Artikeldatenbank
Autor(en) | Titel | Zeitschrift | Ausgabe | Seite | Rubrik |
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Suchmann, Christoph; Fuchs, Christian | Intersection U2xU5 - Tunnelling works at the lot U2/22 / Linienkreuz U2xU5 - Tunnelbaumaßnahmen am Bauabschnitt U2/22 | Geomechanics and Tunnelling | 5/2021 | 477-488 | Topics |
KurzfassungThe next expansion phase of the U2xU5 intersection is currently under construction in the inner districts of the City of Vienna. The construction lot U2/22 Rathaus (City Hall) takes place in the inner districts 1, 7 and 8. Three shafts are the main focus of the construction works at Friedrich-Schmidt-Platz, directly behind the Vienna City Hall as well as a shaft with extensive works on the building of the University of Vienna and another shaft at Josefstädter Straße. Due to difficult and changing geology, different support measures from full face tunnel excavation to tunnelling under a roof of jet grouting piles will be used. In addition, measures such as groundwater drainage, structural improvements of buildings and settlement compensations are necessary in advance. x | |||||
Hochart, Arnaud; Vialle, Denis | Innovative slurry solutions for demanding TBM drives through soil with high permeability in a dense urban area | Geomechanics and Tunnelling | 5/2021 | 489-500 | Topics |
KurzfassungThe extension of the Metro B line in Lyon represents a technical challenge combining difficulties with very few equivalents in pressurised TBM history. Alluviums with wide porosity and high permeability (up to 10-2 m/s) imply a risk of slurry loss leading to ground instabilities. To mitigate geological risks without using heavy ground treatment, two lines of research were followed: x | |||||
Schröfelbauer, Thomas; Permanschlager, Katrin; Montag, Oliver; Avender, Thomas | S1 Tunnel Donau-Lobau - The complex path to geological exploration in the Donau-Auen National Park / S1 Tunnel Donau-Lobau - Der komplexe Weg zur Baugrunderkundung im Nationalpark Donau-Auen | Geomechanics and Tunnelling | 5/2021 | 501-509 | Topics |
KurzfassungThe S1 Donau-Lobau tunnel closes the gap in the road network around Vienna. Its two tunnel tubes run under the Danube and the Donau-Auen National Park, with the provision that no work is allowed to take place on the surface of the site. The (hydro-)geological subsurface conditions in the project area can be described as “difficult”. The tunnel project must also meet all safety-related requirements that arise during construction and operation, while at the same time minimizing the environmental impact. x | |||||
Gächter, Werner; Exenberger, Hans; Fasching, Alfred; Hillisch, Stefan; Mulitzer, Günther; Seywald, Martin; Rettenbacher, Martin; Fröch, Georg; Flora, Matthias | Possible applications for a digital ground model in infrastructure construction / Anwendungsmöglichkeiten eines digitalen Baugrundmodells im Infrastrukturbau | Geomechanics and Tunnelling | 5/2021 | 510-520 | Topics |
KurzfassungThe BIM pilot project “New Köstendorf-Salzburg Line” for ÖBB-Infrastruktur AG covers a new twin-track section about 21 km long involving a wide variety of different engineering structures and a corresponding need for close interdisciplinary collaboration within a sensitive project space. The pilot project successfully achieved its objective of generating a largely software-independent overall model and transferring the knowledge gained to the Employer's Information Requirements and subsequently to a BIM execution plan. In addition to internal coordination meetings, a preliminary external meeting took place to discuss the model elements required for a government agency as part of an approval process and the availability of such elements by means of direct access to the model. x | |||||
Mesic, Muhamed | New insights into the contractual subsoil risk - A view beyond the Austrian horizon / Neues zum Baugrundrisiko - Ein Blick über den Tellerrand | Geomechanics and Tunnelling | 5/2021 | 522-528 | Topics |
KurzfassungDifferent approaches have emerged in dealing with the subject of subsoil risk over the last 25 years. The complex area of geotechnical engineering has contributed significantly to the problem through the development of new technologies. A contractually correct “absorption” of the external conditions has thus become an increasing challenge. This paper describes some of the more recent developments on the subsoil risk, not least in the delimitation to other contractual risks and the contractual arrangement of risk allocation. The topic has also provided for interesting approaches outside Austria, which are also discussed here. The aim is to provide new impulses for dealing with the subsoil risk. x | |||||
