| 1. |
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INNOTRACK: Concluding technical report
- 2010
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Editorial collection (peer-reviewed)abstract
- The track structure, rails, switches and crossings account for more than 50% of maintenance and renewal costs for the rail industry. To improve the competitiveness of rail transportation, the cost-efficiency of these areas needs to be addressed.This the background to INNOTRACK, an integrated research project funded by the European Commission’s 6th research framework pro- gramme. Running from September 2006 to December 2009, INN- OTRACK has developed a multitude of innovative solutions in the areas of track substructure, rails & welds, and switches & crossings. The solutions have been assessed from technical, logistics and life cycle cost point of views.This Concluding Technical Report of INNOTRACK includes an overview of the project. It further details implementable results, and clusters them into ”highlight” areas. In addition, the book acts as a ”key” to the vast amount of information from INNOTRACK: All sections refer to project reports where more information can be found.
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| 2. |
- Acuña, José, 1982-
(author)
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Distributed thermal response tests : New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes
- 2013
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Artistic work (other academic/artistic)abstract
- U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.
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| 3. |
- Mathern, Alexandre, 1986, et al.
(author)
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Experimental study of time-dependent properties of a low-pH concrete for deposition tunnels
- 2018
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In: fib Symposium. - 2617-4820. ; , s. 1726-1735
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Conference paper (peer-reviewed)abstract
- The Swedish Nuclear Fuel and Waste Management Company developed a method for the final disposal of canisters for spent nuclear fuel in tunnels at depths of about 500 meters. The concept for closure of the deposition tunnels is based on a bentonite seal supported by a spherical concrete dome structure. In order to fulfil the requirements specific to the repository concept, a special mix of low-pH self-compacting concrete was developed. A series of large-scale castings and laboratory tests were conducted to gain experience on this low-pH concrete mix, in conjunction with the full-scale demonstration test of an unreinforced concrete dome plug in the underground hard rock laboratory in Äspö, Sweden. The laboratory tests aimed at studying the creep properties under high sustained compressive stresses of the low-pH concrete mix, its shrinkage properties and the properties of the rock-concrete interface. This paper provides an overview of these tests and analyses the latest results of the recently completed creep tests, which include 6 years of measurements. These results allow to improve understanding of the structural behaviour of the concrete plug and to assess the effects of the very high pressure acting on the plug on its deformations, cracking and water tightness.
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| 4. |
- Nickman, Alireza
(author)
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Road disasters? Modeling and assessment of Swedish roads within crucial climate conditions
- 2016
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Doctoral thesis (other academic/artistic)abstract
- 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.
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| 5. |
- Mutafela, Richard Nasilele, et al.
(author)
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Geophysical investigation of glass 'hotspots' in glass dumps as potential secondary raw material sources
- 2020
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In: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 106, s. 213-225
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Journal article (peer-reviewed)abstract
- This study investigates the potential for Electrical Resistivity Tomography (ERT) to detect buried glass ‘hotspots’ in a glass waste dump based on results from an open glass dump investigated initially. This detection potential is vital for excavation and later use of buried materials as secondary resources. After ERT, test pits (TPs) were excavated around suspected glass hotspots and physico-chemical characterisation of the materials was done. Hotspots were successfully identified as regions of high resistivity (>8000 Ωm) and were thus confirmed by TPs which indicated mean glass composition of 87.2% among samples (up to 99% in some). However, high discrepancies in material resistivities increased the risk for introduction of artefacts, thus increasing the degree of uncertainty with depth, whereas similarities in resistivity between granite bedrock and crystal glass presented data misinterpretation risks. Nevertheless, suitable survey design, careful field procedures and caution exercised by basing data interpretations primarily on TP excavation observations generated good results particularly for near-surface materials, which is useful since glass waste dumps are inherently shallow. Thus, ERT could be a useful technique for obtaining more homogeneous excavated glass and other materials for use as secondary resources in metal extraction and other waste recycling techniques while eliminating complicated and often costly waste sorting needs.
