The hydraulic-mechanical behaviour of swelling clay is examined in this thesis. The study includes laboratory testing and numerical modeling which considers the influence of boundary conditions on the hydraulic-mechanical behaviour of a compacted unsaturated swelling clay soil. The laboratory testing component of this research consists of three (3) series of tests using a newly modified triaxial apparatus on which mechanical and hydraulic boundary conditions are altered during liquid infiltration. Mechanical boundary conditions range from constant volume to constant mean stress and also include constant stiffness which is a spring type boundary consisting of both volume expansion and mean stress increase. Hydraulic boundary conditions include drained and undrained flow into triaxial specimens. The numerical modeling component of this research includes the creation of a new capillary tube model for swelling clay materials and incorporates dynamic changes to the cross-sectional area for flow. Laboratory results are modeled using the capillary tube model, an empirical hydraulic model, D’Arcy’s Law, and in an elastic-plastic context for unsaturated soil. Results of the laboratory and numerical modeling components show that boundary conditions dominate the hydraulic-mechanical behaviour of unsaturated swelling clay soil during liquid infiltration. In particular, a mechanism is shown to explain how hydraulic conductivity of a swelling soil can decrease with increasing water content at constant void ratio. Finally hydraulic and mechanical behaviour cannot be considered separately in swelling materials due to the intimate relationship in their response.

Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, 2007. / Submitted in fulfilment of requirements for the degree of Doctor of Philosophy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Includes bibliographical references (p. 174-202).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

L’isolation des cuves des méthaniers, utilisant la technologie de membrane MarkIII, est garantie par l’agencement de barrières thermiques réalisées à l’aide de blocs de mousse polyuréthane renforcée. La membrane est dimensionnée pour résister aux diverses sollicitations mécaniques et thermiques de service. De plus, dans le cadre de l’étude de scénarios de sécurité critiques, il doit être démontré que l’occurrence d’un évènement rare de type pénétration d’eau, n’engendre pas de dommages sévères des composants de la membrane.L’objet de ce travail est d’étudier le comportement de la mousse polyuréthanne renforcée par des fibres de verre en immersion afin d’aider à une meilleure compréhension des mécanismes de diffusion et de l’impact de la pénétration de l’eau sur les propriétés du matériau.La mise en place d’essais de sorption à température ambiante, suivant trois conditionnements « libre », « bloqué » et « couplé » a permis d’identifier respectivement une loi de gonflement, une loi de chargement et une loi d’endommagement.En conditionnement « libre », l’architecture cellulaire et les positionnements de fibres de verre dans les plans XY induisent un couplage hygro-mécanique anisotrope. Le gonflement de la direction Z, joue un rôle très important sur les niveaux de solubilité de l’eau.En conditionnement « bloqué », le blocage du déplacement des faces perpendiculaires à la direction Z induit une augmentation du niveau de contrainte interne en fonction de la progression du front de pénétration.En conditionnement « couplé », l’enchaînement d’un vieillissement hydrique et d’un vieillissement cryogénique engendre un endommagement, dont le degré est proportionnel au niveau de gonflement de la structure cellulaire.L’impact de ces différents conditionnements sur la durabilité des propriétés mécaniques du matériau a été évalué. / The insulation of containment membrane of liquid natural gas carrier using the MarkIII membrane system, consists of load-bearing system made of panels in glass fiber reinforced polyurethane foam. The membrane is designed to resist to mechanical and thermal service load cases. As stated by IGC code regulation, and more specifically in some critical safety scenario, it has to be demonstrated that the cargo containment system will keep its integrity and main functions when subjected to water leakage through the inner hull wall (ballast).The challenge of this study is to appreciate the behavior of the reinforced polyurethane foam in immersion, which could widen the understanding of both water diffusion mechanisms and the impact of water penetration on the properties of the material.The setting up of water sorption tests at ambient temperature, according to three conditioning "free", "blocked" and "coupled" has allowed to identify a swelling law, a loading law and a damage law.In "free" conditioning, the cellular structure and the orientation of glass fibers in XY planes induce an anisotropic hygro-mechanical coupling. The swelling of Z direction has an important impact on the water solubility levels.In "blocked" conditioning, the blocking of the displacement of the faces perpendicular to the Z direction induces an increase in the internal stress levels as a function of the progression of the penetration front. In "coupled" conditioning, the sequence of the water aging and the cryogenic aging causes several damages. The damage degree is proportional to the hygroscopic swelling level of the cellular structure.The impact of these different conditionings on the durability of the material mechanical properties has been evaluated.

The research of this dissertation is formulated in two fields, i.e., the theoretical and computational studies of circumferential wrinkling on soft nanofibers and the swelling mechanics study of a bi-layered spherical hydrogel containing a hard core. Continuous polymer nanofibers have been massively produced by means of the low-cost, top-down electrospinning technique. As a unique surface instability phenomenon, surface wrinkling in circumferential direction is commonly observed on soft nanofibers in electrospinning. In this study, a theoretical continuum mechanics model is developed to explore the mechanisms of circumferential wrinkling on soft nanofibers under uniaxial stretching. The model is able to examine the effects of elastic properties, surface energy, and fiber radius on the critical axial stretch to trigger circumferential wrinkling and to discover the threshold fiber radius to initiate spontaneous wrinkling. In addition, nonlinear finite element method (FEM) is further adopted to predict the critical mismatch strain to evoke circumferential wrinkling in core-shell polymer nanofibers containing a hard core, as a powerful computational tool to simulate controllable wrinkling on soft nanofibers via co-electrospinning polymer nanofibers incorporated with nanoparticles as the core. The studies provide rational understanding of surface wrinkling in polymer nanofibers and technical approaches to actively tune surface morphologies of polymer nanofibers for particular applications, e.g. high-grade filtration, oil-water separation, polymer nanocomposites, wound dressing, tissue scaffolding, drug delivery, and renewable energy harvesting, conversion, and storage, etc. Furthermore, hydrogels are made of cross-linked polymer chains that can swell significantly when imbibing water and exhibit inhomogeneous deformation, stress, and, water concentration fields when the swelling is constrained. In this study, a continuum mechanics field theory is adopted to study the swelling behavior of a bi-layered spherical hydrogel containing a hard core. The problem is reduced into a two-point boundary value problem of a 2nd-order nonlinear ordinary differential equation (ODE) and solved numerically. Effects of material properties on the deformation, stress, and water concentration fields of the hydrogel are examined. The study offers a rational route to design and regulate hydrogels with tailorable swelling behavior for practical applications in drug delivery, leakage blocking, etc.

Swelling clays cause tremendous amounts of damage to infrastructure. For the effective prevention of detrimental effects of these clays, and to optimize the beneficial properties for industrial applications it is necessary to clearly understand the fundamental mechanisms of swelling of clays. In this study, we studied the effect of fluid polarity on swelling and flow properties of swelling clays using molecular modeling and experimental technique for bridging the molecular level phenomenon of these clays with microstructure change, particle breakdown and macro scale swelling and flow properties. A wide range of fluids (Dielectric Constant 110 to 2.4) were used, those are also commonly present in landfill leachates. We were able to tie the properties of swelling clays at different length scales. Then, we simulated the solvation of clay sheets, studied the effect of discrete charge distribution, contribution of edge charges on swelling clays and discussed some fundamental assumptions associated with double layer theories. / Department of Civil Engineering, North Dakota State University

This thesis presents two studies on elastic plates. In the first study, we discuss the choice of elastic energies for thin plates and shells, an unsettled issue with consequences for much recent modeling of soft matter. Through consideration of simple deformations of a thin body in the plane, we demonstrate that four bulk isotropic quadratic elastic theories have fundamentally different predictions with regard to bending behavior. At finite thickness, these qualitative effects persist near the limit of mid-surface isometry, and not all theories predict an isometric ground state. We discuss how certain kinematic measures that arose in early studies of rod mechanics lead to coherent definitions of stretching and bending, and promote the adoption of these quantities in the development of a covariant theory based on stretches rather than metrics. In the second work, the effects of in-plane swelling gradients on thin, anisotropic plates are investigated. We study systems with a separation of scales between bending energy terms. Warped equilibrium shapes are described by two parameters controlling the spatial "rolling up'' and twisting of the surface. Shapes within this two-parameter space are explored, and it is shown that shapes will either be axisymmetric or twisted depending on swelling function parameters and material anisotropy. In some axisymmetric shapes, pitchfork bifurcations to twisted solutions are observed by varying these parameters. We also show that a familiar soft mode of the catenoid to helicoid transformation of an isotropic material no longer exists with material anisotropy. / Master of Science / This thesis presents two studies on the subject of thin, elastic bodies, otherwise known as plates. Plate theory has important applications in many areas of life, ranging from the design and construction of civil structures to the mechanics of wrinkling sheets. In the first work, we discuss how different elastic plate theories have qualitatively different predictions on how a plate will behave when bent. We discuss the different physical implications of each model, and relate our findings to previous studies. Additionally, we promote the use of certain technical measures in the study of plates corresponding to the most coherent definitions of bending and stretching. In the second work, we study the effects of in-plane swelling gradients on elastic plates whose material stiffnesses vary with direction. Inspired by wood panels that warp when exposed to moisture, we model elastic plates exposed to various swelling patterns and determine the resulting warped shapes. We find that some shapes are axisymmetric, while others prefer to twist when exposed to moisture-induced swelling. By varying certain parameters of the swelling functions, or by increasing the material fiber stiffness, we also find a qualitative change in shape from an axisymmetric to a twisted surface.

