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de Frias Lopez, R., Larsson, S. & Silfwerbrand, J. (2019). A discrete element material model including particle degradation suitable for rockfill embankments. Computers and geotechnics, 115, Article ID 103166.
Open this publication in new window or tab >>A discrete element material model including particle degradation suitable for rockfill embankments
2019 (English)In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 115, article id 103166Article in journal (Refereed) Published
Abstract [en]

A material model for future implementation in high rockfill embankments has been developed using discrete elements. Compared to previous modelling of railway ballast representing particles as clumps of spheres with bonded asperities, much simpler breakable clumps are used. This allows considering not only corner breakage but also particle splitting without a prohibitive computational time, something unique when modelling three-dimensional assemblies of particles. Moreover, breakage is controlled by values of contact forces and particle loading configuration, resulting in significantly fewer parameters and with a much clearer physical meaning. All in all, it results in a more computationally efficient and robust model suitable for implementation in rockfill embankments. Numerical monotonic and cyclic triaxial tests are performed under a range of low deviatoric to confinement stress ratios, as anticipated for railway embankments. A comparable degree of resemblance to empirical results as the previous modelling efforts with bonded asperities is observed when including degradation. Results at particle level proved useful to partially explain the observed macroscopic responses; however, these were substantially affected by breakage and none of the studied variables could, on its own, satisfactorily fully explain the observed behaviour. As a matter of fact, a complex interdependency of different factors, both at particle and macroscopic level, was identified that ultimately explained the macroscopic response. The key contribution is thus presenting an efficient and realistic material model specifically aimed at modelling high rockfill embankments including degradation, something not attempted to date.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Discrete element modeling, Granular materials, Particle degradation, Particle-scale behavior, Rockfill embankment, Ballast (railroad track), Railroads, Rock mechanics, Rocks, Computationally efficient, Cyclic tri-axial tests, Macroscopic response, Particle scale, Rock-fill embankments, Three-dimensional assembly, Embankments, breakage, degradation, discrete element method, embankment dam, granular medium, rockfill dam, three-dimensional modeling, triaxial test
National Category
Construction Management
Research subject
Civil and Architectural Engineering, Soil and Rock Mechanics
Identifiers
urn:nbn:se:kth:diva-263509 (URN)10.1016/j.compgeo.2019.103166 (DOI)2-s2.0-85071493258 (Scopus ID)
Note

QC 20191202

Available from: 2019-12-02 Created: 2019-12-02 Last updated: 2019-12-04Bibliographically approved
Ghaderi, A., Abbaszadeh Shahri, A. & Larsson, S. (2019). An artificial neural network based model to predict spatial soil type distribution using piezocone penetration test data (CPTu). Bulletin of Engineering Geology and the Environment, 78(6), 4579-4588
Open this publication in new window or tab >>An artificial neural network based model to predict spatial soil type distribution using piezocone penetration test data (CPTu)
2019 (English)In: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 78, no 6, p. 4579-4588Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
SPRINGER HEIDELBERG, 2019
Keywords
Soil type mapping, Cone penetration test, Artificial neural network
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-259422 (URN)10.1007/s10064-018-1400-9 (DOI)000482240400049 ()2-s2.0-85055539172 (Scopus ID)
Note

QC 20190924

Available from: 2019-09-24 Created: 2019-09-24 Last updated: 2019-09-24Bibliographically approved
Prästings, A., Spross, J. & Larsson, S. (2019). Characteristic values of geotechnical parameters in Eurocode 7. Proceedings of the Institution of Civil Engeneers: Geotechnical Engineering, 172(4), 301-311
Open this publication in new window or tab >>Characteristic values of geotechnical parameters in Eurocode 7
2019 (English)In: Proceedings of the Institution of Civil Engeneers: Geotechnical Engineering, ISSN 1353-2618, E-ISSN 1751-8563, Vol. 172, no 4, p. 301-311Article in journal (Refereed) Published
Abstract [en]

