WorldCat Identities

Djeran-Maigre, Irini

Overview
Works: 34 works in 55 publications in 3 languages and 61 library holdings
Genres: Academic theses 
Roles: Thesis advisor, Opponent, Other, Author, Contributor
Publication Timeline
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Most widely held works by Irini Djeran-Maigre
Étude des diffusions thermique et hydraulique dans une argile soumise à un champ de température by I Djeran( Book )

6 editions published between 1993 and 2006 in French and German and held by 5 WorldCat member libraries worldwide

Etudes du comportement hydromécanique, chimique et de la durabilité des géomatériaux d'étanchéité mélangés avec des polymères = tudy of long term chemohydromechnic behaviour of hydraulic barrier reinforced by polymer by Andry Rico Razakamanantsoa( Book )

4 editions published between 2009 and 2011 in French and held by 3 WorldCat member libraries worldwide

Les barrières de sécurité passives reconstituées, des installations de stockage de déchets, sont conçues à l'aide de géomatériau bentonitique, elles peuvent prendre la forme d'un géosynthétique bentonitique (GSB), ou d'un sol traité. Ce travail présente les études expérimentales relatives aux comportements hydromécaniques et chimiques à long terme des géomatériaux d'étanchéité renforcés par ajout de polymère. Les essais sont conduits sur deux polymères polyélectrolytes P1 et P2, un sol ainsi qu'une bentonite choisie parmi six. Les fluides d'essais sont : NaCl2, CaCl2 et du lixiviat synthétique (LS). Le début de l'étude concerne le choix de la bentonite (B) ainsi que la concentration en polymères donnant les meilleures performances de gonflement (2%). La compatibilité chimique, entre le mélange de bentonite/polymère et le LS est testée sur un GSB reconstitué, à l'aide d'un filtre presse modifié et d'un oedoperméamètre. Les résultats ont confirmé, l'effet immédiat de l'agressivité du fluide sur la bentonite seule. Ils montrent également l'effet floculant du polymère P1, matérialisé par le gonflement et l'effet dispersant du polymère P2, constaté par l'amélioration des performances hydrauliques des mélanges. L'étude de la durabilité hydraulique est réalisée avec des perméamètres à parois rigides sur un sol traité et renforcé. Les résultats montrent que la préhydratation retarde les effets négatifs du LS sans les atténuer. De plus, l'ajout de polymère permet à long terme d'améliorer la capacité de rétention en eau, mais également de rétenir les polluants dans le temps. Des indicateurs de durabilité chimique ont été proposés pour prévenir la dégradation des géomatériaux
ADDITIONAL CHAPTERS OF HIGHER MATHEMATICS by Irini Djeran-Maigre( )

2 editions published in 2016 in English and held by 3 WorldCat member libraries worldwide

Velocities, dispersion, and energy of SH-waves in anisotropic laminated plates by Irini Djeran-Maigre( )

1 edition published in 2014 in English and held by 2 WorldCat member libraries worldwide

Etude du comportement couplé thermo-hydro-mécanique et chimique (THMC) des argiles profondes = Study of the coupled THMC behaviour of deep argillaceaous rocks by Adrien Haxaire( Book )

2 editions published in 2008 in French and held by 2 WorldCat member libraries worldwide

The storage of nuclear wastes in the Bure clay makes interact four types of phenomena: thermal, hydric, mechanical and chemical. Existing THMC models consider chemical reactions indirectly, through a parameter containing the whole information about the reaction. Thus, it was necessary to build a complete model, which would allow to consider every phenomenon, and which could take their couplings into account. This work is made of three parts. The theoretical part constitues an important part of the work. The whole thermodynamical framework has been redefined to take into account chemical reactions. They are represented by the reaction rate, the gate to chemical thermodynamics, the only way to describe them accurately. The model is implemented in Castem 2000. Hydric and chemical procedures have been integrated in the code. The couplings between the phenomena is done at end of time step. The third part is the confrontation of the model to experimental data found in the literature. This work offers many prospects. Firstly, other oefficients have to be determined. The model has to be upgarded by integrating the non linear parts of the phenomena. The numerical code may be optimised by developping a new procedure that computes which resolves the four phenomena for every iteration, in order to produce strong couplings
Caractérisation des sédiments fins des retenues hydroélectriques en vue d'une orientation vers des filières de valorisation matière by Baptiste Anger( Book )

