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By C Augustin, M Hahn, K Nienhaus

Operators of mining machinery like haul trucks or excavators have very limited information about the exact distance to other equipment as well as to the natural boundaries like berms, walls and structures such as crushers. The industry is seeking solutions to provide safety and positioning. The authors have developed a solution approach which is being used in several installations. This solution consists of three parts: first robust and compact two-dimensional (2D) radar scanners that provide range and angular information of the environment especially under difficult conditions like dust, rain, snow and fog; second an intelligent data processing framework flexible enough to adopt to different machines and operation modes like speed, inclination, visibility, tire friction, GPS position, orientation and acceleration; and third a high quality and easy to use interface giving highly condensed data to the operator, not blinding the operator at night and being sunlight readable. The truth of present proximity detection sensors is that they not only have a high false alarm rate but furthermore cover only a fraction of the possible scenarios. This makes them unsuitable for stand-alone collision avoidance systems. On the other side, mine dispatch systems only deliver database and GPS information, but no information regarding the real environment. The indurad company and its Australian partner CTS (http://www.cts.com.au) addressed these aspects by developing smart productivity enhancement driver assistance tools like lane and crusher dumping assistance.An innovative driver assistance tool developed in cooperation with the coal shearer manufacturer Eickhoff and the RWTH Aachen University has been awarded with the annual research award of its customer RAG, being the largest German hard coal producer, as well as with the bauma Innovation Award in 2010.

Sep 26, 2011

The Ernest Henry Mine is an open pit copper-gold mining operation located in north-west Queensland, Australia. It is owned and operated by Xstrata Copper with a current concentrator throughput of approximately ten million tonnes per annum. The pit will cease mining towards the end of 2010. Extensive surface diamond drilling has confirmed an extension of the orebody to depths of 1000 m below surface. A prefeasibility study was commissioned in late 2006 to investigate underground mining options with the preferred mining method being an inclined sublevel cave. In February 2008 mining of a decline commenced in conjunction with a feasibility study to further investigate the project. Work from the prefeasibility study indicates that an underground crusher, conveyor and hoisting shaft could be utilised to crush and transport broken ore from the sublevel cave workings to the concentrator. The study suggests that a production rate of five million tonnes per annum could be achieved and sustained for up to ten years. Ventilation designs and requirements will form a large section of the feasibility study. This paper will detail investigations of preliminary ventilation network designs of the proposed sublevel cave. Work has been completed using both Ventsim and VumA ventilation simulation packages. Ventsim was used to provide preliminary estimations and suggest alternatives for: surface fan duties;airflow characteristics (direction, velocity, pressure and quantity); andventilation network design in key mine areas. With mining activities reaching depths in excess of 1000 m below surface an analysis of heat conditions should be conducted. The VumA software package was used to model the thermal properties of the ventilation system. This model will provide a basis for the preliminary decisions on refrigeration requirements for the mine.

Jan 1, 2008

The extraction of world-class mineral deposits using massive underground mining techniques is not an entirely new theme to world mining companies and experts. Previous MassMin conferences have helped to gather and disseminate the valuable experience and knowledge so important for the proliferation of safe and efficient mining of large underground deposits. With the passing years since the first MassMin conference in Denver in 1981, a number of factors have contributed to an increase in massive underground mining around the world, including environmental pressures, gradual exhaustion of shallower deposits and the enabling effects of improving technology in disciplines related to underground mining. Massive underground mining is heading deeper, embracing challenges which include working with elevated temperatures, increasing in situ and mining induced stress levels and longer ore transport routes. Improvements in mineral processing technology will tend to lead operators to contemplate the extraction of lower grade orebodies in the event that the ore can be efficiently transported to the surface and hence the plant. No doubt this tendency, and its associated challenges is encouraging a rich growth in innovative engineering in such fields as mine planning and materials handling as well as geomechanical issues such as support design and the simulation of extraction sequence effects on stress re-distribution. MassMin 2000, we are sure, will showcase a wide variety of new contributions in thought and actions in these fields. There is a definite place for academic institutions and mining related suppliers in the process of developing new technologies and practices in support of present and future endeavour in this field. Dyno Nobel has its own part to play, certainly as an enthusiastic and proud major sponsor of MassMin 2000, but also by means of identifying common cause between our Vision and Values and the needs, present and future, of the underground massive mining industry. The critical success factors, which Dyno Nobel pursues are:health, safety and environment, customer relationships and market development, cost optimisation (while maintaining quality), technology and innovation, organisational development, and leveraging capabilities globally. Through the present paper we would like to share some of these values and offer some practical insights as to how their realisation will contribute to the achievement of MassMin goals and needs.

Jan 1, 2000

Anglo Platinum recognised with its expanded operations the need to change its evaluation strategy due to increased sample volumes and the pressure it created at laboratories. The sender/receiver analytical scenarios had to change in order to curb costs and to prevent substantial investments in new sampling and analytical facilities. Given the high cost associated with correct sampling systems and sampling protocols and the shortage of technical resources a strategy of single point sampling and analysis was introduced. The analysis was then done at an ISO17025 accredited laboratory with ten per cent checks, subjected to careful statistical scrutiny. Logistical problems increased with respect to weighbridge congestion, maintaining sampling quality, throughput of samples in the sample preparation areas, manual quality control systems in place, audit trails and analytical capacity throughout all operations. This required the expedited improvement of existing sampling practices and the development of new sampling methods and equipment. Anglo Platinum is classifying and standardising sampling equipment, sample preparation and analytical procedures for all process streams with the view to minimise overall uncertainties. Major investments were made into a customised LIMS and automated equipment for data management, reduction of manual transcription errors and streamlining of sample processing. Anglo Platinum is committed in rolling out the enhancements to all sites as priority dictates.

Jan 1, 2008

By A R. Cruden, M S. Egglseder

The formation of banded iron formation (BIF)-hosted high-grade iron ore deposits in the Hamersley Province, Australia has been debated for decades. Although a structural control on their formation is widely accepted, only the roles of large-scale structures (ie faults and folds) formed by brittle and ductile deformation have been considered to date. However, the deformation of multilayered sequences in the Hamersley Province (ie the Mount Bruce Supergroup), with their contrasting rheological behaviours, creates challenges for understanding the complex structural framework at regional to deposit scales, including the significance for mineralisation and orebody location.Our approach to understanding these complex relationships is based on an established principle of structural geology, which is to extrapolate microscale structures to deposit-scale structures and vice versa, supported by state-of-the-art 3D modelling techniques. Complexly deformed hand samples associated with the Mount Tom Price iron ore deposit (Hamersley Province, operated by Rio Tinto Ltd) have been analysed and visualised with 3D explicit (Move™, Midland Valley Ltd) and implicit modelling software packages (Leapfrog™, AranzGeo Ltd) and supported by microstructural investigations (optical and X-ray microscopy) and fieldwork.Our study shows that the deformation of BIFs in the central Hamersley Province is controlled by microscale chemical processes (ie dissolution precipitation creep) due to rheological differences between iron oxide and chert layers, contrasting fluid flow properties and layer thickness variations. These processes account for the removal of vast amounts of silica, its transportation by diffusion in the presence of a fluid and reprecipitation at low-pressure sites. Consequently, this structural framework was used by different upgrading fluids to form iron orebodies.CITATION:Egglseder, M S and Cruden, A R, 2015. Evolution of a structural framework for high-grade iron ore deposits, in Proceedings Iron Ore 2015, pp 255–262 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A Grigg, L Hackett

Alcoa operates two bauxite mines at Huntly and Willowdale, located within the jarrah forest south-east of Perth in Western Australia. Ore reserves are shallow but extensive, and mining pits averaging around 20 ha in size are distributed across a mining region in a mosaic pattern, linked to a centrally-located crusher by a radiating network of haulroads. A mining or crusher region is defined partly in terms of economic haul distances, and new regions are opened once the current regions’ reserves have been mined. Since commencing in 1973, the Huntly mine has constructed and progressively closed three previous mining regions and is presently in a transition from the fourth and current region of McCoy to the new region of Myara. At present rates of production, approximately 450 ha is cleared, mined and rehabilitated each year.The value of topsoil in returning a diverse mix of native jarrah forest plant species and supplying nutrients, organic matter and soil biota to rehabilitated areas has long been recognised. Managing the topsoil resource is therefore a critical element in the success of rehabilitation outcomes, but the distribution and dynamic nature of mining operations pose significant planning and logistical challenges. The regionalised approach to mining at Huntly also presents a range of issues for what are, in effect, soil management plans for episodic mine closure. The nature of mining and rehabilitation operations are described, together with the planning processes that Alcoa follows to quantify, track and report on soil movement. A case study of the Huntly mine demonstrates that an integrated operational and life-of-mine planning process is essential for successful and cost-effective mine rehabilitation.CITATION:Hackett, L and Grigg, A, 2014. Topsoil management for long-term mine operation and closure – a case study from Alcoa's bauxite mining operations in south-west Australia, in Proceedings Life-of-Mine 2014 , pp 609–614 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By B Levasseur, C Olsen, E Ghasemian Langeroudi, F Larachi, F Safizadeh, C Gagnon

