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By H Ramandi, H Masoumi, I Canbulat, B Hebblewhite, J Oh, S Saydam, W Timms, S Mo

This paper reviews the floor heave mechanisms in underground coal mine roadways. Previous studies have reported three main failure mechanisms: bearing capacity failure, buckling and swelling. The buckling failure has been observed where immediate floor strata are relatively strong and thinly bedded. On the contrary, the weak floor strata have been associated with both the bearing capacity failure and swelling mechanisms. The bearing capacity floor failures are likely to induce other types of instability such as pillar punching, tensile failure of pillar, roof fall and subsidence as well as floor heave. Despite a considerable amount of research, predicting the magnitude, location and timing of floor deformation is challenging with current state of knowledge. CITATION:Mo, S, Ramandi, H, Oh, J, Masoumi, H, Timms, W, Canbulat, I, Hebblewhite, B and Saydam, S, 2018. A review of floor heave mechanisms in underground coal mine roadways, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 196–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By A De, B Palmer, rade, P Stowasser, A Fanning

Mining and tunnelling share many commonalities (eg confined working environments, excavation equipment and processes), but of significance is an overarching commitment to provide safe work conditions and environments. This includes reducing exposure to hazardous airborne contaminants such as dust and fumes, in particular Respirable Crystalline Silica (RCS) and Diesel Particulate Matter (DPM), with methods that are environmentally sustainable. In mining, wet methods are common to suppress airborne contaminants, however these methods are reliant on water availability, can be less effective for respirable dust, can have implications for environmental water contamination and can increase maintenance on mining equipment. In contrast, the use of dust scrubbers that provide filtration of airborne contaminants are well established in the tunnelling industry and frequently used to provide spot extraction (dust control at the source) and act often as a complement to the main ventilation system. This paper sought to learn more about the advancements in tunnelling that could be readily applied to mining to improve health outcomes. The paper includes a review of literature and legislation related to health and sustainability and interviews with three respected, and experienced managers from the global tunnel construction industry. It is from these interviews that the focus of the paper turns to Sydney’s WestConnex underground tunnel network and the success of stage 3A M4-M5 construction link. The findings position dust scrubbers as integral to the overall project success as they enabled a Tunnel Production Line (TPL), where multiple stages of construction could take place simultaneously by controlling high volumes of dust at the source. The findings also suggest efficiencies of using mobile scrubbers, both track mounted and hydraulic stepping systems, to accompany road headers and other equipment throughout the excavation process. The findings have transferable applications to underground mining processes in which workers are exposed to high volumes of dust (eg drill and blast) or situations in which dust control at the source, mobility and flexibility offer value (eg room and pillar mining).

Apr 16, 2024

Sampling systems are never perfect. They all have some bias and give variable sampling errors. The ways of thinking about bias and precision should be different before and after construction (or reconstruction) of a sampling system. Before a sampling system is constructed, the fundamental error variance can be estimated using GyÆs formula or by doing test work on the material to be sampled. The component of sampling variance which varies with the number of sample increments can be computed for the expected patterns of grade variation. The smallness of the bias can be checked using discrete element modelling, by checking that the proposed design complies with clauses in standards, or by copying an existing sampling system that performs well for similar material. After a system has been constructed, sampling precision can and should be monitored directly. Anyone claiming to take responsibility for a sampling system should know its precision. Bias could be checked by comparison to a more accurate sampling system, such as stopped-belt sampling, under conditions where bias seems most likely. However, it is more practical to conduct regular checks that the system is still operating as designed, that the design is still appropriate despite any changes to material flows, and that sample masses are consistent with the correct operation of the sampling system. If precision is not regularly assessed then it should be assumed to be very poor. If a sampling system is not regularly inspected then it should be assumed to be biased.

