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  • 1. Abderrazek, K.
    et al.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Seffen, M.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Srasra, N. Frini
    Srasra, E.
    Photocatalytic degradation of indigo carmine using [Zn-Al] LDH supported on PAN nanofibres2015Inngår i: Clay minerals, ISSN 0009-8558, E-ISSN 1471-8030, Vol. 50, nr 2, s. 185-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zn-Al layered double hydroxides (LDH), before and after calcination, were tested for the removal of indigo carmine (IC) dye from solution. These LDH photocatalysts were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry/differential thermogravimetry (TG/DTG), nitrogen physisorption at -196 degrees C, scanning electron microscopy (SEM) and diffuse reflectance spectrophotometry (DRS). The different photocatalysts were supported on polyacrylonitrile (PAN) nanofibres, so that filtration was unnecessary. The PXRD and FTIR analyses showed that the IC adsorption on c-Zn-Al-3-500 (LDH calcined at 500 degrees C) was enhanced by construction of the hydrotalcite matrix intercalated with the dye. The intercalation was clearly evidenced by the appearance of a peak at low degrees 2 theta values. All of the materials prepared exhibited photocatalytic activity, which for the c-Zn-Al-3-500 was comparable to that of commercial PAN-supported ZnO nanoparticles (100% degradation after 180 min). Kinetic studies showed that the degradation of the IC followed a pseudo-first order rate. The high activity and the ease of both synthesis and separation processes rendered this photocatalyst a promising candidate for environmental remediation.

  • 2.
    Acuña, José
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Distributed thermal response tests: New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes2013Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 3.
    Ahmad, Nawaz
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    REACTIVE TRANSPORT MODELLING OF DISSOLVED CO2 IN POROUS MEDIA: Injection into and leakage from geological reservoirs2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the greenhouse gas emissions. However, leakage of CO2 from the storage reservoir is a risk associated with geological sequestration. Over longer times, large-scale groundwater motion may cause leakage of dissolved CO2 (CO2aq).

    The objectives of this thesis are twofold. First, the modelling study analyzes the leakage of CO2aq along the conducting pathways. Second, a relatively safer mode of geological storage is investigated wherein CO2aq is injected in a carbonate reservoir. A reactive transport model is developed that accounts for the coupled hydrological transport and the geochemical reactions of CO2aq in the porous media. The study provides a quantitative assessment of the impact of advection, dispersion, diffusion, sorption, geochemical reactions, temperature, and heat transport on the fate of leaking CO2aq.

    The mass exchange between the conducting pathway and the rock matrix plays an important role in retention and reactions of leaking CO2aq. A significant retention of leaking CO2aq is caused by its mass stored in aqueous and adsorbed states and its consumption in reactions in the rock matrix along the leakage pathway. Advection causes a significant leakage of CO2aq directly from the reservoir through the matrix in comparison to the diffusion alone in the rock matrix and advection in a highly conducting, but thin fracture. Heat transport by leaking brine also plays an important role in geochemical interactions of leaking CO2aq

    Injection of CO2aq is simulated for a carbonate reservoir. Injected CO2-saturated brine being reactive causes fast dissolution of carbonate minerals in the reservoir and fast conversion of CO2aq through considered geochemical reactions. Various parameters like dispersion, sorption, temperature, and minerals reaction kinetics are found to play important role in the consumption of CO2aq in reactions.

  • 4.
    Ahmad, Nawaz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Jarsjö, Jerker
    Stockholm University, Sweden.
    Sanchez-Vila, Xavier
    Universitat Politècnica de Catalunya, UPC-BarcelonaTech, 08034 Barcelona, Spain.
    Bottacin-Busolin, Andrea
    Hellevang, Helge
    Non-isothermal reactive transport modelling of dissolved CO2 leaking through a fractured caprockManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Geological storage of CO2 is considered as one of the mitigation actions for climate change adverse effects. However, some fraction of CO2 dissolved in the brine following injection, may leak from the reservoir through permeable zones such as conducting fractures. In this study we perform the reactive transport modelling of single-phase brine saturated with dissolved CO2 (CO2aq) along a conducting fracture in a clay-rich caprock. This study investigates the role of temperature and various reaction systems on the fate of migrating CO2aq, its geochemical interactions with the carbonate minerals, its conversion in geochemical reactions and associated medium porosity and permeability evolutions along the transport pathway.About 0.64% of leaking CO2aq is found converted into other ions in its geochemical interactions with calcite (simplified geochemical system). Addition of mineral dolomite in the geochemical system (extended geochemical system) results in up to 11% higher mass conversion of CO2 in reactions as compared to the simplified geochemical system. Considering extended geochemical system and heat transport by moving brine resulted in about 27.34% higher mass conversion of CO2 in reactions as compared to the simplified geochemical system. A combination of extended geochemical system, heat transport and sorption resulted in about 82.59% higher mass conversion of CO2 compared to the simplified geochemical system. Leaking CO2aq travelled less than 250 m along the fractured pathway, for a velocity of nearly 19 m/year in the fracture, due to retardation caused by mass stored in aqueous and adsorbed states.

  • 5.
    Ahmad, Nawaz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Sanchez-Vila, Xavier
    Universitat Politècnica de Catalunya, UPC-BarcelonaTech, 08034 Barcelona, Spain.
    Bottacin-Busolin, Andrea
    The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zoneManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    CO2 that is injected into a storage reservoir can leak in dissolved form because of brine displacement from the reservoir, which is caused by large-scale groundwater motion. Simulations of the reactive transport of leaking CO2aq along a conducting fracture in a clay-rich caprock are conducted to analyze the effect of various physical and geochemical processes. Whilst several modelling transport studies along rock fractures have considered diffusion as the only transport process in the surrounding rock matrix (diffusive transport), this study analyzes the combined role of advection and dispersion in the rock matrix in addition to diffusion (advection-dominated transport) on the migration of CO2aq along a leakage pathway and its conversion in geochemical reactions. A sensitivity analysis is performed to quantify the effect of fluid velocity and dispersivity. Variations in the porosity and permeability of the medium are observed in response to calcite dissolution and precipitation along the leakage pathway. We observe that advection and dispersion in the rock matrix play a significant role in the overall transport process. For the parameters that were used in this study, advection-dominated transport increased the leakage of CO2aq from the reservoir by nearly 305%, caused faster transport and increased the mass conversion of CO2aq in geochemical reactions along the transport pathway by approximately 12.20% compared to diffusive transport. 

