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  • 1. Abiye, T. A.
    et al.
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Arsenic concentration in groundwater: Archetypal study from South Africa2019Inngår i: Groundwater for Sustainable Development, ISSN 2352-801X, Vol. 9, artikkel-id 100246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    South Africa does not have significant surface water resources, which is often easily affected by unpredictable and rapidly changing climatic variables, due to its location in the arid and semi-arid climatic setting. In large part of the country, groundwater from weathered and fractured crystalline rocks plays pivotal role in sustaining the livelihood, often it contains toxic metals released from the host rocks. The host rocks that are responsible for arsenic release in groundwater are primarily enriched due to metamorphism and igneous processes that resulted in the enrichment of economic minerals. Preliminary assessment indicates that the main arsenic containing minerals are arsenopyrite (FeAsS), arsenical oxide, sulpharsenide, arsenopyritical reefs, leucopyrite, löllingite (FeAs2) and scorodite (FeAsO4·2H2O). Owing to the release of arsenic from highly mineralized rocks that constitute the aquifers, arsenic concentration in the groundwater reaches up to 253 μg/L (Namaqualand), 6150 μg/L (west of Johannesburg), about 500 μg/L in the Karoo aquifers, considerably higher than the WHO guideline value of 10 μg/L. Acid mine drainage from coal and gold mining is also found to be an important source of arsenic and other toxic metals in groundwater.

  • 2.
    Abrehdary, Majid
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och satellitpositionering.
    Sjöberg, Lars E.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och satellitpositionering.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och satellitpositionering. Univ Gavle, Dept Ind Dev IT & Land Management, SE-80176 Gavle, Sweden.
    Combined Moho parameters determination using CRUST1.0 and Vening Meinesz-Moritz model2015Inngår i: Journal of Earth Science, ISSN 1674-487X, E-ISSN 1867-111X, Vol. 26, nr 4, s. 607-616Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    According to Vening Meinesz-Moritz (VMM) global inverse isostatic problem, either the Moho density contrast (crust-mantle density contrast) or the Moho geometry can be estimated by solving a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parameters are presented by combining the global geopotential model (GOCO-03S), topography (DTM2006) and a seismic crust model, the latter being the recent digital global crustal model (CRUST1.0) with a resolution of 1A(0)x1A(0). The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m(3), with a global average of 321 kg/m(3), and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our leastsquares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.

  • 3. Andersson, J. C.
    et al.
    Feng, X.
    Pan, P.
    Koyama, T.
    Kwon, S.
    Lee, C. S.
    Rinne, M.
    Shen, B.
    Lan, H.
    Martin, C. D.
    Chen, Y.
    Zhou, C.
    Blaheta, R.
    Kohut, R.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Modeling the Äspö Pillar stability experiment2010Inngår i: Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010, 2010, s. 787-790Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents results of the 1st stages ofTaskAof the Decovalex 2011 project, the numerical modeling of the Äspö Pillar Stability experiment performed by the Äspö Hard Rock Laboratory of the Swedish Nuclear Fuel and Waste Management Company (SKB). The objective is to perform back calculation of the Äspö pillar behavior using state of the art numerical modeling techniques for the material behavior. The work is divided into three stages and it is the first stage of thework that will be presented in this paper. Seven international teams from six different countries participated in the task and contributed to the results presented in this paper, concerning back calculation of uniaxial and triaxial compressive core testing and elastic back calculation of the stress path for excavation-induced stresses. The results are useful for understanding the occurrence of spalling in the upper part of the pillar during excavation and the stress path modeling gives the first approximation of the yielding strength of the pillar. The calculated results agree well with observations measured during experiment.

  • 4.
    Artemyev, A. V.
    et al.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA.;RAS, Space Res Inst, Moscow, Russia..
    Pritchett, P. L.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90024 USA..
    Angelopoulos, V.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Zhang, X. -J
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Lu, S.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Runov, A.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA..
    Wellenzohn, S.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.;Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Lindqvist, Per-Arne
    KTH.
    Ergun, R. E.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Field-Aligned Currents Originating From the Magnetic Reconnection Region: Conjugate MMS-ARTEMIS Observations2018Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, nr 12, s. 5836-5844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-Earth magnetic reconnection reconfigures the magnetotail and produces strong plasma flows that transport plasma sheet particles and electromagnetic energy to the inner magnetosphere. An essential element of such a reconfiguration is strong, transient field-aligned currents. These currents, believed to be generated within the plasma sheet and closed at the ionosphere, are responsible for magnetosphere-ionosphere coupling during substorms. We use conjugate measurements from Magnetospheric Multiscale (MMS) at the plasma sheet boundary (around x approximate to- 10R(E)) and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) at the equator (around x approximate to- 60R(E)) to explore the potential generation region of these currents. We find a clear correlation between the field-aligned current intensity measured by MMS and the tailward plasma sheet flows measured by ARTEMIS. To better understand the origin of this correlation, we compare spacecraft observations with results from 3-D particle-in-cell simulations of magnetotail reconnection. The comparison reveals that field-aligned currents and plasma flows start, wax, and wane due to the development of a reconnection region between MMS (near-Earth) and ARTEMIS (at lunar distance). A weak correlation between the field-aligned current intensity at MMS and earthward flow magnitudes at ARTEMIS suggests that distant magnetotail reconnection does not significantly contribute to the generation of the observed near-Earth currents. Our findings support the idea that the dominant role of the near-Earth magnetotail reconnection in the field-aligned current generation is likely responsible for their transient nature, whereas more steady distant tail reconnection would support long-term field-aligned current system. Plain Language Summary Field-aligned currents connect the Earth magnetotail and ionosphere, proving energy and information transport from the region where main energy release process, magnetic reconnection, occurs to the region where the collisional energy dissipation takes place. Therefore, investigation and modeling of the field-aligned current generation is important problem of the magnetosphere plasma physics. However, field-aligned current investigation requires simultaneous observations of reconnection signatures in the magnetotail and at high latitudes. Simultaneous and conjugate operation of two multispacecraft missions, Magnetospheric Multiscale and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun, for the first time provide an opportunity for such investigation. Combining spacecraft observations with results from 3-D particle-in-cell simulations of magnetotail reconnection, we demonstrate that field-aligned currents and plasma flows start, wax, and wane due to the development of a reconnection region between near-Earth (Magnetospheric Multiscale location) and lunar distant tail (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun location). Our findings support the idea that the dominant role of the near-Earth magnetotail reconnection in the field-aligned current generation is likely responsible for their transient nature, whereas more steady distant tail reconnection would support long-term field-aligned current system.

  • 5. Baghbanan, A.
    et al.
    Sookhak, A.
    Hashemalhosseini, H.
    Bagheri, Mehdi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Block stability analysis around a large cavern using probabilistic approach2010Inngår i: Rock Engineering in Difficult Ground Conditions - Soft Rocks and Karst - Proceedings of the Regional Symposium of the International Society for Rock Mechanics, EUROCK 2009, 2010, s. 435-440Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Block stability analysis around a large excavation is analyzed with both Probabilistic Kinematics Limit Equilibrium (PKLE) and Discrete Fracture Network-Distinct Element Method (DFNDEM) approaches. Different combination of geometric parameters of fracture sets are selected in PKLE method and a series of numerical DEM modeling are performed on generated and validated DFN models in DFN-DEM approach to measure volume of potential unstable blocks and also minimum required support patterns. The mean volume of unstable blocks for PKLE with limited joint length assumption is fairly close to DFN models and they are far from mean value of PKLE when the joint length is extended infinitely. The minimum required support pattern for PKLE is smaller than DEM models which means that the PKLE design tool is underestimated compared with DFN-DEM method which benefits more realistic conceptual model and facilitates more sophisticate simulation tool.

