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  • 1.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Distributed thermal response tests: New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.

    Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.

    A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.

    The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.

    Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.

    Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.

    At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.

    Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.

    Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.

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    José Acuña - Doctoral Thesis
  • 2. Al-Yaarubi, A. H.
    et al.
    Pain, C. C.
    Grattoni, C. A.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Navier-Stokes Simulations of Fluid Flow Through a Rock Fracture2013In: Dynamic Fluids and Transport Through in Fractured Rock, American Geophysical Union (AGU), 2013, p. 55-64Chapter in book (Other academic)
    Abstract [en]

    A surface profilometer was used to measure fracture profiles every 10 microns over the surfaces of a replica of a fracture in a red Permian sandstone, to within an accuracy of a few microns. These surface data were used as input to two finite element codes that solve the Navier-Stokes equations and the Reynolds equation, respectively. Numerical simulations of flow through these measured aperture fields were carried out at different values of the mean aperture, corresponding to different values of the relative roughness. Flow experiments were also conducted in casts of two regions of the fracture. At low Reynolds numbers, the Navier-Stokes simulations yielded transmissivities for the two fracture regions that were closer to the experimental values than were the values predicted by the lubrication model. In general, the lubrication model overestimated the transmissivity by an amount that varied as a function of the relative roughness, defined as the standard deviation of the aperture divided by the mean aperture. The initial deviations from linearity, for Reynolds numbers in the range 1-10, were consistent with the "weak inertia" model developed by Mei and Auriault for porous media, and with the results obtained computationally by Skjetne et al in 1999 on a two-dimensional self-affine fracture. In the regime 10 < Re < 40, both the computed and measured transmissivities could be fit very well to a Forchheimer-type equation, in which the additional pressure drop varies quadratically with the Reynolds number.

  • 3.
    Andersson, Johan Vium
    KTH, School of Architecture and the Built Environment (ABE).
    Undifferenced GPS for Deformation Monitoring2006Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    This thesis contains the development of a deformation monitoring software based on undifferenced GPS observations. Software like this can be used in alarm systems placed in areas where the earth is unstable. Systems like this can be used in areas where people are in risk of getting hurt, like in earthquake zones or in land slide areas, but they can also be useful when monitoring the movements in buildings, bridges and other artefacts.

    The main hypotheses that are tested are whether it is possible to detect deformations with undifferenced observations and if it is possible to reach the same accuracy in this mode as when working in a traditional mode where the observations are differenced.

    The development of a deformation monitoring software based on undifferenced GPS observations is presented. A complete mathematical model is given as well as implementation details. The software is developed in Matlab together with a GPS observation simulator. The simulator is mainly used for debugging purposes.

    The developed software is tested with both simulated and real observations. Results from tests with simulated observations show that it is possible to detect deformations in the order of a few millimetres with the software. Calculations with real observations give the same results. Further, the result from calculations in static mode indicates that the commercial software and the undifferenced software diverge a few millimetres, which probably depends on different implementations of the tropospheric corrections. In kinematic mode the standard deviation is about 1 millimetre larger in the undifferenced mode than in the double differenced mode. An initial test with different observation weighting procedures indicates that there is a lot of potential to improve the result by applying correct weights to the observations. This is one of the aims in the future work within this project.

    This thesis are sponsored by the Swedish Research Council for Enviroment, Agricultural Sciences and Spatial Planning, FORMAS within the framework “Monitoring of construction and detection of movements by GPS ref no. 2002-1257"

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    FULLTEXT01
  • 4.
    Bakyayita, Grace Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Makerere Univ, Dept Civil & Environm Engn, Kampala, Uganda..
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, R. N.
    Makerere Univ, Dept Civil & Environm Engn, Kampala, Uganda..
    Assessment of Levels, Speciation, and Toxicity of Trace Metal Contaminants in Selected Shallow Groundwater Sources, Surface Runoff, Wastewater, and Surface Water from Designated Streams in Lake Victoria Basin, Uganda2019In: Journal of Environmental and Public health, ISSN 1687-9805, E-ISSN 1687-9813, article id 6734017Article in journal (Refereed)
    Abstract [en]

    The levels, speciation of elements, and toxicity of selected trace metals as well as other parameters in selected surface water, shallow groundwater sources, landfill leachate, and associated surface runoff in the Lake Victoria basin, Uganda, were studied. The WHO guidelines, Ugandan standards, Canadian guidelines and Swedish EPA were used for assessment. The shallow groundwater was acidic with pH values below 6.5. The pH, dissolved organic carbon, flouride, and sulphate levels for all springs were below the guideline values although 52.8% was contaminated with nitrates while 39% was contaminated with chloride ions. Some surface water samples had levels of major elements, such as iron, chromium, aluminium, and manganese, above the guideline values. Speciation studies showed that 74% of the metal ions was bound to dissolved organic matter in surface water, whereas in landfill leachates, the dominant ionic species was metal hydroxides or fulvic acid bound. Risk analysis based on the Swedish EPA showed varied risks of negative effects in 30%-76% of the sample sites ranging from high to increased risk in surface water, whereas the results from modelling sorption data using the Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+, and Pb2+ in 15.3%-30.8% surface water samples and 8.3%-62.5% groundwater samples.

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    fulltext
  • 5.
    Bazargan, Mohsen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Almqvist, Bjarne
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hieronymus, Christoph F.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Piazolo, Sandra
    School of Earth and Environment, University of Leeds, Leeds, United Kingdom.
    Bahadour Motra, Hem
    Department of Geosciences, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
    Broumand, Pooyan
    Department of Civil Engineering, Shiraz University, Shiraz, Iran.
    Schmiedel, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Numerical, predictive and experimental study on elastic wave propagation in crystalline rocks2021Conference paper (Other academic)
    Abstract [en]

    Calculating anisotropy and better understanding this physical effect is one of the main challenges in geophysics, whether in the size of the field or micro scale. one of the very common methods of calculating seismic anisotropy is to take into account the bulk properties of the material, in a micro-scale, this is based on the average value of Crystallographic preferred orientation measurements by using, for example, Scanning Electron Microscopy to operate - Electron backscatter diffraction method.

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    fulltext
  • 6.
    Birkholzer, Jens T.
    et al.
    Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Bond, Alexander E.
    Quintessa Ltd, Birchwood, England.
    Hudson, John A.
    Imperial Coll London, London, England.
    Jing, Lanru
    KTH Royal Inst Technol, Stockholm, Sweden.
    Stephansson, Ove
    GFZ Helmholtz Ctr Geosci, Potsdam, Germany.
    25 years of DECOVALEX - Scientific advances and lessons learned from an international research collaboration in coupled subsurface processes2019In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 122, article id 103995Article, review/survey (Refereed)
    Abstract [en]

    This paper provides an overview of an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. The creation of the international DECOVALEX Project, now running for over 25 years, was initially motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. Later it was realized that these processes also play a critical role in other subsurface engineering activities, such as storage of CO2, exploration of enhanced geothermal systems, and unconventional oil and gas production through hydraulic fracturing. Research teams from radioactive waste management organizations, national research institutes, regulatory agencies, universities, as well as industry and consulting groups have participated in the DECOVALEX Project, providing a wide range of perspectives and solutions to these complex problems. Analysis and comparative modeling of state-of-the-art field and laboratory experiments has been at the core of the collaborative work, with an increasing focus on characterizing uncertainty and blind prediction of experimental results. Over these 25 years, many of the major advances in this field of research have been made through DECOVALEX, as evidenced by three books, seven journal special issues, and a good number of seminal papers that have emerged from the DECOVALEX modeling work. Examples of specific research advances will be presented in this paper to illustrate the significant impact of DECOVALEX on the current state-of-the-art of understanding and modeling coupled THMC processes. These examples range from the modeling of large-scale in situ heater tests representing mock-ups of nuclear waste disposal tunnels, to studies of fluid flow and chemical-mechanical coupling in heterogeneous fractures, and to the numerical analysis of controlled-injection meso-scale fault slip experiments.

