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Bjureland, W., Johansson, F., Spross, J. & Larsson, S. (2020). Influence of spatially varying thickness on load-bearing capacity of shotcrete. Tunnelling and Underground Space Technology, 98, Article ID 103336.
Open this publication in new window or tab >>Influence of spatially varying thickness on load-bearing capacity of shotcrete
2020 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 98, article id 103336Article in journal (Refereed) Published
Abstract [en]

A common approach to verify a shotcrete layer's ability to secure blocks that can exist between rockbolts in a tunnel is to use analytical calculations. For this situation, an attractive approach to account for variability in the shotcrete parameters is to use reliability-based methods. Variability can then be accounted for by assigning suitable probability distributions to all relevant input parameters. Structural safety can be ensured by verifying that the probability of limit exceedance is smaller than an acceptable target probability of failure. However, even though analytical calculations and reliability-based methods can be used to design shotcrete support, one of the commonly made basic assumptions is that the load-bearing capacity of the shotcrete is governed by the spatial average of the input parameters. Thus, the spatial variability of the parameters are neglected. As a result, if the capacity is governed by the lowest value of a certain parameter, this assumption is non-conservative. In this paper, we present a novel approach in which the minimum of either the spatial average of a shotcrete slab of varying thickness, or the spatial average along the periphery of a loose block of that same slab, is used to estimate the load-bearing capacity of the shotcrete in a tunnel. The approach is based on results from numerical simulations of a shotcrete slab that we perform to investigate the effect that a spatially varying thickness has on the flexural load-bearing capacity of the slab. The results from the simulations show that the shotcrete's flexural load-bearing capacity might be overestimated when using the spatial average of shotcrete thickness between four rockbolts in design. Using the presented approach, the spatial variability of shotcrete thickness can be accounted for in practical design of tunnels without complex and time-consuming numerical simulations.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Rock engineering, Tunnel, Shotcrete, Reliability-based methods
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-271498 (URN)10.1016/j.tust.2020.103336 (DOI)000518873900023 ()2-s2.0-85079122118 (Scopus ID)
Note

QC 20200422

Available from: 2020-04-22 Created: 2020-04-22 Last updated: 2020-04-27Bibliographically approved
Hellgren, R., Malm, R., Fransson, L., Johansson, F. & Westberg Wilde, M. (2020). Measurement of ice pressure on a concrete dam with a prototype ice load panel. Cold Regions Science and Technology, 170, Article ID 102923.
Open this publication in new window or tab >>Measurement of ice pressure on a concrete dam with a prototype ice load panel
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2020 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 170, article id 102923Article in journal (Refereed) Published
Abstract [en]

This paper presents the development and installation of a prototype ice load panel and measurements of ice load from February 2016 to February 2018 at the Rätan hydropower dam in Sweden. The design of the 1 × 3 m2 panel enables direct measurement of ice pressure on the concrete surface is based on previous experience from similar measurements with sea ice. Important features of the design are sufficient height and width to reduce scale effects and to cover the ice thickness and variations in water level. The Rätan dam was chosen based on several criteria so that the ice load is considered to be reasonably idealized against the dam structure.

For the three winters 2016, 2016/2017, 2017/2018, the maximum ice load recorded was 161 kN/m, 164 kN/m and 61 kN/m respectively. There were significant daily fluctuations during the cold winter months, and the daily peak ice loads showed a visual correlation with the daily average temperature and with the daily pattern of operation of the power station with its corresponding water level variations.

Place, publisher, year, edition, pages
Elsevier, 2020
National Category
Engineering and Technology Building Technologies
Research subject
Civil and Architectural Engineering, Structural Engineering and Bridges
Identifiers
urn:nbn:se:kth:diva-264210 (URN)10.1016/j.coldregions.2019.102923 (DOI)000506666000001 ()2-s2.0-85075037308 (Scopus ID)
Note