  • 6.
    Bagherbandi, M.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Eshagh, Mehdi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Crustal thickness recovery using an isostatic model and GOCE data2012Inngår i: Earth Planets and Space, ISSN 1343-8832, E-ISSN 1880-5981, Vol. 64, nr 11, s. 1053-1057Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the GOCE satellite mission goals is to study the Earth's interior structure including its crustal thickness. A gravimetric-isostatic Moho model, based on the Vening Meinesz-Moritz (VMM) theory and GOCE gradiomet-ric data, is determined beneath Iran's continental shelf and surrounding seas. The terrestrial gravimetric data of Iran are also used in a nonlinear inversion for a recovering-Moho model applying the VMM model. The newly-computed Moho models are compared with the Moho data taken from CRUST2.0. The root-mean-square (RMS) of differences between the CRUST2.0 Moho model and the recovered model from GOCE and that from the terrestrial gravimetric data are 3.8 km and 4.6 km, respectively.

  • 7.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Global earth isostatic model using smoothed Airy-Heiskanen and Vening Meinesz hypotheses2012Inngår i: Earth Science Informatics, ISSN 1865-0473, Vol. 5, nr 2, s. 93-104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Isostatic hypotheses are used for different purposes in geophysics and geodesy. The Erath crustal thickness modelling is more complicated than the classical isostatic models. In this study we try to modify Airy-Hesiskanen model, utilizing a smoothing factor, to a model with regional or global isostatic model through a modern solution of the gravimetric-isostatic Vening Meinesz model and CRUST.0. In Airy-Hesiskanen's theory there is no correlation between neighbouring crustal columns, while this must be the case in reality due to the elasticity of the Earth. The idea is to keep the simplicity of the Airy-Heiskanen model, because it needs only the topographic data, and change the model which becomes to a model with regional/global isostatic model. The isostatic assumption for compensating the topographic potential is incomplete, as there are other geophysical phenomena which should be considered. Using the isostatic hypothesis for determining the depth of crust causes some disturbing signals in the gravity anomaly (approximately 285 mGal), which influence the crustal thickness determination. In this paper a simple method use for removing these effects. Spherical harmonic potential coefficients of the topographic compensation masses are used for modifying Airy-Heiskanen's model in a least-square adjustment procedure by estimating smoothing factor. The numerical analysis shows that below degree 10, the modified Airy-Hesiskanen and Vening Meinesz models are close together. Smoothing factors for modifying the Airy-Hesiskanen model vary from 0.75 to 0.64 between degrees 200 and 2159.

  • 8.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Moholso: A MATLAB program to determine crustal thickness by an isostatic and a global gravitational model2012Inngår i: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 44, s. 177-183Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper focuses on the modeling of the boundary between Earth's crust and upper mantle using a gravimetric-isostatic model. Here a MATLAB code is presented based on the gravimetric-isostatic model i.e. the Veiling Meinesz-Moritz model. Inverse problems in isostasy consist in making the isostatic anomalies to be zero under a certain isostatic hypothesis. The Vening Meinesz-Moritz problem is to determine the Moho depth such that the compensating attraction totally compensates the Bouguer gravity anomaly on the Earth's surface, implying that the isostatic anomaly vanishes on the Earth's surface. The main idea is easy but the theoretical analysis is somewhat difficult. Here a practical method to recover the Moho depth from the gravity data is used in the MATLAB code (Moholso.m) based on the Vening Meinesz-Moritz method. The code has been designed based on different sub-codes. The body of the main code works according to the vectorization technique, because this technique causes that the speed of code increases. One of the important possible limitations for the code is over-flow and under-flow for higher degrees in the fully normalized associated Legendre function. This problem occurs in the subroutine applied in this study, it limits the numerical study up to degrees 1800-2000.

  • 9. Bagnoud, Alexandre
    et al.
    Chourey, Karuna
    Hettich, Robert L.
    de Bruijn, Ino
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Andersson, Anders F.
    Leupin, Olivier X.
    Schwyn, Bernhard
    Bernier-Latmani, Rizlan
    Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock2016Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, artikkel-id 12770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Opalinus Clay formation will host geological nuclear waste repositories in Switzerland. It is expected that gas pressure will build-up due to hydrogen production from steel corrosion, jeopardizing the integrity of the engineered barriers. In an in situ experiment located in the Mont Terri Underground Rock Laboratory, we demonstrate that hydrogen is consumed by microorganisms, fuelling a microbial community. Metagenomic binning and metaproteomic analysis of this deep subsurface community reveals a carbon cycle driven by autotrophic hydrogen oxidizers belonging to novel genera. Necromass is then processed by fermenters, followed by complete oxidation to carbon dioxide by heterotrophic sulfate-reducing bacteria, which closes the cycle. This microbial metabolic web can be integrated in the design of geological repositories to reduce pressure build-up. This study shows that Opalinus Clay harbours the potential for chemolithoautotrophic-based system, and provides a model of microbial carbon cycle in deep subsurface environments where hydrogen and sulfate are present.

  • 10. Berger, T.
    et al.
    Mathurin, F. A.
    Gustafsson, Jon Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. Swedish University of Agricultural Sciences, Sweden.
    Peltola, P.
    Åström, M.E.
    The impact of fluoride on Al abundance and speciation in boreal streams2015Inngår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 409, s. 118-124Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of fluoride on the abundance and speciation of aluminium (Al) was investigated in three boreal streams characterised by overall high concentrations of fluoride and dissolved organic matter. Stream-water sampling was carried out several times a year for at least 4 years, and a chemical equilibrium model (Visual MINTEQ) was applied in order to model the proportion of colloidal and organically/inorganically complexed Al in the waters. The Al concentrations in filtered (0.45 μm) water samples were inversely correlated with pH, and reached values up to approximately 1. mg/L during low pH conditions (pH < 6.0). In a stream with high fluoride concentrations, as compared to a similar stream with only moderately elevated fluoride concentrations, the Al concentrations were consistently elevated. For the stream with high concentrations of fluoride and Al, the model predicted both high concentrations and proportions of Al-fluoride complexation. This prediction indicates that high fluoride levels contribute to raise both the Al abundance and the ratio of inorganic to organic Al complexation in stream water. In contrast, for another stream with high fluoride concentrations and consistently high (near neutral) pH, there was no evidence of fluoride affecting Al concentration or complexation. These results show that it is important to focus future studies on the role of high levels of dissolved fluoride on both the speciation and the toxicity of Al in stream water.

  • 11. Chen, Y.F
    et al.
    Zhou, C.B
    Mao, X.Y
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    Numerical simulation of coupled thermal elastic behaviors for hard rock pillar in Äspö Pillar Stability Experiment, Sweden2010Inngår i: Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering, ISSN 1000-4548, Vol. 32, nr 8, s. 1200-1206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The goal of the Äspö Pillar Stability Experiment performed in Äspö Hard Rock Laboratory, Sweden is to investigate the mechanical response and progressive failure process of ahard rock pillar during excavation and heating. Numerical simulation of the thermalelastic behaviors for the pillar is one of the three tasks of the DECOVALEX-2011 project. The evolutions of stress, deformation and temperature of the pillar are modeled by using a coupled thermal elasticity model. The research results demonstrate that the thermalelasticity model is suitable for describing the coupled thermal mechanical behaviors of the pillar during excavation and heating. The stress redistribution and temperature evolution processes of the pillar are largely modeled, and the failure process and its propagation are qualitatively analyzed. The major limitations of the thermal elasticity model are its absence of the multiphase flow and progressive failure processes. The model developed and the modeling experiences accumulated in this study may be helpful for the stability and safety assessment of the hard granite host rock in China's Beishan preselected area for high-level radioactive waste disposal.