Jan 1, 2008

The district specially referred to in this paper comprises the very gently sloping country extending from the western shores of Port Phillip from the mouth of the Yarra to Footscray along the Bacchus Marsh railway to near that town thence in a southerly direction to the Little River, and along that river to the coast, 1 as may be seen on the accompanying map. Almost the whole of this area is covered by volcanic rocks, consisting of pumerous sheets of basalt, which have been poured out of various volcanic hills in the districts, such as Mts. Atkinson and Cotteril, near Melton; Mt. Maryand Bald Hill, 12 and 16 miles respectively N.W. of Werribee; and vents in different parts of the parishes of Tarneit, Mouyong, Mooradoranook, Pyweitjorrk, and Derrimut. These volcanoes were in an active state of eruption during a late period of the earth's historyprobably the late Pliocenll, or still younger Pleistocene.Occupying a narrow strip of country, for most of the distance along the coast from Williamstown to past the mouth of the Little River, there occur deposits of still younger age, belonging to the Recent period. These lie on the basalt, and extend for distances varying from a few chains to more than a mile back from the beach. They comprise superficial deposits of blown sand, and raised beaches, composed of marine sands...

Jan 1, 1902

By J Bower

The JORC Code does not specify a definition for ælevel of confidenceÆ. The common approach in the mining industry is to use a certain drill spacing or number of data samples to classify resources by the confidence categories. Another approach includes application of the quantitative geostatistical criteria for non-subjective and consistent definition of the resource categories. This approach, which has become increasingly popular in the mining industry, provides a quantitative measure of the resource estimation uncertainty. In this study, uncertainties associated with the different drilling grids at the Weipa bauxite deposit (Queensland, Australia) have been modelled using conditional simulation methodology. Criteria used at Weipa for defining resource categories are as follows: mineralisation can be classified as a Measured Resource if tonnage and grade of its volume representing three months of production can be estimated with a precision error not exceeding ¦10 per cent (at 95 per cent probability, ie two standard deviations); and mineralisation can be classified as an Indicated Resource if grade and tonnage of its volume representing annual production can be estimated with a precision error not exceeding ¦10 per cent (at 95 per cent probability). Several different grids have been created by subsampling the drill hole database. The studied variables include Al2O3, SiO2, thickness of the bauxite seam and location of the footwall contact. The variables have been modelled by sequential Gaussian simulation. Based on this study the following drill spacings have been recommended: Measured Resources û 150 m by 150 m, Indicated Resources û 300 m by 300 m.

Jan 1, 2009

Alkaline leaching with sodium carbonate solution adjusted to pH 9·5 to 10·0 preferentially dissolves thorium from a mixture of rare earth and thorium hydroxides. Rare earth sodium carbonates form in the alkaline leaching stage.These are converted to rare earth oxides for use as optical and ophthalmic polishing agents. Quadrivalent cerium is extracted under similar alkaline leaching conditions.INTRODUCTIONAustralia has made significant contributions to mineral chemistry and mineral dressing. As often happens with an industrially immature country, research investigations often outstrip the ability or desire of commerce to exploit them. It is wrong to think exclusively in terms of export of raw materials. Imagination assists in developing world trends. The chemical utilization of mineral sands has interested a group of investigators, chiefly at the Commonwealth Scientific and Industrial Research Organization (C.S.I.R.O.) and, more recently, in the mining industry itself. From an international point of view the highlight of this work was Newnham's (1960) process for the separation of hafnium from zirconium. Earlier work at C.S.I.R.O. investigated the chlorination of rutile, zircon, and monazite. Assuming that titanium tetrachloride would be available in large quantities in the post war years, extensive work was done by Kraitzer, McTaggart, and Winter (1948) on organic compounds of titanium. This work led to the development of heat resistant paints, plastic compositions, and improved organic protective coatings that predated overseas work by up to seven years. (Post, Shiihara and Schwartz, 1961; Anon, 1955). Contributions were made to the production of refractory hard metals (Kraitzer, 1949; Kraitzer and Newnham, 1956). Pilkington and Wylie (1947) and Urie (1947) investigated the production of rare earths from monazite by an acid process.

