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  • 1.
    Abbasiverki, Roghayeh
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Ansell, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Seismic response of buried concrete pipelines subjected to highfrequency earthquakesInngår i: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Buried pipelines are tubular structures that cross large areas with different geological conditions. During an earthquake, imposed loads from soil deformations on concrete pipelines may cause severe damages. In this study, the use of two-dimensional finite element models of pipelines and surrounding soil for simulation of seismic waves that propagate from the bedrock through the soil are demonstrated. The models describe both longitudinal and transverse cross-sections of pipelines and the soil-pipe interaction is modelled as a nonlinear behaviour. The effects of uniform ground with different burial depths, soil layer thickness, soil stiffness and bedrock geometry on the seismic response of reinforced concrete pipelines is studied. Two earthquakes, with high and low frequency contents, are employed for the dynamic analysis. The results show that there is a much smaller risk of damage from high-frequency earthquakes, but that there is a significant effect on the response due to possible irregular ground with inclined bedrock.

  • 2.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik. College of Civil Engineering, Roudehen branch, Islamic Azad University, Tehran, Iran.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    CPT-SPT correlations using artificial neural network approach: A Case Study in Sweden2015Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 20, nr 28, s. 13439-13460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The correlation between Standard and Cone Penetration Tests (SPT and CPT) as two of the most used in-situ geotechnical tests is of practical interest in engineering designs. In this paper, new SPT-CPT correlations for southwest of Sweden are proposed and developed using an artificial neural networks (ANNs) approach. The influences of soil type, depth, cone tip resistance, sleeve friction, friction ratio and porewater pressure on obtained correlations has been taken into account in optimized ANN models to represent more comprehensive and accurate correlation functions. Moreover, the effect of particle mean grain size and fine content were investigated and discussed using graph analyses. The validation of ANN based correlations were tested using several statistical criteria and then compared to existing correlations in literature to quantify the uncertainty of the correlations. Using the sensitivity analyses, the most and least effective factors on CPT-SPT predictions were recognized and discussed. The results indicate the ability of ANN as an attractive alternative method regarding to conventional statistical analyses to develop CPT-SPT relations.

  • 3.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Updated relations for the uniaxial compressive strength of marlstones based on P-wave velocity and point load index test2016Inngår i: INNOVATIVE INFRASTRUCTURE SOLUTIONS, ISSN 2364-4176, Vol. 1, nr 1, artikkel-id UNSP 17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although there are many proposed relations for different rock types to predict the uniaxial compressive strength (UCS) as a function of P-wave velocity (V-P) and point load index (Is), only a few of them are focused on marlstones. However, these studies have limitations in applicability since they are mainly based on local studies. In this paper, an attempt is therefore made to present updated relations for two previous proposed correlations for marlstones in Iran. The modification process is executed through multivariate regression analysis techniques using a provided comprehensive database for marlstones in Iran, including UCS, V-P and Is from publications and validated relevant sources comprising 119 datasets. The accuracy, appropriateness and applicability of the obtained modifications were tested by means of different statistical criteria and graph analyses. The conducted comparison between updated and previous proposed relations highlighted better applicability in the prediction of UCS using the updated correlations introduced in this study. However, the derived updated predictive models are dependent on rock types and test conditions, as they are in this study.

  • 4.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Kartering av skredbenägenhet medartificiell intelligens2018Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1Artikkel i tidsskrift (Annet vitenskapelig)
  • 5.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Storskalig kartering av skredbenägenhet i västra Götaland med artificiell intelligens2018Konferansepaper (Annet vitenskapelig)
  • 6.
    Al-Naqshabandy, Mohammed
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Effect of Uncertainties of Improved Soil Shear Strength on the Reliability of Embankments2013Inngår i: Journal of Geotechnical and Geoenvironmental Engineering, ISSN 1090-0241, E-ISSN 1943-5606, Vol. 139, nr 4, s. 619-632Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The strength variability of soils improved by lime-cement columns is very high, and assessment of the reliability is associated with high uncertainty. Previous research on natural soils has shown that variability has a major impact on the reliability of geotechnical systems. However, concerning ground improvement with lime-cement columns, the effect of the uncertainties associated with improved strength properties on the reliability is unknown. This paper addresses the integration of reliability-based design in the design of embankments founded on soil improved by lime-cement columns by an analysis of a project conducted in Sweden. The uncertainties associated with estimating the strength property based on results from cone penetration tests and their effect on the assessed system reliability are addressed and discussed. The use of variance reduction with respect to the spatial variability of the shear strength of the columns was found to have a major influence on the assessed system reliability. Furthermore, it was found that the transformation uncertainty from measurements based on cone penetration tests has a significant impact on the assessed system reliability. System reliability cannot be improved significantly simply by performing a large number of tests.