  • 12. Chuang, T.C
    et al.
    Henkel, Herbert
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    GIS Visualization of Complex Geoscientific Data from the Björkö Structure2006Inngår i: GeoCongress 2006: Geotechnical Engineering in the Information Technology Age, Atlanta: American Society of Civil Engineers (ASCE), 2006, 2, , s. 204-209s. 204-209Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on the idea of Scientific Visualization, this research is aimed to visualize the complex geoscientific data to support the mapping work of the Björkö Energy Project, which has an ultimate goal to place a heat exchanging mechanism at the most suitable location in the subsurface. The production from this impact crater structure is expecting to supply the heating use for the great Stockholm area. The various point data types were compiled to diverse maps according to their characteristics. Several GIS and numerical tools are introduced integratedly to accomplish the work. The research in addition helps to streamline the data and maps processing activities carried out by the varied working groups

  • 13. Claudio, P.
    et al.
    Von Brömssen, Mattias
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Claus, K.
    Møller, M. L.
    Marco, P.
    Umberto, M.
    Geochemical modelling application for a 1-d arsenic reactive transport study in alluvial aquifers, Matlab Upazila, Bangladesh2009Inngår i: Rendiconti Online Societa Geologica Italiana, ISSN 2035-8008, Vol. 6, s. 364-365Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanistic modelling was used to investigate the hydrochemical evolution along a vertical column, should cross-contamination occur. 1-D reactive transport was carried out to assess sorption effects on aqueous/solid arsenic distribution in Matlab Upazila, Bangladesh. Thermodynamic relationships between aqueous ions and aquifer materials have been investigated: comparison between redox couples shows electrochemical disequilibrium; sorption mainly occurs on weak and strong Hydrous Ferric-Oxides, described by the Surface Complexation Mode. The basis for reactive transport calculations is given by a static model, that evaluates the competing ions net effect: they reduce by ca. 50% arsenic bounding. Desorption process alone can give unacceptable As (aq) concentrations, starting from only a few mg/kg As (sorb). Redox zonation was the starting point for the model conception, which allowed calculating the contamination evolution in an oxidising As-low aquifer. Groundwater analysis is worked out for a 20 cells column of aquifer material, whose top represents the upper reducing aquifer, the bottom the oxidising aquifer; contamination takes place through an As-rich solution percolating into the column. Results are a function of the flow velocity, that needs to be carefully defined before further modelling.

  • 14.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattenvårdsteknik.
    The tempered one-sided stable density: a universal model for hydrological transport?2011Inngår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 6, nr 3, s. 034008-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A generalized distribution for the water residence time in hydrological transport is proposed in the form of the tempered one-sided stable (TOSS) density. It is shown that limiting cases of the TOSS distribution recover virtually all distributions that have been considered in the literature for hydrological transport, from plug flow to flow reactor, the advection-dispersion model, and the gamma and Levy densities. The stable property of TOSS is particularly important, enabling a seamless transition between a time-domain random walk, and the Lagrangian (trajectory) approach along hydrological transport pathways.

  • 15. David, E.
    et al.
    Zimmerman, Robert W.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    Sliding crack model for the uniaxial compression of rock2007Inngår i: Proceedings of the 1st Canada-US Rock Mechanics Symposium - Rock Mechanics Meeting Society's Challenges and Demands, Taylor & Francis, 2007, s. 575-580Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Uniaxial compression tests on rocks, if conducted at stresses below failure, typically show non-linearity in the stress-strain curve, and hysteresis. Walsh (J. Geophys. Res., 1965) explained this behavior in terms of frictional sliding along the faces of closed cracks. Although well known and widely cited, Walsh's model has not previously been developed in sufficient detail to be used for quantitative predictions. We revisit and extend his model, by including the effect of the stress required to close an initially open crack, and we examine the unloading process in detail. Our analysis leads to closed-form expressions for the loading and unloading portions of the stress-strain curve, as functions of elastic modulus of the uncracked rock, the crack density, the characteristic aspect ratio, and the crack friction coefficient. The model provides a good fit to the loading and unloading portions of the stress-strain curves, for experimental data on sandstones taken from the literature.

  • 16.
    Dehkordi, Seyed Emad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. University of Western Ontario, Canada.
    Olofsson, Bo
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Schincariol, Robert A.
    Effect of groundwater flow in vertical and horizontal fractures on borehole heat exchanger temperatures2015Inngår i: Bulletin of Engineering Geology and the Environment, ISSN 1435-9529, E-ISSN 1435-9537, Vol. 74, nr 2, s. 479-491Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Vertical closed loop systems, also known as borehole heat exchangers (BHEs), are a popular way of extracting the ground source heat energy. Primary factors affecting the performance of BHEs are the thermal and hydrogeological properties of the subsurface. Groundwater flow is known to potentially influence heat transport and system performance. The effect of groundwater movement is more commonly studied under homogeneous conditions. However, in heterogeneous fractured rocks, BHEs are more common than horizontal or open loops due to lack of sufficient soil layers and productive aquifers. The finite-element modelling shows that fractures can play an important role in BHE functioning. Especially, vertical open fractures (≥1 mm) near the borehole (≤10 m) can have a considerable impact. Although increase in fracture aperture continuously affects the subsurface and BHE temperatures, the increase in its effect progressively lessens. Depending on the distance and aperture, one major fracture influencing the BHE operation performance can be identified; yet a larger number of fractures may govern heat transport (thermal plume outline) and thermal recovery. Individually, horizontal fractures may have less influence than vertical fractures. However, as the density of horizontal fractures increases, their impact can be major, exceeding that of fracture aperture. In particular, we propose that measurements of rock thermal properties be combined with fracture mapping, to better analyse the thermal response testing results and integrate the configuration of fractures in design and layout of the BHE(s). This is particularly valid for (vertical) fractures not intersecting with the borehole.

  • 17.
    Dehkordi, Seyed Emad
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Schincariol, Robert A.
    Olofsson, Bo
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers2014Inngår i: Ground Water, ISSN 0017-467X, E-ISSN 1745-6584Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10−7 m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings.

  • 18.
    Earon, Robert
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Dehkordi, Seyed Emad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Olofsson, Bo
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Groundwater Resources Potential in Hard Rock Terrain: A Multivariate Approach2014Inngår i: Ground Water, ISSN 0017-467X, E-ISSN 1745-6584Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Groundwater resources are limited and difficult to predict in crystalline bedrock due to heterogeneity and anisotropy in rock fracture systems. Municipal-level governments often lack the resources for traditional hydrogeological tests when planning for sustainable use of water resources. A new methodology for assessing groundwater resources potential (GRP) based on geological and topographical factors using principal component analysis (PCA) and analysis of variance (ANOVA) was developed and tested. ANOVA results demonstrated statistically significant differences in classed variable groups as well as in classed GRP scores with regard to hydrogeological indicators, such as specific capacity (SC) and transmissivity. Results of PCA were used to govern the weight of the variables used in the prediction maps. GRP scores were able to identify 79% of wells in a verification dataset, which had SC values less than the total dataset median. GRP values showed statistically significant correlations using both parametric (using transformed datasets) and non-parametric methods. The method shows promise for municipal or regional level planning in crystalline terrains with high levels of heterogeneity and anisotropy as a hydrogeologically and statistically based tool to assist in assessing groundwater resources. The methodology is executed in a geographic information systems environment, and uses often readily available data, such as geological maps, feature maps and topography, and thus does not require expensive and time-consuming aquifer tests.