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    FULLTEXT01
  • 7.
    Bjureland, William
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Uttorkning av lera: Orsaker och följder2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
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    FULLTEXT01
  • 8.
    Bjureland, William
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Uttorkning av lera: Orsaker och följder2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When building a house or similar the stress on the ground increases and deformations can arise. The deformations create a foundation that the building is not constructed for and damages on the building arise. The increased stress on the ground can be derived back to the building, but it is possible that the increased stress may well derive from different sources such as other buildings or trees.      

     

    The building is an older property, built in the late 19th century alternatively early 20th century, and is today used for rental housing and has suffered severe damages due to subsidence. The goal of the thesis is to find possible causes for these subsidences.

     

    The thesis was executed as a combination between literature- and casestudie.

     

    After careful studies it has been found that a probable cause for these subsidences is trees. Through field- and lab studies it has been found that the trees has effected the ground through there accumulation of water. This has caused the soil to dry up and subsidence’s has probably arisen through the decrease in pore pressure due to the disappearing of water. This, however, needs to be proven by further studies of pore pressures in the area.

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    FULLTEXT01
  • 9. Boano, F.
    et al.
    Harvey, J. W.
    Marion, A.
    Packman, A. I.
    Revelli, R.
    Ridolfi, L.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
    Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications2014In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 52, no 4, p. 603-679Article, review/survey (Refereed)
    Abstract [en]

    Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

  • 10.
    Breton, Simon-Philippe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Shen, W.Z.
    Technical University of Denmark, Energivej, Building 414, 2800 Kgs. Lyngby, Denmark.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Validation of the actuator disc and actuator line techniques for yawed rotor flows using the New MEXICO experimental data2017Conference paper (Refereed)
    Abstract [en]

    Experimental data acquired in the New MEXICO experiment on a yawed 4.5m diameter rotor model turbine are used here to validate the actuator line (AL) and actuator disc (AD) models implemented in the Large Eddy Simulation code EllipSys3D in terms of loadingand velocity field. Even without modelling the geometry of the hub and nacelle, the AL and AD models produce similar results that are generally in good agreement with the experimental data under the various configurations considered. As expected, the AL model does better at capturing the induction effects from the individual blade tip vortices, while the AD model can reproduce the averaged features of the flow. The importance of using high quality airfoil data (including 3D corrections) as well as a fine grid resolution is highlighted by the results obtained. Overall, it is found that both models can satisfactorily predict the 3D velocity field and blade loading of the New MEXICO rotor under yawed inflow.

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    fulltext
  • 11.
    Bäckström, Ann
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    A study of impact fracturing and electric resistivity related to the Lockne impact structure, Sweden2005In: Impact Tectonics / [ed] Koeberl C; Henkel H, 2005, p. 389-404Conference paper (Refereed)
    Abstract [en]

    The fracture frequency and the electric resistivity of outcrops of crystalline basement rocks at the Lockne meteorite impact site have been studied in order to investigate the extent and radial changes of impact induced fracturing. By measuring the electric resistivity and the fracture frequency at the same outcrops, the effect of fracturing on the electric properties of the rock is estimated and correlated with the fracture frequency. A negative linear correlation between the Log of fracture frequency and the Log of electric resistivity was found.

    It was also found that the fracture frequency decreases in a transition zone over a distance of about 1100 m across the southern margin of the impact structure. A similar set of measurements was made across the suggested northern limit of the structure, but no change was detected. This implies that the outer limit of the Tandsbyn Breccia is further to the north. The studied area is, therefore, not likely to be the. margin of the structure.

  • 12.
    Bäckström, Ann
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Rock damage caused by underground excavation and meteorite impacts2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The intent of this thesis is to contribute to the understanding of the origin of fractures in rock. The man-made fracturing from engineering activities in crystalline rock as well as the fracturing induced by the natural process of meteorite impacts is studied by means of various characterization methods. In contrast to engineering induced rock fracturing, where the goal usually is to minimize rock damage, meteorite impacts cause abundant fracturing in the surrounding bedrock. In a rock mass the interactions of fractures on the microscopic scale (mm-cm scale) influence fractures on the mesoscopic scale (dm-m scale) as well as the interaction of the mesocopic fractures influencing fractures on the macroscopic scale (m-km scale). Thus, among several methods used on different scales, two characterization tools have been developed further. This investigation ranges from the investigation of micro-fracturing in ultra-brittle rock on laboratory scale to the remote sensing of fractures in large scale structures, such as meteorite impacts. On the microscopic scale, the role of fractures pre-existing to the laboratory testing is observed to affect the development of new fractures. On the mesoscopic scale, the evaluation of the geometric information from 3D-laser scanning has been further developed for the characterisation of fractures from tunnelling and to evaluate the efficiency of the tunnel blasting technique in crystalline rock. By combining information on: i) the overbreak and underbreak; ii) the orientation and visibility of blasting drillholes and; iii) the natural and blasting fractures in three dimensions; a analysis of the rock mass can be made. This analysis of the rock mass is much deeper than usually obtained in rock engineering for site characterization in relation to the blasting technique can be obtained based on the new data acquisition. Finally, the estimation of fracturing in and around two meteorite impact structures has been used to reach a deeper understanding of the relation between fracture, their water content and the electric properties of the rock mass. A correlation between electric resistivity and fracture frequency in highly fractured crystalline rock has been developed and applied to potential impact crater structures. The results presented in this thesis enables more accurate modelling of rock fractures, both supporting rock engineering design and interpretation of meteorite impact phenomena.

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    FULLTEXT01
  • 13.
    Bäckström, Ann
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Cosgrove, John W.
    Department of Earth Science and Engineering, Imperial College, London.
    Hudson, John A.
    Department of Earth Science and Engineering, Imperial College, London.
    Interpretation of the development of induced cracks within a pre-cracked rock microstructure and the similarities with the geometry of larger-scale geological fracturesIn: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201Article in journal (Other academic)
  • 14.
    Bäckström, Ann
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Feng, Quanhong
    Berg Bygg Konsult AB.
    Lanaro, Flavio
    Berg Bygg Konsult AB.
    Excavation Damage Zone (EDZ) at the TASQ tunnel (Äspö, Sweden): Quantification of blasting effects on the geological settings by 3D-laser-scanningIn: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917Article in journal (Other academic)
  • 15.
    Bäckström, Ann
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Feng, Quanhong
    Berg Bygg Konsult AB.
    Lanaro, Flavio
    Berg Bygg Konsult AB.
    Christiansson, Rolf
    Swedish Nuclear Fuel and Waste Management Co.
    Evaluation of the Excavation Damage Zone (EDZ) by using 3-D laser scanning technique2006In: The 4th Asian Rock Mechanics Symposium, Singapore, 8 - 10 November 2006, 2006Conference paper (Other academic)
  • 16.
    Bäckström, Ann
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Koyama, Tomofumi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    et al.,
    Numerical modelling of uniaxial compressive failure of granite with and without saline porewater2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 7, p. 1126-1142Article in journal (Refereed)
    Abstract [en]

    It is important for rock engineering design to be able to validate numerical simulations, i.e. to check that they adequately represent the rock reality. In this paper, the capability and validity of four numerical models is assessed through the simulation of an apparently simple case: the complete process of microstructural breakdown during the uniaxial compressive failure of intact crystalline rock. In addition to comparing the capabilities of the four models, the results generated by each model were compared with the experimentally determined complete stress-strain curves for the Swedish Avro granite for different porewater conditions. In this way, it has been possible to audit the models' adequacy for this particular simulation task. It was found that although the models had common features, they were each idiosyncratically different and required considerable expertise to match the actual stress-strain curves (which did not monotonically increase in axial strain)-indicating that, for more complex simulations, both adequate modelling and appropriate validation are not going to be an easy task. The work was conducted within the framework of the international 2004-2007 DEmonstration of COupled models and their VALidation against EXperiments with emphasis on Thermo Hydro Mechanic and Chemical aspects (DECOVALEX-THMC) phase on coupled modelling extended to include chemical effects and with application to the excavation damaged zone (EDZ) in crystalline rock.