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| 6. |
- Paul, Seema
(author)
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Lake Hydrodynamics and Pollution Transport under Climate Change : The Case of Lake Victoria
- 2023
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Doctoral thesis (other academic/artistic)abstract
- A very small part of the total earth’s water is freshwater (only 2.5 %). Unfortunately, due to climate change and pervasive manmade activities, surface freshwater quality in many places of the world has become degraded. This is manifested in the Rift Valley lakes, a series of lakes in Eastern Africa that runs from Ethiopia in the north to Malawi in the south. Water quality degradation in the Rift Valley lakes is driven by various factors, including water quantity and scarcity, pollution and contamination, nutrients loading, and general water use by industry and society. In particular, Lake Victoria, the world’s second-largest freshwater body and the largest tropical lake, has seriously polluted near lakeshore areas, which is a great regional development problem causing misfortune for millions of people.This dissertation contributes new insights into lake hydrodynamic processes and pollution transport in shallow lakes through developing more accurate models to understand the complex processes of water quality degradation. Based on empirical data this thesis developed systematic methods to consider lake bathymetry, lake flow, water level verification, water balance, hydro-climatological processes, transport and dispersion of pollutants and nutrient particles. The data-driven hydrological model of Lake Victoria that is developed in the thesis considers hydro-meteorological and climatological data, river discharges and outflow, wind speed and direction, atmospheric deposition, nutrient loading, concentration of pollutants and nutrients, and remote sensing satellite data. The thesis illustrates the power of numerical and hydrodynamic methods that uses one- and two-dimensional mathematical equations (1D and 2D) to model the three-dimensional (3D) behaviour of shallow lakes over time. The results indicate that the lake hydrodynamics of Lake Victoria are heavily influenced by lake bathymetry and regional weather patterns and are thus connected to increasing climate variation. The hydro-meteorological processes, verified by empirical data on precipitation, lake flow and lake water levels, show that extreme weather events are responsible for changing the characteristics of lake water balance, changing seasonal variations, and exhibiting strong correlations among water level and hydro-meteorological data. The model of the movement of pollutants and nutrient particles shows how pollutants and nutrients travel within Lake Victoria and where they concentrate in the lake and its sediments. The wind hydrodynamic modelling shows that the wind, along with hydrodynamic stability, plays an important role in pollution flow patterns and that pollutants can be transported from shallow parts, when they leave rivers and shorelines, to deeper lake areas. The hydro-climatological model demonstrates the crucial interdependence between hydrodynamic processes and climatological factors at the catchment scale of Lake Victoria. The numerical models and calculation methods that have been developed in this dissertation represent additional contributions to hydrodynamic research and can be used to investigate hydrodynamic processes in other lakes. The thesis contributes to UN Sustainable Development Goals related to water security, drinking water, food, and health. A potential area of application lies in supporting analysis and mitigation of pollution and climate change effects and more generally aid in the natural resource governance of this vital African lake.
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| 7. |
- Löfgren, Johan, 1983, et al.
