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By S Schwarz, D Alexander

The mining industry, and in fact the world, has undergone significant changes in the past five to ten years, ranging from the metals boom, the global financial crisis and the rise and fall of national economies, to name just a few. There has been a focus on sustainable development for projects and operations in the mining industry, mainly pushed onto the industry by communities, governments and other agencies. While sustainable development and operation is a worthy priority for mining operations, discussions with mining industry personnel (with a strong slant on the mineral processing perspective) have shown other issues have surpassed the typical issues of water resources, energy availability and the environment. These include staff turnover and skills shortages, extracting metal from more complex orebodies and the uptake of new step-change technology.A number of key operating mineral processing personnel were interviewed to determine their perspective on the current issues facing the mining industry. This paper details the findings of this survey and highlights some of the topics that have been identified as the top issues from a mineral processing perspective.CITATION:Schwarz, S and Alexander, D, 2012. Current issues in the mining industry - From the operational mineral processorÆs perspective, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 369-372 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By C Artica

Two quantitative methods for Mineral Resource classification have been applied to a copper skarn deposit beneath a large open pit that is mining a world-class porphyry complex. A drill hole spacing study (DHSS) using the single block kriging method (SBK) and a conditional simulation method (CS) were applied to the skarn deposit and the results compared. Inputs to both processes included the proposed mining rate and stope designs to estimate the likelihood of achieving grade and metal production targets. Mineral Resource classification of the deposit considers the relative precision of tons, grade and metal predictions over quarterly and annual production periods. These relative precision estimates are calculated at 90 per cent confidence interval (CI). The SBK method represented the production period as a single large block. Kriging estimates were performed in the large block for various synthetic drill hole grids, and the estimation errors derived. The error was assumed to be normally distributed due to the large block size and quantity of samples, allowing CIs to be deduced. The CS method followed a conventional sequential Gaussian simulation workflow where grades were simulated with a 5 ft × 5 ft × 5 ft grid node spacing inside mineralisation domains. Each realisation was then averaged up to monthly production volumes represented by a combination of designed stopes, and the coefficient of variation (CV) for the averaged grade was calculated. CI on the relative precision of grade predictions were then deduced from the CVs. The two methods produced similar results; despite being calculated independently. CS results were used to report uncertainty in the proposed life-of-mine plan and highlight areas for additional drilling. SBK results were used as the basis for Mineral Resource classification as this method has been previously applied to the skarn deposit.

May 24, 2023

By M Scoble

This paper addresses the importance of collaborative approaches to resolving future mining challenges. It attempts to provide some insight into understanding the theory, measurement, mapping and management of collaboration. This is related to the design and planning for successful research and educational initiatives. Reference is made to Canadian and global case studies and personal experiences.

Nov 22, 2011

By P Woodward, T Ly, N Muhamad

OZ Minerals' Prominent Hill copper-gold concentrator is located 650 km north-west of Adelaide in the Gawler Craton of South Australia. The concentrator was built in 2008 and commenced commercial production in early 2009. The Prominent Hill concentrator is comprised of a conventional grinding and flotation processing plant with a design capacity of 8 Mtpa. The flotation circuit includes six rougher cells, an IsaMill for regrinding the rougher concentrate and a Jameson cell preceding the three stage conventional cell cleaner circuit.Since its commissioning, the Prominent Hill flotation circuit has been the focus of a series of projects aimed at continual performance improvement. This has been achieved by a systematic approach of project identification, evaluation and implementation which has led to a progressive improvement in flotation performance. Innovations that have been successfully implemented include aspects of cell design and operation, and reagent suite optimisation.Improvements to the mechanical cells initially focused on the installation of a modified rotor-stator design in the rougher circuit, as recommended by Outotec. Isolated cells were fitted with this technology and proven to provide a benefit for copper recovery before the design was trialled in subsequent cells along the bank. Based on this success, further modifications were made to other aspects of the rougher and cleaner cells.Laboratory trials conducted at Prominent Hill involve a screening process identifying potential reagents from a list of products, which are then rigorously tested in the laboratory before one is selected for trial in the concentrator. Where these reagents have demonstrated a statistical improvement in performance they have typically been incorporated permanently into the flotation circuit. This paper discusses the process of continual improvement at the Prominent Hill flotation circuit and the optimisation achieved by the implementation of key initiatives.CITATION:Woodward, P, Muhamad, N and Ly, T, 2013. Optimisation of the Prominent Hill flotation circuit, in Proceedings MetPlant 2013 , pp 431-444 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By G Williams

