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By N Herault

PT Freeport Indonesia recently completed preproduction development and construction of the Big Gossan underground copper and gold mine, located in the Ertsberg mining district of Papua, Indonesia. Production has commenced with an expected ramp-up to full production of 7000 tonnes per day in 2012. The Big Gossan utilises an open stoping mine method with paste backfill.In order to deliver ore to the mill, which sits in a valley above the ore deposit, an underground production shaft and hoisting facility was designed and constructed as the key component of ore haulage. The design and construction of the Big Gossan shaft posed many challenges to the project team. Available shaft design and construction expertise were limited as this was the first shaft of its kind in Indonesia and the project was undertaken during a time of high industry demand for new shaft systems. Construction resources were also limited due to the remote location and competition with existing, producing mines for these resources and skills. The project also taxed the ability of Freeport to provide services and resources to this as well as their other projects.Completion of the Big Gossan shaft was a milestone in PT Freeport Indonesia’s plan to fully transition ore production to the underground environment in this decade.This paper deals with the various challenges faced by PT Freeport Indonesia and shaft contractor, PT Redpath Indonesia, during the construction of the Big Gossan shaft and offers suggestions to improve future shaft projects of a similar nature.

Mar 21, 2011

By A Mackay

As a result of the explosion in the 512 panel at the Moura No 2 mine in 1994 the role of the ventilation officer (VO) to submit sealing plans (on behalf of the operator/underground mine manager) has become one of the key duties of the VO of an underground coal mine in Australia. The intent of a sealing plan is to document the controls used to manage the build up of flammable concentrations of gases, and for these controls to be reviewed by the industry regulators. These sealing plans have brought a large amount of focus onto the sealing process and served the industry well. The legislation does not define sealing, or when it begins, but throughout the industry typically sealing plans are submitted 30 days prior to the last seal being constructed. This practice appears to have originated from the Moura 512 panel being a standing bord and pillar panel and where the explosive gas mixture could only occur after it was sealed. However, since the Moura disaster the industry has become dominated by goafing style longwall mining. Goafing panels differ from standing bord and pillar panels in that they typically have an unventilated goaf that can potentially contain an explosive mixture from start-up. This was recently highlighted by the explosion and fire on Longwall No 1 Tailgate at the Blakefield South Mine in 2011. The author ponders whether the industry should revisit sealing plans to focus on the core hazard and define that sealing begins when flammable concentrations of gases are created. Although defining when mine sealing begins is the key outcome of this paper, the main point is that VOs and industry regulators need to clearly understand what can occur in the atmosphere of underground coal mines. CITATION:Mackay, A, 2013. A case for change - Defining mine sealing and understanding flammable mixtures during sealing, in Proceedings The Australian Mine Ventilation Conference , pp 307-310 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By S J. Henderson

Pumped co-disposal of coal processing waste was promoted in the 1990-2000s as a low-cost highperformance alternative to tailings dams. In particular it would avoid high up-front capital for rejects trucks and dam embankments, and would produce a combined waste deposit with better geotechnical properties than either coarse rejects or tailings. Overall, the promise was not delivered; in particular, upon discharge the waste segregated by size, and operators responded by moving the coarser waste to contain the finer waste. In consequence, not only did design analysis lag behind construction, but some of the initial expectations persisted with the result that analyses did not fully represent what was occurring on the ground. After more than twenty years inspecting, designing and tending Co-Disposal Areas (CDAs), it is apparent that they are essentially upstream constructed tailings dams with some more favourable aspects but also a few unique quirks. Although waste management technology has moved on somewhat, the high cost of changing CHPP waste circuits means that most mines with pumped codisposal will continue to discharge mixed waste slurry into CDAs. It is therefore worthwhile to share some lessons in the hope of promoting sounder design, operation and rehabilitation. These include: • Discharged waste does not form a homogeneous wholly competent deposit but instead comprises materials ranging from sandy gravel to silty clay with the distribution determined by movement of the discharge and decant structures; • CDAs circulate and contain a lot of water; • As a result of the first two points, some areas of the CDA comprise saturated fine waste that is no different from tailings and, like tailings, often behaves in an undrained manner; • Seepage is inevitable and desirable because strength improves as water is removed. However, stability is strongly impacted by pore pressures and in design these need to be rationally rather than optimistically considered; • As CDAs are built to about 40m or higher, strength-deformation characteristics of the foundation become more important; • Even if geomechanically stable, CDAs will need covers to prevent salts and acids from reaching the surface; and • Erosional stability of the cover material(s) will probably dictate maximum slopes for rehabilitation.