Lack of harmonisation between reliability-based design and the partial factor method in Eurocode 7 (EN 1997-1:2004) is preventing the widespread introduction of a risk-based concept in geotechnical design. This paper discusses how uncertainties are managed according to EN 1997-1:2004 and possible implications of not harmonising the current safety format with reliability-based design. One of several challenges highlighted is how EN 1997-1:2004 defines the characteristic value and design value. The characteristic value is therein defined based on a classical frequentist approach through a confidence interval. From a Bayesian point of view, the current definition does not treat the characteristic value as an uncertain variable. Consequently, the definitions of the characteristic value and design value in EN 1997-1:2004 feature weak connections between uncertainties in the geotechnical properties and the consequences of failure, as regulated by the target reliability index.

Place, publisher, year, edition, pages
ICE Publishing, 2019
Keywords
codes of practice & standards, geotechnical engineering, risk & probability analysis
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-255551 (URN)10.1680/jgeen.18.00057 (DOI)000475709400002 ()2-s2.0-85068838228 (Scopus ID)
Note

QC 20190805

Available from: 2019-08-05 Created: 2019-08-05 Last updated: 2019-08-20Bibliographically approved
Abbaszadeh Shahri, A., Spross, J., Johansson, F. & Larsson, S. (2019). Landslide susceptibility hazard map in southwest Sweden using artificial neural network. Catena (Cremlingen. Print), 183, Article ID UNSP 104225.
Open this publication in new window or tab >>Landslide susceptibility hazard map in southwest Sweden using artificial neural network
2019 (English)In: Catena (Cremlingen. Print), ISSN 0341-8162, E-ISSN 1872-6887, Vol. 183, article id UNSP 104225Article in journal (Refereed) Published
Abstract [en]

Landslides as major geo-hazards in Sweden adversely impact on nearby environments and socio-economics. In this paper, a landslide susceptibility map using a proposed subdivision approach for a large area in southwest Sweden has been produced. The map has been generated by means of an artificial neural network (ANN) model developed using fourteen causative factors extracted from topographic and geomorphologic, geological, land use, hydrology and hydrogeology characteristics. The landslide inventory map includes 242 events identified from different validated resources and interpreted aerial photographs. The weights of the causative factors employed were analyzed and verified using accepted mathematical criteria, sensitivity analysis, previous studies, and actual landslides. The high accuracy achieved using the ANN model demonstrates a consistent criterion for future landslide susceptibility zonation. Comparisons with earlier susceptibility assessments in the area show the model to be a cost-effective and potentially vital tool for urban planners in developing cities and municipalities.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Landslide, GIS, Sweden, Artificial neural network
National Category
Earth and Related Environmental Sciences
Research subject
Civil and Architectural Engineering, Soil and Rock Mechanics
Identifiers
urn:nbn:se:kth:diva-262756 (URN)10.1016/j.catena.2019.104225 (DOI)000488417700047 ()2-s2.0-85071591343 (Scopus ID)
Note

QC 20191023

Available from: 2019-10-23 Created: 2019-10-23 Last updated: 2019-12-03Bibliographically approved
Hov, S., Prästings, A., Persson, E. & Larsson, S. (2019). On empirical correlations for normalised shear strengths from fall cone and direct simple shear tests in soft Swedish clays. Geotechnical and Geological Engineering
Open this publication in new window or tab >>On empirical correlations for normalised shear strengths from fall cone and direct simple shear tests in soft Swedish clays
2019 (English)In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed) Submitted
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-256056 (URN)
Note

QC 20190823

Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2019-08-23Bibliographically approved
Bjureland, W., Johansson, F., Sjölander, A., Spross, J. & Larsson, S. (2019). Probability distributions of shotcrete parameters for reliability-based analyses of rock tunnel support. Tunnelling and Underground Space Technology, 87, 15-26
Open this publication in new window or tab >>Probability distributions of shotcrete parameters for reliability-based analyses of rock tunnel support
Show others...
2019 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 87, p. 15-26Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-246439 (URN)10.1016/j.tust.2019.02.002 (DOI)000462421100002 ()2-s2.0-85061199710 (Scopus ID)
Note

