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The observational method applied to a high embankment founded on sulphide clay
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-5243-4650
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-9615-4861
2014 (English)In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 181, p. 112-123Article in journal (Refereed) Published
Abstract [en]

Since its introduction, Eurocode 7 has acknowledged the observational method as a valid design approach for geotechnical structures. The observational method is defined in five paragraphs. Although several case studies have concluded that the observational method is useful, the method is still sparsely used. This study compares the actual implementation of the observational method in the Veda embankment project according to the definitions given in Eurocode 7. The outcome of the observational method as a design approach, and the major deviations compared to the definitions in Eurocode 7 are discussed. It is concluded that the design of a multi-staged embankment, where the building process is governed by consolidation in the subsoil, can only partly be adapted to the observational method as defined in Eurocode 7. Furthermore, when this is the case, the possibility of combining "design by calculations" and the observational method is discussed.

Place, publisher, year, edition, pages
2014. Vol. 181, p. 112-123
Keywords [en]
Geotechnical engineering, Observational method, Eurocode 7, Embankments, Field testing and monitoring
National Category
Geology
Identifiers
URN: urn:nbn:se:kth:diva-157215DOI: 10.1016/j.enggeo.2014.07.003ISI: 000344426900010Scopus ID: 2-s2.0-84908702194OAI: oai:DiVA.org:kth-157215DiVA, id: diva2:769733
Note

QC 20141209

Available from: 2014-12-09 Created: 2014-12-08 Last updated: 2019-08-20Bibliographically approved
In thesis
1. Aspects on probabilistic approach to design: From uncertainties in pre-investigation to final design
Open this publication in new window or tab >>Aspects on probabilistic approach to design: From uncertainties in pre-investigation to final design
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Geotechnical engineering is strongly associated with large uncertainties. Exploring a medium (soil) that is almost entirely and completely hidden from us is no easy task. Investigations can be made only at discrete points, and the majority of a specific soil volume is never tested. All soils experience inherent spatial variability, which contributes to some uncertainty in the design process of a geotechnical structure. Furthermore, uncertainties also arise during testing and when design properties are inferred from these tests. To master the art of making decisions in the presence of uncertainties, probabilistic description of soil properties and reliability-based design play vital roles. Historically, the observational method (sometimes referred to as the “learn-as-you-go-approach”), sprung from ideas by Karl Terzaghi and later formulated by Ralph Peck, has been used in projects where the uncertainties are large and difficult to assess. The design approach is still highly suitable for numerous situations and is defined in Eurocode 7 for geotechnical design. In paper I, the Eurocode definition of the observational method is discussed. This paper concluded that further work in the probabilistic description of soil properties is highly needed, and, by extension, reliability-based design should be used in conjunction with the observational method. Although great progress has been made in the field of reliability-based design during the past decade, few geotechnical engineers are familiar with probabilistic approaches to design. In papers II and III, aspects of probabilistic descriptions of soil properties and reliability-based design are discussed. The connection between performing qualitative investigations and potential design savings is discussed in paper III. In the paper, uncertainties are assessed for two sets of investigations, one consisting of more qualitative investigations and hence with less uncertainty. A simplified Bayesian updating technique, referred to as “the multivariate approach”, is used to cross-validate data to reduce the evaluated total uncertainty. Furthermore, reliability-based design was used to compare the two sets of investigations with the calculated penetration depth for a sheet-pile wall. The study is a great example of how a small amount of both time and money (in the pre-investigation phase) can potentially lead to greater savings in the final design.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. p. xiv, 38
Series
TRITA-JOB. LIC, ISSN 1650-951X ; 2029
Keywords
Reliability-based design, Geotechnical design, Geotechnical structures, Sheet-pile wall, Characterization of uncertainties, Geotechnical investigations
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-178088 (URN)
Presentation
2016-02-26, V33, Teknikringen 72 (floor 5), KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Projects
TRUST, Transparent Underground Structures
Funder
Swedish Research Council Formas
Note

