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By F T. Suorineni

Empirical methods are deeply rooted in geomechanics. This is a consequence of the recognised complexity of the nature of the rock mass. The usual assumptions of material continuity, homogeneity, isotropicity and linear elasticity often assumed for soil, concrete and steel are difficult to justify in a rock mass except for mathematical convenience. These assumptions form the bases for most mechanistic, analytical and numerical methods in geomechanics. Believers in empirical methods argue that the complexity of the rock mass and its interaction with structures developed in it is adequately accounted for in empirical methods, which compensate for our ignorance.Franklin (1993) defines empirical design as quantified judgement based on experience. He further states that empirical methods often prove ‘closer’ to the ‘truth’ than the apparently more precise predictions of theoretical analysis, adding that based on real data empirical methods provide a standard against which theoretical predictions are measured and can be judged. This paper takes a critical look at the common empirical methods in geomechanics – rock mass classification systems (Bieniawski, 1973; Barton, Lien and Lunde, 1974; Hoek, 1994a), Laubscher block caving design rules (Laubscher, 1994), the stability graph (Mathews et al, 1981), pillar design equations (Salamon and Munro, 1967; Hedley and Grant, 1972; and their derivatives), pillar design chart (Lunder and Pakalnis, 1997) and failure criteria (Hoek and Brown, 1980; and its derivatives). The common thread in the application of these methods is that in most cases they are often applied blindly without an understanding of the underlying assumptions and database limits. This paper emphasises that users of these methods need to know the underlying assumptions, database limits and inherent hidden risks that are often unmentionable for their satisfactory use. Finally, suggestions are provided for the efficient use of empirical methods and how they can be improved.CITATION:Suorineni, F T, 2014. Reflections on empirical methods in geomechanics – the unmentionables and hidden risks, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 143–156 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By A Mirzaghorbnali, D Gilbert, R Burton, J Nemcik, N Aziz

Glass-reinforced polymer bolts, commonly known as fibreglass dowels and fibre-reinforced polymer or plastic bolts or plastic dowels are increasingly applied for strata reinforcement in mines as well as in concrete reinforcement in civil engineering. The most popular dowels used in coalmines are the 22?mm diameter fully threaded type. Fibreglass and plastic bolts are cuttable, easy to handle, lightweight and corrosive resistant. A series of tests were undertaken to evaluate various strength properties of fibreglass dowels. These included tensile failure tests by the double-embedment method, a single guillotine shear test and a double shear test, carried out on dowels installed in concrete blocks, and with punch shear tests. Punch shear tests were used to evaluate the dowel shear strength parallel and perpendicular to the fibreglass strands or elements direction of extrusion. The study found that the tensile strength of the 22?mm diameter fibreglass dowels was in the order of 30?t. In the shear testing, the peak shear load was influenced by the encapsulation grout type and the level of fibreglass axial pretension. Also, there was a nearly fivefold difference in the shear strength value of fibreglass dowels tested parallel as against perpendicular to the dowel axis.CITATION:Aziz, N, Gilbert, D, Nemcik, J, Mirzaghorbnali, A and Burton, R, 2014. The strength properties of fibreglass and other polymer-based dowels for strata reinforcement in coalmines, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 263–268 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By L R. Sousa, M He

Rock burst is common in deep underground excavations and is characterised by a violent ejection of block rocks from excavation walls. It is critical to understand the phenomenon of rock burst and particularly the failure mechanism. Laboratory experiments are one of the ways. For that purpose, a rock burst laboratory test system was developed at the State Key Laboratory for Geomechanics and Deep Underground Engineering at the China University of Mining and Technology, Beijing. A true triaxial test system, designated the Deep Underground Rock Burst Analogue Test Machine, was developed, which can transfer a stress state from three-direction-compression on six surfaces to the compression on five surfaces with one set free. The rock burst experimental system comprises an acquisition of acoustic emission signals, a high-speed recording in order to accurately record the kinetic characteristics of rock fragments ejected during a rock burst event and the possibility of infrared thermography showing the surface temperature of the samples. In this paper, analyses of typical results from rock burst tests are presented with a description of the obtained results. The mechanisms of rock burst are illustrated, and a rock burst classification is proposed based on these laboratory tests. For the control of rock burst, the constant resistance, large deformation (CRLD) bolt or anchor is presented for accommodating the large displacement of surrounding rock masses and absorbing the impact of the sudden release of rock burst while outputting a constant resistant force in response to the external load. The CRLD bolt or anchor has had practical applications in underground mines. Finally, in situ tests performed in a tunnel at Qingshui coalmine, China, are analysed in detail.CITATION:He, M and Sousa, L R, 2014. Experiments on rock burst and its control, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 19–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By M Sandy, A Vakili, J Albrecht

