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Analyse numérique des écoulements d'eau et de la consolidation des sols autour des tunnels creusés dans l'argile

Abstract : This work analyses the seepage of ground water towards tunnels excavated in water bearing soils and the induced consolidation in presence of compressible soils. Several bibliographic syntheses are first presented on the problems induced by ground water seepage towards tunnels, on the existing calculation methods to estimate this seepage, on the field observed hydromechanical response of compressible soil masses to tunneling and on the approaches developed to model soil consolidation for grounds with variable water level. Several numerical studies were conducted with the finite element code CESAR-LCPC. The finite element method was used to analyse ground water seepage around tunnels, in permanent and transient flow conditions through two and three dimensional models. Several cases were modeled, considering an undeformable ground, in order to study the influence of soil anisotropy, ground layering, lining permeability and different field measures to reduce seepage effects at the tunnel face during construction. The response of compressible ground to tunneling was analysed with coupled hydro-mechanical calculations using an anisotropic elastoplastic constitutive law: MELANIE. Results were compared to those obtained by drained and undrained calculations. The undrained approach was also used to analyse the response of relatively hard ground to the precutting tunneling method and to study the behaviour of the supporting shell throughout the different construction steps. Furthermore, this thesis contributes to the development of the finite element code CESAR-LCPC. The subroutine of the constitutive law MELANIE was adapted to deal with the variation of preconsolidation pressure and soil elastic response with depth, and to update soil permeability according to ground deformations. An approach was proposed to model soil consolidation for ground with a variable water level, making use of Richards (1931) and Bishop (1960) hypotheses to deal with hydro-mechanical coupling above the water table. This approach was integrated into CESAR-LCPC and applied first to a study of soil consolidation under a foundation loading and secondly to tunnel construction. This method was finally used to analyse a case study: Grimsby tunnel, excavated in soft clayey soil. The study compares the results given by MELANIE with those given by elastic isotropic, elastic anisotropic and isotropic elastoplastic constitutive laws. Different hypotheses were tested for the hydromechanical coupling above the water table. Modeling results were compared to eleven year settlement measurements.
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Submitted on : Monday, October 4, 2010 - 5:25:24 PM
Last modification on : Friday, March 27, 2015 - 4:02:23 PM
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1996TH_ATWA_M_NS20281.pdf
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  • HAL Id : tel-00523305, version 1

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Mohamed Atwa. Analyse numérique des écoulements d'eau et de la consolidation des sols autour des tunnels creusés dans l'argile. Hydrologie. Ecole Nationale des Ponts et Chaussées, 1996. Français. ⟨tel-00523305⟩

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