Dissertations / Theses on the topic 'Liquefaction'
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Butterfield, Katherine J. "Seismic Liquefaction Trigger Mechanisms." Thesis, University of Canterbury. Civil Engineering, 2004. http://hdl.handle.net/10092/1179.
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Three possible mechanisms for the onset of excess pore water pressure generation due to seismic excitation of saturated soil are investigated using downhole array data from sixteen real earthquakes. The downhole data are used to synthesize both stress and strain at various depths within the ground. Stresses, strains and dissipated energy are then investigated as potential liquefaction trigger mechanisms. The hypothesis that the shear strain threshold is a liquefaction trigger mechanism is strongly supported by the results presented here. In all but one case the shear strain threshold accurately predicts the time of pore pressure rise for real earthquakes in the field. Additionally, the onset of energy dissipation is found to signal the initial rise in measured excess pore pressure remarkably accurately. The results suggest a fundamental link between Nemat-Nasser and Shokooh's pore pressure - dissipated energy.density relationship (1979) and Mindlin and Deresiewicz's (1953) theoretical strain threshold. Mindlin and Deresiewicz's work (1953) defined a theoretical strain threshold as the mechanism for the onset of gross sliding, and 'its associated energy dissipation'. Therefore the onset of energy dissipation constitutes a second, independent verification of the strain threshold hypothesis. The relationship between stress invariants and pore pressure increase is less clear. To date there does not appear to be an acceptable theory that describes a trigger mechanism in terms of stress alone.
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Baloyi, Hope. "Algae liquefaction / Hope Baloyi." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8153.
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The liquefaction of algae for the recovery of bio–oil was studied. Algae oil is a non–edible feedstock and has minimal impact on food security and food prices; furthermore, it has been identified as a favourable feedstock for the production of biodiesel and this is attributed to its high oil yield per hectare. Algae oil can be potentially used for fuel blending for conventional diesel. The recovery step for algae oil for the production of biodiesel is costly and demands a lot of energy due to the high water content and size of the algae organism. In this study hydrothermal liquefaction was used for the recovery of oil from algae biomass. Hydrothermal liquefaction uses high water activity in sub–critical water conditions to convert wet biomass to liquid fuel which makes the process more cost effective than pyrolysis and gasification in terms of energy savings on biomass drying costs.
The main objective of this study was to determine suitable liquefaction reaction conditions (reaction temperature, biomass loading and reaction atmosphere) for producing bio–oil from algae and identifying the effects of these conditions on bio–oil yield and properties. Bio–oil properties are a good indication of the quality of the oil product and the significance of the liquefaction reaction conditions. The experiments were carried out in a SS316 stainless steel high pressure autoclave. An environmental scanning electron microscope with integrated energy dispersive spectroscopy was used for the characterisation of the raw algae biomass. The algae biomass was liquefied in water at various temperatures ranging from 280 to 360°C, at different biomass loadings (3 to 9 wt %) and a 5 wt% potassium hydroxide (KOH) for all experiments. The reaction time was held constant at 30 minutes in all experiments performed under CO2 and N2 atmospheres. Chloroform was used to recover the bio–oil oil from the reaction mixture following liquefaction, and the bio–oil was purified by removing chloroform using a vacuum distillation process.
The bio–oil sample was methylated to the fatty methyl esters using trimethyl sulfonium hydroxide solution to determine its composition using gas chromatography. The elemental composition of the bio–oil was analysed using a Flash 2000 organic analyser. The main organic components of the bio–oil were determined using Fourier–transform infrared (FT–IR) spectroscopy. The oil yield was found to be dependent on reaction temperature and biomass loading when liquefaction was done in an inert environment, showing a significant increase at high temperatures and biomass
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loadings. Biomass loading had no significant influence on bio–oil yields at high temperatures in a reducing atmosphere and an average oil yield of 25.28 wt% and 20.91 wt% was obtained under a CO2 atmosphere and a N2 atmosphere at 360°C, respectively. Higher yields of C16 fatty acid were obtained at 320°C at a 3 wt% biomass loading in a CO2 atmosphere. The FTIR analyses showed the presence of oxygenated compounds such as phenols, ketones, aldehydes and ethers. The bio–oil had a reduced O/C ratio as compared to that in the original feedstock, with improved heating values. The reduction in the O/C ratio in the bio–oil indicated that deoxygenation occurred during liquefaction and that the bio–oil produced has good properties for combustion. This study indicates that the bio–oil is well suited for further processing to biodiesel because of the high C16 fatty acid content. Hydrothermal liquefaction could thus be a feasible method for producing bio–oil from Scenedesmus acutus.Thesis (MSc Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.
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Arndt, Alex Michael. "Performance-Based Liquefaction Triggering Analyses with Two Liquefaction Models Using the Cone Penetration Test." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6945.
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This study examines the use of performance-based engineering in earthquake liquefaction hazard analysis with Cone Penetration Test data (CPT). This work builds upon previous research involving performance-based liquefaction analysis with the Standard Penetration Test (SPT). Two new performance-based liquefaction triggering models are presented herein. The two models used in this liquefaction analysis are modified from the case-history based probabilistic models proposed by Ku et al. (2012) and Boulanger and Idriss (2014). Using these models, a comparison is made between the performance-based method and the conventional pseudo-probabilistic method. This comparison uses the 2014 USGS probabilistic seismic hazard models for both methods. The comparison reveals that, although in most cases both methods predict similar liquefaction hazard using a factor of safety against liquefaction, by comparing the probability of liquefaction, the performance-based method on average will predict a smaller liquefaction hazard.
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Kabbani, Dania. "Ultrasound-assisted liquefaction of honey." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/144664.
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Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling. Honey is commonly heated during pasteurization in order to liquefy it and inhibit any microbial growth. However, heating can degrade the main quality parameters of honey.
A better method compared to expensive and time-consuming heating is desirable to pasteurize, accelerate the liquefaction and retard the crystallization process in honey.
The present thesis documents the work done at investigating the effect of the ultrasounds (US) in honey liquefaction, quality alteration and honey decontamination.
Firstly, in Chapter 1, the effect of different combinations of US treatment (power, temperature and duration) on honey liquefaction were evaluated by studying the rheological properties of honey; viscosity behaviour, crystal content, tendency to re-crystallization and thermal properties. Secondly, in Chapter 2, the effects of US on the hydroxymethylfurfural concentration and diastase activities in honey were determined by chemical analysis and compared with that for standard heat-treated honey samples. Thirdly, in Chapter 3, US treatment was investigated for honey decontamination. In addition, the in vitro antimicrobial and antifungal activities of ultrasonicated honey against several types of microorganisms were evaluated.
The results obtained in this research point to a successful application of the ultrasound technology for the liquefaction of honey, as it speeds up its liquefaction, do not degrade the quality and the intrinsic biological activity of honey was neither affected.
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Broomfield, Derek Chad. "Liquefaction potential of paste backfill." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ52879.pdf.
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Ng, Dixon C. "Wood liquefaction with hydriodic acid." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65993.
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Bhattacharya, S. "Pile instability during earthquake liquefaction." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596628.
