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Identificiation in-situ des sols liquéfiables par pénétromètre statique cyclique : modélisations physiques et numériques

Abstract : The identification of liquefiable soils and the behaviour of soils in response to cyclic stresses are important challenges in geotechnical engineering. Various laboratory and in-situ tests are used to evaluate this phenomenon. The Equaterre group, in particular, is developing a static penetrometer with a cyclic tip that allows a cyclic variation of the force to be imposed on the tip by means of sliding central rods and the resulting deformations to be measured. This provides direct access to the response of the soil in place, and potentially highlights a tendency towards liquefaction or cyclic mobility. This thesis has two main parts: physical modeling in a calibration chamber and numerical modeling.Physical modelling consists in carrying out feasibility tests of the method developed by Equaterre in a calibration chamber in the 3SR Grenoble laboratory. The tests in the calibration chamber were carried out on Fontainebleau sand, with two states of medium density and loose. CPTU tests and Equaterre cyclic penetrometer were performed in both situations. The results showed the good potential of this method to identify the risk of liquefaction.Numerical modelling is based on a coupling between the discrete element method (DEM) for the solid phase and a finite volume method defined at pore scale (PFV method) for internal flow. The geometry of revolution is used to reduce the modelled domain to a quarter of the problem, and a gradation of particle sizes according to the distance to the tip is also implemented to reduce the total number of particles (and therefore the computation times) while maintaining a fine discretization in the immediate vicinity of the tip. Two types of materials, dense and loose, are simulated and for each one the mechanical response is analyzed for the dry case and for the saturated case, under monotonous and cyclic loading. The analysis of the responses in terms of force and interstitial pressure shows a good qualitative agreement with the results in the calibration chamber.Keywords: Static cyclic penetrometer; Calibration chamber; Soil liquefaction; Discrete element method (DEM); Pore-scale finite volume method (PFV).
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Hamid Hosseini Sadr Abadi. Identificiation in-situ des sols liquéfiables par pénétromètre statique cyclique : modélisations physiques et numériques. Géologie appliquée. Université Grenoble Alpes, 2019. Français. ⟨NNT : 2019GREAI078⟩. ⟨tel-02475607⟩

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