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  • 51.
    Nickman, Alireza
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH/ The Royal Institute of Technology.
    Modeling moisture and temperature dynamics in road structure during winter conditionsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Excess moisture significantly impact durability and sustainability of road components especially in cold regions. To improve understanding of moisture dynamics in roads with drainage system, hourly measured moisture content, soil temperature and groundwater level data during a 3-year period from a test site in Växjö, Sothern Sweden were utilized. Seasonal and manipulated changes in the groundwater level and moisture dynamics were observed that describe extreme conditions providing extra moisture to the upper layers of road. CoupModel was used to estimate mass and heat balance in four depths of two spots of the road section. Good performances of the model were achieved in calculation of the soil moisture in different depths. Soil water retention curve parameters were sensitive to constrain criteria which demonstrate importance of soil texture in controlling moisture dynamics. Model could properly capture temperature dynamic during winter time but simulated excess evaporation from soil layers reduced performance of model in the estimation of temperature during summer The combined monitoring and modelling of physical conditions in the road structure will be highly relevant to help decision makers and road engineers to avoid moisture in road structures and to also identify crucial events from meteorological data.

    Fulltekst tilgjengelig fra 2018-08-31 15:24
  • 52.
    Nickman, Alireza
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH/ The Royal Institute of Technology.
    Road disasters? Modeling and assessment of Swedish roads within crucial climate conditions2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    An efficient maintenance of roads to ensure high accessibility and durability of the transport capacity requires an understanding of how the hydrological response depends on both the road and the landscape characteristics. New methods and data were used to identify and explain interaction between roads and surrounding environment and their influence on hydrologic responses both in watershed scale and road-section scale. In the watershed scale, flood hazard probability was made with reference to the most influential physical catchment descriptors and road characteristics. Additionally, a physical based model was used to estimate the effect of road topography on the hydrological responses of 20 watersheds to storms with different intensities. A simple method was developed and discussed to address flood risk probability in the road-stream crossings concerning the correlation between the quantities of the physical catchment descriptors and occurrence/absence of flooding. The most influential factors in describing the probability of flooding along the roads were topographic wetness index, soil properties, road density and channel slopes. A detailed study of simulated flow duration curves showed differences between the 20 watersheds for three different storms based on topography with and without roads. An increase in peak flow and reduced time to pick occurred with existence of roads and increased storm intensity.In the road-section scale, an uncertainty-based simulation approach was used to identify the most influencing processes in controlling the dynamics of the groundwater level. A model (CoupModel) set up with four different geological stratifications was made to model two positions in a slope upstream of a road with drainage pipes and ditches. Results from the simulations indicate the significance of precipitation rate, road drainage and position in hillslope, and soil properties and stratifications in controlling groundwater levels. The same model was also applied to simulate soil moisture and temperature dynamics in two road sections by using groundwater and climate data. Porous media properties were obtained as statistical distribution function that provided the best performance of moisture and temperature dynamic in the road layers and underlying soil.

  • 53.
    Nickman, Alireza
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH/ The Royal Institute of Technology.
    Uncertainty based approach to simulate groundwater levels in a hillslope upstream of a roadManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Knowledge of the processes governing groundwater dynamics in the areas close to roads is important for sustainable road infrastructure in the face of a changing climate. This study established an uncertainty based approach to simulate groundwater oscillations in a hillslope upstream of a road by using a process based model. Four different soil configurations were analyzed in CoupModel to simulate groundwater dynamics in presence of a road drainage system by implementation of meteorological data as driving factors. An approach similar to GLUE method was applied to analyze the statistical performance of the simulated groundwater level versus high resolution measured groundwater level dynamics. Results of the simulations indicate deviations in simulated results due to different soil stratifications. Uncertainties resulted from the lack of precise information about the geological structure of the site are important contributors to deviated simulation results. Different scenarios showed different model performances in which a simpler soil profile describes better the groundwater dynamics when it is closer to the road drainage system while a more complicated soil profile better describes groundwater dynamics in undisturbed soils. Correlation between hydraulic conductivity of each layer and the model performance was discussed. The results also indicate significance of variables such as physical drainage characteristics of the road in governing level of saturations also the position of the road structure in a hillslope. Texture (hydraulic conductivity) of the soil layers that fluctuation of groundwater occurs in those layers and types of modifications that have been done due to road construction are important driving factors. These factors are suggested as suitable indicators for designing an early warning system based on physical characteristics of a road site.

  • 54.
    Nickman, Alireza
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH/ The Royal Institute of Technology.
    Uncertainty based approach to simulate groundwater levels in a hillslope upstream of a roadManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Knowledge of the processes governing groundwater dynamics in the areas close to roads is important for sustainable road infrastructure in the face of a changing climate. This study established an uncertainty based approach to simulate groundwater oscillations in a hillslope upstream of a road by using a process based model. Four different soil configurations were analyzed in CoupModel to simulate groundwater dynamics in presence of a road drainage system by implementation of meteorological data as driving factors. An approach similar to GLUE method was applied to analyze the statistical performance of the simulated groundwater level versus high resolution measured groundwater level dynamics. Results of the simulations indicate deviations in simulated results due to different soil stratifications. Uncertainties resulted from the lack of precise information about the geological structure of the site are important contributors to deviated simulation results. Different scenarios showed different model performances in which a simpler soil profile describes better the groundwater dynamics when it is closer to the road drainage system while a more complicated soil profile better describes groundwater dynamics in undisturbed soils. Correlation between hydraulic conductivity of each layer and the model performance was discussed. The results also indicate significance of variables such as physical drainage characteristics of the road in governing level of saturations also the position of the road structure in a hillslope. Texture (hydraulic conductivity) of the soil layers that fluctuation of groundwater occurs in those layers and types of modifications that have been done due to road construction are important driving factors. These factors are suggested as suitable indicators for designing an early warning system based on physical characteristics of a road site.

    Fulltekst tilgjengelig fra 2018-08-31 14:00
  • 55.
    Nygren, Anton
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Nordenskjöld, Edvard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Östblom, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Groundwater occurrence and quality in Bulawayo province, Zimbabwe2016Student paper other, 10 poäng / 15 hpOppgave
    Abstract [en]

    This study focused on determining the groundwater flow paths in the crystalline subsurface rocks of the Bulawayo metropolitan, Zimbabwe, through analysing the discontinuities of the electrical properties of the ground, as well as in the magnetic field of the underlying rocks. Further, borehole water quality was analysed by measuring and mapping several chemical parameters, specifically TDS, salinity and the electrical conductivity. The electrical and magnetic anomalies were measured at two field sites within the Bulawayo province, the Harry Allen Golf Course and the Barbour Fields dumpsite, while 120 boreholes were sampled for water quality in a large part the province. Two magnetometers were used to measure the magnetic field and the time and location of the measurements, which resulted, after processing in SURFER, into the magnetic field map of these areas. This was used, in conjunction with the geologic map of the Bulawayo province, in order to determine useful locations for the electrical resistivity surveys. These included electrical resistivity tomography and vertical electrical sounding and were performed with an earth resistivity/induced polarization (IP) meter in order to measure the electrical resistivity of the ground. Inverse modelling was used in the RES2DINV software program to produce the topographic image of resistivity. The results for the borehole sampling showed that the maps for the three chemical parameters were very similar, with the western and northern parts of the mapped area displaying higher concentration values. The results of the electrical resistivity surveying showed probable areas of groundwater flow with its relationship to electric conductivity.