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A theory of pile failure, based on buckling instability is proposed in this thesis. The main postulate of this theory is that if piles are too slender they require lateral support from the surrounding soil if they are to avoid buckling instability. During earthquake-induced liquefaction, the soil surrounding the pile loses effective confining stress and can no longer offer sufficient support to the pile. A slender pile may then buckle sideways in the direction of least elastic bending stiffness pushing aside the initially liquefied soil, and eventually rupturing under the increased bending moment and shear force. Lateral loading due to slope movement, inertia or out-of-straightness increases lateral deflections, which in turn induces plasticity in the pile and reduces the buckling load, promoting more rapid collapse. These lateral loads are, however, secondary to the basic requirements that piles in liquefiable soil must be checked against Euler's buckling. This theory has been formulated based on a study of fifteen case histories of pile foundation performance and verified using dynamic centrifuge tests. Analytical studies also support this theory of pile failure. A hypothesis of post-buckling pile-soil interaction is also developed to fit the centrifuge test data. Centrifuge tests were designed in level ground to avoid the effects of lateral spreading and the main aim was to study the effect of axial load as soil liquefies. The failure mode observed in the tests was very similar to those observed in the field in laterally spreading soil. It is concluded in this thesis that it is not necessary to invoke lateral spreading of the soil to cause a pile to collapse. The pile may even collapse before lateral spreading starts. The key parameter identified to distinguish whether the pile pushes the soil (buckling) or the soil pushes the pile (lateral spreading) is the slenderness ratio of the pile in the liquefiable region. The critical value of this parameter is approximately 50. In summary, it has been shown that the current codes of practice for pile design omit considerations necessary to avoid buckling in event of soil liquefaction. These codes are inadequate and buckling needs to be addressed. It has been identified that many of the structures designed based on the current codes of practice may be unsafe and may need retrofitting. Therefore, a design method is proposed taking into consideration the buckling effect.
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Barraza, Burgos Juan M. "Liquefaction of beneficiated coal fractions." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294702.
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Tanaka, Kōtarō. "Safety of foundations against liquefaction." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36526.
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Ju, Lei. "Assessment of ship cargo liquefaction." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27907.
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Liquefaction of fine particle cargoes such as unprocessed nickel ore and iron ore, resulting in cargo shift and loss of stability of ships, has caused the loss of many lives in marine casualties over the recent few years. Since the dangers of cargo liquefaction have long been known to the shipping industry, the question of why the phenomenon is resurfacing now would be a legitimate one. Under the requirements of International Maritime Bulk Solid Cargoes (IMSBC) Code adopted by the Maritime Safety Committee of the Organization, the moisture content of the cargo that may liquefy shall be kept less than its Transportable Moisture Limit (TML) in advance of loading, as determined from one of three laboratory test methods specified in IMSBC code. However, the accuracy of these methods is still not understood and the TML result varies particularly when conducted in different laboratories or in different methods for a given sample (Rose, 2014). Considering the ambiguity of testing (unavailability or non-compliance) and the variability in cargo properties and state as well as conditions that can lead to liquefaction (pertaining to ship design and operation and to environmental conditions), it is necessary to investigate the root causes that trigger the phenomenon and address the problem in a comprehensive manner. On the other hand, despite the positive steps that have been taken towards prevention of such shipping accidents, IMSBC code appears to have certain limitations and leaves the shipper responsible to involve the competent authority and the operator for the characterization of the cargo and the hazards it entails for the ship and its crew, if in doubt. This thesis, therefore, gives consideration to the development of the numerical simulation method to the ship cargo liquefaction, which could be feasibly used as a reference and possibly support a suitable regulatory framework for the liquefaction analysis of cargoes.
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Gibbens, Clem Alexander Molloy. "The Use of the Multi-channel Analysis of Surface Waves (MASW) Method as an Initial Estimator of Liquefaction Susceptibility in Greymouth, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2014. http://hdl.handle.net/10092/10244.
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Combined analysis of the geomorphic evolution of Greymouth with Multi-channel Analysis of Surface Waves (MASW) provides new insight into the geotechnical implications of reclamation work.
The MASW method utilises the frequency dependent velocity (dispersion) of planar Rayleigh waves created by a seismic source as a way of assessing the stiffness of the subsurface material. The surface wave is inverted to calculate a shear wave velocity (Park et al., 1999). Once corrected, these shear-wave (Vs) velocities can be used to obtain a factor of safety for liquefaction susceptibility based on a design earthquake.
The primary study site was the township of Greymouth, on the West Coast of New Zealand’s South Island. Greymouth is built on geologically young (Holocene-age) deposits of beach and river sands and gravels, and estuarine and lagoonal silts (Dowrick et al., 2004). Greymouth is also in a tectonically active region, with the high seismic hazard imposed by the Alpine Fault and other nearby faults, along with the age and type of sediment, mean the probability of liquefaction occurring is high particularly for the low-lying areas around the estuary and coastline. Repeated mapping over 150 years shows that the geomorphology of the Greymouth Township has been heavily modified during that timeframe, with both anthropogenic and natural processes developing the land into its current form. Identification of changes in the landscape was based on historical maps for the area and interpreting them to be either anthropogenic or natural changes, such as reclamation work or removal of material through natural events.
This study focuses on the effect that anthropogenic and natural geomorphic processes have on the stiffness of subsurface material and its liquefaction susceptibility for three different design earthquake events. Areas of natural ground and areas of reclaimed land, with differing ages, were investigated through the use of the MASW method, allowing an initial estimation of the relationship between landscape modification and liquefaction susceptibility. The susceptibility to liquefaction of these different materials is important to critical infrastructure, such as the St. John Ambulance Building and Greymouth Aerodrome, which must remain functional following an earthquake. Areas of early reclamation at the Greymouth Aerodrome site have factors of safety less than 1 and will liquefy in most plausible earthquake scenarios, although the majority of the runway has a high factor of safety and should resist liquefaction. The land west of the St. John’s building has slightly to moderately positive factors of safety. Other areas have factors of safety that reflect the different geology and reclamation history.
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Cordon, Michael, LI Zuun, Tyler List, and Aaron Zhang. "The Growth and Production of Crude Oil from Algae Using Hydrothermal Liquefaction and Catalytic Hydrothermal Liquefaction." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297546.
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This report evaluates the current economic outlook of producing algal biofuels as a potential replacement for fossil fuels. The proposed design incorporates two new technologies: hydrothermal liquefaction and catalytic hydrothermal gasification. Both of these technologies provide significant advantages over other dewatering, extraction, and residual biomass processing methods that are typically considered in past models. The design also accounts for the maximal recycle of resources in the system including water, nutrients, carbon dioxide, and heat. Based on current market info, it was shown that the design is not economically feasible at this time. The plant would break even (NPV of $0 at a 40% tax rate) after 30 years if the selling price of the oil is $174 per barrel. A Monte Carlo simulation was established to monitor the effects that different operating conditions have on the commercial viability of the process. In approximately 5% of the scenarios, a positive economic outlook was found for the proposed plant. These parameters include the efficiency of the electric generator, the price of the oil, the price of electricity, the yield out of hydrothermal liquefaction, and the yield of algal biomass out of the growth raceways.