Jan 1, 1963

By G Stephenson, G MacDonald, A Yeomans, S Sinclair, V Knott

Rio Tinto has actively committed to progressive reclamation, concurrent with commercial operations, at its Diavik Diamond Mine. The most significant piece of progressive reclamation undertaken at Diavik to date has been the construction of an engineered thermal rock cover for the mine’s largest waste rock storage area. This 80-metre-tall and 2000-metre-long area is known as the Waste Rock Storage Area – North Country Rock Pile (WRSA-NCRP) and contains the operationally segregated potentially acid-generating waste rock mined over the last 20 years. As part of the mine plan, an opportunity was recognised where a limited 1.5 per cent of the WRSANCRP surface area was required for storage of the balance of life-of-mine generated waste rock and a decision was made to advance the closure design almost a decade ahead of final closure. With over 12 860 000 tonnes of material placed and 57 443 dozer hours logged since cover construction, progressive reclamation on the WRSA-NCRP is scheduled to be complete in mid-2023, three years before planned cessation of commercial operations in 2026. The progressive closure of the WRSA-NCRP demonstrates Rio Tinto’s commitment to not only closure, but modern best practices with integrated mine closure. Over the past seven years, Diavik has overcome multiple implementation hurdles for this project including the psychology of operational standby, the financial mechanisms required to support closure, working within the constraints of a mine plan and the associated operational organisational structures. This paper outlines the lessons learned to provide an example of successful integrated mine planning for closure. The North Country Rock Pile project had three major learnings which resulted in an effective organisational structure that allowed for the execution of an integrated planning model for progressive closure. The initial hurdle the project faced was adapting the psychology of an operational open pit mining team. The team was an experienced mining group who came in with the perspective to target the shortest haul possible resulting in the initial perception that the longer haul of material to the NCRP was an un-necessary task impacting operational performance metrics. After the installation of an improved dispatch tracking system and performance metrics, it was possible to demonstrate that the mine was shovel constrained. This showcased the short haul was generating an increase in queue time not production. With updated performance metrics, the team was aligned to target a decrease standby through haulage to the NCRP. These performance metrics had to be reinforced by financial mechanisms. The operations team was able to offset costs by charging time to the capital project set-up for the closure of the NCRP. This allowed the operations team to receive credit for time that would have otherwise likely been standby. As well, the progressive closure project was able to receive the benefit of not having to incur costs for the drill, blast and load as that was done as part of the operation. This was a significant benefit to the project and one of the primary drivers for the early approvals of the work as the project costs were limited to the incremental haulage distance and placement of the material. Life of Mine Conference 2023 | Brisbane, Australia | 2–4 August 2023 114 While the combined operational and progressive closure approach provided financial advantages, it did result in the project being constrained by the operational activities. A traditional capital project is managed through a linear execution plan where the deliverables within a project are within the realm of control of the project execution team. However, the NCRP project had to be continuously adapted to the outcomes of the pit operations. This included geotechnical constraints, ore delivery, and other operational delays. To adapt, the planning module had to be dynamic but not reactive to allow for adjustments on a shift-by-shift basis. Based on this requirement the Diavik Closure Projects structure adopted a mine planning format. The team executed a similar planning timeline and reporting structure as the mine operations team, allowing planning to be integrated into the operational planning structures on a daily, weekly, monthly and quarterly basis. This resulted in the Projects team as a core pillar of the mine planning team. The process of continuous improvement spanned six years and has resulted in the project being ahead of schedule and under budget for the project’s scheduled progressive closure completion date of June 2023. The North Country Rock Pile project supports the argument that bulk earthworks progressive closure projects should be integrated into the operational mine plan. If the project is aligned the mine plan it allows for dynamic adjustments which capitalise on evolving opportunities inevitable in an operating mine. These cultural and organisational alignments should be supported by appropriate performance metrics and financial mechanisms to ensure united priorities. The result of this alignment provides long-term financial savings for the business as well as delivery of closure objectives.

Aug 2, 2023

By D Cliff

"Recent underground coal mine incidents have again raised the issue of: under what circumstanceis it safe for personnel to re-enter the mine? Mine rescue guidelines make recommendations aboutthe limits in terms of the circumstances, lives at risk, no lives at risk and training exercises. Theseare based upon percentages of the upper and lower explosive limits. Many factors infl uencesett ing limits for safe re-entry. These include: the representativeness of the sampling location(s),the rapidity of gett ing an underground sample analysed and the rate of change of the atmospherebeing monitored. Value judgements based upon these parameters will then infl uence the sett ing ofa trigger point based upon per cent explosibility. This raises the question of how the percentage ofthe lower or upper explosive limit is established. It is easy to defi ne this when the sampling pointdata sit on the fresh air limit line. However - what value is used when the sample sits somewherein the body of an explosibility diagram? This paper explores the various options and illustratesvarious pitfalls and problems that are faced in making such a determination. These include howthe data are represented and the assumed knowledge of those doing the interpretation."