Jul 1, 2021

By R Lau

The fire safety design for road tunnels includes the following aspects: active systems, passive provisions and operational procedures. The active systems include the smoke control system, fire suppression system, detection system and fire fighter’s assistance systems. Passive provisions include escape passages, fire separation and fire resistance systems. The operational procedures refer to fire fighter access, reporting and alerts, evacuation processes and crowd control.Currently, these systems are typically designed by different designers or teams. These systems are intended to work together in a coordinated manner to provide the desired safety outcome. However, in practice, this is not always happening. The fire engineering process is supposed to bring together all these aspects and arrive at an integrated safety system. The fi re engineering process in practice is not integrating the design with the practice or reality and is thus arriving at less than desirably efficient safety systems.The example of design inputs shows how disconnected each system design basis is. The smoke control system design is based on the design fire size. The performance of the smoke control system is to achieve a smoke free environment for a defined space for a particular fire size – the design fire. The fire suppression system – most commonly sprinklers or deluge systems, is designed according to codes and to achieve a certain water discharge rate. The fire detection system is designed to detect temperature rise/rate of rise and perhaps density of smoke. Fire separation is determined to provide a certain period of service – mostly for structural elements. Escape route size and location is determined mostly by code compliance. Evacuation procedures are determined by Authority operational requirements rather than human behaviour.To arrive at an integrated fire safety system, the design basis and performances must be coordinated. An approach using fire scenarios would ensure all systems are designed to a common performance requirement. This paper will discuss how the current design approach outcomes compared with a fire scenario approach. More effective and efficient fire safety systems would require the stake holders to understand the implication of this approach and to embrace this through the fire engineering process.

Mar 8, 2011

By B Hou

The Eucla Basin in southern Australia is emerging as an important global source of zircon from heavy mineral sands. Understanding the geological evolution of the basin and movement of heavy minerals down peripheral paleovalleys and along paleocoastlines is essential to effectively refine exploration strategies for heavy minerals in the basin. Integration of geoscientific datasets in a Geographic Information System (GIS) environment has proved to be effective in reconstructing depositional environments along the Cenozoic basin margin and in tracing the buried paleorivers that once drained broad areas of the Archean-Paleoproterozoic Yilgarn and Gawler cratons, the dominantly Mesoproterozoic Musgrave and Albany-Fraser Provinces, and the Neoproterozoic-Early Paleozoic Officer Basin. Sea level highstands during the late Middle Eocene (39 - 36 Ma) are associated with formation of the Ooldea coastal barrier complex and the zircon-rich heavy mineral deposits at Jacinth, Ambrosia and Tripitaka. More extensive transgression during the Late Eocene (36 - 34 Ma) built the complex Barton shorelines that host the Cyclone deposit and the extensive ilmenite-dominated occurrences of the Barton West prospect. Multi-generation reworking of the source sands is indicated by the high proportion of deposits that are zircon-rich relative to titanium minerals. The age distribution of zircon grains in heavy mineral concentrates from the Ooldea and Barton barrier systems points to the Musgrave Province as the predominant ultimate zircon source. Paleorivers discharging along the northern basin margin presumably carried a sediment load that was then redistributed by easterly longshore drift to build the extensive coastal sand deposits along the northern and eastern basin margin. The south-eastern extension of these deposits was reworked during Miocene-Pliocene (15 - 2 Ma) times into a series of regressive strandlines that show angular discordance with the Eocene coastlines. This discordance is consistent with evidence for long-wavelength tilting of the Australian continent from Middle Miocene times, as the continent drifted toward a dynamic topographic low induced by convective mantle processes associated with the South East Asia subduction systems. The Dromedary and Gulliver’s deposits probably formed at this time. Ongoing research is focused on the geological features of the basin that influence heavy mineral transport, concentration and preservation, and the processes leading to deposits with high zircon content.

Oct 5, 2011

By Weber W

Methods of calculation of the reliability of process computers are getting more and more important. The paper presents long period observations of 21 process computers with online applications in the iron and steel industry. About 5000 failure events during 10 years have been systematically recorded and evaluated. On the basis of these long time observations it is possible to develop a probability model of the failure behaviour of process computers.This failure model is constructed with four different states of the process computer:Working phase, working phase with undetected reasons, repair phase, failure phase resulting from external influences.The model is defined by differential equations for the probability of one of these four phases. Long time observations show, that all of these four phases are closely correlated with the capa-city of a process computer, restarting without detection of failure reason, changes of programs and software, costs and time of repair. So the result of this analysis is a model of failure for process computers, which allows to predict breakdowns of process computers on the basis of external parameters.