  • 56.
    Reynisson, Jón Ágúst
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Performance of mobile GIS in conjunction withinternet bandwidth in rural areas2015Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    The emerging techniques of mobile GIS applications, its abilities and its implied limitations ofinternet connections is the main subject in this study. Many of the operations that mobile devicesuse are dependent on mobile internet connectivity. Therefore the potential for it in well connectedareas is great but how would they function in less connected areas? Mobile GIS, which is todaymostly used in devices as smart phones and tablets, has internet connectivity for uploading anddownloading files and other data. Mobile GIS is also dependent on location-based services thatenable the device to get information or take action from the current location of the device. Thisresearch examines the potential usage of mobile GIS in conjunction with the bandwidth of wirelesstechnologies. It is important to study this issue to see if mobile applications can perform upload anddownload tasks within reasonable time in poor mobile coverage. To test the possibilities of mobileGIS in rural areas a test environment is set up in a mobile GIS application for septic tanks. Thetesting is performed by uploading and downloading data with real GIS actions from pre-selectedlocations that have low mobile coverage. The study is comparing the measurements with a scale ofacceptable time for download and upload. The result for registering (uploading) a new point inmobile GIS with three small images is that it requires at least 330 Kbit/s connection to transfer thedata within acceptable time. The results for uploading data without images and downloading giveseven better results and are not as dependent on a good connection for transferring within acceptabletime. The conclusion is that mobile gis applications are able to run within acceptable time measuresin rural areas. The results and other sources were used to make general guidelines for mobile GISapplications for use in rural areas.

  • 57.
    Riedesel, Philipp
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Tilt sensing with low-cost inertial measurement units (IMUs): Sensor calibration, accuracy specifications and application range2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Many surveying engineering applications require the knowledge of the orientation parameters of instruments. One can use inertial measurement units (IMUs) to determine that. IMUs are combinations of several inertial sensors and comprise at least an accelerometer and a gyroscope. Therefore, they can detect accelerations and angular rates in a three-dimensional space. As micro-electro-mechanical systems, the sensors are increasingly getting smaller and lighter, but without being reduced in their accuracy. The smaller size facilitates diverse placing of the sensors, which allows a variety of uses. Moreover, several low-cost IMUs have been devised since the development of single-board computers.

    The main objectives of this work are to determine tilts using a low-cost IMU, and the accuracy of the sensor. Furthermore, it studies general IMU applications in surveying engineering, and examines whether low-cost versions are applicable.

    To fulfil the objectives, the study was based on a selected low-cost IMU. Two programs were developed as part of this work. One was to control the sensor and the other, to calculate the tilts and analyse the data. The IMU was mounted in front of the objective of the total station and aligned in different reference orientations. All measurements were performed under controlled thermal conditions. Thereby, it was ensured that no falsifications could appear due to ambient temperature influences. As a first step, the sensor calibration process was completed. It helped determine the signal offset parameter and their time-dependent change. The calibration was done using two present methods, the six-position and the multi-position methods. The calibrated IMU helped determine the tilts. This was done in the case of the accelerometer via trigonometric functions, which allowed an absolute orientation statement. In contrast, the gyroscope provided relative orientation with the multiplication of the detected angular variance and the time that passed. After that, a target-actual comparison with the reference information of the total station helped determine the external accuracy of the tilt from the IMU. Moreover, multiple measurements could give a statement of the internal accuracy. Finally, the Kalman Filter was added to smooth out the sensor data and combine it in real-time.

    The calibration methods showed similar results, and it was striking that the sensors did not show the expected drifts. The reason could be related to a pre-calibration by the manufacturer. On the one hand, the used IMU showed differences in the total station alignments in the order of 0.798° for the accelerometer and up to 4.3° for the gyroscope with the calibrated data. On the other, the differences in repeated measurements were at 0.024° for the accelerometer and 0.5° for the gyroscope.

    It was figured out different possible applications of IMUs in surveying engineering. Among other things, these included orientation monitoring of sensor platforms or the determination of the external orientation of unmanned aerial systems. For these applications, the usability depends on the achievable accuracy. In the case of the IMU chosen in this study, the proven accuracy is too inaccurate for these applications.

    There is a need for further investigation because the use of another sensor type may rectify the insufficient accuracy problem. Moreover, to achieve better accuracies and to make it possible to use the IMU in different ambient temperatures, the temperature influence must be determined.

  • 58.
    Sandgren, Marie
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Ektun, Hans
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    GIS för fastighetsrättsliga frågor inom energibranschen2006Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The purpose with the work is to study Fortums activities with hydro power plants, dams and reservoirs mainly in a premise jurisdictional perspective and to show how GIS would be a helpful tool for the future.

    A great deal of the information that the Generation Hydro-division at Fortum are managing have a spatial element. That means that it is possible to spatially join this information to a geographical polygon, line or point. This information is today gathered from several different sources, such as files, paper maps and digital data of several kinds. A Geographic Information System (GIS), as and aid besides the ordinary tools should be an effective support in the everyday work with questions of a premise jurisdictional nature.

    The goal of this work is to account for how to organize, present and analyse geographic information. We will show how to link from the map to traditional tools such as calculation- and register programs. Linking to documents of different formats and to pictures will also be demonstrated.

    Gathered and processed data in different formats and from different sources will result in a GIS-application overlooking two separate control areas. For the lower parts of the river Ljusnan in the municipalities of Bollnäs and Söderhamn it will be accounted for the handling of hydro power plants. The other area includes the municipalities of Arvika and Eda in the county of Värmland, in which the handling of dams and reservoirs also will be incuded. In the attempt to give suggestions of different solutions the two areas diverge somewhat in the matter of drawing manners and scales.

  • 59.
    Shirabe, Takeshi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö. Vienna University of Technology, Austria.
    A heuristic for the maximum value region problem in raster space2011Inngår i: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 25, nr 7, 1097-1116 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From a single-attribute raster layer in which each cell is assigned a numerical value, a connected set of a specified number of cells that has the maximum (or minimum) total value is selected. This is a highly common decision problem in the context of raster-based geographic information systems (GIS) and seems general enough to deserve inclusion in the standard functionality of such systems. Yet it is a computationally difficult optimization problem, for which no efficient exact solution method has been found. This article presents a new dynamic programming-based heuristic method for the problem. Its performance is tested with randomly generated raster layers with various degrees of spatial autocorrelation. Results suggest that the proposed heuristic is a promising alternative to the existing integer programming-based exact method, as it can handle significantly larger raster data with fair accuracy.

