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dc.contributor.advisorO'Kelly, Brendan
dc.contributor.advisorNagel, Thomas
dc.contributor.authorZHANG, LIN
dc.date.accessioned2017-09-15T13:54:58Z
dc.date.available2017-09-15T13:54:58Z
dc.date.issued2017en
dc.date.submitted2017
dc.identifier.citationZHANG, LIN, Undrained Triaxial Experimental Investigations and Hyperviscoplastic Modelling of Peat Materials, Trinity College Dublin.School of Engineering.CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING, 2017en
dc.identifier.otherYen
dc.identifier.urihttp://hdl.handle.net/2262/81758
dc.descriptionAPPROVEDen
dc.description.abstractThis PhD research includes two parts, viz. experimental investigation on the undrained mechanical properties of undisturbed fibrous peat and a finite strain constitutive model within a thermodynamically consistent framework based on the experimental results of the tested peat. From the laboratory investigation, nonlinear behaviour with large strain was observed from the loading-unloading tests on peat. The influence of cell pressure, strain rate, stress relaxation on the constitutive behaviour as well as strain recoveries from unloading were investigated. Relaxation tests were carried out for overstress quantification as well as to obtain the equilibrium state. The tested peat was categorised as a rate-dependent material with equilibrium hysteresis. Structural anisotropy was also investigated by testing the undisturbed vertical and horizontal specimens under the same conditions. Although in the proposed model, the structural anisotropy was not included, the experimental data provided the foundation for the future development of anisotropic constitutive models. The observed material behaviour motivated a rheological model comprising four parallel layers, each consisting of elastic, viscoelastic and elastoplastic elements. The proposed hyperviscoplastic model was derived from the entropy inequality. Each part of the model was verified against their analytical solutions. The model parameter fitting started with the rate-independent equilibrium tests, where the hyperelastoplastic model was fitted to the defined laboratory equilibrium test. Two compression-relaxation tests, carried out at different strain rates, were used for the parameter estimation of the rate-dependent hyperviscoplastic model. The hyperviscoplastic model was validated against five strain rate tests under various load cases as well as an undrained triaxial creep test. The finite strain constitutive model derived within a thermodynamically consistent framework showed its versatility in simulating peat behaviour in various load cases by a good agreement of the experimental results. Also, from the process of the deriving the hyperviscoplastic model, it is perceived that it would be easy to extend the current model with more features in a mathematically and thermomechanically consistent manner.en
dc.language.isoenen
dc.publisherTrinity College Dublin. School of Engineering. Disc of Civil Structural & Environmental Engen
dc.rightsYen
dc.subjectPeat Materialsen
dc.subjectThermodynamically Consistenten
dc.subjectHyperviscoplastic modelen
dc.subjectFinite strainen
dc.subjectUndrained triaxial testsen
dc.subjectLoading-unloading and relaxation testsen
dc.titleUndrained Triaxial Experimental Investigations and Hyperviscoplastic Modelling of Peat Materialsen
dc.typeThesisen
dc.contributor.sponsorTrinity College Dublin (TCD)en
dc.contributor.sponsorIrish Research Council for Science and Engineering Technology (IRCSET)en
dc.type.supercollectionthesis_dissertationsen
dc.type.supercollectionrefereed_publicationsen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnameDoctor of Philosophy (Ph.D.)en
dc.identifier.peoplefinderurlhttp://people.tcd.ie/linzhangen
dc.identifier.rssinternalid177176en
dc.rights.ecaccessrightsopenAccess


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