  • 19.
    Eshagh, Mehdi
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Quality Description For Gravimetric And Seismic Moho Models Of Fennoscandia Through A Combined Adjustment2012Inngår i: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, Vol. 47, nr 4, s. 388-401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The gravimetric model of the Moho discontinuity is usually derived based on isostatic adjustment theories considering floating crust on the viscous mantle. In computation of such a model some a priori information about the density contrast between the crust and mantle and the mean Moho depth are required. Due to our poor knowledge about them they are assumed unrealistically constant. In this paper, our idea is to improve a computed gravimetric Moho model, by the Vening Meinesz-Moritz theory, using the seismic model in Fennoscandia and estimate the error of each model through a combined adjustment with variance component estimation process. Corrective surfaces of bi-linear, bi-quadratic, bi-cubic and multi-quadric radial based function are used to model the discrepancies between the models and estimating the errors of the models. Numerical studies show that in the case of using the bi-linear surface negative variance components were come out, the bi-quadratic can model the difference better and delivers errors of 2.7 km and 1.5 km for the gravimetric and seismic models, respectively. These errors are 2.1 km and 1.6 km in the case of using the bi-cubic surface and 1 km and 1.5 km when the multi-quadric radial base function is used. The combined gravimetric models will be computed based on the estimated errors and each corrective surface.

  • 20.
    Fardin, Nader
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Feng, Q.
    Stephansson, Ove
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Application of a new in situ 3D laser scanner to study the scale effect on the rock joint surface roughness2004Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, nr 2, s. 329-335Artikkel i tidsskrift (Fagfellevurdert)
  • 21. Feng, X. -T
    et al.
    Liu, J.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    Research and application on coupled t-h-m-c processes of geological media in china - a review2004Inngår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications, Elsevier, 2004, nr C, s. 37-48Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Theoretical models of coupled T-H-M-C processes of geological media and the associated numerical solutions have become an attractive research focus in geomechanics and related fields in China. This paper provides a systematic overview of the past progress in the fundamental studies of the coupled THM models and numerical methods, and their applications in the fields of oil/gas reservoir, coal mining, and water resources engineering works. The key areas of weakness in research in this field are also outlined and possible directions for the future development are discussed.

  • 22.
    Ferdous, Md Ruknul
    et al.
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Univ Amsterdam, Fac Social & Behav Sci, NL-1012 WX Amsterdam, Netherlands..
    Wesselink, Anna
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands..
    Brandimarte, Luigia
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Resurser, energi och infrastruktur.
    Slager, Kymo
    Deltares, NL-2600 MH Delft, Netherlands..
    Zwarteveen, Margreet
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Univ Amsterdam, Fac Social & Behav Sci, NL-1012 WX Amsterdam, Netherlands..
    Di Baldassarre, Giuliano
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Uppsala Univ, Dept Earth Sci, S-75236 Uppsala, Sweden.;CNDS, Ctr Nat Hazards & Disaster Sci, S-75236 Uppsala, Sweden..
    Socio-hydrological spaces in the Jamuna River floodplain in Bangladesh2018Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 10, s. 5159-5173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Socio-hydrology aims to understand the dynamics and co-evolution of coupled human-water systems, with research consisting of generic models as well as specific case studies. In this paper, we propose a concept to help bridge the gap between these two types of socio-hydrological studies: socio-hydrological spaces (SHSs). A socio-hydrological space is a geographical area in a landscape. Its particular combination of hydrological and social features gives rise to the emergence of distinct interactions and dynamics (patterns) between society and water. Socio-hydrological research on human-flood interactions has found two generic responses, "fight" or "adapt". Distilling the patterns resulting from these responses in case studies provides a promising way to relate contextual specificities to the generic patterns described by conceptual models. Through the use of SHSs, different cases can be compared globally without aspiring to capturing them in a formal model. We illustrate the use of SHS for the Jamuna floodplain, Bangladesh. We use narratives and experiences of local experts and inhabitants to empirically describe and delimit SHS. We corroborated the resulting classification through the statistical analysis of primary data collected for the purpose (household surveys and focus group discussions) and secondary data (statistics, maps etc.). Our example of the use of SHSs shows that the concept draws attention to how historical patterns in the co-evolution of social behaviour, natural processes and technological interventions give rise to different landscapes, different styles of living and different ways of organising livelihoods. This provides a texture to the more generic patterns generated by socio-hydrological models, promising to make the resulting analysis more directly useful for decision makers. We propose that the usefulness of this concept in other floodplains, and for other socio-hydrological systems than floodplains, should be explored.

  • 23. Goosse, H.
    et al.
    Roche, D. M.
    Mairesse, A.
    Berger, Marit
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens.
    Modelling past sea ice changes2013Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 79, s. 191-206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dominant characteristic of the available simulations of past sea ice changes is the strong link between the model results for modern and past climates. Nearly all the models have similar extent for pre-industrial conditions and for the mid-Holocene. The models with the largest extent at Last Glacial Maximum (LGM) are also characterized by large pre-industrial values. As a consequence, the causes of model biases and of the spread of model responses identified for present-day conditions appear relevant when simulating the past sea ice changes. Nevertheless, the models that display a relatively realistic sea-ice cover for present-day conditions often display contrasted response for some past periods. The difference appears particularly large for the LGM in the Southern Ocean and for the summer ice extent in the Arctic for the early Holocene (and to a smaller extent for the mid-Holocene). Those periods are thus key ones to evaluate model behaviour and model physics in conditions different from those of the last decades. Paleoclimate modelling is also an invaluable tool to test hypotheses that could explain the signal recorded by proxies and thus to improve our understanding of climate dynamics. Model analyses have been focused on specific processes, such as the role of atmospheric and ocean heat transport in sea ice changes or the relative magnitude of the model response to different forcings. The studies devoted to the early Holocene provide an interesting example in this framework as both radiative forcing and freshwater discharge from the ice sheets were very different compared to now. This is thus a good target to identify the dominant processes ruling the system behaviour and to evaluate the way models represent them.

  • 24.
    Hossain, Mohammed
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Sustainable Arsenic Mitigation A Strategy for Scaling-up Safe Water Access: A Strategy for Scaling-up Safe Water Access2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In rural Bangladesh, the drinking water supply is mostly dependent upon manually operated hand pumped tubewells, installed by the local community. The presence of natural arsenic (As) in groundwater and its wide scale occurrence has drastically reduced the safe water access across the country and put tens of millions of people under health risk. Despite significant progress in understanding the source and distribution of As and its mobilization through sediment-water interactions, there has been limited success in mitigation since the problem was discovered in the country’s water supply in 1993. This study evaluated the viability of other kinds of alternative safe drinking water options and found tubewells are the most suitable due to simplicity and technical suitability, a wide acceptance by society and above all low cost for installation, operation and maintenance. During planning and decision making in the process of tubewell installation, depth of the tubewell is a key parameter as it is related to groundwater quality and cost of installation. The shallow wells (usually < 80m) are mostly at risk of As contamination. One mitigation option are deep wells drilled countrywide to depths of around 250 m. Compared to safe water demand, the number of deep wells is still very low, as the installation cost is beyond affordability of the local community, especially for the poor and disadvantaged section of the society. Using depth-specific piezometers (n=82) installed in 15 locations spread over the 410 km2 area of Matlab (an As-hot spot) in southeastern Bangladesh, groundwater monitoring was done over a 3 year period (pre- and post-monsoon for 2009-2011 period). Measurements were performed for hydrogeological characterization of shallow, intermediate deep and deep aquifer systems to determine the possibility of targeting safe aquifers at different depths as the source of a sustainable drinking water supply. In all monitoring piezometers, As was found consistently within a narrow band of oscillation probably due to seasonal effects. Hydrogeochemically, high-As shallow groundwaters derived from black sands are associated with elevated DOC, HCO3, Fe, NH4-N and PO4-P and with a relatively low concentration of Mn and SO4. Opposite to this, shallow aquifers composed of red and off-white sediments providing As-safe groundwater are associated with low DOC, HCO3, Fe, NH4-N and PO4-P and relatively higher Mn and SO4. Groundwaters sampled from intermediate deep and deep piezometers which were found to be low in As, are characterized by much lower DOC, HCO3, NH4-N and PO4-P compared to the shallow aquifers. Shallow groundwaters are mostly Ca-Mg-HCO3 type and intermediate deep and deep aquifers’ groundwaters are mostly Na-Ca-Mg-Cl-HCO3 to Na-Cl-HCO3 type.

    A sediment color tool was also developed on the basis of local driller’s color perception of sediments (Black, White, Off-white and Red), As concentration of tubewell waters and respective color of aquifer sediments. A total of 2240 sediment samples were collected at intervals of 1.5 m up to a depth of 100 m from all 15 nest locations. All samples were assigned with a Munsell color and code, which eventually led to identify 60 color varieties. The process continued in order to narrow the color choices to four as perceived and used by the local drillers for identification of the targeted As-safe aquifers. Munsell color codes assigned to these sediments render them distinctive from each other which reduces the risk for misinterpretation of the sediment colors. During the process of color grouping, a participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. In addition to the monitoring wells installed in the piezometer nests, results from 87 other existing drinking water supply tubewells were also considered for this study. A total of 39 wells installed in red sands at shallow depths producing As-safe water providing strong evidence that red sediments are associated with As-safe water. Average and median values were found to be less than the WHO guideline value of 10 μg/L. Observations for off-white sediments were also quite similar. Targeting off-white sands could be limited due to uncertainty of proper identification of color, specifically when day-light is a factor. Elevated Mn in red and off-white sands is a concern in the safe water issue and emphasizes the necessity of a better understanding of the health impact of Mn. White sediments in shallow aquifers are relatively uncommon and seemed to be less important for well installations. Arsenic concentrations in more than 90% of the shallow wells installed in black sands are high with an average of 239 μg/L from 66 wells installed in black sediments. It is thereby recommended that black sands in shallow aquifers must be avoided. This sediment color tool shows the potential for enhancing the ability of local tubewell drillers for the installation of As-safe shallow drinking water tubewells.

    Considering the long-term goal of the drinking water safety plan to provide As-safe and low-Mn drinking water supply, this study also pioneered hydrogeological exploration of the intermediate deep aquifer (IDA) through drilling up to a depth of 120 m. Clusters of tubewells installed through site optimization around the monitoring piezometer showed a similar hydrochemical buffer and proved IDA as a potential source for As-safe and low-Mn groundwater. Bangladesh drinking water standard for As (50 µg/L) was exceeded in only 3 wells (1%) and 240 wells (99%) were found to be safe. More than 91% (n=222) of the wells were found to comply with the WHO guideline value of 10 µg/L. For Mn, 89% (n=217) of the wells show the concentration within or below the previous WHO guideline value of 0.4 mg/L, with a mean and median value of 0.18 and 0.07 mg/L respectively. The aquifer explored in the Matlab area shows a clear pattern of low As and low Mn. The availability of similar sand aquifers elsewhere at this depth range could be a new horizon for tapping safe drinking water at about half the cost of deep tubewell installation.

    All findings made this study a comprehensive approach and strategy for replication towards As mitigation and scaling-up safe water access in other areas of Bangladesh and elsewhere having a similar hydrogeological environment.

  • 25. Hudson, J. A.
    et al.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Demonstration of coupled models and their validation against experiment: The current phase DECOVALEX 20152013Inngår i: Rock Characterisation, Modelling and Engineering Design Methods - Proceedings of the 3rd ISRM SINOROCK 2013 Symposium, Taylor & Francis Group, 2013, s. 391-396Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The DECOVALEX Project (DEmonstration of COupled models and their VALidation against EXperiment) has been operating since 1992 with the objective of developing thermo-hydro-mechanical coupled computer modelling in order to provide the necessary support for the design of underground radioactive waste repositories. The Project consists of Benchmark Tests which are synthetic models for comparison of different research teams' computer modelling results (verification), and Test Cases which are simulations of actual physical cases to establish whether the modelling does in fact represent the rock reality (validation). An international consortium of Funding Organisations supports the DECOVALEX work, currently the following ten Funding Organisations: BGR/UFZ (Germany), CAS (China), DOE (USA), ENSI (Switzerland), IRSN (France), JAEA (Japan), KAERI (Korea), NDA (UK), NRC (USA) and RAWRA (Czech Republic). In this paper, we explain the 2011-2015 DECOVALEX modelling tasks which cover the range of argillaceous, sedimentary and crystalline rocks.

  • 26. Kataoka, Ryuho
    et al.
    Fukuda, Yoko
    Miyoshi, Yoshizumi
    Miyahara, Hiroko
    Itoya, Satoru
    Ebihara, Yusuke
    Hampton, Donald
    Dahlgren, Hanna
    KTH, Skolan för elektro- och systemteknik (EES).
    Whiter, Daniel
    Ivchenko, Nickolay
    KTH, Skolan för elektro- och systemteknik (EES).
    Compound auroral micromorphology: ground-based high-speed imaging2015Inngår i: EARTH PLANETS AND SPACE, ISSN 1880-5981, Vol. 67, artikkel-id 23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Auroral microphysics still remains partly unexplored. Cutting-edge ground-based optical observations using scientific complementary metal-oxide semiconductor (sCMOS) cameras recently enabled us to observe the fine-scale morphology of bright aurora at magnetic zenith for a variety of rapidly varying features for long uninterrupted periods. We report two interesting examples of combinations of fine-scale rapidly varying auroral features as observed by the sCMOS cameras installed at Poker Flat Research Range (PFRR), Alaska, in February 2014. The first example shows that flickering rays and pulsating modulation simultaneously appeared at the middle of a surge in the pre-midnight sector. The second example shows localized flickering aurora associated with growing eddies at the poleward edge of an arc in the midnight sector.

  • 27. Khotyaintsev, Y. V.
    et al.
    Lindqvist, Per-Arne
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cully, C. M.
    Eriksson, A. I.
    Andre, M.
    In-flight calibration of double-probe DC electric field measurements on Cluster2014Inngår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 4, nr 1, s. 85-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of DC and AC electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the EFW instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.

  • 28.
    Larsson, Stefan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Ahnberg, Helen
    Ignat, Razvan
    Baker, Sadek
    Discussion of "Numerical Modeling of Geotextile-Reinforced Embankments over Deep Cement Mixed Columns Incorporating Strain-Softening Behavior of Columns" by N. N. S. Yapage, D. S. Liyanapathirana, H. G. Poulos, R. B. Kelly, and C. J. Leo2015Inngår i: International Journal of Geomechanics, ISSN 1532-3641, E-ISSN 1943-5622, Vol. 15, nr 4, artikkel-id 07014008Artikkel i tidsskrift (Fagfellevurdert)
  • 29. Li, Peijun
    et al.
    Hu, Hongtao
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik (stängd 20110301).
    Guo, Jiancong
    Segmentation of high-resolution multispectral image based on extended morphological profiles2007Inngår i: IGARSS 2007: 2007 IEEE International Geoscience and Remote Sensing Symposium, IEEE , 2007, s. 1481-1484Konferansepaper (Fagfellevurdert)
    Abstract [en]

    High-resolution multispectral remote sensing image provides both spectral and structural information about land cover/land use types. In segmentation of such complex image scenes with obvious texture, the efficient image segmentation is required. In this study, a method for high resolution image segmentation based on the extended morphological profiles is proposed. First, fundamental morphological vector operations (erosion and dilation) are defined by the extension, taking into account the spatial and spectral information in simultaneous fashion. Theoretical definitions of extended morphological operations are used in the formal definition of the concept of extended morphological profiles, which is constructed based on the repeated use of openings and closings by reconstruction with a structuring element (SE) of increasing size. Then, the morphological multiscale characteristic (MMC) of each pixel is gained through the derivative of the extended morphological profiles (DEMP). A modified method was proposed to obtain the right morphological characteristics of the pixel, which will be used for the final segmentation results. Finally, a simple region merging method based on the distance between two centroids of the neighboring regions was adopted to further improve the segmentation result. The proposed approach is applied to high-resolution QuickBird multispectral images from urban, agricultural and forest areas for evaluation and comparison with existing methods, in terms of qualitative visual inspection and quantitative criteria. The proposed method demonstrated better performance than the classical morphological segmentation approaches.