Jan 1, 1985

By Grader F. E

A linear motor properly wound can serve as a mechanism for separating paramagnetic sulphide minerals, like pyrrhotite, from other sulphides and associated gangue minerals. The effective- ness of separation depends on the energising current of the separator, the frequency of the a.c. cycle, and the particle size of the minerals. The speed of travel of the minerals over the surface of the separator is also a function of particle size, and appears to be constant. The movement of pyrrhotite, magnetite and iron filings of comparable size fraction (150um +74pm) on the linear motor surface has been observed using a cine camera. An attempt has been made to give a theoretical basis for the movement of the particles by calculating the minimum electrical energy required to move them. Further, the rate of decay of magnetic moment of the particles has been estimated for magnetite and it has been found that sufficient residual magnetism existed in the particles after they had been exposed to the first half of an a.c. cycle for them to have like polarity with the second half of the cycle. The particles are therefore repelled from the motor surface every second half of the cycle. This repulsion due to remanent magnetism is the probable cause of particle movement over the linear meter surf, e.

Jan 1, 1980

By P J. Handley

"Predicting how coal seams will be beneficiated through the coal handling processing plant (CHPP) has long been challenging within BHP Coal. Various coal seams from different areas are mined and stockpiled separately, often depending upon a deleterious coal quality parameter; high/low trace elements for example. These stockpiles are then fed in different ratios into the CHPP to produce the desired product/s. In understanding the washability characteristics of the feed source, mine geologists and process engineers work together to improve the beneficiation of different coal materials through the CHPP.For the majority of the BHP Coal deposits, the washability data is available for the coal seams across the deposits. However, no previous standardised modelling and prediction technique existed that could ensure the correct information was available for forecasting and refining CHPP processes. This paper will discuss the steps undertaken to implement a geometallurgical prediction tool that simplified and streamlined the washability modelling and yield estimation process. The value realised to the BHP Coal assets resulting from this process was: improved compliance to plan increased throughput increased CHPP recovery through improved efficiencies and increased revenues.CITATION:Handley, P J, 2017. Washability modelling and estimation techniques used to improve coal handling preparation plant beneficiation, in Proceedings Tenth International Mining Geology Conference 2017, pp 327–336 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 20, 2017

By V Lawson

Vale’s Sudbury Clarabelle Mill processes Cu/Ni ores from a number of mines in the Sudbury basin in Ontario, Canada. Bulk sulphide flotation produces a copper-nickel concentrate with pyrrhotite as the major diluent. After successful commissioning of the Voisey’s Bay Cu/Ni Mill (VBN) in Labrador, a miniplant campaign on Clarabelle ore with the VBN flow sheet produced a significant recovery improvement over current performance. In 2001, the Mill Redesign Project moved grinding energy into rock/sulphide and pentlandite/pyrrhotite separation and in 2006 Cu/Ni separation was re-introduced to Clarabelle Mill to produce a saleable Cu concentrate. The projects were a great success. What remained was to simplify the Clarabelle flow sheet by introducing the missing components found in the VBN flow sheet. This project known as CORe has evolved through many stages including the mining boom and surviving the 2008 economic downturn and it is scheduled for completion in mid 2013. This paper outlines some of the challenges faced in this major brownfields project – organizational, technical, financial and operational.

Aug 8, 2011

By A Vakili

Dilution is associated with considerable direct and indirect costs in underground open stoping operations. As shown in previous works, an improved ability to predict dilution enables the economic risks associated with unplanned dilution to be reduced. Depending on the width of the orebody and depth of mining, the economic performance of an open stoping operation can become even more sensitive to dilution. It is shown in several well-documented studies that as little as 1 per cent of additional dilution can impose millions of dollars of lost profits per annum. Optimisation of a stoping operation is therefore largely dependent on the ability of the operation to minimise dilution. This can only be achieved through sensible analysis of past and future performance of mined stopes using the most appropriate recent available technologies and tools. This article presents a new design process that utilises advanced geotechnical numerical modelling and various other analytical tools to assist with a more robust mine design of open stoping operations. The focus of this design process is on geotechnical factors affecting dilution during the life-of-mine. A recent application of this optimisation method for a mining operation is presented in this paper as a case study. Through the application of this method and various other operational improvements, the mine was able to deliver more consistent production and lower operating costs over its life-ofmine outlook and was able to reduce dilution by up to 50 per cent and achieve sustainable record high production rates.

