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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Grouting Design Considering Different Geological Conditions : Grout evaluation for the extension of the Blue Metro Line

Al Omari, Roaa, Alali, Yasmeen January 2021 (has links)
This thesis forms the basis for a new documented experience of grouting design and work in the extension of the blue metro line in Stockholm. It includes documentation of the grouting design based on theoretical basis, stop criteria and fan geometries for favorable and unfavorable geological conditions. The work is concerned in evaluating the design stop criteria in different geological conditions to assess the efficiency of grouting process, and its compatibility to the maximum permissible leakage according to applications submitted to the land and environmental court in Stockholm. The work was conducted in cooperation with TYPSA AB and SWECO; the joint venture who designed the grouting work. This work was initiated by studying the design documents and reports, requirements, geological and hydrogeological prognosis documents. Six access tunnels were analyzed, with different work percentage based on the actual work achieved at the site at the time of conducting the study. Each access tunnel stretch was determined in terms of geological condition (rock quality), hydrogeological domain, and grouting class (IK1, IK2 or IK3). Evaluations and assessments were done for different aspects including evaluating the grout volume uptake per each grouting class, calculating the percentage of boreholes that stopped by time, volume or zero flow per grouting class, and comparing the measured leakage with prognosed leakage to check the efficiency of the design and implementation phases. RTGC (Real Time Grouting Control) method was also applied on some fans to check its validity in grout optimization, knowing that it is a relatively new method and not yet fully validated. The results showed that geological mappings during the implementation phase were slightly different from the mappings done during the design phase, which is expected due to the high uncertainties in rock mass science. It was also shown that the design stop criteria in this project were promising, through which they have satisfied the requirements according to the application to the land and environmental court. Average grout uptake in typical injection classes were compatible with the results in City Line projects, where the average grout uptake in 2 L/m. However, results also showed that in weakness zones, the average grout uptake was different with high standard deviations. Knowing the fact that unfavorable geological conditions were classified based on different parameters, it is not possible to find one reference value for the grout uptake, but instead results can be used as references in similar geological conditions in main tunnels work and future projects. Some recommendations are made in this thesis on the design stop criteria in weakness zones, surface rock domains, and at fans injected at large water depth. These zones always form the basis for controversial discussions and thus, if documentation of grouting work is carried out and continued in this project, then more knowledge can be gained and transferred to other projects. As part of this thesis, RTGC was applied in favorable conditions where it showed very promising results, the matter that makes it possible to optimize the stop criteria and actual work by conducting trial grouting. However, in unfavorable geological conditions, the RTGC could not be applied because the dimensionality of the flow is 3D, while RTGC was developed for 1D and 1D flow. Therefore, and since