Purrer, Walter | Dispute adjudication in Austrian conditions of contract for underground works / Der TSV im Spannungsfeld von Baugrundrisiko und Sphärentrennung | Geomechanics and Tunnelling | 5/2021 | 529-536 | Topics |
KurzfassungThe institution of a neutral Tunnelling Expert (TE) has proven to be of benefit to Austrian Tunnelling Projects. However, misdevelopments have been observed during recent years, which lead to setbacks and obstructions against utilizing its full potential. On the basis of practical experiences, the reasons and backgrounds are explained and options for improved collaboration of the participants by targeted involvement of the TE are shown. These considerations are not restricted to structural topics. They also take into account the mechanism of the social system of manpower cooperating in construction projects, x | |||||
Weh, Markus | Dealing with geological risk in Switzerland - Mix shield TBM on the Eppenberg tunnel site, field report / Umgang mit dem Baugrundrisiko in der Schweiz, Erfahrungsbericht zum Vortrieb einer Mix-Schild-TBM auf der Baustelle Eppenbergtunnel | Geomechanics and Tunnelling | 5/2021 | 537-546 | Topics |
KurzfassungOn the mix-shield TBM excavation of the Eppenberg tunnel, unexpected conditions were encountered in both the rock and soil excavations, which resulted in a modified execution of the project. In this case, the openly formulated contract made it possible to take advantage of improvements in the ground and to manage unexpected system behaviour with the right measures in such a way that economical and time-saving excavation was possible. In all three examples presented in this paper, time is one of the key success factors, because recurring processes result in feedback processes that change the system behaviour more and more rapidly as time goes on. In order to reduce the resulting additional costs and time losses, it is necessary to understand what is happening on site, then evaluate, test and check the possible measures, and finally decide on their implementation in a timely manner. At Eppenberg tunnel, this enabled unexpectedly adverse system behaviour to be overcome in two cases without any major loss of construction time. This was only possible because the responsible persons from all parties involved were able to discuss the situation together and make decisions at short notice. x | |||||
Sellner, Peter Johann; Pacher, Wolfgang; Weinmar, Wolfgang; Moser, Herwig; Monsberger, Yvonne | Impact of alternative tunnelling procedure on contractual allocation of ground risk at S 7 motorway Tunnel Project Rudersdorf / Alternatives Vortriebskonzept - Verlagerung des Baugrundrisikos beim Tunnel Rudersdorf | Geomechanics and Tunnelling | 5/2021 | 547-556 | Topics |
KurzfassungThe approx. 3 km long twin-tube Rudersdorf tunnel is part of the Fürstenfeld Motorway S7. In addition to jet grouting and steel pipe umbrella sections, the excavation is mainly carried out according to the NATM. After the contract had been signed, the contractor proposed a value engineering concept including a stepped (almost) full excavation with a short ring closure. This concept avoids jet grouting sections and reduces sections with steel pipe umbrellas and the temporary top heading invert. A fair risk transfer between both contractual partner enables the full technical and economic potential of the project to be released and guarantees a win-win situation. The modified construction methodology consequently also requires a change of tasks and responsibility for the contractual partners for the project. This paper highlights the main topics of the contractual modifications required and explains the handling of the ground risk with examples. x | |||||
Steiner, Walter | Geotechnical processes at the tunnel face - The key to successful tunnelling / Erkennen geotechnischer Vorgänge an der Ortsbrust als Schlüssel zum erfolgreichen Tunnelvortrieb | Geomechanics and Tunnelling | 5/2021 | 557-568 | Topics |
KurzfassungWhen tunnelling with a TBM (Tunnel Boring Machine) in rock and soil, mostly the machine is described and often reduced to a slogan. Such descriptions say little about geotechnical processes at the tunnel face that are key to the success of tunnel driving and must be considered when selecting a tunnelling system. In soil tunnels the tunnel face must be safely supported and extracting material must be possible. For a slurry shield the slurry must not escape and pressure must act on the face. In the literature mostly bentonite content is considered. With an Earth-Pressure balance machine the soil has to have characteristics that it can be remoulded and transformed in a mass of adequate consistency with mechanical means, adding water and additives such that this mass can support the face and be extracted. Long-term experience shows that the fine content and polymers are also important factors. Flow channels (pores) in open gravel may be clogged, and the face supported by seepage forces. Also, the drag forces in the slurry circuit are increased and the operation of the slurry circuit became more stable. Rates of advance exceeding 10 m/day were achieved with a 11.6 m slurry shield. The limited depth of penetration of the slurry could be determined in-situ. For fine-grained soils the characteristics of the fines are crucial and are described by the Atterberg limits. Soil mechanics strength properties may be vastly different. x | |||||