  • 6.
    Ahmad, Nawaz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Sanchez-Vila, Xavier
    Bottacin-Busolin, Andrea
    The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zone2016Inngår i: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 98, s. 132-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CO2 that is injected into a geological storage reservoir can leak in dissolved form because of brine displacement from the reservoir, which is caused by large-scale groundwater motion. Simulations of the reactive transport of leaking CO2aq along a conducting fracture in a clay-rich caprock are conducted to analyze the effect of various physical and geochemical processes. Whilst several modeling transport studies along rock fractures have considered diffusion as the only transport process in the surrounding rock matrix (diffusive transport), this study analyzes the combined role of advection and dispersion in the rock matrix in addition to diffusion (advection-dominated transport) on the migration of CO2aq along a leakage pathway and its conversion in geochemical reactions. A sensitivity analysis is performed to quantify the effect of fluid velocity and dispersivity. Variations in the porosity and permeability of the medium are found in response to calcite dissolution and precipitation along the leakage pathway. We observe that advection and dispersion in the rock matrix play a significant role in the overall transport process. For the parameters that were used in this study, advection-dominated transport increased the leakage of CO2aq from the reservoir by nearly 305%, caused faster transport and increased the mass conversion of CO2aq in geochemical reactions along the transport pathway by approximately 12.20% compared to diffusive transport.

  • 7.
    Ahmad, Nawaz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vattendragsteknik.
    Sanchez-Vila, Xavier
    Universitat Politècnica de Catalunya, UPC-BarcelonaTech, 08034 Barcelona, Spain.
    Jarsjö, Jerker
    Stockholm University, Sweden.
    Bottacin-Busolin, Andrea
    Hellevang, Helge
    Injection of CO2-saturated brine in geological reservoir: A way to enhanced storage safetyManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Injection of free phase supercritical CO2 into deep geological reservoirs is associated with risk of considerable return flows towards the land surface due to the buoyancy of CO2, which is lighter than the resident brine in the reservoir. Such upward movements can be avoided if CO2 is injected in the dissolved phase (CO2aq). In this work, injection of CO2-saturated brine in a subsurface carbonate reservoir is modelled. Physical and geochemical interactions of injected low-pH CO2-saturated brine with the carbonate minerals (calcite, dolomite and siderite) are investigated in the reactive transport modelling. CO2-saturated brine, being low in pH, shows high reactivity with the reservoir minerals, resulting in a significant mineral dissolution and CO2 conversion in reactions. Over the injection period of 10 years, up to 16% of the injected CO2 is found consumed in geochemical reactions. Sorption included in the transport analysis resulted in additional quantities of CO2 mass stored. However, for the considered carbonate minerals, the consumption of injected CO2aq is found mainly in the form of ionic trapping.

  • 8.
    Al-Ajmi, Adel
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Wellbore stability analysis based on a new true-triaxial failure criterion2006Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A main aspect of wellbore stability analysis is the selection of an appropriate rock failure criterion. The most commonly used criterion for brittle failure of rocks is the Mohr-Coulomb criterion. This criterion involves only the maximum and minimum principal stresses, s1 and s3, and therefore assumes that the intermediate stress s2 has no influence on rock strength. When the Mohr-Coulomb criterion had been developed, it was justified by experimental evidence from conventional triaxial tests (s1>s2=s3). Based on triaxial failure mechanics, the Mohr-Coulomb criterion has been extensively used to represent rock failure under the polyaxial stress state (s1>s2>s3).

    In contrast to the predictions of Mohr-Coulomb criterion, much evidence has been accumulating to suggest that s2 does indeed have a strengthening effect. In this research, I have shown that Mohr-Coulomb failure criterion only represents the triaxial stress state (s2=s3 or s2=s1), which is a special case that will only occasionally be encountered in situ. Accordingly, I then developed a new true-triaxial failure criterion called the Mogi-Coulomb criterion. This failure criterion is a linear failure envelope in the Mogi domain (toct-sm,2 space) which can be directly related to the Coulomb strength parameters, cohesion and friction angle. This linear failure criterion has been justified by experimental evidence from triaxial tests as well as polyaxial tests. It is a natural extension of the classical Coulomb criterion into three dimensions.

    As the Mohr-Coulomb criterion only represents rock failure under triaxial stress states, it is expected to be too conservative in predicting wellbore instability. To overcome this problem, I have developed a new 3D analytical model to estimate the mud pressure required to avoid shear failure at the wall of vertical, horizontal and deviated boreholes. This has been achieved by using linear elasticity theory to calculate the stresses, and the fully-polyaxial Mogi-Coulomb criterion to predict failure. The solution is achieved in closed-form for vertical wellbores, for all stress regimes. For deviated or horizontal wellbores, Mathcad programs have been written to evaluate the solution. These solutions have been applied to several field cases available in the literature, and the new model in each case seems to be consistent with the field experience.

  • 9.
    Andersson, J. Christer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Rock Mass Response to Coupled Mechanical Thermal Loading: Äspö Pillar Stability Experiment, Sweden2007Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The geological disposal of nuclear waste, in underground openings and the long-term performance of these openings demand a detailed understanding of fundamental rock mechanics. A full scale field experiment: Äspö Pillar Stability Experiment was conducted at a depth of 450 m in sparsely fractured granitic rock to examine the rock mass response between two deposition holes. An oval shaped tunnel was excavated parallel to the σ3 direction to provide access to the experiment and also provide elevated stress magnitudes in the floor. In the tunnel floor two 1.75-m diameter 6-m deep boreholes were excavated so that a 1-m thick pillar was created between them. In one of the holes a confinement pressure of 700 kPa was applied and in the other displacement transducers were installed. The pillar volume was monitored by an Acoustic Emission System. Spatially distributed thermocouples were used to monitor the temperature development as the pillar was heated by electrical heaters. The excavation-induced stress together with the thermal-induced stress was sufficient to cause the wall of the open borehole to yield. The temperature-induced stress was increased slowly to enable detailed studies of the rock mass yielding process. Once the rock mass loading response was observed, the rock mass was unloaded using a de-stress slotting technique.

    This thesis focuses on the in-situ study of the rock mass response to coupled mechanical thermal loading and thermal-mechanical unloading. The experiment, its design, monitoring and observations are thoroughly described. An estimate of the yielding strength of the rock mass is presented and compared with laboratory test and results from other rock mass conditions reported elsewhere in the open literature. General conclusions about the effect of the confining pressure and the observations from the unloading of the pillar are also presented.

    Important findings are that the yielding strength of the rock mass has been successfully determined, low confinement pressures significantly affects the onset of yielding, the primary mode of fracture initiation and propagation is extensional, no significant time dependency of the yielding process was observed. The unloading studies also indicated that what appeared to be shear bands likely was a propagating zone of extensile failure that weakened the rock so that displacements in the shear direction could occur.