Jun 1, 2012

By O Omidi, P D. Katsabanis

The effect of delay time on fragmentation has been discussed for a long period but rarely in a satisfactory and unbiased way. Despite the efforts of many researchers, delay selection for fragmentation improvement or optimisation remains a controversial issue. Large-scale tests have been plagued with scarcity and scatter of observations, while small-scale tests have been associated with boundary effects and energy losses. Theoretical work is often used to produce explanations for available measurements or tries to simplify wave propagation and wave interaction to guide observation and practical work. The present work analyses results obtained from a relatively large number of small-scale experiments in blocks made of grout, and re-analyses results of previous experiments, to conclude on the effect of delay on fragmentation. It is shown that the main contribution of the delay is found in the fragmentation of the larger fragments of the blast, while the small fractions show almost no effect. Samples, where copper liners were used to inhibit penetration of detonation products in the rock mass, showed effect of delay only when short times were used and steady but poor fragmentation when long delays were used. Based on small-scale experiments, it appears that the fragmentation is optimised when a hole fires prior to the radial cracks, produced by the previous hole, reach the free face of the blast. Gas penetration may result in the development of few more fractures that affect the fragmentation of the largest particles of the blast.CITATION:Katsabanis, P D and Omidi, O, 2015. The effect of delay time on fragmentation distribution through small- and medium-scale testing and analysis, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 715–720 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Hemingway P, Boag J

Major operating aspects of the Mary Kathleen Uranium Ltd. treatment plant are discussed with partkular reference to those which are peculiar to this operation.Problems associated with the production of a penalty free uranium oxide product are examined and the methods developed to overcome them are described in detail.INTRODUCTIONMary K,athleen Uranium Ltd. is the largest of the Australian uranium producers. The flow-sheet is based on fine grinding, standard sulphuric acid leach, ion exchange concentration, and magnesia precipitation of the final product, with certain modifications introduced as the result of pilot plant investigations at the South Australian Department of Mines Research Laboratories in Adelaide.The plant commenced operations in June, 1958, attained design tonnlige of 1,120 tons per day in September of that year and has since operated continuously with a throughput in excess of 1,000 tons per day. Pilot plant recommendations generally have been followed, and predicted results have been attained. The only exception has been the silica and rare earth content of the product produced during the early months of operation. Considerable modification of the early resin regeneration techniques resulted in the reduction of the silica content of the product to within specification limits. Research work in the ion exchange section has also resulted in the reduction of the rare earth content of the product to below specification levels. All product now being produced is completely within the agreed specification limits of impurities.

