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  • 1.
    Hellgren, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Fransson, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Luleå, Sweden.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Westberg Wilde, Marie
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Measurement of ice pressure on a concrete dam with a prototype ice load panel2020In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 170, article id 102923Article in journal (Refereed)
    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.

  • 2.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A discrete element material model including particle degradation suitable for rockfill embankments2019In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 115, article id 103166Article in journal (Refereed)
    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.

  • 3.
    Stigsson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. SKB, Swedish Nuclear Fuel and Waste Management Co, Solna, Sweden.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A Novel Conceptual Approach to Objectively Determine JRC Using Fractal Dimension and Asperity Distribution of Mapped Fracture Traces2019In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, no 4, p. 1041-1054Article in journal (Refereed)
    Abstract [en]

    The understanding of fractures in hard rock is important for topics such as geomechanics, rock mechanics and groundwater flow and solute transport. One key aspect is the roughness of the fracture, often described as the joint roughness coefficient, JRC. JRC is often subjectively interpreted by one geologist comparing a fracture trace with different type traces. It has been shown that several geologists are needed to get reliable interpretations of JRC. There are numerous attempts in the literature to develop objective methods to estimate JRC from digital traces. Some methods are not applicable to fractures, which give arbitrary results while other methods are sensitive to the resolution of the digitalisation and hence need a new relationship for each resolution. Another way of describing the roughness is by the two parameters fractal dimension and magnitude distribution of the asperities. These parameters can be objectively inferred using algorithms and act as input for a model to estimate JRC. Using several evaluation methods, the uncertainty can be decreased and, hence, more robust results achieved. A multilinear model is developed, JRC = − 4.3 + 54.6σδh(1mm) + 4.3H, that estimates JRC, of the classic ten type curves by Barton and Choubey, with standard deviation ± 1 unit. Despite the simplicity of the model it explains 96.5% of the variance in JRC. The developed model is benchmarked against an ensemble of geologists, using nine synthetic fracture traces. The median difference of JRC is 0.2 units and the model shows 40% smaller spread compared to the geologists.

  • 4.
    Ghaderi, Abdolvahed
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Abbaszadeh Shahri, Abbas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Islamic Azad Univ, Roudehen Branch, Fac Civil Engn, Tehran, Iran..
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    An artificial neural network based model to predict spatial soil type distribution using piezocone penetration test data (CPTu)2019In: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 78, no 6, p. 4579-4588Article in journal (Refereed)
    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.

  • 5.
    Prästings, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Characteristic values of geotechnical parameters in Eurocode 72019In: 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)
    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.

  • 6.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Landslide susceptibility hazard map in southwest Sweden using artificial neural network2019In: Catena (Cremlingen. Print), ISSN 0341-8162, E-ISSN 1872-6887, Vol. 183, article id UNSP 104225Article in journal (Refereed)
    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.

  • 7.
    Massarsch, K. R.
    et al.
    Geo Risk & Vibrat Scandinavia AB, Stockholm, Sweden..
    Wersäll, Carl
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Monitoring and Process Control of Vibratory Driving2019In: Geotechnical Engineering, ISSN 0046-5828, Vol. 50, no 3, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Vibrators are used increasingly in the foundation industry, primarily for installation of piles and sheet piles, but also for deep vibratory compaction. Fundamentals of vibratory driving are described that make it possible to choose vibrator performance parameters based on field monitoring and performance control. Variable frequency and amplitude vibrators have become available that make it possible to adapt the driving process to project-specific requirements. The components of modern electronic measuring systems are detailed that can be used to monitor, control, and document different aspects of vibratory driving. Two examples are presented-vibratory driving of sheet piles and resonance compaction-which show how the performance of vibrators and sheet piles can be analysed and adapted to meet specific requirements. By using the advanced monitoring and process control systems, the efficiency of vibratory driving is enhanced. From the retrieved parameters, a better understanding of the vibratory driving process is gained, which can be used to develop a valuable database.

  • 8.
    Bjurström, Henrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Non-contact rolling surface wave measurements on asphalt concrete2019In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 20, no 2, p. 334-346Article in journal (Refereed)
    Abstract [en]

    Rolling surface wave measurements on a single, thin asphalt concrete (AC) layer are presented to investigate their use in rapid nondestructive field tests. An array of 47 micro-electro-mechanical sensor (MEMS) microphones is mounted on a trailer together with an automated impact source. Multichannel recordings from single impacts are obtained at 80 equally spaced array positions as the trailer moves at a constant speed. The complete battery-powered data acquisition system enables large-scale testing of newly built pavements. Multiple sets of test results show good repeatability for the assessed shear wave velocity and demonstrate the strong temperature dependency of AC. The presented results indicate a possible application for quality assurance of AC using rolling surface wave measurements.

  • 9.
    Hov, Sölve
    et al.
    GeoMind/LabMind.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Persson, Erik
    Bjerking.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On empirical correlations for normalised shear strengths from fall cone and direct simple shear tests in soft Swedish clays2019In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed)
  • 10.
    Bjureland, William
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sjölander, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Probability distributions of shotcrete parameters for reliability-based analyses of rock tunnel support2019In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 87, p. 15-26Article in journal (Refereed)
    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.