QC 20160201

Available from: 2016-02-01 Created: 2015-12-07 Last updated: 2016-02-01Bibliographically approved
2. Managing uncertainties in geotechnical parameters: From the perspective of Eurocode 7
Open this publication in new window or tab >>Managing uncertainties in geotechnical parameters: From the perspective of Eurocode 7
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Geotechnical engineering is strongly associated with large uncertainties. Geotechnical site investigations are made only at discrete points and most of a soil volume is never tested. A major issue is therefore how to cost effectively reduce geotechnical uncertainties with respect to structural performance. Managing the geotechnical uncertainties is thus an important aspect of the design process. Guidance on this subject is given in the European design code for geotechnical design, Eurocode 7 (EN 1997), which advocates the use of the partial-factor method, with the added possibility to use the observational method if the uncertainties are large and difficult to assess.This thesis aims to highlight, develop and improve methods to assess the quality and value of geotechnical site investigations through reliability-based design. The thesis also discusses the limitations of the deterministic partial-factor method, according to its EN 1997 definition, and how to better harmonise this design methodology with the risk-based approach of reliability-based design. The main research contributions are: (1) a presented case study showing the importance of and potential gains with a robust framework for statistical evaluation of geotechnical parameters, (2) the discussion on the limitations of the partial-factor method in EN 1997, and (3) the discussion on how to harmonise the EN 1997 definition of the partial-factor method with the risk-based approach of reliability-based design.

Abstract [sv]

Geoteknik förknippas med ett stort antal osäkerheter. Geotekniska undersökningar utförs i diskreta punkter och den absolut största delen av en jordvolym testas aldrig. En viktig fråga inom geotekniken är därför hur man kan minimera osäkerheterna i relation till kostnaderna för undersökningarna och konstruktionens säkerhet. En annan fråga som uppstår när en konstruktion ska dimensioneras är hur osäkerheterna bör hanteras i dimensioneringsprocessen. För detta ges vägledning i de europeiska dimensioneringsprinciperna för geotekniska konstruktioner, Eurokod 7 (EN 1997), som förespråkar partialkoefficientmetoden. Om osäkerheterna är stora och svåra att uppskatta kan observationsmetoden användas som ett komplement. Syftet med denna avhandling är att belysa, utveckla och förbättra metoder för bygg- och anläggningsbranschen att uppskatta kvalité och värde av geotekniska undersökningar. Ett bayesianskt tillvägagångssätt (multivariabel analys) har använts för att utvärdera osäkerheterna relaterade till de geotekniska undersökningarna. Därtill presenterar avhandlingen en diskussion om begränsningarna i partialkoefficientmetoden, enligt definitionen i EN 1997, och hur denna metod kan utvecklas för att bättre harmonisera med sannolikhetsbaserad dimensionering. De huvudsakliga forskningsbidragen är: (1) den presenterade fallstudien som visar vikten, och den potentiella nyttan, av ett robust ramverk för statistisk utvärdering av geotekniska parametrar som grund för sannolikhetsbaserad dimensionering, (2) diskussionen om begränsningarna med partialkoefficientmetoden enligt definitionen i EN1997, och (3) diskussionen om hur partialkoefficientmetoden kan utvecklas för att bättre harmonisera med sannolikhetsbaserad dimensionering.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 79
Series
TRITA-ABE-DLT ; 1924
Keywords
Eurocode 7, Characteristic value, Partial-factor method, Reliability-based design
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-256058 (URN)978-91-7873-249-4 (ISBN)
Public defence
2019-09-19, Kollegiesalen, Brinellvägen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council FormasSwedish Transport Administration
Note

QC 20190822

Available from: 2019-08-22 Created: 2019-08-20 Last updated: 2019-08-22Bibliographically approved

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Prästings, AndersLarsson, Stefan

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