  • 7.
    Al-Naqshabandy, Mohammed
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Partial factor design for a highway embankment founded on lime-cement columns2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stability assessment of highway embankments is a common practice in geotechnical engineering. Rational estimation of soil properties is essential for reliable and safe design. However, previous research has shown that high degree of uncertainty is associated with engineering properties and the behavior of the ground improvement with lime-cement columns. Current design methods for stability of lime-cement column are deterministic and the uncertainties are not treated rationally. A reliable design requires rational treatment of uncertainties. This paper addresses the need for application of partial factor design for safety and reliability assessment of lime-cement columns. The study was carried out on an example highway embankment of 6 m height. Resistance and load parameters were considered random variables. The sensitivity factors for the random variables were evaluated from the first order reliability method (FORM). Partial factors were evaluated for the random variables according to the approximate location of the design values. It was shown that the design by partial factor method fulfills both safety and reliability requirements.

  • 8.
    Al-Naqshabandy, Mohammed Salim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Bergman, Niclas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Effect of spatial variability of the strength properties in lime-cement columns on embankment stability2012Inngår i: Geotechnical Special Publication, ISSN 0895-0563, Vol. 228, s. 231-242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatial variability with respect to the strength in lime-cement columns is an unavoidable source of uncertainty that should be considered in design. Current design method for the assessment of embankment stability, based on the deterministic factor of safety, cannot address the effect of spatial variability. Reliability-based design methodology is a powerful tool that can be used to integrate the variability into the analysis. In this paper, the spatial variability with respect to the undrained shear strength in the soil and in the columns was evaluated based on CPT test. The first order second moment (FOSM) reliability method was applied to address the impact of the spatial variability of the strength in the soil and in the columns on the reliability of an embankment founded on improved soil by lime-cement columns. The paper also presents a technique to evaluate the variance reduction factor over the failure surface. The results propose that the undrained shear strength in the soil and in the columns can be modelled following normal or lognormal distribution. The analysed example show that the reliability increased significantly when the spatial variability was considered

  • 9.
    Al-Naqshabandy, Mohammed Salim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Bergman, Niclas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Strength variability in lime-cement columns based on CPT data2012Inngår i: Ground Improvement, ISSN 1365-781X, E-ISSN 1751-7621, Vol. 165, nr 1, s. 15--30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Natural and improved soils have relatively high inherent property variability that should be taken into consideration in design. Investigations of the spatial variability in lime-cement columns are important since they provide a rational quantification of the variability parameters needed for a reliability-based design analysis of geotechnical systems. Statistical analyses are used to evaluate the spatial variability parameters, i.e. the mean, the variance, and the scale of fluctuation, which is the distance within which soil properties reveal strong correlation. This paper presents a field test, in which 30 CPT soundings were performed and analyzed statistically in order to address the spatial variability in a group of lime-cement columns, with respect to the cone tip resistance. The objective of this paper is to describe the statistical analyses and to make a contribution to the empirical knowledge about strength variability in a volume of lime-cement columns. Stationarity has been assessed, and the scale of fluctuation has been evaluated in the vertical and horizontal directions. Random field theory was used based on the sample autocorrelation function ACF. The scale of fluctuation was found to be within the range of 0.2-0.7 m and 2-3 m in the vertical and horizontal direction, respectively. A simple design consideration shows that the variance reduction factor has a major influence on the determination of the design value.

  • 10. Axelsson, Morgan
    et al.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Column penetration tests for lime-cement columns in deep mixing - experiences in Sweden2003Inngår i: Geotechnical Special Publication, ISSN 0895-0563, Vol. 120, s. 681-694Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper column penetration tests for lime-cement columns in deep soil mixing are reviewed. In principle, column penetration tests and reversed column penetration tests are considered. Improved test techniques are presented and discussed based on tests from two test sites in Sweden. The investigations indicate that the reversed column penetration test is the most suitable method for the primary quality test with reference to the uniformity and continuity of the columns. The probe should, however, be installed by the lime-cement column machine short after the manufacturing of the column to avoid disturbances in the mixing process and to enable a random test selection.

  • 11.
    Bergman, Niclas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Al-Naqshabandy, Mohammed Salim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Variability of strength and deformation properties in lime-cement columns evaluated from CPT and KPS measurements2013Inngår i: Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, ISSN 1749-9518, E-ISSN 1749-9526, Vol. 7, nr 1, s. 21-36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The strength variability of soil improved by deep mixing with lime-cement columns is generally high. Eurocode 7 states that selection of characteristic values for geotechnical parameters shall take the variability of measured property values into account. This variability can be considered in the design by using reliability-based design. With reliability-based design, three statistical parameters are needed to evaluate the design value; mean, variance and scale of fluctuation. In this paper, the shear strength of soil improved by lime-cement columns was evaluated using two different penetration methods, the cone penetration test and the column penetration test. The strength was quantified statistically by the mean, variance and scale of fluctuation, while each test method was analyzed and discussed with a focus on its influence on the design value. Based on the analyses, the column penetration test is suggested as a test method for soil improved by lime-cement columns.