it was proven to be as a promising tool, further studies are recommended to develop the method for 3D flow. / Denna avhandling utgör grunden för en ny dokumenterad upplevelse av injekteringsdesign och arbete i förlängningen av den blå tunnelbanelinjen i Stockholm. Den innehåller dokumentation av injekteringsdesignen baserad på teoretisk grund, stoppkriterier och fläktgeometrier för gynnsamma och ogynnsamma geologiska förhållanden. Arbetet handlar om att utvärdera designstoppskriterierna under olika geologiska förhållanden för att bedöma injekteringsprocessens effektivitet och dess kompatibilitet med maximalt tillåtna läckage enligt ansökningar som lämnats in till Mark- och miljödomstolen i Stockholm. Arbetet genomfördes i samarbete med TYPSA AB och SWECO; det gemensamma företaget som designade injekteringsarbetet. Detta arbete inleddes genom att studera designdokument och rapporter, krav, geologiska och hydrogeologiska prognosdokument. Sex arbetstunnlar analyserades, med olika arbetsprocent baserat på det faktiska arbete som uppnåddes på platsen när studien genomfördes. Varje arbetstunnelsträcka bestämdes i termer av geologiskt tillstånd (bergkvalitet), hydrogeologisk domän och injekteringsklass (IK1, IK2 eller IK3). Utvärderingar och bedömningar gjordes för olika aspekter inklusive utvärdering av injektionsmassans upptag per injekteringsklass, beräkning av andelen borrhål som stoppades av tid, volym eller nollflöde per injekteringsklass och jämförelse av det uppmätta läckaget med prognostiserat läckage för att kontrollera effektiviteten av design- och implementeringsfaserna. RTGC-metoden (Real Time Grouting Control) tillämpades också på vissa fans för att kontrollera dess giltighet vid injekteringsoptimering, med vetskap om att det är en relativt ny metod och ännu inte helt validerad. Resultaten visade att geologiska kartläggningar under implementeringsfasen skilde sig något från kartläggningarna som gjordes under designfasen, vilket förväntas på grund av den höga osäkerheten inom bergmassevetenskap. Det visades också att designstoppskriterierna i detta projekt var lovande, genom vilka de har uppfyllt kraven enligt ansökan till mark- och miljödomstolen. Genomsnittligt injektering av injekteringsbruk i typiska injektionsklasser var förenligt med resultaten i City Line-projekt, där det genomsnittliga injekteringen av injekteringsbruk i 2 liter / m. Resultaten visade emellertid också att i svaghetszoner var det genomsnittliga injekteringen av injekteringsbruk annorlunda med höga standardavvikelser. Att veta det faktum att ogynnsamma geologiska förhållanden klassificerades baserat på olika parametrar är det inte möjligt att hitta ett referensvärde för injekteringen av injekteringsbruk, utan resultaten kan användas som referenser i liknande geologiska förhållanden i huvudtunnelarbeten och framtida projekt. Några rekommendationer görs i denna avhandling om designstoppskriterier i svaghetszoner, ytbergsdomäner och vid fläktar injicerade på stort vattendjup. Dessa zoner utgör alltid grunden för kontroversiella diskussioner, och om dokumentation av injekteringsarbete utförs och fortsätter i detta projekt, kan mer kunskap fås och överföras till andra projekt. Som en del av denna avhandling tillämpades RTGC under gynnsamma förhållanden där det visade mycket lovande resultat, det som gör det möjligt att optimera stoppkriterierna och det faktiska arbetet genom att utföra försöksfogning. Men under ogynnsamma geologiska förhållanden kunde RTGC inte tillämpas eftersom flödets dimension är 3D, medan RTGC utvecklades för 1D- och 1D-flöde. Därför, och eftersom det visade sig vara ett lovande verktyg, rekommenderas ytterligare studier för attutveckla metoden för 3D-flöde.
102