  • 17. Bäckström, Ann
    et al.
    Lanaro, Flavio
    Berg Bygg Konsult AB.
    Christiansson, Rolf
    Swedish Nuclear Fuel and Waste Management Co.
    Coupled chemical-mechanical behaviour: the influence of salinity on the uniaxial compressive strength of the Smålands granite, Sweden2006In: Proc. of the 2nd International Conference on Coupled T-H-MC Processes in Geo-Systems: Fundamentals, Modeling, Experiments and Applications, Geo-Proc 2006, 2006, p. 437-443Conference paper (Refereed)
  • 18. Chan, T.
    et al.
    Christiansson, R.
    Boulton, G. S.
    Ericsson, L. O.
    Hartikainen, J.
    Jensen, M. R.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stanchell, F. W.
    Vistrand, P.
    Wallroth, T.
    DECOVALEX III BMT3/BENCHPAR WP4: The thermo-hydro-mechanical responses to a glacial cycle and their potential implications for deep geological disposal of nuclear fuel waste in a fractured crystalline rock mass2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 805-827Article in journal (Refereed)
    Abstract [en]

    A number of studies related to past and on-going deep repository performance assessments have identified glaciation/ deglaciation as major future events in the next few hundred thousand years capable of causing significant impact on the long term performance of the repository system. Benchmark Test 3 (BMT3) of the international DECOVALEX III project has been designed to provide an illustrative example that explores the mechanical and hydraulic response of a fractured crystalline rock mass to a period of glaciation. The primary purpose of this numerical study is to investigate whether transient events associated with a glacial cycle could significantly influence the performance of a deep geological repository in a crystalline Shield setting. A conceptual site-scale (tens of kilometres) hydro-mechanical (HM) model was assembled based primarily on site-specific litho-structural, hydrogeological and geomechanical data from the Whiteshell Research Area in the Canadian Shield, with simplification and generalization. Continental glaciological modelling of the Laurentide ice sheet through the last glacial cycle lasting approximately 100,000 years suggests that this site was glaciated at about 60 ka and between about 22.5 and 11 ka before present with maximum ice sheet thickness reaching 2500 m and maximum basal water pressure head reaching 2000m. The ice-sheet/drainage model was scaled down to generate spatially and temporally variable hydraulic and mechanical glaciated surface boundary conditions for site-scale subsurface HM modelling and permafrost modelling. Under extreme periglacial conditions permafrost was able to develop down to the assumed 500-m repository horizon. Two- and three-dimensional coupled HM finite-element simulations indicate: during ice-sheet advance there is rapid rise in hydraulic head, high transient hydraulic gradients and high groundwater velocities 2-3 orders of magnitude higher than under nonglacial conditions; surface water recharges deeper than under nonglacial conditions; upon ice-sheet retreat, the gradients reverse; fracture zone network geometry, interconnectivity and hydraulic properties significantly influence flow domain response; residual elevated heads are preserved for 10,000s in the low-diffusivity rock; and no hydraulic jacking or shear failure occurs at depth. It was found that transient coupled modelling is necessary to capture the essence of glacial effects on Performance Assessment. Model dimensionality also significantly affects simulated results.

  • 19. Darcel, C.
    et al.
    Davy, P.
    Le Goc, R.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Rock mass effective properties from a DFN approach2018In: 2nd International Discrete Fracture Network Engineering Conference, DFNE 2018, American Rock Mechanics Association (ARMA) , 2018Conference paper (Refereed)
    Abstract [en]

    Rock mass mechanical properties are strongly controlled by the fractures they contain. Their determination raises strong issues for many rock-engineering applications, like underground repository safety assessment, support design, slope stability or mine caving. To compensate the impossibility to perform direct in-situ measures of these properties at appropriate scales, empirical approaches classically aim to determine the rock mass equivalent properties from simple indicators. Here we propose an approach based on the complete representation of the rock mass as an intact rock with a population of discrete fractures through it (the Discrete Fracture Network). The core of the approach is the definition, at the rock mass scale, of the deformation induced by each fracture locally, including the fracture mechanical and geometrical parameters, the remote stress conditions and the interactions with the rest of the fracture population. Depending on the conditions, the resulting scaling and anisotropic effects can be critical. The method is applied to the Forsmark site in Sweden. We show that two main scaling regimes occur, where the shift from the one to the other is controlled by the ratio between the intact rock modulus, the typical fracture stiffness and the DFN size distribution. Beyond the scaling issue we quantify the resulting level of anisotropy. 

  • 20.
    Dargahi, Bijan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Setegn, Shimelis Gebriye
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Combined 3D Hydrodynamic and Watershed Modelling of Lake Tana, Ethiopia2011In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 398, no 1-2, p. 44-64Article in journal (Refereed)
    Abstract [en]

     The growing high demand for lake Tana water portends a disturbing future. The main objective of this paper is to make a contribution to the development of a sustainable use of the water of Lake Tana. A fully three-dimensional hydrodynamic model was combined with a watershed model and together, these models were successfully validated for the year 2006. The flow structure is characterized by large recirculation and secondary flow regions. Secondary flows are induced by hydrodynamic instabilities occurring at the interfaces of layers with a velocity gradient and the interaction with the irregularities of the bed. The weak stratification process in Lake Tana is characterized by a classic summer profile, which is more pronounced during January-February. Mixing processes in the lake are controlled by wind, the mixing energy induced by both river inflows and the lake outlet, and convective mixing due to the negative buoyancy. An alarming fall of the water levels in Lake Tana was found in response to the planned water withdrawal. The long flushing time (19 months) will not allow a fast decay of contaminated materials released into the lake. The flow structure will not be significantly modified by the planned water withdrawal but the flushing time will decrease. The hydrodynamics of Lake Tana resemble a closed system similar to a shallow reservoir with an overflow type outlet. The implication is that the lake is vulnerable to changes in external conditions and sustainable use of the water resource of the lake will require awareness of this vulnerability. The combined watershed and hydrodynamic models would be effective tools to achieve this awareness. It is also necessary to address the impact of climate change on the fate of the lake. These are all difficult challenges that need to be addressed to safeguard the sensitive eco-system of the area.

  • 21.
    De Simone, Silvia
    et al.
    UMR 6118, Univ Rennes, CNRS, Géosciences Rennes, 35000, Rennes, France; Spanish National Research Council (IDAEA–CSIC), 08034, Barcelona, Spain.
    Darcel, Caroline
    Itasca Consultants SAS, Rennes, France.
    Kasani, Hossein A.
    Nuclear Waste Management Organization (NWMO), Toronto, ON, Canada.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Swedish Nuclear Fuel and Waste Management Company (SKB), Solna, Sweden.
    Davy, Philippe
    UMR 6118, Univ Rennes, CNRS, Géosciences Rennes, 35000, Rennes, France.
    Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach2023In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 56, no 12, p. 8907-8925Article in journal (Refereed)
    Abstract [en]

    A quantitative and analytical approach is adopted to estimate two important parameters for coupled hydro-mechanical analysis at the scale of a fractured rock mass, namely the equivalent Biot effective stress coefficient α¯ and Skempton pore pressure coefficient B¯ . We derive formal expressions that estimate the two equivalent poroelastic coefficients from the properties of both the porous intact rock and the discrete fracture network, which includes fractures with different orientation, size, and mechanical properties. The coefficients are equivalent in the sense that they allow effectively predicting the volumetric deformation of the fluid-saturated fractured rock under an applied load in drained and undrained conditions. The formal expressions are validated against results from fully coupled hydro-mechanical simulations on systems with explicit representation of deformable fractures and rock blocks. We find that the coefficients are highly anisotropic as they largely vary with fracture orientations with respect to the applied stress tensor. For a given set of fracture and rock properties, B¯ increases with the ratio of normal to average stress undergone by the fractures, while the opposite occurs for α¯ . Additionally, both α¯ and B¯ increase with fracture density, which directly impacts the deformation caused by a load in undrained conditions. Because the effective stress variation is proportional to the applied load by (1 - α¯ B¯) , a factor that partly compensates for the decrease in equivalent rock stiffness caused by the fractures, a fully saturated fractured rock may deform less than an intact rock in undrained conditions, while the opposite occurs in dry conditions.