Somewhat to the surprise of many heavy mineral sands (TiO2 and zircon) producers, there are important geological structures within their typical placers and aeolian sands deposits that affect plant metallurgical performance. After many years of operations, even experienced producers have encountered unexpected changes in production, product quality and recovery. After looking in all the obvious (but wrong) places, it is recognised that the mine has advanced into ore with different separation characteristics. Metallurgical process response can vary significantly between ore sourced from different geological domains. The mineral characteristics that are exploited for effective separation may be associated with differences in the depositional environment, or be post-depositional in origin. Surface coatings that interfere with electrostatic separation might be associated with paleo-water table movements. Major storm events in the deposition history can also leave distorted mineral assemblage through stranded formations or incisions in older deposits.Apart from the influence on capital and operating costs, geometallurgical variances add another dimension to orebody modelling. Each domain could have specific recovery, mineral assemblage and product quality values to be considered in the value model. Project success is often directly dependent on understanding the geometallurgy of the resource. Tailoring the exploration and early process flow sheet development programs to account for such variances should be standard practice. Such practices have had a chequered history in the mineral sands industry, with sophisticated processes having been developed, only to be shelved for ‘economic’ reasons, and then once again ‘discovered’ when problems re-emerge.It is clear that knowledge gained through a higher level understanding of the changing mineral separation characteristics and advance warning of mineral behavioural differences can mean the difference between lost recoveries and disappointed customers or well timed capital plans and maximised revenues.

Oct 5, 2011

By N Redwood, N Fowkes, A Bassom, S Durkin

"It is well known that from time-to-time a vehicle will interact with a bund or windrow and often the barrier is insufficient to safely arrest that vehicle. The result of such an incident is often catastrophic. Regulations around the requirement for edge protection near pit edges vary between jurisdictions. Generally in Australia regulations tend to be around placing the responsibility on the mine operator to provide ‘adequate’ or ‘appropriate’ edge protection. Guidelines often place a minimum height of bund at between half and two-thirds the diameter of the largest tyre on-site.Safescape has identified the opportunity to improve safety in open pit edge protection and is currently developing the Edge Protector (EP) product. The EP is designed to create a vertical front face to a conventional broken rock safety bund. The fundamental premise of the product is that by creating a vertical front face to the bund, trucks cannot easily drive up over the bund and instead have to push through the rock to get to the other side.In addition to providing a safer system for arresting vehicles, the vertical front face also means that extra space is made available in the haul road. This can either be used to facilitate larger trucks or when designing a new mine, with an increase in overall pit slope.This paper outlines the research and development of a new edge protection product. Discussion will include project objectives, economic incentive for mines to apply the system, mathematical analysis of the truck/bund interaction and physical testing of the product.Citation:Durkin, S, Fowkes, N, Redwood, N and Bassom, A, 2016. Innovative Approach to Open Pit Edge Protection, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 138–149 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By J Simpson, M Johnston

Recently Mount Isa Mines undertook a study to review the lead-zinc orebodies to extent of resource and reserves and determine the new life-of-mine schedule, as the Mount Isa and Hilton orebodies had not be reviewed for many years. Also, the recovered value of the Mount Isa, Hilton and George Fisher orebodies had been increased by major performance improvements in the lead-zinc concentrator. The Mount Isa Lead-Zinc concentrator processes fine-grained lead-zinc ore from the Mount Isa, Hilton and George Fisher orebodies. These orebodies have varying levels of pyrite and large variation in the grain size and texture of the galena, sphalerite and pyrite. This variation has a large effect on the recovery of the lead and zinc in the concentrator. Some ores achieve 90 per cent recovery at target grades, yet other ores are unable to achieve æsaleableÆ concentrate grade, with no metal being recovered to concentrate and therefore effectively losing the contained metal to the final tailings. Models were created to predict the metallurgical performance of these orebodies, to better reflect the variation that occurs. These improved metallurgical models and economic data allowed the determination of the Net Smelter Return (NSR) for each block in the geological block model. This NSR is the return to MIM of the metals contained in concentrate. The NSR was used as the cut-off grade criteria when determining the value of the ore. This formed the basis of the lead-zinc life-of-mine schedule and the optimisation of the lead-zinc business.