Deformation of Granular Materials under Multi-Directional Loading

Li, Xing January 2018 (has links)
The deformation and failure properties of granular soils largely affect the stability of upper structures built on or in such soils. Owing to its discrete nature as well as the randomness of particle shape and inter-particle connectivity, the internal structure of a granular material usually exhibits a certain level of anisotropy. In addition, the microstructure of a granular material evolves following certain patterns, which are influenced by the initial fabric, void ratio, stress level, as well as the stress or deformation history. It has been a major challenge to properly describe the deformation of anisotropic granular materials in constitutive models especially when the materials are subjected to cyclic loading. The existing constitutive models usually have limited capabilities in describing the behaviour of granular materials subjected to repeated loading with principal stress rotation. How to quantify the microstructure change and how to consider the changing microstructure in constitutive models have been two missing links for building a comprehensive model framework. This research aimed at developing a constitutive model that can properly describe the deformation of granular soils under repeated multi-directional loading. To achieve this goal, a systematic study was performed, including a comprehensive experimental study and a theoretical development of a stress-strain model with proper consideration of the influence of fabric. The developed model was verified with experimental results and then implemented into a finite element code to solve boundary-valued problems. In the first part of this study, a comprehensive experimental study was carried out to investigate the behaviours of granular materials under both monotonic and cyclic loading to investigate the influence of the intermediate principal stress and the major principal stress direction on soil responses. The results of monotonic loading tests showed that both the strength and dilatancy of sand decreased notably with an increase of either the intermediate principal stress or the inclination angle of the major principal stress direction relative to the major principal fabric direction. The stress states at failure from the tests suggested that the benchmarked Matsuoka-Nakai and Lade-Duncan failure criteria are only valid under certain conditions. From the cyclic loading tests, it was observed that, in addition to the increased intermediate principal stress, varied cyclic loading direction caused a significant increase in accumulative volumetric compaction. To consider the microstructural dependencies of granular materials, a more general mathematical formulation of stress-dilatancy was developed based on the assumption of the existence of a critical state fabric surface that is expressed as a function of the invariants of the fabric tensor. This assumption was also used to establish the fabric evolution law. The implementation of the resulting stress-dilatancy formulation and the fabric evolution law in elasto-plasticity theory produced interesting modelling results consistent with experimental observations with respect to the microstructural aspects of granular materials. The developed constitutive model was further extended to cyclic loading within the framework of hypo-plasticity with kinematic hardening. The model was capable of describing the behaviour of sand subjected cyclic loading under various conditions including the variation of loading directions. Finally, the constitutive model was implemented into a commercial software package ABAQUS via the subroutine UMAT. The capacity of the proposed stress-strain model in solving boundary value problems was examined. Six series of elements tests were designed to examine the proposed model under different initial void ratios, degrees of anisotropy, loading directions, and stress paths. Furthermore, a series of simulations were performed for the settlement of footing on sands with different bedding plane orientations. Results from the simulations were found to be consistent with experimental observations. / Thesis / Doctor of Philosophy (PhD)
103

Soil Nailing: a Monte Carlo Simulation of Soil Parameters

Taule, Christoffer January 2019 (has links)
No description available.
104

Utvärdering av produktionsflöde vid insamling av djupdata från en Autonomous Surface Vehicle (ASV) : Analys av noggrannhet vid användning av ASV för djupdata insamling / Evaluation of the Production Workflow for Depth Data Collection Using an Autonomous Surface Vehicle (ASV)

Almarashli, Mohammad January 2024 (has links)
Sjöfartsverket som förvaltar sjömätning i Sverige använder flera specialiserade fartyg och utrustningar för att samla in djupdata, och har nyligen börjat undersöka möjligheten att använda en autonom farkost (ASV) för insamling av djupdata i grunda vatten. Syftet med detta arbete är att utvärdera hela processen för datainsamling för ASV-mätningar enligt FSIS-44 noggrannhetskrav och Category of Zones of Confidence (CATZOC).Skräddaren är en ASV utrustad med fyra enkelstråleekolod (SBES) och en sidescansonar (SSS). Studien innefattar utvärdering av äldre tester och mätuppdrag utförda med skräddaren som visade att det fanns en gemensam brist för utförda mätuppdrag där glipor uppkom mellan planerade mätkurser som gjorde att FSIS-44 noggrannhetskrav kunde ej uppfyllas. Beräkningar av ekolodets sidolob detektionsnivå utfördes för att påpeka på möjligheten att identifiera objekt med sidolober även vid uppkommande av glipor. Resultat visade att sidolob har en detektionsintervall mellan 1–2 m om ekolodet på motsvarande bottentyp kan detektera djup mellan 20–40 m.Fotavtryck storlek, samt analyser av uppkommande av glipor och överlappningar mellan skräddarens respektive SBES beräknades vid olika djupnivåer. Utöver det skapades en automatiserad tabell i Excel för att hitta de lämpliga kursavstånd som kan användas vid olika djupnivåer för att uppfylla FSIS-44 Special Order krav för fullbottensökning.Avslutningsvis, visade arbetet att insamlade djupdata med skräddaren kan teoretisk uppfylla FSIS-44 Special Order krav om lämpliga kursavstånd används i relation till djupet. Insamlade djupdata med skräddaren kan även klassas som CATZOC A1 om positionsnoggrannheten är inom tillåtna ram. Övriga CATZOC A1-krav, såsom fullbottensökning och djupnoggrannhet kan skräddaren uppfylla.
105