  • 22.
    Dessirier, Benoit
    et al.
    Stockholm University, Stockholm, Sweden.
    Sharma, Mrityunjai
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pedersen, Jonas
    AFRY, Stockholm, Sweden.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Channel Network Modeling of Flow and Transport in Fractured Rock at the Äspö HRL: Data‐Worth Analysis for Model Development, Calibration and Prediction2023In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 59, no 5, article id e2022WR033816Article in journal (Refereed)
    Abstract [en]

    Performance assessment of nuclear waste disposal in deep crystalline bedrock demands a thorough understanding of the related flow and transport processes. Uncertainties may arise both from the selection of the conceptual model as well as the estimation of the related model parameters. Discrete fracture network (DFN) models are widely used for such modeling while channel network models (CNM) provide an alternative representation, the latter focusing on the fact that flow and transport in deep fractured media often are dominated by a small number of long preferential flow paths. This study applies the principle of channel networks, implemented in the Pychan3d simulator, to analyze the hydraulic and tracer transport behavior in a 450-m-deep fractured granite system at the Äspö Hard Rock Laboratory in Sweden, where extensive site characterization data, including hydraulic and tracer test data are available. Semi-automated calibration of channel conductances to field characterization data (flow rates, drawdowns, and tracer recoveries) is performed using PEST algorithm. It was observed that an optimal CNM connectivity map for channel conductance calibration can only be developed by jointly fitting flow rates, drawdowns and tracer mass recovery values. Results from data-calibrated CNM when compared to a corresponding calibrated DFN model shows that the CNM calibrates and adapts better than a DFN model with uniform fracture surfaces. This comparative study shows the differences and uncertainties between two models as well as examines the implications of using them for long term model predictions.

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  • 23.
    Dessirier, Benoît
    et al.
    Stockholms universitet, Institutionen för naturgeografi.
    Frampton, Andrew
    Stockholms universitet, Institutionen för naturgeografi.
    Fransson, A.
    Jarsjö, Jerker
    Stockholms universitet, Institutionen för naturgeografi.
    Modeling early in situ wetting of a compacted bentonite buffer installed in low permeable crystalline bedrock2016In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, no 8, p. 6207-6221Article in journal (Refereed)
    Abstract [en]

    The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the postclosure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Aspo Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state-of-the-art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de-saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open-hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions.

  • 24.
    Do, Tan Manh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Department of Civil Engineering, University of Mining and Geology, Hanoi, Vietnam.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jia, Qi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Tailings fluidization under cyclic triaxial loading – a laboratory study2022In: Geomechanics and Engineering, ISSN 2005-307X, E-ISSN 2092-6219, Vol. 29, no 5, p. 497-508Article in journal (Refereed)
    Abstract [en]

    Tailings fluidization (i.e., tailings behave as being fluidized) under cyclic loading is one concern during the construction of tailings dams, especially in the shallow tailings layers. The primary goal of this study is to evaluate the responses of tailings under cyclic loadings and the tailings potential for fluidization. A series of cyclic triaxial undrained and drained tests were performed on medium and dense tailings samples under various cyclic stress ratios (CSR). The results indicated that axial strain and excess pore water pressure accumulated over time due to cyclic loading. However, the accumulations were dependent on CSR values, densities, and drainage conditions. The fluidization potential analysis in this study was then evaluated based on the obtained cyclic axial strain and excess pore water pressure. As a result, tailings samples were stable (unfluidized) under small CSR values, and the critical CSR values, where the tailings fluidized, varied depending on the density of tailings samples. Tailings fluidization is triggered as cyclic stress ratios reach critical values. In this study, the critical CSR values were found to be 0.15 and 0.40 for medium and dense samples, respectively.

  • 25.
    Doolaeghe, D.
    et al.
    Univ Rennes, CNRS, Geosci Rennes, UMR 6118, 263 Ave Gen Leclerc, F-35042 Rennes, France..
    Darcel, C.
    Itasca Consultants SAS, 29 Ave Joannes Masset, F-69009 Lyon, France..
    Selroos, Jan-Olof
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Swedish Nucl Fuel & Waste Management Co SKB, Box 3091,Evenemangsgatan 13, S-16903 Solna, Sweden..
    Davy, P.
    Univ Rennes, CNRS, Geosci Rennes, UMR 6118, 263 Ave Gen Leclerc, F-35042 Rennes, France..
    Controls on fracture openness and reactivation in Forsmark, Sweden2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 6686Article in journal (Refereed)
    Abstract [en]

    In crystalline bedrock, the open fraction of the fracture network constitutes the main pathways for fluids. Many observations point out that the state of stress influences the open fraction, likely indicating recent reactivation. But how this occurs is still unresolved. We analyse the conditions for fracture reactivation from fracture data collected in the uppermost 1 km of bedrock in Forsmark, Sweden. The open fraction is mainly correlated to the stress acting normally on the fracture but even away from critical failure, leading us to analyse the potential fluid pressure required for reactivation, P-c. We observe that 100% of the fractures are open when P-c is hydrostatic, and the ratio decreases exponentially to a plateau of similar to 17% when P-c is lithostatic and above. Exceptions are the oldest fractures, having a low open fraction independent of P-c. We suggest that these results reflect past pressure build-ups, potentially related to recent glaciations, and developing only if the preexisting open fraction is large enough.

  • 26.
    Elvin, Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Dangré, Markus
    Spetsbärförmåga hos betongpålar slagna i friktionsjord2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to build a database for point-bearing piles in dense noncohesive soil, predominantly moraine. Further, the database was analysed and areas with difficult geotechnical conditions was identified.

    The database includes for point-bearing piles driven to refusal in moraine. Piles with mainly shaft friction have been excluded. Only concrete piles have been included. Geographically the database covers almost all geotechnical conditions of Sweden. The total amount of piling projects is 110 and the total amount of piles is 600.

    For contractors, foundation work is usually connected with a lot of uncertainty and risk, concerning the estimating of time and cost. During the design stage of foundation construction the database can be a useful tool to estimate suitable loads on the piles.

    The data was analysed further with different statistical method. Possible reasons for low bearing capacity, in some projects, have also been investigated.

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  • 27.
    Eshagh, Mehdi
    University West, Department of Engineering Science, Division of Mathematics, Computer and Surveying Engineering.
    Satellite gravimetry and the solid Earth: mathematical foundations2020Book (Other academic)
    Abstract [en]

    Satellite gravimetry and the solid Earth: mathematical foundations presents the theories behind satellite gravimetry data and their connections to solid Earth. It covers the theory of satellite gravimetry and data analysis, presenting it in a way that is accessible across geophysical disciplines. Through a discussion of satellite measurements and the mathematical concepts behind them, the book shows how various satellite measurements, such as satellite orbit, acceleration, vector gravimetry, gravity gradiometry, and integral energy methods can contribute to an understanding of the gravity field and solid Earth geophysics. Bridging the gap between geodesy and geophysics, this book is a valuable resource for researchers and students studying gravity, gravimetry and a variety of geophysical and Earth Science fields.

  • 28.
    Estevez-Ventosa, Xian
    et al.
    Univ Vigo, Dept Nat Resources & Environm Engn, CINTECX, GESSMin Grp, Campus Lagoas, Vigo 36310, Pontevedra, Spain..
    Castro-Filgueira, Uxia
    Univ Vigo, Dept Nat Resources & Environm Engn, CINTECX, GESSMin Grp, Campus Lagoas, Vigo 36310, Pontevedra, Spain..
    Gonzalez-Fernandez, Manuel A.
    Univ Vigo, Dept Nat Resources & Environm Engn, CINTECX, GESSMin Grp, Campus Lagoas, Vigo 36310, Pontevedra, Spain..
    Garcia-Bastante, Fernando
    Univ Vigo, Dept Nat Resources & Environm Engn, CINTECX, GESSMin Grp, Campus Lagoas, Vigo 36310, Pontevedra, Spain..
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Swedish Nucl Fuel & Waste Management Co SKB, Evenemangsgatan 13,Box 3091, SE-16903 Stockholm, Sweden..
    Alejano, Leandro R.
    Univ Vigo, Dept Nat Resources & Environm Engn, CINTECX, GESSMin Grp, Campus Lagoas, Vigo 36310, Pontevedra, Spain..
    Scale effects on triaxial peak and residual strength of granite and preliminary PFC3D models2022In: Geomechanics and Engineering, ISSN 2005-307X, E-ISSN 2092-6219, Vol. 31, no 5, p. 461-476Article in journal (Refereed)
    Abstract [en]

    Research studies on the scale effect on triaxial strength of intact rocks are scarce, being more common those in uniaxial strength. In this paper, the authors present and briefly interpret the peak and residual strength trends on a series of triaxial tests on different size specimens (30 mm to 84 mm diameter) of an intact granitic rock at confinements ranging from 0 to 15 MPa. Peak strength tends to grow from smaller to standard-size samples (54 mm) and then diminishes for larger values at low confinement. However, a slight change in strength is observed at higher confinements. Residual strength is observed to be much less size-dependent. Additionally, this study introduces preliminary modelling approaches of these laboratory observations with the help of three-dimensional particle flow code (PFC3D) simulations based on bonded particle models (BPM). Based on previous studies, two modelling approaches have been followed. In the first one, the maximum and minimum particle diameter (Dmax and Dmin) are kept constant irrespective of the sample size, whereas in the second one, the resolution (number of particles within the sample or phi v) was kept constant. Neither of these approaches properly represent the observations in actual laboratory tests, even if both of them show some interesting capabilities reported in this document. Eventually, some suggestions are provided to proceed towards improving modelling approaches to represent observed scale effects.