Jan 1, 1961

The Nena high sulphidation-type copper-gold deposit is composed of andesitic pyroclastic units with minor interstratified lava flows. Epiclastic sandstone and conglomerate, and siliciclastic rocks consisting of mudstone, shale, lithic and bioclastic sandstone and conglomerate are locally present. Pre-mineral diorite intruded and domed the volcano-siliciclastic sequence. Economic copper-gold is hosted by vuggy quartz altered lapilli tuff and tuff breccia. The early hydrothermal alteration stage involved deposition of epithermal banded quartz and chalcedonic silica in localised environments. This alteration stage was locally superimposed by a hydrothermal breccia event. Following the breccia event, magmatically-derived volatiles were channelled through a NW striking dilational fault zone and generated the high sulphidation alteration. The high sulphidation alteration is zoned from a vuggy quartz core with local massive replacement silica through a broad pyritic quartz-alunite halo and finally to a thin illite-smectite zone. This is surrounded by regional chlorite-epidote-smectite alteration. A gangue mineral phase consisting of quartz, alunite and baryte overprinted the zoned high sulphidation alteration and preceded the main copper-gold-arsenic mineralisation. Early sulphide deposition is characterised by marcasite, arsenical pyrite and melnicovenite. Main-stage copper-gold mineralisation involved sequential deposition of hypogene bladed covellite+chalcocite, enargite-luzonite and luzonite+stibioluzonite respectively. The copper sulphides are zoned from bladed covellite-chalcocite in the north (cross-sections 5000 - 5600 N) through enargite-luzonite (cross-sections 4700 - 5000 N) and to luzonite????stibioluzonite in the south (cross-sections 4400 - 4700 N). A late phase of minor acicular covellite and enargite+luzonite overprinted the zoned copper sulphides and associated gold mineralisation. Gold mineralisation commenced at the transition from enargite to luzonite, and continued through the deposition of luzonite-stibioluzonite in both stages. Most gold was deposited during the main-stage mineralisation. Yellow native sulphur was deposited in the remaining vugs and defines the waning stage of the hydrothermal system. Post-mineral dioritic intrusives and feldspar porphyries intruded the volcano-siliciclastic sequence. Finally, supergene chemical processes with associated erosion and uplift generated a 40 - 50 m thick oxide-hosted gold cap. The oxide gold cap is underlain by a 35 - 45 m thick blanket of supergene chalcocite+covellite mineralisation which overlies and occurs throughout the main hypogene copper-gold zone. Supergene gold is related to the distribution of primary gold-bearing sulphides. Therefore, remobilisation and redeposition of gold are considered to be insignificant and very localised.

Jan 1, 1999

By Y Ren

?ptim?sgtion t?ols nos ope? 0iu ?ingc s?ch as the cche??ling and?pi? k?(i?isatTon tool{ ?ave bg?ome(?osd-dvfective way? to e?iluata open`¦it mi~e!p?n?ept as w?ll asá?}prmv?ng mine?projecW`value> ?owerez

Aug 12, 2013

In the Ngakuru area, zeolite deposits occur in late Quaternary lake sediments and ignimbrites. The deposits are associated with sinters, hydrothermal eruption breccias, and quartz-adularia altered fault breccias: all indicators of a shallow epithermal environment. Several of the deposits are adjacent to epithermal gold prospects. Zeolites are most abundant in lacustrine tuffs of the Ngakuru Formation, a 100-300 m thick sequence of siltstone, tuff, diatomite, sandstone and conglomerate. The formation overlies the Ohakuri Ignimbrite dated at c. 270 Ka, and is unconformably overlain by alluvial sands and gravels which are younger than 20 Ka. Individual zeolite deposits contain 30-80 per cent zeolite over a thickness of up to 45 m in thinly stratified tuff beds. The tuff beds are locally overlain by diatomite. The tuffs are composed mainly of glass shards and pumice clasts, with minor volcanic plagioclase, quartz and biotite crystals. Glass shards in the tuffs are replaced by the silica-rich zeolites mordenite and clinoptilolite. Amorphous silica (opal A), opal-CT, K-feldspar and smectite are also present. The distribution of the Ngakuru Formation is controlled by northeast trending normal faults, which separate it into the Ngakuru and Guthrie grabens. A silicified (quartz-adularia altered) hydrothermal breccia along one of the fault zones suggests that the faults acted as feeders for heated water that caused the deposition of the zeolite minerals. Some of the zeolite deposits are adjacent to sinters and hydrothermal eruption breccias. The location of the sinter about 20 m above one deposit indicates that the zeolites were formed at a depth of 20 to 70 m below the paleosurface. The hydrothermal eruption breccias contain clasts of altered ignimbrite, which contain geochemically anomalous gold and silver values. By analogy with their occurrence in active geothermal systems in the Taupo Volcanic Zone, mordenite and clinoptilolite in the Ngakuru deposits probably formed at temperatures of 60-150oC from near-neutral pH waters as a result of interaction with glass-rich tuff beds. The Ngakuru zeolite deposits are therefore interpreted as shallow hydrothermal alteration zones within larger epithermal gold-bearing systems.