Centrifuge and finite element modelling of buried flexible culverts

Mokrani, A. January 1988 (has links)
No description available.
106

The simulation of sampling disturbance and its effects on the deformation behaviour of clays

Hajj, Ahmed Ramez January 1991 (has links)
The importance of studying the behaviour of soil at small strain levels (« 0.1 %) has been increasingly recognised in recent years. In the laboratory, tests are usually conducted on tube samples retrieved from the ground, which inevitably suffer from disturbance. This thesis describes an investigation of the effects of sampling disturbance on the small strain behaviour of one-dimensionally consolidated kaolin. Following the suggestion of Baligh (1985), tube sampling disturbance was simulated by applying a strain cycle in the triaxial cell. Comparative tests on 'disturbed' and 'undisturbed' specimens were conducted in a specially designed 100 mm hydraulic triaxial apparatus. Tests were also carried out in a 38 mm triaxial cell to study the effects of loading rate and overconsolidation ratio on the small strain deformation behaviour of isotropically consolidated kaolin. In the 100 mm cell the local axial and radial strains were measured using proximity transducers mounted on adjustable fittings, enabling small strains to be measured accurately at any stage of a test. The axial strain was also measured between the end caps and externally. Comparisons of these three axial strain measurements showed that, under favourable conditions when bedding errors arc negligible, end cap or external strains may be considered satisfactory. Bedding errors are reduced by consolidating the specimen to a high stress level and providing a rigid connection to the top cap. External strains must be corrected for equipment compliance. Tests for the effects of sampling disturbance indicated that reconsolidating disturbed specimens to their initial stress conditions results in an adequate recovery of the small strain stiffness, but yields a higher stiffness at larger strains. The recovery of the small strain stiffness was better in compression tests than in extension tests and further work is required to understand this finding. Specimens were observed to approach failure during the simulation of sampling disturbance. For isotropically consolidated specimens, the relationships between normalised small strain stiffness at a given strain level and both overconsolidation ratio and rate of shearing were linear on a semi-logarithmic scale. This is in agreement with expectation on the basis of most previous research, but the effect of over consolidation ratio requires further study using one-dimensionally consolidated specimens. The experimental results were compared with the predictions from theoretical models based on critical state soil mechanics. These comparisons showed that the behaviour of kaolin under monotonic loading can be adequately predicted, even at small strains. Encouraging predictions were also made for behaviour during the loading cycle, as sampling disturbance was simulated. However, further theoretical developments are needed to take into account the rate of shearing. The critical state parameters derived from the present tests and used in the model predictions showed close agreement with those obtained by other researchers.
107

Multiscale thermo-hydro-mechanical-chemical coupling effects for fluid-infiltrating crystalline solids and geomaterials: theory, implementation, and validation

Na, SeonHong January 2018 (has links)
Extreme climate change and demanding energy resources have led to new geotechnical engineering challenges critical for sustainable development and resilient infrastructure of our society. Applications such as geological disposal of nuclear waste and carbon dioxide, artificial ground freezing, and hydraulic fractures all require an in-depth understanding of the thermo-hydro-mechanical coupling mechanisms of geomaterials subjected to various environmental impact. This dissertation presents a multiphysical computational framework dedicated to address the issues related to those unconventional applications. Our objective is not only incorporating multiphysical coupling effects at the constitutive laws, but also taking into account the nonlocal effects originated from the flow of pore-fluid, thermal convection and diffusion among solid and fluid constituents, and crystallization and recrystallization of crystals in the pore space across length scales. By considering these coupling mechanisms, we introduce a single unified model capable of predicting complex thermo-hydro-mechanical responses of geological and porous media across wide spectra of temperature, confining pressure and loading rate. This modeling framework applies to two applications, i.e., the freezing and thawing of frozen soil and the modeling of anisotropic crystal plasticity/fracture response of rock salt. Highlights of the key ingredients of the models cover the stabilization procedure used for the multi-field finite element, the return mapping algorithm for crystal plasticity, the micromorphic regularization of the Modified Cam-Clay model, and the strategy for enhancing computational efficiency of solvers, such as pre-conditioner, adaptive meshing, and internal variable mapping. By introducing the multiphysical coupling mechanisms explicitly, our computational geomechanics model is able to deliver more accurate and consistent results without introducing a significant amount of additional material parameters. In a parallel effort, we analyze the impact of thermo-hydro-mechanical (THM) coupling effects on the dynamic wave propagation and strain localization in a fully saturated softening porous medium. The investigation starts with deriving the characteristic polynomial corresponding to the governing equations of the THM system. The theoretical analysis based on the Abel–Ruffini theorem reveals that the roots of the characteristic polynomial for the THM problem cannot be expressed algebraically. Our analysis concludes that the rate-dependence introduced by multiphysical coupling may not regularize the THM governing equations when softening occurs.
108

