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  • 101.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Reducing uplift pressure uncertainty with measurements under concrete dams2013In: Proceedings ICOLD 2013 International Symposium, Denver: US Society on Dams , 2013, p. 2551-2560Conference paper (Refereed)
    Abstract [en]

    In quantitative risk analyses of concrete dams founded on rock, it is necessary to consider the uplift pressure in the foundation with respect to both mean value and variation. With a more accurately predicted uplift pressure, the calculated probability of failure of the dam can be reduced. This paper proposes a methodology for predicting the current uplift pressure and related uncertainty, based both on pore pressure measurements and on expert judgment. An illustrative example is presented and the suggested methodology is compared with other conceivable approaches. The results are found to be reasonable in most conditions. However, it should be recognized that in risk analyses of dams, more extreme load cases not captured by the measurements also must be considered.

  • 102.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Tillståndsbedömning av betongdammar grundlagda på berg med observationsmetoden2013In: Bygg & teknik, ISSN 0281-658X, no 1, p. 83-87Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Observationsmetoden erbjuder ett alternativ till dagens mer etablerade dimensioneringsmetoder för geokonstruktioner. På Avdelningen för jord- och bergmekanik på Kungliga Tekniska högskolan (KTH) pågår för tillfället ett forskningsprojekt om när och i vilka typer av projekt som denna metod kan vara lämplig att använda, då man bygger i och på berg. Nu påbörjar vi ett delprojekt som syftar till att undersöka om och hur observationsmetoden kan tillämpas vid tillståndsbedömning av betongdammar grundlagda på berg, som ett led i att utveckla förvaltningen av Sveriges bestånd av dammar. Projektet finansieras av Svenskt Vattenkraftcentrum (SVC), Stiftelsen Bergteknisk forskning (BeFo) och Formas.

  • 103.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Towards an improved observational method2014In: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium, Taylor & Francis Group, 2014, p. 1435-1440Conference 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.

  • 104.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On the observational method for groundwater control in the Northern Link tunnel project, Stockholm, Sweden2014In: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 73, no 2, p. 401-408Article in journal (Refereed)
    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.

  • 105.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lizka, Hana
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Observationsmetodens tillämpning på inläckande grundvatten i bergtunnlar – Fallstudie: Norra länken i Stockholm2012In: Bergmekanikdag 2012 - Föredrag / [ed] Eva Friedman, 2012, p. 89-100Conference paper (Other academic)
  • 106.
    Sölve, Hov
    et al.
    GeoMind.
    Persson, Erik
    Bjerking.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Korrelationer mellan odräneradskjuvhållfasthet och förkonsolideringstryck i lera2018In: Bygg & teknik, ISSN 0281-658X, no 1, p. 55-58Article in journal (Other academic)
  • 107.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Influence of force ratio and frequency on vibratory surface compaction2016In: Geotechnics for Sustainable Infrastructure Development / [ed] Phung Duc Long, 2016Conference paper (Refereed)
  • 108.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Small-Scale Testing of Frequency-Dependent Compaction of Sand Using a Vertically Vibrating Plate2013In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 36, no 3, p. 394-403Article in journal (Refereed)
    Abstract [en]

    Vibratory rollers generally operate at a fixed vibration frequency. It is hypothesized that the compaction of soil could be made more efficient if the frequency could be adapted to specific project conditions. In order to study the applicability to surface compaction, the frequency dependence of compacting dry sand with a vertically vibrating plate was investigated experimentally in 85 small-scale tests. Tests were performed in a test box simulating the free-field condition and with concrete underlying the sand bed. The results show that there is a distinct frequency dependence, implying a significantly improved compaction effect close to the compactor soil resonant frequency. It is suggested that particle velocity is the governing amplitude parameter for vibratory soil compaction, rather than displacement or acceleration. As the soil is compacted, it is also displaced, resulting in surface heave. A larger vibration amplitude implies greater displacement relative to the compacted volume. It was also observed that the compaction and strain-dependent reduction of soil stiffness are closely related.