(author)
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Sea level time series and ocean tide analysis from multipath signals at five GPS sites in different parts of the world
- 2014
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In: Journal of Geodynamics. - : Elsevier BV. - 0264-3707. ; 80, s. 66-80
-
Journal article (peer-reviewed)abstract
- We present sea level observations derived from the analysis of signal-to-noise ratio (SNR) data recorded by five coastal GPS stations. These stations are located in different regions around the world, both in the northern and in the southern hemisphere, in different multipath environments, from rural coastal areas to busy harbors, and experience different tidal ranges.The recorded SNR data show periodic variations that originate from multipath, i.e. the interference of direct and reflected signals. The general assumption is that for satellite arcs facing the open sea, the rapid SNR variations are due to reflections off the sea surface. The SNR data recorded from these azimuth intervals were analyzed by spectral analysis with two methods: a standard analysis method assuming a static sea level during a satellite arc and an extended analysis method assuming a time dependent sea level during a satellite arc.The GPS-derived sea level results are compared to sea level records from co-located traditional tide gauges, both in the time and in the frequency domain. The sea level time series are highly correlated with correlation coefficients to the order of 0.89–0.99. The root-mean-square (RMS) difference is 6.2 cm for the station with the lowest tidal range of 165 cm and 43 cm for the station with the highest tidal range of 772 cm. The relative accuracy, defined as the ratio of RMS and tidal range, is between 2.4% and 10.0% for all stations.Comparing the standard analysis method and the extended analysis method, the results based on theextended analysis method agree better with the independent tide gauge records for the stations with a high tidal range. For the station with the highest tidal range (772 cm), the RMS is reduced by 47% when using the extended analysis method. Furthermore, the results also indicate that the standard analysis method, assuming a static sea level, can be used for stations with a tidal range of up to about 270 cm, without performing significantly worse than the extended analysis method.Tidal amplitudes and phases are derived by harmonic analysis of the sea level records. Again, a high level of agreement is observed between the tide gauge and the GPS-derived results. Comparing the GPS-derived results, the results based on the extended analysis method show a higher degree of agreement with the traditional tide gauge results for stations with larger tidal ranges. Spectral analysis of the residuals after the harmonic analysis reveals remaining signal power at multiples of the draconitic day. This indicates that the observed SNR data are to some level disturbed by additional multipath signals, in particular for GPS stations that are located in harbors.
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| 8. |
- Murekatete, Rachel Mundeli, 1981-
(author)
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Sensitivity, Variation, and Application of Least-Cost Path Models in Landscape Connectivity Analysis and Corridor Planning
- 2022
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Doctoral thesis (other academic/artistic)abstract
- In recent decades, Rwanda has been affected by the loss and fragmentation of natural habitats for native species of animals and plants. As a consequence, landscape connectivity—i.e., the degree to which a landscape facilitates or impedes the movement of organisms between resource patches—has considerably weakened or is even completely lost, causing detrimental effects on biodiversity, notably the reduction of populations of key native species. In order to counter this problem, one potential solution currently being explored by local planners in Rwanda consists of establishing conservation corridors for organisms to move safely between their habitat remnants. Specifically, this thesis was inspired by a project initiated by the Dian Fossey Gorilla Fund International, a conservation non-governmental organization (NGO) based in Rwanda, which consists of establishing a conservation corridor for pollinators.For their capabilities of storing, processing, and visualizing landscape data, geographic information systems (GIS) have been increasingly popular among conservation biologists and practitioners. Of particular relevance to connectivity analysis and corridor planning is the least-cost path model. A typical use of this model is such that one first estimates the cost for a certain action (e.g., movement by an organism or acquisition by a government) at each location of a given landscape and represents the results in the form of a raster surface, and then measures the degrees of connectivity between patches of interest in terms of effective distances, which are equated with least-cost path distances over the raster cost surface. While the least-cost path model is easy to use and available in virtually any commercial raster-based GIS, we observe that users of it often overlook some important assumptions, the violation of which might greatly affect the validity of the model’s outcome.The goal of this thesis is to provide a scientific contribution to landscape connectivity analysis and conservation corridor planning by 1) investigating the potential misuse or abuse of the conventional least-cost path model when sufficient information is not available on the underlying cost surface, 2) proposing an alternative model under such a circumstance and 3) demonstrating its relevance to conservation practice. More specifically, for the model to work, it is explicitly or implicitly assumed that, the optimality of a path is evaluated as the sum of the cost-weighted lengths of all its segments—cost-weighted, i.e., multiplied by their underlying cost values. The validity of this assumption must be questioned, however, if cost values are measured on a scale—e.g., an ordinal scale of measurement in Stevens’s typology—that does not permit arithmetic operations. In a typical practice of landscape connectivity analysis and corridor planning, the raster cost surface is created by transforming one or more sets of values (e.g., land cover type, land ownership, and elevation) attributed to cells into another set of such values (representing cost) through a function reflecting one or more criteria. A question arises: how certain can one be about the correctness of such a cost estimation function?There are at least four issues in the application of the least-cost path model to landscape connectivity analysis and corridor planning under uncertainty. First, while it is generally anticipated that different cost estimation functions lead to different least-cost paths (hence to different effective distances or different corridor locations), little is known on how such differences arise (or do not arise). Second, while it is generally recognized that the location and length of a least-cost path are both sensitive to the spatial resolution of the raster cost surface, little is known if they are always sensitive in the same way and to the same degree and if not, what makes them more (or less) sensitive. Third, when it is difficult to establish a fully connected corridor between target habitat areas (e.g., because of surrounding anthropogenic activities), the least-cost path (which is by definition fully connected) may not be useful at least in its original form. Lastly, even if the conventional least-cost path model may have inconsistent results in theory, it may well be continued to be used in practice, unless there is a sound alternative to it.The issues raised above are addressed through four studies corresponding to four respective papers which are appended to this thesis. While the first three studies use artificial landscape data generated by computers with varying spatial and non-spatial characteristics, the fourth study uses data on a real landscape. The first study (Paper 1) evaluates how the locations and lengths of least-cost paths (the latter of which are referred to as least-cost distances) vary with change in cost estimation parameters. This is done through a series of computational experiments, in which each of the artificial landscapes is converted into different cost surfaces by systematically varying parameters of a cost-estimation function, on which least-cost paths are generated. The locations and lengths of those paths are statistically analyzed to find sources of their variation. The second study (Paper 2) investigates how the least-cost distance is affected by the spatial resolution of the corresponding cost surface. This is also done through a series of computational experiments, in which each of the artificial landscapes is converted into a cost surface, which is, in turn, converted into different cost surfaces (different, i.e., only in their spatial resolutions) by systematically aggregating grid cells. Then, the statistical behavior of the ratio of the least-cost distance measured on a lower-resolution cost surface to that measured on a higher-resolution cost surface is analyzed. The third study (Paper 3) proposes the mini-max path model as an alternative to the least-cost path model. Unlike the conventional model (in which the optimality of a path is based on the sum of its length multiplied by the underlying cost values), the alternative model determines the optimality of a path using the length of a segment(s) of the path that intersects the cells having the maximum cost value (with a special tie-breaking rule). The performances of the two models are tested in one of the following two assumptions at a time: the cost values are measured on an ordinal scale or on a ratio scale. The fourth study (Paper 4) applies the model proposed in the third study to an ongoing conservation project of the Dian Fossey Gorilla Fund International that plans to design a ‘stepping-stone’ corridor—which is not fully connected but takes the form of a sequence of fragmented forest patches—between two core habitat areas of pollinator birds between two protected areas in Rwanda. The project does not have complete information on the study area and the target species and thus the project staff can only rank land cover types in terms of their suitability/cost for being part of the corridor. The utility of the model is tested with different assumptions on the behavior of the birds (e.g., minimum stepping stone size) as well as on the cost associated with the implementation of the corridor (e.g., cost for planting shrubs along the corridor to encourage the birds to use it).The first study finds that the same pair of terminal cells may well be connected by different least-cost paths on different cost surfaces though derived from the same landscape data. The variation among those paths is highly sensitive to the forms of spatial and non-spatial distributions of landscape elements (which cannot be controlled by users of the least-cost path model) as well as by those of cost values derived from them (which may be, at least indirectly, controlled