  • 10.
    Ask, Daniel
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    New developments in the Integrated Stress Determination Method and their application to rock stress data at the Aspo HRL, Sweden2006Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, nr 1, s. 107-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Integrated Stress Determination Method (ISDM) is a powerful tool for estimating the regional stress tensor from in-situ measurements of local stress tensors using a wide variety of stress measuring techniques. This study presents new developments of the ISDM: The stress field may be described with up to 12 model parameters; and is applicable to data from CSIR- and CSIRO HI-type of overcoring devices, hydraulic fracturing, hydraulic tests of pre-existing fractures (HTPF), as well as to combined data sets. Furthermore, in combined data sets, the hydraulic fracturing and/or HTPF data may be used to constrain the average elastic parameters, Young's modulus and Poisson's ratio. The new ISDM developments were applied to the extensive and recently re-analysed rock stress data at the Aspo Hard Rock Laboratory. The results reveal a good fit of the re-analysed data. Overall, the re-analysis indicates that the stress field at Aspo HRL is relatively well constrained and consistent with depth. The NE-2 Fracture Zone influences the stresses, and dividing the regional stress field into a NW and a SE stress domain. When the hydraulic fracturing data were used to constrain the average elastic parameters, Young's modulus, E, and Poisson's ratio, v, quite similar results were obtained (E = 50.8 GPa and v = 0.33) compared with results from biaxial tests of overcore samples (E = 61.6 MPa and v = 0.26).

  • 11.
    Belonoshko, Anatoly B.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Lukinov, Timofiy
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Rosengren, Anders
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori. KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. AlbaNova University Center, Sweden.
    Bryk, Taras
    Litasov, Konstantin D.
    Synthesis of heavy hydrocarbons at the core-mantle boundary2015Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikkel-id 18382Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis of complex organic molecules with C-C bonds is possible under conditions of reduced activity of oxygen. We have found performing ab initio molecular dynamics simulations of the C-O-H- Fe system that such conditions exist at the core-mantle boundary (CMB). H2O and CO2 delivered to the CMB by subducting slabs provide a source for hydrogen and carbon. The mixture of H2O and CO2 subjected to high pressure (130 GPa) and temperature (4000 to 4500 K) does not lead to synthesis of complex hydrocarbons. However, when Fe is added to the system, C-C bonds emerge. It means that oil might be a more abundant mineral than previously thought.

  • 12.
    Benavente, Martha
    et al.
    Faculty of Chemical Engineering, National University of Engineering (UNI), Managua, Nicaragua.
    Casas, Jesús M.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Speciation of Cyanide and Compounds related to the Washing of Gold Ore Tailing2002Inngår i: CIQ 2002: Proceedings of the 15th Chilean Congress of Chemical Engineering, Punta Arenas, Chile, 2002Konferansepaper (Fagfellevurdert)
  • 13. Berumen, S. A.
    et al.
    Pérez-Megino, L. P.
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.).
    Socioeconomic ranking for the development of coal-mining regions in Europe2016Inngår i: Revista de Métodos Cuantitativos para la Economía y la Empresa, ISSN 1886-516X, Vol. 21, nr 1, s. 39-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The socioeconomic situation of European coalfields is highly heterogeneous. On the one hand, successful examples comprise regions that long ago embraced internationalization, innovation and/or restructuring strategies. In those regions where the aforementioned strategies were fruitful, the development of new production methods led to gradual repopulation. Less successful examples, however, are likely to experience undesired effects as a consequence of both the suppression of aid (EU- and regional- level) and the liberalization of EU mining markets, starting on December 31, 2018. This papers aims to provide a method to accurately assess the socioeconomic situation of these regions. As such a method is rooted in previous policies, it enables the identification of welfare-enhancing policies for the inhabitants of European coalfield regions.

  • 14. Bond, A. E.
    et al.
    Chittenden, N.
    Fedors, R.
    Lang, P.
    McDermott, C.
    Neretnieks, Ivars
    KTH.
    Pan, P. Z.
    Šembera, J.
    Bruský, I.
    Watanabe, N.
    Lu, R.
    Yasuhara, H.
    Coupled THMC modelling of single fractures in novaculite and granite2018Inngår i: 2nd International Discrete Fracture Network Engineering Conference, DFNE 2018, American Rock Mechanics Association (ARMA), 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The host rock immediately surrounding a nuclear waste repository has the potential to undergo a complex set of physical and chemical processes starting from construction of the facility and continuing until many years after closure. Understanding the relevant processes of fracture evolution may be key to supporting the attendant safety arguments for such a facility. Experimental work has been examined wherein artificial fractures in novaculite and granite are subject to a mechanical confining pressure, variable fluid flows and different applied temperatures. This paper presents a synthesis of the work of seven separate research teams. A range of approaches are summarized including detailed thermal-hydrological-mechanical-chemical (THMC) models and homogenized ‘single compartment’ models of the fracture; the latter with a view to larger network or effective continuum models. The competing roles of aqueous geochemistry, pressure solution, stress corrosion and pure mechanics were found to be significant in the reproduction of the experimental observations. The results of the work show that while good, physically plausible representations of the experiment can be obtained, there is considerable uncertainty in the relative importance of the various processes, and that the parameterization of these processes can be closely linked to the physical interpretation of the fracture surface topography.

  • 15.
    Casas, Jesús M.
    et al.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Speciation of Copper Mine Solutions1994Inngår i: CONAMET'94 & ALAMET III, Vol. 1: Proceedings of the 8th Chilean Congress of Metallurgy and the 3rd Congress of the Latin-American Association of Metallurgy and Materials, Antofagasta, Chile: Catholic University of North , 1994, s. 1-10Konferansepaper (Fagfellevurdert)
  • 16.
    Casas, Jesús M.
    et al.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Vargas, T.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Influence of Bacterial Activity on Temperature, Oxygen Profiles and Leaching Rates in the Bioleaching of Copper Sulfide Ore Beds1997Inngår i: IBS 97: Proceedings of the International Biohydrometallurgy Symposium, Sydney, Australia: Australian Mineral Foundation , 1997, s. M5-3.1Konferansepaper (Fagfellevurdert)
  • 17.
    Casas, Jesús M.
    et al.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Vargas, T.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Two-Dimensional Model of Heat and Gas Transport and Mineral Oxidation in Copper Bioleaching Dump1995Inngår i: Biohydrometallurgical Processing, Vol. 1: Proceedings of the International Biohydrometallurgy Symposium (IBS-95) / [ed] Vargas, T., Jerez, C.A., Wiertz, J.V., Toledo, H., Santiago, Chile: University of Chile , 1995, s. 447-457Konferansepaper (Fagfellevurdert)
  • 18.
    Casas, Jesús M.
    et al.
    Dept of Mining Engineering, University of Chile, Santiago, Chile.
    Vargas, T.
    Dept of Chemical Engineering, University of Chile, Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Bioleaching model of a copper-sulfide ore bed in heap and dump configurations1998Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 29, nr 4, s. 899-909Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-dimensional (2-D) model for a heap or dump bioleaching of a copper ore containing mainly chalcocite and pyrite has been developed. The rate of the mineral sulfide dissolution was related to the rate of oxidation by bacteria attached onto the ore surface. The latter was calculated using the model of Michaelis-Menten, where both temperature and dissolved oxygen in the leach solution were taken into account by the kinetic equation. Oxygen transport through the ore bed was associated with natural air convection originating from the decrease in gas density inside the ore bed, which was attributable not only to heating, but also to humidification and decrease in the oxygen concentration. The model was used to estimate air-velocity fields and profiles of temperature and oxygen concentrations as well as mineral conversions during the bioleaching operation for ore beds with different pyrite contents, bacterial populations, widths, heights, and permeabilities. The model provides a useful tool for the design, improvement, and optimization of industrial operating conditions.