QC 20191125

Available from: 2019-11-23 Created: 2019-11-23 Last updated: 2020-02-14Bibliographically 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
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
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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: 2020-05-12Bibliographically approved
Stille, B., Johansson, F., Ríos Bayona, F., Batres Estrada, R. & Roslin, M. (2019). Stockholm bypass project – passage under the Lake Mälaren. In: Daniele Peila, Giulia Viggiani, Tarcisio Celestino (Ed.), Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art- Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), May 3-9, 2019, Naples, Italy. Paper presented at World Tunnel Congress, WTC 2019 and the 45th General Assembly of the International Tunnelling and Underground Space Association, ITA-AITES 2019, 3 May 2019 through 9 May 2019 (pp. 1569-1578). London: CRC Press
Open this publication in new window or tab >>Stockholm bypass project – passage under the Lake Mälaren
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2019 (English)In: Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art- Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), May 3-9, 2019, Naples, Italy / [ed] Daniele Peila, Giulia Viggiani, Tarcisio Celestino, London: CRC Press, 2019, p. 1569-1578Conference paper, Published paper (Refereed)
Abstract [en]

In the last years, the Swedish Transport Administration has been working on improving and expanding road communications in Sweden. The Stockholm Bypass Project, one of the biggest projects in Swedish history, consists of a 21 km long highway that goes around the city from north to south. In order to reduce the environmental impact, 17 km of the total length will be excavated underground passing through several regional fault zones and subsea passages. One of the most difficult technical challenges in this project is the passage under the Lake Mälaren and the regional fault zone in the Fiskar fjord. This paper presents the utilized methodology to design the temporary rock support and to manage the risks and uncertainties for the excavation through the fault zone, which mainly originate from the limited information about the rock conditions and the relatively large width of the tunnels.

Place, publisher, year, edition, pages
London: CRC Press, 2019
Keywords
Environmental impact, Lakes, Office buildings, Tunneling (excavation), Fault zone, Limited information, Risks and uncertainties, Rock conditions, Rock support, Stockholm, Technical challenges, Total length, Tunnels
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-262472 (URN)10.1201/9780429424441-166 (DOI)2-s2.0-85068361697 (Scopus ID)9781138388659 (ISBN)9780429424441 (ISBN)
Conference
World Tunnel Congress, WTC 2019 and the 45th General Assembly of the International Tunnelling and Underground Space Association, ITA-AITES 2019, 3 May 2019 through 9 May 2019
Note

QC 20191017

Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-17Bibliographically approved
Ríos Bayona, F., Stigsson, M., Johansson, F. & Mas Ivars, D. (2018). Comparison between shear strength based on Barton’s roughness profiles and equivalent synthetic profiles based on fractal theory. In: 52nd U.S. Rock Mechanics/Geomechanics Symposium: . Paper presented at 52nd U.S. Rock Mechanics/Geomechanics Symposium, 17 June 2018 through 20 June 2018, Seattle, WA, USA. American Rock Mechanics Association (ARMA)
Open this publication in new window or tab >>Comparison between shear strength based on Barton’s roughness profiles and equivalent synthetic profiles based on fractal theory
2018 (English)In: 52nd U.S. Rock Mechanics/Geomechanics Symposium, American Rock Mechanics Association (ARMA) , 2018Conference paper, Published paper (Refereed)
Abstract [en]

A comprehensive understanding of the shear strength and the mechanical behavior of rock joints is to some extent still missing today. Several attempts have been made to develop empirical and analytical shear strength criteria that explain this mechanism. One of the most important parameters governing the shear strength of rock fractures is the surface roughness, which is generally determined using the Joint Roughness Coefficient (JRC). This parameter is often determined subjectively in the field by comparison with 10 predefined roughness profiles. Recent studies indicate that surface roughness can be accurately represented by using fractal analysis. The aim of this study is to perform a first attempt to investigate the mechanical equivalence in terms of the peak shear strength between synthetic rock fractures, where the surface roughness has been generated using fractal theory, and standard roughness profiles from Barton and Choubey, 1977, using the particle flow code PFC2D. The results from the numerical shear tests under constant normal load (CNL) are compared with the predicted peak shear strength using Barton’s criterion and a back-calculation of the JRC value is carried out.