2 editions published in 2014 in French and held by 2 WorldCat member libraries worldwide

Sediment dredging is needed to ensure good operation of ports, waterways and reservoirs insofar as navigation or energy production is concerned. The analysis of feedback from experiments concerning beneficial uses of fine sediments dredged from marine and river environments, shows that sustainable solutions are very limited or do not exist. Land-based management of hydro-electric dams with sediments requires the integration of all resources existing in a given area. A sustainable approach to management of dredged material requires, inter alia, a change of point of view. Even if their status is that of waste, these materials deserve to be considered as a valuable potential alternative resource, bearing in mind the scarcity of natural mineral material. Therefore, this thesis proposes a global approach, adapted to dam fine sediments, to implement a decision-making tool in order to pre-screen sediments towards re-use channels. A study of five potential industrial sectors for reusing fine dam sediments was conducted, including cement works, concrete admixtures, road building, ceramics, and agriculture. It highlighted input specifications of fine dam sediments, and research on key parameters. An inventory was established for each of these industrial sectors, quoting related research works and applied engineering. These five sectors or channels were implemented and investigated in laboratory conditions using four hydroelectric dam fine sediments, representative of various typologies. First, a mineral, geotechnical and agronomic characterization was conducted, allowing to weigh sediments - industrial sectors or channels, considering input specifications of re-use objectives. Then, re-use tests followed, namely, manufacturing of a clinker, addition of sediments to a mortar, development of road material and manufacturing of a ceramic material, highlighting positive or negative characteristics of fine sediments in relation to various channels studied. A decision tool was implemented for preselecting re-use channels. It was designed from the identification and interpretation of pertinent technical criteria, and from minimal characterization of fine dam sediments. Finally, it is stressed that geographical proximity for possible re-use is of paramount importance
Grain breakage under uniaxial compression using a three-dimensional discrete element method by François Nader( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Numerical analyses of segmental tunnel lining under static and dynamic loads by Ngoc Anh Do( )

2 editions published in 2014 in English and held by 2 WorldCat member libraries worldwide

This PhD thesis has the aim to study the behaviour of segmental tunnel lining by developing a new numerical approach to the Hyperstatic Reaction Method (HRM) and producing two-dimensional (2D) and three-dimensional (3D) numerical models using the finite difference method (FDM). The study first deals with under static loads, and then performs under dynamic loads. Firstly, a literature review has been conducted. A new numerical approach applied to the HRM has then been developed. At the same time, a 2D numerical model is programmed regarding static loading conditions in order to evaluate the influence of the segmental joints, in terms of both joint distribution and joint stiffness characteristics, on the tunnel lining behaviour. After that, full 3D models of a single tunnel, twin horizontal tunnels and twin tunnels stacked over each other, excavated in close proximity in which the joint pattern is simulated, have been developed. These 3D models allow one to investigate the behaviour of not only the tunnel lining but also the displacement of the ground surrounding the tunnel during the tunnel excavation. A simplified 3D numerical model has then been produced in order to validate the new numerical approach applied to the HRM. In the last part of the manuscript, the performance of the segmental tunnel lining exposed to dynamic loading is taken into consideration through quasi-static and full dynamic analyses using 2D numerical models (FDM). A new HRM model has also been developed considering quasi-static loads. The differences of the tunnel behaviour under static and seismic loadings are highlighted
Déshydratation naturelle et mécanisée de sédiments : étude des processus mis en jeu et applications by Beatriz Boullosa Allariz( )

2 editions published in 2018 in French and held by 2 WorldCat member libraries worldwide