  • 29.
    Farcas, Florentina
    Linköping University, Department of Computer and Information Science, GIS - Geographical Information Science Group.
    Road Traffic Noise - A study of region Skåne, Sweden2008Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Since the first car appeared, the pollution on the roads became an issue, which is still mainly unsolved. Too many people complain about traffic noise. Various methods have been developed that aimed at minimizing the noise pollution and improving the environment.

    This thesis presents the problems posed by noise pollution, covers the background of noise pollution and its effects on human health. Another important part of the thesis covers the method of noise calculation which applies in specific Nordic countries.

    The main goal of the thesis is to present maps of noise levels on roads for region Skåne in Sweden. Because the regulation and the limits for noise levels are different for different countries, I could find various calculators for traffic noise. Australia, England, USA have the noise level calculators open for public. Another professional calculator, SoundPlan, is a program that can perform a very accurate calculation for traffic noise but only for small areas. Because of this disadvantage, the request for my thesis was to provide a program which can calculate traffic noise level for wide areas. As a master student specialist in GIS (Geographic Information System) it was natural to develop the traffic noise calculator with available GIS tools.

    The software system to calculate the traffic noise maps was implemented in ArcMap 9.1, a GIS program which allows creation of tools, according to a mathematical description of noise calculator. The mathematical description is based on the Nordic Prediction method, a document which set up requirements for prediction of road traffic noise. ArcMap 9.1 allows the development of extensions in different programming languages. The tools implemented in this thesis are written in Visual Basic. The thesis work implements several tools for calculating noise levels, starting from the basic traffic noise level and introducing additional noise corrections to perform more accurate noise calculation. The additional corrections could be added because I had access to additional data regarding buildings and population location. The available population data from Lund gave me the opportunity to create a tool which performs population exposure to noise in this region.

     

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  • 30.
    Fernlund, Joanne M. Robison
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Magnusson, Mimmi K.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Total analysis of till using resistivity and 3D image analysisArticle in journal (Other academic)
  • 31.
    Fernlund, Joanne
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Magnusson, Mimmi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Lithological analysis of multiple size fractions of tillArticle in journal (Other academic)
  • 32.
    Figueiredo, Bruno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Itasca Consultants AB, Lulea, Sweden.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley Natl Lab, Berkeley, CA USA.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    The Influence of Coupled Thermomechanical Processes on the Pressure and Temperature due to Cold Water Injection into Multiple Fracture Zones in Deep Rock Formation2020In: Geofluids, ISSN 1468-8115, E-ISSN 1468-8123, Vol. 2020, article id 8947258Article in journal (Refereed)
    Abstract [en]

    A technique to produce geothermal energy from deep rock formations at elevated temperatures consists of drilling two parallel deep boreholes, the second of which is directed so as to intersect a series of fractures produced by hydraulic fracturing in the first borehole. Then, the first borehole is used for injection of cold water and the second used to produce water that has been heated by the deep rock formation. Some very useful analytical solutions have been applied for a quick estimate of the water outlet temperature and injection/production pressures in this enhanced geothermal system (EGS), but they do not take into account the influence of thermomechanical and hydromechanical effects on the time evolutions of the pressure and temperature. This paper provided help for the engineering design of the EGS based on these analytical solutions, by evaluating the separate influences of the thermal (T), hydromechanical (HM), thermo-hydro-mechanical (THM) effects on the fluid pore pressure and temperature. A thermo-hydro-mechanical (THM) model was developed to simulate the heat extraction from multiple preexisting fracture zones in the hot rock formation, by considering permeability changes due to the injection pressure as a function of changes in the mean effective stress. It was found that the thermal effects (without coupling with mechanical effects) led to a decrease of the transmissivity of the fracture zones and a consequent increase in the injection pressure, by a maximum factor of 2. When the temperature is constant, the influence of the hydromechanical effects on the fluid pore pressure was found to be negligible, because in such scenario, the variation of the mean effective stress was 3 MPa, which was associated with a maximum increase in the initial permeability of the fracture zone only by a factor of 1.2. Thermo-hydro-mechanical effects led to a maximum increase in the permeability of the fracture zones of approximately 10 times the initial value, which was associated with a decrease in the fluid pore pressure by a maximum factor of 1.25 and 2, when hydrological and thermohydrological effects were considered, respectively. Changes in temperature were found not to be affected significantly by the thermomechanical and hydromechanical effects, but by the flow rate in the fracture zones. A sensitivity analysis was conducted to study the influence of the number, the initial permeability, the elastic modulus and the residual porosity of the fracture zones, and the elastic modulus of the confining intact rock, on the simulation results. The results were found to be the most sensitive to the number and the initial permeability of the fracture zones.

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  • 33.
    Fälth, Billy
    et al.
    Clay Technol AB, Lund, Sweden..
    Grigull, Susanne
    SKB Swedish Nucl Fuel & Waste Management Co, Solna, Sweden..
    Gåling, Jenny
    SKB Swedish Nucl Fuel & Waste Management Co, Solna, Sweden..
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. SKB Swedish Nucl Fuel & Waste Management Co, Solna, Sweden.
    Wagner, Frederic
    SKB Swedish Nucl Fuel & Waste Management Co, Solna, Sweden..
    Comment on "Modelling coseismic displacements of fracture systems in crystalline rock during large earthquakes: Implications for the safety of nuclear waste repositories" as published by Lei and Loew (2021) in IJRMMS, 138, 1045902022In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 150, article id 105013Article in journal (Refereed)
  • 34.
    Ghaderi, Abdolvahed
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Shahri, Abbas Abbaszadeh
    Islamic Azad Univ, Fac Civil Engn, Roudehen Branch, Tehran, Iran..
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A visualized hybrid intelligent model to delineate Swedish fine-grained soil layers using clay sensitivity2022In: Catena (Cremlingen. Print), ISSN 0341-8162, E-ISSN 1872-6887, Vol. 214, p. 106289-, article id 106289Article in journal (Refereed)
    Abstract [en]

    In the current paper, a hybrid model was developed to generate 3D delineated soil horizons using clay sensitivity (St) with 1 m depth intervals in a landslide prone area in the southwest of Sweden. A hybridizing process was carried out using generalized feed forward neural network (GFFN) incorporated with genetic algorithm (GA). The model was conducted by means of seven variables consisting of the geographical coordinates and piezocone penetration test data (CPTu). The output of model (St) as a description of the effect of soil disturbance on shear strength plays a significant role in landslides in Sweden and thus can be applied for site-specific evaluation. Therefore, the use of St-based models to delineate soil layers can be a cost-effective solution to improve geoengineering design practices and assist in the reduction of related environmental risks, such as catastrophic landslide events or excavation failures. Evaluated model performance based on different applied soil classifications showed 4.38% improvement in the predictability level of GFFN-GA compared to optimum GFFN. Accordingly, delineated soil layers were evaluated using different criteria including previous landslides as well as supplementary geophysical and geotechnical investigations. The results show that the adopted hybrid GFFN-GA is an efficient tool that can potentially be applied to delineate soil horizons for the prediction of future events.