Although rock strength anisotropy is a well-known phenomenon in rock mechanics, its impact on geotechnical design is often ignored. No widely accepted guideline currently exists for its characterisation. Anisotropy can significantly control the failure mechanism and progression of damage into the rock mass, particularly in high-stress conditions. As such, it can play a key role in the stability of underground excavations and subsequent geotechnical design.This paper introduces the concept of anisotropy at both intact and rock mass scales. It then presents guidelines for measuring anisotropy and assigning rock mass strength properties. An improved unified constitutive model (IUCM), which can account for more complex failure mechanisms, is then briefly described. This IUCM is used to better understand the typical responses of anisotropic rocks to underground mining and to develop an improved damage classification scheme for these conditions.The application of conventional design methods in anisotropic conditions is shown to lead to significant errors. Two case histories are then presented, illustrating how the proposed methodology can improve the reliability and accuracy of the geotechnical analysis when compared with conventional design methods.CITATION:Vakili, A, Albrecht, J and Sandy, M, 2014. Rock strength anisotropy and its importance in underground geotechnical design, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 167–180 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By K A. Heasley

The LaModel program was initially developed in 1993, and it is used to model the stresses and displacements in thin tabular deposits such as coal seams. It uses the displacement-discontinuity variation of the boundary-element method with a simplified laminated overburden model and because of this formulation, it is able to quickly and effectively analyse large areas of single- or multiple-seam mines. Over the last couple of decades, LaModel has been used by many mine engineers and researchers for improving pillar designs and mine safety, and it has been continually updated to add functionality and improve its ease of use and accuracy. The present LaModel can calculate seam displacements and overburden, multiple-seam and total seam stresses, pillar safety factors, energy values, roof-bending stresses, fault effects and surface subsidence. It can automatically generate the mine and overburden grids from AutoCAD drawings, and it includes wizards for automatically generating Bieniawski strength coal pillars, easily calibrating the overburden properties to observed abutment stresses and calibrating the gob material to expected gob loading. This paper will present the formulation and features of the modern LaModel program and demonstrate its utility with a multiple-seam case study from the rugged topography in Southern Appalachia.CITATION:Heasley, K A, 2014. LaModel – a program for coalmine modelling, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 409–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By D J. Kilkenny, D A. O’Toole, P B. Hills, K L. Seah

An investigation was undertaken to critically analyse the use of fibre reinforced shotcrete (FRS) for a variety of applications in large diameter shafts. Those applications included the use of FRS with or without the addition of subsequent rock bolting in the temporary support cycle prior to the installation of a permanent lining, most likely cast in situ concrete or as the final lining medium.Numerous authors have considered the early re-entry and strength characteristics of FRS in recent years. The current study has investigated the practical application of the recommendations of many leading authors in an endeavour to establish practical and acceptable risk-assessed procedures for the use of FRS for rapid, safe, efficient and cost-effective shaft sinking.Shaft sinking is regarded as a specialist and potentially higher risk activity due to the confined work environment, exposure to ground conditions and a high degree of manual handling associated with getting materials to the sinking face. The use of robotically applied FRS as a primary lining in shaft sinking has significant safety advantages in reducing manual handing associated with mesh safety support and bolting, as well as reducing direct exposure to ground conditions.The study involved both field testing and a literature review. The study established an initial set of criteria for the use of FRS in the development of large diameter shafts and demonstrated a number of scenarios where the technique of robotically applied FRS provided significant safety and cycle time advantages. The opportunity for a fully sprayed single pass lining was also investigated as part of the project.CITATION:Hills, P B, O’Toole, D A, Kilkenny, D J and Seah, K L, 2014. Exploring the use of fibre reinforced shotcrete in large diameter shafts, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 295–306 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By M Wieloch, D Wimpenny, M Chappell