Gold recovery by the cyanidation process is often accompanied by the leaching of other species. This leads to the depletion of the level of free cyanide and oxygen available for gold cyanidation. The largest proportion of the consumed cyanide is diverted by the cyanicides (eg S, Cu, Zn, Fe, etc) into non-valuable complexes.COREMÆs Extractive Metallurgy team has been conducting a research program on the improvement of the gold cyanidation process. As a part of this program, the current study aims to investigate the effect of certain operating parameters on the reactions involved during preoxidation and cyanidation. Flotation tailings and single mineral samples such as pyrite, sphalerite and chalcopyrite, along with their different combinations, were analysed to highlight the influence of ore mineralogy on the operating conditions. The effects of different kinds of oxidants (oxygen, hydrogen peroxide, ferricyanide and ozone) and chemical additives (ammonium sulfate) were investigated.Experiments conducted in alkaline solutions reveal that mineralogy is a key parameter since pyrite, chalcopyrite and sphalerite react quite differently during preoxidation and cyanidation. A significant increase in sulfur dissolution, especially on pyrite, was observed by applying preoxidation. H2O2 preoxidation showed a positive effect on increasing sulfate formation, a desirable by-product from the cyanide consumption point of view. Preoxidation of synthetic ores with ferricyanide resulted in boosting thiosulfate formation. Tests conducted on flotation tailings from a polymetallic mine revealed that a short preoxidation increases the dissolution of the ore leading to higher gold recovery and lower cyanide consumption. Regarding the formation of thiocyanate, the most undesirable by-product of the cyanidation, ferricyanide and ozone were found particularly efficient to hinder their formation. Finally, the addition of ammonium sulfate during the cyanidation process showed some promising results in terms of both gold dissolution and cyanide consumption.CITATION:Ghasemian Langeroudi, E, Levasseur, B, Safizadeh, F, Olsen, C, Larachi, F and Gagnon, C, 2013. Optimisation of operating parameters for cyanidation of sulfide-bearing gold flotation tailings in order to prevent the impact of cyanicides, in Proceedings World Gold 2013 , pp 111-120 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By P M. Cepuritis

In hard rock mining, large-scale bulk mining methods such as block or panel caving (BC/PC) and sublevel caving (SLC) typically generate significant surface deformations such as subsidence. Surface deformations need to be considered in the project evaluation and planning stages of cave mines, for example, planning and location of critical underground mine planning infrastructure such as portals, haulage and vent shafts, access roads, or potential damage to existing infrastructure, changes to surface water management, waste dump, stockpile and tailings dam stability, and environmental impacts. Assessing the impact and risks associated with subsidence is a key component in robust mine planning and operations management.

Nov 29, 2022

By J Berg, M Hahn, R Winkel

Imaging sensor systems designed for the mining and minerals industry incorporate different physical measurement technologies that can be used to detect the machine environment, such as laser, ultrasonic/sonar, video and RF-sensors. The underlying physical measurement principles cannot be employed in most applications near the face without regular maintenance due to the harsh environmental conditions like dust, dirt or moisture. However, that is the area, where imaging sensors are most valuable to the machine operator. In the domain of 2D radar sensors these have been either restricted by the angular coverage area or by limited adaptability of signal processing algorithms. The unique full digital solid state design will establish a generation step in mining applications.In order to fill this gap of terrain imaging sensors, the Institute for Mining and Metallurgy Machinery (IMR) of the RWTH Aachen University, in cooperation with the radar company indurad, developed an imaging sensor based on radar technology employing the digital beam forming (DBF) concept. Through multiple transmitting and receiving antennas the sensor delivers high accuracy range and angular information. Using adaptive digital signal processing with multiple imaging algorithms and target detection routines, data of the surrounding environment can be used to enable automation functions in mining.A comprehensive range of radar scans in different environments have been evaluated and benchmarked by using laser scanners. Accuracy measurements in range and angular direction have shown minimal differences. Experimental measurements have been performed at slopes, on conveyor belts and hot cement clinker silos. The experimental system uses a frequency modulated continuous wave (FMCW) front-end combined with a processing unit for signal analysis and target detection.