  • 12.
    Bergman, Niclas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Ignat, Razvan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik. Skanska Sverige AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Serviceability Limit State design of lime-cement columns - A reliability-based design approach2014Inngår i: Geotechnical Safety and Risk IV - Proceedings of the 4th International Symposium on Geotechnical Safety and Risk, ISGSR 2013 / [ed] D . Q . Li, London: Taylor & Francis Group, 2014, s. 417-422Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Deep mixing with lime-cement columns is a ground improvement method used to improve the strength and deformation properties of soft cohesive soils. Due to the complex manufacturing process, the variability in the strength and deformation properties is normally high. A rational approach to include variability in the design process is by introducing Reliability-Based Design (RBD). This paper presents a reliability-based design approach for Serviceability Limit State (SLS) design of soil improved by lime-cement columns using the First-Order Reliability Method (FORM). The paper further presents the impact of uncertainties, reliability indices and area replacement ratios on the relationship between the characteristic value and the design value with respect to the column modulus of elasticity.

  • 13.
    Bergman, Niclas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Probabilistic serviceability limit statedesign approach for dry deep mixingManuskript (preprint) (Annet vitenskapelig)
  • 14.
    Bergman, Niclas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Alternativ metod för verifiering av hållfasthet hos kalkcementpelare2013Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1, s. 75-79Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Inom ett doktorandprojekt på Kungliga Tekniska högskolan (KTH) har möjligheten till att använda Jb-totalsondering som testmetod för verifiering av hållfasthet hos kalkcementpelare studerats. Syftet med doktorandprojektet, som är finansierat av Svenska Byggbranschens Utvecklingsfond (SBUF) och Trafikverket, är att öka förståelsen för variationer i hållfasthets- och deformationsegenskaper hos kalkcementpelare och att undersöka variationernas betydelse vid sannolikhetsbaserad dimensionering i bruksstadiet, Bergman (2012).

  • 15.
    Bergman, Niclas
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Comparing column penetration and total–sounding data for lime–cement columns2014Inngår i: Ground Improvement, ISSN 1365-781X, E-ISSN 1751-7621, Vol. 167, nr 4, s. 249-259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In Sweden, the method commonly used for the quality control of lime–cement columns is the column penetration test. However, it is recommended for depths of no more than 8 m because the probe easily deviates from the column at greater depths. As an alternative to facilitate keeping the probe vertical, a centre hole is normally bored in the column using the total-sounding test method. The aim of this paper is to quantify the agreement between the two methods. If there is good agreement, it should be possible to use the less expensive and less time-consuming total-sounding test as a complement to the column penetration test. The analyses suggest good agreement between the methods, and it is therefore suggested that the total-sounding test be used as a complement to the column penetration test in evaluating the average strength properties of a group of medium- and high-strength lime–cement columns.

  • 16.
    Bitir (Buliga), Andreea-Cristina
    et al.
    “Gheorghe Asachi” Technical University of Iaşi.
    Muşat, Vasile
    “Gheorghe Asachi” Technical University of Iaşi.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Laboratory Methods Used to Assess the Mechanical Properties of Soft Soils Improved by Deep Mixing2015Inngår i: Bulletin of the Polytechnic Institute of Jassy, Constructions, Architechture Section, ISSN 1224-3884, E-ISSN 2068-4762, Vol. LXI (LXV), nr 4, s. 165-178Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    In ground improvement projects by deep mixing, the laboratory experimental programis an important stage by which,the suitable binder and quantity are chosen andgeotechnical performances of improvedsoil are evaluated.In current practice, the design process oflime-cement columns ismainlybased on unconfined compressive strength and the corresponding secant Young's modulusevaluated by unconfined compression tests. In this paper, the main laboratory methods used to assess the mechanical properties of improvedsoil mixed with lime and cement in deep mixing are reviewed. Laboratory preparation of the samples and testing procedures for unconfined compression tests, triaxial tests and oedometer testsare presented. In addition,someexperimental results of tests conducted on soft soils mixed with lime and cement are analyzedand commented.

  • 17.
    Bjureland, William
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Sjölander, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Probability distributions of shotcrete parameters for reliability-based analyses of rock tunnel support2019Inngår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 87, s. 15-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A common support measure for underground excavations in jointed rock masses to support loose blocks is to apply a thin shotcrete layer to the periphery of the excavation and systematically install rockbolts into the surrounding rock mass. In this support system, large blocks are carried by the rockbolts and small blocks are carried by the thin shotcrete layer. To verify the shotcrete layer's load-bearing capacity and to stringently account for the large uncertainties incorporated in the variables involved in determining its capacity, analytical calculations in combination with reliability-based methods can be used. However, a lack of knowledge exists regarding the magnitude and uncertainty of shotcrete characteristics (thickness, adhesion, flexural tensile strength, residual flexural tensile strength, and compressive strength), making it difficult to apply reliability-based methods. A statistical quantification of these characteristics is therefore important to facilitate reliability-based methods in design and verification of shotcrete support. In this paper, we illustrate how shotcrete support against small loose blocks can be viewed as a correlated conditional structural system and how this system can be analyzed using reliability-based methods. In addition, we present a unique amount of data for the aforementioned variables, which are all incorporated in the design and verification of a shotcrete layer's ability to sustain loads from small loose blocks. Based on the presented data, we statistically quantify and propose suitable probability distributions for each variable. Lastly, we illustrate how the proposed probability distributions can be used in the design process to calculate the probability of exceeding the shotcrete's load-bearing capacity. Both the probabilistic quantification and the defined correlated conditional structural system along with the illustrative calculation example are followed by a discussion of their implications.