Jukes, Simon; Schenk, Stephan | Feeder 9 Gas Pipeline Replacement Tunnel - Achieving a world record for pipe insertion of a new gas pipeline within a tunnel beneath the river Humber (UK) | Geomechanics and Tunnelling | 5/2021 | 569-573 | Topics |
KurzfassungSince December 2020, at a pressure of 70 bar, up to 25 % of Britain's gas requirements was flowing through the new Feeder 9 gas pipeline, which installed in a 4.9 km long tunnel 30 m below the River Humber. With the insertion of the new pipeline, the Humber Pipeline Joint Venture (HPT JV), consisting of the companies Porr, Skanska and A. Hak, achieved a major milestone when it was officially recognised as a Guinness World Record for the longest hydraulically-inserted pipe at 4,963.7 m long. Replacing the existing pipeline was an absolute necessity due to the shifting river bed which, over the years, had exposed sections of the pipeline threatening the supply to the customers in the UK. The solution adopted by the client, National Grid to provide a long-term permanent solution, was for the construction of a segmental lined tunnel with an inner diameter of 3.65 m accommodating the new 1050 mm diameter welded steel gas pipe. The tunnel was excavated with a 4.4 m diameter mix shield type TBM. The small diameter together with the length, without intermediate access including a tidal range in the Humber estuary of up to 6.4 m and an overburden on the tunnel of 10 m below the river bed resulted in a number of challenges. The installation of the concrete-coated steel pipeline was particularly high risk. The individual strings ranging from 595 to 620 m in length and weighing about 850 t, were pushed consecutively into the water-filled tunnel employing two hydraulic thrusters in just 18 days. x | |||||
Bäppler, Karin; Battistoni, Frédéric; Burger, Werner; Flora, Matthias; Schwärzel, Matthias | Initial project experiences with variable density TBMs in Europa - Extension of the Lyon metro line B / Erste Projekterfahrungen mit Variable-Density-TVMs in Europa - Erweiterung der U-Bahnlinie B in Lyon | Geomechanics and Tunnelling | 5/2021 | 574-583 | Topics |
KurzfassungGlobalisation and advancing urbanisation around the globe have a significant influence on market dynamics in tunnelling. The expansion of infrastructures in urban and regional centres calls for the construction of new transport, supply, and disposal systems to link individual economic centres. Innovative technologies in mechanised tunnelling, such as the now well-established Variable Density TBM, are making a significant contribution to the safe and low-settlement construction of sustainable tunnel infrastructure projects in extremely challenging and variable ground conditions. In this publication, the current developments and design features as well as the application areas of the Variable Density Technology are addressed, based on one of the first project experiences in Europe, in Lyon. x | |||||
Tintelnot, Götz; Koch, Michael | Injection materials in tunnel excavation material - Waste or substitute construction material? / Injektionsstoffe im Tunnelausbruchmaterial - Abfall oder Ersatzbaustoff? | Geomechanics and Tunnelling | 5/2021 | 584-591 | Topics |
KurzfassungThis paper examines the possibility of using excavated material with system-related admixtures as a substitute construction material, considering the current rules and regulations in the field of landfilling or disposal. In addition to conventional injections with bentonite- and cement-containing suspensions, which always require longer setting times and are relevant for classification during disposal with sulfate values in the eluate, fast-setting multicomponent resins are suitable for filling or consolidation, e.g. fast-reacting, high-foaming silicate resins, polyurethane resins for stopping water ingress, or rubber-elastic, versatile 3-component acrylate gels. However, the discussion is currently focusing on tunnelling compounds to which foams or resins have been added and which, according to Systal's “system-related admixtures”, are to be remunerated as special services. This paper deals with the question how to deal with the excavated material contaminated with organic matter under soil protection law and waste law. On the basis of the results of laboratory tests, the question arises as to whether tunnel excavation with a few percent of organic, system-related admixtures would not make an excellent substitute building material in the sense of the draft substitute building materials ordinance. x | |||||