QC 20190329

Available from: 2019-03-29 Created: 2019-03-29 Last updated: 2019-05-02Bibliographically approved
Ignat, R., Baker, S., Holmén, M. & Larsson, S. (2019). Triaxial extension and tension tests on lime-cement-improved clay. Soil and foundation
Open this publication in new window or tab >>Triaxial extension and tension tests on lime-cement-improved clay
2019 (English)In: Soil and foundation, ISSN 0038-0806Article in journal (Refereed) Published
Abstract [en]

This paper presents the results of a series of undrained and drained isotropic consolidated triaxial extension, tension and compression laboratory tests on lime-cement-improved very soft clay. The main objective of these tests was to investigate the material strength and stiffness properties for stress conditions similar to those expected on the passive side of excavations where a retaining structure is supported by Deep Mixing columns. The different stress paths to failure were obtained by varying the directions of the major and minor principal stresses in a conventional triaxial test cell. The undrained tests conducted at low consolidation stresses, corresponding to depths of approximately 0–10 m below the ground surface, revealed significant differences in undrained strength depending on the directions of the major and minor principal stresses, indicating anisotropic material behavior. Based on the undrained triaxial test results, the relationship among the undrained strength, the effective consolidation stress and the over-consolidation ratio (OCR) is presented for different stress paths to failure. The experimental data from the drained tests show that a failure surface comprised of a shear failure function based on the 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.

Place, publisher, year, edition, pages
Elsevier B.V., 2019
Keywords
Dry deep mixing, Mobilized strength, Stress paths, Triaxial tests, Cements, Lime, Mixing, Surface testing, Tensile strength, Tensile testing, Conventional triaxial test, Deep mixing, Mohr-Coulomb failure criterion, Over consolidation ratio, Tension and compression, Undrained triaxial test, Strength of materials
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-263267 (URN)10.1016/j.sandf.2019.06.004 (DOI)2-s2.0-85070084689 (Scopus ID)
Note

QC 20191106

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-06Bibliographically approved
Wonglert, A., Jongpradist, P., Jamsawang, P. & Larsson, S. (2018). Bearing capacity and failure behaviors of floating stiffened deep cement mixing columns under axial load. Soil and foundation, 58(2), 446-461
Open this publication in new window or tab >>Bearing capacity and failure behaviors of floating stiffened deep cement mixing columns under axial load
2018 (English)In: Soil and foundation, ISSN 0038-0806, Vol. 58, no 2, p. 446-461Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Japanese Geotechnical Society, 2018
Keywords
DCM, SDCM, Bearing capacity, Failure, Numerical analysis, Physical model
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:kth:diva-230549 (URN)10.1016/j.sandf.2018.02.012 (DOI)000432690700015 ()2-s2.0-85042184222 (Scopus ID)
Note

QC 20180620

Available from: 2018-06-20 Created: 2018-06-20 Last updated: 2018-06-20Bibliographically approved
Wersäll, C., Nordfelt, I. & Larsson, S. (2018). Effektivare packning med nya insikter. Bygg & Teknik (1), 44-45
Open this publication in new window or tab >>Effektivare packning med nya insikter
2018 (Swedish)In: Bygg & Teknik, ISSN 0281-658X, no 1, p. 44-45Article in journal (Other academic) Published
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-238695 (URN)
Note

QC 20181108

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2019-10-30Bibliographically approved
Abbaszadeh Shahri, A., Spross, J., Johansson, F. & Larsson, S. (2018). Kartering av skredbenägenhet medartificiell intelligens. Bygg & teknik (1)
Open this publication in new window or tab >>Kartering av skredbenägenhet medartificiell intelligens
2018 (Swedish)In: Bygg & teknik, ISSN 0281-658X, no 1Article in journal (Other academic) Published
Place, publisher, year, edition, pages
Förlags AB Bygg & teknik, 2018
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:kth:diva-238799 (URN)
Note

QC 20181214

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2018-12-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9615-4861

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