  • 18.
    Bjureland, William
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Influence from spatially varying thickness on shotcrete’s load-bearing capacityManuskript (preprint) (Annet vitenskapelig)
  • 19.
    Bjureland, William
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Prästings, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Challenges in applying fixed partial factors to rock engineering design2017Inngår i: Geotechnical Special Publication, ISSN 0895-0563, nr 283, s. 384-393Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 20.
    Bjureland, William
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Prästings, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Reliability aspects of rock tunnel design with the observational methodManuskript (preprint) (Annet vitenskapelig)
  • 21.
    Bjureland, William
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Prästings, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Reliability aspects of rock tunnel design with the observational method2017Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 98, s. 102-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    According to Eurocode 7, two accepted approaches for managing uncertainty in tunnel design are reliability based methods and the observational method. Reliability-based methods account for uncertainty by acknowledging the random variation of the input parameters; the observational method does this by verifying the expected behavior from an initial design during the course of construction. However, in the framework of the observational method, as defined in Eurocode 7, no guidance is given on the selection of suitable parameters for observation and how they can be linked to the limits of acceptable behavior and, at a sufficiently early stage, the decision for implementing contingency actions. Furthermore, no guidance is given on how to verify that the structure fulfills society's required safety level. In this paper, we present a design procedure for shotcrete-supported rock tunnels that combines reliability-based methods with the observational method. The design procedure applies a deformation-based limit state function for the shotcrete support that is based on the convergence confinement method. We suggest how the requirements in the observational method, as defined in Eurocode 7, may be satisfied for this application. In particular, we focus on the structural reliability aspects. The structural reliability of the preliminary design is assessed with Monte Carlo simulations by calculating the expected deformations of the tunnel. The appropriateness of the preliminary design is then verified by observing the actual deformations during the course of construction. The observed deformations are used to predict the future behavior of the tunnel and to update the assessed probability of unsatisfactory behavior. If the defined deformation-based alarm limit regarding the structural reliability is exceeded, predefined contingency actions are put into operation. The procedure is illustrated with a shotcrete-lined circular rock tunnel and practical aspects in satisfying the reliability requirements with the observational method are discussed.

  • 22.
    Daniels, Markus
    et al.
    Bjerking AB.
    Lovén, Katarina
    Skanska Sverige AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Berg, Joakim
    Skanska Sverige AB.
    Studie visar fördelarna med borrad spont med avseende på markvibrationer2015Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1, s. 36-39Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Då det byggs allt tätare och i känsliga områden blir det allt vanligare att man måste ta hänsyn till markvibrationer. Anläggningsarbeten såsom packning, borrning och pål- och spontinstallationer genererar markvibrationer som kan skada intilliggande bebyggelse, påverka marken negativt samt skapa en otrivsam vistelsemiljö. I känsliga områden är det viktigt att kunna välja rätt metod som skapar acceptabla vibrationsnivåer.

      Det är allmänt vedertaget att vibrationerna som skapas vid installation av borrade stålrör är mindre än vibrationer genererade vid installation av vibrerad spont och slagna pålar. Det har dock inte gått att finna några tillgängliga studier där markvibrationer genererad från borrning respektive vibrerad spont har uppmätts parallellt. Fördelen av att använda borrade stålrör har därför inte kunnat påvisas. Att förutspå vibrationerna analytiskt är mycket komplicerat då det finns ett stort antal parametrar som inverkar på resultatet, både vad det gäller installationsmetoden samt markens beskaffenhet. I Daniels & Lovéns (2014) examensarbete utfört för KTH och Skanska Grundläggning har för första gången en borrad RD-vägg och en vibrerad spont installerats inom samma område med lika markförhållanden samtidigt som vibrationerna uppmätts både i marken och på respektive sponttyp (Figur 1 och 2). Resultaten från undersökningen visar tydligt på skillnaderna i vibrationer och är tänkta att kunna användas vid projektering av spontarbeten där vibrationer blir en faktor att ta hänsyn till.