Jan 1, 2003

By A Kleinitz, J Halilovic, K Trappitt

Mine operators use grade control to determine the destination of each block of material in the mine. In polymetallic mines, grades are best expressed in dollars: the Net Smelter Return, NSR, per tonne. To estimate NSRs, geologists working on grade control develop models for each geometallurgical domain in the mine. These models may incorporate observations on the mineralogy and grain sizes of the material being examined. The site’s mill operators contribute to the models by providing geologists with statistical analyses that relate assay results and mineralogical compositions to metallurgical parameters, such as the rates of recovery of each economic metal to each of the concentrates produced, and the compositions of those concentrates. The team responsible for sales and marketing of the site’s products contributes to the NSR models by providing details of the costs of shipping concentrates to smelters and refineries; and by providing figures that are specified in the smelter contracts, such as the payability of the metals in each concentrate and the fees charged by the smelter. The mill operators also provide, for the NSR models, equations to estimate the rates of recovery of deleterious materials to each concentrate. Deleterious materials comprise mostly halogens and amphoteric elements, both of which reduce the efficiency of smelters. Furthermore, deleterious materials such as antimony and arsenic may be poisonous to people and to the environment. The sales and marketing team provide specifics of the penalties that smelters impose upon deleterious materials. These penalties may reduce NSRs by tens of percent, possibly to levels below the cut-off grade. Thus, in the blocks that are subject to grade control, mine geologists monitor not only the concentrations of economic metals, but also the presence and abundance of deleterious materials. The preparation and maintenance of models, to estimate NSRs and to assess changes in the levels of potentially toxic materials to be mined, requires close and continuing consultation between corporate departments. There must be strong communication of mine geologists with the mill operators; with the people who market the mine’s concentrates; and, should there be a risk of encountering toxic levels of deleterious materials, with the mine’s health, safety and environmental officers. This co-operation could require radical changes in the structure of many organisations. However, experience suggests that such changes can significantly improve the profitability of a mine.

Mar 22, 2022

By J Furtney, W Fu, D Nutakor, A Brose

Rock blasting outcomes are often a shared responsibility of both the mine operations group and the mine geotechnical group. From an operational logistics and planning perspective, blasting concerns include optimal fragmentation for subsequent crushing, ensuring the blast is energetic enough to allow easy digging, and understanding the effect of muck from a previous blast on the current blast. From a geotechnical perspective, wall damage and catch bench capacity are the primary concerns. Other concerns for both teams include damage to mine infrastructure by fly rock or blast-induced vibrations, and the stability of open stopes under the pit. This work presents two blast modelling applications (or ‘apps’). The basic app instantly gives fragmentation and wall damage predictions for a given generic blast design. The advanced app loads the current pit contours, reads the blast design from a spreadsheet, and calculates the expected vibration magnitude and peak frequency. The apps have been developed specifically for the Rio Tinto Borates and Lithium Mine in California and are used to support blast design between the operations group and geotechnical group. The basic app instantly gives fragmentation and vibration predictions given a blast design by combining the Kuz-Ram fragmentation model with the scaled distance model for vibrations. The advanced app uses the signature hole method. Blasting outcomes at the mine have improved since using the apps.

Jun 22, 2022

The Mt Keith Mining Alliance operates a fleet of large capacity hydraulic face shovels and more than 40 X 240 t capacity haul trucks to deliver annual production in excess of 40 Mbcm per annum. The Mt Keith Nickel mine is currently operating at a depth to 300 m below surface with a planned final depth of the order of 500 m. As is the case with any large open pit managing the health of the workforce on continuous shift operations is of critical importance to achieving outstanding safety and production outcomes. Fatigue management at Mt Keith is effectively managed by the personnel operating the mining equipment, with assistance and understanding of the management team and supervisors. The program has been driven through the introduction of Fatigue Champions and a comprehensive management plan that includes education, individual health plans and the use of new technologies. Mt Keith has been instrumental in trialling new technology which assists in monitoring fatigue in operations personnel. Insight into these developments is provided in the context of the overall fatigue management plan. The field trials of the OptAlert(TM) system and how it assists in measuring fatigue is explained. The implications for individual operators and the context for a fleet wide approach to fatigue management is also discussed. Mt Keith has recently completed the second phase of trials with the result that this new and exciting technology is being considered for adoption globally across BHP BillitonÆs open pit mining operations.

