Coquillay, Sophie (2005) Accounting for small strain non-linear soil behaviour in the circulation of geotechnical structures. PhD thesis, ENPC.
Abstract
The intensive use of urban subsoil and the evolution of the technical regulations require to develop new tools to calculate the displacements caused by the construction of new structures. The performance of usual calculation methods is often inadequate, because they have been developed mainly for the analysis of the pre-failure behaviour of structures; thus in these models, the soil behaviour for small strains is not well represented. The soil shear modulus exhibits significant variations between the field of very small strains and the field of usual deformations next to geotechnical structures during their construction. Experience shows that the displacements of a structure can not be correctly evaluated without taking into account these variations. Based on a bibliographical study on elastic-plastic constitutive models with non-linear elasticity, a model with few parameters has been chosen, which is nevertheless able to improve substantially the results of displacement calculations of the geotechnical structures. The proposed model is a slightly modified version of the constitutive model established by Fahey and Carter (1993) which has been combined to a Mohr-Coulomb plastic criterion. The main characteristic of the Fahey- Carter-model is that the shear modulus increases with the mean stress and decreases with the shear stress. The model has been implemented in the finite element code CESAR-LCPC. The identification of its parameters, based on classical soil mechanic tests, was an important part of this work. The model was tested by calculating various structures for which soil data as well as displacement and stress measurements were available. These examples confirm the interest of using a complex constitutive law to produce calculation results similar to the strain and displacement patterns of real structures. The present work was also a contribution to CESAR-LCPC's functionalities improvement.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Magnan, Jean-Pierre |
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| Date: | August 2005 |
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| Board of examiners: | Shahrour, Isam and Modaressi, Arezou and Schmitt, Pierre and Bourgeois, Emmanuel and Magnan, Jean-Pierre |
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| Collection (Fonds): | ENPC |
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| Institution: | ENPC |
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| Subjects: | 8. Earth Sciences and Environmental Engineering |
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| Uncontrolled Keywords: | Calculations in displacements, Calculation and justification of geotechnical structures, Parameters identification, Finite element method, Elastic-plastic model with non-linear elasticity, hyperbolic model of Fahey and Carter, Shear modulus, Small strains, Calculs en déplacements, Dimensionnement et justification des ouvrages géotechniques, Identification des paramètres, Méthode des éléments finis, Modèle élastoplastique à élasticité non linéaire, modèle hyperbolique de Fahey et Carter, Module de cisaillement, Petites déformations |
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