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Ulmer, Kristin Jane. "Development of a Simplified Performance-Based Procedure for Assessment of Liquefaction Triggering Using Liquefaction Loading Maps." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5600.
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Seismically-induced liquefaction has been the cause of significant damage to infrastructure and is a serious concern in current civil engineering practice. Several methods are available for assessing the risk of liquefaction at a given site, each with its own strengths and limitations. One probabilistic method has been shown to provide more consistent estimates of liquefaction risk and can be tailored to the specific needs of a given project through hazard-targeted (i.e. based on return periods or likelihoods) results. This type of liquefaction assessment is typically called “performance-based,” after the Pacific Earthquake Engineering Research (PEER) Center's performance-based earthquake engineering framework. Unfortunately, performance-based liquefaction assessment is not easily performed and can be difficult for practicing engineers to use on routine projects. Previous research has shown that performance-based methods of liquefaction assessment can be simplified into an approximation procedure. This simplification has successfully been completed for the Cetin et al. (2004) empirical, probabilistic standard penetration test -based liquefaction triggering model. Until now, such a simplification has not been performed for another popular liquefaction triggering model developed by Boulanger and Idriss (2012). As some engineers either wish to use or are required to use the Boulanger and Idriss (2012) model in their liquefaction assessments, there is a need for a simplified performance-based method based on this model to supplement that based on the Cetin et al. (2004) model. This thesis provides the derivation of a simplified performance-based procedure for the assessment of liquefaction triggering using the Boulanger and Idriss (2012) model. A validation study is performed in which 10 cities across the United States are analyzed using both the simplified procedure and the full performance-based procedure. A comparison of the results from these two analyses shows that the simplified procedure provides a reasonable approximation of the full performance-based procedure. This thesis also describes the development of liquefaction loading maps for six states and a spreadsheet that performs the necessary correction calculations for the simplified method.
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Chung, Jae-Won. "Development of a geographic information system-based virtual geotechnical database and assessment of liquefaction potential for the St. Louis Metropolitan area." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Chung_09007dcc80483011.pdf.
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Thesis (Ph. D.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 24, 2008) Includes bibliographical references (p. 145-155).
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Mitrani, Helen. "Liquefaction remediation techniques for existing buildings." Thesis, University of Cambridge, 2006. https://www.repository.cam.ac.uk/handle/1810/252017.
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Adalier, Korhan. "Mitigation of earthquake induced liquefaction hazards." online access from Digital Dissertation Consortium access full-text, 1996. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?9635658.
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Bradshaw, Aaron S. "Liquefaction potential of non-plastic silts /." View online ; access limited to URI, 2006. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3248224.
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Mayfield, Roy T. "The return period of soil liquefaction /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10209.
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Lee, Wayne Y. "Numerical modeling of blast-induced liquefaction /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1431.pdf.
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Mei, Huan. "Market risk analysis of coal liquefaction." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5502.
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Thesis (M.S.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains vii, 66 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 55-57).
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Wang, Lijie 1963. "Low severity electrochemical liquefaction of wood." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37693.
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Direct liquefaction of wood with aqueous HI solution to a wood oil product under low severity conditions, atmospheric pressure and low temperature around 125°C, was investigated in two stages. The first stage involved batch reactor studies. The wood-HI liquefaction reaction is fast, nearly complete in as little as 20s when the initial aqueous phase concentration is 57 wt% HI or greater. Yield of the char-type residue, a major problem in other liquefaction processes, is completely eliminated provided the final aqueous phase concentration is 50 wt% HI or above. The performance of this process with wood is better than would be predicted from experiments on the liquefaction of wood components determined separately.Removal of oxygen from polymeric wood components is accomplished with oxidation of I- to I2. The second stage tested a novel concept for closing the HI → I2 → HI loop, an electrochemical liquefaction reactor (ECLR) with liquefaction in the cathode cell where I2 is simultaneously reduced back to I- . Electrolysis of water at the anode generates O2 and the H+ required at the platinum cathode for HI regeneration. Without wood liquefaction, current efficiency for I2 reduction is 90--100% and I2 concentration can be maintained at about 0.1 M, which is about 10% of that without I2 reduction.
Preliminary ECLR tests in batch and batchwise-continuous modes demonstrated simultaneous wood liquefaction and electrochemical reduction of I2 in the presence of the viscous wood oil. Also the iodine content of the crude wood oil is thereby reduced by about 60%, where this limit is imposed by the strong physical association between I2 and various functional groups in the product. Generation of H2, the competitive reaction, can be avoided.
ECLR characteristics were determined from a continuous run in a sealed reactor at a steady aqueous phase concentration of 55 wt% HI with a cathode current density of 0.81 A/cm2 at a cell voltage of 6 V. Carbon base yields were 84.2% crude wood oil product, 4.9% methyl iodide from the lignin methoxy groups and no production of the char-type residue common to other biomass liquefaction processes. Of the I2 produced, 93% would be reduced to HI, the other 7% being I2 associated physically with the product. Of the H+ generated at the anode, about half is used for HI regeneration and half for electrochemical liquefaction reactions as reflected by the exceptionally high levels of hydrogen retention and oxygen removal of the wood oil relative to the wood, above 85% in both cases.
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Promputthangkoon, Panu. "Liquefaction of Sand-Tyre Chip Mixtures." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515469.
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Cloke, M. "Trace element concentrations during coal liquefaction." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378771.
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Soile, Olutola O. "The thermochemical liquefaction of Kraft lignin." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326109.
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GUILLEN, JORGE LUIS CARDENAS. "ELASTO-PLASTICITY MODELLING OF SOIL LIQUEFACTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25812@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Mudanças das propriedades dos solos devido à ação de carregamentos dinâmicos são responsáveis por danos significativos em geo-estruturas, tais como: barragens, estruturas de concentração, fundações, taludes, etc. A ocorrência do fenômeno da liquefação, em materiais suscetíveis como areias fofas saturadas, representa um tipo de resposta desastrosa de solos. O termo liquefação tem sido empregado para descrever uma variedade de fenômenos no qual tem em comum o desenvolvimento de altas poropressões em materiais saturados sem coesão devido a carregamentos monotônicos , transientes ou ciclios. A previsão da liquefação depende de uma adequada análise do comportamento não-drenado do material, em termos do incremento de poropressões e da perda da rigidez da mistura sólido-fluido, durante e após o período de movimento. O estabelecimento das equações governantes é essencial para elaboração de um modelo matemático realista para descrever o comportamento físico deste fenômeno. As equações a srem consideradas são: equação de movimento da fase sólida, a equação do movimento da mistura sólido-fluido , a equação de continuidade da fase fluida, as equações de acoplamento das fases e as equações constitutivas desses materiais. Nesta tese a resposta dinâmica do solo foi investigada numericamente mediante a técnica dos elementos finitos. A discretização espacial das equações governantes foi feita através de método de Galerkin e a discretização temporal pelo método de Newmark Generalizado. Um modelo constitutivo elasto-plástico foi considerado para descrever o comportamento mecânico da fase sólida, desenvolvido a partir de conceitos da generealização da teoria da plasticidade, que apresenta algumas vantagens em relação aos outros modelos baseados na teoria da plasticidade clássica. A implementação computacional foi escrito em fortran 90. Exemplos numéricos analisados nesta tese comprovam tanto a eficiência do modelo constitutivo na predição do comportamento do solo sobre liquefação como a confiabilidade do programa computacional elaborado nesta pesquisa, em termos da rapidez de processamento e da boa precisão dos resultados, quando comparados com soluções analíticas e outros valores numéricos obtidos por vários autores e diferentes modelos constitutivos.