Flora, Matthias; Weiser, Torsten; Zech, Philipp; Ruepp, Anna; Bergmeister, Konrad | Added value in mechanized tunnelling by intelligent systems / Mehrwerte im maschinellen Tunnelvortrieb durch intelligente Systeme | Geomechanics and Tunnelling | 5/2021 | 592-599 | Topics |
KurzfassungBoth conventional and mechanized tunnelling have a fantastic tradition. The technical progress of the industry moved in step with social developments, characterized by crises and leaps in innovation. In the field of mechanized tunnelling, the driving force for some years now has been the desire to excavate heterogeneous construction sites with changes in tunnelling modes without the need for costly conversions underground. In addition, two innovation surges are currently discernible. On the one hand, the demands on innovation and technology management again follow a societal challenge, namely the goal of climate neutrality. On the other hand, digital processes and tools are changing all areas of our lives at an enormous speed, which means that the construction industry will also undergo a transformation in the coming years. Automation, robotics, the Internet of Things, machine learning, or artificial intelligence are all gradually encroaching on current processes and methods. x | |||||
Türtscher, Matthias; Mark, Simon; Leitner, Wolfgang; Innerhofer, Guntram | "Flying" start with gripper TBM in flat and inclined shaft / "Fliegendes" Andrehen mit einer Gripper-TBM in Flach- und Steilstrecke | Geomechanics and Tunnelling | 5/2021 | 600-608 | Topics |
KurzfassungContractor G. Hinteregger & Söhne Baugesellschaft mbH submitted an alternative proposal for the “Rodundwerk I, new headrace and distribution pipe system” project commissioned by Illwerke vkw AG which uses a new launch structure for an open gripper TBM. An Austrian utility model has been registered for this new development. This paper describes the process. x | |||||
Dickmann, Thomas; Hecht-Méndez, Jozsef; Krüger, Dirk; Sapronova, Alla; Unterlaß, Paul Johannes; Marcher, Thomas | Towards the integration of smart techniques for tunnel seismic applications | Geomechanics and Tunnelling | 5/2021 | 609-615 | Topics |
KurzfassungApplications of seismic measurements for the prediction of hazard zones are applied practice in many tunnel drives in rock mass today. Next to a large exploration range and accurate localisation of discontinuities, seismic data provide attributes for a comprehensive characterisation of the ground conditions. A good synchronisation of all technical components is required to obtain optimum data quality and quantity while the tunnel excavation is not obstructed thereby. Firstly, the signal source must feed as much energy as possible into the rock in a very short time. Secondly, continuity of the signal generation with constant quality and its precise timing by means of wireless data transmission also ensure a reliable measurement process. Artificial intelligence is used to determine the quality of the recorded data already in the tunnel and feedback is given to the user keeping the data quality high. From the tunnel site, recorded raw data can be transferred to a cloud, from where an authorised processor collects them, wherever in the world. An immediately started data processing delivers a result within an hour that includes a geological forecast of up to 150 m of heading, depending on the rock mass condition. In addition to data quality, the quality of the results is crucial. Therefore, techniques are currently under development using machine learning to correlate and analyse seismic attributes with geological properties. This should lead to a more objective evaluation of the geological forecast in the future. x | |||||
Chwatal, Werner; Domenig, Angela; Kostial, Dieter; Rudel, Thomas; Schlögel, Günter; Wagner, Hanns | Review of the "Tunnel Seismic While Drilling" measurements during construction of the Koralm Tunnel at section KAT2 / Erkenntnisse aus den "Tunnel Seismic While Drilling" Messungen während des Vortriebs am Koralmtunnel Baulos KAT2 | Geomechanics and Tunnelling | 5/2021 | 616-625 | Topics |