Mar 29, 2023

By A R. Hollis, M Heddon

The safe life cycle of a Tailings Storage Facility (TSF) is founded on the fundamentals of proper design, construction, operation and closure. Leinster Nickel Operations (Leinster) utilises four active TSF cells that are cycled between filling (deposition), desiccation, and construction to meet a targeted rate of rise. This results in ongoing and consistent raising of the TSF walls. Critical to maintaining the safe life cycle through this consistent wall raising is precision construction and high frequency quality assurance to ensure compliance to design requirements and TSF walls free from defects. Leinster has recently deployed Intelligent Machine Control technology for TSF construction. Advances in Intelligent Machine Control have decreased variability in construction; ensuring variations are within the tolerances of design. The Intelligent Machine Controls are programed to ensure construction conforms to design tolerances of +/-30mm. This level of accuracy provides assurance of borrow area set out, compacted layers are as per design, compaction monitoring is within the zone placed, scarification between layers to prevent lamination is maintained, and batter angles are set to the correct grade. This level of control provides certainty that construction meets the design intent. In conjunction with Intelligent Machine Control, periodic drone surveys are conducted to verify construction against design. Advancement in survey equipment and techniques allow higher frequency, high accuracy survey to be completed on demand by site based personnel. This provides quality assurance through all stages of the construction phases, as well as the final constructed wall, ensuring compliance to design. Combining Intelligent Machine Control with higher frequency quality assurance provides an increased level of certainty that the TSF construction is defect free and within quality specifications. These recent technological advancements in Construction and Quality Assurance ensure cell raises are constructed to the design intent with greater levels of accuracy and precision than ever before.

Jul 1, 2021

By J Rubio

This work presents design features of an innovative in-line mixing helical (coiled) reactor for flocculation and flotation as a solid-liquid separation process for suspended particles (including liquid droplets). The device has been named flocs generator reactor (FGR), a compact system whereby the flocculation of particles is assisted by the kinetic energy transfer from the hydraulic flow through the reactor and/or by the injection of microbubbles (30 - 70 ¦m). The flow mixing presented a plug flow regime with a low dispersion degree, promoting the required hydrodynamic conditions to disperse the polymer flocculant (cationic polyacrylamide) and to generate æstrongÆ flocs of Fe(OH)3 or clays (as colloidal model systems) with aggregation using an anionic polymer, Al2(SO4)3 and poly aluminium chloride (PAC), and oil emulsions destabilisation with a high molecular weight cationic polymer. The solid-liquid separation of the flocs was then achieved either by settling or by flotation with microbubbles. This paper discusses advances in this new in-line flocculation-rapid flotation device to remove æaerated aggregatesÆ, aggregates with entrained and entrapped bubbles. Studies were carried out with different models of FGRs (varying the length:volume ratio) and process efficiency (mainly kinetics) evaluated as a function of polymer concentration and some operating parameters, namely, feed flow-rate, air:solids ratio and residence time. Results showed that the aerated flocs are readily floated with rising rates in the order of 120 mh-1, values higher than those obtained for the settling of the non-aerated flocs (18 - 24 mh-1). The FGR requires short residence times and generates dense, well structured flocs (with a mass fractal dimension, dF of about three) which withstand high shear forces. Mechanisms involved appear to include small bubble formation and their rapid occlusion (entrapment) within flocs, nucleation of bubbles at floc/water interfaces, polymer coiling as a result of æsalting outÆ effects at the aqueous/air interface and plug flow type of mixing (flocculation). Successful examples of emulsified oil and solids removal from water are shown and because in all cases high efficiencies were obtained (>90 per cent removal). Due to the high process efficiency and high loading capacity shown, the FGR appears to have good potential as an in-line flotation-separator device in applications requiring high rate solid-liquid or liquid-liquid separations.

Jan 1, 2005

In May 2000, Kanowna Belle Gold Mines (KBGM) carried out a detailed Truck versus Shaft Haulage Study. The study showed that whilst the shaft option had many operating cost benefits the capital costs were too high, therefore the truck option was selected. In May 2001, the concept of achieving æshaft typeÆ benefits without the capital costs was floated. This is achieved by separating the hoisting of ore from other mining activities. The general concept is that material from underground is transported to a central location and then transported to the surface by a special truck fleet, thus removing the dependency between trucks and loaders, providing the mine with surge capacity and decreasing operating costs. At KBGM these advantages have been gained by installing an ore pass system with a plate feeder at its base that directly loads trucks. This provides the mine with a haulage system with enough surge capacity to remove the interdependency between trucks and loaders. The plate feeder is situated just off the decline which creates the opportunity to use larger more reliable, lower cost trucks. A number of truck types were considered for the truck loop including Elphinstone AD55Æs which are the truck type being used on site prior to the truck loop, CAT 775EÆs and power trailer road trains. This paper covers the philosophy behind the truck loop, the truck selection process, project installation and commissioning, people issues and the benefits expected by the operation. As of May 2002, the project is nearing completion, with decline haulage expected to commence in July 2002.