  • 19.
    Casas, Jesús M.
    et al.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Vargas, T.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Modelling of Bioleaching from Low Grade Copper Sulphide Ore1993Inngår i: Biohydrometallurgical Technologies, Vol. 1: Proceedings of an International Biohydrometallurgy Symposium (IBS'93) / [ed] A.E. Torma, J.E. Wey, V.I. Lakshmanan, The Minerals, Metals & Materials Society , 1993, s. 249-258Konferansepaper (Fagfellevurdert)
  • 20. Chen, Yifeng
    et al.
    Hu, Shaohua
    Wei, Kai
    Hu, Ran
    Zhou, Chuangbing
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Experimental characterization and micromechanical modeling of damage-induced permeability variation in Beishan granite2014Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 71, s. 64-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Triaxial compression tests with measurements of permeability were performed on core granite samples taken at 450-550 m depth from the Beishan area in Gansu Province, a potential site for China's high-level radioactive waste (HLW) disposal. Corresponding to the distinct features in the stress-strain behaviors, the permeability of the Beishan granite was found to evolve with a clear permeability decrease in the initial microcrack closure region, a constant permeability value in the elastic region and a dramatic permeability increase in the crack growth region. The permeability increases by up to and over two orders of magnitude as deviatoric stress increases up to sample failure; but at a given deviatoric stress, the permeability reduces remarkably with the increase of confining pressure. An empirical upper bound permeability model was presented by relating the mechanisms involved in the microstructure alteration to the permeability change, and the experimental results were well simulated by the proposed model. Combined with field geological characterization and numerical simulation, the implications of the experimental results for China's HLW disposal were discussed.

  • 21.
    Einstein, H. H.
    et al.
    United States.
    Stephansson, Ove
    KTH.
    Fracture systems, fracture propagation and coalescence2018Inngår i: ISRM International Symposium 2000, IS 2000, International Society for Rock Mechanics , 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the context of "strength of rocks for rock slope design" this paper concentrates on the fact that rock masses are discontinua and, in many cases, have to be modelled as such. The paper, therefore, first describes various ways in which fracture systems can be described. Specifically, geometric, mechanical and geometric - mechanical models are discussed with emphasis on the latter. When considering slope stability, as well as rock mass behavior in general, it is very important to capture the mechanisms by which the discontinuities interact with each other. This interaction involves fracture coalescence which is the second major part of the paper. While all the preceding problems involve mainly non-persistent fractures, a few final comments are made on some special issues relating to persistent fractures. Throughout the paper we attempt to present the state-of-the-art of theory and compare it to the state of practice.

  • 22. Englund, David
    et al.
    Brunberg, Anna
    Jacks, Gunnar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    A CASE STUDY OF A FRESHWATER PEARL MUSSEL (MARGARITIFERA MARGARITIFERA) POPULATION IN CENTRAL SWEDEN2008Inngår i: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 90A, nr 4, s. 251-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most of the Margaritifera margaritifera populations in Sweden are not reproducing. Land use such as forestry, eutrophication and water regulation for hydropower are commonly reported causes for the absence of reproduction. A brook with a very dense population of pearl mussels has been investigated with regard to the age distribution of the population and their habitat, in order to discover the reason for the absence of reproduction. The population consisted almost entirely of old mussels with very few young ones. The water flow and chemistry of the water are very stable and well buffered, due to a large glacifluvial deposit in the catchment area. The substrate in the stream is favourable and well aerated to a depth of at least 15 cm. Forestry has been practised with care for at least the last 15 years to avoid siltation of the stream sediments. The most likely reason for the lack of reproduction seems to be the water regulation of the main stream introduced 60 years ago, which has left the main stream dry seasonally. This is likely to have affected the population of brown trout which is the host for the first life-stage of the mussels, the glochidia.

  • 23.
    Fidalgo, Alexandre Barreiro
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Can H-2 enhance the oxidative dissolution of UO2?2016Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 477, s. 85-87Artikkel i tidsskrift (Fagfellevurdert)
  • 24.
    Hudson, John A.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Stephansson, Ove
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Andersson, J
    Guidance on numerical modelling of thermo-hydro-mechanical coupled processes for performance assessment of radioactive waste repositories2005Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, nr 5-6, s. 850-870Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper provides advice on how to incorporate thermo-hydro-mechanical (THM) coupled processes into performance and safety assessments and design studies for radioactive waste disposal in geological formations. The advice is based on work conducted for the EU research project BENCHPAR: "Benchmark Tests and Guidance on Coupled Processes for Performance Assessment of Nuclear Waste Repositories". In Section 1, there is an explanation of why numerical analyses incorporating THM mechanisms are required for radioactive waste studies and background material on the subject is provided. Then, the THM processes and their interactions are explained in Section 2. Three case examples of THM numerical analysis are presented in Section 3 to illustrate the type of work that can be conducted to study the near-field, upscaling, and the far-field. The importance and priority of the THM couplings are summarized in Section 4. Recommended soft and hard auditing procedures are presented in Section 5. We place special emphasis on the fact that the most important step in numerical modelling is not executing the calculations per se, but the earlier conceptualization of the problem regarding the dominant processes, the material properties and parameters, the engineering perturbations, and their mathematical presentations. The associated modelling component of addressing the uncertainties and estimating their influence on the results is also important. Thus, the specific models and codes should be studied first to evaluate the harmony between the nature of the problem and the nature of the codes. The tactical use of particular numerical techniques will then be based on a sound strategic foundation. An associated listing of bullet point recommendations and issues for future directions for this THM subject area is given in Section 6.

  • 25.
    Jing, Lanru
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Hudson, J. A.
    Fundamentals of the hydro-mechanical behaviour of rock fractures: roughness characterization and experimental aspects2004Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, nr 3, s. 383-383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The coupled hydro-mechanical behaviour of rock fractures plays an important role in design, performance and safety assessments of rock engineering projects. However, due to the complexity in the mathematical representation of the fracture surface geometry and its effects on the stress-flow behaviour of the fractures, and the limitations in the test conditions in laboratories, significant lack of knowledge still exists in testing and modelling approaches regarding rock fractures. Based on a general review of the roughness characterization and shear-flow testing of rock fractures, this paper presents the definition of the stationarity threshold of roughness, and a combined experimental-numerical approach for simulating rock fracture testing conditions for more general fluid flow behaviour of the rock fractures. The conclusions are that fracture roughness characterization must be conducted and represented in three-dimensions and the more general fluid flow behaviour cannot be observed with conventional parallel shear-flow tests or compressionradial flow tests. Numerical simulations are needed to reveal more general behaviour of stress-flow processes of rock fractures with boundary and loading conditions that are difficult or impractical in laboratory tests.