Ground source energy in crystalline bedrock - increased energy extraction by using hydraulic fracturing in boreholes

Ramstad, Randi Kalskin January 2004 (has links)
<p>The use of improved equipment and methodology can result in considerable reductions in the drilling costs for medium- to large sized ground source heat pump system in crystalline bedrock. The main point has been to use special techniques within hydraulic fracturing to create a larger heat exchange area in the bedrock, and thus a greater energy extraction per borehole. The energy extraction is based on circulating groundwater.</p><p>Stimulation with hydraulic fracturing is a well known technique in order to improve borehole yields for drinking water-, oil-, and geothermal purposes. A procedure for injection of propping agents in selected borehole sections, and custom-made equipment for hydraulic fracturing in crystalline bedrock, a double packer, have been developed in this study. The propping agents are likely to ensure a permanent improvement of the hydraulic conductivity in a long-run perspective. </p><p>In addition to a pre-test, a comprehensive test programme has been performed at each of the two pilot plants at Bryn and at the former property of Energiselskapet Asker og Bærum (EAB) in Bærum municipality outside Oslo, Norway. A total of 125 stimulations with hydraulic fracturing using water-only and hydraulic fracturing with injection of sand have been performed in 9 boreholes. Test pumping and geophysical logging (temperature, electrical conductivity, gamma radiation, optical televiewer and flow measurements) have been carried out in order to document the effect of the hydraulic fracturing.</p><p>The pilot plants at Bryn and EAB, where the ground source heat pump systems are based on circulating groundwater, have demonstrated the short-period energy extraction, limitations and opportunities of the concept for hydraulic fracturing and increased energy extraction in different geological and hydrogeological areas. The bedrock at Bryn and EAB is characterized as a low-metamorphic sandstone and a nodular limestone, respectively. At Bryn, the five boreholes were organised with a central borehole encircled by four satellite boreholes 13 metres away from the central borehole. The central borehole at EAB was flanked with two boreholes 16 and 20 metres away. In operation mode, groundwater was pumped from the satellite boreholes, heat exchanged, and re-injected into the groundwater magazine via the central borehole. Routine operation of the plants has not yet been initiated.</p><p>The main findings from this study can be summarized as follows:</p><p>•Hydraulic fracturing with water-only results in an overall increase in water yield for the hard rock borehole.</p><p>•Hydraulic fracturing with injection of sand as propping agent also leads to an increased water yield.</p><p>•The use of sand as propping agent seems to be more required in fractures with high counter pressure, in this study higher than approximately 40 bars, compared with fractures with lower counter pressure. The particle size of the sand should also be adjusted to the appearing counter pressure, and injection of coarser sand is recommended in fractures with lower counter pressures.</p><p>•Comparing the results from the hydraulic fracturing performed at Bryn and EAB shows that the pressure levels, required to create new fractures, varied considerably. The maximum pressures present at Bryn were higher than the corresponding pressures at EAB. At Bryn 70% (44 out of 63) of the pressure-time curves from the hydraulic fracturing with water-only were interpreted as initiation or reopening of fractures, while the number for EAB was 97% (36 out of 37). The lower degree of fracturing at Bryn is likely to be a result of high rock stresses and high tensile strength of the bedrock, also confirmed by the results from the rock stress measurements performed at Bryn. Considering the bedrock at EAB, characterized as nodular limestone, the tensile strength is assumed to be less than the values for the low-metamorphic sandstone present at Bryn.</p><p>•The infiltration rate in the central boreholes is a critical factor for the energy extraction and a successful operation of ground source heat pump systems based on circulating groundwater. Results from the short-period circulation tests accomplished at Bryn and EAB show that the infiltration rate in the central borehole at Bryn (approximately 2500 litres/hour) was too low to obtain a satisfactory operation of the plant, while the infiltration rate at EAB (14000 litres/hour) was sufficient to achieve profitability. Under the actual conditions, a reduction in the construction costs, i.e. the drilling costs, for a conventional ground source heat pump system with single U-collectors in vertical boreholes, of more than 50% were achieved for the pilot plant at EAB when the energy extraction from water is more than 105 MWh. The large difference in the infiltration rate between Bryn and EAB was probably related to: (1) Large initial differences in the borehole yield prior to hydraulic fracturing (<560 litres/hour at Bryn and >6300 litres/hour at EAB). Nodular limestone generally has high permeability, while compact sandstone rocks are expected to have low permeability. (2) Hydraulic fracturing was most successful at EAB. (3) The higher rock stress level present at Bryn compared to EAB will increase the tendency to tighten the opened fractures, even the fractures with injected sand •The FEFLOW-modelling of the pilot plant at Bryn and EAB emphasized the important relation between the available heat exchange area in the bedrock, the thermal conductivity of the bedrock, and the energy potential. </p><p>•The increased borehole yields achieved by hydraulic fracturing in this study, and the improved, reliable and cost-effective hydraulic fracturing techniques in crystalline bedrock, will probably increase the interest for groundwater as a domestic water supply for small- to medium sized water works.</p>
109