Jan 1, 2002

By B McCarthy

Mining has been typified of late as a boom and bust, cyclical industry operating against a steady decline in the size and quality of mineral deposits. Decreasing deposit grades and increasing costs of traditional mining techniques, all in the face of another commodity downturn, are forcing mining companies more than ever before to seek out new and innovative ways to operate. New technologies are emerging to model, control and track resources through the mining value chain, to move material about mines more efficiently, and to identify and separate ore from gangue early in the extraction process.Discovering such technologies however is only the first challenge for mining companies. Actually implementing technological change successfully has proved to be an even bigger challenge. Like for many industries, fulfilling the promised benefits for the expense and timing envisioned, has not been easy when innovative technologies are introduced.Citing the author’s insights and experiences in a number of emerging technologies, this paper explores barriers to implementing technological change in the mining context. Key elements of a change management framework, first developed for implementing mine management systems, are described to give mining executives insight into how they and their organisations can succeed through technology-driven change.CITATION:McCarthy, B, 2016. Successfully implementing technology-driven change in the mining environment, in Proceedings International Mine Management Conference, pp 89-104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

PIP is regularly engaged in businesses where Greenfield Capital Projects are under- delivering on the expected business case. In most of these projects, we can identify that rigorous review has been carried out on the design and financial cost elements and substantial reporting is maintained to Boards on progress versus plan of project completion and cost. However, in all sites of this nature that we have worked at, the planning, design and execution of the operational elements or æwiringÆ of the organisation have fallen short and resulted in significant extra cost or opportunity cost (lost tonnage or quality) during start-up. When compared to the amount of planning and resources that have been poured into the capital side, the ledger on the æwiringÆ side is typically fairly sparse. This presentation outlines the importance of running a disciplined, rigorous process to prepare the human and wiring side of a start-up to ensure rapid start-ups and put the site on the pathway to high performance. It gives an outline of the rigorous process PIP has used with projects to ensure excellent start-ups.

Jan 1, 2006

By Fradd WP

South Australia pioneered metal mining in Australia and was the main source of copper for several decades. Gold discoveries and mining also contributed significantly to the development of the Colony. Across the State can be seen the holes, the mullock heaps and, in some instances, the remnants of machinery of the past era. In this, the centenary year of the discovery of the Teetulpa goldfield, considered by some to he the most significant discovery of gold in the State, it is appropriate that we should present a paper on the history of gold mining in South Australia. South Australia has not been a major producer of gold with recorded production a little in excess of 15 million grams (15 t). This represents about 0.25 per cent of the Australian total and ranks last of the States of the Commonwealth. The outstand- ing feature of gold production in South Australia has been the succession of short periods of rela- tively high production immediately following a discovery, with payable dirt being quickly exhausted, a fact clearly illustrated by the graph of South Australian gold production (Figure 1).

Jan 1, 1987

By A S. Derrington

In some parts of Australia, mine air cooling may not be needed until a depth of 1300 m below surface is reached. In other locations, it may be essential at a depth of only 300 m below surface. The reasons for these differences are multifaceted. This paper discusses the main factors and describes a simple method to assess whether or not mine air cooling will be required. The method uses a graphical relationship that considers depth below surface, geothermal gradient, surface climatic conditions and directness of the mine intake routes. This relationship has been developed, tested and refined over a period of more than ten years using data collected from most of Australia’s deeper metalliferous mines. The method provides a ‘first-pass’ indication of whether more detailed cooling studies may be needed. Perhaps more importantly, the method’s underpinning by benchmarking against other mines improves confidence in the assessment results. Like any empirical method, the context must be understood and this aspect is also discussedCITATION:Derrington, A S, 2014. Will your mine require cooling?, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 181–186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By Winrove G. S, Herdie G. J, McCarthy C. A