  • 26.
    Jing, Lanru
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Min, K. -B
    Baghbanan, A.
    Zhao, Z.
    Understanding coupled stress, flow and transport processes in fractured rocks2012Inngår i: ISRM Regional Symposium - 7th Asian Rock Mechanics Symposium, ARMS 2012, International Society for Rock Mechanics , 2012, s. 44-72Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a review of a systematic research program for understanding scale and stress effects on transport behaviours of fractured crystalline rocks, using a hybrid discrete element and particle tracking approach. The motivation is the importance of understanding stress effects on behaviours of contaminant transport in fractured crystalline rocks, an important issue of rock mechanics for environmental safety assessments of many rock engineering projects. The study is divided into three steps. The first step is a basic study that established the mathematical platform for deriving the conditions, criteria, basic approaches and test case results for investigating stress and scale effects on hydraulic behavior of the fractured rock concerned. At the second step, based on outstanding issues drawn from the first step, the study was extended to consider effects of the correlation between the fracture aperture and size (represented by trace length) on the permeability of the fractured rock, and uncertainties in deriving equivalent continuum properties of fractured rocks. The third step added the particle/solute transport processes to the mathematical platform, including different retardation mechanisms, so that impact of stress on safety can be directly evaluated, even it can only be done conceptually. The obtained results show that stress, scale and inter-parameter correlations of the fracture system geometry are dominant issues for understanding and characterization of coupled hydro-mechanical processes of fractured rocks and play a significant role for understanding the mass transport behaviour in them, with direct impact on geo-environmental safety. 

  • 27.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Influence of scale and matedness on the peak shear strength of fresh, unweathered rock joints2016Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 82, s. 36-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 28.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Shear Strength of Unfilled and Rough Rock Joints in Sliding Stability Analyses of Concrete Dams2009Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The horizontal water load combined with uplift forces implies that concrete damsare sensitive for sliding. At the same time, the safety of concrete dams againstsliding in the rock foundation is associated with large uncertainties. One of themain uncertainties regards the shear strength of rock joints.

    Several failure criteria exist to express the shear strength for unfilled and roughrock joints. However, these criteria do not in general consider a possible scaleeffect which means that the shear strength could be lower at larger scales. Somesuggestions exist for how a possible scale effect could be considered, but theseare mainly based on empiric grounds. This means that there exists a need of amore detailed and conceptual understanding on the scale effect of rock joints.

    In an attempt to increase the understanding on the scale effect of unfilled andrough rock joints, a conceptual model was derived. The model is based on theassumptions that contact points occur at the steepest asperities facing the sheardirection and that their total area could be expressed with adhesion theory. Fractaltheory is used in order to idealize the surface roughness by superposition ofasperities at different scales. Based on changes in the size and number of contactpoints, the conceptual model suggests that the scale effect does not occur for alltypes of rock joints. Perfectly mated joints are suggested to not exhibit any scaleeffect while a considerable scale effect could be expected for unmated joints.

    The practical implications from this, for foundations with unfilled joints, is thatunmated joints with large aperture are most critical for the sliding stability ofconcrete dams, since these joints probably are the ones with longest persistenceand lowest shear strength.

    In order to study the scale effect of rock joints further, eighteen shear tests atdifferent scales were performed. All of the samples were taken from the rockfoundation at Långbjörn hydropower station. Possible scale effects could beobserved, but no firm conclusions could be made, mainly due to different surfacecharacteristics of the tested joints. Three of the samples were also used toinvestigate the accuracy of the conceptual model. This investigation revealed thatit may be necessary to distinguish between weathered and unweathered joints,since the distribution of contact points appears to become more randomlydistributed for a weathered joint which in turn results in lower friction angles.

    In Sweden, dam safety is governed by the Swedish power company’s guidelinesfor dam safety, RIDAS. When the Swedish guidelines were compared withguidelines and regulations in other countries, it was realized that there exists aneed for a more balanced evaluation of the sliding stability for concrete damsfounded on rock in Sweden. In a first step of development, it can be based onsafety factors and an increased use of investigations. However, in a second step, anatural way of the development of RIDAS would be in a direction towardsreliability based methods.

  • 29.
    Johansson, Fredrik
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Bagheri, Mehdi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Stille, Håkan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Variation of mechanical parameters of a slightly weathered joint in granite estimated from fourteen shear tests2010Inngår i: ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 2010, s. 223-226Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Describing the mechanical parameters of a rock joint with single values is difficult since rock has a natural spatial variation. In addition to this, the interpretation of the results is dependent on the number of tests. Despite this fact, input data for these parameters are often given with a deterministic value. This paper presents the results of fourteen shear tests tested under a constant normal stress of approximately 0.8 MPa. The samples were taken from a slightly weathered rock joint in granite. Basic friction angle and dilation angle, together with shear and normal stiffness, are evaluated. Based on the results, mean values and standard deviations together with coefficient of variations for the different parameters are presented. After that, different statistical distributions for the parameters are compared. Finally, the results are compared against calculated values derived from commonly used equations.

  • 30.
    Johansson, Nils
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Strategiska hållbarhetsstudier.
    Gruvdrift eller återvinning av metaller? En politisk fråga2018Inngår i: Svensk gruvpolitik i omvandling: Aktörer, kontroverser, möjliga världar / [ed] Jonas Anshelm, Simon Haikola, Björn Wallsten, Halmstad: Gidlunds förlag, 2018, s. 201-214Kapittel i bok, del av antologi (Fagfellevurdert)
  • 31.
    Johnson, Kyle D.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Raftery, Alicia M.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Lopes, Denise Adorno
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Fabrication and microstructural analysis of UN-U3Si2 composites for accident tolerant fuel applications2016Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 477, s. 18-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, U3Si2 was synthesized via the use of arc-melting and mixed with UN powders, which together were sintered using the SPS method. The study revealed a number of interesting conclusions regarding the stability of the system - namely the formation of a probable but as yet unidentified ternary phase coupled with the reduction of the stoichiometry in the nitride phase - as well as some insights into the mechanics of the sintering process itself. By milling the silicide powders and reducing its particle size ratio compared to UN, it was possible to form a high density UN-U3Si2 composite, with desirable microstructural characteristics for accident tolerant fuel applications.