  • 23.
    Eriksson, Fredrik
    et al.
    Bjerking AB.
    Gemvik, Lina
    Atkins Sverige AB.
    Hov, Sölve
    Atkins Sverige AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    En bortglömd metod: Elektroosmos,jordförstärkning med hjälp av el2015Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1, s. 61-65Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Elektroosmos är en metod för att dränera och förbättra hållfasthetsegenskaperna hos finkorniga jordar. Metoden har visat sig kunna vara upp till hundra gånger snabbare än mekanisk konsolidering med hjälp av till exempel överlast, Lefebvre & Burnotte (2002). I dagens projekt är både de ekonomiska och miljömässiga aspekterna kanske viktigare än någonsin, och elektroosmos har visat sig kunna vara både miljövänlig och ekonomiskt fördelaktig vilket skulle kunna göra den till en användbar metod i många projekt med geotekniska problem. Som exempel visade Lamont Black & Weltman (2010) i ett projekt med stabilitetsproblem att klimatpåverkan, i form av utsläpp av växthusgaser, minskade med 47 procent vid användande av elektroosmos i jämförelse med till exempel jordspikning. Även kostnaderna minskade med 26 procent jämfört med andra jämförbara metoder. I ett examensarbete, Eriksson & Gemvik (2014), utfört för KTH, Atkins Sverige AB och Sweco Geolab har leror från tre olika platser i Sverige behandlats med elektroosmos. Resultaten visar att elektroosmos effektivt kan dränera en finkornig jord och avsevärt öka dess hållfasthetsparametrar

  • 24.
    Ghaderi, Abdolvahed
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Abbaszadeh Shahri, Abbas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik. Islamic Azad Univ, Roudehen Branch, Fac Civil Engn, Tehran, Iran..
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    An artificial neural network based model to predict spatial soil type distribution using piezocone penetration test data (CPTu)2019Inngår i: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 78, nr 6, s. 4579-4588Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Soil types mapping and the spatial variation of soil classes are essential concerns in both geotechnical and geoenvironmental engineering. Because conventional soil mapping systems are time-consuming and costly, alternative quick and cheap but accurate methods need to be developed. In this paper, a new optimized multi-output generalized feed forward neural network (GFNN) structure using 58 piezocone penetration test points (CPTu) for producing a digital soil types map in the southwest of Sweden is developed. The introduced GFNN architecture is supported by a generalized shunting neuron (GSN) model computing unit to increase the capability of nonlinear boundaries of classified patterns. The comparison conducted between known soil type classification charts, CPTu interpreting procedures, and the outcomes of the GFNN model indicates acceptable accuracy in estimating complex soil types. The results show that the predictability of the GFNN system offers a valuable tool for the purpose of soil type pattern classifications and providing soil profiles.

  • 25.
    Holm, Göran
    et al.
    Statens geotekniska institut.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Beyer, Fredrik
    Batman, Mathew
    Genberg, Cristian
    Geokonstruktioner av stabiliserade/solidifierade förorenade muddermassor2009Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1, s. 46-51Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 26.
    Hov, Sölve
    et al.
    GeoMind/LabMind.
    Prästings, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Persson, Erik
    Bjerking.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    On empirical correlations for normalised shear strengths from fall cone and direct simple shear tests in soft Swedish clays2019Inngår i: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Artikkel i tidsskrift (Fagfellevurdert)
  • 27.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska Sweden AB.
    Holmén, Martin
    Swedish Geotechnical Institute.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Triaxial Extension and Tension behavior of Lime-Cement improved clayManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The performance of Deep Mixing columns installed on the passive side of excavation supporting structures was investigated by means of two instrumented full-scale tests conducted in Enköping, in eastern Sweden, during 2014. In these tests, a braced steel sheet pile wall interacting with panels of overlapping Dry Deep Mixing columns was excavated and loaded to failure. This paper present the results of a series of undrained and drained isotropic consolidated triaxial extension, tension and compression laboratory tests on lime-cement improved clay with a binder of lime-cement similar to that used in the experimental field tests. The different stress paths to failure, with the purpose to reflect the stress path to failure from the experimental field tests, were obtained by varying the direction of the major and minor principle stresses in a conventional triaxial test cell. The undrained tests revealed that at low consolidation stresses, corresponding to depth of approximately 0-10 m below the ground surface, significant stress induced anisotropy was observed depending on the direction of the major and minor principle stresses. Based on undrained triaxial test results, a relationship between the undrained strength, effective consolidation stress and OCR is presented for different stress paths to failure.

    The experimental data of the drained tests show that a failure surface comprising of a shear failure function based on Mohr-Coulomb failure criterion and a tensile failure function based on the tensile strength and the confining stress can be applied for lime-cement stabilized clay.

  • 28.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska Sweden AB.
    Karstunen, Minna
    Chalmers Institute of Technology.
    Liedberg, Sven
    Skanska Sweden AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Numerical analyses of an experimental excavation supported by panels of lime-cement columnsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The influence of ground improvement with panels of overlapping lime-cement columns on the behavior of a braced excavation loaded to failure has been investigated using 3D numerical analyses and compared with a reported experimental failure test. The dependency of the mobilized column strength on the stress path to failure was considered by assessing the strength criteria based on results from isotropically consolidated undrained triaxial extension tests. For comparison, the problem is also analyzed with isotropic column material parameters determined from unconfined compression tests. The analyses reveal that stress-induced strength anisotropy of lime-cement improved clay needs to be considered when the stress path for the actual field conditions differs from that in conventional laboratory testing. The failure loads, and also the location of the failure surface predicted by the FE-analyses, were in good agreement with the field tests. On the other hand, analyses conducted with column strength parameters, evaluated from unconfined compression tests, significantly over-predicted the failure load of the experimental tests. In addition to strength parameters, the modulus of deformation that is consistent with the actual encountered stress path is also needed to predict reasonable results.

  • 29.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Field test of braced excavation supported wth rows of dry deep mixing columns2015Inngår i: Proceedings of the Deep Mixing 2015 Conference, Deep Foundation Institute , 2015, s. 573-580, artikkel-id 2079Konferansepaper (Fagfellevurdert)
  • 30.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska Sweden AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Liedberg, Sven
    Skanska Sweden AB.
    Two- and three-dimensional analyses of excavation support with rows of dry deep mixing columns2015Inngår i: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 66, s. 16-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a 2D model of an excavation with a tied back sheet pile wall in interaction with perpendicular rows of deep dry mixed overlapping columns was compared to a 3D model. A method to take into consideration the effect of the overlap zones between columns in a 2D model, where the improved soil was modeled as a composite material, was investigated and the results between the 2D and 3D analyses were compared with focus on predicted failure load, failure mechanism and deformations. The results of this numerical study show that both the area improvement ratio of the improved soil and the quality of the overlap zone has a significant influence on how well a 2D model that incorporates the overlap zone between columns, performs compared to the 3D model.

  • 31.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska Sverige AB.
    Liedberg, Sven
    Skanska Sverige AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Behavior of braced excavation supported by panels of deep mixing columns2016Inngår i: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 53, nr 10, s. 1671-1687Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the instrumentation, execution and performance of two full-scale tests where a braced steel sheet pile wall interacting with rows of overlapping dry deep mixing columns was excavated and then loaded to failure. The purpose of these tests was to provide knowledge of the behavior of deep mixing column rows located in passive zone and interacting with a retaining structure. Both tests were extensively instrumented on the active as well as on the passive side of the retaining structure. In both conducted tests a stability failure of the retaining structure occurred, resulting in heave at the bottom of the excavation and large settlements of the ground surface behind the sheet pile wall. For a spacing between LC-panels of 3.0 m a very brittle failure developed suddenly in the clay between the panels with small deformations prior to failure. In the second test, with a spacing of 1.5 m between LC-panels, the failure developed in the LC-panels as well as in the clay between the panels. Even if a similar failure mechanism developed, measured horizontal displacements, horizontal stresses, and pore pressure response prior to failure differed between the tests.

  • 32.
    Ignat, Razvan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska.
    Liedberg, Sven
    Skanska.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Djupstabilisering med kalkcementpelarskivor för förstärkning av djupa schakter2017Konferansepaper (Annet vitenskapelig)
  • 33.
    Ignat, Razvan
    et al.
    Skanska AB.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska AB.
    Studie av 2D/3D numeriskmodellering av kalkcementpelare installerade som överlappande skivor2014Inngår i: Bygg & teknik, ISSN 0281-658X, Vol. 1, s. 80-83Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 34.
    Kardan, Caesar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Nik, Leyla
    Geosigma.
    Viking, Kenneth
    NCC Teknik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    CPTu: Kan vi lita på sonderingsresultaten?2015Inngår i: Bygg & teknik, ISSN 0281-658X, nr 1, s. 53-58Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    I geotekniska utredningar ingår behovet av att kunna bestämma markförhållanden och jordens egenskaper. Ett antal sonderingsmetoder har utvecklats för detta ändamål och CPTu (Cone Penetration Test med portrycksmätning) betraktas som en av de mer sofistikerade. Denna metod ställer dock höga krav på alla aktörer i processen, det vill säga fältgeotekniker, handläggande geotekniker, geokonstruktörer men även beställaren. Ett vanligt problem med CPTu är osäkerheten i resultaten, osäkerheter kopplat till både utrustning och handhavande. Trots att det idag finns ramverk avseende användning, prestanda, underhåll och andra detaljer, finns det fortfarande en grad av osäkerhet i resultaten. Hur stor denna osäkerhet är och vilka faktorer som inverkar har översiktligt studerats i form av ett examensarbete på KTH Jord- och bergmekanik, under 2014,Kardan (2014), i samarbete med övriga medförfattare. Resultat från studien visar tydligt på skillnader i resultat, en skillnad som är kopplat till både aktörens utrustning och handhavande.