Les opérations de dragage génèrent d'importants volumes de sédiments à teneur en eau élevée qui sont difficilement transportables. Toute opération de valorisation ou stockage des sédiments implique de réduire la teneur en eau. Le séchage naturel et la déshydratation mécanisée des sédiments répondent à cette attente. Le séchage naturel des sédiments est la technique de déshydratation la plus économique et la meilleure du point de vue environnemental. Le temps de séchage peut être réduit par des moyens techniques adaptés (retournement, scarification) mis en action par l'application de critères d'aptitude au séchage naturel. Pour ce faire, le processus de séchage naturel a été reproduit à l'échelle du laboratoire à l'aide d'essais d'Égouttage et de Séchage et d'essais de Séchage et de Retrait couplés à des essais scissométriques. Ils ont porté sur neuf sédiments : sept sédiments de barrage, deux sédiments marins et une kaolinite. Une relation Su=f(IP) a été établie. Cette relation permet d'obtenir la cohésion non drainée Su à partir d'une mesure de teneur en eau. Elle permet aussi de définir ou cerner le moment le plus propice au retournement des sédiments à l'aide d'engins spécifiques sur site. Une autre méthode mécanique pour réduire le temps de séchage est suggérée. Il s'agit de pratiquer une scarification des sédiments à l'aide d'outils mobiles, voire robotisés, comme un rouleau scarificateur ou d'une rangée d'outils transportés par un treillis mobile adapté. En ce qui concerne la déshydratation mécanisée des sédiments, une nouvelle méthode de déshydratation en continu a été proposée à partir d'une presse à boues KDS®. Pour des raisons de conception et d'application, la presse à boues KDS® n'a jamais été utilisée pour déshydrater des sédiments. Un plan expérimental a été développé. Il est démontré que la presse KDS® est capable de déshydrater un sédiment fin sableux sans une maintenance démesurée. Des adaptations de la presse KDS® à la déshydratation de sédiments et des améliorations sont finalement proposées
Variation over time of excavated soil properties treated with surfactants by Irini Djeran-Maigre( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

Etude de la continuité des états liquides et solides pour les géomatériaux traités constituants les barrières d'étanchéité hydraulique = Study of Liquid and Solid States Continuum for treated Geo material Used as Landfill Liners by Gilles Barast( Book )

2 editions published in 2010 in French and held by 2 WorldCat member libraries worldwide

To comply with waste containment liners regulatory requirements, bentonite (moisture-reactive clay) based hydraulic sealing systems may be required, possibly enhanced using innovative polymer reinforcement. Due to the low hydraulic conductivity, the testing lime for characterisation in the laboratory is long, which makes it difficult for rapid engineering design. Pioneering investigations, as weil as new quick hydraulic indexes, are called for. Accordingly, experimental studies were undertaken on the geomaterials in their higher hydraulic conductivity liquid state, based on rheology and filtration. Liquid state rheological parameters were experimentally transposed into solid state soli mechanics parameters (specifically hydraulic conductivity). This methodology was based on test results for various bentonites, fluids (including water and CaCI2) two polymers and sand, for compacted sand-bentonite-polymer mixtures. Observations from HMC investigations, from the literature, and from rheology and .filtration testing, showed compatibility for bentonite polymer-fluid mixtures over a range of states. Dynamic rheology testing was found to provide the most appropriate parameters to formulate a hydraulic performance index. Two approaches were adopted (gel and swelling), linking the hydraulic conductivity with rheological parameters. Linear correlations were observed, dependent on the fluid chemistry and polymer addition, manifesting the mixing affect and the significance of a liquid-solid continuum
Traitement électrocinétique des sédiments de dragage multi-contaminés et évolution de leur toxicité / encadrante Céline Boulangé-Lecomte by Yue Tian( )

2 editions published in 2017 in French and held by 2 WorldCat member libraries worldwide