by users of the model). The second study finds that least-cost distances measured on lower-resolution cost surfaces are generally highly correlated with—and useful predictors of—effective distances measured on higher-resolution cost surfaces. This relationship tends to be weakened when linear barriers to connectivity (e.g., roads and rivers) exist, but strengthened as distances increase and/or when linear barriers (if any) are detected by other presumably more accessible and affordable sources such as vector line data. The third study confirms the effectiveness of the conventional least-cost path model on ratio-scaled cost surfaces but finds that the alternative mini-max path model is mathematically sounder if the cost values are measured on an ordinal scale and practically useful if the problem is concerned not with the minimization of cost but with the maximization of some desirable condition such as suitability. The fourth study demonstrates the utility of the mini-max path model by effectively casting the stepping stone corridor problem as a special case of it. The model allows for a rapid first delineation of candidate routes for stepping stone corridors and facilitates the early exploratory stages of conservation projects.Major implications of this thesis to the research and practice in landscape connectivity analysis and conservation corridor planning with raster-based GIS are summarized as follows.When sufficient information is available for quantification of cost values, the conventional least-cost path model is a reasonable approach to use.However, it is worth trying or at least acknowledging alternatives that do not rely on the quantitative-cost assumption if the value of each cell only indicates the ordinal category of cost of intersecting that cell. Note in particular that information used for cost estimation in practice (e.g., expert opinions or public surveys) are often of subjective and qualitative nature.The highest-resolution data may not always be most effective—much less, most cost-effective—for the task being undertaken. The choice of spatial resolution of th
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| 9. |
- Routh, Joyanto, 1968-
(author)
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Metamorphism and Structural Interpretation of the Zanskar Shear Zone, PJW Himalaya, India
- 1993
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In: Journal of the Geological Society of India. - : Geological society of India. - 0016-7622 .- 0974-6889. ; 41:3, s. 187-198
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Journal article (peer-reviewed)abstract
- Herren in 1987, reported normal faults resulted in the telescoping of metamorphic isograds within a 200 meter zone between Sumche Topko to Mulung Topko in the Zanskar Shear Zone NW Himalaya. However petrographic study-of sections obtained from Mulung Topko and surrounding areas (pensila-padarn section) indicate that the rocks belong to the kyanite-sillimanite-starurolite grade only. Extension crenulation cleavage and other shear criteria show an initial NESW movement after which a layer parallel extension occurred and the shear zone developed. Minieralogical assemblage and mapping indicate that the isograds run paralleI to each other before they possibly truncate against the shear zone along the Pensila-Padam section. A probable model has been proposed to explain the features
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| 10. |
- Zou, Liangchao, 1987-, et al.
(author)
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Impact of Normal Stress Caused Closure on Fluid Flow and Solute Retention in Rock Fractures
- 2018
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Conference paper (peer-reviewed)abstract
- Modeling of coupled hydro-mechanical and chemical (HMC) processes in fractured rocks is an important topic for many geoengineering projects. Over the past decades, many efforts have been devoted to study the flow and transport in single fractures with consideration of mechanical effects. It is generally known that the mechanical effects, i.e. normal and shear deformation, significantly affect fluid flow and solute transport processes in rough-walled rock fractures since the deformation may largely alter the structure of fracture apertures that directly controls transmissivity. Due to complicated physical processes combined with complexity of geometry structures, many issues remain open questions, such as fracture surface roughness characterization, deformation dependence of transmissivity and advective transport in natural rock fractures. In this work, we attempt to investigate the impact of stress caused closure on fluid flow and solute advective transport in a rough-walled fracture through numerical modeling. A rough-walled fracture model is created based on a laser-scanned rock surface. The Bandis’s model is used to describe the fracture closure subject to normal stress. The flow is modeled by solving Reynolds equation and the advective transport is simulated through Lagrangian particle tracking. The results show that the normal stress caused fracture closure creates asperity contacts and reduces the mean aperture, which significantly reduces transmissivity, and affects the travel time and transport resistance. With increases of normal stress, the specific surface area reduces nonlinearly due to the nonlinear closure. In practice, especially for important hydrogeological projects, e.g. nuclear waste disposal, it is important to consider the coupled HMC processes in design and risk assessment.
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