Place, publisher, year, edition, pages
American Rock Mechanics Association (ARMA), 2018
Keywords
Fractals, Rock mechanics, Rocks, Shear flow, Back calculation, Fractal analysis, Fractal theory, Joint roughness coefficients, Mechanical behavior, Particle flow code, Peak shear strength, Strength criteria, Surface roughness
National Category
Geophysical Engineering
Identifiers
urn:nbn:se:kth:diva-236439 (URN)2-s2.0-85053478312 (Scopus ID)
Conference
52nd U.S. Rock Mechanics/Geomechanics Symposium, 17 June 2018 through 20 June 2018, Seattle, WA, USA
Note

QC 20181025

Available from: 2018-10-25 Created: 2018-10-25 Last updated: 2019-04-16Bibliographically approved
Johansson, F., Spross, J., Damasceno, D., Johansson, J. & Stille, H. (2018). Investigation of research needs regarding the storage of hydrogen gas in lined rock caverns: Prestudy for Work Package 2.3 in HYBRIT Research Program 1. Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Investigation of research needs regarding the storage of hydrogen gas in lined rock caverns: Prestudy for Work Package 2.3 in HYBRIT Research Program 1
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2018 (English)Report (Other academic)
Abstract [en]

The objective of HYBRIT RP1 is to explore and assess pathways to fossil-free energy-mining-iron-steel value chains and thereby provide a basis for industrial development activities and the necessary future transformative change in this field. A large-scale storage capacity for hydrogen gas is an important component of the proposed HYBRIT concept. Underground storage in lined rock caverns provides a reasonable option: a large-scale demonstration plant for storage of natural gas was constructed in Sweden in 2002 and has operated safely since then. Considering that this lined rock cavern facility was constructed for natural gas, the present report investigates the current research needs to allow for underground storage of hydrogen gas in such a facility. This will serve as a basis for the research in Work Package 2.3 of HYBRIT RP1.

Studying the experiences from decades of Swedish and international research and practice on the construction of underground gas storage facilities, the conclusion is that the lined rock cavern concept seems a reasonable way forward. In terms of rock engineering research, there are currently no critical research issues; however, a development of a previously proposed risk-based design framework for lined rock caverns may further strengthen the ability to manage risks related to underground gas storage facilities. The report identifies several potential research questions on this topic to be further studied: development of a risk-based design approach using subset simulation, the optimization potential of the concrete thickness in the lining, and the effect of spatial variation of rock mass properties on a location’s suitability for the storage facility.

Additionally, the report identifies the potential effect of hydrogen embrittlement on the steel lining as a critical research issue to ensure safe storage of hydrogen gas in lined rock caverns. However, as this issue is not related to rock engineering, but a material issue, it will not be covered further in Work Package 2.3.

Abstract [sv]

Syftet med HYBRIT RP1 är att undersöka och utvärdera möjliga vägar till att göra värdekedjorna för energi-gruva-järn-stål fossilfria och därigenom ge en grund för industriella utvecklingsarbeten och den framtida omställningen. En viktig del i HYBRIT-konceptet utgörs av behovet av lagring av stora volymer vätgas. Lagring i inklädda bergrum är ett möjligt alternativ: en storskalig demonstrationsanläggning för lagring av naturgas byggdes 2002 i södra Sverige och har använts sedan dess. Eftersom denna anläggning konstruerades för naturgas, är syftet med denna rapport att undersöka det nuvarande forskningsbehovet för att kunna lagra vätgas i en sådan typ av anläggning. Detta kommer att utgöra basen för det fortsatta arbetet inom delprojekt 2.3 i HYBRIT RP1.

Efter att ha studerat resultaten från svensk och internationell forskning, samt erfarenheterna från byggnation av inklädda bergrum för gaslagring, är slutsatsen att inklädda bergrum utgör ett rimligt alternativ för lagring av vätgas. Avseende bergmekanik finns det för närvarande inga kritiska frågeställningar. Däremot finns möjlighet att vidareutveckla riskbaserade dimensioneringsmetoder för inklädda bergrum, vilket kan stärka förmågan till god riskhantering vid byggnation av sådana anläggningar. Rapporten identifierar flera forskningsuppslag inom detta område att arbeta med inom delprojekt 2.3: utveckling av en riskbaserad dimensioneringsmetod med hjälp av subset-simulering, studie av optimeringspotentialen för betongliningens tjocklek, samt hur bergmassans rumsliga variation påverkar en plats lämplighet för anläggandet av ett inklätt bergrum.