This thesis research is mainly devoted to the optimization of an electrokinetic (EK) remediation process as a promising technology for treating multi-contaminated (trace metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyles (PCBs)) dredged harbor sediments of low permeability. This study is also investigating the effect of the EK treatment on the evolution of sediment toxicity. After a bibliographic review, asecond part of this study was dedicated to the analytical methods carried out for the characterization of the sediment and its contaminants, particularly to their extraction from the sediment matrix; thus a new extraction method, through matrix solid phase dispersion (MSPD) was developed, for a fast and simultaneous extraction of both PAHs and PCBs, and a sample purification.MSPD appeared more efficient than the microwave assisted extraction (MAE) method. Thereafter many EK experiments (at different scales) were described in a third part. EK remediation tests were performed using a spiked model sediment or natural harbor dredged sediments. Many combinations of surfactants and chelators were tested as EK enhancing agents for decreasing simultaneously metal (Cd, Cr, Cu, Pb, Zn) and PAH/PCB levels. Their choice was done because of their possible low toxicity with a view to use them for future site restoration: (bio)surfactants (rhamnolipids, saponin and Tween 20) combined with chelators (citric acid (CA) and EDDS). The results showed that metals (except Cr) were difficult to remove from this kind of dredged sediment owing to its reductive character, to its high buffering capacity, to its very low hydraulic permeability and to its high organic matter content. However PAHs and PCBs showed better removal levels (29.2% and 50.2%, respectively). In a fourth part, the efficiency of the EK process was also assessed by measuring the evolution of the acute toxicity of the treated sediment on E. affinis copepods exposed to sediment elutriates. The results showed that using CA, biosurfactants or Tween 20 as enhancing agents did not significantly impact the toxicity of the treated sediment. However, E. affinis copepods were significantly sensitive to low pH values and oxidative conditions, to Cu, and to a lesser extent to Pb amounts, if they were transformed in more mobile and bioavailable forms. In contrast, acute toxicity was only slightly and even negatively correlated to PAH and PCB amounts after EK treatment, probably due to the production of oxidized metabolites of PAHs and PCBs, more toxic than the parent compounds
Couches absorbantes pour la propagation d'ondes dans les sols non bornés à l'aide de la décomposition en sous-domaines et l'intégration temporelle hybride asynchrone by Sijia Li( )

2 editions published in 2019 in French and held by 2 WorldCat member libraries worldwide

The purpose of this thesis is to propose novel designs and formulations of different absorbing layers at the boundaries of finite element meshes for the numerical simulation of wave propagation in unbounded 2D and 3D media, in order to deal with complex soil-structure interaction problems in transient dynamics. Three absorbing layers are developed: Rayleigh Absorbing Layer, Kosloff Absorbing Layer and Perfectly Matched Layer (PML). By studying analytically the strong form of elastic wave propagation in each medium, the frequency-independent absorbing ability of Kosloff damping and PML is derived, whereas the attenuation due to Rayleigh damping turns out be frequency-dependent. The interface problem between a non-dissipative elastic medium and a dissipative medium has been investigated by considering the wave propagation in the continuous setting, in order to establish optimal conditions to further reduce the spurious waves reflected at the interface. The three absorbing layers are discretized in space by the finite element method, while the time discretization is based on the powerful and flexible HATI framework (Heterogeneous Asynchronous Time Integrator), enabling adopt the most suitable time integration schemes and time steps, depending on the characteristics and physical phenomena occurring in the different subdomains. The efficiency of three asynchronous hybrid absorbing layers for modeling unbounded domains has been illustrated in various 2D and 3D numerical applications, such as Lamb's test in stratified heterogeneous media or soil-structure interaction problems involving wave barriers. Finally, implicit and explicit versions of asynchronous PML are implemented and tested in problems with a large number of degrees of freedom. It is proved to be more accurate and efficient than the absorbing layers based on Rayleigh and Kosloff damping
Effect of micro and macro parameters in 3D modeling of grain crushing by François Nader( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

The role of the microstructure in granular material instability by Nho Gia Hien Nguyen( Book )

2 editions published between 2016 and 2019 in English and held by 2 WorldCat member libraries worldwide

