Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Toward a reliability framework for the observational method
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-5372-7519
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Constructing sustainable structures in rock that satisfy all predefined technical specifications requires rational and effective construction methods. When the geotechnical behaviour is hard to predict, the Euro­pean design code, Eurocode 7, suggests application of the observational method to verify that the performance is acceptable. The basic principle of the method is to accept predefined changes in the design during con­struction to comply with the actual ground conditions, if the current de­sign is found unsuitable. Even though this in theory should ensure an effective design solution, formal application of the observational method is rare.

Investigating the applicability of the observational method in rock en­gineering, the aim of this thesis is to identify, highlight, and solve the aspects of the method that limit its wider application. Furthermore, the thesis aims to improve the conceptual understanding of how design deci­sions should be made when large uncertainties are present.

The main research contribution is a probabilistic framework for the observational method. The suggested methodology allows comparison of the merits of the observational method with that of conventional design. Among other things, the thesis also discusses (1) the apparent contradiction between the preference for advanced probabilistic calculation methods and sound, qualitative engineering judgement, (2) how the establishment of limit states and alarm limits must be carefully considered to ensure structural safety, and (3) the applicability of the Eurocode defini­tion of the observational method and the implications of deviations from its principles.

Abstract [sv]

För att kunna konstruera en anläggning i berg, som uppfyller satta tek­niska krav, krävs det en rationell och effektiv konstruktionsmetod. När konstruktionens beteende är svårt att förutsäga, erbjuder den europeiska standarden Eurokod 7 den så kallade observationsmetoden. Denna metod tillåter i förväg förberedda förändringar i designen under konstruktions­tiden, om observationer av konstruktionens beteende indikerar att så behövs. På så vis anpassas konstruktionen till de faktiska förhållandena i marken. Trots att detta tillvägagångssätt i teorin ger en rationell design, används metoden sällan i enlighet med Eurokod 7.

Denna doktorsavhandling undersöker tillämpbarheten av observa-tionsmetoden när man bygger i och på berg. Målet är att belysa de aspekter som begränsar dess användning och i dessa fall föreslå förbätt­ringar som ökar tillämpbarheten. I ett vidare perspektiv syftar avhand­lingen även till att förbättra den konceptuella förståelsen för hur beslut bör fattas i designprocessen när det finns stora osäkerheter.

Avhandlingen visar hur observationsmetoden kan användas i ett san­nolikhetsbaserat ramverk. Metodiken ger användaren möjlighet att jäm­föra för- och nackdelarna med observationsmetoden och konventionell dimensionering. Avhandlingen diskuterar bland annat även (1) den skenbara motsatsen mellan användandet av sannolikhetsbaserade beräkningsmetoder för att lösa komplexa dimensioneringsfrågor och kvalitativa ingenjörsmässiga bedömningar, (2) hur larmgränser och brottgränstillstånd bör definieras för att ge tillräcklig säkerhetsmarginal, samt (3) hur Eurokod 7:s strikta definition av observationsmetoden påverkar dess användbarhet.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan, 2016.
Series
TRITA-JOB PHD, ISSN 1650-9501 ; 1023
Keyword [en]
Rock engineering, observational method, Eurocode 7, structural safety, reliability analysis, dam safety
Keyword [sv]
Bergmekanik, observationsmetoden, Eurokod 7, sannolikhetsbaserad dimensionering, dammsäkerhet
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-192825ISBN: 978-91-7729-128-2 (print)OAI: oai:DiVA.org:kth-192825DiVA: diva2:974101
Public defence
2016-10-25, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160926

Available from: 2016-09-26 Created: 2016-09-20 Last updated: 2016-09-26Bibliographically approved
List of papers
1. On the observational method for groundwater control in the Northern Link tunnel project, Stockholm, Sweden
Open this publication in new window or tab >>On the observational method for groundwater control in the Northern Link tunnel project, Stockholm, Sweden
2014 (English)In: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 73, no 2, 401-408 p.Article in journal (Refereed) Published
Abstract [en]

For tunnelling in rock in Sweden, the public authorities usually set stringent requirements on low groundwater inflow to the tunnel, to minimise the risk of building settlement and the environmental impact. To improve this groundwater control, the potential application of the observational method in this matter was studied. A comparison was made between the actual implementation of groundwater control in the Northern Link road tunnel project in Stockholm and the definition of the observational method in Eurocode 7. The results showed that the groundwater control in the Northern Link project mainly agreed with the Eurocode. The significance of the deviations was discussed, and it was concluded that adopting the observational method for groundwater control so that it complied with Eurocode 7 would mostly entail simply a formalisation of today's procedures.

Keyword
Eurocode 7, Groundwater, Observational method, Tunnelling
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-136378 (URN)10.1007/s10064-013-0501-8 (DOI)000335156900011 ()2-s2.0-84899647565 (Scopus ID)
Funder
Formas
Note

QC 20140604

Available from: 2013-12-04 Created: 2013-12-04 Last updated: 2017-12-06Bibliographically approved
2. On the use of pore pressure measurements in safety reassessments of concrete dams founded on rock
Open this publication in new window or tab >>On the use of pore pressure measurements in safety reassessments of concrete dams founded on rock
2013 (English)In: Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, ISSN 1749-9518, E-ISSN 1749-9526, Vol. 8, no 2, 117-128 p.Article in journal (Refereed) Published
Abstract [en]

In probabilistic stability analyses of concrete dams founded on rock, the uplift pressure is often a parameter of major importance. In previous literature, it has been suggested that assessing uplift with pore pressure measurements, instead of using empirical assumptions, could improve the calculated dam safety. This paper presents a coherent methodology to investigate whether incorporating pore pressure measurements has any impact on the calculated dam safety, based on Bayesian linear regression of pore pressure data in combination with series-system and the first-order reliability method. The study concludes that the probability of sliding failure is closely related to the probability of an extreme increase in uplift. Hence, measured uplift should only be incorporated while this probability remains sufficiently small, which requires proper programs both for uplift monitoring and for maintenance of drains and grout curtains.

Place, publisher, year, edition, pages
Taylor & Francis, 2013
Keyword
dam safety, dams, probability of failure, reliability analysis, system reliability
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-136377 (URN)10.1080/17499518.2013.864172 (DOI)2-s2.0-84897054569 (Scopus ID)
Note

QC 20140415

Available from: 2013-12-04 Created: 2013-12-04 Last updated: 2017-12-06Bibliographically approved
3. Using observational method to manage safety aspects of remedial grouting of concrete dam foundations
Open this publication in new window or tab >>Using observational method to manage safety aspects of remedial grouting of concrete dam foundations
2016 (English)In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529, Vol. 34, no 5, 1613-1630 p.Article in journal (Refereed) Published
Abstract [en]

As concrete dams age, the need for remedial grouting to reduce the seepage and uplift pressure in the rock foundations under them increases. Based on a case study of a Swedish dam with very low calculated safety against sliding, this paper discusses the application of the observational method (as defined in Eurocode 7) to manage safety aspects during remedial grouting. The studied case was complex in that grouting works posed the risk of causing increased uplift pressure, which could have induced sliding failure along a shallow, persistent, horizontal rock joint in the foundation. The approach applied in the studied case mainly followed the principles of the observational method, except in some highly significant safety aspects for which alternative procedures are suggested and discussed. Implementing these procedures along with the observational method offers a coherent framework to manage the safety aspects of the remedial grouting of concrete dam foundations that is in line with modern risk-informed dam safety policies.

Place, publisher, year, edition, pages
Springer, 2016
Keyword
observational method; Eurocode 7; dam safety; foundation; grouting;
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-192817 (URN)10.1007/s10706-016-0069-8 (DOI)000384332200024 ()2-s2.0-84982279542 (Scopus ID)
Note

QC 20160929

Available from: 2016-09-20 Created: 2016-09-20 Last updated: 2017-11-21Bibliographically approved
4. Towards an improved observational method
Open this publication in new window or tab >>Towards an improved observational method
2014 (English)In: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium, Taylor & Francis Group, 2014, 1435-1440 p.Conference paper, Published paper (Refereed)
Abstract [en]

The observational method is today an accepted method in Eurocode 7 for design of geotechnical structures. However, case studies with formal application of its principles are still rare. One reason could be that the method to some extent is considered complex and associated with low safety margins. In fact, the Eurocode does not give any reference to how the safety of the completed structure can be assured. This paper strives to open up a discussion on how the observational method can be improved by including a requirement for a safety margin of the completed structure. A methodology is outlined and illustrated with a simple calculation example analysing the safety of a square rock pillar. Lastly, the compatibility with the observational method is discussed.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2014
Keyword
Rock mechanics, observational method, Eurocode, reliability-based design
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-144206 (URN)10.1201/b16955-250 (DOI)000345985300233 ()2-s2.0-84901325558 (Scopus ID)978-1-138-00149-7 (ISBN)
Conference
2014 ISRM European Regional Symposium on Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, EUROCK 2014, Vigo, Spain, 26 May 2014 through 28 May 2014
Note

QC 20150108. Updated from manuscript to proceedings paper

Available from: 2014-04-14 Created: 2014-04-14 Last updated: 2016-09-23Bibliographically approved
5. 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
6. When is the observational method in geotechnical engineering favourable?
Open this publication in new window or tab >>When is the observational method in geotechnical engineering favourable?
2017 (English)In: Structural Safety, ISSN 0167-4730, E-ISSN 1879-3355, Vol. 66, 17-26 p.Article in journal (Refereed) Published
Abstract [en]

The observational method in geotechnical engineering is an acceptable verification method for limit states in Eurocode 7, but the method is rarely used despite its potential savings. Some reasons may be its unclear safety definition and the lack of guidelines on how to establish whether the observational method is more favourable than conventional design. In this paper, we challenge these issues by introducing a reliability con­straint on the observational method and propose a probabilistic optimi­sation methodology that aids the decision-making engineer in choosing between the observational method and conventional design. The method­ology suggests an optimal design after comparing the expected utilities of the considered design options. The methodology is illustrated with a practical example, in which a geotechnical engineer evaluates whether the observational method may be favourable in the design of a rock pillar. We conclude that the methodology may prove to be a valuable tool for deci­sion-making engineers’ everyday work with managing risks in geotech­nical projects.

Keyword
Observational method, reliability-based design, decision analysis, Eurocode 7
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-192821 (URN)10.1016/j.strusafe.2017.01.006 (DOI)2-s2.0-85011115079 (Scopus ID)
Note

QC 20160923

Available from: 2016-09-20 Created: 2016-09-20 Last updated: 2017-05-23Bibliographically approved

Open Access in DiVA

fulltext(1234 kB)236 downloads
File information
File name FULLTEXT01.pdfFile size 1234 kBChecksum SHA-512
f13684049d1084b52cb7a1adbf558531f895d8a5ff80a63cff3d795efb8fd2e0c5a8272482da7c12c419f907e561ffa88092c7e80d3653e926c9256e617fd46b
Type fulltextMimetype application/pdf

Authority records BETA

Spross, Johan

Search in DiVA

By author/editor
Spross, Johan
By organisation
Soil and Rock Mechanics
Geotechnical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 236 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1972 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf