Ref HAL: hal-03544804_v1
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In the context of long-term degradation of porous media, the coupling between fracture mechanics and reactive transport is investigated. To capture the effect of the discontinuities into the reactive transport kinetic and the expansion induced by solid precipitation, a reactive transport model has been developed into the IRSN numerical platform XPER. The fracture is studied through micromechanical modeling based on a multibody concept and Frictional Cohesive Zone Model (FCZM). Each mesh of a finite element modeling is considered as an independent body and the overall behavior is obtained by the coupling of a volume behavior and a surface behavior respectively inside and between the finite elements. The volume behavior takes into account the poromechanics and the geochemical behavior of a porous medium without any damage. The surface behavior describes the fracture mechanics and the species transport across and along the discontinuities. The first application is dedicated to chemical attack in a pre-cracked concrete where the crack path has been computed by the mechanical solver . The second application focuses on the expansion of concrete induced by strong solid precipitation.

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Ref HAL: hal-03324034_v1
DOI: 10.1016/j.powtec.2021.07.036
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This paper is devoted to the investigation of the density sorting of grains using water jigging. Experiments achieved in a laboratory scale water jig for two initial binary bed configurations are studied and compared to numerical results. The vertical composition of the deposit is estimated after different number of water pulses to represent the sorting evolution in time. Simulations are based on a multiscale model in which the fluid is solved at a larger scale than the grain diameter using the finite element method, while the grains are considered as rigid bodies and solved using the nonsmooth contact dynamics. Key parameters are numerically varied and observed to determine the sensitivity of the process.

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Ref HAL: hal-03269431_v1
DOI: 10.1007/s10596-021-10058-x
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In the context of long-term degradation of porous media, the coupling between fracture mechanics and reactive transport is investigated. A reactive transport model in a cracked discontinuous and heterogeneous porous medium is proposed. The species transport through and along the crack network are taken into account in a multibody approach. A dedicated geochemistry solver is developed and allows to take into account a significant number of chemical reactions. The model is validated via a benchmark for a porous medium without discontinuity. The applications deal with two kinds of chemical attacks in a pre-cracked concrete sample and highlight the impact of the discontinuities in the reactive transport kinetic and on the localization of the chemical degradation. The results bring out that a unidirectional descriptor, such as the depth of ingress rate, is not sufficient to describe the material degradation correctly.

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Ref HAL: hal-03269423_v1
DOI: 10.1007/s40571-021-00418-w
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The drag exerted on an object moving in a granular medium is subject to many studies: in dry grains, it depends on the stress – often due to gravity – inside the grains. For Froude numbers less than 10, the drag is independent of the velocity. In immersed grains, it is proportional to the apparent weight of the grains and it depends on both velocity and fluid viscosity. In this paper, the drag on a cylinder in dry and immersed granular flow is simulated with a multi-scale FEM-DEM model. The Janssen stress saturation effect before the flow and velocity independence of the drag are both reproduced. The semi-circular orientation of the stress field supports the hypothesis of a spherical zone of influence of the cylinder. This orientation does not significantly change upon flowing. The results show the velocity independence of the drag is due to particle friction. In the immersed case, the fluid contribution is negligible on its own. A dimensional analysis suggests that shear thickening should be taken into account. The transition between the quasi-static and the fluidized regime is accompanied by a decrease of the stress field downstream of the cylinder and a change in the shape of the shear zone.

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Ref HAL: hal-03186643_v1
DOI: 10.26168/ajce.38.1.52
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Une approche par éléments finis cohésifs-volumétriques, tenant compte des propriétés mécaniques de la zone de transition interfaciale (ITZ), est utilisée pour étudier le comportement mécanique du béton lors d'un essai de compression uniaxiale. Dans ce travail, un modèle géométrique bidimensionnel à l'échelle mésoscopique du béton numérique a été considéré. Les échantillons obtenus sont maillés à l'aide du logiciel GMSH avec une méthode de Delaunay.Les résultats des simulations à l’aide du Modèle de Zones Cohésives Frottantes (MZCF) permettent, à travers une étude de criblage de type Hadamard, d’apporter des éléments de réponses concernant les facteurs les plus influents et leur contribution à la résistance maximale du béton en compression uniaxiale.

Commentaires: Issu de : RUGC20 Rencontres Universitaires de Génie Civil de l'AUGC, du mardi 22 mai au vendredi 25 septembre 2020, Université Cadi Ayyad de Marrakech.

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Ref HAL: hal-03185129_v1
DOI: 10.1016/j.icarus.2021.114441
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Over the last decades, simulations by discrete elements methods (DEM) have proven to be a reliable analysis tool in various domains of science and engineering. By providing access to the local physical mechanisms, DEM allows the exploration of microscopic based phenomena related to particles properties and interactions in various conditions and to revisit constitutive equations consequently. The growing computer power and memory now allow us to handle large collections of grains of various shapes and sizes by DEM simulations and in particular, it offers new perspectives in the exploration of the behavior of asteroids seen as self-gravitating and cohesive granular aggregates. In this paper we describe the Contact Dynamics (CD) method, a class of DEM based on non-smooth mechanics, and its implementation in the open-source software LMGC90. In contrast to more classical approach, Hard-and Soft-Sphere DEM, the CD method is based on an implicit time integration of the equations of motion and on a non-regularized formulation of mutual exclusion between particles. This numerical strategy is particularly relevant to the study of dense granular assemblies (even of large size) because it does not introduce numerical artefacts due to contact stiffness. So that it can be used for Small Body research, we implement a parallelised kd-tree and monitor the performance of the code as it simulates a number of granular systems. We provide examples of the simulation of the accretion of self-gravitating aggregates as well as their rotational disruption. We use the routines at our disposal in the code to monitor their behaviour through the entire evolution and find agreement with previous research.

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Ref HAL: hal-02996011_v1
DOI: 10.1007/s00226-020-01197-y
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For in situ timber structures applications, heat and mass transfer are strongly dependent on temperature. This work focuses on a parametrical modeling to evaluate and quantify temperature effect at each stage. The model is classically based on a coupling between Fourier's Law, which establishes the temporal and spatial distribution of temperature, and Fick's Law dealing specifically with the water field distribution. Several hypotheses are proposed and discussed in this work as regards thermal coupling. In particular, it is shown how to integrate temperature into a permeability correction. Also proposed herein is an interaction between temperature and the sorption isotherm. The model incorporates partial adsorption and desorption isotherms. Implementation in a finite element software allows highlighting the various couplings, in comparison with more standard calculus approaches.

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