  • 32.
    Johnson, Kyle D.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Jolkkonen, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Claisse, Antoine
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Spark plasma sintering and porosity studies of uranium nitride2016Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 473, s. 13-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD-corresponding to an absolute density of 14.25 g/cm3 out of a theoretical density of 14.28 g/cm3-have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density.

  • 33.
    Komlev, Andrei A.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnkraftssäkerhet.
    Almjashev, Vyacheslav I.
    Bechta, Sevostian V.
    Khabensky, Vladimir B.
    Granovsky, Vladimir S.
    Gusarov, Victor V.
    New sacrificial material for ex-vessel core catcher2015Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 467, s. 778-784Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new functional (sacrificial) material has been developed in the Fe2O3-SrO-Al2O3-CaO system based on strontium hexaferrite ceramic in concrete matrix. The method of producing SM has been advanced technologically; this technological effectiveness allows the SM to be used in ex-vessel core catchers with corium spreading as well as in crucible-type core catchers. Critical properties regarding the efficiency of SM in ex-vessel core catchers, such as porosity, pycnometric density, apparent density, solidus and liquidus temperatures, and water content have been measured. Suitable fractions of SrFe12O19 and high alumina cement (HAC) were found in the SM based on thermodynamic analysis of the SM/corium interaction. The use of sacrificial steel as an additional heat adsorption component in the core catcher allowed us to increase the mass fraction range of SrFe12O19 in the SM from 0.3-0.5 to 0.3-0.85. The activation temperature of the SM/corium interaction has been shown to correspond to the liquidus temperature of the local composition at the SM/corium interface. The calculated value of this temperature was 1716 degrees C. Analysis of phase transformations in the SrO-Fe2O3 system revealed advantages of the SrFe12O19-based sacrificial material compared with the Fe2O3-contained material owing to the time proximity of SrFe12O19 decomposition and corium interaction activation.

  • 34. Liu, D W
    et al.
    Gu, D S
    Dai, T G
    Henkel, Herbert
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Analysis and calculation of thermal conductivity of rock in deep strata2005Inngår i: Journal of Central South University of Technology, ISSN 1005-9784, E-ISSN 1993-0666, Vol. 12, s. 114-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal conductivity of rock is an important parameter for the deep mine and the geothermal development. It is often not possible to measure the thermal conductivity of the rocks present in the deep strata, and the usual approach is to calculate thermal conductivity including mineralogy and porosity. The compositions of core samples from the MID01 borehole in the Björkö area were determined, and the mineral composition was classified. The calculation of the thermal conductivity of rock in the borehole was carried out, and the main factors for the thermal conductivity of rock were analyzed. The results show that the calculated thermal conductivity of rock is reliable and useful for the design and calculation of geothermal development in the Björkö area.

  • 35.
    Martínez, Joaquín
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Casas, Jesús M.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Modelling of Intermittent Irrigation in Leaching Heaps1995Inngår i: Electrorefining and Hydrometallurgy of Copper, Vol. III: Proceedings of the Copper 95 International Conference / [ed] Cooper, W.C., Dreisinger, B.D., Dutrizac, J.E., Hein, H., Ugarte, G., Santiago, Chile: The Metallurgical Society of CIM , 1995, s. 393-407Konferansepaper (Fagfellevurdert)
  • 36.
    Moreno, Luis
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Martínez, Joaquín
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Teknisk strömningslära.
    Casas, Jesús M.
    Dept of Chemical Engineering, University of Chile (UChile), Santiago, Chile.
    Modelling of Bioleaching Copper Sulphide Ores in Heaps or Dumps1999Inngår i: IBS'99: Proceedings of the International Biohydrometallurgy Symposium / [ed] Amils, R., Ballester, A., Madrid, Spain: Universidad Complutense de Madrid , 1999, s. BII-17Konferansepaper (Fagfellevurdert)
  • 37.
    Müller, Rasmus
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Larsson, Staffan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Veda trial embankment-comparison between measured and calculated deformations and pore pressure development2009Inngår i: GEOTECHNICS OF SOFT SOILS - FOCUS ON GROUND IMPROVEMENT / [ed] Karstunen M, Leoni M, BOCA RATON: CRC PRESS-TAYLOR & FRANCIS GROUP , 2009, s. 405-410Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Veda embankment is about 300 metres long, up to 16 metres high and is being built as a staged construction on vertically drained subsoil consisting of very loose post glacial sulphide clay and very loose glacial clay. The Veda trial embankment was built one year in advance in order to obtain essential knowledge about the behaviour of the subsoil when subjected to an embankment load. This paper present and discuss the process of using the measurements from the trial embankment together with laboratory tests in order to establish a numerical analysis for the Veda embankment, that describes the behaviour of the soil sufficiently well as a foundation for the design and prediction according to the observational method.

  • 38. Olupot, P. W.
    et al.
    Jonsson, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Byaruhanga, J. K.
    Proprietà di porcellane elettriche ottenute con materie prime ugandesi: Studio degli effetti dovuti alla formaulazione dell'impasto e alla temperatura di sinterizzaione2008Inngår i: Ceramurgia, ISSN 0045-6152, Vol. 38, nr 1, s. 17-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Five sample mixtures of Ugandan kaolin, ball clay, feldspar and flint were formulated and porcelain samples fabricated by extrusion through a vacuum pugmill. Samples were evaluated for formability. The degree of densificaron of sintered specimens fired at 1200 to 1350°C was evaluated by measuring the firing shrinkage, bulk density, water absorption and bending strength. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. Dielectric strength measurements were carried out on disc specimens. Dielectric and bending strength properties deteriorated at high temperatures because of pore formation and decreasing amount of undissolved quartz in the crystalline phase. An optimum composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded an unglazed body with highest bending strength of 72MPa and dielectric strength of 19MVm-1 after firing at 1250°C. The body consisted of small, closely packed mullite needles and undissolved quartz crystals embedded in a glass matrix.

  • 39. Ordonez, Javier I.
    et al.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Mellado, Mario E.
    Cisternas, Luis A.
    Modeling validation of caliche ore leaching using seawater2014Inngår i: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 126, s. 10-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Leaching column experiments of caliche were performed using seawater as the leaching agent because the caliche deposits are located in Northern Chile where water resources are scarce. The use of seawater without desalination is an attractive alternative for mining operations. The experimental recoveries of different ions were modeled using a hybrid model, which uses empirical information and fundamental principles. The following ions were considered: nitrate, iodine, sulfate, chloride, sodium, potassium and magnesium. The model explicitly considers different column heights, irrigation rates, and leaching agents. A sensitivity analysis showed that parameters associated with the particle level predominantly determined the calculated recoveries. The predictive capability was also tested, and the results were generally good, except for the sulfate ion, the dissolution of which was controlled by the presence of other ions.