Changes in soil properties due to the action of dynamic loads are responsible for significant damage of geo-structures such as dams, retaining structures,building foundations, slopes, etc. The occurrence of liquefaction phenomena in susceptible materials, such as loose saturated, represents a type of disastrous response of soil, the term liquefaction has been used to refer to a group of phenomena wich have in common the development of high pore pressures in saturated cohesionless mterial due to monotonic, transient, or cyclic loads. The prediction of soil liquefaction depends of an adequate analysis of the behavior of undrained materials, in terms of increase of pore water pressure and weakening of the solid-fluid mixture, during and after the periodic motion. The establishment of the governing equations is essential to provide a realistic mathematical model to describe the physical behavior of this phenomenon. The system of equations to be considered are: the equilibrium equation of the solid phase, the equilibrium equation of the solid-fluid mixture, the conservation mass of the fluid phase, the coupling equation of phases, and the conservation equations of materials. In this thesis the soil dynamic response was numerically investigated by the finite element method. To obtain the spatial discretization in time was the Generalized Newmark method. An elastic-plastic constitutive model was used to describe the mechanical behavior of the solid phase. This model was developed in the framework of the generalized theory of plasticity, wich has some advantages when compared with other models based on the classical plasticity theory. The computacional implementation was written in fortran 90. Numerical examples considered in this thesis demonstrate the efficiency of the constitutive model to simulated the predicted behavior of soil under liquefaction as well as the reliability of the software developed in this research, in terms of computational effort and good accuracy of the results, when compared with some analytical solutions and other numerical values obtained by various authors and different constitutive models.
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Hashash, Youssef M. A. "Liquefaction probability mapping in greater Boston." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14559.
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Liao, Samson Sim Cheng. "Statistical modelling of earthquake-induced liquefaction." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14976.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Includes bibliographies.
by Samson Sim Cheng Liao.
Ph.D.
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Laureano-Perez, Lizbeth. "Carbon products from coal liquefaction fractions." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1618.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xvi, 182 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 98-100).
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Lee, Wayne Yeung. "Numerical Modeling of Blast-Induced Liquefaction." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/524.
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A research study has been conducted to simulate liquefaction in saturated sandy soil induced by nearby controlled blasts. The purpose of the study is to help quantify soil characteristics under multiple and consecutive high-magnitude shock environments similar to those produced by large earthquakes. The simulation procedure involved the modeling of a three-dimensional half-space soil region with pre-defined, embedded, and strategically located explosive charges to be detonated at specific time intervals. LS-DYNA, a commercially available finite element hydrocode, was the solver used to simulate the event. A new geo-material model developed under the direction of the U.S. Federal Highway Administration was applied to evaluate the liquefaction potential of saturated sandy soil subjected to sequential blast environments. Additional procedural enhancements were integrated into the analysis process to represent volumetric effects of the saturated soil's transition from solid to liquid during the liquefaction process. Explosive charge detonation and pressure development characteristics were modeled using proven and accepted modeling techniques. As explosive charges were detonated in a pre-defined order, development of pore water pressure, volumetric (compressive) strains, shear strains, and particle accelerations were carefully computed and monitored using custom developed MathCad and C/C++ routines. Results of the study were compared against blast-test data gathered at the Fraser River Delta region of Vancouver, British Columbia in May of 2005 to validate and verify the modeling procedure's ability to simulate and predict blast-induced liquefaction events. Reasonable correlations between predicted and measured data were observed from the study.
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Taghipour, Alireza. "Fractional distillation of hydrothermal liquefaction Biocrude." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213838/1/Alireza_Taghipour_Thesis.pdf.
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This thesis describes fractional distillation as an upgrading method for improving the quality of hydrothermal liquefaction (HTL) biocrude as a green-based biofuel. Firstly, as a part of the biomass to fuel pathway, aqueous phase recycling in the HTL process increased the yield of biocrude production and reduced the nitrogen content. Secondly, fractional distillation improved the biocrude quality (e.g., lower nitrogen content, viscosity, etc), co-processing ability (with conventional fuels) and improved stability during storage. Finally, the learnings from fractional distillation facilitated more accurate process modelling of biocrude assisting biocrude application in the current fossil fuel supply chain.
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Andersen, Paul Joseph Walsh. "Performance of a full-scale Rammed Aggregate Pier group in silty sand based on blast-induced liquefaction testing in Emilia-Romagna, Italy." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8530.
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To investigate the liquefaction mitigation capability of Rammed Aggregate Piers® (RAP) in silty sand, blast liquefaction testing was performed at a soil profile treated with a full-scale RAP group relative to an untreated soil profile. The RAP group consisted of 16 piers in a 4x4 arrangement at 2 m center-to-center spacing extending to a depth of 9.5 m. Blasting around the untreated area induced liquefaction (ru ≈1.0) from 3 m to 11 m depth, producing several large sand boils, and causing settlement of 10 cm. In contrast, installation of the RAP group reduced excess pore water pressure (ru ≈0.75), eliminated sand ejecta, and reduced average settlement to between 2 to 5 cm when subjected to the same blast charges. Although the liquefaction-induced settlement in the untreated area could be accurately estimated using the CPT-based settlement approach proposed by Zhang et al. (2002), settlement in the RAP treated area was significantly overestimated with the same approach even after considering RAP treatment-induced densification. Analyses indicate that settlement after RAP treatment could be successfully estimated from elastic compression of the sand and RAP acting as a composite material. The composite reinforced soil mass, surrounded by liquefied soil, transferred load to the base of the RAP group inducing settlement in the non-liquefied sand below the group. This test program identifies a mechanism that explains how settlement was reduced for the RAP group despite the elevated ru values in the silty sands that are often difficult to improve with vibratory methods.
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ELHUSSIEN, HUSSIEN Eldod. "NON- CATALYTIC TRANSFER HYDROGENATION IN SUPERCRITICAL CO2 FOR COAL LIQUEFACTION." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1409.