Fibre-reinforced geopolymer concrete (FRGC) contains no Portland cement or steel reinforcement, but instead uses synthetic fibre reinforcement and a geopolymer binder. The use of geopolymer binder in lieu of Portland cement reduces the concrete’s embedded energy (CO2 emissions) whilst the use of synthetic fibres eliminates the issue of reinforcement corrosion, thus enhancing the overall long-term durability of concrete. This paper presents the development of FRGC during a three-year project funded by the Victorian Science Agenda and a consortium of five organisations. The work involved laboratory and field trials and the production of prototype tunnel segments that have been subject to durability and fire testing.FRGC has exceeded the performance of the Portland cement-based control mix in terms of flexural strength, chloride diffusion, water sorptivity and drying shrinkage. Furthermore, the FRGC segments subjected to a simulated hydrocarbon fire test did not exhibit explosive spalling; however, the creep of FRGC was approximately three times that of the steel fibre-reinforced Portland cement-based control mix. The compressive strength and tensile splitting strength of the FRGC were also lower than the control mix. These differences need to be allowed for in the design using FRGC.Prototype bolted tunnel segments of up to 0.8?t mass have been produced from FRGC using standard production techniques and ambient curing. These were successfully produced within a 24-hour production cycle. Cut sections through the segments showed good compaction and even distribution of fibres. The estimated carbon footprint of tunnel segments produced using FRGC is approximately 70 per cent less than that of Portland cement-based segments containing 25 per cent fly ash and steel reinforcement.The results to date indicate that FRGC has the potential to produce a new generation of tunnel segments and, in general, precast concrete products with increased durability and substantially reduced carbon emissions compared to the Portland cement-based concrete with steel reinforcement.A summary of further research carried out by CH2M HILL into a complete elimination of ferrous inserts from segmental concrete tunnel lining is also summarised in this paper. The use of non-ferrous connectors for radial joints in combination with the FRGC technology in the manufacture of tunnel segments will effectively lead to development of a new generation of segmental tunnel lining systems.CITATION:Wimpenny, D, Chappell, M and Wieloch, M, 2014. Fibre-reinforced geopolymer concrete – an innovative material for tunnel segments, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 345–352 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By D Kubik, K The

The New Zealand (NZ) Transport Agency’s Waterview Connection will complete Auckland’s Western Ring Route, a 47 km north–south motorway alternative to Stage Highway 1. The project is being delivered by the Well-Connected Alliance comprising the New Zealand Transport Agency (NZTA), Fletcher Construction, McConnell Dowell Constructors, Obayashi Corporation, Parsons Brinckerhoff NZ, Beca Infrastructure and Tonkin & Taylor.The project involves construction of 5 km of new motorway, nearly half of it underground connecting State Highway 20 (SH20) to State Highway 16 (SH16). The underground portion of the project incorporates twin 13.2 m inside diameter (ID) tunnels 2.4 km long, each carrying three traffic lanes, one for north-bound traffic and one for south-bound traffic. The tunnels are being driven by a 14.46 m outside diameter (OD) 2400 t, tunnel boring machine (TBM) shield that was assembled and launched at the southern portal. It will be turned and re-launched at the northern portal for the return drive to the southern portal where it will be disassembled. This paper presents two major temporary works elements contributing to the successful launch of the TBM: the TBM assembly crane platform and the TBM shove frame and associated components.Tunnel boring machine shield assembly – crane platformThe TBM shield was delivered to site in subassemblies ranging in weight from 100 to 380 t. It was initially proposed to use a 750 t crawler crane sitting above the tunnel portal headwall to assemble and disassemble the TBM. However, this did not have sufficient capacity to allow the TBM shield to advance clear of the tunnel before disassembly commences. To reduce the crane’s working radius a temporary steel crane platform was developed that is supported on the side walls of the tunnel approach trench. This has enabled a smaller, less expensive, 600 t crawler crane to be used and will allow the TBM shield to clear the tunnel before disassembly.Tunnel boring machine launch – temporary worksTo launch the TBM a purpose built steel frame was required for the TBM thrust rams to react against. The shove frame had to be able to transfer the thrust loads from the TBM shield to the ground below and thrust wall behind. A range of potential thrust loads and jacking patterns were examined to develop the design load cases for the shove frame. The shove frame was used to launch the TBM at the southern portal and to re-launch it at the northern portal. Elements of the shove frame will also be used to support the portal faces during the TBM arrivals.CITATION:Kubik, D and The, K, 2014. Waterview Connection – temporary works for tunnel boring machine?launching, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 281–288 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By M Rauer