  • 11.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Gasch, Tobias
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Reliability-based alarm thresholds for structures analysed with the finite element method2019In: Structural Safety, ISSN 0167-4730, E-ISSN 1879-3355, Vol. 76, p. 174-183Article in journal (Refereed)
    Abstract [en]

    Civil engineering structures are commonly monitored to assess their structural behaviour, using alarm thresholds to indicate when contingency actions are needed to improve safety. However, there is a need for guidelines on how to establish thresholds that ensure sufficient safety. This paper therefore proposes a general computational algorithm for establishment of reliability-based alarm thresholds for civil engineering structures. The algorithm is based on Subset simulation with independent-component Markov chain Monte Carlo simulation and applicable with both analytical structural models and finite element models. The reliability-based alarm thresholds can straightforwardly be used in the monitoring plans that are developed in the design phase of a construction project, in particular for sequentially loaded structures such as staged construction of embankments. With the reliability-based alarm thresholds, contingency actions will only be implemented when they are needed to satisfy the target probability of failure.

  • 12.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB, Sweden.
    Rheology of Cement Grouts: On the Critical Shear Rate and No-Slip Regime in the Couette Geometry2019In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948Article in journal (Refereed)
    Abstract [en]

    The rheological properties of cement grouts play a key role in determining the final spread in grouted rock formations. In terms of flow properties, cement grouts are known to be complex thixotropic fluids, but their steady flow behavior is often described by the simple Bingham constitutive law. Due to their time dependent nature, the flow curves of cement grouts have been known to exhibit an unstable non-monotonic region, characterized by a negative slope below a critical shear rate. Within this paper, we focus on how this unstable region that is dominated by flow localization is affected by rheometer geometry and flow sweep measurement interval. We carried out controlled shear rate (CSR) flow sweeps on typical micro-cement grouts within different Couette geometries. Lastly, we discuss the effects of geometry and measurement interval on the resulting flow curves, with a focus on the critical shear rate that separates homogenous from non-homogeneous unstable flow.

  • 13.
    Ignat, Razvan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Baker, S.
    Skanska Sweden AB, Stockholm, Sweden.
    Holmén, M.
    Swedish Geotechnical Institute (SGI), Linköping, Sweden.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Triaxial extension and tension tests on lime-cement-improved clay2019In: Soil and foundation, ISSN 0038-0806Article in journal (Refereed)
    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.

  • 14.
    Wonglert, Anucha
    et al.
    King Mongkuts Univ Technol Thonburi, Dept Civil Engn, Bangkok, Thailand..
    Jongpradist, Pornkasem
    King Mongkuts Univ Technol Thonburi, Dept Civil Engn, Bangkok, Thailand..
    Jamsawang, Pitthaya
    King Mongkuts Univ Technol North Bangkok, Dept Civil Engn, Bangkok, Thailand..
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bearing capacity and failure behaviors of floating stiffened deep cement mixing columns under axial load2018In: Soil and foundation, ISSN 0038-0806, Vol. 58, no 2, p. 446-461Article in journal (Refereed)
    Abstract [en]

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

  • 15.
    Davy, P.
    et al.
    Univ Rennes, CNRS, Geosci Rennes, UMR 6118, Rennes, France..
    Darcel, C.
    Itasca Consultants SAS, Ecully, France..
    Le Goc, R.
    Itasca Consultants SAS, Ecully, France..
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Swedish Nucl Fuel & Waste Management Co, SKB, Solna, Sweden.
    Elastic Properties of Fractured Rock Masses With Frictional Properties and Power Law Fracture Size Distributions2018In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 123, no 8, p. 6521-6539Article in journal (Refereed)
    Abstract [en]

    We derive the relationships that link the general elastic properties of rock masses to the geometrical properties of fracture networks, with a special emphasis to the case of frictional crack surfaces. We extend the well-known elastic solutions for free-slipping cracks to fractures whose plane resistance is defined by an elastic fracture (shear) stiffness k(s) and a stick-slip Coulomb threshold. A complete set of analytical solutions have been derived for (i) the shear displacement in the fracture plane for stresses below the slip threshold and above, (ii) the partitioning between the resistances of the fracture plane on the one hand and of the elastic matrix on the other hand, and (iii) the stress conditions to trigger slip. All the expressions have been checked with numerical simulations. The Young's modulus and Poisson's ratio were also derived for a population of fractures. They are controlled both by the total fracture surface for fractures larger than the stiffness length l(S) (defined by k(s) and the intact matrix elastic properties) and by the percolation parameter of smaller fractures. These results were applied to power law fracture size distributions, which are likely relevant to geological cases. We show that if the fracture size exponent is in the range -3 to -4, which corresponds to a wide range of geological fracture networks, the elastic properties of the bulk rock are almost exclusively controlled by k(s) and the stiffness length, meaning that the fractures of size l(S) play a major role in the definition of the elastic properties.

  • 16.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Palmström, Arild
    RockMass Consulting Co, Ovre Smestad Vei 35E, N-0378 Oslo, Norway..
    On the Need for a Risk-Based Framework in Eurocode 7 to Facilitate Design of Underground Openings in Rock2018In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, no 8, p. 2427-2431Article in journal (Refereed)
    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.

  • 17.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, I.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Resonant roller compaction of gravel in full-scale tests2018In: Transportation Geotechnics, ISSN 2214-3912, Vol. 14, p. 93-97Article in journal (Refereed)
    Abstract [en]

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

  • 18.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Olsson, Lars
    Geostatistik AB, Tumba, Sweden..
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    The Swedish Geotechnical Society's methodology for risk management: a tool for engineers in their everyday work2018In: Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, ISSN 1749-9518, E-ISSN 1749-9526, Vol. 12, no 3, p. 183-189Article in journal (Refereed)
    Abstract [en]

    The Swedish Geotechnical Society has adopted a general methodology for risk management in geotechnical engineering projects to reduce the costs related to negative outcomes of geotechnical risks. This technical note highlights the main features of the methodology and strives to inspire the international geotechnical community to apply sensible risk management methods. In the authors' opinion, a successful geotechnical risk management needs to be structured, be tailored to the project, and permeate the engineers' everyday work. Then, sufficient quality can be achieved in the project with larger probability.

  • 19.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Two-phase cement grout propagation in homogeneous water-saturated rock fractures2018In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 106, p. 243-249Article in journal (Refereed)
    Abstract [en]

    Modeling of cement grout flow in rock fractures is important for the design, monitoring and execution of rock grouting that is widely used in a variety of rock engineering applications. This study presents a mathematical model based on the Reynolds flow equation for cement grout flow in a homogeneous water-saturated rock fracture. The model is based on two-phase flow, i.e. grout as a Bingham fluid and groundwater as a Newtonian fluid, and is used for investigating the importance of the water phase in rock grouting. The modeling results for the two-phase flow generally show the importance of the water phase that can significantly affect the pressure distribution and grout penetration in the fracture, especially under the condition of grout hardening. Such effects depend on the viscosity ratio between the grout and groundwater, which becomes increasingly important for cases with smaller values of the viscosity ratio. The grout density also affects the grout penetration length. Applying an analytical solution based on single-phase flow, i.e. neglecting the impact of groundwater flow, for modeling grout injection, will generally overestimate the penetration length.

  • 20.
    Bjureland, William
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Challenges in applying fixed partial factors to rock engineering design2017In: Geotechnical Special Publication, ISSN 0895-0563, no 283, p. 384-393Article in journal (Refereed)
    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.

  • 21.
    El Tani, Mohamed
    et al.
    AABuildings, Beirut, Lebanon.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Grout Spread and Injection Period of Silica Solution and Cement Mix in Rock Fractures2017In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, p. 1-16Article in journal (Refereed)
    Abstract [en]

    A systematic presentation of the analytic relations of grout spread to the time period is established. They are divided following the nature of the flow, the property of the mix and the driving process. This includes channel flow between parallel plates and radial flow between parallel discs, nonlinear Newtonian fluids like silica solution, polyurethane and epoxy, and Bingham material like cement-based grout, and three grouting processes at a constant flow rate, constant pressure and constant energy. The analytic relations for the constant energy process are new and complete the relations of the constant flow rate and constant pressure processes. The well-known statement that refusal cannot be obtained during finite time for any injected material at a constant flow rate or constant injection pressure is extended to include the energy process. The term refusal pressure or energy cannot be supported for stop criteria. Stop criteria have to be defined considering confirmed relation of the spread to the time period and of the flow rate to the pressure and spread. It is shown that it is always possible to select a grouting process along which the work will exceed any predefined energy, the consequence of which is that jacking is related to the applied forces and not to the injected energy. Furthermore, a clarification is undertaken concerning the radial flow rate of a Bingham material since there are two different formulations. Their difference is explained and quantified. Finally, it is shown that the applied Lugeon theory is not supported by the analytic relations and needs to be substantially modified.

  • 22.
    Prästings, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Müller, Rasmus
    Tyréns AB.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Bjureland, William
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Implementing the Extended Multivariate Approach in Design with Partial Factors for a Retaining Wall in Clay2017In: ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering, ISSN 2376-7642, Vol. 3, no 4, article id 04017015Article in journal (Refereed)
    Abstract [en]

    Limitations with the current design using partial factors in Eurocode 7 have been identified. Uncertainties in the material properties are incorporated in both the cautious estimate of the characteristic value and the partial factor. Furthermore, the partial factor is fixed, which limits the opportunities to update the design when additional information is available. A more rational procedure of managing uncertainties in design with partial factors is proposed based on the Bayesian methodology referred to as the extended multivariate approach. The benefits of the approach are illustrated with a case study in which uncertainties of undrained shear strength are characterized for a Swedish clay. The characteristic value and design value is calculated in accordance with the Swedish national annex to Eurocode 7 by adjusting the otherwise fixed partial factor with a conversion factor allowable through EN 1990. The study highlights major benefits in managing uncertainties in a quantifiable and rational way.

  • 23.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Halilovic, Armin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Numerical, Experimental and Analytical Studies on Fluid Flow through a Marsh Funnel2017In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, no 6, p. 1501-1507Article in journal (Refereed)
    Abstract [en]

    This paper presents the application of computational fluid dynamics technique in civil and underground industries to evaluate fluid behaviour in a Marsh funnel. The numerical approach, based on computational fluid dynamics, simulated an incompressible two-phase Newtonian flow by means of the Volume-of-Fluid method. A complementary analytical proposed which provided a quick, field-ready method to assess the fluid field in the Marsh funnel. A supplemental experimental effort evaluated the results obtained from both the analytical calculation and numerical simulation. Results showed that the application of computational fluid dynamics technique gives the desired results in studying fluid flows in civil and underground industries. Proposed analytical solution is also capable of accurately predicting the fluid flow and thus can complement the experimental and numerical approaches. Further, the proposed analytical approach can be an alternative method for faster evaluation of fluid, although it needs to be calibrated with either the numerical or the experimental studies.

  • 24.
    Bjureland, William
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Reliability aspects of rock tunnel design with the observational method2017In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 98, p. 102-110Article in journal (Refereed)
    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.

  • 25.
    Deckner, Fanny
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Jörgen
    Norwegian Geotechnical Institute.
    Viking, Kenneth
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Trafikverket.
    Hintze, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Sheet pile behavior during vibratory driving: numerical study based on a field test2017In: Soil Dynamics and Earthquake Engineering, ISSN 0267-7261, E-ISSN 1879-341XArticle in journal (Refereed)
    Abstract [en]

    Vibrations due to sheet pile driving are a problem in many urban areas today. Increased knowledgeof the vibration transfer process from source to nearby objects is important in order to enableminimization of induced vibrations. The transfer of vibrations from sheet pile to soil is dependent onthe sheet pile behaviour during driving. This paper presents a 3D finite element study of thebehaviour of a vibratory driven sheet pile, complementing results from a full-scale field test. Thefinite element model accounts for strain dependent soil stiffness using an equivalent linear soilmodel. The conclusion is that the sheet pile bends considerably during driving with eccentricclamping. Furthermore, it is shown that the bending mode is similar irrespective of sheet pilepenetration depth.

  • 26.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ali Akbar, Saman
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Al-Naddaf, Manar
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Uncertainties in Grout Penetrability Measurements; Evaluation and Comparison of Filter pump, Penetrability meter and Short slot2017In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed)
    Abstract [en]

    To measure grout penetrability in fractured hard rock, various measuring instruments have been developed over the years. Penetrability meter and Filter pump have been designed to use in both the lab and the field. Short slot has been applicable mainly in the lab due to its complexity. The fact, that these instruments have been built based on different assumptions, limitations, and test conditions, makes their results occasionally in contradict. Deficiency in design of the instruments as well as the methods of evaluating grout penetrability is additionally a basis for uncertainty in results. This study is an experimental effort to determine and thoroughly perceive the nature of the most governing uncertainties in grout penetrability measurements. The test apparatus, procedure, and method used to evaluate the grout penetrability in both Penetrability meter and Filter pump were thus modified. The aim was to control the corresponding uncertainties and make their limitations and test conditions as similar as possible with the ones in Short slot. The results suggested that to obtain a more realistic evaluation of the grout penetrability, measurement should be accomplished at both the high and the low pressures with sufficient grout volume using Short slot. Moreover, application of both Filter pump and Penetrability meter is no longer recommended due to the revealed uncertainties.

  • 27.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Lawrence Berkeley National Laboratory.
    Magakis, Konstantinos
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Varying aperture long slot (VALS), a method for studying grout penetrability into fractured hard rock2017In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 40, no 5, p. 871-882Article in journal (Refereed)
    Abstract [en]

    This paper presents the design, manufacturing, and assembly of a new laboratory apparatus for investigation of grout filtration tendency and penetrability into rock fractures. The method makes it possible to examine grout samples composed of a wide range of cements and additives/ admixtures with different water-to-solid ratios. The apparatus can be used to investigate the influence of different parameters on grout penetrability. Examples of these parameters include the cement particle size/distribution curves/chemical compositions, and the type and ratio of additives/admixtures that provide a variety of setting/hardening times, and rheological and strength properties. The grouting operation into the rock fractures is replicated using an artificial slot with 4-m-long constrictions varying from 230 to 10 μm, and selective inlet and outlet. The apparatus can also accommodate grouting experiments under both static and dynamic pressure conditions up to 1, 500 kPa to study their influence. Illustrative results are also provided.

  • 28.
    Deckner, Fanny
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Viking, Kenneth
    Trafikverket.
    Hintze, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Wave patterns in the ground: case studies related to vibratory sheet pile driving2017In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529Article in journal (Refereed)
    Abstract [en]

    Vibrations due to pile and sheet pile driving are known to cause discomfort for people, aswell as damage to nearby buildings and structures. To enable prediction of ground vibration levels itis important to acknowledge the wave patterns induced in the ground to correctly determine whichattenuation model to adopt. This paper presents wave patterns in the ground due to vibratory sheetpile driving based on field measurements from three case studies. The results show different wavepatterns in the ground. At the ground surface the wave patterns are elliptical, resembling Rayleighwaves. At depth in the soil the wave patterns are instead strongly polarized in different directions,indicating the presence of P- and S-waves. Moreover, wave patterns tend to become more irregularwith increasing distance from the source. This paper contributes to an improved understanding ofwave patterns in the ground during vibratory sheet pile driving, forming a platform for thedevelopment of a reliable prediction model.

  • 29.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    When is the observational method in geotechnical engineering favourable?2017In: Structural Safety, ISSN 0167-4730, E-ISSN 1879-3355, Vol. 66, p. 17-26Article in journal (Refereed)
    Abstract [en]

    The observational method in geotechnical engineering is an acceptable verification method for limit states in Eurocode 7, but the method is rarely used despite its potential savings. Some reasons may be its unclear safety definition and the lack of guidelines on how to establish whether the observational method is more favourable than conventional design. In this paper, we challenge these issues by introducing a reliability con­straint on the observational method and propose a probabilistic optimi­sation methodology that aids the decision-making engineer in choosing between the observational method and conventional design. The method­ology suggests an optimal design after comparing the expected utilities of the considered design options. The methodology is illustrated with a practical example, in which a geotechnical engineer evaluates whether the observational method may be favourable in the design of a rock pillar. We conclude that the methodology may prove to be a valuable tool for deci­sion-making engineers’ everyday work with managing risks in geotech­nical projects.

  • 30.
    Nejad Ghafar, Ali
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Mentesidis, Anastasios
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    An Experimental Approach to the Development of Dynamic Pressure to Improve Grout Spread2016In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, no 9, p. 3709-3721Article in journal (Refereed)
    Abstract [en]

    Dynamic grouting is one of the methods to improve grout spread in rock that have been investigated since 1985. The results were promising, but all tests were performed under noticeable simplifications related to conditions in rock fractures. This study is an experimental approach to improve the grout spread using low-frequency instantaneous variable pressure as a new alternative with better control of filtration. The method is tested through parallel plates with constrictions of 30 and 43 µm under the applied pressures with 4 s/8 s and 2 s/2 s peak/rest periods. The results reveal conclusively the effectiveness of the method and provide a basis for further development of dynamic grouting.

  • 31.
    Shahri, Abbas Abbaszadeh
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Islamic Azad Univ.
    Assessment and Prediction of Liquefaction Potential Using Different Artificial Neural Network Models: A Case Study2016In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529, Vol. 34, no 3, p. 807-815Article in journal (Refereed)
    Abstract [en]

    Soil liquefaction as a transformation of granular material from solid to liquid state is a type of ground failure commonly associated with moderate to large earthquakes and refers to the loss of strength in saturated, cohesionless soils due to the build-up of pore water pressures and reduction of the effective stress during dynamic loading. In this paper, assessment and prediction of liquefaction potential of soils subjected to earthquake using two different artificial neural network models based on mechanical and geotechnical related parameters (model A) and earthquake related parameters (model B) have been proposed. In model A the depth, unit weight, SPT-N value, shear wave velocity, soil type and fine contents and in model B the depth, stress reduction factor, cyclic stress ratio, cyclic resistance ratio, pore pressure, total and effective vertical stress were considered as network inputs. Among the numerous tested models, the 6-4-4-2-1 structure correspond to model A and 7-5-4-6-1 for model B due to minimum network root mean square errors were selected as optimized network architecture models in this study. The performance of the network models were controlled approved and evaluated using several statistical criteria, regression analysis as well as detailed comparison with known accepted procedures. The results represented that the model A satisfied almost all the employed criteria and showed better performance than model B. The sensitivity analysis in this study showed that depth, shear wave velocity and SPT-N value for model A and cyclic resistance ratio, cyclic stress ratio and effective vertical stress for model B are the three most effective parameters on liquefaction potential analysis. Moreover, the calculated absolute error for model A represented better performance than model B. The reasonable agreement of network output in comparison with the results from previously accepted methods indicate satisfactory network performance for prediction of liquefaction potential analysis.

  • 32.
    Ignat, Razvan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Baker, Sadek
    Skanska Sverige AB.
    Liedberg, Sven
    Skanska Sverige AB.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Behavior of braced excavation supported by panels of deep mixing columns2016In: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 53, no 10, p. 1671-1687Article in journal (Refereed)
    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.

  • 33.
    Lingwanda, Mwajuma
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nyaoro, Dalmas L.
    Comparison of geotechnical uncertainties linked to different soil characterization methods2016In: Geomechanics and Geoengineering, ISSN 1748-6025, E-ISSN 1748-6033, p. 1-15Article in journal (Refereed)
    Abstract [en]

    One of the essential inputs in settlement prediction models is the soil modulus, which may be obtained from laboratory tests or estimated from in situ measurements. The total uncertainty in predicting the confined modulus of a sandy soil is quantified with data from side-by-side in situ testing using the standard penetration test, the static cone penetration test, the light dynamic probing and the laboratory oedometer test. To estimate transformation errors, correlations are proposed between in situ and laboratory data. The results indicate that similar magnitudes of total uncertainties are associated with the in situ methods, which are approximately twice as high as those from the direct oedometer method. The quantified uncertainties are an important input for reliability-based designs of foundations under similar soil conditions.