Production of hot metal from the Hlsmelt Research and Development Facility at Kwinana, Western Australia commenced in October 1993. The stand-alone facility is a unique, coal-based, integrated ironworks equipped to process iron ore fines to pig iron and simultaneously undertake a wide range of research tasks. The data generated will be used to verify the commercial potential of the technology and to set the design and operating parameters for a full-scale production plant. The design, construction, commissioning and initial operation of the HRDF has required many innovative and practical solutions to be developed and implemented by the international group of organisations contributing to the Hlsmelt Project. Initial operation has produced results which demonstrate the potential of the unique process technology associated with the core plant smelting unit. The recent achievement of post-combustion levels of 60 per cent with heat transfer efficiencies greater than 85 per cent demonstrates that the performance obtained with the Small Scale Pilot Plant in Maxhutte, Germany can be reproduced at a larger scale. The results presented in this paper support the thrust for further intensification and future commercialisation of the process.

Jan 1, 1995

By B R. Castley

Consumable materials used in mines are often transported to the working areas down shallow angle decline shafts, typically at anywhere between 10¦ and 30¦ to the horizontal. The winding equipment is usually a relatively small single-drum winder and the material is transported in one or more cars, running on rails in the decline. The winding rope is attached directly to the cars, which are mechanically coupled together. For small rock hoisting declines, the cars are replaced with hoppers or skips. The winder is normally of basic design, fitted with only the minimum required safety devices and very elementary brake control. Since these winders are not ælicensedÆ and are usually located in remote areas, the standard of maintenance on the installations is often poor, leading to frequent accidents, resulting in runaways, derailments and broken ropes. These problems can be overcome easily with the application of the rope haulage principle. When large volumes of ore have to be transported to surface, belt conveyors are used on shallow angle inclines, or high-capacity friction winders are used in vertical shafts. Conveyors are limited to inclines no steeper than 14¦ and vertical shafts with large friction or drum type winders are extremely capital-intensive. Rope haulage systems can be used on decline shafts where the inclination is too steep for belt conveyors and too shallow for conventional drum winders. Rope haulage systems also offer a variety of safety, technical and cost advantages over other winding and transport systems. This paper describes the adaptation of the rope haulage principle to modern requirements and, combined with 21st century electronic technology, explains how the principle can be used as an efficient, safe and practical solution to some problems associated with the transport of materials, personnel and ore in mines. The authors describe the designs, methods of operation, safety aspects, automated control, loading and unloading facilities of modern rope haulage systems used for transporting personnel, material and ore. This paper considers a variety of systems already designed for different applications, from small material-only installations to multi-purpose and large rock-hoisting systems with payloads as much as 180 t. It also describes in more detail, a material transporting system recently commissioned in South Africa.

Jan 1, 2005

The purpose of the Lower Lea Valley Cable Tunnel project is to relocate the overhead power lines circuits, which currently cross the proposed site for the 2012 London Olympics in East London. This was the first contract to be awarded as an Olympic project and is on the critical path for the proposed Olympic Park as the construction of the Olympic village, stadium and other venues cannot begin until the tunnels are complete, the cables installed and the overhead power lines removed. The tunnelling works for the scheme include two parallel tunnels between Hackney and West Ham. Each tunnel is approximately 6 km in length. One tunnel is 4.15 m ID and connects the National Grid substations. The other is 2.82 m ID and connects the EDF Energy substations. The tunnels were constructed through mixed ground using four earth pressure balance tunnel boring machines. These were driven simultaneously from two drive shafts within a single site. The 12 km of main tunnels were constructed within a year from start to finish, with completion in June 2007. The shafts range between 6 m and 15 m ID. These were constructed using a combination of caisson sinking and underpinning techniques. Dewatering was adopted to suit the groundwater conditions.Other works include the design and construction of the head house buildings, cable and ventilation culverts, mechanical and electrical (M&E) installations and all associated works. In addition to the above, a further 1 km of tunnel and two shafts were added to the project scope connecting the EDF Energy tunnel to the substation at Bow. These additional works provided further challenges to the project to ensure that these works were constructed within the program constraints for the 2012 London Olympics. This involved refurbishing one of the tunnel boring machines from the main EDF Energy tunnel drives and relaunching the machine to construct the Bow tunnel. The Bow tunnel was constructed within two and a half months, with the tunnel boring machine breaking through in August, ahead of schedule. The main challenge presented by this project is the program constraints. This project outlines the requirement for team work between the client, stakeholders, contractor and designer in order to provide program certainty. A close working relationship between the contractor and the designer is required to provide value engineered, time-saving solutions to mitigate the risks associated with the design and construction program.

Jan 1, 2008