  • 40.
    Rönnqvist, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Assessing potential for internal erosion in glacial moraine core embankment dams2007Inngår i: Dam Engineering, ISSN 0958-9341, Vol. 18, nr 2, s. 101-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Internal erosion, the process of washout of fine-grained material by seepage flow from an embankment dam filling material, can pose a major threat to dam safety. Internal erosion at a far reached stage can surface in the shape of sinkholes, sudden turbid leakages and settlements, indicating that the filling material in the dam is undergoing potentially significant property changes. It was early on found, for instance by Sherard [1979], that embankment dams comprising broadly graded material appear to develop sinkholes more frequent than dams of other material components. And considering that typical Swedish embankment dams are composed of material with broad and wide gradations of glacial origin, in particular the impervious core of broadly graded moraine (till), it should come as no surprise that many embankment dams in Sweden have shown signs of deterioration that can be related to internal erosion. The susceptibility for internal erosion in Swedish embankment dams was perhaps first noticed in a survey carried out by Nilsson et al [1999], where 20 % of the incorporated dams were estimated being affected by internal erosion. To reduce the risks connected to internal erosion it can be necessary to implement dam safety measures preferably at an early stage before the internal erosion progressed to surfacing, but distinguishing which dams that hold a real potential future risk for internal erosion can prove difficult. This paper is based on an evaluation comprising 45 existing Swedish embankment dams and the results show that a more discriminatory predictor, than today’s filter criteria, appears to be needed if embankment dams with widely graded glacial cores with high potential for surfacing internal erosion are to be singled out from dams apparently internal erosion free. The results indicate that not only filter coarseness needs to be addressed when assessing potential for internal erosion in embankment dams with glacial moraine cores, but also the internal stability of the core and filter.

  • 41.
    Rönnqvist, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Long-term behaviour of internal erosion afflicted dams comprising broadly graded soils2009Inngår i: Dam Engineering, ISSN 0958-9341, Vol. 20, nr 2, s. 149-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Internal erosion occurs when fine-grained particles are washed out from a filling material by seepage. Sinkholes and settlements on the dam crest, sudden increased leakage, or muddy seepage may be manifestations of progressed internal erosion. Dams with cores of glacially formed broadly graded soils have been found to be more likely to experience internal erosion than dams composed of other materials. This paper describes and reviews case histories of 30 existing dams constructed from broadly graded soils with performance history of internal erosion. Understanding i) typical signs and observations of internal erosion, ii) the timing of internal erosion incidents, iii) the possible early-warning signs, iv) the possible warning-time, and v) the location of the internal erosion incident on the dam body – may provide tools for early-warning detection of internal erosion prone dams and improve the assessment of internal erosion in existing dams.

  • 42.
    Rönnqvist, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Predicting surfacing internal erosion in moraine core dams2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Dams that comprise broadly and widely graded glacial materials, such as moraines, have been found to be susceptible to internal erosion, perhaps more than dams of other soil types. Internal erosion washes out fine-grained particles from the filling material; the erosion occurs within the material itself or at an interface to another dam zone, depending on the mode of initiation. Whether or not internal erosion proceeds depend on the adequacy of the filter material. If internal erosion is allowed, it may manifest itself as sinkholes on the crest, increased leakage and muddy seepage once it surfaces, which here is called surfacing internal erosion (i.e. internal erosion in the excessive erosion or continuation phase). In spite of significant developments since the 1980s in the field of internal erosion assessment, the validity of methods developed by others on broadly graded materials are still less clear because most available criteria are based on tests of narrowly graded granular soils. This thesis specifically addresses dams that are composed of broadly graded glacial soils and investigates typical indicators, signs and behaviors of internal erosion prone dams. Based on a review of 90+ existing moraine core dams, which are located mainly in Scandinavia as well as North America and Australia/New Zealand, this thesis will show that not only the filter’s coarseness needs to be reviewed when assessing the potential for internal erosion to surface (i.e., erosion in the excessive or continuing phase); in addition, the grading stability of the filter and the core material as well as non-homogeneities that are caused by filter segregation need to be studied. Cross-referencing between these aspects improves the assessment of potential for internal erosion in dams of broadly graded soils and furthermore it provides aid-to-judgment.

  • 43.
    Rönnqvist, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Review of moraine core dams and internal erosion2008Inngår i: Dam Engineering, ISSN 0958-9341, Vol. 19, nr 2, s. 99-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Embankment dams comprising broadly graded materials of glacial origin have in the past been identified as being prone to develop sinkholes more frequent than dams composed of materials of other origin. Sinkholes on the crest of a dam are many times an indicator of internal erosion. Internal erosion can initiate and continue to develop for many reasons, but mainly due to root causes coming from core/filter properties and interaction, possibly affected by the dam design and/or construction related reasons. In this paper a review is made on moraine core dams in the literature in relation to performance history of internal erosion. Dam data comprising 90 existing moraine core embankment dams has been compiled and assessed with objective to investigate the occurrence of indicative properties of dams that have developed internal erosion. The data set of dams consists predominately of Swedish dams, but it also includes moraine core dams located in the rest of Scandinavia, in North America, Russia and Australia. The investigation shows that a coarsely graded filter, grading instability of the core and filter, and high susceptibility for filter segregation are properties that are over-represented and possibly indicative for moraine (till) core dams with performance history of internal erosion.

  • 44.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sustainability, waste processing and secondary resources2017Inngår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 126, nr 1-2, s. 1-2Artikkel i tidsskrift (Fagfellevurdert)
  • 45.
    Sellin, Jessica
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Industriell ekologi.
    Särhållning av gruvavfall med avseende på syrabildande potential: en studie av svenska sulfidmalmsgruvor2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Gruvavfall utgör över 80 % av den totala mängden avfall i Sverige. Avfallet från gruvindustrin kan påverka våra ekosystem negativt om tungmetaller och försurande ämnen lämnar materialet. I Sverige utgör avfall från sulfidmalmer störst risk för miljön eftersom det innehåller mineral som genom kontakt med luft vittrar och producerar surt och metallhaltigt lakvatten. Efterbehandling av dessa material är viktigt för att förhindra läckage till omgivningen. Eftersom efterbehandling är en kostsam process hänvisar Stiftelsen för Miljöstrategisk Forskning i första hand till särhållning av materialet med avseende på syrabildande potential. I denna studie har undersökts vilka förbättringsmöjligheter som finns för särhållning av avfall inom gruvindustrin. Arbetet har utförts genom studier av miljörapporter, avfallshanteringsplaner samt kommunikation med Länsstyrelser och Naturvårdsverket.

