge alternatives.o Escape and rescue.• Equipment safety.• Fires and explosions.• Ground control.• Mine environmental systems (mine ventilation and atmospheric monitoring).• Worker/workplace health and safety.Contracts are issued under a request for proposal (RFP), through a broad agency announcement (BAA) or under an interagency agreement (IAA). An RFP solicitation includes a specific problem description and a well-defined scope of work to guide the offeror in preparing a bid to conduct the research. Under the BAA several problem areas are described and the offeror develops the scope of work and deliverables for the proposed research. An IAA is very similar to an RFP except it is a contract between two federal government agencies."

Jan 10, 2018

By Stuart Lister

"When MacLean Engineering chairman and founder Don MacLean got the first question from a minesite about the possibility of addressing ventilation limits through incremental fleet electrification, he was intrigued. It was back in 2015, and the MacLean scissor bolter was already diesel-electric (jumbo trailing cable), so it made sense to him that if they could engineer a battery drive system for the unit’s tramming cycle, they would have the inaugural electric vehicle (EV) MacLean unit.At that time, there were not any entirely diesel-free hard rock mines in existence on the planet, and that remains the case to this day — although the Borden project in northern Ontario is progressing toward that goal (see page 33). This meant there was essentially zero market demand for battery electric vehicles as well as a complete lack of battery technology to address the battery electrification of heavy haulage. Heavy haulage is the part of a typical mine’s mobile fleet with the largest footprint when it comes to diesel particulate emissions, greenhouse gases and wasted energy in the form of heat.Three years later — the wave of battery electrification that is currently picking up speed across the mining industry promises to hit full swing by the early 2020s when a slew of new build, diesel-free mines will start construction. But this movement toward emissions-free mobile fleets is not a completely new phenomenon. Instead, it is an updating of mining technology from a previous generation. What is going on now is the re-electrification of mining. Up until the 1960s, early generations of battery technology (lead acid) and electric locomotive systems were the norm for material and ore haulage in Canada and elsewhere.The thought of a coming paradigm change in mining was particularly pertinent to Don MacLean back in 2015, as he had been part of the era that ushered in the first generation of rubber-tire diesel equipment, when he was a divisional foreman with Inco in Sudbury in the 1970s. He was part of the operating team that was tasked to build a rail loop on one extraction level of the mine. At that time, events on the ground overtook the project, as diesel-powered mobile equipment became a viable option. Once the first diesel scoop was introduced at Creighton #3 shaft, it was clear what the power, haulage capacity and mobility could do for operations and that era of electric rail haulage underground was effectively over."

Jan 10, 2018

By Konner Horton, Adam L. Bedell, Don Del Nero, Brian Jones

"The City of Atlanta’s Water Supply Program Tunnel project includes a 7,315-m (24,000-ft) long, 4-m (13-ft) diameter, hard rock tunnel. A complex aspect of the project involves connecting five, blind bore shafts to the tunnel in a location close to current drinking water reservoirs. During the supplemental geotechnical investigation following the initial contract award, results from additional borehole geophysics were reviewed. Unfavorably oriented fracture sets forced a change in the original pre-excavation grouting program designed for that site. Real-time grout monitoring and geophysical data were compared to provide assurance that the program, as designed, correlated with the in situ ground conditions. Following grouting, results were modeled, and all grouting data were reviewed to determine if grouting was complete.Project backgroundThe current water supply system operated by the city of Atlanta’s Department of Watershed Management (DWM) consists of four, aged, raw-water pipelines, one of which dates back to 1893. Based on previous assessments completed by the DWM, the entire water supply system is at, or will soon reach, its recommended useful life. As such, the city acquired the Bellwood Quarry in 2006 with the intention to create a water storage facility with a volume of approximately 9.1 billion L (2.4 billion gal) to serve approximately 1.2 million people.The project location is shown in Fig. 1, which is generally in the northwest part of downtown Atlanta, GA. The overall project has been divided into two phases. The Phase 1 project connects the quarry and the Hemphill Water Treatment Plant (HWTP), and the Phase 1 Extension project connects the HWTP to the Chattahoochee Water Treatment Plant (CWTP) and the Chattahoochee River. A 7,315- m (24,000-ft) tunnel with a finished diameter of 3 m (10 ft) connects all three elements. The HWTP location is also where the city’s two most proximate drinking water reservoirs are located."

Jan 9, 2018