Ground source energy in crystalline bedrock - increased energy extraction by using hydraulic fracturing in boreholes

Ramstad, Randi Kalskin January 2004 (has links)
The use of improved equipment and methodology can result in considerable reductions in the drilling costs for medium- to large sized ground source heat pump system in crystalline bedrock. The main point has been to use special techniques within hydraulic fracturing to create a larger heat exchange area in the bedrock, and thus a greater energy extraction per borehole. The energy extraction is based on circulating groundwater. Stimulation with hydraulic fracturing is a well known technique in order to improve borehole yields for drinking water-, oil-, and geothermal purposes. A procedure for injection of propping agents in selected borehole sections, and custom-made equipment for hydraulic fracturing in crystalline bedrock, a double packer, have been developed in this study. The propping agents are likely to ensure a permanent improvement of the hydraulic conductivity in a long-run perspective. In addition to a pre-test, a comprehensive test programme has been performed at each of the two pilot plants at Bryn and at the former property of Energiselskapet Asker og Bærum (EAB) in Bærum municipality outside Oslo, Norway. A total of 125 stimulations with hydraulic fracturing using water-only and hydraulic fracturing with injection of sand have been performed in 9 boreholes. Test pumping and geophysical logging (temperature, electrical conductivity, gamma radiation, optical televiewer and flow measurements) have been carried out in order to document the effect of the hydraulic fracturing. The pilot plants at Bryn and EAB, where the ground source heat pump systems are based on circulating groundwater, have demonstrated the short-period energy extraction, limitations and opportunities of the concept for hydraulic fracturing and increased energy extraction in different geological and hydrogeological areas. The bedrock at Bryn and EAB is characterized as a low-metamorphic sandstone and a nodular limestone, respectively. At Bryn, the five boreholes were organised with a central borehole encircled by four satellite boreholes 13 metres away from the central borehole. The central borehole at EAB was flanked with two boreholes 16 and 20 metres away. In operation mode, groundwater was pumped from the satellite boreholes, heat exchanged, and re-injected into the groundwater magazine via the central borehole. Routine operation of the plants has not yet been initiated. The main findings from this study can be summarized as follows: •Hydraulic fracturing with water-only results in an overall increase in water yield for the hard rock borehole. •Hydraulic fracturing with injection of sand as propping agent also leads to an increased water yield. •The use of sand as propping agent seems to be more required in fractures with high counter pressure, in this study higher than approximately 40 bars, compared with fractures with lower counter pressure. The particle size of the sand should also be adjusted to the appearing counter pressure, and injection of coarser sand is recommended in fractures with lower counter pressures. •Comparing the results from the hydraulic fracturing performed at Bryn and EAB shows that the pressure levels, required to create new fractures, varied considerably. The maximum pressures present at Bryn were higher than the corresponding pressures at EAB. At Bryn 70% (44 out of 63) of the pressure-time curves from the hydraulic fracturing with water-only were interpreted as initiation or reopening of