Jan 1, 2002

By M Zlatev, S Silge

Producers of primary resources such as iron ore face the challenge of processing crude materials with increasing levels of impurities, which may result in the requirement for wet processing. This results in a significant increase in water usage, power consumption and operating costs. Given the remote locations of most operations in Australia (Stewart et al, 2013; Prosser, Wolf and Littleboy, 2011), the required volumes of power and fresh water for wet processing can be very difficult to achieve.HAVER&TYLER is renowned across the world for their screening technology in wet and dry processes. Its innovative Hydro-Clean® system represents a cost-effective and eco-sensitive way to clean any crude materials and material blends with a grain size distribution of 0–150 mm that are contaminated with adhesive clay, slit and other impurities.CITATION:Silge, S and Zlatev, M, 2015. Iron ore washing – achieve more with fewer resources, in Proceedings Iron Ore 2015, pp 519–528 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Tucker A. J

An overburden blast utilising horizontal blast holes was successfully attempted at the Ulan Coal Mines during December 1991. The blast reduced operational problems and costs and improved dragline productivity in an area of that contains poorly consolidated sands and clays overlying very hard Permian strata.The fan shaped shot consisted of seven 250 mm diameter holes between 80 and 95 metres long drilled into the highwall face. The holes were loaded with ICI Powergel Gold 25606 bulk Emulsion explosive. The design powder factor was 0.15 kg/bcm for the total shot of 180 000 bcros and 0.44 kg/bcm for the competent Permian strata into which the holes were drilled. Fragmentation from the horizontal blast was comparable to areas conventual blasted. Following the success of this shot further shots are planned for this area.

Jan 1, 1992

By Y K. Leong

Occasionally additives are used in the wet processing of iron ore tailings and slurries, for examples, in the thickening of tailings with flocculant to recover process water, and in the smooth pumping of concentrated slurries. They can mitigate slurry behavioural issues that could significantly affect the plant operation and production. The nature of iron ore business requiring the plant to have a high throughput to be economical, large amounts of slurries are therefore processed every day. The quantity of additives needed will correspondingly be large and so are the associated costs. This could have a significant impact on the plant profitability. If additives are used they must be very costeffective. NaOH is among the lowest cost chemicals available, at ~US$400 per ton. In this paper we will look at use of composite additives involving phosphate compounds with NaOH added to reduce the cost, for the control of iron ore slurries rheology. The NaOH worked synergistically with the phosphate compounds. The effectiveness of these composite additives in viscosity reduction can be neutralised by another cheap additive such as lime or a Ca(II)-based salt turning the slurries back to being a paste. Tailings paste is an ideal material for safe storage in the dam. These composite additives can also be used to facilitate the recovery of iron ore at commercial grade from tailings (Leong, 2020a, 2021a).

Sep 18, 2023

Over the past few years, there has been an emerging relationship between business and civil society, especially NGOs. This relationship has the potential to bring about significant change, identifying common ground between commercial and societal interests. The mining industry has been a leader in acknowledging the need for community consultation and engagement. This paper argues that partnerships can make a very significant contribution to the industry as it comes to terms with the dilemma of an open economic system pushing against a closed ecological system.The paper will pose a number of questions: where is the locus for debate about sustainability in the mining sector?; how well embedded within companies are the new competencies that Leon Davis first identified in 1995 for the mining sector?; how has education for mining engineers or exploration geologists changed to prepare people for what are very different expectations within the working environment?; how well is the industry doing in managing its own environmental impact and what is its responsibility to an agenda for sustainability which extends beyond its own operations?;and how can NGO partnerships contribute to more sustainable outcomes? The paper does not aim to answer these questions, but to explore them in the hope that the issues and possibilities raised will contribute to advancing progress towards sustainability within the industry.

Jan 1, 2002

THE old mill erected by the .Irvinebank Company consisted of 10 heads of stamps (850 lb.), rock-breaker, Hartz jig, two Krupp tables, two Luhrig vanners, three sand-pumps, one mixer; six flotation vessels, and the necessary settlers. Power was supplied by a small colonial-type boiler, and 10-in. x 15-in Tangye engines. The ore was darted from the mines to the mill and hand-fed, into the rock-breaker, and the broken product elevated into the batter bins and fed into the stamps, the pulp from the stamps passing to a classifier, the spigot to jig, tables, and vanners, the overflow from the classifier passing to settlers. After the removal of bismuth-wolfram concentrates, the pulp was pumped to the molybdenite flotation plant and the olybdenite recovered by flotation.A commencement was made with the erection of the first unit (20 heads) of the new mill in August, 1917, and milling and concentrating commenced in February, 1919.

