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On reliability-based design of rock tunnel support
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Tunneling involves large uncertainties. Since 2009, design of rock tunnels in European countries should be performed in accordance with the Eurocodes. The main principle in the Eurocodes is that it must be shown in all design situations that no relevant limit state is exceeded. This can be achieved with a number of different methods, where the most common one is design by calculation. To account for uncertainties in design, the Eurocode states that design by calculation should primarily be performed using limit state design methods, i.e. the partial factor method or reliability-based methods. The basic principle of the former is that it shall be assured that a structure’s resisting capacity is larger than the load acting on the structure, with high enough probability. Even if this might seem straightforward, the practical application of limit state design to rock tunnel support has only been studied to a limited extent.

The aim of this licentiate thesis is to provide a review of the practical applicability of using reliability-based methods and the partial factor method in design of rock tunnel support. The review and the following discussion are based on findings from the cases studied in the appended papers. The discussion focuses on the challenges of applying fixed partial factors, as suggested by Eurocode, in design of rock tunnel support and some of the practical difficulties the engineer is faced with when applying reliability-based methods to design rock tunnel support.

The main conclusions are that the partial factor method (as defined in Eurocode) is not suitable to use in design of rock tunnel support, but that reliability-based methods have the potential to account for uncertainties present in design, especially when used within the framework of the observational method. However, gathering of data for statistical quantification of input variables along with clarification of the necessary reliability levels and definition of “failure” are needed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 52
Series
TRITA-JOB. LIC, ISSN 1650-951X ; 2033
Keywords [en]
Rock engineering, reliability-based design, Eurocode 7, observational method, tunnel engineering
Keywords [sv]
Bergmekanik, sannolikhetsbaserad dimensionering, Eurokod 7, observationsmetoden, tunnelbyggnation.
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-204919ISBN: 978-91-7729-354-5 (print)OAI: oai:DiVA.org:kth-204919DiVA, id: diva2:1086872
Presentation
2017-05-18, B3, Brinellvägen 23, KTH-Campus, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20170407

Available from: 2017-04-07 Created: 2017-04-04 Last updated: 2017-04-07Bibliographically approved
List of papers
1. Challenges in applying fixed partial factors to rock engineering design
Open this publication in new window or tab >>Challenges in applying fixed partial factors to rock engineering design
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2017 (English)In: Geotechnical Special Publication, ISSN 0895-0563, no 283, p. 384-393Article in journal (Refereed) Published
Abstract [en]

The Swedish national guidelines for design of the main structural support system in road and railway rock tunnels have been adjusted to cohere with Eurocode 7. In the design guidelines, the limit states that the designer should consider are specified. The main method to account for uncertainties in the Swedish guidelines is similar to the method preferred in Eurocode 7: the partial factor method. For each limit state, fixed partial factors retrieved from different sections of the Eurocodes are specified. However, fixed partial factors may not correspond to the same structural reliability for all design situations. In this paper, we show for a common design situation in rock engineering design how partial factors in theory should vary with design geometries and uncertainties. The derived partial factors are compared to the Eurocodes’ fixed values. We find that using fixed partial factors to ensure structural safety in these limit states might not be suitable. The implications are discussed along with suggestions of other more suitable methods to account for uncertainties in rock engineering design.

Place, publisher, year, edition, pages
Reston: American Society of Civil Engineers (ASCE), 2017
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-204912 (URN)10.1061/9780784480700.037 (DOI)000406412100037 ()2-s2.0-85030456959 (Scopus ID)
Note

QC 20170419

Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-11-30Bibliographically approved
2. Some aspect of reliability-based design for tunnels using observational method (EC7)
Open this publication in new window or tab >>Some aspect of reliability-based design for tunnels using observational method (EC7)
2015 (English)In: EUROCK 2015 & 64th Geomechanics Colloquium, Salzburg, 2015Conference paper, Published paper (Refereed)
Abstract [en]

According to Eurocode 7, the observational method is an accepted design method, where a preliminary design may be updated as the construction progresses. However, Eurocode 7 does not give any advice on how to relate the observations to the acceptable level of safety of the structure. In this paper, we outline a methodology for how to use deformation measurements to predict the final deformation of a circular rock tunnel to calculate the probability of failure. Consequently, the measurements can be used to verify that the design does not violate the specified safety level. The paper shows the potential of combining the observational method with reliability-based design in tunneling

Place, publisher, year, edition, pages
Salzburg: , 2015
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-184132 (URN)
Conference
ISRM Regional Symposium Eurock 2015
Note

QC 20160408

Available from: 2016-03-28 Created: 2016-03-28 Last updated: 2017-04-04Bibliographically approved
3. Reliability aspects of rock tunnel design with the observational method
Open this publication in new window or tab >>Reliability aspects of rock tunnel design with the observational method
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(English)Manuscript (preprint) (Other academic)
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-204911 (URN)
Note

QC 20170419

Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-04-19Bibliographically approved

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