    De förbättringsmöjligheter som i denna studie identifierats rör utformning av kriterierna för klassning av syrabildande potential samt metodik vid bestämning av syrabildande potential. Inför framtida särhållning bör kriterierna för vad som klassas som icke syrabildande material skärpas såtillvida att de bättre överensstämmer med definitionen för inert avfall i utvinningsavfallsförordningen. Om kriterierna formuleras som villkor tilldelade genom Mark- och miljödomstolen kan det dessutom föreligga större möjligheter till uppföljning och undersökning av metodikens lämplighet för att hindra spridning av surt och metallhaltigt lakvatten. Metodiken för identifiering av icke syrabildande material kan förbättras genom att borrkax analyseras under produktionens gång. Dessutom bör lakvattnet från deponierna med icke syrabildande material analyseras för att kunna följa upp åtgärdernas verkan. Denna studie visar även att det idag finns mer potentiellt syrabildande anrikningssand än gråberg på upplag, vilket indikerar att teknologin för att särhålla anrikningssand bör förbättras. 

  • 46. Uotinen, L. K. T.
    et al.
    Korpi, E.
    Hartikainen, A.
    Yorke, R.
    Antikainen, J.
    Johansson, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Rinne, M.
    A method to downscale joint surface roughness and to create replica series using 3D printed molds2017Inngår i: 13th ISRM International Congress of Rock Mechanics, International Society for Rock Mechanics , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to determine the in-situ shear strength of rock joints, large scale testing is required. However, this is both expensive and difficult to execute. One possible method to overcome this may be to use photogrammetry to capture large joint surface roughness in-situ and downscale it to replica samples, which could be sheared in laboratory. In this paper, as a first part in such a method, a technique to digitize surface roughness and to produce replica samples for laboratory shear testing from a larger joint sample are presented. First, a thin granitic rock slice with dimensions of 1.75 m x 0.95 m of granitic intact rock was chosen for the study. The joint surface is fresh and created through tensile induced splitting. The large joint sample is digitized using photogrammetry. Then, one fullscale 1.7 m x 0.6 m geometry is cropped from the digitized joint geometry and then subsamples at 10x, 7.5x, 5x, 2.5x and 1x scales. All sub-geometries are scaled down digitally to produce 0.17 m by 0.06 m geometries. The geometries are used to make casting molds both positive and negative to produce samples with perfect matedness. The casting molds are 3D printed in polylactic acid plastic and C60/75 concrete is cast to produce a replica series. In addition to the creation of this replica series, two pilot replicas are also tested using a portable shear box with a 0.5 MPa normal pressure. The results from the pilot rounds are presented and discussed. Finally, suggestions for future research are given.

  • 47.
    Vikström, Hanna
    et al.
    Global Energy Systems, Department of Earth Sciences, Uppsala University.
    Davidsson, Simon
    Uppsala Universitet.
    Höök, Mikael
    Uppsala Universitet.
    Lithium availability and future production outlooks2013Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 110, s. 252-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lithium is a highly interesting metal, in part due to the increasing interest in lithium-ion batteries. Several recent studies have used different methods to estimate whether the lithium production can meet an increasing demand, especially from the transport sector, where lithium-ion batteries are the most likely technology for electric cars. The reserve and resource estimates of lithium vary greatly between different studies and the question whether the annual production rates of lithium can meet a growing demand is seldom adequately explained. This study presents a review and compilation of recent estimates of quantities of lithium available for exploitation and discusses the uncertainty and differences between these estimates. Also, mathematical curve fitting models are used to estimate possible future annual production rates. This estimation of possible production rates are compared to a potential increased demand of lithium if the International Energy Agency's Blue Map Scenarios are fulfilled regarding electrification of the car fleet. We find that the availability of lithium could in fact be a problem for fulfilling this scenario if lithium-ion batteries are to be used. This indicates that other battery technologies might have to be implemented for enabling an electrification of road transports.

  • 48. Xueyan, Zhang
    et al.
    Yunfeng, Hu
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik (stängd 20110301).
    Dafang, Zhuang
    Yongqing, Qi
    Xin, Ma
    NDVI spatial pattern and its differentiation on the Mongolian Plateau2009Inngår i: JOURNAL OF GEOGRAPHICAL SCIENCES, ISSN 1009-637X, Vol. 19, nr 4, s. 403-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    GIMMS NDVI database and geo-statistics were used to depict the spatial distribution and temporal stability of NDVI on the Mongolian Plateau. The results demonstrated that: (1) Regions of interest with high NDVI indices were distributed primarily in forested mountainous regions of the east and the north, areas with low NDVI indices were primarily distributed in the Gobi desert regions of the west and the southwest, and areas with moderate NDVI values were mainly distributed in a middle steppe strap from northwest to southeast. (2) The maximum NDVI values maintained for the past 22 years showed little variation. The average NDVI variance coefficient for the 22-year period was 15.2%. (3) NDVI distribution and vegetation cover showed spatial autocorrelations on a global scale. NDVI patterns from the vegetation cover also demonstrated anisotropy; a higher positive spatial correlation was indicated in a NW-SE direction, which suggested that vegetation cover in a NW-SE direction maintained increased integrity, and vegetation assemblage was mainly distributed in the same specific direction. (4) The NDVI spatial distribution was mainly controlled by structural factors, 88.7% of the total spatial variation was influenced by structural and 11.3% by random factors. And the global autocorrelation distance was 1178 km, and the average vegetation patch length (NW-SE) to width (NE-SW) ratio was approximately 2.4:1.0.

  • 49.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lannu
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Stress effects on nuclide transport in fractured rocks: A numerical study2010Inngår i: ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 2010, s. 783-786Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The main objective of this study was to investigate the influence of stresses on radioactive nuclide transport in fractured rocks, based on Discrete Element Method (DEM) and a particle tracking approach. Matrix diffusion was also considered in the transport simulation. The results show that stresses not only influence the particle residence time in fracture network, but also change the particle transport paths significantly.

  • 50.
    Zimmerman, R.W.
    et al.
    Dept. of Earth Science/Engineering, Imperial College, London.
    Al-Yaarubi, A
    Pain, C.C
    Grattoni, C.A
    Non-linear regimes of fluid flow in rock fractures2004Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, nr 3, s. 384-384Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have conducted high-resolution Navier-Stokes simulations and laboratory measurements of fluid flow in a natural sandstone fracture. First, epoxy casts were made of the two opposing fracture surfaces. The surface profiles of the two surfaces were then measured at a vertical resolution of ±2 μm, every 20 μm in the x and y-directions, over 2 cm × 2 cm regions of the fracture. These data were then used to create a finite-element mesh for the fracture void space, and the Navier-Stokes equations were solved within this domain. Flow experiments were also conducted within the same fracture casts, over a range of flowrates. The simulations confirm the existence of a weak inertia regime for Reynolds numbers in the range of 1-10, in which the non-Darcy pressure drop varies with the cube of the flowrate. Although of theoretical interest, this effect is, however, probably too small to be of engineering interest. At Reynolds numbers above about 20, both the simulations and experiments exhibit a Forchheimer-type regime, in which the non-Darcy pressure drop is quadratic in the flowrate.

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