Jan 1, 2007

By A Purwodihardjo

Evaluation of the construction method used for the pedestrian underpass construction at Ipswich Road, Brisbane, Australia is presented in this paper. The pedestrian underpass was constructed through the existing railway embankment between Harrogate and O’Keefe Streets on the eastern side of Ipswich Road. This underpass construction is part of the CLEM7 tunnel project (formerly known as the North-South Bypass Tunnel) which is the longest toll road in Australia at a total length of 6.8 km. The jacked box construction technique was initially identified as a preferred option during the tender and concept design phases. However at the final design stage, the cut and cover technique was selected as this method can reduce the construction time and cost significantly. The design and construction teams effectively managed the challenges, complexities and risks associated with undertaking cut and cover tunnel through the existing heavily utilised rail embankment. The on-site construction time for the underpass using the cut and cover technique was reduced to less than 42 hours.

Mar 8, 2011

By G Cooper

The Société Nationale Industriel et Minière (SNIM) is expanding its ore and concentrate production capacity in Mauritania, West Africa. This government-controlled mining company has been in production since 1963 and currently exports some 12 Mt/a.SNIM is presently doubling its magnetite concentrate production at the Guelb el Rhein mine. An existing processing line will have a second parallel production line of 4 Mt/a added. The mine is located some 600 km inland from the Atlantic coast in the heart of the Sahara Desert.The metallurgy of the ore is reasonably straightforward. It is a magnetite banded iron formation that is amenable to magnetic separation. While the existing plant uses semi-autogenous grinding and dry magnetic separation, the new processing line will use HPGRs, dry magnetic separation, and a wet milling and magnetic separation circuit for treating middlings.The process choices refl ect the scarcity of water in the region, the high cost of locally generated power and the operating experience and preferences of SNIM. Dust control in the desert environment has been a particular challenge.The metallurgical design aspects as well as the infl uence of the environmental and commercial aspects of the project are presented.

Jul 11, 2011

By H Thanasekaran, M J. Mankosa, J N. Kohmuench, G H. Luttrell

"Fluidised-bed flotation has been demonstrated over the last 16 years as an effective method for improving the flotation recovery of coarse particles. This technology has been successfully deployed into the industrial mineral sector with multiple installations within phosphate beneficiation plants and potash mills. Due to the minimal mineral surface expression required when utilising this technology, more recent studies have centred on the applicability of using this HydroFloat™ technology for the recovery of coarse sulfides and base metals. Multiple approaches have been investigated to determine the best means for implementing this novel coarse particle flotation system into both existing and new plant circuitry. These include the treatment of tailings to recover values that have been lost using conventional technologies and also the direct treatment of a coarse feed, either within the grinding circuit or by use of a separate split-feed flotation approach. Recent applications of the technology will be presented along with data generated from several test campaigns and ongoing research investigations. The benefits of properly applying this technology, such as reduced power consumption and increased mill capacity will be discussed.Citation:Kohmuench, J N, Thanasekaran, H, Mankosa, M J and Luttrell, G H, 2016. The Impact of Fluidised-bed Flotation for Treating Coarse Sulfides, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 105–112 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By M Bouare, C Holland, K N’Diaye