KurzfassungThe 32.9 km long Koralm tunnel (Austria) is the core piece of the Koralm railway and will be one of the longest railway tunnels worldwide after completion. At the longest construction section “KAT2” two approx. 17 km long parallel single-track tunnels were driven by two double-shield tunnel boring machines with a diameter of about 10 m. Accompanying the tunnelling of the two tubes, the continuous Tunnel Seismic While Drilling (TSWD) method was used shortly after the start of mechanical excavation in January 2013 until the final position was reached in February 2018. The aim was to consistently explore the rock mass up to 100 m in front of the tunnel face to detect faults and water-bearing zones which were relevant for tunnel construction. Another purpose of the measurements was to reduce the number of exploration drillings ahead of the tunnel face. After an initial test phase of about 5000 m, where exploration drillings were continuously carried out parallel with TSWD, an advanced and optimized exploration concept was evaluated and performed for permanent operation. This paper summarizes the findings gained from the TSWD measurements at this tunnel site. x | |||||
Kratz, Thorsten; Vogel, Guido; Ouschan, Michael | Combined exploration drilling with digital data management / Einsatz kombinierter Bohrverfahren zur Vorauserkundung mit digitalem Bohrdatenmanagement | Geomechanics and Tunnelling | 5/2021 | 626-636 | Topics |
KurzfassungThe purpose of exploration drillings in tunnelling operations is to investigate rock structure, geological composition of the rock, especially with regard to fault zones, and the identification and characterisation of water-bearing zones. When determining the quality of exploration, the economic parameters must be taken into account. The application of combined exploration drilling methods allows the successful drilling of exploration drillings even in complex geotechnical and hydrogeological rock conditions. The concept provides the flexibility to switch between drilling systems and to realise probe measures tailored to the specific geology quickly and according to economic requirements. For successful exploration projects, documents and findings from past projects are used in the planning phase. The use of digital drilling data management offers enormous potential for optimising data evaluation. The determination of machine, equipment and the preparation of a drilling plan can thus be prepared much more specifically for the upcoming exploration. During execution, direct conclusions can be reached regarding e.g. drillability or drilling tool condition on the basis of the process-oriented process analysis. x | |||||
Schmidt, Markus; Zenz, Reinhard; Richter, Thomas | Innovative geophysical exploration technologies in karst-prone and crystalline rock formations / Innovative geophysikalische Vorauserkundungstechnologie in verkarstungsfähigen und kristallinen Gesteinen | Geomechanics and Tunnelling | 5/2021 | 637-652 | Topics |
KurzfassungIn rock formations prone to karstification there are only limited geological/hydrological principles that allow a safe prognosis of the existence and location of karstic and fault structures. A combination of geophysical borehole radar measurements utilizing both reflection and crosshole probe setups can be used to reliably detect anomalous structures, especially air-filled karstic cavities and fault zones, when a sensible measuring concept for karstified or crystalline rocks is applied. Besides the determination of the anomalous structure's location it is also possible to distinguish its type of filling. Using examples from the major railway project Albaufstieg between Wendlingen-Ulm the investigation concepts ahead of the tunnel construction are presented. The borehole radar measurements were successfully utilized during different phases of the tunnel excavation and could be integrated into the construction process without significant delays, thus contributing to a safe construction process and later operation of the tunnels. The reliability and high efficiency of these borehole radar investigation concepts places this technology of karst detection at a significant advantage over the commonly applied seismic methods, especially in karst-prone and crystalline rocks. x | |||||
Radinger, Alexander; Hofmann, Thomas; Holzer, Robert; Fasching, Florian; Kusnirak, David | Highly specialized geophysical methods for undergroud construction works - Semmering Base Tunnel, a practice report | Geomechanics and Tunnelling | 5/2021 | 654-660 | Topics |
KurzfassungThe use of geophysical methods for the planning of complex underground structures such as deep tunnels has made significant progress in the last two decades. The realization of large underground construction projects in complex geological environments has led to an increase of geophysical exploration during excavation activities, drilling, and geological documentation. The aim is to continuously update and improve the geological model in order to identify and mitigate potential risks. Flexible planning of geophysical measurements and their fast and efficient implementation are required to minimize the impact on ongoing construction works. x | |||||