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This thesis presents the results of the investigation on developing and evaluating a low temperature (<150oC) non - catalytic process using a hydrogen transfer agent (instead of molecu-lar hydrogen) for coal dissolution in supercritical CO2. The main idea behind the thesis was that one hydrogen atom from water and one hydrogen atom from the hydrogen transfer agent (HTA) were used to hydrogenate the coal. The products of coal dissolution were non-polar and polar while the supercritical CO2, which enhanced the rates of hydrogenation and dissolution of the non-polar molecules and removal from the reaction site, was non-polar. The polar modifier (PM) for CO2 was added to the freed to aid in the dissolution and removal of the polar components. The addition of a phase transfer agent (PTA) allowed a seamless transport of the ions and by-product between the aqueous and organic phases. DDAB, used as the PTA, is an effective phase transfer catalyst and showed enhancement to the coal dissolution process. COAL + DH- +H2O COAL.H2 + DHO-- This process has a great feature due to the fact that the chemicals were obtained without requir-ing to first convert coal to CO and H2 units as in indirect coal liquefaction. The experiments were conducted in a unique reactor set up that can be connected through two lines. one line to feed the reactor with supercritical CO2 and the other connected to gas chromatograph. The use of the supercritical CO2 enhanced the solvent option due to the chemical extraction, in addition to the low environmental impact and energy cost. In this thesis the experiment were conducted at five different temperatures from atmos-pheric to 140°C, 3000 - 6000 psi with five component of feed mixture, namely water, HTA, PTA, coal, and PM in semi batch vessels reactor system with a volume of 100 mL. The results show that the chemicals were obtained without requiring to first convert coal to CO and H2 units as in indirect coal liquefaction. The results show that the conversion was found to be 91.8% at opti-mum feed mixtures values of 3, 1.0 and 5.4 for water: PM, HTA: coal, water: coal respectively. With the oil price increase and growing in energy demand, the coal liquefaction remain afforda-ble and available energy alternative.
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Strand, Spencer R. "Liquefaction Mitigation Using Vertical Composite Drains and Liquefaction Induced Downdrag on Piles: Implications for Deep Foundation Design." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2330.pdf.
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Wright, Alexander David. "Comparison of Performance-Based Liquefaction Initiation Analyses Between Multiple Probabilistic Liquefaction Models Using the Standard Penetration Test." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3710.
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For the most recent and correct article, please click here: http://ascelibrary.org/doi/abs/10.1061/9780784412787.086
This study examines the use of performance-based approaches in liquefaction hazard analysis. Two new methods of performance-based liquefaction initiation analysis are proposed which use the works of Juang et al. (2012) and Boulanger and Idriss (2012). Further advances are made by incorporating the performance-based magnitude scaling factors as proposed by Cetin et al. (2012). Using these new equations a comparative study is made between the three methods. Further comparisons are made between the performance-based approaches and the more widely used deterministic approaches. The comparisons reveal that on average for the 11 sites used in this study, the performance-based approaches tend to be slightly less conservative than deterministic approaches overall, with large differences possible for some locations in the country. They also reveal that the newer performance-based approaches are generally less conservative than the approach proposed by Kramer and Mayfield (2007). Some cases where this relationship does not hold true and the new relationships are more conservative are outlined.
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Linton, Nicholas James. "Gravel Liquefaction Assessment with the Dynamic Penetration Test at Non-Liquefaction Sites in Valdez, Alaska and L'Aquila, Italy." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/8963.
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The development of a reliable, and cost-effective in-situ method for characterizing the liquefaction potential of gravelly soils is a considerable challenge for engineers and researchers. The ability to accurately characterize the liquefaction potential of gravelly soils is an important consideration at port facilities and dams for example. The Dynamic Penetration Test (DPT) provides a reliable and cost-effective method for evaluating the liquefaction resistance of gravelly soils. Probabilistic liquefaction triggering curves based on DPT field data have been developed from data collected at 47 sites in China. However, using the DPT-based liquefaction curves for locations outside of the Chengdu plain in China where the data for the triggering curves were gathered may yield unreliable results. To improve the reliability of the DPT-based liquefaction triggering curves additional DPT field data form outside of the Chengdu plain is required. In total seven new non-liquefaction DPT case histories are presented in this report. Two of the case histories are based on DPT field data from Valdez, Alaska. The remaining five case histories were developed from DPT field data from L'Aquila, Italy. When plotted on the liquefaction triggering curves based only on the DPT data obtained in the Chengdu plain three of the seven data points plot in a position that indicates a considerable possibility of liquefaction despite these case histories being from locations where liquefaction did not occur. Roy (2021) developed new DPT-based liquefaction triggering curves with these seven new non-liquefaction case histories, DPT filed data from other sites around the world, and the DPT field data from the Chengdu plain. The three data points from the new case histories presented in this report that had a considerable probability of liquefaction when plotted on the curve developed only with the data from the Chengdu plain had a significantly lower probability of liquefaction when plotted on the new DPT-based liquefaction triggering curves. One of the data points from Valdez, Alaska decreased from a probability of liquefaction of around 50% to a probability of liquefaction of less than 30% when plotted on the new DPT-based liquefaction triggering curves. The reliability of DPT-based liquefaction triggering curves will continue to increase as the amount of available DPT data increases.
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Error, Braden Michael. "Development of a Simplified Performance-Based Procedure for the Assessment of Liquefaction-Induced Settlements Using Liquefaction Loading Maps." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/7210.
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Liquefaction-induced settlement can cause extensive damage to infrastructure. Quantifying the amount of settlement that may occur after an earthquake is crucial to seismic design. The Pacific Earthquake Engineering Research (PEER) Center developed performance-based earthquake engineering (PBEE) as a probabilistic framework to characterize the risks associated with a seismic event. When applied to liquefaction-induced settlement, the PBEE framework provides a more complete and accurate representation of liquefaction hazard than other more conventional evaluation methods. Performance-based engineering is not widely used in practice, however, due to its complexity. In an attempt to make performance-based engineering methods more accessible to engineers for routine projects, this thesis derives a simplified map-based procedure to evaluating performance-based post-liquefaction settlements. A simplified PBEE procedure is developed for the Cetin et al. (2009) and Ishihara and Yoshimine (1992) empirical post-liquefaction volumetric strain models. The simplified map-based procedure involves obtaining a hazard-targeted value of vertical strain for a reference soil layer which is then adjusted using site-specific soil parameters to assess the liquefaction-induced settlement hazard at a particular location. This thesis derives the equations needed to perform a simplified analysis. The simplified procedure presented herein is then validated in which 15 cities across the United States are analyzed using both the simplified procedure and the full performance-based procedure. The simplified procedure is shown to adequately estimate a full performance-based procedure for post-liquefaction settlement. This thesis also presents SPLIQ, a spreadsheet tool that streamlines the derived simplified procedure in a single, user-friendly program.
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Struckmeier, Vera. "A computational model for seismically induced liquefaction." Braunschweig Mechanik-Zentrum der Techn. Univ, 2007. http://d-nb.info/997386584/34.
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Luna, Ronaldo. "Liquefaction evaluation using a spatial analysis system." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19413.
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Wang, Rui. "Mechanism of catalysed solvent-mediated coal liquefaction." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/10810.