Les matériaux granulaires se composent de grains solides et d'un constituant remplissant les pores, tel qu'un fluide ou une matrice solide. Les grains interagissent au travers de répulsions élastiques, auxquelles s'ajoutent des mécanismes de friction, d'adhérence et d'autres forces surfaciques. La sollicitation externe conduit à la déformation des grains ainsi qu'à des réarrangements de particules. Les déformations des milieux granulaires sont d'une importance capitale dans de nombreuses applications industrielles et dans la recherche, comme par exemple dans la métallurgie des poutres ou en mécanique des sols. La réponse des matériaux granulaires sous chargement externe est complexe, en particulier lorsqu'une rupture se produit: le mode de rupture peut être diffus ou localisé, et l'aspect de peut varier drastiquement lorsque celui-ci ne peut plus soutenir la charge externe. Dans le cadre de cette thèse, une analyse numérique basée sur une méthode des éléments discrets est réalisée pour étudier les comportements macroscopique et microscopique des matériaux granulaires à la rupture. Ces simulations numériques prennent en compte le critère du travail du second ordre afin de prédire la rupture. De plus il est montré que l'annulation du travail du second ordre coïncide avec la transition d'un régime statique vers un régime dynamique. Ensuite, le comportement matériaux granulaires est analysé à l'échelle micro-structurelle. L'évolution des chaines des forces et des cycles des grains est étudiée durant le processus de déformation jusqu'à la rupture. Le travail du second ordre est également pris en compte pour examiner l'aspect local qui régit la rupture à l'échelle locale. L'effondrement de l'échantillon discret quand il passe du régime quasi-statique vers le régime dynamique est accompagné d'une bouffée d'énergie cinétique. Cette augmentation de l'énergie cinétique est générée lorsque la contrainte interne ne permet pas d'équilibrer la force externe sous l'action d'une petite perturbation, ce qui entraîne une différence entre les travaux du second ordre interne et externe du système. Les mésostructures démontrent une relation symbiotique entre elles, et leur évolution gouverne le comportement macroscopique du système discret. La distribution de l'effondrement des chaînes de forces est parfaitement corrélée avec l'annulation du travail du second ordre à l'échelle de particules. Les mésostructures jouent un rôle important dans l'instabilité des milieux granulaires. Le travail du second ordre peut être utilisé comme un critère pertinent et robuste pour détecter l'instabilité du système que ce soit à l'échelle macroscopique ou microscopique (échelle de particule)
Modélisation double-échelle de la rupture des roches : influence du frottement sur les micro-fissures by Aleksandra Wrzesniak( )

1 edition published in 2012 in English and held by 2 WorldCat member libraries worldwide

In continuum damage models, the degradation of the elastic moduli, as the results of microscopic crackgrowth, is represented through damage variables. The evolution of damage variable is generally postulatedbased on the results of the experimental observations. Many such phenomenological damage modelshave been proposed in the literature. The purpose of this contribution is to develop a new procedurein order to obtain macroscopic damage evolution laws, in which the damage evolution is completelydeduced from micro-structural analysis. We use homogenization based on two-scale asymptotic developmentsto describe the overall behaviour starting from explicit description of elementary volumes withmicro-cracks. We consider quasi-brittle (time independent) and sub-critical (time dependent) criteria formicro-cracks propagation. Additionally, frictional contact is assumed on the crack faces. An appropriatemicro-mechanical energy analysis is proposed, leading to a damage evolution law that incorporates stiffnessdegradation, material softening, size effect, and unilaterality, different fracture behaviour in contactwithout and with friction. The information about micro-cracks is contained in the homogenized coefficientsand in the damage evolution law. The homogenized coefficients describe the overall response inthe presence of (possibly static) micro-cracks, as they are computed with the (quasi-) static microscopicsolution. The damage law contains the information about the evolution of micro-cracks, as a result ofthe energy balance in time during the microscopic propagation. The homogenized law is obtained in therate form. Effective coefficients are numerically computed for different crack lengths and orientations.This allows for the complete construction of the macroscopic laws. A first analysis concerns the localmacroscopic behaviour, for complex loading paths, in order to understand the behaviour predicted bythe two-scale model and the influence of micro structural parameters, like for example friction coefficient.Next, the FEM implementation of the macroscopic equations is performed and simulations for variouscompression tests are conducted. The results of the numerical simulations are compared with the experimentalresults obtained using a new true-triaxial apparatus recently developed at the Laboratory 3SRin Grenoble (France)
Contribution à l'étude de mélange en pellets composé d'argilite COx et de bentonite MX80 pour le remplissage des stockages géologiques by Danai Panagiota Tyri( )

2 editions published in 2021 in French and held by 2 WorldCat member libraries worldwide

The safe operation of the geological disposal facilities for radioactive waste indicates the galleries progressive closure, by installing sealing and backfill materials. The French disposal concept examines the crushed excavated Callovo-Oxfordian (COx) claystone with bentonite additive (MX80) as backfill material. One of the ongoing studied backfill solutions considers the pelletized implementation of the mixture, due to potential set-up advantages. The pelletized mixture is emplaced inside the galleries at dry state, presenting initially a granular structure, gradually homogenised, due to swelling upon hydration from the groundwater of the surrounding rock. Objective of the PhD thesis is the determination and manufacturing of the pelletized mixture, as well as the analysis of its hydro-mechanical behaviour. The pelletized granulometry is selected to result in the highest possible packing density, defining the optimum grain size distribution (GSD). The implemented COx/MX80 backfill needs to present hydro-mechanical properties capable of limiting the voids after the saturation on the drift as well as blocking the concrete movement when liners cracking will occur in the long-term. Numerical and experimental gravitational deposits are conducted, to study the compactness of a granular material, without mechanical compaction. Simulations using the Discrete Element Method (DEM) investigate the granulometric effect on the granular material's packing state, determining an optimum GSD. Supplementary experiments are used to evaluate and finalise the granulometric selection maximising the resulting density. Both studies investigate the effect of additional parameters (implementation protocol, inter-particle friction, deposit height,...) on the packing state. The pelletization of the selected GSD is performed for the first time on COx/MX80 powdered mixtures, by applying the compression method on a reconditioned tablet machine. The process is analysed to successfully fabricate pellets and optimise the challenging pellet production. COx/MX80 mixtures hydro-mechanical behaviour is experimentally investigated by performing infiltration tests under free and confined volume conditions. A parametric study on various powdered mixtures is conducted to characterise the materials physicochemical properties and evaluate their swelling capacity at densities expected on the backfill implementation. On the other hand, the finalised pellets assembly on various compositions is directly tested in terms of swelling pressure and hydraulic conductivity
Problèmes géotechniques couplés en hydromécanique : application à l'érosion interne par suffusion by Hashem Abdou( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

The phenomenon of Suffusion corresponds to the migration of fine eroded particles in a porous medium under the action of an internal water flow. This mechanism could be the main origin of damage in embankments and earth dams. Many experimental studies have been done to analyse the suffusion but actually understanding this phenomenon appears as a major scientific challenge. On the other hand, numerically, only a few studies were found which associate the mechanisms of detachment, transport and deposition of eroded particles.Based on the Darcy's law model, the erosion model of Papamichos et al (2001) modified by Bendahmane (2005) and the fluid viscosity evolution law (Einstein relation), we developed a new hydro-mechanical approach of suffusion. The numerical solution of the problem is carried out by using a finite element method. Two aspects are presented: first, the general framework of the proposed model (implemented in 2D) with a parametric study and then the validation of the numerical model realized with a 3D study of the geometric model of the experimental study of Cross Erosion Test (CET). This model describes the three phenomena of suffusion: erosion, transport and deposition of eroded particles in a saturated soil.Furthermore, the numerical modeling of coupled phenomena of internal erosion is performed using the commercial software "Comsol Multiphysics-3.4b". However, to validate the model, experimental results on two types of soil: sandy gravel soil (S3) and the silt of Isère (S4 and S4-a) are used. These results are found in the PhD thesis of Nguyen(2013) who has developed a new apparatus called Cross Erosion Test (CET).Moreover, to discuss the transient and dynamic aspects of the phenomenon, the evaluation of the mass conservation with different figures of flow velocity, hydraulic gradient, hydraulic head, porosity and permeability distribution, concentration distribution, and of outgoing eroded particles, are measured over time and compared with experimental results
Numerical study on vibration isolation by wave barrier and protection of existing tunnel under explosions by Bo Qiu( )