Two adjacent open pits in Mali hosted by deeply weathered saprolitic materials were mined consecutively over the course of approximately 12 months. During excavation, both pits experienced significant displacement and tension cracking as the result of deeper than expected depth of weathering coupled with relatively steep slope angles and significant groundwater. In response, geotechnical and operations teams overcame numerous monitoring challenges with prisms and radar to develop a simple and effective monitoring system coupled to a Trigger Action Response Plan (TARP) which enabled continued safe operations while reducing ore loss. Observations of previous slope performance of these two pits allowed for greater confidence in empirical failure runout calculations that was used to specify the standoff widths for the exclusion zones in the pit. Back analysis of the slope as-built performance after the first indications of slope distress was also conducted. The back analysis was used to confirm rock mass parameters for modelling while being utilised as a reality check for the stability analysis. The stability analysis indicated that leaving a large step-out or buttress would not prevent the displacement, resulting in some ore being sacrificed to ensure the safety of personnel. Key learnings from this experience highlight the importance of: • up-to-date geological interpretation of the depth of weathering • ensuring slope design guidance is reviewed and updated as latest information (ie geology and monitoring) is received • having multiple complementary slope monitoring methods to ensure redundancy • ensuring visual observations and as-built performance are utilised as a reality check to provide greater confidence in stability analysis and design guidance.

Jun 22, 2022

By D Wimpenny

Underground infrastructure is often a critical component of transportation and utility schemes. It is characterised by long design lives with limited access for inspection and maintenance. The exposure environment can be difficult to assess since it will often vary substantially between different locations in the same facility and with time during construction and in service. In addition, the specific demands placed upon underground infrastructure are not well covered by the exposure classes and other guidance given within current codes of practice. When problems occur they can be difficult to rectify and involve significant disruption.Given these substantial risks the prudent designer may adopt a systematic ‘durability planning’ approach which:· defines the environment and principal deterioration mechanisms for the various elements and construction materials,· predicts the design life for alternative durability enhancement options, and· recommends associated measures to be adopted during construction and in service.This paper describes the development of durability planning within Halcrow, giving examples of its use from its first implementation on tunnels under the Suez Canal in 1993 to recent projects in the Middle East and Australia. It seeks to demystify the process, identify shortcomings and speculate on its future development within the civil and mining sectors.

Mar 8, 2011

By R Miller

The enrichment of magnetite to haematite and haematite-goethite leads to a coincident magnetic low and gravity high within the banded iron formation. Palaeochannel deposits of pisolitic limonite can be expected to provide a relative magnetic high and gravity low in a sinuous geometry. Detrital iron deposits of conglomerate, scree or ‘canga’ might have indistinct magnetic response but will usually have a relative gravity high.These signatures provide clear discriminators detectable by a joint gravity and magnetic survey.The combination of airborne gravity gradiometry and magnetometry is particularly powerful in detecting and discriminating targets, as well as mapping lithologies and structure, across a wide variety of iron ore deposit styles. It provides detection capabilities in a platform capable of rapid, complete coverage with minimal access issues. This approach has been used in FALCON™ airborne surveys for iron ore exploration in the Great Lakes, USA; the Middleback Ranges, South Australia; and the Hamersley Basin, Western Australia.The complex magnetic properties of iron formations (particularly remanence, anisotropy and depth of weathering) prevent this approach from being simple. The use of vector residual magnetic intensity (VRMI), calculated from the measured total magnetic intensity (TMI), assists by reducing the complexity due to the different directions of the remanent and induced magnetic fields.Estimations of the density to magnetisation ratio via the pseudo-lithology calculated from the VRMI and gravity gradients provide a useful method of capturing the discriminatory power of joint magnetic and gravity gradient data.

Jul 11, 2011

By M Andrew, D McTiffen, M Adams

A major Ventilation Upgrade Project commenced at the Fosterville Gold Mine (FGM) in 2017 to service the ongoing ventilation requirements of the underground mining operation. The project consists of three large diameter ventilation raises totalling 1100 metres, and new axial primary ventilation fans to upgrade the mine ventilation system. With a mining depth of 1200 metres and a thermal gradient of approximately 2.7 °C per 100 metres of depth, the completion of the Ventilation Upgrade Project is key to the ongoing success at FGM. The Ventilation Upgrade Project will allow continued mining, including high-grade gold deposits, lower in the mine where heat is increasing. Figure 1 below illustrates the underground workings at FGM, and provides a general view of the ventilation upgrade works to establish the new exhaust system from the lower workings to surface. Whilst raisebore pilot drilling the H4760 Return Air Rise (RAR) from surface to 395 metres, the raisebore drill string became stuck in the raisebore pilot hole at approximately 300 metres down hole, presenting a significant technical problem and delays to the project. This Case Study provides an overview of the recovery process undertaken at FGM including the recovery of the stuck drill string. The value of the stuck in-hole equipment, the investment in the shaft site preparation, the collar stabilisation, the underground development to the base of the ventilation raise, the surface footprint prepared for the Primary Fans construction and the limited available space on the site were all motivations to recover the raisebore drill sting and ultimately recover the ventilation raise location. More importantly, the long lead-time required should a new shaft location be the final solution, and the delay this would incur to the ventilation upgrade was unacceptable. Recovery of the drill string was not possible using the capability of the Contractor’s Raise Drill. An alternative method for freeing the drill string was required. A significant amount of engagement with industry was undertaken to seek out potential solutions and draw from the experience of others. All methodologies available were considered and assessed. Ultimately, after several attempts at freeing the raisebore drill string using various methodologies, Adams Drillers and Clear Cut Interventions were engaged to provide a turnkey recovery solution.