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This thesis describes a study of the control of the reaction chemistry of the coal dissolution stage of a two-stage coal liquefaction process through the use of catalysts to produce coal liquids more amenable to secondary upgrading, particular emphasis being placed on investigating the feasibility of using "spent" or "deactivated" catalysts from, for example, upgrading of coal-derived liquids, to promote solvent-mediated coal dissolution in an inert atmosphere, such systems having an appreciable impact on process economICS. The coal dissolution reaction was carried out using a tubing bomb micro-reactor, primarily, with British Point of Ayr coal in recycle solvent using a range of Mo based catalysts, both fresh and "spent", under a variety of reaction conditions. Initially the influence of the catalysts on single model solvents, such as tetralin, 9, I O-dihydroanthracene and phenanthrene, and binary and ternary blends of these model solvent was investigated in order to establish whether the catalysts had any effect on the solvent itself and/or on any interaction between them. This work demonstrated that the catalysts did indeed exert an effect on the reaction chemistry of the solvents. In all instances the catalysts were effective in promoting the dehydrogenation of the solvents and this reaction can be used as a base of ranking various catalysts. It has been found from the coal dissolution investigation that the coal dissolution under the reaction conditions used, is primarily a thermolytic process. The temperature for significant coal dissolution with a IS min reaction period was 3S0°C and the reaction was complete within 30 min at 42S°C. Increase in temperature above 3S0°C increased coal dissolution and evidence was obtained to indicate some merit in operating at a temperature as high as 4S0°C, but at short reaction time. The influence of the catalyst was to enhance the yield of low molecular weight materials in the dissolution products and in this way benefited the first stage of a two-stage coal liquefaction process. The catalytic activity was maintained at low concentration of Mo 0.01 wt% (daf coal). The rate of coal dissolution is highly coal rank dependent with the higher rank coals showing little propensity for dissolution. On the other hand, limited evidence was obtained indicating that the blending of coals, which are susceptible to dissolution, may be advantageous with some synergistic effects
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McQueen, Paul. "Catalysis deactivation in staged direct coal liquefaction." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/746.
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Staats, Wayne Lawrence. "Analysis of a supercritical hydrogen liquefaction cycle." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45208.
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Includes bibliographical references (p. 72-76).Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
In this work, a supercritical hydrogen liquefaction cycle is proposed and analyzed numerically. If hydrogen is to be used as an energy carrier, the efficiency of liquefaction will become increasingly important. By examining some difficulties of commonly used industrial liquefaction cycles, several changes were suggested and a readily scalable, supercritical, helium-cooled hydrogen liquefaction cycle was proposed. A novel overlap in flow paths of the two coldest stages allowed the heat exchanger losses to be minimized and the use of a single-phase liquid expander eliminated the pressure reduction losses associated with a Joule-Thomson valve. A simulation program was written in MATLAB to investigate the effects of altering component efficiencies and various system parameters on the cycle efficiency. In addition to performing the overall cycle simulations, several of the system components were studied in greater detail. First, the required volume of the ortho-para catalyst beds was estimated based on published experimental data. Next, the improvement in cycle efficiency due to the use of a single-phase liquid expander to reduce the pressure of the hydrogen stream was estimated. Finally, a heat exchanger simulation program was developed to verify the feasibility and to estimate the approximate size of the heat exchangers in the cycle simulation. For a large, 50-ton-per-day plant with reasonable estimates of achievable component efficiencies, the proposed cycle offered a modest improvement in efficiency over the current state of the art. In comparison to the 30-40% Second Law efficiencies of today's most advanced industrial plants, efficiencies of 39-44% were predicted for the proposed cycle, depending on the heat exchange area employed.
by Wayne Lawrence Staats, Jr.
S.M.
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Daftari, Abbas. "New approach in prediction of soil liquefaction." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-192304.
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Liquefaction is the phenomena when there is loss of strength in saturated and cohesion-less soils because of increased pore water pressures and hence reduced effective stresses due to dynamic loading. It is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading.
In this study, after the short review of liquefaction definition, the models of prediction and estimation of liquefaction were considered. Application of numerical modelling with two major software (FLAC & PLAXIS) for the Wildlife site liquefaction, under superstition earthquake in 1987 were compared and analysed.
Third step was started with introduction of Fuzzy logic and neural network as two common intelligent mathematical methods. These two patterns for prediction of soil liquefaction were combined. The “Neural network- Fuzzy logic-Liquefaction- Prediction” (NFLP) was applied for liquefaction prediction in Wildlife site. The results show the powerful prediction of liquefaction happening with high degree of accuracy in this case.
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Xu, Haixia. "Wave-induced liquefaction processes in marine sediments." Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/e9c70159-a416-49d7-b055-968991e55414.
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An investigation for seabed liquefaction induced by progressive water waves is vital for the protection of marine structures from damage to the structure foundations. The residual liquefaction in sedimentary seabed has been found to be of progressive nature and experiments have also demonstrated that the liquefied soil behaves as a visco-elastic-plastic material. Building on the previous research, this work develops various numerical models to re-examine the key factors which influence the progressive liquefaction processes.To investigate the effect of randomness of wave height on seabed liquefaction, ensemble modelling approach is adopted in a two-layer inviscid fluid flow model, whereby the liquefied soil is treated as inviscid heavy fluid. Probabilistic study of soil liquefaction processes indicates that the random wave-induced liquefaction depth is much larger than that corresponding to regular waves with Equivalent Wave Height. The larger liquefaction depth in random waves is shown to be due to the fact that the highest waves rather than average waves in the wave series tend to dominate the liquefaction extent. It is also shown that the time needed for liquefaction to reach the bottom of investigated domain can vary considerably in the case of random wave time series. The longer period of low waves between the large waves will delay the time for the maximum liquefaction depth to be reached within the simulation time considered. The current design practice, which is entirely based on the regular wave models, can under-estimate the liquefaction depth and lead to unsafe design. It is recommended that the evaluation of liquefaction potential due to random waves should be based on the appropriate extreme values in the wave height distribution rather than average values such as significant wave height or root-mean-square wave height.Secondly, a two-layer viscous fluid model representing a visco-elastic-plastic liquefied soil is constructed. The upper seawater and liquefied soil were treated as viscous fluid and described by the linearized Navier-Stokes and continuity equations. Simulation results confirmed that shear stress solved from infinite seabed solution can lead to significant errors and underestimate the liquefaction depth. The viscosity of liquefied soil computed by the present model reveals a clear state change, i.e., from viso-elastic stage to visco-plastic stage, due to the increasing deformation rate of liquefied soil layer. The strain rate dependent viscosity can influence the liquefaction process relative to constant viscosity although not very strongly. Deeper liquefaction is more likely to take place in shallower water under the same wave loading. Smaller soil permeability prevents residual pore pressure dissipation and consequently enhances the liquefaction.Finally, the two-layer viscous model is extended to a multi-layer model in order to investigate the effect of stratification of liquefied soil layer. It is found that the liquefaction depth estimated using the N-layer model is sensitive to water content, which is contrary to that predicted by the two-layer model. The continuously increasing liquefied soil density is found to overcome the numerical difficulty in achieving a convergent viscosity. The predicted liquefied soil viscosity, liquefaction depth and interface wave amplitude are all different from that predicted by constant water content model. The sensitivity of liquefaction to both wave and soil parameters are enhanced by the stratification of liquefied soil viscosity and density. The thickness of seabed is also found to affect liquefaction but the trend is not monotonic. There seems to be a critical seabed thickness, at which the effect of seabed thickness on liquefaction reverses. Below the critical thickness, the liquefaction depth is smaller due to the relatively short drainage distance in thinner seabed but beyond the critical thickness, increasing seabed thickness damps the wave energy and consequently prevents the liquefaction. Seabed liquefaction is very sensitive to the soil plastic model parameters contained in the residual pore pressure build-up equation. Therefore, a reliable procedure for quantifying these parameters is extremely important.