Avseende materialfrågor finns dock en kritisk frågeställning för underjordisk vätgaslagring: vätgasförsprödning av stålliningen ses som ett möjligt problem och bör studeras vidare. Men eftersom detta inte är relaterat till bergmekanik kommer det inte att studeras vidare inom delprojekt 2.3.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018
Series
TRITA-ABE-RPT ; 182
Keywords
LRC, lined rock caverns, hydrogen gas, gas storage, LRC, inklädda bergrum, vätgas, gaslagring
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-231034 (URN)
Projects
HYBRIT
Note

QC 20180620

Available from: 2018-06-20 Created: 2018-06-20 Last updated: 2018-06-20Bibliographically 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
Spross, J., Stille, H., Johansson, F. & Palmström, A. (2018). On the Need for a Risk-Based Framework in Eurocode 7 to Facilitate Design of Underground Openings in Rock. Rock Mechanics and Rock Engineering, 51(8), 2427-2431
Open this publication in new window or tab >>On the Need for a Risk-Based Framework in Eurocode 7 to Facilitate Design of Underground Openings in Rock
2018 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, no 8, p. 2427-2431Article in journal (Refereed) Published
Abstract [en]

The European design code for geotechnical engineering, EN-1997 Eurocode 7, is currently under revision. As design of underground openings in rock fundamentally differs from design of most other types of structures, the revised Eurocode 7 must be carefully formulated to be applicable to underground openings. This paper presents the authors' view of how a design code for underground openings in rock needs to be organized to ensure that new structures are both sufficiently safe and constructed cost-effectively. The authors find that the revised version of Eurocode 7 carefully must acknowledge the fundamental decision-theoretical connection between design and risk management that should permeate all geotechnical design work. Otherwise, if the revised code is not given a risk-based framework, the authors fear that, as a consequence, the observational method will not be favorable to use in excavations of underground openings in rock. Then, cost-effective construction will be very difficult to achieve.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Eurocode 7, Risk, Design, Structural safety, Rock
National Category
Geology
Identifiers
urn:nbn:se:kth:diva-233283 (URN)10.1007/s00603-018-1463-8 (DOI)000440580300007 ()2-s2.0-85044481362 (Scopus ID)
Note

QC 20180816

Available from: 2018-08-16 Created: 2018-08-16 Last updated: 2018-08-16Bibliographically approved
Johansson, F., Westberg Wilde, M., Krounis, A., Spross, J. & Ríos Bayona, F. (2018). Some recent developments in reliability based slidingstability assessments for concrete dams. In: 26th International Congress on Large Dams, 2018: . Paper presented at 26th International Congress on Large Dams, 2018, 4 July 2018 through 6 July 2018 (pp. 1277-1294). CRC Press/Balkema
Open this publication in new window or tab >>Some recent developments in reliability based slidingstability assessments for concrete dams
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2018 (English)In: 26th International Congress on Large Dams, 2018, CRC Press/Balkema , 2018, p. 1277-1294Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a reliability based framework for the assessment of sliding stability for concrete dams was presented. The framework consists of several parts based on the Probabilistic model code for concrete dams developed by Westberg-Wilde and Johansson and includes guidelines on how reliability based sliding stability assessment should be performed, together with recent work by Krounis et al. how to account for partially bonded interfaces. In the proposed framework, the assessments start with performing preliminary calculations using a priori assumptions on parameters included in the analysis. If cost-benefit analyses show that further analyses could be beneficial, investigations are undertaken on relevant parameters in the failure modes. The results from the investigations are used to update the calculations in the assessment and decisions on stability enhancing measures are undertaken if necessary. In the presented example the preliminary sliding stability analysis of the interface, before testing was performed, showed a reliability index of 4.91, indicating an unacceptable failure probability of the dam without any testing. Taking into account the information obtained from testing the basic friction angle of the interface increased the reliability index from 4.91 to 7.24, clearly showing the gain of including test results in the assessment. When the influence of cohesion was accounted for a reliability index of 6.49 was obtained, which shows that cohesion can give a potential gain to the stability, even though it in this case still is lower than the gain from updating the basic friction angle. When both limit states of the interface were considered as a system the reliability index increased to 8.1.

Place, publisher, year, edition, pages
CRC Press/Balkema, 2018
Keywords
Concrete dams, Concretes, Cost benefit analysis, Friction, Interface states, System stability, Failure Probability, Partially bonded interfaces, Presented examples, Probabilistic modeling, Reliability Index, Reliability-based, Sliding stability, Sliding stability analysis, Reliability analysis
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-247231 (URN)2-s2.0-85061499340 (Scopus ID)9781138612280 (ISBN)
Conference
26th International Congress on Large Dams, 2018, 4 July 2018 through 6 July 2018
Note

QC 20190402

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8152-6092

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