Sep 26, 2011

By N McIntyre, R Trancoso, N Bulovic

Mining is essential for facilitating human development particularly as demand for critical minerals grows. However, over the mine life cycle, the environment is permanently changed. Once mining ceases, mine-affected land can leave significant legacy issues on the surrounding environment if not managed. Therefore, mine closure planning is critical. Mine closure occurs over large scales often with the aim of recreating resilient ecosystems over mined landscapes with mitigated negative impacts. The natural state of the landscape and the environmental risks over planning time-scales are largely driven by climate. Climate change is expected to impact different parts of the post-mining landscape, from stable landform design (soil erosion mitigation) to revegetation efforts and pit lake management. Consequently, mine closure plans may need to account for a non-stationary and uncertain future climate, that may be both different to the current climate and evolve during the mine life and post-closure. Here a new data-based approach is presented for incorporating climate change projections in mine closure planning, based on the recently released Coupled Model Intercomparison Project phase 6 (CMIP6) climate data used in the latest Intergovernmental Panel on Climate Change (IPCC) assessment report. The approach: (i) characterises closure-related attributes of the future climate, and (ii) identifies the amount (and direction) of change expected to occur, and its uncertainty, focusing on five metrics for demonstrative purposes and initially describing changes in erosive potential below. This provides information on the type of future environment (ie the changing baseline) that mine closure should plan towards, and identifies rehabilitation options that may be susceptible to increased risks from climate change.

Aug 2, 2023

By M Zoorabadi, Y Zhang, D Bringemeier, S Nicoll, N Kerr

Lihir operations of Newcrest Mining Limited (NML) are on Lihir Island (PNG) which is located approximately 900 km north-north-east of the national capital Port Moresby. The mine is located within the Luise Caldera of the Luise Volcano which is located on the east coast of the island. The caldera is an extinct volcanic crater that is geothermally active. Volcanic activity on Lihir Island is limited to remnant hydrothermal venting in the Luise Caldera in the form of hot springs and fumaroles. Steam and gas (including H2S) naturally discharge within the pit area and along the Kapit beach and near shore region. The hydrothermal reservoir temperatures can reach 100°C at the water table and exceed 200°C at depth. Newcrest maintains a Geo-hazard Management Plan to identify and manage the various geotechnical and geothermal hazards on-site. The major geothermal hazard to mining at Lihir is the occurrence of geothermal outbursts, which have occurred in the past with varying intensities and caused two ‘near misses’, production delays and material losses.

Nov 29, 2022

By Brenchley R

Partitioning behaviour studies for -particles in the 250 to 1,000 micron size range at. the Curragh coal preparation plant are presented. Plant surveys were conducted to compare the partitioning efficiencies of dense medium cyclones and froth flotation. The aim was to assess the potential for improving yield of coal by directing more of the top size of flotation feed material to dense medium cyclones. ovel mass balancing and model fitting NI procedures were used. While flotation offers high yield of low ash particles smaller than 500 microns, dense medium cyclone rejection .of high ash particles larger than 250 microns is superior. These strengths of the two processes are turned to good advantage by the use or desliming sieve bends which tend to perform some density separation on the'size fractions of interest, directing lower ash material to froth flotation than to the dense medium cyclones.

Jan 1, 1987

By H Asche

The proposed Rockwater Power Project is a hydropower development on the Waitaki River in the South Island of New Zealand. The proposed development will have an installed capacity of 250 MW with a peak flow capacity of 260 m3/s. The project commences at Lake Waitaki and extends some 35 km downstream on the north bank to a surface power station at Stonewall. Flow is returned to the Waitaki River via an outfall channel.The tunnelling for the project is through Greywacke, which comprises Permian and Triassic age marine sediments that are well indurated and weakly metamorphosed. The rock mass is jointed and sheared and there are frequent faults, which range up to hundreds of metres in width. Three 12 m diameter tunnel boring machines (TBMs) are proposed to excavate the 35 km long tunnel.The paper describes the development of the tunnel alignment, rock mass classification, design of the support, rock and hydraulic loads, support installation options and construction sequencing.The alternatives of rock bolts and shotcrete and segmental lining were both investigated and are discussed. Support using rock bolts and shotcrete offers the potential of rapid construction with minimum support cost when the ground conditions are good, but delays due to support installation increases with deteriorating ground conditions. In contrast, segmentally lined tunnels offer greater certainty in cycle time with reduced program risk. Both options are described and discussed.The horizontal alignment is affected by the presence of major fault zones, which are either avoided, or pretreated by driving conventional tunnels through in advance of the TBM delivery, topographical constraints with the rugged topography and operational hydraulic constraints. Construction requirements, future power station operation and the minimisation of leakage from the tunnel have all impacted on the vertical alignment.The number and sequencing of TBMs to be used is discussed in terms of program time and risk minimisation.

