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Spyridis P.,Dr. Sauer and Partners Ltd. | Feiersinger A.,Dr. Sauer and Partners Ltd. | Nasekhian A.,Dr. Sauer and Partners Ltd.
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2014

The London Underground transportation system (the Tube) celebrated its 150th anniversary in 2013. It is not only the oldest of its kind worldwide but also one of the busiest, serving more than 1,2 billion passengers annually. Considering the huge socioeconomic value of the city's building stock and subsurface infrastructure, as well as the conditions of confined space, the design and execution of urban tunnelling projects pose significant engineering challenges. Accomplishment of such projects relies on a combination of design, construction, and structural monitoring exercises. This report aims to showcase aspects of project execution in this environment, focusing on the preservation of structural and functional integrity in the interaction of new and existing structures, based on experiences from a recently delivered project, namely tunnelling works for the Tottenham Court Road Station Upgrade in central London. The station upgrade will be fully complete by 2016. Two of the new entrances, the new ticket hall and the new Northern line access, will open in 2015 and be ready to connect to the Crossrail platforms when they open in 2018, via a shared ticket hall and a fivestorey underground interchange.

Spyridis P.,Dr. Sauer and Partners Ltd.
Tunnelling and Underground Space Technology | Year: 2014

Tunnels typically comprise large scale infrastructure projects, where a demand for an increased service life is present. The most recent large scale projects in the UK come with a requirement for a service life of 120. years. At the same time, the implementation of Eurocodes is becoming standard practice, the current provisions of which cover a service life of 50. years. On the other hand, temporary structures often do not need to be designed for a service life longer than a few years only. The present paper discusses a reliability life-cycle based methodology to adjust safety factors used in the design of tunnel linings in order to reach a specified service life, i.e. a variation of the safety factors used leading to an analogous reliability level at the start of the structures lifetime, which in turn provides a modification of the expected service life duration. As discussed herein, this procedure does not conflict the Eurocode provisions (one of the most referred standards in tunnel design) but it comes in line with the safety concept indicated in Eurocode 0 "Basis of Design". © 2013 Elsevier Ltd.

Gakis A.,Dr. Sauer and Partners Ltd. | Flynn S.,Dr. Sauer and Partners Ltd. | Nasekhian A.,Dr. Sauer and Partners Ltd.
North American Tunneling - 2014 Proceedings, NAT 2014 | Year: 2014

The Crossrail Farringdon Station is a deep level station with two platform tunnels, 300 metres long with the tunnel axis being at a depth of approximately 30 metres below street level, linked by means of eight cross passages and two concourse tunnels. The platform tunnels will be enlarged from the TBM bored Crossrail running tunnels using sprayed concrete lining (SCL) tunnelling method, after the removal of the TBM segments. The station is located in challenging ground conditions due to the presence of several faults and the heterogeneity of the Lambeth Group, which call for a variety of temporary works contingency measures and in-tunnel depressurisation scheme. Back analyses for the already constructed cross passage CP1 were performed using finite element (FE) analysis in order to calibrate them against observed deformations, deriving valuable information for future design of similar SCL tunnels. The accuracy of assumptions made in the initial design stages had to be checked and such parameters as ground relaxation factor for construction advance, at rest earth pressure coefficient and soil stiffness were back-calculated and compared with the initial values. The result of this work is refined FE modelling input parameters calibrated against measured deformation results, which demonstrated a greater accuracy for predicting both, in-tunnel and surface deformations and thus allowing for a better understanding of the soil-structure interaction to be anticipated in the remaining stages of SCL tunnel excavation for the completion of the project.

Lyons B.,Dr. Sauer and Partners Ltd. | Kumpfmueller S.,Dr. Sauer and Partners Ltd. | Sleath M.,Atkins Ltd. | Terry D.,Costain Laing ORourke Joint Venture
North American Tunneling - 2014 Proceedings, NAT 2014 | Year: 2014

Bond Street station is undergoing a major upgrade to increase capacity, improve accessibility and create interchange with the new Crossrail station. It is one of the most complex sprayed concrete lining (SCL) tunnel design projects undertaken by London Underground. The design has had to address challenging connections to and interfaces with the existing infrastructure requiring the use of binocular sections, an underpass tunnel and a large cruciform junction. This has required significant design effort, maximizing innovation and utilisation of the latest technology including the use of fibre reinforced sprayed concrete for both the primary and secondary linings.

Gakis A.,Dr. Sauer and Partners Ltd | Schwind T.,Dr. Sauer and Partners Ltd | Grau B.,Dr. Sauer and Partners Ltd | Grau B.,University of Graz
ITA-AITES World Tunnel Congress 2016, WTC 2016 | Year: 2016

In Crossrail's Farringdon station, compensation grouting was successfully utilized to mitigate the surface settlements induced by the tunneling works. The main focus of this study was the platform tunnels, which were approximately 300m long each and were enlarged to platform size using sequential excavation method (SEM) from the existing TBM running tunnels, initially supported using sprayed concrete linings. The rear grouting injections were carried out at a typical distance of minimum 5m above the completed, fully strengthened shotcrete lining hence inducing some additional stresses. In-tunnel monitoring using surveying targets was performed systematically to ensure that no excessive distortion of the initial shotcrete lining occurred. 3D finite element analyses were utilized to back calculate the actual "effective" pressure that was imposed on the completed shotcrete rings against the additional measured in-tunnel displacements due to the compensation grouting episodes. Additionally an assessment of the theoretical, "maximum" allowable grouting pressures that would lead to overstressing of the lining is presented. Copyright © (2016) by the Society for Mining, Metallurgy and Exploration All rights reserved.

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