Mar 15, 2021

By R Wynn, R A. Pax, S Mann, B Cornish

The semi-autogenous grinding (SAG) mill at the MMG Century operation has failing load cells that are essential to the control strategy used to stabilise the mill. Currently, mill-bearing pressure is used as a proxy for the load cells, but it has been found to be a noisy signal and lacking in useful sensitivity. It is also prone to variations and drift due to temperature. After consideration of a number of options, a non-contact acoustic array has been installed around the SAG mill to provide a more stable proxy load signal as well as other information about the internal operation of the?mill.The installation consists of 12 microphones to provide some detail into the operational differences that occur during normal operations at the MMG Century SAG mill. This acoustic approach acknowledges that operational grinding mills emit significant acoustic emissions that are a consequence of the dynamic environment prevailing inside them.Previous studies have attributed the acoustic noise to a range of events that occur inside these mills (Pax, 2011; 2012). Consequently, non-contact acoustic determinations of in-mill behaviour can provide powerful insights into the operation of the primary comminution tumbling mills. By measuring key microphone signal attributes at different positions around a mill, a holistic picture of mill internal operation can be developed.This paper will describe the installation of the 12 microphones and discuss the use of the acoustic load signals as a proxy for failing load cells. It will also present data from new observations of internal mill dynamics and the results of implementation of control using these acoustic signals. Key to the control approach has been the development of a logically coherent picture of the processes inside the mill.CITATION:Pax, R A, Wynn, R, Mann, S and Cornish, B, 2014. Implementation of acoustic arrays for semi-autogenous grinding mill?operation, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 273–282 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By W Mahoney, F Clement, E Saraiva

Prefabricated waterproofing sheet membranes are extremely complicated to install in underground sections with complex geometries and, despite being already subjected to quality tests in the factory, the installed membrane often exhibits leakages due to different reasons. Main sources of leaks are the required high amount of welding seams and damages caused during installation of reinforcement, as well as overstretching and poorly installed secondary concrete linings. Also the design of the tunnel lining is strongly influenced and limited by the use of prefabricated waterproofing sheet membranes. The use of sprayed waterproofing membranes for more than a decade has contributed to durability and serviceability, as well as to increasing sustainability of tunnel linings. The presented sprayed waterproofing membrane MasterSeal 345 is an advantageous alternative to prefabricated waterproofing sheet membranes under typical tunnelling conditions, especially in geometrically complex areas, such as in lay-by niches, cross passages and crossover caverns, where installation of conventional waterproofing membranes is inherently difficult, and locating leaks is challenging. This membrane has been successfully used in underground projects with different waterproofing design concepts and under diverse hydro-geological and environmental conditions for over a decade. It provides tunnel designers with different options and optimisation for the design of the tunnel concrete lining. Additional advantages to owners, contractors and designers from the use of the sprayed membrane include flexibility in the design, increased productivity and flexibility in working programming, as well as improved logistics, resulting in significant program and cost savings and reduced long-term maintenance costs. This paper describes the key features of this sprayed waterproofing membrane, its application range and limitations, the waterproofing concept, design options and related benefits. Further, guidance for membrane application and quality control and a summary of two recent project references in the United Kingdom and in Switzerland are provided.CITATION:Saraiva, E, Clement, F and Mahoney, W, 2014. The use of sprayable waterproofing membranes in underground structures – concept, design options, benefits and limitations, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 323–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

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