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Tarragó, Munté Daniel. "Hydraulic fills liquefaction : effect on quay stability." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672274.
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The starting point of this thesis is the failure of part of a quay wall under construction. The quay was divided in two phases, failure affected Phase 1 only. The failure and all the relevant associated information on quay design, construction and monitoring records are described in detail together with the results of a site investigation campaign carried out after the failure. Flow liquefaction of the hydraulic fill emplaced behind the quay wall was the main cause of the failure. The state of the hydraulic fill in the quay area is assessed in the light of the current understanding of the phenomenon and of a number of flow liquefaction criteria. In addition, an elastoplastic constitutive law is described that is capable to simulate the undrained brittleness behaviour that underlies the phenomenon of flow liquefaction. It is a critical-state model that incorporates the concept of state parameter. Subsequent finite element analyses are able to reproduce satisfactorily the behaviour of the quay during construction and the features and circumstances of the failure. Two possible triggering mechanisms are identified that can explain the failure: spontaneous liquefaction, or liquefaction of a limited zone caused by the concurrent construction of an embankment. A parametric study verifies the robustness of the simulation and the dependence of stability on the degree of brittleness of the hydraulic fill. The same type of analysis of quay Phase 2, not involved in the failure, revealed that the margin of safety was small if the hydraulic fill liquefied. Soil improvement measures were implemented and an extensive monitoring system was installed. Construction of quay Phase 2 was completed applying the observational method that involved a continuous check of the monitoring data and its comparison with numerical simulation results. An additional site investigation confirmed that the soil improvement measures had succeeded in removing both the flow and the cyclic liquefaction potential of the hydraulic fill, according to currently accepted criteria. The Phase 1 quay involved in the failure was reconstructed with mainly terrestrial fill with no flow potential liquefaction, as confirmed by the corresponding site investigation.
Based on the experience gathered in the case and on the research carried out, an operational scheme dealing with quays constructed with hydraulic fills susceptible to flow liquefaction is proposed. It consists of a protocol to evaluate liquefaction potential of hydraulic fills, the use of a constitutive law capable of simulating flow liquefaction, the implementation of soil improvement measures to reduce flow liquefaction potential and the employment of a monitoring system to control the quay wall behaviour during construction and to provide data for comparison with numerical analyses results.El punto de partida de esta tesis es la rotura de parte de un muelle en construcción. El muelle estaba dividido en dos fases, la rotura solo afectó a la Fase 1. La rotura y toda la información relevante sobre el diseño, construcción y resultados de la auscultación se describen en detalle junto con los resultados de la campaña de reconocimiento efectuada después de la rotura. La licuefacción estática del relleno hidráulico colocado en el trasdós del muro del muelle fue la causa principal de la rotura. El estado del relleno hidráulico se estudia en el marco del conocimiento actual del fenómeno y de una serie de criterios de licuefacción existentes. Además, se describe un modelo constitutivo elasto-plástico capaz de simular el comportamiento frágil no drenado que subyace al fenómeno de licuefacción estática. Es un modelo de estado crítico que incorpora el concepto de parámetro de estado. Los consiguientes análisis de elementos finitos reproducen satisfactoriamente el comportamiento del muelle durante la construcción, así como las características y circunstancias de la rotura. Se identifican dos posibles mecanismos desencadenantes que explican la rotura: licuefacción espontánea o licuefacción de una zona limitada del relleno hidráulico debido a la simultánea construcción de una mota. Un estudio paramétrico verifica la solidez de las simulaciones y la dependencia que presenta la estabilidad del grado de fragilidad del relleno hidráulico. Análisis similares de la Fase 2, no involucrada en la rotura, revelaron que el margen de estabilidad era reducido en caso de que el relleno hidráulico sufriera licuefacción. Se implementaron diversas medidas de mejora del terreno y se instaló un extenso sistema de monitorización. La construcción de la Fase 2 se completó usando el método observacional que implicaba una observación continua de los datos de instrumentación y su comparación con los resultados de las simulaciones numéricas. Un reconocimiento del terreno adicional confirmó que las medidas de mejora del terreno habían conseguido eliminar el potencial de licuefacción, tanto estática como cíclica, del relleno hidráulico. La Fase 1 del muelle involucrada en la rotura se reconstruyó con relleno terrestre sin potencial de licuefacción de acuerdo con los datos del reconocimiento del terreno efectuado. En base a la experiencia y trabajos realizados en este caso, se propone un esquema de actuación para casos de muelles construidos con relleno hidráulico potencialmente licuefactable. Este esquema consta de un protocolo para evaluar el potencial de licuefacción de rellenos hidráulicos, el uso de una ley constitutiva capaz de simular apropiadamente la licuefacción estática, la implementación de un conjunto de medidas de mejora del terreno para eliminar el potencial de licuefacción estática y la instalación de un sistema de auscultación para controlar el comportamiento del muelle durante la construcción y proporcionar datos para comparar con los resultados de los análisis numéricos.
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Hayati, Hossein. "Characterizing liquefaction resistance of aged sand deposits." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1246545673/.
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Taiebat, Hossein Ali. "THREE DIMENSIONAL LIQUEFACTION ANALYSIS OF OFFSHORE FOUNDATIONS." Thesis, The University of Sydney, 1999. http://hdl.handle.net/2123/499.
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This thesis presents numerical techniques which have been developed to analyse three dimensional problems in offshore engineering. In particular, the three dimensional liquefaction analysis of offshore foundations on granular soils is the main subject of the thesis. The subject matter is broadly divided into four sections: 1)Development of an efficient method for the three dimensional elasto?plastic finite element analysis of consolidating soil through the use of a discrete Fourier representation of field quantities. 2)Validation of the three dimensional method through analyses of shallow offshore foundations subjected to three dimensional loading and investigation of the yield locus for foundations on purely cohesive soils. 3)Formulation of governing equations suitable for three dimensional liquefaction analyses of offshore foundations founded on granular soil, presentation of a method for liquefaction analyses, and application of the method in modified elastic liquefaction analyses of offshore foundations. 4)Application of a conventional elasto?plastic soil model in the liquefaction analyses of offshore foundations using the three dimensional finite element method. The finite element method developed in this thesis provides a rigorous and efficient numerical tool for the analysis of geotechnical problems subjected to three dimensional loading. The efficiency of the numerical tool makes it possible to tackle some of the problems in geotechnical engineering which would otherwise need enormous computing time and thus would be impractical. The accuracy of the numerical scheme is demonstrated by solving the bearing capacity problem of shallow foundations subjected to three dimensional loading. The generalized governing equations and the numerical method for liquefaction analyses presented in this thesis provide a solid base for the analysis of offshore foundations subjected to cyclic wave loading where they are founded on potentially liquefiable soil. The practicability of the numerical scheme is also demonstrated by a modified elastic liquefaction analysis of offshore foundations. The liquefaction phenomenon is redefined in the context of the conventional Mohr?Coulomb model, so that a relatively simple and practical model for elasto?plastic liquefaction analysis is presented. The three dimensional finite element method together with the numerical scheme for liquefaction analysis and the elasto?plastic soil model provide a suitable practical engineering tool for exploring the responses of offshore foundations subjected to cyclic wave loading.