  • 30.
    Lindström, Kati
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Filosofi och teknikhistoria, Historiska studier av teknik, vetenskap och miljö.
    Koff, Tiiu
    Tallinn University.
    Antropotseen: Inimeste ajastu2015Inngår i: Horisont, ISSN 0134-2282, Vol. 5, s. 26-34Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 31.
    Liu, Longcheng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Analysis of fluid flow and solute transport through a single fracture with variable apertures intersecting a canister: Comparison between fractal and Gaussian fractures2006Inngår i: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 31, nr 14-okt, s. 634-639Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Canisters with spent nuclear fuel will be deposited in fractured crystalline rock in the Swedish concept for a final repository. The fractures intersect the canister holes at different angles and they have variable apertures and therefore locally varying flowrates. Our previous model with fractures with a constant aperture and a 90 degrees intersection angle is now extended to arbitrary intersection angles and stochastically variable apertures. It is shown that the previous basic model can be simply amended to account for these effects. More importantly, it has been found that the distributions of the volumetric and the equivalent flow rates are all close to the Normal for both fractal and Gaussian fractures, with the mean of the distribution of the volumetric flow rate being determined solely by the hydraulic aperture, and that of the equivalent flow rate being determined by the mechanical aperture. Moreover, the standard deviation of the volumetric flow rates of the many realizations increases with increasing roughness and spatial correlation length of the aperture field, and so does that of the equivalent flow rates. Thus, two simple statistical relations can be developed to describe the stochastic properties of fluid flow and solute transport through a single fracture with spatially variable apertures. This obviates, then, the need to simulate each fracture that intersects a canister in great detail, and allows the use of complex fractures also in very large fracture network models used in performance assessment.

  • 32. Mao, Bo
    et al.
    Ban, Yifang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik.
    Harrie, Lars
    Lund University.
    Real-time visualization of 3D city models at street-level based on visual saliency2015Inngår i: Science China Earth Sciences, ISSN 1674-7313, Vol. 58, nr 3, s. 448-461Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Street-level visualization is an important application of 3D city models. Challenges to street-level visualization include the cluttering of buildings due to fine detail and visualization performance. In this paper, a novel method is proposed for street-level visualization based on visual saliency evaluation. The basic idea of the method is to preserve these salient buildings in a scene while removing those that are non-salient. The method can be divided into pre-processing procedures and real-time visualization. The first step in pre-processing is to convert 3D building models at higher Levels of Detail (LoDs) into LoD1 models with simplified ground plans. Then, a number of index viewpoints are created along the streets; these indices refer to both the position and the direction of each street site. A visual saliency value is computed for each building, with respect to the index site, based on a visual difference between the original model and the generalized model. We calculate and evaluate three methods for visual saliency: local difference, global difference and minimum projection area. The real-time visualization process begins by mapping the observer to its closest indices. The street view is then generated based on the building information stored in those indexes. A user study shows that the local visual saliency method performs better than do the global visual saliency, area and image-based methods and that the framework proposed in this paper may improve the performance of 3D visualization.

  • 33. Mayer, M.
    et al.
    Krat, S.
    Van Renterghem, W.
    Baron-Wiechec, A.
    Brezinsek, S.
    Bykov, Igor
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Coad, P.
    Gasparyan, Y.
    Heinola, K.
    Likonen, J.
    Pisarev, A.
    Ruset, C.
    De Saint-Aubin, G.
    Widdowson, A.
    Erosion and deposition in the JET divertor during the first ILW campaign2016Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, artikkel-id 014051Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Erosion and deposition were studied in the JET divertor during the first JET ITER-like wall campaign 2011 to 2012 using marker tiles. An almost complete poloidal section consisting of tiles 0, 1, 3, 4, 6, 7, 8 was studied. The data from divertor tile surfaces were completed by the analysis of samples from remote divertor areas and from the inner wall cladding. The total mass of material deposited in the divertor decreased by a factor of 4-9 compared to the deposition of carbon during all-carbon JET operation before 2010. Deposits in 2011 to 2012 consist mainly of beryllium with 5-20 at.% of carbon and oxygen, respectively, and small amounts of Ni, Cr, Fe and W. This decrease of material deposition in the divertor is accompanied by a decrease of total deuterium retention inside the JET vessel by a factor of 10 to 20. The detailed erosion/deposition pattern in the divertor with the ITER-like wall configuration shows rigorous changes compared to the pattern with the all-carbon JET configuration.

  • 34.
    Min, Ki Bok
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Jing, Lanru
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Stephansson, O
    Determining the equivalent permeability tensor for fractured rock masses using a stochastic REV approach: Method and application to the field data from Sellafield, UK2004Inngår i: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 12, nr 5, s. 497-510Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A numerical procedure to determine the equivalent permeability tensor of a fractured rock is presented, using a stochastic REV (Representative Elementary Volume) concept that uses multiple realizations of stochastic DFN (Discrete Fracture Network) models. Ten square DFN models are generated using the Monte Carlo simulations of the fracture system based on the data obtained from a site characterization program at Sellafield, Cumbria, UK. Smaller models with varying sizes of from 0.25 mx0.25 m to 10 mx10 m are extracted from the generated DFN models and are used as two-dimensional geometrical models for calculation of equivalent permeability tensor. The DFN models are also rotated in 30degrees intervals to evaluate the tensor characteristics of calculated directional permeability. Results show that the variance of the calculated permeability values decreases significantly as the side lengths of the DFN models increase, which justifies the existence of a REV. The REV side length found in this analysis is about 5 m and 8 m with 20% and 10% acceptable variations, respectively. The calculated directional permeability values at the REV size have tensor characteristic that is confirmed by a close approximation of an ellipse in a polar plot of the reciprocal of square roots of the directional permeability.

  • 35.
    Min, Ki-Bok
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    Rutqvist, J.
    Tsang, C. -F
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    A Block-Scale Stress-Permeability Relationship of a Fractured Rock Determined by Numerical Experiments2004Inngår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications, Elsevier, 2004, nr C, s. 269-274Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    We present the stress induced permeability change in a fractured rock with special focuses on 1) fracture closure/opening process, 2) anisotropic stress conditions, and 3) fracture dilation. In order to overcome the limitations from the experimental study on a single fracture or analytical study on orthogonal and/or persistent fracture models, realistic Discrete Fracture Network (DFN) models were used as a geometrical basis. A series of numerical experiments on fluid flow are conducted under different stress boundary conditions for calculation of equivalent permeability. From the analysis on the realistic DFN model, this paper demonstrates the decrease of permeability with the fracture normal closure, increased anisotropy in permeability with anisotropic stress and increase of permeability and significant channelling effect due to fracture dilation. It is shown that block-scale permeability change in fractured rock depends not only on stress magnitude but also on stress orientation and differential stresses.

  • 36. Nakamura, R.
    et al.
    Karlsson, Tomas
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Hamrin, M.
    Nilsson, H.
    Marghitu, O.
    Amm, O.
    Bunescu, C.
    Constantinescu, V.
    Frey, H. U.
    Keiling, A.
    Semeter, J.
    Sorbalo, E.
    Vogt, J.
    Forsyth, C.
    Kubyshkina, M. V.
    Low- altitude electron acceleration due to multiple flow bursts in themagnetotail2014Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, nr 3, s. 777-784Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    At 10:00 UT on 25 February 2008, Cluster 1 spacecraft crossed the near-midnight auroral zone, at about 2R(E) altitude, while two of the Time History of Events and Macroscale Interactions During Substorms (THEMIS) spacecraft, THD and THE, observed multiple flow bursts on the near-conjugate plasma sheet field lines. The flow shear pattern at THEMIS was consistent with the vortical motion at duskside of a localized flow channel. Coinciding in time with the flow bursts, Cluster 1 observed bursts of counterstreaming electrons with mostly low energies (441eV), accompanied by short time scale (<5s) magnetic field disturbances embedded in flow-associated field-aligned current systems. This conjugate event not only confirms the idea that the plasma sheet flows are the driver of the kinetic Alfven waves accelerating the low-energy electrons but is a unique observation of disturbances in the high-altitude auroral region relevant to the multiple plasma sheet flows. Key Points <list list-type="bulleted"> <list-item id="grl51326-li-0001">First observation of multiple flow signatures on near-conjugate flux tubes <list-item id="grl51326-li-0002">Low-energy electron profile suggests Alfvenic acceleration due to fast flow <list-item id="grl51326-li-0003">Multiple flow bursts are obtained to extend over large radial distance in tail

  • 37.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Some aspects of release and transport of gases in deep granitic rocks: possible implications for nuclear waste repositories2013Inngår i: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 21, nr 8, s. 1701-1716Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radon, radium and helium data from three sites in granitic rock in Sweden (Forsmark and Laxemar) and Finland (Olkiluoto) from depths greater than 1,000 m were interpreted by a model that describes how daughter nuclides, including helium from uranium and thorium decay, escape from minerals, enter the pore water in the rock matrix and diffuse to the seeping water in the fractures in the rock. The radium concentrations are on the order of < 30 Bq/l of water that has recently infiltrated and then emerged from the rock. Radon concentrations are mostly several orders of magnitude larger. The model predicts values in the same range. The fair agreement between model results, field data and laboratory data over a scale spanning micrometres over meters to kilometres, and time scales of days to millions of years, shows that the micropores of the rock matrix are connected even at depths down to and beyond a kilometre. Molecular diffusion in the matrix pore water is a key migration mechanism. Laboratory-derived sorption coefficients for radium are of the same magnitude as those needed in the modelling of the in situ data to give good agreement.

  • 38.
    Nissen, Anna
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Numerisk analys, NA. University of Bergen, Norway.
    Keilegavlen, Eirik
    Sandve, Tor Harald
    Berre, Inga
    Nordbotten, Jan Martin
    Heterogeneity preserving upscaling for heat transport in fractured geothermal reservoirs2018Inngår i: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 22, nr 2, s. 451-467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In simulation of fluid injection in fractured geothermal reservoirs, the characteristics of the physical processes are severely affected by the local occurence of connected fractures. To resolve these structurally dominated processes, there is a need to develop discretization strategies that also limit computational effort. In this paper, we present an upscaling methodology for geothermal heat transport with fractures represented explicitly in the computational grid. The heat transport is modeled by an advection-conduction equation for the temperature, and solved on a highly irregular coarse grid that preserves the fracture heterogeneity. The upscaling is based on different strategies for the advective term and the conductive term. The coarse scale advective term is constructed from sums of fine scale fluxes, whereas the coarse scale conductive term is constructed based on numerically computed basis functions. The method naturally incorporates the coupling between solution variables in the matrix and in the fractures, respectively, via the discretization. In this way, explicit transfer terms that couple fracture and matrix solution variables are avoided. Numerical results show that the upscaling methodology performs well, in particular for large upscaling ratios, and that it is applicable also to highly complex fracture networks.

  • 39.
    Noorian-Bidgoli, Majid
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Effects of loading conditions on strength and deformability of fractured rocks - A numerical study2014Inngår i: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium, Taylor & Francis Group, 2014, s. 365-368Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a systematic numerical study to evaluate the effects of two different loading conditions, namely the axial stress and axial velocity, on testing compressive strength and deformability properties of fractured rocks. The UDEC code was used to perform a series of numerical tests on two-dimensional fracture network (DFN) models, in the similar ways for the uniaxial and biaxial laboratory testing on intact rock samples. The obtained stresses and strains from these numerical experiments were used to estimate equivalent directional Young's modulus and fit the Mohr-Coulomb and Hoek-Brown failure criteria, represented by equivalent material properties defining these two criteria. The numerical results show that stress-strain behaviors changes by loading conditions with higher averaged axial stress under axial velocity condition than that under axial stress condition. Therefore, the effects of different loading conditions should be carefully considered for designing and interpretation of results for in-situ experiments with large volumes of fractured rocks.

  • 40.
    Partamies, Noora
    et al.
    Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway. artamies, Noora.
    Blomgren, Karl
    KTH. Department of Electronic and Electrical Engineering, University of Bath, Bath, United Kingdom.
    Heino, Erkka
    Ivchenkoo, Nickolay
    KTH.
    Borovsky, Joseph E.
    Hedberg, Hanna
    KTH. FOI Swedish Defence Research Agency, Stockholm, Sweden.
    Patch Size Evolution During Pulsating Aurora2019Inngår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, nr 6, s. 4725-4738Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report both decreasing and increasing trends in the patch sizes during pulsating aurora events. About 150 pulsating auroral events over the Fennoscandian Lapland have been successfully analyzed for their average patch size, total patch area, and number of patches as a function of event time, typically 1-2 hr. An automatic routine has been developed to detect patches in the all-sky camera images. In addition to events with decreasing and increasing average patch size evolution over the course of the pulsating aurora, events with no size trends and events with intermittently increasing and decreasing patch size trends were also found. In this study, we have analyzed a subset of events for which the average and total patch size systematically increase or decrease. The events with increasing patch size trend do not experience a decrease in the peak emission height, which was previously associated with the behavior of pulsating aurora precipitation. Furthermore, the events with increasing patch sizes have shorter lifetimes and twice as many substorm-injected energetic electrons at geosynchronous orbit as the events with decreasing patch sizes. Half of the events with increasing patch sizes occur during substorm expansion phases, while a majority (64%) of the ones with decreasing patch sizes take place during the recovery phase. These findings suggest that the visual appearance of pulsating aurora may be used as an indication of the pulsating aurora energy deposition to the atmosphere.

  • 41. Pikovsky, Y. I.
    et al.
    Glasko, M. P.
    Kutcherov, Vladimir G.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Gubkin Russian State University of Oil and Gas, Russia.
    The block structure and the presence of oil and gas in the Siljan impact crater2017Inngår i: Russian Geology and Geophysics, ISSN 1068-7971, E-ISSN 1878-030X, Vol. 58, nr 2, s. 199-205Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Morphostructural modeling of the block structure of a part of the Scandinavian crystalline shield has shown that the ring structure of the Siljan Ring impact crater is located in the center of a morphostructural node, a ring structure with a diameter of 300 km, marking a large disjunctive tectonic knot. The crater area consists of a central block, which is a granite massif, and of a surrounding mobile morphostructural boundary forming a wide small-block ring depression zone, where oil and gas shows have been revealed within the crater. This zone is regarded as the most promising one for search for migration channels and atypical shows of hydrocarbons.

  • 42.
    Prästings, Anders
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Müller, Rasmus
    Larsson, Stefan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    The observational method applied to a high embankment founded on sulphide clay2014Inngår i: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 181, s. 112-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Since its introduction, Eurocode 7 has acknowledged the observational method as a valid design approach for geotechnical structures. The observational method is defined in five paragraphs. Although several case studies have concluded that the observational method is useful, the method is still sparsely used. This study compares the actual implementation of the observational method in the Veda embankment project according to the definitions given in Eurocode 7. The outcome of the observational method as a design approach, and the major deviations compared to the definitions in Eurocode 7 are discussed. It is concluded that the design of a multi-staged embankment, where the building process is governed by consolidation in the subsoil, can only partly be adapted to the observational method as defined in Eurocode 7. Furthermore, when this is the case, the possibility of combining "design by calculations" and the observational method is discussed.