Hartl, Irene; Schlögel, Ingrid; Behm, Michael; Wenighofer, Robert; Galler, Robert | Alternative seismic sources for exploration in conventional tunnelling / Alternative seismische Quellen für die Vorauserkundung im konventionellen Tunnelbau | Geomechanics and Tunnelling | 5/2021 | 662-670 | Topics |
KurzfassungFor seismic ahead-of-the-face prediction in tunnelling, sources with known properties are usually used, which, however, are not compatible with NATM. In order to integrate geophysical exploration into conventional tunnelling, the feasibility of construction machinery for generating seismic source signals was investigated. Passive monitoring during conventional tunnelling was used to analyse the seismic signals. Different radiation characteristics of drilling, blasting and bouldering could be identified and their characteristics regarding range and spectrum of the signal could be determined. In subsequent system tests, various machines used in NATM tunnelling were examined for their suitability as sources. The sensor positioning for source signal pickup was evaluated by stroke tests and during ongoing tunnelling operations. For the registration of the waves in the rock mass, different receivers with different geometries were used to characterize the wave field emitted to the front or side of the sources. In addition, the necessary processing steps were determined in order to make these signals usable for an ahead-of-the-face exploration. The results and data form a basis for further development into a practical technical solution for conventional tunnel construction. x | |||||
Thomas, Alun; Bernard, Erik Stefan | Developments in fibre reinforced concrete in tunnelling | Geomechanics and Tunnelling | 4/2021 | 333-339 | Topics |
KurzfassungThis paper will provide an overview of the state of the art of the use of fibre reinforced concrete in tunnelling. The major applications for fibres are for the reinforcement of sprayed concrete and pre-cast concrete segmental linings, but fibre reinforcement is also increasingly used for other applications such as trackbed/trackslab and minor precast concrete elements such as cable ducts, drip shields, and drainage elements. As the technology has matured, a wide variety of fibre types, made from different materials, has emerged. Standards have been developed for the manufacture, testing and application of all these fibre types. Moreover, design guidelines and codes have been published and new design methods are still being developed. The International Tunnelling Association has published several guidance documents in this field. Last but not least, FRC has an important role to play in reducing the carbon footprint of tunnelling projects. x | |||||
Thomas, Alun | The design of the Crossrail tunnels in UK | Geomechanics and Tunnelling | 4/2021 | 340-346 | Topics |
KurzfassungThis paper will focus on the use of fibre reinforced concrete on the Crossrail project in the UK. Crossrail (now named The Elizabeth Line) is a new railway running from West to East under the centre of London. This railway runs for approximately 14 km underground and five of the new stations were constructed with permanent sprayed concrete linings. Fibre reinforced concrete played a prominent role in all of the tunnelling - both for the segmental linings and the sprayed concrete tunnel (SCL) linings. Having reviewed the context of the project and the state-of-the-art in tunnel design at the time of the design, this paper will describe the design approach for both the TBM and mined tunnels and their fibre reinforced linings. While the segmental lining design followed a conventional approach, the SCL tunnels adopted an innovative design with the first major application of permanent sprayed concrete in the UK and featured the first use of a spray applied waterproofing membrane (SAWM) on a major project in Europe. Performance during construction will be reviewed and conclusions will be drawn on what can be learnt from the mega project. x | |||||
Horny, Ulrich; Bayer, Lars; Schiesser, Karl; Kliem, Olaf | Metro Doha Green Line: Fibre reinforced tunnel linings - Design and construction experience | Geomechanics and Tunnelling | 4/2021 | 347-355 | Topics |