  • 60.
    Stenström, Petter
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Hydraulics and mixing in the Hudson River estuary: A numerical model study of tidal variations during neap tide conditions2004Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 109, nr C4, C04019- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three-dimensional numerical modeling is performed to study intratidal and along-channel variability in stratification and mixing in the Hudson River estuary. The modeled fields show good agreement with observations, both qualitatively and quantitatively. Estuarine circulation dominates the mean fields, and intratidal variability is dominated by tidal straining that acts to strengthen the stratification during ebb and weaken it during flood. Mixing is mainly confined to a bottom layer during flood but occurs higher up in the water column during ebb. Mixing across the halocline shows marked along-channel variability due to bathymetric effects. During ebb, mixing occurs preferentially at an abrupt channel expansion seaward of a channel constriction at the George Washington Bridge, as predicted by Chant and Wilson [2000]. The salt flux across the halocline in this region, averaged over ebb, exceeds 5x10(-4) kg m(-2) s(-1), a factor of 3 greater than the along-channel average. Increased residence time of tracers should be expected in this region due to the strong mixing but also due to observed secondary circulation [Chant and Wilson, 1997]. Mixing across the halocline during flood is small, except for early flood, before the well-mixed bottom layer is developed. Mixing is then localized to the landward slope of sills.

  • 61.
    Ström, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A geophysical study of the Mertainen area: Modelling and interpretation of primarily aeromagnetic data2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Nautanen Deformation Zone, is a prominent deformation zone in the Malmfälten area, which is of importance to understand for mineral exploration purposes. In spite of diverse geophysical data being available in Malmfälten and the good correlation between airborne measurements and geological observations, the area has not been fully investigated in detail using the aforementioned available data. A geological feature in connection with the Mertainen magnetite-breccia apatite iron ore deposit has been studied. Methods include the study of geological maps, the study of analytic signals of magnetic and gravity data, data processing, potential field- and 3D modelling and the interpretation of aforementioned models. Based on the observed and modelled data a fold structure has been detected in connection with Mertainen, and several mineralizations are believed to be structurally related to this fold. Furthermore, a potential mineralization structurally related with the fold has been detected, though it is quite likely that it isn't economically viable.

  • 62.
    Tafesse, Solomon
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Physical properties of coarse particles in till coupled to bedrock composition based on new 3D image analysis method2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The physical properties of the coarse fraction of the till (0.4 to 20 cm) and the surface boulders have been studied at two different sites in Sweden. The research work included: development of a new image analysis software for 3D size and shape measurements of particles; lithological analysis on multiple size fractions in till and magnetic susceptibility survey on coarse till clasts, surface boulders and local bedrock.

    The new 3D image analysis method provides an enormous amount of size and shape data for each particle in the coarse fraction (2 to 20 cm) in till. The method is suitable for field study, cost effective and the software is executable in Matlab. The field imaging method together with the image analysis software give non subjective results of size and shape of coarse particles and makes it feasible and easy to study representative sample size, which is one tonne for testing clasts of size up to 20 cm.

    The lithological analysis of the multiple size fraction of the till clasts has been investigated on six different size fractions of the till (0.4 to 20 cm); the result of the different samples from the two sites shows that this method can potentially be used as a stratigraphic tool in the areas where there is no unique indicator lithologies.

    The magnetic susceptibility has been made on the surface boulders, the 6-20 cm till fraction and on insitu bedrock outcrops near to the study sites. The method has good potential for determining stratigraphic relationships between different till units as well as for determining the provenance ofcoarse clasts and surface boulders.

  • 63.
    Tafesse, Solomon
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Fernlund, Joanne
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Bergholm, Fredrik
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Digital sieving-Matlab based 3-D image analysis2012Inngår i: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 137-138, 74-84 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new image analysis technique for determining the three-dimensional size and shape distribution of coarse particles has been developed. It entails acquiring a pair of images, one each of the maximum and minimum projected area of the particles. Glow-In-the-Dark beads were used to create luminous background, thus it is named the GID method. In this study the size and shape distribution of four coarse-grained samples, size varies from 2 to 20. cm, have been analyzed. The size distribution of the samples obtained from the GID analysis is comparable to sieve analysis results, and has an extra advantage of being applicable in the field. The algorithm was developed in Matlab; therefore users could make some optimization in the program to meet their own needs as the program code is open source.

  • 64.
    Tafesse, Solomon
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Fernlund, Joanne M. Robison
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Repeatability of GID Image-analysis method for assessment size, shape and angularity of coarse particlesInngår i: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917Artikkel i tidsskrift (Annet vitenskapelig)
  • 65.
    Tafesse, Solomon
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Fernlund, Joanne M. Robison
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Sun, Wenjuan
    Bergholm, Fredrik
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Evaluation of image analysis methods for the quantification of particle angularityInngår i: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091Artikkel i tidsskrift (Annet vitenskapelig)
  • 66.
    Tian, Liang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Yang, Zhibing
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Fagerlund, Fritjof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Niemi, Auli
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Effects of permeability heterogeneity on CO2 injectivity and storage efficiency coefficient2016Inngår i: Greenhouse Gases: Science and Technology, E-ISSN 2152-3878, Vol. 6, nr 1, 112-124 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the dependency of CO2 storage efficiency coefficient (E) and injectivity index (Iinj) on the geostatistical parameters of the permeability field. CO2 injection simulations are conducted for multiple realizations of log-normally distributed permeability fields parameterized by log permeability standard deviation (𝜎) and dimensionless horizontal correlation length (𝜆). Results show that the injectivity index increases with increasing 𝜆, the magnitude of the effect depending on 𝜎. Increasing 𝜎 leads to poorer injectivity for cases with small 𝜆, but improves injectivity when 𝜆 is large. Further analysis indicates that the enhancing effect of 𝜎 on injectivity can be attributed to cases with channelized flow, while the decrease effect of 𝜎 is seen in more dispersive flow regime. The dependence of injectivity on both 𝜆 and 𝜎 is captured with a linear correlation between Iinj and a parameter group (𝜆/ξ)𝜎, where ξ is a dimensionless scaling parameter. The storage efficiency coefficient, on the other hand, decreases with both increasing 𝜎 and 𝜆, and a simple linear fit is found between E and the parameter group 𝜆𝜎2, a well-established heterogeneity parameter group describing e.g. macro-dispersivity in solute transport studies. The above relationships provide potentially useful tools for preliminary evaluation of a site. Future studies should address the validity of the relationships in alternative injection scenarios and domain geometries.

  • 67.
    Tian, Liang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Yang, Zhibing
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
    Jung, Byeongju
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources (KIGAM).
    Joodaki, Saba
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Erlström, Mikael
    Geological Survey of Sweden.
    Zhou, Quanlin
    Lawrence Berkeley National Laboratory.
    Niemi, Auli
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Integrated simulations of CO2 spreading and pressure response in the multilayer saline aquifer of South Scania Site, Sweden2016Inngår i: Greenhouse Gases: Science and Technology, E-ISSN 2152-3878, Vol. 6, nr 4, 531-545 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An integrated modeling approach/workflow, in which a series of mathematical models of different levels of complexity are applied to evaluate the geological storage capacity of the Scania Site, southwest Sweden, is presented. The storage formation at the site is a layered formation limited by bounding fault zones, and injection is assumed to take place from one existing deep borehole into all layers. A semi-analytical model for two-phase flow is first used to evaluate the pressure response and related parameter sensitivity, as well as the first estimates of acceptable injection rates. These results are then used to guide the more detailed numerical simulations that address both pressure response and plume migration. The vertical equilibrium (VE) model is used to obtain a preliminary understanding of the plume migration with a larger number of simulations. Finally the full TOUGH2/ECO2N simulations are performed for the most detailed analyses of pressure responses and plume migration. Throughout, the results of the different modeling approaches are compared against each other. It is concluded that the key limiting factor for the storage capacity at the site in the injection scenario considered is the fast CO2 migration within the high permeability layer. Future studies can address alternative injection scenarios, including horizontal injection wells and injection to other layers than the high permeability layer.

  • 68.
    Tong, Fuguo
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Numerical modeling of coupled thermo-hydro-mechanical processes in geological porous media2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Coupled Thermo-Hydro-Mechanical (THM) behavior in geological porous media has been a subject of great interest in many geoengineering disciplines. Many attempts have been made to develop numerical prediction capabilities associated with topics such as the movement of pollutant plumes, gas injection, energy storage, geothermal energy extraction, and safety assessment of repositories for radioactive waste and spent nuclear fuel. This thesis presents a new numerical modeling approach and a new computer code for simulating coupled THM behavior in geological porous media in general, and compacted bentonite clays in particular, as buffer materials in underground radioactive waste repositories.

    New governing equations were derived according to the theory of mixtures, considering interactions among solid-phase deformation, flows of water and gases, heat transport, and phase change of water. For three-dimensional problems, eight governing equations were formulated to describe the coupled THM processes.

    A new thermal conductivity model was developed to predict the thermal conductivity of geological porous media as composite mixtures. The proposed model considers the combined effects of solid mineral composition, temperature, liquid saturation degree, porosity and pressure on the effective thermal conductivity of the porous media. The predicted results agree well with the experimental data for MX80 bentonite.

    A new water retention curve model was developed to predict the suction-saturation behavior of the geological porous media, as a function of suction, effective saturated degree, temperature, porosity, pore-gas pressure, and the rate of saturation degree change with time. The model was verified against experimental data of the FEBEX bentonite, with good agreement between measured and calculated results.

    A new finite element code (ROLG) was developed for modeling fully coupled thermo-hydro-mechanical processes in geological porous media. The new code was validated against several analytical solutions and experiments, and was applied to simulate the large scale in-situ Canister Retrieval Test (CRT) at Äspö Hard Rock Laboratory, SKB, Sweden, with good agreement between measured and predicted results. The results are useful for performance and safety assessments of radioactive waste repositories.

  • 69.
    Tong, Fuguo
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Bin, Tian
    A Water Retention Curve Model for the Simulation of Coupled Thermo-Hydro-Mechanical Processes in Geological Porous Media2012Inngår i: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 91, nr 2, 509-530 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a new water retention curve (WRC) model for the simulation of coupled thermo-hydro-mechanical processes in geological porous media. The model simultaneously considers the impact of porosity and temperature on suction, for both wetting processes and drying processes. The model is based on an idealization of porous geological media as having an isotropic and homogeneous microscopic pore structure. Suction is expressed as a function of degree of saturation, porosity, surface tension of the water-air interface, and the length of air bubble perimeter of the pores per unit area on a random 2D cross-section of the medium. The tension of water-air interface is written as a function of temperature, and the length of perimeter of the water-air interface of the pores becomes a function of porosity and degree of saturation. The final equation of the new WRC is a function of suction, effective degree of saturation, temperature, porosity, pore-gas pressure, and the rate of degree of saturation change with time for both wetting and drying processes. The model was used to fit experimental data of the FEBEX bentonite, with good agreements between measured and calculated results.

  • 70. Tournassat, Christophe
    et al.
    Bourg, Ian C.
    Holmboe, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sposito, Garrison
    Steefel, Carl I.
    Molecular dynamics simulations of anion exclusion in clay interlayer nanopores2016Inngår i: Clays and clay minerals, ISSN 0009-8604, E-ISSN 1552-8367, Vol. 64, nr 4, 374-388 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aqueous chemistry of water films confined between clay mineral surfaces remains an important unknown in predictions of radioelement migration from radioactive waste repositories. This issue is particularly important in the case of long-lived anionic radioisotopes (129I , 99TcO4 , 36Cl) which interact with clay minerals primarily by anion exclusion. For example, models of ion migration in clayey media do not agree as to whether anions are completely or partially excluded from clay interlayer nanopores. In the present study, this key issue was addressed for Cl using MD simulations for a range of nanopore widths (6 to 15 Å) overlapping the range of average pore widths that exists in engineered clay barriers. The MD simulation results were compared with the predictions of a thermodynamic model (Donnan Equilibrium model) and two pore-scale models based on the Poisson-Boltzmann equation under the assumption that interlayer water behaves as bulk liquid water. The simulations confirmed that anion exclusion from clay interlayers is greater than predicted by the pore-scale models, particularly at the smallest pore size examined. This greater anion exclusion stems from Cl being more weakly solvated in nano-confined water than it is in bulk liquid water. Anion exclusion predictions based on the PoissonBoltzmann equation were consistent with the MD simulation results, however, if the predictions included an ion closest approach distance to the clay mineral surface on the order of 2.0 0.8 Å. These findings suggest that clay interlayers approach a state of complete anion exclusion (hence, ideal semi-permeable membrane properties) at a pore width of 4.2 +/- 1.5 Å. 

  • 71. Tsang, C. F.
    et al.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Stephansson, O.
    Kautsky, F.
    The DECOVALEX III project: A summary of activities and lessons learned2005Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, nr 5-6, 593-610 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Initiated in 1992, the DECOVALEX project is an international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical (THM) processes in geologic systems. The project has made important scientific achievements through three stages and is progressing in its fourth stage. It has played a key role in the development of mathematical modeling and in situ testing of coupled THM processes in fractured rock and buffer/backfill materials, a subject of importance for performance assessment of radioactive waste geologic repositories. This paper summarizes studies under the most recent stage of the project, DECOVALEX III (2000-2003). These studies include those of two major field experiments: (a) the FEBEX experiment at Grimsel, Switzerland, investigating coupled THM processes in a crystalline rock-bentonite system, and (b) the Drift Scale Test (DST) experiment at Yucca Mountain, Nevada, investigating coupled THM processes in unsaturated tuff. These are two of the largest multiyear heater tests undertaken to date for the study of coupled THM processes in geological systems. In addition, three so-called benchmark tests are also studied to evaluate the impact of coupled THM processes under different scenarios and geometries. Within the DECOVALEX project, multiple research teams participated in each of the studies, using different approaches and computer codes. Comparisons of results have provided insight into coupled THM processes, which in turn has stimulated further development of our modeling capabilities. Lessons learned from these studies are discussed. The scientific advances and enhanced insight gained through this kind of international cooperation illustrate the effectiveness of the DECOVALEX project.

  • 72. Tsang, Chin-Fu
    et al.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Tsang, Yvonne
    Hydrologic issues associated with nuclear waste repositories2015Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, nr 9, 6923-6972 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Significant progress in hydrology, especially in subsurface flow and solute transport, has been made over the last 35 years because of sustained interest in underground nuclear waste repositories. The present paper provides an overview of the key hydrologic issues involved, and to highlight advances in their understanding and treatment because of these efforts. The focus is not on the development of radioactive waste repositories and their safety assessment, but instead on the advances in hydrologic science that have emerged from such studies. Work and results associated with three rock types, which are being considered to host the repositories, are reviewed, with a different emphasis for each rock type. The first rock type is fractured crystalline rock, for which the discussion will be mainly on flow and transport in saturated fractured rock. The second rock type is unsaturated tuff, for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository. The third rock type is clay-rich formations, whose permeability is very low in an undisturbed state. In this case, the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances; i.e., on the relevant coupled thermo-hydro-mechanical processes. The extensive research results, especially those from multiyear large-scale underground research laboratory investigations, represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research.

  • 73.
    Wörman, Anders
    et al.
    Environmental Physics Group, Swedish University of Agricultural Sciences, Sweden.
    Marklund, Lars
    Environmental Physics Group, Swedish University of Agricultural Sciences, Sweden.
    Xu, Shulan
    Swedish Radiation Protection Authority, Sweden.
    Dverstorp, Björn
    Swedish Radiation Protection Authority, Sweden.
    Impact of repository depth on residence times for leaking radionuclides in land-based surface water2006Inngår i: Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The multiple scales of landscape topography produces a wide distribution of groundwater circulation cells that control the hydro-geological environments surrounding geological repositories for nuclear waste. The largest circulation cells tend to discharge water into major river reaches, large freshwater systems or the nearby Sea. We investigated numerically the release of radionuclides from repositories placed in bedrock with depths between 100 to 2,000 meters in a Swedish coastal area and found that, leakage from the deeper positions emerges primarily in the major aquatic systems. In effect, radionuclides from the deeper repositories are more rapidly transported towards the Sea by the stream system compared to leakage from more shallow repositories. The release from the shallower repositories is significantly retained in the initial stage of the transport in the (superficial) landscape because the discharge occurs in or near low-order streams with high retention characteristics. This retention and residence time for radioactivity in the landscape control radiological doses to biota and can, thus, be expected to constitute an essential part of an associated risk evaluation.

  • 74.
    Wörman, Anders
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Marklund, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Xu, Shulan
    Dverstorp, Björn
    Implication of physical and chemical retention on radioactive land-area in the biosphere2008Inngår i: Proceedings of the int. Conference on Radioecology and Environmental Radioactivity / [ed] Per Strand, Justin Brown and Torun Jolle, 2008Konferansepaper (Fagfellevurdert)
  • 75.
    Xia, Xiaolin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    A Comparison Study on a Set of Space Syntax based Methods: Applying metric, topological and angular analysis to natural streets, axial lines and axial segments2013Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Recently, there has been an increasing interest in looking at urban environment as a complex system. More and more researchers are paying attention to the study of the configuration of urban space as well as human social activities within it. It has been found that correlation exists between the morphological properties of urban street network and observed human social movement patterns. This correlation implies that the influence of urban configurations on human social movements is no longer only revealed from the sense of metric distance, but also revealed from topological and geometrical perspectives. Metric distances, topological relationships and angular changes between streets should be considered when applying space syntax analysis to an urban street network. This thesis is mainly focused on the comparison among metric, topological and angular analyses based on three kinds of urban street representation models: natural streets, axial lines and axial segments. Four study areas (London, Paris, Manhattan and San Francisco) were picked up for empirical study. In the study, space syntax measures were calculated for different combinations of analytical methods and street models. These theoretical space syntax accessibility measures (connectivity, integration and choice) were correlated to the corresponding practical human movement to evaluate the correlations. Then the correlation results were compared in terms of analytical methods and street representation models respectively. In the end, the comparison of results show that (1) natural-street based model is the optimal street model for carrying out space syntax analysis followed by axial lines and axial segments; (2) angular analysis and topological analysis are more advanced than metric analysis; and (3) connectivity, integration and local integration (two-step) are more suitable for predicting human movements in space syntax. Furthermore, it can be hypothesized that topological analysis method with natural-street based model is the best combination for the prediction of human movements in space syntax, for the integration of topological and geometrical thinking.

  • 76.
    Xu, Shulan
    et al.
    Swedish Radiation Protection Authority, Stockholm, Sweden.
    Dverstorp, Björn
    Klos, Ryk
    Wörman, Anders
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Marklund, Lars
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Application of a Regulatory Performance Assessment Approach for Comparison with the Proponent’s Calculations2006Inngår i: Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM, 2006, 980-985 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To be able to carry out review functions regulatory authorities must be able to make critical evaluations of proponents PA cases. In Sweden the Swedish Radiation Protection Authority (SSI) aims to have in place its own suite of performance assessment (PA) tools. These will be used to address the forthcoming PAs submitted by the Swedish Nuclear Waste Management Company (SKB)for an encapsulation plant (2006) and a geological repository for spent fuel (2008). This paper looks at the role and application of the regulator's models to important features of current modelling in SKB's latest PAs. The SSI modelling tools are applied to a mire system in which radionuclides are assumed to be released from a geological repository. Results are presented which illustrate the importance of a deeper understanding of the geosphere-biosphere interface zone than has been the case in assessments to date.

  • 77. Xu, Shulan
    et al.
    Dverstorp, Björn
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Predication of Concentration and Model Validation: Key issues in assessment of long term safety for radioactive waste disposal2008Inngår i: Proceedings of the int. Conference on Radioecology and Environmental Radioactivit / [ed] Per Strand, Justin Brown and Torun Jolle, 2008Konferansepaper (Fagfellevurdert)
  • 78. Xu, Shulan
    et al.
    Dverstorp, Björn
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Prediction of concentration and model validation: Key issues in assessment of long term safety for radioactive waste disposal2008Inngår i: Proceedings of the International Conference on Radioecology and Environmental Radioactivity / [ed] Per Strand, Justin Brown, Torun Jolle, 2008Konferansepaper (Fagfellevurdert)
  • 79. Xu, Shulan
    et al.
    Marklund, Lars
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Wörman, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Vattendragsteknik.
    Dverstorp, Anders
    A regulatory modelling strategy for review of dose calculations2008Inngår i: Proceedings of The 12th International High-Level Radioactive Waste managemenent Conference, American Nuclear Society , 2008, 466-472 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To be able to carry out review functions regulatory authorities must be able to make critical evaluations of proponent's performance assessment (PA) cases. In Sweden the Swedish Radiation Protection Authority (SSI) aims to have in place its own suite of PA tools. These will be used to address the forthcoming PAs submitted by the Swedish Nuclear Waste Management Company (SKB) for a geological repository for spent fuel (2010). This paper looks at the role and application of the regulator's models to important features of current modelling in SKB 's latest PAs. The SSI modelling tools are applied to demonstrate a possible size of the contaminant area due to leakage of radionuclides from a damaged canister. An improved representation of these processes will enhance our understanding of biosphere functions and provide a better basis for evaluating radiological consequences in the safety assessment.

  • 80.
    Zhang, Li
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Ren, Xi
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    A two-factor evaluation of bus delays based on GIS-T database and simulation2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    During the urbanization process, vehicles quantity increase with expansion in population. Under this situation, bus transportation system also suffers from bus delay. Bus delay could be caused by a series of factors, for instance, overload passengers, traffic jam, traffic accident and other unpredictable situations. Therefore, choosing crucial elements to efficiently evaluate bus delay is a complex problem in bus delay researches and operation management. The thesis propose an approach to evaluate and explain bus delay by two elements: traffic congestion and passengers’ waiting time. Those two elements would represent the action of external and internal factors on bus operation. This approach could be adaptive to explain the reasons for bus delays, thus to help the optimization of bus lines and give useful information for decision making of transportation company. To achieve the research aim, a GIS-T database was created by combining the GIS database and TIS database. Spatial data as well as attribute data are combined in the database to represent the crucial information for bus delay. Based on GIS-T the database, the impact of traffic congestion and passengers’ waiting time was calculated using the bus line simulation. By implementing the above steps, the main cause of bus delay was studied. A case study application of this method is narrated; focusing on optimize the bus system of Guiyang city, South China. Different methods are used to find out the problem of system and the reason for delay. Moreover, optimization suggestion is proposed according to result. Compared with other methods, the two-factor method has the advantage of locating the reason of delay for each station. The time performance is not superior to other methods. By comparing the situation of adjacent station, the proportion of traffic congestion and overload passenger in bus delay was determined. The two-factor method is applicable for other transit system in different cities which has similar structure as Guiyang. However, for cities with other structure, a feasibility should be made to select an appropriate model.

  • 81.
    Zhang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transporter och samhällsekonomi, Geodesi.
    Spatial-Temporal Patterns of Urban Growth in Shanghai, China: Monitoring, Analysis, and Simulation2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Supporting huge population, megacities are definitely the hot spots of production, consumption, and waste generation. Without careful investment and planning, megacities will be overwhelmed by burgeoning negative impacts on the environment, natural resources, and human health, as well as a host of social and economic issues. The unprecedented combination of economic and population growth since the Reform and Open Policy has led China into transition from a largely rural society to a predominantly urban one. Chinese cities, without question, have not escaped the danger of the series of problems during the rapid progress of urbanization. Therefore, monitoring the spatial-temporal patterns of urban sprawl and their impact on the environment is of critical importance for urban planning and sustainable development, especially in developing Chinese cities such as Shanghai.

    To date, few studies have focused on the urban trajectories of Shanghai over the past 30 years from a remote sensing perspective. Most of the studies were concentrated on the technical issues of image processing and classification. Moreover, research on spatial metrics has focused on analyzing remote sensing classification results rather than on the use of interpreting, assessing, and verifying urban simulation results. Furthermore, many researches merely focused on baseline projection and very few studies took into consideration urban growth scenarios so far. As yet there have been no reported scenario simulations of future Shanghai growth with several land-use categories within urban areas.

    The overall objective of this research is to investigate the integration of remote sensing, spatial metrics, and spatial-temporal models in the monitoring, analysis, and simulation of urban growth in Shanghai, China. The specific objectives are to: 1). monitor urban dynamics over time with multi-sensor remote sensing images; 2). quantify spatial-temporal properties of urban growth and representing the urban morphological structures by means of spatial metrics; and 3). simulate the geographic extent, patterns, and detailed catalogs of urban growth under different scenarios using Markov-Cellular Automata (Markov-CA) model to support decision making for a more sustainable Shanghai.

    Through this study, the combined approach using remotely sensed data with change detection techniques, spatial metrics, and a scenarios-based simulation model proved to be effective to understand, represent, and predict the spatial-temporal dynamics of urban growth. In detail, the segmented-based hierarchy classification and visual interpretation were effective methods to extract urban and industrial land with high-resolution remotely sensed images. Direct change detection using variables derived from tasseled cap transformation was efficient for monitoring impervious surface sprawl. Spatial metrics is a quick and executable way to assessing the impact of urban sprawl on landscape dynamic. Markov-CA model is a useful tool to simulate the scenarios of future urban developments and therefore provides the policy options for sustainable urban planning.

    The research results of urban trajectories and impervious surface sprawl showed that Shanghai experienced high-speed urban sprawl and the rate of urban expansion, however, was not homogeneous spatially and temporally. The general annual urban expansion speed was 34.8 km2 per year; nevertheless, it reached 80.2 km2 per year recent six years from 2001 to 2007, while it touched the bottom speed around 14.3 km2 per year during 1979-1989. The expanded area in the Puxi region was 5.23 times of its original area while that of Pudong region was 19.94 times of its original area during 1979-2007. The research results of landscape analysis demonstrated that greenbelt becomes fractured while infrastructural and commercial area is more and more aggregated in the central Shanghai area, and satellite images such as SPOT Pan, XS and Landsat TM with 10-30 meter resolution are sufficient for the landscape dynamic research in central Shanghai area. The results of scenarios-based simulation indicated that built-up areas in Shanghai will increase significantly in 2025 and Shanghai will experience less urban sprawl and retain a better environment in 2025 under service-oriented center (SOC) than under baseline (NS) or manufacturing-dominant center (MDC) scenario. If favorable policy for MDC scenario is adopted, however, there will be a lot of manufacturing industries gathering in Shanghai and more agricultural lands will be encroached.

    The present research focused on the analysis of physical and morphological aspects of urban growth. Urban land-use dynamics are, however, intrinsically linked with socio-economic, political, or demographic drivers. Trying to fill in the missing link between traditional urban geography and urban remote sensing & urban simulation and to improve understanding of the interactions between human and natural aspects in the urban socio-ecosystem is the major focus in the next phase of the Ph.D. research.

    Keywords: Urban growth, Spatial-temporal pattern, Remote sensing, Spatial metrics, Scenarios-based simulation, Shanghai

  • 82.
    Zhang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Ban, Yifang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    Liu, Jiyuan
    Institute of Geographic Science and Natural Resources Research, Chinese Academy of Sciences, China.
    Hu, Yunfeng
    Institute of Geographic Science and Natural Resorces Research, Chinese Academy of Sciences, China.
    Simulating urban development scenarios using Markov-Cellular automata: a case study of greater Shanghai area, China2009Inngår i: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this paper is to provide a comparative analysis of urban simulations under different scenarios. The objective of this paper is to provide a comparative analysis of urban simulations under different scenarios. Specifically, this research investigates the Markov-Cellular Automata (Markov-CA) model under different development schemes for simulations of the urban expansion scenarios of Greater Shanghai Area (GSA) in 2015 and 2025 in support of sustainable urban development. In this study, multitemporal land cover dataset, derived from remotely sensed images from 1995, 2000 and 2005 were used for simulation and validation. The scenarios of urban expansion patterns of GSA in 2015 and 2025 under three different schemes, i.e., Non-Scheme (NS), Service Oriented Center scheme (SOC) and Manufacture Dominant Center scheme (MDC), were simulated and comparatively analyzed with the aid of landscape metrics. The results demonstrated that GSA will experience less urban sprawl and retain a better environment in 2025 if the service orientated development policy is given priority. If favorable policy for MDC is adopted, however, there will be a lot of manufacturing industries gathering in GSA and more agricultural lands will be encroached. Through this study, the combined approach using remote sensing data, GIS spatial analysis environment and urban simulation model with landscape metrics and scenario analysis proved to be effective to understand, represent and predict the spatial-temporal dynamics of urban evolution, and Markov-CA model is a useful tool for simulating the scenarios of future urban developments, even though there are some issues that need to be investigated in the future, such as the construction of localized schemes, and the incorporation of political, social, economic and cultural factors. Specifically, this research investigates the Markov-Cellular Automata (Markov-CA) model under different development schemes for simulations of the urban expansion scenarios of Greater Shanghai Area (GSA) in 2015 and 2025 in support of sustainable urban development. In this study, multitemporal land cover dataset, derived from remotely sensed images from 1995, 2000 and 2005 were used for simulation and validation. The scenarios of urban expansion patterns of GSA in 2015 and 2025 under three different schemes, i.e., Non-Scheme (NS), Service Oriented Center scheme (SOC) and Manufacture Dominant Center scheme (MDC), were simulated and comparatively analyzed with the aid of landscape metrics. The results demonstrated that GSA will experience less urban sprawl and retain a better environment in 2025 if the service orientated development policy is given priority. If favorable policy for MDC is adopted, however, there will be a lot of manufacturing industries gathering in GSA and more agricultural lands will be encroached. Through this study, the combined approach using remote sensing data, GIS spatial analysis environment and urban simulation model with landscape metrics and scenario analysis proved to be effective to understand, represent and predict the spatial-temporal dynamics of urban evolution, and Markov-CA model is a useful tool for simulating the scenarios of future urban developments, even though there are some issues that need to be investigated in the future, such as the construction of localized schemes, and the incorporation of political, social, economic and cultural factors.

  • 83.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Neretnieks, Ivars
    Shear effects on solute retardation coefficient in rock fractures: Insights from a particle mechanics modelManuskript (preprint) (Annet vitenskapelig)
  • 84.
    Zou, Liangchao
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Numerical modeling of fluid flow and solute transport in rock fractures2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This study focuses on numerical modeling of fluid flow and solute transport in rough-walled rock fractures and fracture-matrix systems, with the main aim to investigate the impacts of fracture surface roughness on flow and transport processes in rock fractures. Both 2D and 3D fracture models were built from laser-scanned surface tomography of a real granite rock sample, to consider realistic features of surface tomography and potential asperity contacts. The flow was simulated by directly solving the Navier-Stokes equations (NSE) and the transport was modeled by solving the advection-dispersion equation (ADE) in the entire domain of fracture-matrix system, including matrix diffusion process. Such direct simulations provided detailed flow and concentration fields for quantitatively analysis of flow and transport behavior. The detailed analysis of surface roughness decomposition, complex flow patterns (i.e., channeling, transverse and eddy flows), effective advective flow apertures, effective transmissivity, effective dispersivity, residence time, transport resistance and specific surface area demonstrated significant impacts of realistic fracture surface roughness on fluid flow and solute transport processes in rock fractures. The results show that the surface roughness and shear displacement caused asperity contacts significantly enhance nonlinearity and complexity of flow and transport processes in rough-walled fractures and fracture-matrix systems. The surface roughness also causes invasion flows in intersected fractures which enhance solute mixing at fracture intersections. Therefore, the fracture surface roughness is an important source of uncertainty in application of such simplified models like cubic law (CL) for fluid flow and analytical solutions for solute transport in rock fractures. The research conducted advances our understanding of realistic flow and transport processes in natural fractured rocks. The results are useful for model validation/extension, uncertainty analysis/quantification and laboratory experiments design in the context of various applications related to fracture flow and transport.

  • 85.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Modeling of advection-dominated transport in rough-walled rock fractures: a comparison of Reynolds and Navier-Stokes equationsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Statistical analysis of flow-dependent specific surface areas of a 3D rough-walled fracture-matrix system were presented in this paper, based on numerical simulations of fluid flow and advective particle transport. The aim is to investigate the flow-dependent solute transport quantities in natural fracture-matrix systems, and identify the potential uncertainty lie in the common used flow model (i.e., Reynolds equation) by comparing with the more realistic flow model(i.e., Navier-Stokes equations). The rough-walled fracture model was built from laser-scanned surface tomography of a real rock sample, by considering realistic features of surfaces roughness and asperity contacts. Based on the flow fields simulated by solving the Reynolds and Navier-Stokes equations, the advective transport was modeled through Lagrangian particle tracking. The controlling quantities of advective transport in fracture-matrix systems (i.e., residence time, transport resistance and specific surface area) were statistically analyzed and compared. The results generally show that fracture surface roughness and associated spatially variable apertures as well as shear caused asperity contacts significantly increase the heterogeneity of flow field in rough-walled fractures, which consequently affects the flow-dependent transport process. By comparison, the simplified flow model (i.e., Reynolds equation) may cause uncertainty in quantifying of the specific surface area for the realistic rough-walled fracture-matrix systems. To identify such uncertainty, it is important to obtain the more reliable flow fields by solving the NSE. The presented results are helpful in uncertainty quantification and risk assessment of solute transport in natural fractured rocks.

    Fulltekst tilgjengelig fra 2018-10-09 12:47
  • 86.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Effects of multi-level surface roughness on solute transport in single rock fractures2016Inngår i: The proceeding of International Symposium on Reducing Risks in Site Investigation, Modeling and Construction for Rock Engineering, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Natural rock fractures are consisted of complicate rough surfaces with multi-level surface roughness which causes significant uncertainties in fluid flow and solute transport be-haviors through fractured rocks. In this study, for the aim of investigation the effects of multi-level surface roughness on fluid flow and solute transport in rock fractures, a single rough-walled fracture model was built from a scanned granite rock surface, which was then gradually decomposed and characterized by wavelet analysis and statistics. A verified finite volume method (FVM) code was used to simulate fluid flow and solute transport in the rough fracture models by solving the Navier-Stokes equations (NSE) and advection-dispersion equation (ADE). The simulation results of nonlinear flow and solute breakthrough curves (BTCs) showed that the multi-level surface roughness strongly correlated with the Eddy flows and the solute non-Fickian transport behaviors, represented by the changes of effective advective flow apertures and an empirical function of the BTCs. The results would improve our understanding of solute transport in fractured rocks and may help to reduce the uncertainties and risks in related engi-neering practices.

  • 87.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Invasion flow enhanced solute mixing at rough-walled rock fracture intersectionsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The processes of fluid flow and solute transport through rock fractures are of primary importance in environmental engineering and geosciences. This study presented numerical modeling results of fluid flow and solute transport in a 3D rock fracture-matrix system with an orthogonal intersection of two rough-walled rock fractures. The rough-walled fracture geometry models were built from laser-scanned data of a real rock surface, for a realistic representation of natural rock fracture surface roughness. The fluid flow in the two intersected fractures and solute transport in the fracture-matrix system were simulated by solving the Navier-Stokes equations (NSE) and transport equation in the entire system. The dependence of mixing on Péclet number (Pe), flow directionality and interaction with matrix diffusion were analyzed. The results showed important invasion flow patterns that significantly enhanced the solute mixing process, which cannot be described by traditional complete mixing and streamline routing models. It also cannot be simulated by simplified 2D geometry models ignoring the surface roughness as widely used in previous published studies. The finding of invasion flow and associated impacts on mixing in this study is particularly important in prediction of solute transport in natural fractured rocks, especially when discrete fracture network (DFN) approach is applied.

    Fulltekst tilgjengelig fra 2018-10-09 12:20
  • 88.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Modeling of flow and mixing in 3D rough-walled rock fracture intersections2017Inngår i: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 107, 1-9 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The processes of fluid flow and solute transport through rock fractures are of primary importance in environmental engineering and geosciences. This study presented numerical modeling results of fluid flow and solute transport in a 3D rock fracture-matrix system with an orthogonal intersection of two rough-walled rock fractures. The rough-walled fracture geometry models were built from laser-scanned data of a real rock surface, for a realistic representation of natural rock fracture surface roughness. The fluid flow in the two intersected fractures and solute transport in the fracture-matrix system were simulated by solving the Navier–Stokes equations (NSE) and transport equation in the entire system. The dependence of mixing on Péclet number (Pe) and flow directionality features were analyzed. The results directly visualized important channeling flow patterns that significantly enhanced the solute mixing process at the rough-walled fracture intersection. The illustrated channeling flow and associated impacts on mixing are particularly important in the prediction of solute transport in natural fractured rocks, especially when discrete fracture network (DFN) approach is applied.

  • 89.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Modeling of solute transport in a 3D rough-walled fracture-matrix systemManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Fluid flow and solute transport in a 3D rough-walled fracture-matrix system was simulated by directly solving the Navier-Stokes equations for fracture flow and solving the transport equation for the whole domain of fracture and matrix with considering matrix diffusion. The rough-walled fracture-matrix model was built from laser-scanned surface tomography of a real rock sample, by considering realistic features of surfaces roughness and asperity contacts. The numerical modeling results were compared with both analytical solutions based on simplified fracture surface geometry and numerical results by particle tracking based on the Reynolds equation. The aim is to investigate impacts of surface roughness on solute transport in natural fracture-matrix systems, and to quantify the uncertainties in application of simplified models. The results show that fracture surface roughness significantly increases heterogeneity of velocity field in the rough-walled fractures, which consequently cause complex transport behavior, especially the dispersive distributions of solute concentration in the fracture and complex concentration profiles in the matrix. Such complex transport behavior caused by surface roughness are important sources of uncertainty that needs to be considered for modeling of solute transport processes in fractured rocks. The presented direct numerical simulations of fluid flow and solute transport serve as efficient numerical experiments that provide reliable results for the analysis of effective transmissivity as well as effective dispersion coefficient in rough-walled fracture-matrix systems. Such analyses are helpful in model verifications, uncertainty quantifications and design of laboratorial experiments.

    Fulltekst tilgjengelig fra 2018-10-09 12:17
  • 90.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. KTH.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Shear enhanced nonlinear flow in rough-walled rock fracturesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Nonlinear flow in 3D rough-walled rock fracture models are simulated by solving the Navier-Stokes equations in this paper. The emphasis is on the impacts of shear caused aperture changes (variable apertures and asperity contacts) and flow conditions (inertial term) upon nonlinear flow behaviors in 3D rough-walled rock fractures. In order to compare shear effects, two 3D fracture models, with and without shear process, were established with the identical initial rough-walled surfaces tomography of a realistic rock sample. Five groups of simulations with different inflow boundary conditions of flowrates/Reynolds numbers (Re) were conducted to demonstrate shear enhanced nonlinearity of flow fields and limitations of local cubic law (LCL) approach. The flow results clearly show channeling flow along the preferential fluid paths, transverse flow around the contact spots and eddy flows behind contact spots with increasing Re numbers, which cannot be observed in 2D models. The effective transmissivity of the 3D fracture model was calculated from the modeling results of velocity and pressure fields. The results showed that the effective transmissivity is a function of local apertures with important uncertainties even when Re is small (i.e. Re = 0.4 in this study), thus the validity of the transmissivity evaluation using LCL approach for nonlinear flow in 3D rough-walled rock fractures is questionable. The mechanical effects, i.e. stress and shear caused aperture space changes and asperity contacts should be considered for modeling flow and mass/energy transport processes in rough-walled fractures in 3D.

    Fulltekst tilgjengelig fra 2018-10-09 12:00
  • 91.
    Zou, Liangchao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Resurser, energi och infrastruktur.
    Shear-enhanced nonlinear flow in rough-walled rock fractures2017Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 97, 33-45 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonlinear flow in 3D rough-walled rock fractures is simulated by solving the Navier-Stokes equations. The emphasis is on the impact of shear-caused aperture changes (variable apertures and asperity contacts) and flow conditions (inertial term) upon nonlinear flow behavior. In order to compare shear effects, two 3D fracture models, with and without shear, were established with identical initial rough-walled surfaces topographies of a realistic rock sample. Five groups of simulations with different inflow boundary conditions of flowrates/Reynolds numbers (Re) were conducted to demonstrate shear-enhanced nonlinearity of flow fields and limitations of local cubic law (LCL) approach. The flow results clearly show channeling flow along the preferential paths, transverse flow around the contact spots, and eddy flows behind contact spots with increasing Re, which cannot be observed in 2D models. The effective transmissivity of the 3D fracture model was calculated from the modeling results of velocity and pressure fields. The results showed that the effective transmissivity is a function of local apertures with important uncertainties even when Re is small (i.e. Re = 0.4 in this study), thus the validity of the transmissivity evaluation using LCL approach for nonlinear flow in 3D rough-walled rock fractures is questionable.

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