  • 43.
    Saadati, Mahdi
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Forquin, P.
    Weddfelt, K.
    Larsson, Per Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Hild, Francois
    LMT Cachan, Paris, France.
    Granite rock fragmentation at percussive drilling - experimental and numerical investigation2014Inngår i: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 38, nr 8, s. 828-843Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study is to numerically model the fracture system at percussive drilling. Because of the complex behavior of rock materials, a continuum approach is employed relying upon a plasticity model with yield surface locus as a quadratic function of the mean pressure in the principal stress space coupled with an anisotropic damage model. In particular, Bohus granite rock is investigated, and the material parameters are defined based on previous experiments. This includes different tests such as direct tension and compression, three-point bending, and quasi-oedometric tests to investigate the material behavior at both tension and confined compression stress states. The equation of motion is discretized using a finite element approach, and the explicit time integration method is employed. Edge-on impact tests are performed, and the results are used to validate the numerical model. The percussive drilling problem is then modeled in 3D, and the bit-rock interaction is considered using contact mechanics. The fracture mechanism in the rock and the bit penetration- resisting force response are realistically captured by the numerical model.

  • 44.
    Sjoberg, Lars E.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Quasigeoid-to-geoid determination by EGM082012Inngår i: Earth Science Informatics, ISSN 1865-0473, Vol. 5, nr 2, s. 87-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method to estimate the difference between quasigeoid and geoid heights globally from the Earth Gravitational Model EGM08 and a related topographic model. The numerical computations with the standard topographic density of 2.67 g/cm(3) show that the maximum and minimum of the separations are estimated to 5.47 m and -0.11 m on the Tibet plateau and in the Indian Ocean, respectively. These estimates do not consider possible topographic density variations, which result in topographic bias changes proportional to the topographic elevation squared. Assuming such density changes of 10% from the standard value, the separation may change up to 5 dm.

  • 45. Sookhak, A.
    et al.
    Baghbanan, A.
    Hashemalhosseini, H.
    Bagheri, Mehdi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    UDEC simulation of block stability analysis around a large cavern2010Inngår i: Analysis Of Discontinuous Deformation: New Developments And Applications, Research Publishing Services, 2010, s. 445-452Konferansepaper (Fagfellevurdert)
  • 46.
    Spross, Johan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Stille, Håkan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    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 Rock2018Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, nr 8, s. 2427-2431Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 47.
    Tafesse, Solomon
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Robison Fernlund, Joanne M.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Sun, Wenjuan
    Bergholm, Fredrik
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Evaluation of image analysis methods used for quantification of particle angularity2013Inngår i: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091, Vol. 60, nr 4, s. 1100-1110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Angularity is an important parameter in the characterization of particle morphology that is used to interpret the transport history of particles in sedimentary deposits. In the past, visual classification using silhouette charts was widely used to determine particle angularity, but this approach is subjective and time-consuming. With advances in modern image analysis techniques and low-cost software packages, it is possible to rapidly quantify particle angularity more objectively than using visual classification methods. This study re-examines the performance of three existing image analysis methods and one new image analysis procedure, applied to six rock and sediment samples that were visually different in angularity. To facilitate comparison between the angularity results, measurements were reduced to rankings for each aggregate sample. These results show that the four image analysis methods rank the angularity of the samples differently, and that none rank the mean angularity index in the same order as the angularity ranking using visual classification. Therefore, further research is needed to develop an image analysis method that can quantify the angularity of sedimentary particles more precisely.

  • 48. Tavassoli, Z
    et al.
    Zimmerman, Robert W.
    Department of Earth Science and Engineering, Imperial College, London, United Kingdom.
    Blunt, M.J
    Analysis of counter-current imbibition with gravity in weakly water-wet systems2005Inngår i: Journal of Petroleum Science and Engineering, ISSN 0920-4105, E-ISSN 1873-4715, Vol. 48, nr 1-2, s. 94-104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Counter-current imbibition in one dimension is analyzed, in which a wetting phase (water) displaces a non-wetting phase against gravity. An approximate analytical approach is used to derive an expression for the saturation profile in the case where the mobility of the displaced phase at the inlet is finite. This approach is applicable to waterflooding in hydrocarbon reservoirs, flow in geothermal systems, or the displacement of non-aqueous phase liquid (NAPL) or air by water. Solutions are developed for both gravity-dominated and capillary-dominated cases. In the capillary-dominated limit the predicted recoveries compare very well with experimental data from the literature, over all time scales. The use of this expression for field-scale dual-porosity modeling of flow in fractured systems is briefly discussed.

  • 49. Tenzer, Robert
    et al.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Gladkikh, Vladislav
    Signature of the upper mantle density structure in the refined gravity data2012Inngår i: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 16, nr 4, s. 975-986Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The gravitational signal of the upper mantle density structures is investigated in the refined gravity data which are corrected for the gravitational contributions of the crust density structures and the Moho geometry. The gravimetric forward modeling is applied to compute these refined gravity data globally on a 1 x 1 arcdeg grid using the global geopotential model (EGM2008), the global topographic/bathymetric model (DTM2006.0) including the ice-thickness data, and the global crustal model (CRUST2.0). The characteristics of the upper mantle density structures are further analyzed in association with the Moho parameters (i.e., Moho depths and density contrast). The 1 x 1 arcdeg global data of the Moho parameters are estimated by applying the combined least-squares approach based on solving Moritz's generalization of the Vening-Meinesz inverse problem of isostasy. The refined gravity data exhibit mainly the mantle lithosphere structures attributed to the global mantle convection. A significant correlation found over oceans between the refined gravity data and the Moho density contrast is explained by the increasing density of the oceanic lithosphere with age. Despite the lithosphere structures attributed to the global mantle convection are confirmed also in the refined gravity data over continents, the significant correlation between the refined gravity data and the Moho parameters is in this case absent. Instead, the significant proportion of lateral variations of the Moho density contrast within the continental lithosphere is attributed to the depth-dependant density changes due to pressure and thermal gradient.

  • 50. Tenzer, Robert
    et al.
    Bagherbandi, Mohammad
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Vajda, Peter
    Global model of the upper mantle lateral density structure based on combining seismic and isostatic models2013Inngår i: Geosciences Journal, ISSN 1226-4806, Vol. 17, nr 1, s. 65-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compile the global model of the upper mantle lateral density structure with a 2x2 arc-deg spatial resolution using the values of the crust-mantle density contrast estimated relative to the adopted crust density model. The combined least-squares approach based on solving Moritz's generalization of the Vening-Meinesz inverse problem of isostasy is facilitated to estimate the crust-mantle density contrast. The global geopotential model (EGM08), the global topographic/bathymetric model (DTM2006.0) including ice-thickness data, and the global crustal model (CRUST2.0) are used to compute the isostatic gravity anomalies. The estimated upper mantle densities globally vary between 2751 and 3635 kg/m(3). The minima correspond with locations of the divergent oceanic tectonic plate boundaries (along the mid-oceanic ridges). The maxima are found along the convergent tectonic plate boundaries in the Andes and Himalayas (extending under the Tibetan Plateau). A comparison of the estimated upper mantle densities with the CRUST2.0 data shows a relatively good agreement between these two models within the continental lithosphere with the differences typically within +/- 100 kg/m(3). Much larger discrepancies found within the oceanic lithosphere are explained by the overestimated values of the CRUST2.0 upper mantle densities. Our result shows a prevailing pattern of increasing densities with the age of oceanic lithosphere which is associated with the global mantle convection process.

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