  • 109.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bodare, Anders
    Dynamic response of vertically oscillating foundations at large strain2014In: Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 / [ed] Oka, Murakami, Uzuoka & Kimoto, CRC Press, 2014, p. 643-647Conference paper (Refereed)
    Abstract [en]

    A method for calculating the dynamic response of a vertically oscillating foundation on soil with strain-dependent properties is developed. Strain-dependent stiffness and damping are incorporated by an iterative procedure, presenting the response in frequency domain. The calculated dynamic displacement amplitudes are compared to small-scale tests using a vertically oscillating plate. The calculated dynamic quantities agree well with measured amplitudes over a wide frequency range.

  • 110.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rydén, Nils
    Lund Universitet.
    Nordfelt, Ingmar
    Dynapac.
    Frequency Variable Surface Compaction of Sand Using Rotating Mass Oscillators2015In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 38, no 2, p. 198-207Article in journal (Refereed)
    Abstract [en]

    The influence of vibration frequency was studied in 110 small-scale compaction tests conducted using a vertically oscillating plate. The underlying soil was dry sand, or sand close to the optimum water content. The results showed that there is a resonant amplification, providing a slightly higher degree of compaction. Frequency has a major influence on soil compaction. An iterative method for calculating the dynamic response of the plate, incorporating strain-dependent properties of the soil, is also presented. The calculated frequency response agrees fairly well with measured quantities.

  • 111.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, I.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Resonant roller compaction of gravel in full-scale tests2018In: Transportation Geotechnics, ISSN 2214-3912, Vol. 14, p. 93-97Article in journal (Refereed)
    Abstract [en]

    Results from a recent study indicated that compaction by vibratory roller can be made more time- and energy-efficient by operating at a vibration frequency close to resonance. In this paper, the results are verified and the reduction in operating time is quantified by conducting detailed full-scale tests under realistic conditions at two frequencies: the standard operating frequency of the roller and a lower frequency slightly above resonance. Compaction was done in two tests per frequency with 16 passes in each test. The obtained compaction was quantified using a combination of measurement techniques, including laser levelling, nuclear density gauge and static plate load tests. The results confirm that the lower frequency is more efficient for compaction and that utilizing resonance in the roller-soil system can reduce the number of passes. In addition, lowering the frequency reduces energy consumption, environmental impact and machine wear. 

  • 112.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, Ingemar
    Dynapac.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Vibrovältar och jorddynamik - mot effektivare packning2013In: Bygg & teknik, ISSN 0281-658X, no 1, p. 32-35Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Packning är den vanligaste jordförstärkningsmetoden och används i stort sett i alla byggprojekt. Ökande byggkostnader och striktare utsläppskrav gör att det finns ett behov av att effektivisera packningsprocessen. I ett doktorandprojekt vid Kungliga Tekniska högskolan (KTH) studeras hur jordpackning med vibrovält kan bli mer effektivt genom att ta hänsyn till  amspelet mellan vält och jord samt vältens och jordens dynamiska egenskaper. Projektet  inansieras av Svenska Byggbranschens Utvecklingsfond (SBUF), Dynapac, Peab och KTH och utförs som ett samarbete mellan KTH, Dynapac och Peab.

  • 113.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, Ingmar
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Effektivare packning med nya insikter2018In: Bygg & Teknik, ISSN 0281-658X, no 1, p. 44-45Article in journal (Other academic)
  • 114.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, Ingmar
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Roller compaction of rock-fill with automatic frequency control2018In: Proceedings of the Anniversary Symposium – 40 Years of Roller Integrated Continuous Compaction Control (CCC), 2018Conference paper (Refereed)
  • 115.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, Ingmar
    Dynapac Compaction Equipment AB.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Soil compaction by vibratory roller with variable frequency2016In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656Article in journal (Refereed)
    Abstract [en]

    Full-scale tests were conducted to study the influence of the operating frequency of a vibratory roller on the compaction of crushed gravel in a controlled environment. Tests were performed at both fixed and variable frequencies. The average densification of the soil was represented by settlement of the ground surface, and depth-dependent density variation before and after compaction was determined by horizontal nuclear density gauge measurements. The resonant frequency was approximately 17 Hz and frequencies in the range 15–35 Hz were tested. The optimum compaction frequency was determined to be around 18 Hz; that is, slightly above resonance, as compared with the standard operating frequency of the roller, 31 Hz. Lower compaction frequency significantly reduces the required engine power and thus fuel consumption and environmental impact, while increasing the lifespan of the roller. Furthermore, the soil closest to the ground surface is loosened at high frequency. This can be avoided with a lower compaction frequency and the need for subsequent static passes can thereby possibly be eliminated.

