In this thesis, basic concepts of populational models are studied from a theoretical point of view, especially the long term behaviours. All models are at least time dependent with additional age structure, spatial structure. The last model which is an extension of the von Foerster equation, is dependent on all o f these structures and have a long-term solution for large values of time. Modeling population is a frequent subject in modern biology. It is hard to create a model that appears as realistic as possible. First one might consider that a population size is governed by the current size of the population, along with rates of how each individual contributes (give birth), so that the population increases. and how frequent an individual dies, causing the population to decrease in size. However these sort of models can only describe the size of population in a shorter span of time.

There are numerous experiments for the exploration of the corium spreading behaviour, but comparable data have not been available up to now in the field of the long term behaviour of a corium expanded in a core catcher. The difficulty consists in the experimental simulation of the decay heat that can be neglected for the short-run course of events like relocation and spreading, which must, however, be considered during investigation of the long time behaviour. Therefore the German GRS, defined together with Battelle Ingenieurtechnik a benchmark problem in order to determine particular problems and differences of CFD codes simulating an expanded corium and from this, requirements for a reasonable measurement of experiments, that will be performed later. First the finite-volume-codes Comet 1.023, CFX 4.2 and CFX-TASCflow were used. To be able to make comparisons to a finite-element-code, now calculations are performed at the Institute of Safety Research at the Forschungszentrum Rossendorf with the code ANSYS/FLOTRAN.For the benchmark calculations of stage 1 a pure and liquid melt with internal heat sources was assumed uniformly distributed over the area of the planned core catcher of a EPR plant. Using the Standard-k-e-turbulence model and assuming an initial state of a motionless superheated melt several large convection rolls will establish within the melt pool. The temperatures at the surface do not sink to a solidification level due to the enhanced convection heat transfer. The temperature gradients at the surface are relatively flat while there are steep gradients at the ground where the no slip condition is applied. But even at the ground no solidification temperatures are observed. Although the problem in the ANSYS-calculations is handled two-dimensional and not three-dimensional like in the finite-volume-codes, there are no fundamental deviations to the results of the other codes.

There are numerous experiments for the exploration of the corium spreading behaviour, but comparable data have not been available up to now in the field of the long term behaviour of a corium expanded in a core catcher. The difficulty consists in the experimental simulation of the decay heat that can be neglected for the short-run course of events like relocation and spreading, which must, however, be considered during investigation of the long time behaviour. Therefore the German GRS, defined together with Battelle Ingenieurtechnik a benchmark problem in order to determine particular problems and differences of CFD codes simulating an expanded corium and from this, requirements for a reasonable measurement of experiments, that will be performed later. First the finite-volume-codes Comet 1.023, CFX 4.2 and CFX-TASCflow were used. To be able to make comparisons to a finite-element-code, now calculations are performed at the Institute of Safety Research at the Forschungszentrum Rossendorf with the code ANSYS/FLOTRAN.For the benchmark calculations of stage 1 a pure and liquid melt with internal heat sources was assumed uniformly distributed over the area of the planned core catcher of a EPR plant. Using the Standard-k-e-turbulence model and assuming an initial state of a motionless superheated melt several large convection rolls will establish within the melt pool. The temperatures at the surface do not sink to a solidification level due to the enhanced convection heat transfer. The temperature gradients at the surface are relatively flat while there are steep gradients at the ground where the no slip condition is applied. But even at the ground no solidification temperatures are observed. Although the problem in the ANSYS-calculations is handled two-dimensional and not three-dimensional like in the finite-volume-codes, there are no fundamental deviations to the results of the other codes.