Mar 8, 2011

This paper examines the complex interplay of deposit characteristics, mining plans, tailings disposal techniques and rehabilitation requirements on planning for mineral sands operations. All component parts of this mining cycle are interdependent and cannot be evaluated in isolation when optimising a mineral sands operation. This is most evident when projects are large-scale or involve resources that contain complexities such as high slimes content, consolidated hard band materials, acid forming materials and radioactive materials. Projects located in environmentally sensitive areas add further to the need for more stringent planning. This paper describes the analysis techniques adopted by Hatch to evaluate mining and tailings placement options for a dredging and floating concentrator system. The principles and methods used in the analysis are applicable to any mining system involving the complexities listed above. The focus of this paper is on the reconstitution of mined material as tailings and the impact of this process on mining schedules and tailings construction and placement options.

Jan 1, 2001

By B Bonfils, P Lois Morales, C Evans

One of the main challenges for current and future mining and processing methodologies is to understand the characteristics of the rock so that its behaviour in one or more parts of the mining process chain can be predicted. Features such as rock texture, mineralogy or border complexity between minerals control how the rock behaves from the processing plant through to the final products, including tailings disposal and thus can affect the feasibility of the project from technical, economic and environmental impact perspectives. Understanding how the mineralogy and texture of rock affect its behaviour in mineral processing is a demanding area of research and is essential knowledge in predicting the processability of complex ores in different stages. This study aims to demonstrate that different types of relevant information can be extracted from a range of currently available analytical methods. However, this information can be used in a complementary way for building a more comprehensive rock characterisation at the microscale and better-predicting ore processing characteristics from the intact rock through to tailing disposal. CITATION: Lois Morales, P, Evans, C and Bonfils, B, 2018. Multisource rock characterisation at microscale for a better understanding of processing characteristics, in Proceedings Complex Orebodies Conference 2018, pp 44–48 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By T Takayama, M Matsumura, Y Konno

The steel industry accounts for 14 per cent of domestic CO2 emission in Japan, and iron ore sintering process occupies approximately three per cent. While Fe content in iron ore is gradually decreasing. So, the amount of concentrated iron ore will increase in the future. We have focused on magnetite concentrate as sinter materials, because magnetite can be easily magnetically beneficiated. However, it is experienced that blending magnetite ore resulted in increasing Fe2+ component in the iron ore sinter, which results in lower reducibility. Therefore, promoting the oxidation reaction from magnetite to hematite in the sintering process is countermeasure for reducibility. In addition, this promotion causes increase of oxidation heat, which results in high sinter strength and reduction of coke. It is assumed that the oxidation of magnetite tends to proceed in the cooling stage, where the oxygen partial pressure increases after the combustion of fine coke, but there are few studies on the effect of heat profile, especially cooling path. The purpose of this study is to design the effective sintering heat profile to promote oxidation of magnetite ore, especially, to investigate the effect of cooling path on sintered ore microstructure. In this study, magnetite ore and magnetite reagent were respectively mixed with calcium carbonate reagent. Then the mixed samples were pressed and formed into cylindrical tablets for simulating the adhesive layer of a pseudo particle. Through examining influence of maximum temperature and cooking rate on oxidation reaction of magnetite, we confirmed that the oxidation reaction of magnetite is suppressed at above 1350°C for maximum temperature, compared to 1300°C. Sintering at lower temperature is desirable because hematite is stable below 1350°C in the Fe2O3-CaO phase diagram.