  • 116.
    Westerberg, Bo
    et al.
    Swedish Geotechnical Institute, Linköping, Sweden.
    Müller, Rasmus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Tyréns AB, Sweden.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Evaluation of undrained shear strength of Swedish fine-grainedsulphide soils2015In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 188, p. 77-87Article in journal (Refereed)
    Abstract [en]

    In Swedish practice, there is a long tradition of evaluating undrained shear strength from fall-cone tests and field vane tests. During the last 20 years cone penetration tests have also become widely used. However, the results from all these test methods have to be evaluated using empirical factors. The factors generally used for Swedish clays are related to liquid limit and overconsolidation, but they are not applicable to all types of fine-grained soils and can often be improved by local calibration for the particular type of soil in the area of current interest. For this calibration, the results of direct simple shear tests and/or triaxial tests in the laboratory are normally used. This paper presents an evaluation for Swedish fine-grained sulphide soils, for which a general correction factor of 0.65 for field vane tests and fall-cone tests, a cone factor Nkt of 20.2 for cone penetration tests and a relation cu,DSS/(σ′cOCR−0.2) of 0.28 have been found. No correlations were found between these empirical factors and the clay content, liquid limit or organic content, but a relationship was found between the overconsolidation ratio and both the cone penetration test and the field vane test. The sulphide soils in question are found in northern Sweden along the coast of the Gulf of Bothnia. They aremostly classified as organic silt or organic clay,which is normally silty.

  • 117.
    With, Christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bodare, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lime-cement columns as wave barrier against train-induced vibrations2007In: Geotechnical Engineering in Urban Environments: Proceedings of the 14th European Conference on Soil Mechanicsand Geotechnical Engineering / [ed] V. Cuéllar, E. Dapena, E. Alonso, J.M. Echave, A. Gens, J.L. de Justo, C. Oteo, J.M. Rodríguez-Ortiz, C. Sagaseta, P. Sola, A. Soriano, 2007, p. 1397-1401Conference paper (Refereed)
  • 118.
    Wonglert, Anucha
    et al.
    King Mongkuts Univ Technol Thonburi, Dept Civil Engn, Bangkok, Thailand..
    Jongpradist, Pornkasem
    King Mongkuts Univ Technol Thonburi, Dept Civil Engn, Bangkok, Thailand..
    Jamsawang, Pitthaya
    King Mongkuts Univ Technol North Bangkok, Dept Civil Engn, Bangkok, Thailand..
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bearing capacity and failure behaviors of floating stiffened deep cement mixing columns under axial load2018In: Soil and foundation, ISSN 0038-0806, Vol. 58, no 2, p. 446-461Article in journal (Refereed)
    Abstract [en]

    This research aims to clarify and gain an insight into the impact of the length of the stiffened core and the strength of the deep cement mixing (DCM) socket on the behaviors of floating stiffened deep cement mixing (SDCM) columns. The observed behaviors include the axial ultimate bearing capacity, settlement and failure mode. The study begins by conducting a series of physical model tests as a preliminary investigation. The results reveal that the strength of the DCM socket can be reduced to a certain value by inserting a sufficiently long reinforced core to achieve the highest possible load-carrying capacity, indicating an optimum length of the stiffened core for a specific DCM socket strength. For a parametric study on the actual scale condition, full-scale load tests on a floating DCM and an SDCM column with eucalyptus wood as a core in the thick soft clay layer area were carried out to provide a reference case. The extended numerical analysis results suggest that the modes of failure depend on the length of the stiffened core and the strength of the DCM socket. The results from the numerical parametric study were used to establish a guideline chart for suggesting the appropriate length of the core in accordance with the strength of the DCM socket of the floating SDCM columns. The field pile load test results also confirm that core materials with a lower strength and stiffness, such as eucalyptus wood, could potentially be used as a reinforced core.

123 101 - 118 of 118
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