  • 35.
    Giron, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Effekter på grund- och ytvattenförhållandenkring svenska oljelager i bergrum2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Det saknas i dagsläget en samlad redovisning av erfarenheter rörande påverkan pågrundvattennivåer samt ytvattennivåer och flöden vid grundvattenbortledning från Svenskaberganläggningar. Det saknas även en utvärdering av olika prognosmetoders tillämpbarhetbaserad på prognoser kontra utfall.Det finns ett brett spektrum av metoder för att prognostisera effekterna, från relativt enklabedömningar baserat på vattenbalanser, analytiska lösningar, till avancerade numeriskamodelleringsverktyg. Vilken eller vilka metoder som används i det enskilda fallet styrs idealtav faktorer som exempelvis anläggningstyp, hydrogeologiska förhållanden och dekonsekvenser som grundvattenbortledning potentiellt kan ge upphov till i omgivningen. Ensamling av branscherfarenheter skulle således kunna leda till en effektivisering samt enkostnadssänkning vid framtida bergbyggen.Det saknas även en kartläggning av befintliga berganläggningar i norden. Det finns mängdermed bergrum, tunnlar och gruvor i norden men i dagsläget finns ingen sammanställning avdessa. En sammanställning som redovisar relevant information om området somberganläggningen ligger i som t.ex. berggrund, jordtyp och potentiell grundvattenbildningskulle även det kunna effektivisera arbetet och minska framtida kostnader då en jämförelsesnabbt kan göras med befintliga anläggningar.En analys av ett enklare prognosverktyg som uppskattar uppfyllnadstiden för olikaberganläggningar endast baserat läckvattenmängd och berganläggningens totala volym visadeatt dessa enklare metoder ofta underskattar uppfyllnadstiden.En metod för teoretisk beräkning av påverkansavståd och kvot mellan grundvattenbildning tilljord och berg undersöktes och påvisades gå att använda i områden med tätt berg, dock medstor osäkerhet.

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  • 36.
    Grigat, Felix
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. ONERA.
    Optimizing the architecture of the Salammbô-EnKF data assimilation tool for radiation belt modeling2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 37.
    Gunnvard, Per
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Garcia, Nelson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jia, Qi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Monitoring of a timber pile-supported road embankment2022In: Proceedings Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields / [ed] Inge Hoff, Helge Mork, Rabbira Garba Saba, London: CRC Press, 2022, Vol. 2, p. 337-347Conference paper (Refereed)
    Abstract [en]

    Timber piling allows for a solution with lower carbon footprint than concrete or steel piling, yet there exist few well-documented cases of modern timber piled embankments. In this paper, field measurements on a geosynthetic-reinforced timber pile-supported road embankment are reported and evaluated. The monitored road embankment is a section of a newly reconstructed semi-motorway in northern Sweden. The embankment was constructed on 8 m long untreated timber piles with 1.1 m spacing in a triangular pattern, without pile caps. On top of that, a 1.7 m high embankment was constructed, reinforced by two layers of biaxial geogrids. A long-term monitoring program is being carried out from when the semi-motorway was reconstructed. This study presents results from the first year of monitoring. The measurements include the load on the pile heads and subsoil, geogrid strain, pore water pressures, and settlements. The measurements show the development of arching over time, the interlocking of geogrid and embankment material, the subsoil consolidation, etc. The results of the monitoring are compared with results of analytical models from recommendations and codes.

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  • 38.
    Henkel, Herbert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Piazolo, Sandra
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    A deep rock laboratory in the Dellen impact crater2010In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 132, no 1, p. 45-54Article in journal (Refereed)
    Abstract [en]

    The Deep Rock Lab is a platform to establish a comprehensive subsurface bedrock characterization approach, by integrating site characterization techniques applied from different disciplines of geo-mechanics, geochemistry, hydrogeology, structural geology, lithology and geophysics, with consideration of the effects of coupled geological processes of importance for the understanding of groundwater renewal, continental shield deformations, engineering issues related to geological disposal of nuclear waste and CO2, and geothermal energy retrieval in crystalline rocks. The approach will focus on the physics and chemistry of crystalline rocks and groundwater with down-the-hole measurements of relevant variables, using and developing more efficient geo-scientific site investigation techniques for deep boreholes at a chosen site, and develop more advanced down-the-hole measurements and numerical modelling methods with more advanced inversion algorithms to help integrate data interpretations and object representations. The goal is to develop this platform into a long-term research facility that can be readily used by the scientific community for both subsurface fundamental and engineering-oriented research. Such a platform will be especially important for the education of PhD students for generations to come. The integrated drilling and research facility is suggested to be located at the Dellen site. This site has an impact crater with a large range of expected physical property changes with depth, complex and multiple thermal processes that have affected the bedrock, a favorable infrastructure and local supporting activities, and a large body of existing geo-scientific data.

  • 39. Hollesen, J.
    et al.
    Elberling, B.
    Jansson, Per-Erik
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles2011In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 65, no 2, p. 258-268Article in journal (Refereed)
    Abstract [en]

    Subsurface heat production from oxidation of pyrite is an important process that may increase subsurface temperatures within coal waste rock piles and increase the release of acid mine drainage, AMD. Waste rock piles in the Arctic are especially vulnerable to changes in subsurface temperatures as the release of AMD normally is limited by permafrost. Here we show that temperatures within a 20 year old heat-producing waste rock pile in Svalbard (78 degrees N) can be modelled by the one-dimensional heat and water flow model (CoupModel) with a new temperature-dependent heat-production module that includes both biological and chemical oxidation processes and heat source depletion over time. Inputs to the model are meteorological measurements, physical properties of the waste rock material and measured subsurface heat-production rates. Measured mean annual subsurface temperatures within the waste rock pile are up to 10 C higher than the mean annual air temperature of -5.8 degrees C. Subsurface temperatures are currently decreasing with 0.5 degrees C per year due to decreasing heat production, which can be modelled using an exponential decay function corresponding to a half-life period of pyrite oxidation of 7 years. Simulations further suggest that subsurface temperatures two years after construction of the pile may have been up to 34.0 degrees C higher than in 2009 and that the release of AMD may have been more than 20 times higher. Sensitivity simulations show that maximum temperatures in the pile would have been up to 30.5-32.5 degrees C lower and that the pile would have been frozen 12-27 years earlier if the pile had been initially saturated with water, constructed with a thickness half of the original or a combination of both. Simulation show that the pile thickness and waste rock pyrite content are important factors controlling the internal build up of heat leading to potential self-incineration. However, site specific measurements of temperature-dependent heat production as well as simulation results show that the heat produced from pyrite oxidation alone cannot cause such a temperature increase and that processes such as heat production from coal oxidation may be equally important. (C) 2010 Elsevier B.V. All rights reserved.

  • 40.
    Hu, Yingtao
    et al.
    Zhejiang Univ, MOE Key Lab Soft Soils & Geoenvironm Engn, Hangzhou 310058, Peoples R China.;Zhejiang Univ, Ctr Hypergrav Expt & Interdisciplinary Res, Hangzhou 310058, Peoples R China..
    Xu, Wenjie
    Zhejiang Univ, MOE Key Lab Soft Soils & Geoenvironm Engn, Hangzhou 310058, Peoples R China.;Zhejiang Univ, Ctr Hypergrav Expt & Interdisciplinary Res, Hangzhou 310058, Peoples R China..
    Zhan, Liangtong
    Zhejiang Univ, MOE Key Lab Soft Soils & Geoenvironm Engn, Hangzhou 310058, Peoples R China.;Zhejiang Univ, Ctr Hypergrav Expt & Interdisciplinary Res, Hangzhou 310058, Peoples R China..
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Chen, Yunmin
    Zhejiang Univ, MOE Key Lab Soft Soils & Geoenvironm Engn, Hangzhou 310058, Peoples R China.;Zhejiang Univ, Ctr Hypergrav Expt & Interdisciplinary Res, Hangzhou 310058, Peoples R China..
    Modeling of solute transport in a fracture-matrix system with a three-dimensional discrete fracture network2022In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 605, article id 127333Article in journal (Refereed)
    Abstract [en]

    Understanding the fluid flow and solute transport mechanisms in fractured rocks is essential for many geo-engineering applications. In this study, the fluid flow and solute transport in a fracture-matrix system with a three-dimensional (3-D) discrete fracture network (DFN) are modelled through an efficient numerical simulation workflow. The simulation approach is used to systematically investigate the effects of the rock matrix on the transport behaviors in a fracture-matrix system. The results show that the mass exchange between the DFN and the rock matrix can be accurately evaluated based on the conforming mesh at the interface between the fractures (using triangular elements) and the rock matrix (using tetrahedral elements). The complementary cumulative distribution function curves (CCDFs) for the physical processes that consider sorption and decay exhibit significant long tail characteristics, which suggests that the sorption and decay processes play an important role in retarding the migration of solutes in fractured rocks. It is also found that a larger matrix porosity enhances the mass exchange at the interface between the DFN and the rock matrix, which consequently promotes the matrix diffusion effects. The distribution of the concentration plumes in the matrix demonstrates in fracture-matrix systems with larger fracture densities could result in a better connection between the fracture networks and the larger interface (specific wetting) areas, which therefore, promotes the mass exchange. These findings are critical to understanding the migration behavior of radioactive nuclides in far field areas and for the deep geological disposal of nuclear waste.