Nov 8, 2021

The last decade of national water reform implementation has improved the availability and efficiency of water source allocation in Western Australia. However, it is critical to recognise that the concurrent mining boom witnessed the approach of full water allocation limits, and increasing trends in mineral processing, water infrastructure costs, and wastewater management costs. Water supplies are commonly viewed as absolutely critical to project feasibility in mining, industrial and energy generation projects, even if considered 'non-core business'.   An increasing density of mining projects and industrial estates in Western Australia (WA) creates an opportunity for water infrastructure cost sharing and synergies. The WA government and its agencies have given preliminary consideration to the establishment of independent water utilities in the goldfields (Kalgoorlie), the Pilbara, and Collie regions, and in the Kwinana Industrial Area. The impending Oakajee industrial area and Mid West regional development, and Anketell port in the East Pilbara, could also be considered for common non-municipal water supplies.   The critical issue of apparent commercial risk due to the large scale of water demands and the low customer numbers in the minerals sector relative to other water markets is expected to mandate government partnership in any non-municipal water utility ownership. The commercial feasibility risk is observed as a risk to water supply security for potential mining and industrial customers. Absence of proper water infrastructure planning and governance has the potential to create infrastructure access issues as observed for Pilbara rail developments under the Trade Practices Act 1974.   Other aspects of water cycle management which could be addressed by a non-municipal utility include resumption of mine dewatering water (required changes to WA legislation that are progressing) and consolidated wastewater management for maximising synergy or reuse opportunities and minimising cumulative environmental impacts.   Address of water infrastructure planning for non-municipal water demands must cover commercial and environmental sustainability outcomes to successfully progress minerals sector growth in the State.

Jun 1, 2010

In this paper a quantitative deterministic risk modelling approach (Quadrim) is introduced. The mathematical framework and equations for quantifying uncertainty within and aggregating across value chain nodes from error propagation techniques is proposed and discussed. A case study and worked examples, based on a hypothetical mine are then presented. This illustrates how uncertainty from the mining and economic value chains can be handled in a typical net cash flow calculation, and how this can be translated to a risk model. It is then illustrated that current valuation techniques do not just result in an information gap for decision makers. Traditional approaches such as discounted cash flow (DCF) analysis and truck and shovel productivity analysis, which do not take into account uncertainty in input values, can result in potential bias in estimates such as net present value (NPV) or equipment hours

Sep 26, 2011

By A Geldenhuis, M Hagger, J Maree

Disposal of mine water is a worldwide problem occurring in the coal and gold as well in the metal ore mining areas. Since southern Africa is a (semi) arid region, mining effluents should be treated to qualities such that they can be used for agricultural purposes or that they can be discharged in river system. Studies have shown that partly treated acid mine water can be used for irrigation. A copper mine in Botswana plans to use 5 M/d of treated mine effluent for the irrigation of agricultural product. The results of this study showed that when applying the biological sulfate removal technology the produced sulfide precipitated the metals in the mine effluent, such as nickel, Zn and Mn, to metal sulfide (MeS).

Jan 1, 2003

By S Januszewski and, G Dirom, D Christensen

Four field test plots were constructed in 1998 on a sloped waste rock surface at the Myra Falls Operations of Boliden Westmin (Canada) Limited to evaluate hydraulic performance of alternate cover system designs. The field test plot cover systems were designed to control oxygen ingress and water infiltration to the underlying waste rock while providing a medium for a grass and legume vegetation cover. The test plots consisted of a bare waste rock surface (control plot), and three additional plots consisting of native compacted till placed directly on the waste rock surface, overlain by non-compacted till. Two of the test plots included a compacted till layer ameliorated with flyash and bentonite, respectively, to improve moisture retention and reduce permeability. The third test plot consisted of a compacted layer of native till overlain by non-compacted till. A performance monitoring system was installed in each test plot to evaluate net percolation and oxygen ingress to the underlying waste rock. In addition, each test plot has profiles of matric suction, water content, and temperature sensors installed at up-slope and down slope locations. A review of four years of monitoring data shows that the compacted till/bentonite cover system has been most successful in limiting the infiltration of meteoric waters and oxygen ingress to the underlying waste rock material. The compacted till/flyash and compacted till cover systems have produced similar net percolation results and neither have functioned well in maintaining an oxygen ingress layer throughout the year. The amelioration of bentonite with till to produce a compacted barrier layer shows promise in reducing water and oxygen ingress at the MFO site, while the incorporation of flyash with the till did not result in a significant increase in performance. The field performance data clearly demonstrates the need for developing field trials prior to full-scale construction, as opposed to relying solely on an un-calibrated numerical modelling to design the full-scale cover system.

Jan 1, 2003