  • 35.
    Kardan, Caesar
    et al.
    Ramböll, Sweden.
    Viking, Kenneth
    NCC, Sweden.
    Nik, Leila
    Geosigma, Sweden.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Influence of operator performance on quality of CPTu results2016Inngår i: Challenges in Nordic Geotechnic, The Icelandic Geotechnical Society , 2016, s. 153-158Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cone penetration tests (CPT) is one of the most sophisticated geotechnical field investigations methods. As for all test methods, the CPT is associated with many uncertainties. However,there are two main sources that have aninfluence on the quality ofCPTumeasurements. One is the choice of equipment since different equipment differs in design and functionality.The other source relates tooperator performanceand incorrectexecutionof the methodas well as lack of competence to analyze the results.However, inorder to achieve satisfying results, the operator should be skilled, competent and well-educated. Some countries don’t have any formal education and in countries wereformal education doexist, the achieved quality ofresultsdoesquite frequentlystill come out unsatisfactory.This fact is seldom mentioned, but still a well-known fact amongst practicing geotechnicians.The objective of this paperis to discuss operator performance related factors and contribute to a better knowledgeof how important every single procedure contributes to the outcome as well as quality of the results.

  • 36.
    Krounis, Alexandra
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Shear strength of partially bonded concrete-rock interfaces for application in dam stability analyses2016Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, nr 7, s. 2711-2722Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The shear strength of the concrete–rock interface has a substantial influence on the sliding stability of concrete gravity dams founded on rock. While several studies have been done on concrete–rock contacts, there remains uncertainty regarding the peak shear strength of partially bonded interfaces. There exists, in particular, an uncertainty regarding the contribution from surface roughness of the unbonded parts to the peak shear strength of the interface due to the dependency of mobilized strength on shear displacement. In this study, a series of 24 direct shear tests are performed under CNL conditions on concrete–rock samples with different bonding conditions. Tests on samples with fully bonded and unbonded interfaces are conducted to study the strain compatibility of the different contacts, while the results of samples with partially bonded interfaces are evaluated in the context of linking the joint roughness of the unbonded parts to the peak shear strength of the interface. The results indicate that a significant part of the surface roughness of the unbonded parts is mobilized prior to degradation of bond strength, in particular for interfaces with low bonding percentages. It is recommended that further research should be conducted to understand how the contribution from roughness change with an increase in scale and degree of matedness.

  • 37.
    Krounis, Alexandra
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Spross, Johan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Influence of cohesive strength in probabilstic sliding stability re-assessment of concrete dams2016Inngår i: Journal of Geotechnical and Geoenvironmental Engineering, ISSN 1090-0241, E-ISSN 1943-5606, Vol. 143, nr 2, artikkel-id 04016094Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For concrete dams, cohesive strength often constitutes a significant share of the overall shear strength of partially bonded concrete-rock interfaces. However, cohesive strength is also associated with great uncertainties that may have a significant impact on the assessed stability of the analyzed structure. In this paper, the merits of including cohesion are evaluated using a probability-based approach to analyze the sliding stability of an existing concrete gravity dam. The shear strength properties of the interface are inferred from a limited number of site-specific tests and previous knowledge from similar structures using Bayesian updating. The study shows that the potential gain from cohesive strength is strongly related to the involved uncertainties and identifies the bonding percentage and basic friction angle as the most influential parameters. The importance of testing, both with regard to the specific project and for future projects, is also highlighted.

  • 38.
    Krounis Guerrero, Alexandra
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Effects of spatial variation in cohesion over the concrete-rock interface on dam sliding stability2015Inngår i: Journal of Rock Mechanics and Geotechnical Engineering, ISSN 1674-7755, Vol. 7, nr 6, s. 659-667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The limit equilibrium method (LEM) is widely used for sliding stability evaluation of concrete gravity dams. Failure is then commonly assumed to occur along the entire sliding surface simultaneously. However, the brittle behaviour of bonded concrete-rock contacts, in combination with the varying stress over the interface, implies that the failure of bonded dam-foundation interfaces occurs progressively. In addition, the spatial variation in cohesion may introduce weak spots where failure can be initiated. Nonetheless, the combined effect of brittle failure and spatial variation in cohesion on the overall shear strength of the interface has not been studied previously. In this paper, numerical analyses are used to investigate the effect of brittle failure in combination with spatial variation in cohesion that is taken into account by random fields with different correlation lengths. The study concludes that a possible existence of weak spots along the interface has to be considered since it significantly reduces the overall shear strength of the interface, and implications for doing so are discussed.

  • 39.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Binder distribution in lime-cement columns2001Inngår i: Ground Improvement, ISSN 1365-781X, E-ISSN 1751-7621, Vol. 5, nr 3, s. 111-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mixing of soil and binders is a very complex process. The object of the mixing process is to distribute the binder and to achieve a satisfactory mixture for the particular purpose. The requirements on homogeneity may differ for each application. The assessment and definition of mixing quality are difficult and very expensive. This paper discusses the concept of mixing quality with respect to the binder distribution, and the use of mixing indices, as a quantitative assessment. The possibility of using mixing indices with the lime–cement column method is taken up. Statistical analysis was performed on a number of samples taken from four lime–cement columns at Arboga, Sweden. The sampling methodology, the scale of scrutiny and thus the influence of the sample size are discussed. The study shows that mixing indices can be used as a quantitative measure of the mixing quality. The results indicate that the sample size has a considerable influence when the mixing quality is poor and a lesser influence when the mixing quality is relatively good. It is also shown that it is difficult to draw conclusions concerning binder distribution from only a few samples, since the distribution may vary. With more extensive knowledge, it may be possible to assess the mixing quality from only a few samples.