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Taiebat, Hossein Ali. "THREE DIMENSIONAL LIQUEFACTION ANALYSIS OF OFFSHORE FOUNDATIONS." University of Sydney. Civil Engineering, 1999. http://hdl.handle.net/2123/499.
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This thesis presents numerical techniques which have been developed to analyse three dimensional problems in offshore engineering. In particular, the three dimensional liquefaction analysis of offshore foundations on granular soils is the main subject of the thesis. The subject matter is broadly divided into four sections: 1)Development of an efficient method for the three dimensional elasto?plastic finite element analysis of consolidating soil through the use of a discrete Fourier representation of field quantities. 2)Validation of the three dimensional method through analyses of shallow offshore foundations subjected to three dimensional loading and investigation of the yield locus for foundations on purely cohesive soils. 3)Formulation of governing equations suitable for three dimensional liquefaction analyses of offshore foundations founded on granular soil, presentation of a method for liquefaction analyses, and application of the method in modified elastic liquefaction analyses of offshore foundations. 4)Application of a conventional elasto?plastic soil model in the liquefaction analyses of offshore foundations using the three dimensional finite element method. The finite element method developed in this thesis provides a rigorous and efficient numerical tool for the analysis of geotechnical problems subjected to three dimensional loading. The efficiency of the numerical tool makes it possible to tackle some of the problems in geotechnical engineering which would otherwise need enormous computing time and thus would be impractical. The accuracy of the numerical scheme is demonstrated by solving the bearing capacity problem of shallow foundations subjected to three dimensional loading. The generalized governing equations and the numerical method for liquefaction analyses presented in this thesis provide a solid base for the analysis of offshore foundations subjected to cyclic wave loading where they are founded on potentially liquefiable soil. The practicability of the numerical scheme is also demonstrated by a modified elastic liquefaction analysis of offshore foundations. The liquefaction phenomenon is redefined in the context of the conventional Mohr?Coulomb model, so that a relatively simple and practical model for elasto?plastic liquefaction analysis is presented. The three dimensional finite element method together with the numerical scheme for liquefaction analysis and the elasto?plastic soil model provide a suitable practical engineering tool for exploring the responses of offshore foundations subjected to cyclic wave loading.
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Davenport, George Andrew 1965. "A process control system for biomass liquefaction." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/558114.
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Upadhyaya, Sneha. "Development of an Improved and Internally-Consistent Framework for Evaluating Liquefaction Damage Potential." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95941.
Full textAbstract:
Soil liquefaction continues to be one of the leading causes of ground failure during earthquakes, resulting in significant damage to infrastructure around the world. The study presented herein aims to develop improved methodologies for predicting liquefaction triggering and the consequent damage potential such that the impacts of liquefaction on natural and built environment can be minimized. Towards this end, several research tasks are undertaken, with the primary focus being the development of a framework that consistently and sufficiently accounts for the mechanics of liquefaction triggering and surface manifestation. The four main contributions of this study include: (1) development of a framework for selecting an optimal factor of safety (FS) threshold for decision making based on project-specific costs of mispredicting liquefaction triggering, wherein the existing stress-based "simplified" model is used to predict liquefaction triggering; (2) rigorous investigation of manifestation severity index (MSI) thresholds for distinguishing cases with and without manifestation as a function of the average inferred soil-type within a soil profile, which may be employed to more accurately estimate liquefaction damage potential at sites having high fines-content, high plasticity soils; (3) development of a new manifestation model, termed Ishihara-inspired Liquefaction Severity Number (LSNish), that more fully accounts for the effects of non-liquefiable crust thickness and the effects of contractive/dilative tendencies of soil on the occurrence and severity of manifestation; and (4) development of a framework for deriving a "true" liquefaction triggering curve that is consistent with a defined manifestation model such that factors influential to triggering and manifestation are handled more rationally and consistently. While this study represents significant conceptual advance in how risk due to liquefaction is evaluated, additional work will be needed to further improve and validate the methodologies presented herein.Doctor of Philosophy
Soil liquefaction continues to be one of the leading causes of ground failure during earthquakes, resulting in significant damage to infrastructure around the world (e.g., the 2010-2011 Canterbury earthquake sequence in New Zealand, 2010 Maule earthquake in Chile, and the 2011 Tohoku earthquake in Japan). Soil liquefaction refers to a condition wherein saturated sandy soil loses strength as a result of earthquake shaking. Surface manifestations of liquefaction include features that are visible at the ground surface such as sand boils, ejecta, cracks, and settlement. The severity of manifestation is often used as a proxy for damage potential of liquefaction. The overarching objective of this dissertation is to develop improved models for predicting triggering (i.e., occurrence) and surface manifestation of liquefaction such that the impacts of liquefaction on the natural and built environment can be minimized. Towards this end, this dissertation makes the following main contributions: (1) development of an approach for selecting an appropriate factor of safety (FS) against liquefaction for decision making based on project-specific consequences, or costs of mispredicting liquefaction; (2) development of an approach that allows better interpretations of predictions of manifestation severity made by the existing models in profiles having high fines-content, high plasticity soil strata (e.g., clayey and silty soils), given that the models perform poorly in such conditions; (3) development of a new model for predicting the severity of manifestation that more fully accounts for factors controlling manifestation; and (4) development of a framework for predicting liquefaction triggering and surface manifestation such that the distinct factors influential to each phenomenon are handled more rationally and consistently.
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Shaw, John Michael. "Novel design criteria for direct coal liquefaction reactors." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25971.
Full textAbstract:
A semi-batch Direct Coal Liquefaction facility was designed and constructed in order to examine the impact of process variables on coal liquefaction kinetics. A series of parametric investigations involving bituminous, sub-bituminous coals and lignite were performed. The process variables included solvent composition, catalyst to coal ratio, the intensity of turbulence, the initial dissolved hydrogen concentration, and the slurry residence time distribution. The results of these investigations showed that process variables have a significant impact on the rates of liquefaction reactions, and that reaction rates for coal and lignite are affected in a similar manner.
The overall rate and maximum extent of liquid and gas production was found to depend on the initial rate of molecular hydrogen transfer to the coal particles, and on the ratio of the intensity of turbulence to the level of catalysis. This latter finding led to the discovery of a persistent dispersed liquid phase within the coal liquefaction environment.
A reaction model, coupling these findings with a simple kinetic scheme, was found to correlate the liquefaction behaviour of bituminous and sub-bituminous coals and lignite, in diverse reaction environments. The experimental results and the reaction model were used to develop novel design criteria for Direct Coal Liquefaction Reactors. Two design optima were identified. One optimum is closely approximated by an existing process. An alternative and potentially preferable optimum is proposed.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate