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  • 1.
    Ferdos, Farzad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Internal Erosion Phenomena in Embankment Dams: Throughflow and internal erosion mechanisms2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

     In this study, two major internal erosion initiation processes, suffusion and concentrated leak mechanisms, which lead to both defect formation in a dam’s body and its foundation and high throughflow in dams subjected to internal erosion were studied. This understanding has the potential to facilitate numerical modelling and expedite dam safety assessment studies. 

    The throughflow properties of coarse rockfill material were studied by; analysing filed pump test data, performing extensive laboratory experiments with a large-scale apparatus and numerically simulating the three-dimensional flow through coarse rock materials, replicating the material used in the laboratory experiments.

    Results from the tests demonstrate that the parameters of the nonlinear momentum equation of the flow depend on the Reynolds number for pore Reynolds numbers lower than 60000. 

    Numerical studies were also carried out to conduct numerical experiments. By applying a Lagrangian particle tracking method, a model for estimating the lengths of the flow channels in the porous media was developed.  The shear forces exerted on the coarse particles in the porous media were found to be significantly dependent on the inertial forces of the flow.

    Suffusion and concentrated leak mechanisms were also studied by means of laboratory experiments to develop a theoretical framework for continuum-based numerical modelling. An erosion apparatus was designed and constructed with the capability of applying hydraulic and mechanical loading. Results were then used to develop constitutive laws of the soil erosion as a function of the applied hydromechanical load for both suffusion and concentrated leak mechanisms. Both the initiation and mass removal rate of were found to be dependent on the soil in-situ stresses.

    A three-dimensional electrical-resistivity-based tomography method was also adopted for the internal erosion apparatus and was found to be successful in visualising the porosity evolution due to suffusion.

  • 2.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Dargahi, Bijan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation2016Inngår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, nr 6, s. 663-677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Analyses of turbulent flows through the downstream slopes of embankment dams are important for dam safety assessments, especially considering high-risk scenarios such as a sudden release of water due to internal erosion. Flow prediction is difficult in such situations due to coarseness of construction materials and high Reynolds numbers. The present study addresses this issue through comprehensive numerical modelling. The novelty of the proposed approach lies in a combination of large-scale experiments and three-dimensional numerical simulations, leading to a fully calibrated and validated model that is applicable to flows through cobble-sized materials (100–160 mm in diameter) at high Reynolds numbers (>104). Comparing the results of the standard turbulence models to data from the large-sale experiments, the renormalization group theory-based model yielded the smallest relative errors based on the hydraulic gradients. Considering the flow field, the turbulent shear stress increased by a factor of 17, and the time-averaged vorticities intensified by factors of 2, 6 and 10 for vorticities in the x-, y- and z-directions, respectively, due to the presence of cobbles.

  • 3.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Dargahi, Bijan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part II: flow physics2016Inngår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, nr 6, s. 678-691Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evaluation of hydraulic performance of coarse porous media at high Reynolds numbers is of significant importance for dam safety assessment. To address this task, the present study uses a numerical approach based on a rigorous theoretical framework. The novelty of the study lies in the application of a fully calibrated and validated numerical three-dimensional model and a set of modified equations for momentum transfer and the associated coefficients for flow in porous media. A Lagrangian particle tracking model was used to estimate the lengths of the flow channels that developed in the porous media. Gamma distributions were fitted to the normalized channel lengths, and the scale and shape parameters of the gamma distribution were found to be Reynolds number dependent. These shape parameters can be estimated from the suggested polynomial equations. The proposed normalized length parameter can be used to evaluate permeability, energy dissipation, induced forces, and diffusion. It was found that shear forces exerted on the coarse particles depend on the inertial forces of the flow and can be estimated using the proposed equation for the developed turbulent flows in porous media.

  • 4.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Dargahi, Bijan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Solari, Luca
    Mechanism of concentrated leak erosion phenomenon in embankment dams2016Manuskript (preprint) (Annet vitenskapelig)
  • 5.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Dargahi, Bijan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Solari, Luca
    Mechanism of suffusion erosion phenomenon in embankment dams2016Manuskript (preprint) (Annet vitenskapelig)
  • 6.
    Ferdos, Farzad
    et al.
    Chalmers University of Technology.
    Jafarzadeh, Fardin
    Sharif University of Technology.
    Establishing Long Term Seepage Behavior of Zoned Embankment Dams with Three-Dimensional Seepage Analysis2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Since seepage-related problems are the main cause of morethan fourty percent of dam failures, seepage analysis is oneof the most important stages in the design process of anembankment dam. Seepage factors must be monitored in thedam’s body, abutments, and foundation during dam'soperating life for evaluating safety and conducting riskassessments [1]. Most of e designing analysis is performedtwo-dimensionally and therefore, little attention is paid toseepage through abutments. On the other hand, the extensionof the grout curtain inside the abutments, abutment materialproperties and dam site inhomogeneities, such as fault andcrushed zones are inevitably neglected when performing 2Dseepage analyses by this reason, 2D seepage analysis doesnot reflect real seepage factors and parameters [2]. In thiscase study, two and three-dimensional finite element (FE)models of an earth-fill dam are generated. Several steadystate seepage analyses, as long term seepage behaviorevaluation, are performed; the results are compared with theseepage monitored data from the instrumentation systeminstalled in the dam body and foundation. It is concluded thatconventional two-dimensional seepage models lead to resultsthat are somewhat unrealistic; instead, three-dimensional(3D) models are much more representative of reality and canbe used to evaluate seepage parameters in embankment dams.

  • 7.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Rosén, Lars
    Quantitative environmental footprints and sustainability evaluation of contaminated land remediation alternatives for two case studies2013Inngår i: Remediation Journal, ISSN 1051-5658, E-ISSN 1520-6831, Vol. 24, nr 1, s. 77-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Since the US Environmental Protection Agency (US EPA) launched its "green remediation" program and EU member states began to reassess their national regulations for environmental remediation in order to reach a Europe-wide consensus on policy and standards, the need and interest for sustainable remediation of contaminants from brownfields has grown considerably. Concomitantly, the ability to calculate and assess the suitability as well as the environmental footprints and associated risks of a growing number of remediation techniques has become a priority. The authors quantitatively evaluate the differences between various remediation techniques, and for this purpose, a number of ex situ and in situ remediation techniques are adapted to model 21 remediation scenarios for two contaminated sites in the Gothenburg region of Sweden: the Bohus Varv site on the Göta älv river bank and the Hexion site in Mölndal. A wide range of quantitative results for these models are presented, compared, and analyzed. Based on the results from both projects, it is concluded that: (1) remediation techniques requiring long distance residual transportation have significant footprints, except the transportation of contaminated residuals by train due to Swedish energy production conditions; (2) residual transportation by ship results in much higher SOx, NOx, and particle releases compared to the other alternatives; and (3) residual transporation by truck results in high accident risks. Finally, activities powered by electricity result in a reduced footprint compared to activities powered by fossil fuels, considering Swedish energy production conditions. The authors conducted a cross-benefit analysis of SiteWiseTM applications which recognizes its potential as a tool for presenting life cycle assessment analyses with appropriate system boundary definitions and an easy inventory analysis process. Results from this tool provide valuable support to decision makers aiming at more sustainable remediation.

  • 8.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Ekström, Ingvar
    Hydraulic Conductivity of Coarse Rockfill used in Hydraulic Structures2015Inngår i: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 108, nr 2, s. 367-391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Internal erosion is a major cause of embankment dam failure. Unravelling and instability of the downstream slope, initiated by internal erosion and leakage through the dam core, is one of the most likely breach mechanisms for large, zoned embankment dams. To be able to model this mechanism, the relationship between the hydraulic gradient and the flow velocity for the coarse rockfill material must be understood. Because most studies of this topic have focused on the flow parameters in gravel-size materials with Reynolds (Re) numbers lower than 25,000, permeability measurements are needed coarser rockfill material under heavily turbulent flow regimes prevailing in rockfill material under certain design flow scenarios. This paper presents the set-up and results of a series of field and laboratory experimental studies and the subsequent data interpretation, from which relevant hydraulic conductivity parameters, defined in applicable flow laws, were extracted. This study demonstrates that the exponent of a power flow law relating the hydraulic gradient and the flow velocity is Re number dependent for pore Re numbers 60,000. The power remains constant (Re number independent) above this Re number threshold for the fully developed turbulent regime. This validity threshold as well as the constant behaviour also applies if the flow law is written in a quadratic form. The aforementioned threshold lies beyond the ranges investigated experimentally by previous researchers. The experiments in this study examined Re numbers as large as 220,000 for grain-diameter distributions in the range 100-160 mm and as large as 320,000 in the range 160-240 mm.

  • 9.
    Ferdos, Farzad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Yang, James
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Characterization of hydraulic behaviours of coarse rock materials in a large permeameter2013Inngår i: Journal of Geoscience and Environment Protection, ISSN 2327-4336, Vol. 1, nr 3, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydraulic behavior of a rock material structure is a major feature for its design and safety assessment. Similar to all other physical prob-lems, in order to enclose the governing equations systems and achieve a solution, the hydraulic characteristics of these materials need to be determined experimentally and implemented then into adopted thermo-dynamical models. This paper covers the process of the design, con-struction and operation of an experimental rig built for this specific purpose. Using the constructed large-scale permeameter, tests have been conducted. The non-linear hydraulic behavior of various materials under extreme turbulent conditions, where Reynolds number reaches un-precedented values, has not been studied before. Preliminary results are presented and discussed.

  • 10.
    Jafarzadeh, Fardin
    et al.
    Sharif University of Technology.
    Ferdos, Farzad
    Sharif University of Technology.
    Soleimanbeigi, Ali
    Sharif University of Technology.
    Comparison between two and three dimensional seepage analysis of rock-fill dams constructed in narrow valleys a case study: La comparaison entre l’analyse de l’infiltration du barrage en enrochement a deux ettrois dimensions construit dans la étroit vallée : on étude de cas2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Since seepage-related problems account for the cause of more than50% of dam failures, seepage analysis serves as one of the most significantstages in the design process of an embankment dam. Currently, a twodimensional (2D) seepage analysis in atypical or maximum cross section of thedam is performed instead of its three dimensional (3D) analysis for simplicity. Inthis way, little or no attention is paid to the seepage through side abutments.Moreover the role of grout curtain extensions into the side abutments andabutment material properties are inevitably neglected when performing a 2Dseepage analysis. In this paper, two and three-dimensional models of a rockfilldam during operation state are generated and several unsteady and steady stateseepage analyses are performed using finite element method (FEM). The resultsobtained from 2D and 3D seepage analyses were compared with measurementsfrom the instrumentation system installed in the dam body and foundation duringconstruction. It is concluded that for embankment dams to be constructed innarrow valleys, 2D seepage analysis results are far from reality and considering3D modeling of such dam sites is vital. In addition several designing andillustrative graphs were developed to calculate 3D discharge rates and hydraulicgradients from those obtained from 2D seepage analysis.

  • 11. Masi, Matteo
    et al.
    Ferdos, Farzad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Losito, Gabriella
    Solari, Luca
    Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tomography system developed on laboratory scaleManuskript (preprint) (Annet vitenskapelig)
1 - 11 of 11
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