fractures, while the number for EAB was 97% (36 out of 37). The lower degree of fracturing at Bryn is likely to be a result of high rock stresses and high tensile strength of the bedrock, also confirmed by the results from the rock stress measurements performed at Bryn. Considering the bedrock at EAB, characterized as nodular limestone, the tensile strength is assumed to be less than the values for the low-metamorphic sandstone present at Bryn. •The infiltration rate in the central boreholes is a critical factor for the energy extraction and a successful operation of ground source heat pump systems based on circulating groundwater. Results from the short-period circulation tests accomplished at Bryn and EAB show that the infiltration rate in the central borehole at Bryn (approximately 2500 litres/hour) was too low to obtain a satisfactory operation of the plant, while the infiltration rate at EAB (14000 litres/hour) was sufficient to achieve profitability. Under the actual conditions, a reduction in the construction costs, i.e. the drilling costs, for a conventional ground source heat pump system with single U-collectors in vertical boreholes, of more than 50% were achieved for the pilot plant at EAB when the energy extraction from water is more than 105 MWh. The large difference in the infiltration rate between Bryn and EAB was probably related to: (1) Large initial differences in the borehole yield prior to hydraulic fracturing (&lt;560 litres/hour at Bryn and &gt;6300 litres/hour at EAB). Nodular limestone generally has high permeability, while compact sandstone rocks are expected to have low permeability. (2) Hydraulic fracturing was most successful at EAB. (3) The higher rock stress level present at Bryn compared to EAB will increase the tendency to tighten the opened fractures, even the fractures with injected sand •The FEFLOW-modelling of the pilot plant at Bryn and EAB emphasized the important relation between the available heat exchange area in the bedrock, the thermal conductivity of the bedrock, and the energy potential. •The increased borehole yields achieved by hydraulic fracturing in this study, and the improved, reliable and cost-effective hydraulic fracturing techniques in crystalline bedrock, will probably increase the interest for groundwater as a domestic water supply for small- to medium sized water works.
110

Evaluation of the Frequency and Time Domain Soil-structure Interaction Analysis Methods against the Hualien Large-scale Seismic Test (LSST) Data

Kabanda, John Samuel 29 November 2013 (has links)
Nonlinear seismic soil-structure interaction (SSI) analyses are often completed using the equivalent linear frequency domain analysis method as it is simple to use and computationally efficient. However, the method is inherently linear and a better strategy is to employ the nonlinear time domain analysis method, which is computer intensive but can more accurately simulate nonlinear soil behavior. In this thesis, the two methods are evaluated using the Hualien LSST field data. For the nonlinear time domain analyses, the utilized Hualien LSST finite element model is initially verified by comparing its linear responses to those obtained via the linear frequency domain analysis method; which is also verified against the multi-step analysis approach. In the frequency domain, the equivalent linear analyses are completed by an industry collaborator. The results show that two methods generate similar responses for the low intensity earthquakes but differ for the more intense and amplified earthquakes.

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