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Theses

Analyse des mécanismes d'effondrement des couches de sol cohésives renforcées par géosynthétique sur cavité

Abstract : The presence of a natural or anthropogenic cavity in a soil mass represents a major source of risk of disruption to surface infrastructures and, in the most serious cases, loss of human life. In order to limit these risks, a preventive solution is preferred. Reinforcement of embankments by geosynthetics in areas of potential collapse is nowadays a widely used solution because it is considered to be more technically and economically relevant. Indeed, traditional treatments, such as filling cavities or bridging them with reinforced concrete slabs, are very costly and require knowledge of the location of the cavity. Often used for granular backfill, the geosynthetic reinforcement solution is not so used for thin cohesive backfill. More precisely, the scientific obstacles that remain to be overcome are linked to the lack of knowledge of the failure modes of cohesive fillings in cavities and to the action of collapsed blocks on the water table. To answer these questions, a consortium of researchers (3SR), operational staff (INERIS) and a geosynthetics producer (AFITEXINOV) has been formed as part of the REGIC project (Reinforcement by Intelligent Geosynthetics on Natural or Anthropic Cavities), financed by ADEME. One of the objectives of the project is to develop and validate for this type of application the use of an innovative geosynthetic with double stiffnesses and instrumented with optical fibres.This thesis essentially aims to meet one of the project's objectives: the understanding of the collapse mechanisms of embankment reinforced by a geosynthetic sheet in the context of cohesive embankments. It is mainly a numerical modelling work, carried out using the SDEC calculation code that couples discrete elements and finite elements. It enables the simulation of the cavity opening phase and the loading phase up to the rupture of the cohesive fill, which is generally thin. The soil is modelled by discrete elements, the layer by finite elements. Discrete element modelling enables the behaviour of the soil under large deformations to be well reproduced numerically, but above all it enables the block failure of the cohesive soil layer to be represented (geometry of the failure lines, block rotation kinematics, etc.). The finite element method was chosen because it is better suited to simulate the continuity of the geosynthetic layer, its membrane and tensile behaviour (with an evolution of stiffness with the level of traction) and its interaction with the soil. This numerical work was validated by experiments on a reduced scale physical model and by in situ tests, which included in particular the analysis of the efficiency of the innovative geosynthetic whose tensile behaviour is qualified as "inverted bimodulus". Numerical modelling has provided access to variables or quantities that are difficult to measure in the laboratory and on site: distribution of vertical stresses transmitted by the ground to the geosynthetic sheet, analysis of load transfers transmitted to the edges of the cavity, etc.The numerical model developed within the framework of this thesis work constitutes a major element for the analysis of experimental phenomena and mechanisms. Indeed, the validation of the numerical model has made it possible to systematically extend its use to different geometries, different forms of surface loading and different reinforcement materials. Finally, this work leads to some practical proposals for the dimensioning of geosynthetics by an analytical method in the context of cohesive backfill.
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https://tel.archives-ouvertes.fr/tel-03191338
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Submitted on : Wednesday, April 7, 2021 - 9:23:52 AM
Last modification on : Thursday, April 8, 2021 - 3:35:14 AM

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  • HAL Id : tel-03191338, version 1

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Maria Delli Carpini. Analyse des mécanismes d'effondrement des couches de sol cohésives renforcées par géosynthétique sur cavité. Mécanique des matériaux [physics.class-ph]. Université Grenoble Alpes [2020-..], 2021. Français. ⟨NNT : 2021GRALI002⟩. ⟨tel-03191338⟩

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