With a worldwide growing population the demand for higher living standards, food and the development of new technology is rapidly rising. To allow for a continuous growth, larger quantities of minerals and raw materials are needed at a faster pace. Different methods have been developed to access or tap ore more quickly, such as improved drill and blast operations, mechanical mining methods using equipment such as roadheaders (RH), longwall miners and other technical equipment. Another possibility to access and develop mines faster is the use of a tunnel boring machine (TBM).The historical usage of TBMs is surprisingly long, but the opportunity for technology adoption by the majority of worldwide mining companies remains largely untapped. Dozens of full face TBMs have been used by mines around the world, including two that will begin operation soon in Australia. TBMs have been used to safely and rapidly gain access to the orebody, or to expand access to the orebody to increase output by running a TBM along the edge of the orebody for several kilometres. These machines have also been used for ventilation and for conveyor tunnels for ore removal. They have been used to quickly excavate long and winding declines giving access to an orebody at several levels in a short period of time.Tunnel boring technology can be used for mine declines, mine access tunnels and all sorts of different mine designs and set-ups. TBM technology simply needs to be adapted to the mine conditions and, if manufacturers are involved early on in the planning process for mine development, the operation can be very successful. In some cases, historically typical mine designs may need to be re-thought.One mine, the Stillwater Platinum mine in Nye, Montana, is currently employing its fourth TBM in 25 years. Two were used to create tunnels running alongside the orebody, rapidly expanding access to the orebody in many locations for increased output. Two were used to create parallel access tunnels to a mine expansion at the East Boulder orebody; one tunnel is for conveyor haulage and the other for vehicular access. TBMs have been employed successfully many times to rapidly drive vehicular decline tunnels to multiple mine levels, such as at the San Manuel – Magma Copper mine in the USA. While TBM technology may not seem to be optimal for every mine, these success stories show that the method can provide vast benefits for the right projects.Early use of TBMs in extremely hard rock metal mines, in the 1960s and 1970s, had limited success since performance was low. However there have been great improvements made over the years in the strength of rock which can be excavated by TBMs with high performance. Other important improvements involve the provision of a safe work environment, safely and rapidly supporting the rock and predicting geology ahead of the TBM.This paper will briefly note the more than 20 TBM mining projects and highlight some notable successes. It will then go on to give a status report on the two active TBM mining projects in Australia and the difference between a TBM operation versus other excavation methods such as drill and blast (D&B) or RH excavation.CITATION:Rauer, M, 2014. Tunnel boring machines in mines – a?brief review of past use with a status report on use today in Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 663–670 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By M Norbert, P Mok

The mainline running tunnels for Legacy Way comprise of two-lane tunnel boring machines (TBM) driven tunnels. The length of the TBM tunnel section is approximately 4.2 km. The TBMs employed are double shield TBMs. Typical support to the segment ring while advancing a double shield TBM comprises of filling the excavated annulus between the ground and the segmental lining by injecting pea gravel, followed with primary grouting to fill between the pea gravel some distance behind the excavated face. The methodology adopted for the Legacy Way project, however, did not follow this typical approach, instead, two component grouting of the annulus was carried out.Where the annulus is typically filled with pea gravel, support is provided to the segment ring very close to the end of the tail shield, whereas in the case of two component grout this is not practical as the risk of grouting in the tail shield is high. The staging of the two component grout injection, the grout early age strength properties become key issues in ensuring that the segment ring leaving the TBM tail shield is stable and can support the necessary external loads.Two-component grout is a grout with two components, cementitious grout (component A) and accelerator (component B), commonly adopted for earth pressure balance (EPB) TBM. The grout reaches its thixotropic state in a matter of seconds providing initial support for the segment rings. Manual injection of two component grout to fill the bore annulus was carried out in stages leaving a portion of the segment rings unsupported. Ring stability during TBM advance was provided by a combination of ram thrust and the segment circumferential joint shear connectors.This paper outlines the design considerations such as rock load derivation by probabilistic analysis carried out utilising the software JBlock, 3D finite element analyses using the software Strand7 for ring stability and the testing and back analysis of the shear connector load bearing behaviour. In particular, the actual available capacity of the shear connectors against their published capacity by supplier was discussed.CITATION:Mok, P and Norbert, M, 2014. Tunnel boring machine excavation stability – double shield tunnel boring machine advance with partially grouted annulus, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 51–62 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By A Harding, M Chappell

Precast concrete segmental linings have enjoyed widespread use around the world, and are the lining type of choice for tunnels constructed using a shielded tunnel boring machine. However, there is significant variation in the design of such linings from one country to the next in such areas as materials, geometry, fixtures and fittings, waterproofing and reinforcement to name but a few. This arises because the speed at which the technology has developed within some countries and regions has sometimes outstripped the transfer of such technologies to the rest of the world.This paper provides some insights into the variations in lining design in different parts of the world with the aim of providing designers and constructors alike a reference for the different methods adopted. It provides a context for these developments by briefly summarising historical reviews of this subject before looking at some of the developments around the world over the last 15–20 years. The developments are presented with some reference to the reasons for implementation, and the advantages and limitations commented on. Following on from this description of the state-of-the-art, the authors also provide their own views on what developments we may see in this area in the near future.CITATION:Harding, A and Chappell, M, 2014. Precast concrete segmental tunnel linings – the state-of-the-art, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 257–266 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By T Ireland, S Eratne, W Newns, P Spies

The approach to risk management during the procurement of major projects often has a significant outcome on the ultimate delivery of a project. The NZ$1.4 B Waterview Connection project is the largest and most complex project yet undertaken by the New Zealand Transport Agency (NZTA) and the procurement process for an alliance contract was refined to provide compliance with the International Tunnel Insurance Group (ITIG) Code of Practice for Risk Management of Tunnel Works (TCoP). The principle of shared risk within an alliance incentivises a common understanding of project risks prior to finalising the alliance agreement and therefore enables superior risk management through design, construction and beyond. Risk management practices need to be instigated well in advance of commercial phases, so that commercial competition does not lead to a significant elevation of project risk. In particular the practice of gaining commercial advantage by taking on a potentially unmanageable level of risk is one of the outcomes to be avoided by the TCoP.During the procurement phase the NZTA placed high value on design and construction mitigation measures proposed in order to address ground risks, as is appropriate for a major tunnel project. In order to achieve alignment on the level of geotechnical risks an Alliance Geotechnical Baseline Report (AGBR) process was developed.This paper describes the measures taken during the procurement process to achieve certainty with respect to outcomes and minimise project risks whilst also achieving value for money. Refinements to the procurement process to ensure compliance with the TCoP prepared by the International Tunnel Insurance Group (ITIG) are described along with the AGBR process applied as part of a suite of measures to achieve a successful procurement outcome.CITATION:Ireland, T, Spies, P, Eratne, S and Newns, W, 2014. Risk management and use of a geotechnical baseline report for a competitive alliance procurement?process, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 553–562 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By P K. Wong, D A. F Oliveira, F M. Azad

In situations where foundation piles are located in proximity to existing or future tunnels, it is typical for the tunnel owner to require that sleeving of the piles be carried out to at least the invert of the tunnels to minimise any load transfer to the tunnel lining. In competent rock, this practice may be sometimes unnecessary, thus uneconomical. This paper presents an assessment of the effect of pile loading from one of the multi-storey buildings at Barangaroo South in Sydney on the adjacent future Sydney Metro tunnels. It was originally required by Transport for NSW (TfNSW) that the piles be sleeved below the tunnel invert level; however, the building developer wanted to reduce the pile sleeving depth to achieve a more economical solution due to the large number of load transfer piles being required for the project. To assess this feasibility, a full 3D commercial numerical code, FLAC3D, was used to carry out this complex soil-structure interaction analyses. Based on these assessments, it was demonstrated successfully to the TfNSW that the pile sleeving may be terminated at 2 m above the tunnel invert level. For this arrangement, the investigations found that the loading on the piles should have negligible adverse impact on the tunnel lining design. As a result of such an assessment, the proposed pile sleeving level was approved by TfNSW, thus offering an economical foundation solution for the project.CITATION:Azad, F M, Oliveira, D A F and Wong, P K, 2014. The impact of pile loading on adjacent metro tunnels – Barangaroo South, Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 355–360 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By B Chapman, R Nievergelt, J Hill

A major component of Sydney’s new South West Rail Link project is the Hume Highway Underpass (HHU), an 80 m long twin track mined tunnel excavated at a depth of just 5 m below the pavement of the Hume Highway; one of Australia’s busiest road corridors.In order to ensure a safe and efficient construction of the underpass without disruption to the Hume Highway traffic, design of the HHU required specific focus on the prediction and control of ground movements. This paper describes the design and construction solutions adopted in response to these challenging constraints. The paper also provides discussion on the observed behaviour of the underpass during construction and the results of a back analysis that was undertaken during construction.CITATION:Hill, J, Nievergelt, R and Chapman, B, 2014. Design and construction of Sydney’s South West Rail Link Hume Highway Underpass, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 375–386 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By L Nagy, K P. Juhasz

The authors were engaged to optimise a traditional rebar cage reinforced concrete segmental lining by means of finite element analysis (FEA) using macro synthetic fibres for the Shanghai metro extension. The aim of this study was to reduce or entirely replace the original steel reinforcement of the segmental lining, in order to make the precast production process faster and more economic. The outer diameter of the tunnel was 6200 mm, the thickness of the segments was 350 mm.The numerical calculations were performed by Atena Finite Element software, which is based on the combination of Menétrey-William and Rankine failure surfaces on the compression and tension sides respectively. The effect of the macro synthetic fibres was modelled as tension stiffening on the tension surface.A one-to-one full scale model of an assembled tunnel ring using the original reinforcement cages was tested at Tongji University in Shanghai, July 2013. The ring was tested to differing load levels where load and displacement were measured until failure. The author’s first step was to calculate the real displacement characteristics of the original reinforced concrete (RC) ring, then calculate the numerically modelled version, so as to compare them. The material parameters of the concrete and rebar used had been determined through basic material tests conducted at the Tongji University. (Bi, Liu and Wang, in press).The numerical modelling undertaken has shown good correlation with the full-scale physical test results. Optimisation of the lining reinforcement was achieved through the addition of fibres, resulting in a substantial reduction of the steel rebar cages. Several results have been computed with the numerical model using different dosages of macro synthetic fibres, showing that the mass of steel reinforcement could be reduced by 50 and 75 per cent respectively.CITATION:Juhasz, K P, Nagy, L and Winterberg, R, 2014. Full-round numerical modelling of a macro synthetic fibre reinforced tunnel boring machine tunnel in the Shanghai Metro extension, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 477–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By D Miller, M Dowling, R Domotor

"This paper is focused on blasting activities undertaken as part of the Pacific Highway Upgrade – Tintenbar to Ewingsdale – project (T2E). This is a ‘priority 1’ Pacific Highway road construction project in New South Wales (NSW), to be completed by mid-2015 (weather permitting). T2E will provide approximately 17 km of dual carriageway road starting at the northern end of the Ballina bypass and extending to the Ewingsdale interchange, and will complete the existing dual carriageway road between Ballina and the NSW/Queensland border.Roads and Maritime Services (RMS) (formerly the Roads and Traffic Authority) is delivering the project on behalf of the NSW state and federal governments. In October 2011, RMS awarded a contract to Baulderstone Pty Ltd (now Lend Lease Engineering Pty Ltd – Lend Lease) to design and construct T2E. One of the key elements in this project is the St Helena Tunnel.In order to avoid the steep grades of St Helena Hill, eliminate a well-known accident black spot and maintain the aesthetics of the Byron hinterland escarpment, RMS and Lend Lease prepared designs to construct a 434 m long dual carriageway tunnel, 46 m below the ridge line of St Helena Hill. Lend Lease elected, where geotechnical conditions permitted, to use drill and blast methods to excavate the full tunnel profile, instead of traditional mechanical excavation techniques.Since all blasting locations (both inside and outside the tunnel) were in close proximity to nearby residents, the NSW Department of Planning and Infrastructure imposed strict air blast overpressure (airblast), ground vibration (vibration) limits and limited working hours. Both RMS and Lend Lease recognised that these restrictions meant that nearby residents may be exposed to blasting activities for longer than was necessary. As a result, after close consultation and agreement with the nearby residents, RMS applied successfully to the NSW Department of Planning to increase the airblast and vibration limits, as well as the working hours.Working under these new conditions, Lend Lease employed a range of best practice drill and blast technologies provided by both Orica Australia Pty Ltd and Atlas Copco Mining and Rock Excavation to improve the safety and efficiency of blasting activities and to minimise the potential negative impacts of the blasting works on affected residents. These technologies included: the use of a continuous environmental monitoring system to record the results of the blast events and provide quick and easy reporting to key stakeholders to address RMS specification requirements electronic detonators to enable accurate hole detonation timing for vibration compliance and to give project engineers the flexibility and precision to alter each design to suit the geological profile of each face the use of two software programs and advanced drill rigs to enable the efficient design of blasts, electronic transfer of designs to the drill rigs, as well as in-hole monitoring and recording of drilling performance the use of a specialised bulk emulsion system to deliver fully coupled bulk explosives into face blastholes to maximise fragmentation, and decoupled bulk explosives into perimeter blastholes, to reduce overbreak and deliver a cleaner profile.By taking a progressive approach towards the environmental restrictions and the work hours imposed, as well as utilising best practice blasting techniques, RMS and Lend Lease were able to blast with confidence and achieve their production deadlines and reduce the total cost of the project.Most importantly, RMS and Lend Lease were able to meet their environmental obligations and work constructively with the nearby residents to ensure that the blasting was undertaken as safely and efficiently as possible without delay or negative impact.CITATION:Dowling, M, Domotor, R and Miller, D, 2014. Improving excavation efficiency at the St Helena Tunnel using best practice drill and blast techniques, in Proceedings 15"

Sep 17, 2014

By M Burdick, A Harding, M Krulc, M Chappell

Substantial schedule advantages can be made on projects if cross-passage construction can occur at the same time as tunnel boring machine (TBM) operation with little or no impact on TBM logistics. However, this approach can prove difficult to achieve with many of the more cost-effective means of supporting the segmental lining during cross-passage break-out. This paper discusses the constraints and shortcomings of conventional approaches, and describes how a cost-effective solution involving a shotcrete shell and opening constructed inside the segmental lining was designed and constructed to deliver cost and time savings on Seattle University Link contract U220.The paper explains the spatial and schedule constraints on the TBM tunnelling and cross-passage construction, and how a shotcrete solution was arrived at in preference to traditional approaches. As the solution was novel the design had to be robust, and the paper explains how this was achieved through a combination of 3D finite element modelling and closed form solutions. Following a description of the trials to verify that the structure could be demolished post-cross-passage completion, the paper describes how the shell solution was constructed, used and demolished safely to leave the lining surface in a clean and undamaged state fit for tunnel operation.CITATION:Harding, A, Chappell, M, Burdick, M and Krulc, M, 2014. Opening supports to segmental linings – a novel shotcrete support solution, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 267–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By C Harrison, A Bowskill

The Ambuklao hydroelectric dam was originally constructed in the 1950s in the remote and mountainous region of the northern Philippines. Following its construction the dam has suffered heavily due to siltation and a partial collapse of the intake structure due to a 7.8 magnitude earthquake that struck the region in 1990. Between the years 1990 and 1999 the power station progressively lost its capacity to generate power. In 1999 the owner took the power station out of commission. The power station remained idle over the next 12 years. In 2008 the power station was sold to a new owner who commissioned the rehabilitation works.The rehabilitation project restored the operating status of the power station in June 2011 and increased its capacity from 75 MW to 105 MW. The civil contract of the rehabilitation project required the construction of a new intake structure behind an in situ rock coffer dam on the edge of the existing reservoir, new 6.2?m diameter × 124?m deep blind sunk shaft behind the intake structure, which connects to a new 6.8?m horseshoe profile headrace tunnel that ultimately connected onto the existing vertical penstocks which feed three No 35 MW Horizontal Turbines rated at 155?m head.The unique challenge in rehabilitating this existing hydropower station involved finding solutions that would conclusively deal with the challenging geological and hydrogeological conditions associated with excavating new tunnels and a drop shaft beneath a live dam.McConnell Dowell was awarded the civil works package for the rehabilitation works in August 2008. The Ambuklao rehabilitation program took 33 months to complete.Over 600?m of tunnels were excavated in highly weathered and often challenging geotechnical conditions via drill and blast with the extensive use of high-pressure fissure grouting to control groundwater ingress that was surcharged by the dam.This paper focuses on the use of high-pressure fissure grouting that took place to enable the excavation of the new waterway system and intake structure.CITATION:Bowskill, A and Harrison, C, 2014. High-pressure fissure grouting for drill and blast tunnelling, Ambuklao, Philippines, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 141–152 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By E P. O’Dwyer

Segment and gasket lining in tunnel boring machine (TBM) tunnels; and sheet membrane lining systems in driven tunnels are robust waterproofing systems each with a proven history of performance in Australia and further afield. Where an interface between these two systems occurs, the potential for costly failures is vastly increased and additional attention to detail is required in design, planning and construction. TBM cross-passages represent the most common occurrence of this interface, with steel compression flanges and neoprene gaskets being the typical means of connecting the waterproofing systems. There is a large variance in both detailing these flanges and associated outcomes, which makes this an area where there is room for improvement within the industry.The paper will look to tease out the various issues associated with this interface and how they can be dealt with efficiently with appropriate design measures, robust planning and carefully controlled construction methods.The paper will also look to review the new technologies and systems currently being put forward as potential alternatives, including an epoxy tape system, which has recently been successfully trialled on a project in Europe under high-pressure head.CITATION:O’Dwyer, E P, 2014. The challenge of waterproofing cross passages in segmentally lined tunnel boring machine tunnels, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 315–322 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By S J. Clarke, G Sieders

Double corrosion protection (DCP) rock bolts have evolved to become complicated assemblies comprising numerous components. This complexity is mainly associated with durability considerations including potential exposure to adverse groundwater conditions and ensuring separation of dissimilar metals within the bolt assembly itself.Recent progress in the construction of glass-fibre reinforced polymer (GRP) rock bolts have the potential to provide a viable alternative to conventional steel rock bolts in civil tunnelling applications. The durability of the material results in a much simpler bolt detail and permits the use of resin rather than solely cement based grouts.This paper presents the findings of the comparative structural testing of GRP bolts with conventional DCP steel bolts. The axial load performance, including stiffness, ultimate capacity and ductility of bolts are compared. Shear behaviour of bolts is considered, including durability issues associated with damage to the plastic sleeve used in DCP bolts.The paper also considers other issues which are relevant to the design of temporary and permanent rock bolts used in tunnel support, such as initial tensioning and grouting. Long-term performance, including durability and creep are also reviewed.CITATION:Clarke, S J and Sieders, G, 2014. Comparison of glass-fibre reinforced polymer rock bolts with double corrosion protection steel rock bolts for use in tunnel applications, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 237–246 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014