  • 41.
    Hu, Yingtao
    et al.
    School of Engineering, Hangzhou City University, Hangzhou, 310015, China; Key Laboratory of Safe Construction and Intelligent Maintenance for Urban Shield Tunnels of Zhejiang Province, Hangzhou City University, Hangzhou, 310015, China; MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
    Xu, Wenjie
    MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Zhan, Liangtong
    MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
    Chen, Yunmin
    MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
    Wang, Ju
    CNNC Key Laboratory on Geological Disposal of High-level Radioactive Waste, Beijing Research Institute of Uranium Geology, Beijing, 100029, China.
    Dai, Zhenxue
    School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao, 266520, China.
    Evaluating the long-term barrier performance of fractured granite for nuclear waste disposal: Impact of fast water-conducting path2024In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 337, article id 107583Article in journal (Refereed)
    Abstract [en]

    Granite has relatively low-permeability and it has been considered as one of favorable geological formation for final disposal of high-level radioactive waste (HLW). However, the granite is often fractured and characterized as complex discrete fracture-matrix systems with considerable degree of uncertainties in its physical and geometrical properties. Prediction of nuclide migration in fractured granite at large spatial and long temporal scales is important for safety assessment of HLW disposal. In the present study, parametric studies are performed to evaluate the long-term barrier performance of fractured granite using the Beishan granite barrier as an illustration example. As the distance between the fast water-conducting path (FWCP) and the disposal pit decreased from 80 m to 0, the nuclides' arrival time (Tt) in the biosphere decreased from 9000 to approximately 2000 years when the effects of the fault and the FWCP are considered. The maximum nuclide concentration (Cmax) increases from 0.0019 (350,000 years) to 0.0121 mSv/y (150,000 years), exceeding the limit of 0.01 mSv/y. In addition, as the permeability (equivalent hydraulic aperture) of the FWCP increased from 5.0 × 10−5 m to 1.0 × 10−4 m, the Tt of Cs-135 further decreases to about 15,000 years, and the Cmax increases to 0.0256 mSv/y (100,000 years), suggesting a significant reduction in the long-term performance of the geological barrier. These findings are helpful for site assessment of HLW repositories built in fractured granite.

  • 42.
    Huber, Florian M.
    et al.
    Karlsruhe Inst Technol KIT, Inst Nucl Waste Disposal INE, POB 3640, D-76021 Karlsruhe, Germany..
    Leone, Debora
    Karlsruhe Inst Technol KIT, Inst Nucl Waste Disposal INE, POB 3640, D-76021 Karlsruhe, Germany..
    Trumm, Michael
    Karlsruhe Inst Technol KIT, Inst Nucl Waste Disposal INE, POB 3640, D-76021 Karlsruhe, Germany..
    Moreno, Luis
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Wenka, Achim
    Karlsruhe Inst Technol KIT, Inst Micro Proc Engn IMVT, Hermann Von Helmholtz Pl 1, DE-76344 Eggenstein Leopoldshafen, Germany..
    Schaefer, Thorsten
    Friedrich Schiller Univ Jena FSU, Inst Geosci, Appl Geol, Burgweg 11, D-07749 Jena, Germany..
    Impact of rock fracture geometry on geotechnical barrier integrity - A numerical study2021In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 142, article id 104742Article in journal (Refereed)
    Abstract [en]

    The effect of fracture geometry on bentonite erosion for a generic repository site in crystalline host rock environment was investigated by means of 2-d numerical simulations. Fracture geometry was varied systematically using random aperture normal distributions with a mean aperture of 1 mm and standard deviations between 0 and 0.7 mm, respectively. Moreover, two aperture correlation lengths (0.2 m and 2 m) were applied. Based on the synthetic fracture aperture fields generated the cubic law in conjunction with the Darcy equation is used to simulate fracture flow fields for mean flow velocities in the fracture between 1 x 10(-5) m/s and 1 x 10(-7) m/s. These flow fields are used in a two-way coupling approach to bentonite erosion simulations. The results of the study clearly show the influence of variable fracture aperture on bentonite erosion behaviour and erosion rates (kg/a). Increasing fracture aperture standard deviation leads to increasing heterogeneous flow velocity distributions governing the erosion behaviour and erosion rates. Calculated steady state erosion rates are in the range of similar to 0.25 kg/a down to similar to 0.014 kg/a. The highest erosion rate is calculated for the highest mean flow velocity in conjunction with the highest standard deviation. The effect of aperture heterogeneity diminishes for the lowest flow velocities. In summary, the results show the effect of fracture heterogeneity on bentonite erosion, especially for high to medium mean flow velocities combined with high to medium fracture heterogeneity under the model boundary conditions and model capabilities and limitations considered. An increase of up to g heterogeneous flow velocity distributions governing the erosion behaviour and erosion rates. Calculated steady state erosion rates are in the range of similar to 83% in erosion rate compared to the constant aperture case highlights the need to consider fracture aperture heterogeneity and its effect on the bentonite erosion in the assessment of the safety and evolution of a high-level nuclear waste repository.

  • 43. Jacobsson, L.
    et al.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. SKB, Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden..
    Kasani, H. A.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Lam, T.
    Experimental program on mechanical properties of large rock fractures2021In: IOP Conference Series: Earth and Environmental Science, IOP Publishing , 2021, Vol. 833, no 1, p. 012015-Conference paper (Refereed)
    Abstract [en]

    Predictions of fracture displacements are required to support the safety assessments of a deep geological repository for nuclear spent fuel. Laboratory and in-situ experiments are used to estimate these properties. Despite significant contributions in the last decades, there is a knowledge gap in terms of the impact of high normal stresses on the mechanical properties of large-scale fractures under Constant Normal Stiffness (CNS) boundary conditions. Within the framework of the POST project, a cooperative effort was made by SKB (Sweden), NWMO (Canada), and Posiva from Finland (in phase 1) to study these questions. In the second phase of the POST project, a first of a kind direct shear testing machine was manufactured and calibrated that can accommodate samples up to 400 × 600 mm under normal stresses up to 10 MPa, for both CNS and Constant Normal Load (CNL) conditions, with the ability to shear the sample up to 50 mm. Several best practice procedures were developed for fracture characterization pre-, syn-, and post-shear test which utilize high resolution optical scanning, contact pressure measurements, Digital Image Correlation (DIC) measurements, and acoustic emission measurements during the shear test. Natural and tensile-induced fractures of a granitic rock as well as replicas of the hard rock fractures, at three different fracture sizes of 35×60 mm, 70×100 mm, and 300×500 mm, are now being tested. It is hoped that this program will provide a set of high-quality data which will help reduce the knowledge gap in the understanding of fracture behavior.

  • 44.
    Jiang, Bin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Yao, Xiaobai
    Geospatial Analysis and Modelling of Urban Structure and Dynamics2010Collection (editor) (Other academic)
    Abstract [en]

    The increasingly urbanized world has created various problems of environment, climate, consumption of resources, and public health, which are closely linked to the side-effects of urbanization such as sprawl, congestion, housing affordability and loss of open space. Fundamental to the urban problems are two separate yet related issues: urban structure and urban dynamics. The chapters collected in this book present an excellent profile of the current state of geospatial analysis and modelling, and demonstrate how these approaches can contribute to the study of various urban issues. The book addresses key themes including new ways of capturing data digitally at the individual level, the development of systems based around networks, the notion of linking hierarchy to networks to morphology as in complexity theory, and the development of new ways of integrating diverse urban processes through simulation paying careful attention to the basic econometric and statistical principles of spatial analysis.