Intresset för användning av KL-trä som byggnadsmaterial har ökat kraftigt sedan tekniken introducerades i Sverige under 1990-talet. Med ökande användning av KL-trä i konstruktioner finns behov av att undersöka hur materialet beter sig under längre tid. Förband är generellt sett en svag punkt i en konstruktion, och det är därför viktigt att närmare undersöka långtidsbeteendet hos förband i KL-trä. Syftet med arbetet är att utveckla metoder som kan användas för att ge större insikt i hur effekterna av belastning under lång tid påverkar konstruktioner i KL-trä. I den här studien undersöks vilka tidigare utförda studier som behandlat långtidsbeteende hos trä i allmänhet och hos KL-trä i synnerhet. Utifrån dessa studier har två förslag på testmetoder tagits fram: ett test för förband utsatt i skjuvning, och ett utdragstest. / The interest for the use of CLT as a building material has increased dramatically since the technology was first introduced in Sweden during the 1990s. With increasing use of CLT in constructions there is a need to investigate the material’s long-term behaviour. Connections are generally a weak point in a construction, and it is therefore important to investigate the long-term behaviour of connections in CLT. The purpose of this project is to develop methods that can be used to provide greater insight into how the effects of long-term loading affect the behaviour of CLT designs. This study examines previously conducted studies involving long-term behaviour of wood in general and CLT in particular. Following this investigation, two proposals of test set-ups have been developed: one test for joints subjected to loading in shear, and one withdrawal test.

This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentontie, mixtures of MX80/crushed claystone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the framework of the Barcelona Expansive Model (BExM). By comparing the model with the experimental results, the performance and limitation of the model were analyzed

The assessment of ageing tunnels requires a deeper understanding of the long-term behaviour of twin tunnels, whilst lack of permeability data limits the accuracy of long-term predictions. This thesis therefore investigates long-term twin-tunnel behaviour through finite-element parametric analyses, and provides additional pereability data through laboratory studies. Permeability tests are performed on fissured London Clay, exploring the effect of isotropic stress cycles on the permeability of fissures. A model explaining the permeability-stress relationship is proposed to explain irrecoverable changes observed in fissure permeability, and is formulated mathematically for numerical implementation. Laboratory investigations are performed on grout from the London Underground tunnels, investigating permeability, porosity, microstructure and composition. A deterioration process is proposed to explain observations, consisting of acid attack and leaching. The deterioration had appeared to transform the grout from impermeable to permeable relative to the soil. The change in grout permeability with time would strongly influence long-term movements. The long-term behaviour of single tunnels is investigated in a finite-element parametric study. A new method is formulated to predict long-term horizontal and vertical surface displacements after excavation of a single tunnel, and incorporates an improved measure of relative soil-lining permeability. The study also predicts significant surface movements during the consolidation period, contradicting the lack of further building damage observed in the field. A further parametric study also investigates the long-term behaviour of twin tunnels. Key interaction mechanisms are identified, leading to the postulation of the long-term interaction behaviour under different tunnelling conditions. Long-term interaction is found to be complex and significant, and should be accounted for in numerical simulations.

<p>The research contained in this thesis is concerned with longterm behaviour of drilled piers socketed in weak rock. The experimental work involved testing of two steel and seven concrete model piers. The 25.4 mm (1.0 in) diameter steel piers had relatively smooth socket walls (RF = 0.033) and were socketed into pseudo-rock material. The concrete piers were 76.2 mm (3.0 in) in diameter and were socketed into weak rock (Queenston Shale). The concrete piers were of two types: conventional socketed piers with relatively smooth socket walls (RF = 0.025) and grooved piers with relatively rough socket walls (RF = 0.081 and 0.303).</p> <p>The piers were tested under two condition of load support, shaft resistance only and combined shaft resistance and end-bearing support conditions.</p> <p>In case of steel piers, electrical resistance strain gauges were mounted on the pier shaft to measure the load distribution along the shaft of the piers. For concrete piers under combined shaft resistance and end-bearing support conditions, flat jack load cells with Marsh and Budenberg pressure gauges and/or electrical pressure transducers were used to measure the load transfer at the base.</p> <p>All model piers were axially loaded in the laboratory using load frames designed and fabricated for this purpose. The axial loads were iii applied by the air cylinders and held constant throughout the period of testing using a regulated air pressure supply.</p> <p>The test results confirmed that performance of socketed piers can be significantly improved by increasing the roughness of the pier-rock interface. Both the primary creep rate and the load transfer with time were larger for piers with small shaft roughness.</p> <p>A second stage of creep having a much lower creep rate was observed for all model tests. The time to the end of primary creep was found to depend on the roughness of the socket wall. The primary and secondary creep rate appeared to be dependent on the stress level, shaft roughness, compressive strength of weak rock and support conditions.</p> <p>The results of the model tests are compared with available test data and with values predicted using methods based on viscoelastic analysis. This method of analysis for piles in clay soils has been modified for application to socket piers in weak rock. It is suggested that the modifications can be used to estimate the long-term settlement of socket piers in weak rock</p> / Master of Engineering (ME)

Die Verbundwirkung zwischen Stahl und Beton stellt die essentielle Grundlage für die Funkti-onsweise von Stahlbetonbauteilen dar und beeinflusst deren Trag- und Verformungsverhalten maßgeblich. Darüber hinaus sind Rissabstände und Rissbreiten sowie die Mitwirkung des Betons auf Zug zwischen den Rissen vom Verbundverhalten abhängig. Für die Sicherstellung der Ge-brauchstauglichkeit und Dauerhaftigkeit von Gebäuden ist es notwendig die Rissbreiten zu begrenzen. Dies gilt insbesondere für Bauwerke der kritischen Infrastruktur, wie Zwischenlager für Brennelemente, welche häufig länger genutzt werden als ursprünglich geplant. Aufgrund des zeitabhängigen Verhaltens von Beton verändert sich die Verbundwirkung während der Nut-zungsdauer von Bauwerken, was zu einer Zunahme der Rissbreiten führt. Eine realitätsnahe Zustandsbewertung im Hinblick auf die verlängerte Beanspruchungsdauer setzt daher eine ge-naue Kenntnis des Verbundverhaltens und der Rissbreitenentwicklung unter Kurzzeit- und Langzeitbelastung voraus. Die Basis der vorliegenden Arbeit bildet eine umfassende Literaturrecherche zu bestehenden Verbundmodellen, den Einflüssen auf das Verbundverhalten und dessen experimentelle Ermitt-lung sowie die Auswirkungen einer Langzeitbelastung auf den Verbund und die Breite von Rissen. Im Rahmen der Arbeit wurde der Einfluss der Betonfestigkeit, der Verbundlänge und der Probe-körperart auf das lokale Verbundverhalten unter Kurzzeit- und Langzeitbelastung untersucht. Dazu wurden insgesamt 132 Verbundversuche an Auszieh- und Balkenendkörpern durchge-führt. Um Informationen über den örtlichen und zeitlichen Verlauf der Verbundkraftübertragung entlang der Einbettungslänge zu erlangen, wurden faseroptische Sensoren auf den Bewehrungs-stäben appliziert und damit die Stahldehnungsverteilung erfasst. Auf Grundlage der Ergebnisse von Versuchen mit einer sehr kurzen Verbundlänge wurden analytische Beschreibungen des lokalen Verbundspannungs-Schlupf-Verhaltens unter Kurzzeit-belastung in Abhängigkeit der Versagensart formuliert. Dabei nimmt der Verbundwiderstand im Falle eines Ausziehversagens nahezu linear mit der Betondruckfestigkeit und bei Auftreten von Spaltrissen in Abhängigkeit der Spaltzugfestigkeit zu. Des Weiteren nimmt die Bruchverschie-bung mit zunehmender Betonfestigkeit ab. Gegenüber dem lokalen Verbundmodell des fib MODEL CODE 2010 weisen die hergeleiteten Beziehungen ein steiferes Verbundverhalten auf. Die Vergrößerung der Verbundlänge im Versuch hatte eine Abnahme der gemittelten Verbund-spannung zur Folge. Insbesondere bei Balkenendversuchen hat die Verbundlänge einen maßgeb-lichen Einfluss auf den Entstehungszeitpunkt von Spaltrissen und damit auf den Verbundwider-stand. Anhand der gemessenen Dehnungen an unterschiedlichen Applikationsorten am Stab konnten Aussagen über die Spannungsverteilung innerhalb des Stabs und über den örtlichen Einfluss der Rippen abgeleitet werden. Die experimentell gewonnen Erkenntnisse wurden durch numerische Simulationen mit diskreter Modellierung der Rippen qualitativ bestätigt. Mithilfe der faseropti-schen Sensoren konnte nachgewiesen werden, dass die Kraftübertragung auch bei sehr kurzen Verbundlängen ungleichmäßig erfolgt und dass das Verbundverhalten eine Ortsabhängigkeit besitzt. Dies trifft im besonderen Maße auf lastnahe Verbundabschnitte zu, welche aufgrund des Ausbruchsverhaltens des Betons einen Bereich gestörten Verbunds darstellen. Auf Grundlage der ermittelten Verbundspannungsverteilungen wurde ein Ansatz zur Abminderung des Ver-bundwiderstands für diesen Bereich formuliert. In den Verbundversuchen unter Langzeitbelastung wurden deutliche Verformungszuwächse während der Belastungsdauer aufgezeichnet, welche keine Abhängigkeit von der Verbundlänge und nur einen geringen Einfluss von der Betonfestigkeit aufwiesen. Bestehende Modelle unter-schätzen den Effekt des Verbundkriechens. Der vorgeschlagene Berechnungsansatz kann mit der lokalen Verbundspannungs-Schlupf-Beziehung verknüpft und die Schlupfzunahme für eine beliebige Belastungsdauer bestimmt werden. Zur Untersuchung der Rissbreitenentwicklung unter Dauerlast wurden Dehnkörperversuche mit einem zentrisch einbetonierten Stab und unterschiedlichen Querschnittsabmessungen durchge-führt. Mithilfe faseroptischer Sensoren wurde während einer Langzeitbelastung von 1.000 h eine Rissbreitenzunahme von bis zu 20 % ermittelt. Aus den Dehnkörperversuchen ließ sich ableiten, dass die Auswirkungen des Verbundkriechens auf die Rissbreite mit zunehmendem Beweh-rungsgrad und zunehmendem Belastungsniveau abnehmen. Unter Anwendung der schrittweisen Integration der Differentialgleichung des verschieblichen Verbundes wurden vergleichende Berechnungen auf Basis bestehender Modelle zum Verbund und zum Verbundkriechen sowie den hergeleiteten lokalen Beziehungen durchgeführt. Die berechneten Schlupf- und Verbundspannungsverteilungen weisen im Vergleich mit den ver-suchstechnisch ermittelten Verläufen ein hohes Maß an Übereinstimmung auf. Größere Abwei-chungen wurden im Falle eines Spaltbruchversagens erzielt. Die in den Dehnkörperversuchen ermittelten Rissbreiten konnten anhand der hergeleiteten Beziehungen für kleine Querschnitts-abmessungen zutreffend prognostiziert werden, während mit dem Verbundmodell des fib MODEL CODE 2010 die Rissbreiten überschätzt werden. Die Berechnungsergebnisse zur Rissbreiten-zunahme infolge Verbundkriechens bestätigen die in den Versuchen gewonnen Erkenntnisse qualitativ. Abschließend erfolgt eine kompakte Zusammenfassung der wichtigsten technischen und wissen-schaftlichen Ergebnisse und gewonnen Erkenntnisse zum lokalen Verbundverhalten und dessen Einfluss auf die Rissbreitenentwicklung unter Langzeitbelastung. / The bond between steel and concrete is the essential basis for the functioning of reinforced concrete components and has a significant influence on their load-bearing and deformation behaviour. In addition, crack spacing and crack widths as well as the tension stiffening effect depend on the bond behavior. To ensure the serviceability and durability of buildings, it is necessary to limit the crack widths. This applies in particular to critical infrastructure structures, such as interim storage facilities for radioactive materials, which are often used for longer than originally planned. Due to the time-dependent behavior of concrete, the bonding effect changes during the service life of structures, which leads to an increase in crack widths. A realistic condi-tion assessment with regard to the extended load duration therefore requires precise knowledge of the bond behavior and the development of crack widths under short-term and long-term loading. The basis of the present work is a comprehensive literature research on existing bond models, the influences on the bond behavior and its experimental determination as well as the effects of long-term loading on the bond and the width of cracks. Within the scope of the work, the influence of concrete strength, bond length and specimen type on the local bond behaviour under short-term and long-term loading was investigated. A total of 132 bond tests were carried out on pull-out and beam end specimens. In order to obtain infor-mation about the local and temporal course of the bond force transmission along the embedment length, fiber optic sensors were applied to the reinforcing bars and the steel strain distribution was recorded. Based on the results of tests with a very short bond length, an analytical description of the local bond stress-slip behavior under short-term loading was formulated as a function of the failure mode. The bond resistance increases linearly with the concrete compressive strength in the case of pull-out failure and as a function of the splitting tensile strength in the event of splitting cracks. Furthermore, the fracture displacement decreases with increasing concrete strength. Compared to the local bond model of fib MODEL CODE 2010, the derived relationships show a stiffer bond behavior. Increasing the bond length in the test resulted in a decrease in the average bond stress. Particularly in beam end tests, the bond length has a significant influence on the time of formation of splitting cracks and thus on the bond resistance. On the basis of the measured strains at different application locations on the bar, it was possible to derive statements about the stress distribution within the bar and about the local influence of the ribs. The experimental findings were qualitatively confirmed by numerical simulations with discrete modeling of the ribs. With the help of the fiber optic sensors, it was possible to prove that the force transmission is uneven even with very short bond lengths and that the bond behaviour has a spatial dependency. This applies in particular to bond sections close to the load, which represent an area of disturbed bond due to the break-out behavior of the concrete. Based on the determined bond stress distributions, an approach was formulated to reduce the bond resistance for this area. In the bond tests under long-term loading, significant deformation increases were recorded during the loading period, which showed no dependence on the bond length and only a slight influence of the concrete strength. The proposed calculation approach can be linked to the local bond stress-slip relationship and the slip increase can be determined for any load duration. To investigate the development of crack widths under sustained load, tension tie tests were carried out with a bar centrally embedded in concrete and different cross-sectional dimensions. By means of fibre-optic sensors, an increase in crack width of up to 20 % was determined during a long-term load of 1,000 hours. The results of the tension tie tests showed that the ef-fects of bond creep on the crack width decrease with increasing degree of reinforcement and increasing load level. By applying the stepwise integration of the differential equation of sliding bond, comparative calculations were carried out on the basis of existing models for the bond and bond creep as well as the derived local relationships. The calculated slip and bond stress distributions show a high degree of agreement in comparison with the experimentally determined curves. Larger deviations were achieved in the case of a splitting failure. The crack widths determined in the tension tie tests could be accurately predicted for small cross-section dimensions using the de-rived relationships, while the bond model of fib MODEL CODE 2010 results in an overestimation of the crack width. The calculated results for the increase in crack widths due to bond creep qualitatively confirm the findings obtained in the tests. Finally, a compact summary of the most important technical and scientific results and findings on the local bond behavior and the influence on crack width development under long-term loading is provided.

La majorité des bâtiments existant aujourd'hui ne respectent pas les réglementations thermiques actuelles. Pour répondre aux exigences environnementales il est impossible, dans ce contexte, d'envisager une politique globale de démolition-reconstruction. Des campagnes de réhabilitation doivent être mises en place. Une solution innovante de réhabilitation énergétique est proposée permettant d'exploiter les ressources énergétiques urbaines, peu utilisées actuellement. Elle consiste à rajouter autour du bâtiment une enveloppe extérieure qui aurait pour fonction principale le captage d'énergie solaire. Un outil d'optimisation de la géométrie de l'enveloppe et de la distribution spatiale de panneaux capteurs à sa surface est développé. Sa validation est effectuée sur des cas simples, puis il est appliqué aux situations présentant de forts contrastes : optimisation pendant la période d'hiver ou d'été, à Oslo ou à Tunis, avec des obstacles proches masquant le Soleil. Afin de réaliser les formes complexes obtenues, il est proposé d'utiliser les gridshells comme système constructif. Ces structures obtenues par déformation élastique d'une grille de poutres en matériau composite initialement planes posent la question de la durabilité de ces matériaux soumis au chargement permanent. Pour étudier le comportement à long terme (fluage et rupture différée) de ces matériaux composés de fibres de renfort et matrice polymère viscoélastique, un modèle micro-mécanique est développé. Ce modèle de type shear-lag permet d'étudier l'influence des propriétés mécaniques des constituants sur la durée de vie du composite soumis à un chargement en traction et traction-cisaillement combinés / The majority of existing buildings does not follow present energy efficiency regulations. In order to fulfill environmental requirements it seems impossible, in this context, to consider a global demolition-reconstruction policy. Renovation programmes need to be implemented. An innovative energy efficiency improvement solution is proposed, enabling to explore urbain energy ressources presently underexploited. The concept is to add, around the building, an external envelope whose main function would be to collect energy. An optimization tool aiming at finding the optimal geometry and collectors' spatial distribution on the envelope's surface, is developed. Its validation is carried out on simple cases, it is then applied in situations showing strong contrasts: optimization during summer and winter, in Oslo and in Tunis, with close obstacles partially masking the Sun. In order to build the emerging complex geometries, the use of gridshell structures is proposed. These structures are obtained through elastic deformation of an initially plane grid made of composite material slender beams. This raises the problem of composite materials durability under sustained loading. In order to study the long-term behavior (creep and creep rupture) of these materials composed of reinforcing fibres and a polymeric viscoelastic matrix, a micromechanical model is developed. This shear-lag type model allows studying the influence of the constituents' mechanical properties on the lifespan of the composite under permanent pure traction or combined shear and traction loadings

La présente étude concerne le comportement hydromécanique des matériaux compactés à base de bentonite pour le stockage des déchets radioactifs en grande profondeur. Trois matériaux candidats ont été étudiés : la bentonite (MX80) pure, le mélange bentonite/argilite broyée et le mélange bentonite/sable. Une étude expérimentale sur la pression de gonflement du mélange bentonite/argilite a été premièrement réalisée. Cette étude a mis en évidence l'effet de la salinité de l'eau, de la procédure et la durée d'hydratation, du pré-existant vide technologique et des méthodes expérimentales. Une importante relation entre la pression de gonflement et la densité sèche finale de la bentonite a été élaborée. Ensuite, des essais de rétention d'eau, des essais d'hydratation et des essais oedométriques à succion contrôlée ont été réalisés sur des échantillons à différentes porosités tout en considérant la présence du vide technologique. En introduisant les paramètres comme indice des vides de la bentonite et le ratio volume d'eau, une analyse globale des effets des vides sur la réponse hydromécanique de la barrière ouvragée a été effectuée. Pour obtenir un meilleur aperçu de l'évolution de l'étanchéité dans le cas de vide technologique, l'effet de densité sèche finale (densité après fermeture de vide technologique) et du temps d'hydratation sur la microstructure a été, de même, étudié. La perméabilité de ce matériau à l'état non saturé a été ensuite étudiée en réalisant des essais de rétention d'eau et d'infiltration ainsi que par des observations de la microstructure. Les résultats obtenus ont permis de relier la variation de la conductivité hydraulique non saturée aux changements de la microstructure. Une expérimentation en modèle réduit reproduisant à une échelle 1/10ème les essais in-situ (SEALEX) a été effectuée, et cela pour étudier la reprise des vides à long terme d'un mélange compacté bentonite/sable, tout en considérant la présence d'un vide technologique. Les résultats ont été utilisés pour interpréter les observations de l'essai in situ. A une échelle de temps réduite, cette étude fournit des informations utiles pour estimer la durée et l'efficacité de la conception en place. Finalement, les données expérimentales obtenues dans le laboratoire sur le mélange bentonite/sable ont été interprétées dans le cadre du modèle de Barcelone (BExM). Après comparaison des résultats expérimentaux avec le modèle, les performances et les limitations du modèle ont été analysées / This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentontie, mixtures of MX80/crushed claystone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the framework of the Barcelona Expansive Model (BExM). By comparing the model with the experimental results, the performance and limitation of the model were analyzed