Jan 1, 1920

By W M. Tekano, T S. Coulter, N M. Hutt

The Vancouver Island Highway Project (VIHP) was a $CAD 1.2 billion expenditure by the Province of British Columbia to improve travel safety and relieve traffic congestion between Victoria and Campbell River on Vancouver Island. In the section of highway between the Tsolum River and Oyster River, on the Inland Island Highway portion of the VIHP, over half of the rock to be cut and filled was found to be net acid generating. The Tsolum River has been impacted by metal leaching and acid rock drainage (ML/ARD) for decades from an upstream closed minesite. Geochemical testwork indicated: over half of the rock along this section of highway was potentially net acid generating based on a site-specific SNPR (=NP/SAP) criterion of 1.5; some core samples were already acidic; pyrite occurred in disseminated framboidal and gel forms; the rate of acid generation was not high; measured neutralisation potential (NP) provided some lag time for the onset of net acidity; and non-carbonate neutralising minerals prevented low pH (These predictions led to ML/ARD controls involving: realignment of the highway; elevation control to minimise the volume of disturbed rock; encapsulation of blasted-rock fills within the highway, surrounded by low-permeability till and covered with asphalt; and diversion of water away from cut faces. Internal pipes drained any water reaching the fills into external ditches and ponds, where the water could be monitored and, if necessary, treated. Water from the cuts was also captured in ditches and carried to monitored ponds. Elevated aqueous sulfate concentrations in several ponds confirmed that sulfide minerals were oxidising, but the lack of both acidic pH and increasing trends in concentrations demonstrated that ML/ARD was controlled. Contingency plans for any pond that may become acidic include water treatment, which predictive testwork has shown would not require substantial amounts of limestone or lime.

Jan 1, 2003

By D J. Williams

Tailings management is typically constrained by many factors that are taken as given. These include the tailings production rate that must be accommodated, the desire to deliver the tailings cheaply and easily as a slurry using centrifugal pumps, and a tailings footprint limited by the desire to minimise capital costs leading to a rapid tailings rate of rise and a low settled density. Other constraints include wall raises being delayed due to limited capital, inadequate tailings water and rainfall run-off management, and the net present value (NPV) approach to capital expenditure that puts off expenditure at the expense of performance. All of these constraints result in the tailings occupying much more volume than is necessary, being difficult to rehabilitate, and not being capable of supporting a beneficial post-mining land use or function. Ultimately, such constrained tailings storage facilities will assume very large dimensions, but each will typically be developed as a series of smaller storages that are filled rapidly and added to progressively. The optimal stage to efficiently recover process water is in the process plant, but this is limited by the desire to use centrifugal pumps rather than the more costly positive displacement pumps, which also require greater management of tailings deposition. Process water can also be recovered from the tailings storage facility (TSF) decant. Tailings water that is not recovered from the plant or the decant will be lost to entrainment within the tailings, seepage to the foundation or through the wall, or evaporation. However, tailings water is not always suitable for reuse in the plant, particularly when it becomes contaminated by the processing, and it may simply be stored on the TSF. This will exacerbate the seepage of contaminated water to the environment, and will limit the densification of the tailings that would otherwise occur due to desiccation of the tailings on exposure. If a larger tailings footprint were developed early, cycling of tailings deposition in thin lifts between a number of cells could occur, maintaining the dormant cells dry to enhance desiccation and densification, and ultimate rehabilitation. The end result would be a much reduced stored volume of tailings, the potential for upstream raising, and ease of rehabilitation to a high level. The higher initial capital cost would be overtaken by reduced ongoing capital, operating and closure costs.CITATION:Williams, D J, ?2014. An alternative whole-of-life approach to tailings management, in Proceedings Life-of-Mine 2014 , pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014