2 editions published in 2014 in English and held by 2 WorldCat member libraries worldwide

Ground vibration induced by human activity such as industrial activities, car or truck traffic, or pilling and blasting in construction or deconstruction operation, generally reaches the troublesome limit for men and occasionally attains the harmful limit. In the densely populated urban regions and buildings housing sensitive equipments, ground vibration has to be strictly controlled. Up to now, many vibration reduction methods have been proposed, one of which is the installation of wave barrier between the dynamic sources and the protected structures. Over the past decades, the vibration isolation effectiveness of wave barrier has been extensively studied. However, to the best of the writer's knowledge, there is little study about the mutual influence of the parameters of soil-barrier system on the barrier screening efficiency, and the optimization design for wave barrier is rare as well. On the other hand, the influence of ground vibration generated by explosions on the nearby existing tunnel has attracted more and more attention due to the recent damage or even failure of tunnels. Up to now, there are few mitigation measures comprehensively proposed by researchers and engineers for the tunnel vibration reduction during explosions. To overcome those drawbacks, this dissertation focuses on the investigation of the influence of various parameters of soil-barrier system on the barrier isolation efficiency. Key parameters are identified. More importantly, an optimization design method is developed, aiming to find out the desirable barrier that is able to minimize the ground vibration in protected site. Besides, the dynamic behavior of existing tunnel under nearby explosions is examined. Parameters that significantly affect the response of tunnel are pointed out. Furthermore, two practical mitigation measures: the installation of a protective layer along the tunnel lining and time-delayed explosions (rather than instantaneous explosions), are presented with details. The research in this dissertation is able to provide a good reference for the optimization design of wave barrier in reducing ground vibration in protected site and for the design of practical mitigation measures to protect existing tunnel from nearby explosions
Couches absorbantes hybrides multi-pas de temps en dynamique des sols by Eliass Zafati( )

2 editions published between 2015 and 2020 in French and held by 2 WorldCat member libraries worldwide

This thesis which deals with the study of absorbing layers for soil dynamics problems, is divided into three essential parts. The first part aims to propose a design method of absorbing layers by the Rayleigh damping to simulate wave propagation problems in infinite media. This method is based on a mathematical analysis of the wave propagation problem in a media characterized by a Rayleigh damping matrix, which allows us, firstly, to establish conditions for minimizing spurious waves at the interfaces, and another hand, to provide a simple design relationship for the absorbing domain based on the notion of the logarithmic decrement. The second part aims to apply the multi-time step strategy for wave propagation problems in 1D and 2D infinite media. The proposed approach is to integrate the physical domain by an explicit scheme and the absorbing domain by an implicit scheme and to evaluate the potential of this method by varying the time step ratio between subdomains. Special attention is given to the 1D case for which the effect of the mesh fineness, defined by the number of finite elements per wavelength, is also analyzed. Furthermore, the evolution of computing time depending on the time ratio is studied in order to estimate the gains made with respect to a reference computation achieved by a full explicit integration. The last part is dedicated to the study of the Perfectly Matched Layer (PML) as part of hybrid couplings multi-time step. This section is introduced by a stability study of temporal scheme for 1D cases. The absorbing layer PML is integrated by an implicit scheme with a time step larger than that of the domain of interest. Although this coupling methodology is very effective for the reproduction of infinite media, parametric studies show a sensitivity to the time ratio greater than that exhibited by the Rayleigh damping layers
 
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ADDITIONAL CHAPTERS OF HIGHER MATHEMATICS
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Irini Djeran-Maigre wetenschapper

Languages
French (26)

English (13)

German (1)