  • 40.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Inblandningsprocessen vid kemiskdjupstabilisering - en översikt2000Inngår i: Proc. of the 12th Nordic Geotechnical Meeting, 2000, s. 241-250Konferansepaper (Annet vitenskapelig)
  • 41.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    On the use of CPT for quality assessment of lime-cement columns2005Inngår i: Proceedings of the International Conference on Deep Mixing: Best Practice and Recent Advances, 2005, s. 555-560Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents results from a somewhat unusual application, where CPT was performed inclined in order to investigate the overlapping zone in lime-cement column rows. The column rows had been subjected to large movements due to an embankment failure. The discussion touches upon the evaluation of strength properties, advantages and major drawbacks. The results show that the upper part of the column rows was held together in spite of the fact that the rows had been subjected to large movements. However, the value of using CPT with respect to the assessment of strength properties is strongly questioned due to the small probe size.

  • 42.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Recent Developments in Deep Mixing Research in Sweden2013Konferansepaper (Annet vitenskapelig)
  • 43.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Reliabilityanalysis and design issues of ground improvement by deep mixing2012Konferansepaper (Annet vitenskapelig)
  • 44.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Shear box apparatus for modelling chemicalstabilised soil - introductory tests1999Inngår i: Dry Mix Methods for Deep Soil Stabilization, Balkema, 1999, s. 115-121Konferansepaper (Fagfellevurdert)
  • 45.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    State of Practice Report: Execution, monitoring and quality control2005Inngår i: Proceedings of the International Conference on Deep Mixing: Best Practice and Recent Advances, 2005, s. 732-785Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The state of practice of deep mixing concerning execution, monitoring and quality control is highlighted and discussed. Important recently published publications and different deep mixing methods are briefly reviewed. The mixing process in-situ is described and present knowledge concerning influencing factors are reviewed and discussed. The quality control concept of deep mixing is discussed and control methods are reviewed. The extent of testing and the evaluated strength- and deformation properties are discussed. The concept quality and variability in deep mixing are discussed.

  • 46.
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    The mixing process at the dry jet mixing method1999Inngår i: Dry Mix Methods for Deep Soil Stabilization / [ed] H.Bredenberg/G.Holm / B.B.Broms, Balkema, 1999, s. 339-346Konferansepaper (Fagfellevurdert)
  • 47.
    Larsson, Stefan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Adevik, Sebastian
    Ignat, Razvan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Baker, Sadek
    Skanska Sverige AB.
    A case study on the effect of using surcharge fill as a complement to ground improvement with dry deep mixing2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Uncertain strength, deformation and flowproperties in dry deep mixing columns often lead to conservative choicesconcerning design values where the design is regularly complemented with asurcharge fill.  The surcharge not onlyleads to increased cost but also to logistical problems where the surcharge isa physical obstacle.  The deformationproperties of a ground improvement were studied by means of two smallembankment load tests.  The settlementmeasurements were also used in FEM analyses, where the effect of surcharge oncreep settlements was investigated.  Basedon the results, the effects of the surcharge were considered negligible and couldsafely be ignored.  The project is anexample how the contractor can use a field test as an effective designapproach.

  • 48.
    Larsson, Stefan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Ahnberg, Helen
    Ignat, Razvan
    Baker, Sadek
    Discussion of "Numerical Modeling of Geotextile-Reinforced Embankments over Deep Cement Mixed Columns Incorporating Strain-Softening Behavior of Columns" by N. N. S. Yapage, D. S. Liyanapathirana, H. G. Poulos, R. B. Kelly, and C. J. Leo2015Inngår i: International Journal of Geomechanics, ISSN 1532-3641, E-ISSN 1943-5622, Vol. 15, nr 4, artikkel-id 07014008Artikkel i tidsskrift (Fagfellevurdert)
  • 49.
    Larsson, Stefan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Al-Naqshabandy, Muhammed
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Bergman, Niclas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Ignat, Razvan
    SVR, C02, Skanska Sverige AB.
    Kalkcementpelare: forskningen på KTH med industrisamverkan2012Inngår i: Samhällsbyggaren, ISSN 2000-2408, nr 4, s. 14-18Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 50.
    Larsson, Stefan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Axelsson, Morgan
    Rehnman, Sven-Erik
    On the assessment of the mixing quality whenusing the dry jet mixing method2000Inngår i: Proceedings of the 4th GIGS, Int. Conf. on Ground Impr. Geosystems, 2000, s. 99-108Konferansepaper (Fagfellevurdert)
123 1 - 50 of 118
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