  • 45.
    Jin, Yunzhe
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    He, Chen
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Yao, Chi
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Sun, Zhejie
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Zhang, Xiaobo
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Yang, Jianhua
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Jiang, Qinghui
    State Key Laboratory of Civil Engineering, Wuhan University, Wuhan, 430072, China.
    Zhou, Chuangbing
    School of Infrastructure Engineering, Nanchang University, Nanchang, 330032, China.
    Effects of in-situ stress on heat transfer in fracture networks2024In: Geomechanics for Energy and the Environment, ISSN 2352-3808, Vol. 37, article id 100516Article in journal (Refereed)
    Abstract [en]

    Stress-induced fracture deformation is the principal cause for permeability change in geothermal systems. This study focuses on the influence of the nonlinear deformation and dilation effect of fractures on the geothermal system under the action of in-situ stress. By adopting a nonlinear constitutive model of rock fractures and embedding discrete fracture networks, numerical studies are first conducted to investigate the effects of different in-situ stress schemes on fracture aperture evolution using a rigid-body spring method. Based on the anisotropic aperture field of the fracture network caused by the in-situ stress, a finite element method is then used to study the flow and heat transfer process. The effects of different stress schemes on the heat flow transfer process are analyzed. Numerical simulation results show that when the ratio of horizontal to vertical stresses is not sufficient to cause shear dilation effects, the nonlinear normal deformation is the main factor affecting flow and heat transfer. In this case, the heat extraction efficiency is reduced. As the stress ratio increases, the shear dilation gradually becomes the dominant mechanism, and the heat extraction performance is improved. The obtained results provide a practical guide for geothermal site siting and optimizing heat extraction efficiency in geothermal reservoirs.

  • 46.
    Jing, Lanru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Feng, X
    Main rock mechanics issues in geological disposal of radioactive wastes: Yanshilixue Yu Gongcheng Xuebao2006In: Chinese Journal of Rock Mechanics and Engineering, ISSN 1000-6915, Vol. 25, no 4, p. 833-841Article in journal (Refereed)
    Abstract [en]

    Geological disposal of radioactive wastes is a multi-disciplinary issue of importance for national interest. It stimulated many challenging scientific and technical issues, and at a higher level, presented a series of demanding requirements for a country's overall research and development programme, its implementation and engineering practice, about basic policies and legislature concerning nuclear energy, defense, waste management and environment. Rock mechanics and rock engineering are very important fields for geological disposal of radioactive wastes, and contribute significantly to the conceptual design, site investigation, engineering design and construction, operation and the long-term safety assessment of the waste repositories. It plays, therefore, a irreplaceable role in the research and development programme of geological disposal of radioactive wastes. In this paper, we first summarizes briefly the main steps about repository system, followed by the major demands for rock mechanics and rock engineering during feasibility study and site investigation, and the major international trends concerning these issues. The focus is placed on the coupled thermo-hydro-mechanical and chemical (THMC) processes and the current status of research in international communities. At the end, the progresses in research and development works in the field of radioactive waste disposal in China are presented; and possible future working directions are discussed.

  • 47. Jing, Lanru
    et al.
    Stephansson, Ove
    Fundamentals of Discrete Element Methods for Rock Engineering2007Book (Refereed)
  • 48. Jing, Lanru
    et al.
    Stephansson, Ove
    Research results from the DECOVALEX III BECHPAR Projects2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 591-870Article in journal (Refereed)
  • 49.
    Johansson, Teddy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Artificial Ground Freezingin Clayey Soils: Laboratory and Field Studies of Deformations During Thawing at the Bothnia Line2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Artificial ground freezing as a method to temporarily stabilize and create hydraulic sealing in urban as well as in rural areas has been used in a number of Swedish construction projects, particularly during the last decade.

    One problem with the freezing of soil and rock is that fine-grained clayey types of soils have showed a tendency to under certain circumstances, during the thawing process, create a pore water overpressure and to consolidate, despite a change in the external loading conditions. In certain cases, this condition can be a desired effect as the soil mass after a freeze- and thaw cycle acquires overconsolidated properties.

    The main objectives of this study are, to describe and review the knowledge and current state of practice of artificial ground freezing, to increase the understanding about the conceptual behaviour for prognosis of the vertical deformation concerning artificial ground freezing and to compare and discuss results from laboratory and field studies concerning vertical deformation during thawing process for Bothnia soil.

    The field studies and the laboratory tests in this research study have been performed with soil from the freezing of the Bothnia Line in the vicinity of Stranneberget. The Bothnia Line is the railway link between Nyland, north of Kramfors, and Umeå.

    This thesis relates to a part of the Bothnia Line. It deals with the behaviour of soil during thawing by means of temporary stabilization and hydraulic sealing of fine-grained soil through artificial freezing using brine as the cooling agent. However, the reason behind the problem consists of the final deformations due to the thawing process.

    The general conclusions of this study are;

    • the Bothnia soil water content decreased in mean approximately 14 % after a freeze-thaw cycle, which approximately corresponds to; wth = 0.8w – 1.5
    • the decrease of the water content has no correlation to the depth below ground surface, in contrast, there is a strong correlation between the undisturbed soil water content and the magnitude of the decrease in water content
    • the soil liquid limit decreases after a freeze-thaw cycle, simultaneously as the relative share of clay and fine silt grains decreases while the relative share of more coarse grains increases
    • the coarser and denser soil created after a freeze-thaw cycle obtains an increased preconsolidation pressure and an increased undrained shear strength.
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  • 50.
    Junjun, Yin
    University of Gävle, Department of Technology and Built Environment.
    Exploring the topological patterns of urban street networks from analytical and visual perspectives2009Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Research interests in the studies of complex systems have been booming in many disciplines for the last decade. As the nature of geographic environment is a complex system, researches in this field are anticipated. In particular, the urban street networks in the Geographic Information System (GIS) as complex networks are brought forth for the thesis study. Meanwhile, identifying the scale-free property, which is represented as the power law distribution from a mathematical perspective, is a hot topic in the studies of complex systems. Many previous studies estimated the power law distributions with graphic method, which used linear regression method to identify the exponent value and estimate the quality that the power law fits to the empirical data. However, such strategy is considered to cause inaccurate results and lead to biased judgments. Whereas, the Maximum Likelihood Estimation (MLE) and the Goodness of fit test based on Kolmogorov-Smironv (KS) statistics will provide more solid and trustable results for the estimations. Therefore, this thesis addresses these updated methods exploring the topological patterns of urban street networks from an analytical perspective, which is estimating the power law distributions for the connectivity degree and length of the urban streets. Simultaneously, this thesis explores the street networks from a visual perspective as well. The visual perspective adopts the large network visualization tool (LaNet-vi), which is developed based on the k-core decomposition algorithm, to analyze the cores of the urban street networks. By retrieving the spatial information of the networks from GIS, it actually enables us to see how the urban street networks decomposed topologically and spatially. In particular, the 40 US urban street networks are reformed as natural street networks by using three "natural street" models.

    The results from analytical perspective show that the 80/20 principle still exists for both the street connectivity degree and length qualitatively, which means around 20% natural streets in each network have a connectivity degree or length value above the average level, while the 80% ones are below the average. Moreover, the quantitative analysis revealed the fact that most of the distributions from the street connectivity degree or length of the 40 natural street networks follow a power law distribution with an exponential cut-off. Some of the rest cases are verified to have power law distributions and some extreme cases are still unclear for identifying which distribution form to fit. The comparisons are made to the power law statement from previous study which used the linear regression method. Moreover, the visual perspective not only provides us the chance to see the inner structures about the hierarchies and cores of the natural street networks topologically and spatially, but also serves as a reflection for the analytical perspective. Such relationships are discussed and the possibility of combining these two aspects are pointed out. In addition, the future work is also proposed for making better studies in this field.

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