KurzfassungThe Design and Build project “Metro Doha Green Line Underground” has been awarded to a joint venture composed of Porr, the Saudi Bin Ladin Group and HBK in summer 2013. It contains the “ready to use” construction of the underground part of the Green Line with 2 × 17 km tunnels, six stations, switching areas as well as cross passages and emergency exit shafts. The 34 km of tunnelling, realized with six EPB machines simultaneously, have been completed in only 18 months. The main impact on the determination of the design and build specification in terms of the segmental ring design is based on the extraordinary geological environment properties of the project area of Doha City. The geology is characterized by a dominating 3-rocklayers system comprising massive upper and lower limestone deposits, which are commonly separated by a thin shale layer. Additionally, and in regard to the nearby located sea-side the type of identified aggressive exposure conditions relevant to the concrete segment lining in terms of significant sulphate and chloride impact requires a durable reinforcement solution fit for required 120-year service life. Especially due to chloride attack an ordinary steel bar reinforcement system including a projected 90 mm nominal concrete cover at lining's intrados and extrados turns out statically difficult and constructionally non-practicable. Therefore, steel fibres are chosen to meet the strict design constraints. x | |||||
Zeuli, Vincenzo; Maier, Christof; Diaz, José Manuel Suarez; Saeed, Fahed Ahmed; Tharamapalan, Jayapregasham; Germani, Carlo; Bayer, Lars; Atzl, Georg | Structural design of precast segmental lining reinforced by steel fibres | Geomechanics and Tunnelling | 4/2021 | 356-366 | Topics |
KurzfassungDubai Municipality awarded to Porr Besix JV the Project for the Main Tunnel component of the Deep Storm Water System. The tunnel will collect both rainwater and groundwater from approximately 500 sq. km and transfer the captured flow to the sea. The Design Builder JV selected COWI as Designer of the entire Project and IC Consultant as Design Checker for the Tunnels. The Project includes approximately 10.3 km of 10-meter-inside diameter tunnel in rock, three construction shafts and one drop shaft. The main tunnel will convey stormwater and groundwater flows from the EXPO 2020 area near the intersection of Sheikh Mohammed Bin Zayed Road and Jebal Ali Lehbab Road to the sea close to the EGA facility. The tunnel will follow beneath the road easement along Jebal Ali Lehbab Road and along Sheikh Zayed Road and continue to the pumping station. The tunnel traversed through the Barzaman and Fars formation with an overburden of 33 m with maximum water pressure of 4.4 bar and was excavated by EPB TBMs. This project is characterized by its dimensions with an internal diameter of 10 m and 350 mm of segment thickness, and by the use of steel fibre reinforced concrete in the precast segmental lining. The use of fibres aims to reduce the CO2 footprint obtaining an optimized design from the environmental point of view. These facts are associated to a complex design of precast segments, in order to ensure their structural competence and their integrity according to the durability requirements, under large thrust forces (temporary loads) and permanent load. Hence, considering such complexities, the structural design has been carried out producing a 3D structural model by means of a sophisticated FEM structural software. Results of the model allow to identify areas of the segment where spalling and bursting stresses are generated along circumferential joints and maximum value of those stresses in the temporary load cases. Moreover, a structural design verification of the segment has been undertaken considering the contribution of steel fibres class 4c, as it is set up in the FIB model code, aiming to ensure that the precast segments are structurally competent and fulfil the durability requirements of the Project. The article details the design approach and the independent checker design verification approach. The experience gained during construction is also reported, describing challenging aspects of the Tunnel execution and an analysis of the lining damages. x | |||||
Laubbichler, Jürgen; Schwind, Thomas; Gakis, Angelos; Sanz, Alejandro; Soto, Francisco | Advanced design of large cavern intersections in soft ground without conventional bar reinforcement | Geomechanics and Tunnelling | 4/2021 | 367-376 | Topics |
KurzfassungThe design of three mined stations in Toronto as part of the Eglinton Crosstown Light Rail Project involved several intersections of large tunnels situated in the heterogenous, water-bearing glacial till deposits. The most challenging openings, 220 m2 each, were formed in the two sides of the 18 m high cross-cut tunnels to allow the excavation of the 18 m wide platform caverns. A key objective for the design was the optimization of the tunnel shapes and the advanced simulation of the fibre reinforced shotcrete properties, to allow these openings in the initial tunnel linings to be achieved without conventional bar reinforcement or thickenings, thus simplifying and accelerating the construction, whilst reducing health and safety risks. x |