  • 34.
    Bjurström, Henrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Detecting the thickness mode frequency in a concrete plate using backward wave propagation2016In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 139, no 2, p. 649-657Article in journal (Refereed)
    Abstract [en]

    Material stiffness and plate thickness are the two key parameters when performing quality assurance/quality control on pavement structures. In order to estimate the plate thickness non-destructively, theImpact Echo (IE) method can be utilized to extract the thickness resonance frequency. An alternativeto IE for estimating the thickness resonance frequency of a concrete plate, and to subsequently enablethickness determination, is presented in this paper. The thickness resonance is often revealed as asharp peak in the frequency spectrum when contact receivers are used in seismic testing. Due to a lowsignal-to-noise ratio, IE is not ideal when using non-contact microphone receivers. In studying thecomplex Lamb wave dispersion curves at a frequency infinitesimally higher than the thickness frequency,it is seen that two counter-directed waves occur at the same frequency but with phase velocitiesin opposite directions. Results show that it is possible to detect the wave traveling with anegative phase velocity using both accelerometers and air-coupled microphones as receivers. Thisalternative technique can possibly be used in non-contact scanning measurements based on aircoupled microphones.

  • 35.
    Dinegdae, Yared H.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Birgisson, Björn
    Aston University, UK.
    Effects of truck traffic on top-down fatigue cracking performance of flexible pavements using a new mechanics-based analysis framework2016In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    The mechanics-based analysis framework predicts top-down fatigue cracking initiation timein asphalt concrete pavements by utilising fracture mechanics and mixture morphology-basedproperty. To reduce the level of complexity involved, traffic data were characterised and incorporatedinto the framework using the equivalent single axle load (ESAL) approach. There isa concern that this kind of simplistic traffic characterisation might result in erroneous performancepredictions and pavement structural designs. This paper integrates axle load spectraand other traffic characterisation parameters into the mechanics-based analysis framework andstudies the impact these traffic characterisation parameters have on predicted fatigue crackingperformance. The traffic characterisation inputs studied are traffic growth rate, axle load spectra,lateral wheel wander and volume adjustment factors. For this purpose, a traffic integrationapproach which incorporates Monte Carlo simulation and representative traffic characterisationinputs was developed. The significance of these traffic characterisation parameters wasestablished by evaluating a number of field pavement sections. It is evident from the resultsthat all the traffic characterisation parameters except truck wheel wander have been observedto have significant influence on predicted top-down fatigue cracking performance.

  • 36.
    Bjurström, Henrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Gudmarsson, Anders
    Ryden, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Starkhammar, Josefin
    Field and laboratory stress-wave measurements of asphalt concrete2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 126, p. 508-516Article in journal (Refereed)
    Abstract [en]

    Abstract Non-contact surface wave measurements are performed on a new asphalt concrete (AC) pavement using 48 micro-electro-mechanical system (MEMS) sensors as receivers to estimate the real part of the dynamic moduli of the AC top layer. Laboratory measurements of core samples, extracted from the field measurement positions, are used to construct master curves for comparison with the field measurements. The real parts of the dynamic moduli from the two test methods are consistent at the field measurement temperatures, and the non-contact field measurements are highly repeatable. These results indicate a possible application for quality assurance of AC based on mechanical properties.

  • 37.
    Draganović, Almir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lagerblad, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Filtration of silica particles from a low-pH cementitious grout2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 105, p. 29-34Article in journal (Refereed)
    Abstract [en]

    Spent nuclear fuel is stored in rock depositories. Swelled bentonite around the stored capsules prevents eventual spread of radioactive material by ground water. The pH-value of the ground water in contact with bentonite shall be less than 11 not to affect the swelling capacity of the bentonite. Therefore cementitious grout with low pH-value is used to grout these depositories. There is a risk that pH-value of this grout can locally increase due to filtration at fracture constriction and influence pH-value of ground water. Chemical SEM EDAX-analysis indicates that there is no risk of increasing of PH-value in this grout.

  • 38.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory. School of Engineering and Applied Science, Aston University, Birmingham, UK.
    Force transmission and soil fabric of binary granular mixtures2016In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656, Vol. 66, no 7, p. 578-583Article in journal (Refereed)
    Abstract [en]

    The effect of fines content on force transmission and fabric development of gap-graded mixtures under triaxial compression has been studied using the discrete-element method. Results were used to define load-bearing soil fabrics where the relative contributions of coarse and fine components are explicitly quantified in terms of force transmission. Comparison with previous findings suggests that lower particle size ratios result in higher interaction between components. A potential for instability was detected for underfilled fabrics in agreement with recent findings. It was also found that the threshold fines content provides an accurate macroscopic estimation of the transition between underfilled and overfilled fabrics.

  • 39.
    Krounis, Alexandra
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Influence of cohesive strength in probabilstic sliding stability re-assessment of concrete dams2016In: Journal of Geotechnical and Geoenvironmental Engineering, ISSN 1090-0241, E-ISSN 1943-5606, Vol. 143, no 2, article id 04016094Article in journal (Refereed)
    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.

  • 40.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Influence of scale and matedness on the peak shear strength of fresh, unweathered rock joints2016In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 82, p. 36-47Article in journal (Refereed)
    Abstract [en]

    It is widely recognized that the mechanical parameters for unfilled and rough rock joints, such as the peak shear strength, can vary with scale. However, due to contradictory results concerning the extent and nature of the scale effect reported in the literature, it is still a debated subject. A conceptual model developed by Johansson and Stille 2014 suggests how roughness and matedness at different scales influences the peak shear strength for fresh, rough and unweathered joint. However, the model's ability to predict how the roughness and matedness affects the peak shear strength at different scales was not verified. The aim of this paper is to investigate the ability of the conceptual model to estimate the peak shear strength at different degrees of matedness and scales. A series of direct shear test were carried out at two different scales and two different degrees of matedness. The peak shear strength from the tests was compared to the peak shear strength calculated with the conceptual model. The results showed that the model can predict the peak shear strength for both the perfectly mated and the unmated joints. No scale effect was observed in the shear tests, which is in line with the predictions using the model. The influence of matedness in combination with scale might explain some of the contradictory findings regarding the scale effect.

  • 41.
    Palmén, Anders
    et al.
    PEAB Civil Engineering.
    Axelson, Morgan
    Swedish Transport Administration.
    Price, Graham
    Lithic Australia Pty Ltd.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Low-temperature calcite precipitation in sand using CIPS2016In: Ground Improvement, ISSN 1365-781X, E-ISSN 1751-7621, Vol. 169, no 1, p. 36-41Article in journal (Refereed)
    Abstract [en]

    The permeation grouting system CIPS (calcite in situ precipitation system) stabilises granular soil by hydrolysing the urea and causing calcite crystals to precipitate at the contact points of the grains. At low temperatures, the activity of urea hydrolysis is slow, causing concern that the CIPS system might not build sufficient strength in order to be an efficient soil stabilisation method. Most of the documented experience and research have been conducted in Australia; in order to examine the suitability of CIPS under Scandinavian climate conditions, where the operating temperature for the method needs to be adjusted to around 10°C, a laboratory study was conducted. The test cores were all treated and stabilised in a temperature-controlled room simulating Scandinavian ground conditions. After different lengths of curing time, some of the cemented samples were tested saturated for unconfined compressive strength (UCS); the other samples were allowed to dry at either 10 or 20°C before they were tested for UCS. The tests showed a rather obvious increase in strength especially after allowing the spent fluid to deplete, causing the samples to dry out; only a slight difference in UCS increase was recorded between the drying temperature of 10 and 20°C.

  • 42.
    Prästings, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Müller, Rasmus
    Tyréns AB.
    Multivariate approach in reliability-based design of a sheet pile wall2016In: Transportation Geotechnics, ISSN 2214-3912, Vol. 7, p. 1-12Article in journal (Refereed)
    Abstract [en]

    In light of a restricted budget, there is a need to stress on the potential savings in conducting qualitative geotechnical investigations. This paper presents a case study on how site investigation efforts can be linked to potential savings in designing a sheet pile wall in central Sweden. The uncertainty in the undrained shear strength is a measure of investigation effort and have been evaluated from multivariate information, several investigation methods. A multivariate analysis (MVA) procedure based on Bayesian statistics was used to cross-validate information obtained by different investigation methods, thus allowing the uncertainty or effort to be updated (reduced) when additional investigations are included in the analysis. The uncertainty was evaluated for two sets of investigations, one of which included additional measurements and hence less uncertainty. A reliability-based design method, FOSM, was then used to study how the additional investigations affected the evaluated uncertainty and one design constraint of the sheet pile wall, namely the depth of penetration. The results show that the depth of penetration can potentially be reduced by approximately 11% of the total wall area.

  • 43.
    Müller, Rasmus
    et al.
    Tyréns AB.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Multivariate stability assessment during staged construction2016In: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 53, no 4, p. 603-618Article in journal (Refereed)
    Abstract [en]

    For staging the construction of embankments on soft clay, an important aspect in deterministic or probabilistic stability analyses is the assessment of the representative average values and associated uncertainties for the undrained shear strength as the height of the embankment is sequentially increased. Assessments made prior to construction can be verified by performing observations during the construction phase. All relevant available information should be incorporated into an analysis to increase the level of confidence and the objectivity of the assessment. To this end, we apply an extended multivariate approach to assess the undrained shear strength using different indirect measurement methods during the staged construction of the Veda embankment (Sweden). This multivariate approach implies that uncertainties associated with the assessments are reduced, and objectively weighted averages are obtained. The resulting implications on the calculated deterministic safety factors and the probabilistically retrieved reliability indices of the embankment are thoroughly discussed in this work.

  • 44. Place, Joachim
    et al.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Malehmir, Alireza
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On using the thin fluid-layer approach at ultrasonic frequencies for characterising grout propagation in an artificial fracture2016In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 89, p. 68-74Article in journal (Refereed)
    Abstract [en]

    We investigate the ultrasonic transport properties of such an idealised fracture whose 100 µm aperture is about 0.02 the wavelength, and filled with various fluids flowing under external forcing. As the artificial fracture is made of two solid and parallel walls separated by a thin fluid layer, we use the thin fluid layer concept to study the compressional (P-) wavefield transmitted across and reflected off the fracture, with no mode-conversion considered. We demonstrate that air and various fluids (water, grouts of varied w/c – water to cement ratio) can be distinguished when injected into the fracture, both at atmospheric pressure or under over-pressure as done in real grouting cases in the field. Then, using an analytical solution, we verify our experimental data and predict the results that can be obtained with a different fracture aperture. Our results illustrate that replicating such ultrasonic measurements both in space and time would allow successfully monitoring the grout propagation within an artificial fracture.

  • 45. Esmaeilabadi, Reza
    et al.
    Shahri, Abbas Abbaszadeh
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Islamic Azad Univ.
    PREDICTION OF SITE RESPONSE SPECTRUM UNDER EARTHQUAKE VIBRATION USING AN OPTIMIZED DEVELOPED ARTIFICIAL NEURAL NETWORK MODEL2016In: ADVANCES IN SCIENCE AND TECHNOLOGY-RESEARCH JOURNAL, ISSN 2299-8624, Vol. 10, no 30, p. 76-83Article in journal (Refereed)
    Abstract [en]

    Site response spectrum is one of the key factors to determine the maximum acceleration and displacement, as well as structure behavior analysis during earthquake vibrations. The main objective of this paper is to develop an optimized model based on artificial neural network (ANN) using five different training algorithms to predict nonlinear site response spectrum subjected to Silakhor earthquake vibrations is. The model output was tested for a specified area in west of Iran. The performance and quality of optimized model under all training algorithms have been examined by various statistical, analytical and graph analyses criteria as well as a comparison with numerical methods. The observed adaptabilities in results indicate a feasible and satisfactory engineering alternative method for predicting the analysis of nonlinear site response.

  • 46.
    Dinegdae, Yared Hailegiorgis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Reliability-based calibration for a mechanics-based fatigue cracking design procedure2016In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 17, no 3, p. 529-546Article in journal (Other academic)
    Abstract [en]

    This paper presents a new reliability-based code calibration in load resistance factor design (LRFD) format for the mechanics-based fatigue cracking analysis framework. The pavement design procedure incorporates an appropriate failure criterion and design period. Moreover, it provides uniform performance at the desired level of reliability while considering the inherent variabilities and uncertainties involved. A number of field pavement sections with well documented performance histories and high quality field and laboratory data were used for this purpose. Moreover, a reliability computation methodology that incorporates a central composite design (CCD) response surface approach (RS) is proposed. Appropriate statistical characterization of the dominant design parameters was performed considering its key role in reliability analysis. A first order reliability method (FORM) was used to compute pavement performance reliability and to establish the partial safety factors of the design procedure. Illustrative examples based on the developed LRFD procedure have demonstrated clearly its capacity of delivering designs with uniform reliability.

  • 47.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Resilient properties of binary granular mixtures: A numerical investigatio2016In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 76, p. 222-233Article in journal (Refereed)
    Abstract [en]

    The effect of stress level on the resilient modulus for binary mixtures of elastic spheres under triaxial loading is investigated using the discrete element method. The secant modulus during the first cycle of unloading is used as an estimate of the modulus after several load cycles due to computational time restrains. Later in the paper, its adequacy as an accurate and efficient estimator is shown. Numerical results are statistically compared with existing relations characterizing the stress dependency of the resilient modulus for real granular materials. It is concluded that the modulus prediction is significantly improved considering the effect of the deviator stress in addition to the confinement stress, obtaining a good correlation between the modulus and the confinement to deviator stress ratio for the numerical mixtures. The stress dependency of a recently proposed soil fabric classification system, based on force transmission considerations at particulate level, is also studied and its correlation with performance investigated. It is found that the relative load-bearing role of coarse and fine components is governed by the deviator to confinement stress ratio. However, the implemented fabric classification is fairly insensitive to changes in this ratio. Regarding resilient performance, interactive fabrics show the stiffest response whereas underfilled fabrics should be avoided due to a potential for instability.

  • 48.
    Krounis, Alexandra
    et al.
    KTH, School of Architecture and the Built Environment (ABE).
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Shear strength of partially bonded concrete-rock interfaces for application in dam stability analyses2016In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, no 7, p. 2711-2722Article in journal (Refereed)
    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.

  • 49.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Nordfelt, Ingmar
    Dynapac Compaction Equipment AB.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Soil compaction by vibratory roller with variable frequency2016In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656Article in journal (Refereed)
    Abstract [en]

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

  • 50.
    Abbaszadeh Shahri, Abbas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Updated relations for the uniaxial compressive strength of marlstones based on P-wave velocity and point load index test2016In: INNOVATIVE INFRASTRUCTURE SOLUTIONS, ISSN 2364-4176, Vol. 1, no 1, article id UNSP 17Article in journal (Refereed)
    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.

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