Spyridis P.,Dr. Sauer and Partners |
Gakis A.,London office of Dr. Sauer and Partners |
Bedi A.,Imperial College London
Tunnels and Tunnelling International | Year: 2013
The intention of this paper has been to present numerical modelling for tunnelling from a less academic, more practical point of view and to provide some useful concepts and insights for engineers. As a summary, the following points are recommended: ■ Even the most sophisitcated numerical model is incapable of giving an exact answer. Numerical models do have limitations, and peril to the project lurks when the results of a model are trusted blindly. However, when the limits of the model are understood, numerical solutions can yield veiy useful information. As with most tasks, we need to know what we know, but we must also know what we don't. ■ Models are but mathematical calculations based on fundamental laws of physics and engineering theories. Engineers should always question and challenge their models up to the point they are able to explain and defend the results based on theory and/or experience. Confidence in the analysis results should arise from agreement with relevant past experience, cross checking with analytical or simplified numerical solutions, and above all common engineering sense. ■ Modelling engineers should know the 'habits' of the software they are using, its pros and cons, and to develop a thorough checklist that simplifies the modelling and moreover the debugging process. Note also, in a poorly constructed model, debugging may take up to 90 per cent of the overall effort. ■ Decisions on the analysis approach need to be aligned with the characteristics of the project team. It is sometimes preferable, depending on the capacities of the parties involved, to use simpler models (e.g. simple constitutive laws) that are better understood and communicated. Numerical models are built in order to support a pre-specified engineer's decision and they should be understood in this context. This, when balanced with the project budget can lead to an efficient analysis campaign. Copyright © 2013 Caterpillar.
Wilhelmstoetter F.,Dr. Sauer and Partners |
Karner C.,Dr. Sauer and Partners
ITA-AITES World Tunnel Congress 2016, WTC 2016 | Year: 2016
The Confederation Line is phase one of Ottawa's light rail transit, which consists of 13 stops and stations. The project's center piece is a 2.5 kilometer (1.6 miles) long tunnel with three underground stations leading underneath downtown Ottawa and is constructed within feet of adjacent buildings. The downtown stations, Lyon and Parliament, are caverns approximately 16.5 m (54 ft) by 18 m (59 ft) in a horseshoe configuration constructed in rock, while the third station, Rideau, is approximately 22 m (72 ft) by 18 m (59 ft) in an oval configuration and constructed in mixed ground. The paper will discuss design decisions made early on in the project such as excavation method, unique construction sequencing, and equipment selection, and go on to include corresponding progress rates. The paper also documents design and construction challenges of large caverns in very close proximity to existing buildings and varying ground conditions. Finally, an overview of achieved construction milestones and a current construction progress will be presented. Station cavern excavation is expected to be completed in early 2016. Copyright © (2016) by the Society for Mining, Metallurgy and Exploration. All rights reserved.
Feiersinger A.,Dr. Sauer and Partners |
Mitsch T.,Dr. Sauer and Partners |
Spyridis P.,Dr. Sauer and Partners
Life-Cycle and Sustainability of Civil Infrastructure Systems - Proceedings of the 3rd International Symposium on Life-Cycle Civil Engineering, IALCCE 2012 | Year: 2012
The London Underground system is not only the oldest of its kind worldwide, but also one of the busiest, serving approximately a billion passengers annually. Both of these characteristics induce an accelerating necessity for maintenance and rehabilitation of the present infrastructure, which of course includes the upgrading and extension of existing underground stations. Next to that, especially with London being one of the most condensed regions in the world, influence of tunneling works on the built environment can hardly be overmatched. This poses a huge challenge for the designer, who comes to develop an appropriate balancing solution that guarantees, apart from the new structure's safety, the functionality and structural integrity of the existing neighboring structures and surrounding assets and utilities. In that sense, the design is strongly dependent on the different life-cycle stages of the individual elements within the same system due to the varying construction types, building standards and philosophies, varying ages and maintenance levels, and socioeco-nomic priorities. For this challenge to be confronted in practice, prediction of deformations during construction is a key-agent, whereat the successful combination of three main features can be signified: (a) advanced finite element modeling, (b) expertise-based assumptions, and (c) response monitoring of the existing assets throughout the entire project execution phase. These critical aspects of urban tunneling are discussed on the basis of the accomplishment of the London Underground's Green Park station extension and upgrading project, while the experience gained from the completion of this project may provide a solid reference for future cases.
Gakis A.,Dr Sauer and Partners |
Salak P.,Dr Sauer and Partners |
St. John A.,BFK Joint Venture
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2015
Following the construction of the Crossrail Project, Farringdon will become one of Britain’s busiest train stations connecting three major networks - Thameslink line, Crossrail and London Underground. The station tunnels are constructed using sprayed concrete lining techniques. The geotechnical conditions were the principal challenge, governing both design and construction processes. The tunnels were excavated mainly within the Lambeth Group, a formation comprising various units, mainly stiff to very stiff overconsolidated clays with interbedded sand lenses of unknown size, hydraulic properties and continuity. Moreover, four major geological faults cross the footprint of the station, effectively changing the position of the risk-imposing sand lenses in relation to the tunnelling works. A robust and innovative geotechnical risk management approach was adopted from the design to the construction phase, utilising additional surface investigation, in-tunnel investigation and a ‘live’ three-dimensional ground model. This provided a framework for effective on-site decision making and a cycle of risk reduction related mainly to the presence of multiple faults and potentially high water pressures within sand layers at the tunnel face. This approach is demonstrated in various stages of the project. This ‘best practice’ model could be applied to other projects with challenging geotechnical conditions © 2015, Thomas Telford Services Ltd. All rights reserved.
Spyridis P.,Dr. Sauer and Partners |
Nasekhian A.,Dr. Sauer and Partners |
Skalla G.,Dr. Sauer and Partners
Geomechanik und Tunnelbau | Year: 2013
The underground metropolitan transport network of London is not only the oldest worldwide, but also one of the busiest, serving approximately a billion passengers annually. Both of these characteristics induce an accelerating necessity for new infrastructure as well as maintenance and rehabilitation of the present infrastructure, which of course includes the upgrading and extension of existing underground stations. Next to that, especially with London being one of the most condensed regions in the world, influence f tunnelling works on the built environment can hardly be matched. A huge design challenge is then to develop an appropriate balancing solution that guarantees, apart from the new structures' safety and functionality, the operational and structural integrity of the existing neighbouring structures and surrounding assets and utilities. Under these circumstances, Sprayed Concrete Lining (SCL) structures are very often a preferable option, due to the flexibility in geometries and the ability to regulate the impacts on surrounding structures during construction. This paper aims to present the status of London transport infrastructure and recent important initiatives towards its improvement (i.e. the LU upgrade plan and the Crossrail project), the sensitivities and particularities of underground sprayed concrete constructions in London, and an outline of case histories from Dr. Sauer and Partners (DSP) involvement in respective projects, namely the London Underground Green Park Station, the Bond Street Station, and the Tottenham Court Road Station upgrades and the Crossrail Farringdon Station, the Limmo Auxiliary Shaft and the Independent Category-3 design checks of the Crossrail project. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.