The swelling and caking propensity of coals may cause operational problems such as channelling and excessive pressure build-up in combustion, gasification and specifically in fluidised-bed and fixed-bed operations. As a result, the swelling and caking characteristics of certain coals make them less suitable for use as feedstock in applications where swelling and/or caking is undesired. Therefore, various studies have focused on the manipulation of the swelling and/or caking propensity of coals, and have proven the viability of using additives to reduce the swelling and caking of powdered coal (<500 μm). However, there is still a lack of research specifically focused on large coal particle devolatilisation behaviour, particularly swelling and caking, and the reduction thereof using additives. A comprehensive study was therefore proposed to investigate the swelling and caking behaviour of large coal particles (5, 10, and 20 mm) of typical South African coals, and the influence of the selected additive (potassium carbonate) thereon. Three different South African coals were selected based on their Free Swelling Index (FSI): coal TSH is a high swelling coal (FSI 9) from the Limpopo province, GG is a medium swelling coal (FSI 5.5-6.5) from the Waterberg region, and TWD is a non-swelling coal (FSI 0) from the Highveld region. Image analysis was used to semi-quantitatively describe the transient swelling and shrinkage behaviour of large coal particles (-20+16 mm) during lowtemperature devolatilisation (700 °C, N2 atmosphere, 7 K/min). X-ray computed tomography and mercury submersion were used to quantify the degree of swelling of large particles, and were compared to conventional swelling characteristics of powdered coals. The average swelling ratios obtained for TWD, GG, and TSH were respectively 1.9, 2.1 and 2.5 from image analysis and 1.8, 2.2 and 2.5 from mercury submersion. The results showed that coal swelling measurements such as FSI, and other conventional techniques used to describe the plastic behaviour of powdered coal, can in general not be used for the prediction of large coal particle swelling. The large coal particles were impregnated for 24 hours, using an excess 5.0 M K2CO3 impregnation solution. The influence of K2CO3-addition on the swelling behaviour of different coal particle sizes was compared, and results showed that the addition of K2CO3 resulted in a reduction in swelling for powdered coal (-212 μm), as well as large coal particles (5, 10, and 20 mm). For powdered coal, the addition of 10 wt.% K2CO3 decreased the free swelling index of GG and TSH coals from 6.5 to 0 and from 9.0 to 4.5, respectively. The volumetric swelling ratios (SRV) of the 20 mm particles were reduced from 3.0 to 1.8 for the GG coal, and from 5.7 to 1.4 for TSH. In contrast to the non-swelling (FSI 0) behaviour of the TWD powders, the large particles exhibited average SRV values of 1.7, and was found not be influenced by K2CO3-impregnation. It was found that the maximum swelling coefficient, kA, was reduced from 0.025 to 0.015 oC-1 for GG, and from 0.045 to 0.027 oC-1 for TSH, as a results of impregnation. From the results it was concluded that K2CO3-impregnation reduces the extent of swelling of coals such as GG (medium-swelling) and TSH (high-swelling), which exhibit significant plastic deformation. Results obtained from the caking experiments indicated that K2CO3-impregnation influenced the physical behaviour of the GG coal particles (5, 10, and 20 mm) the most. The extent of caking of GG was largely reduced due to impregnation, while the wall thickness and porosity also decreased. The coke from the impregnated GG samples had a less fluid-like appearance compared to coke from the raw coal. Bridging neck size measurements were performed, which quantitatively showed a 25-50% decrease in the caking propensity of GG particles. Coal TWD did not exhibit any caking behaviour. The K2CO3-impregnation did not influence the surface texture or porosity of the TWD char, but increased the overall brittleness of the devolatilised samples. Both the extent of caking and porosity of TSH coke were not influenced by impregnation. However, impregnation resulted in significantly less and smaller opened pores on the surface of the devolatilised samples, and also reduced the average wall thickness of the TSH coke. The overall conclusion made from this investigation is that K2CO3 (using solution impregnation) can be used to significantly reduce the caking and swelling tendency of large coal particles which exhibits a moderate degree of fluidity, such as GG (Waterberg region). The results obtained during this investigation show the viability of using additive addition to reduce the caking and swelling tendency of large coal particles. Together with further development, this may be a suitable method for modifying the swelling and caking behaviour of specific coals for use in fixed-bed and fluidised-bed gasification operations. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

The swelling and caking propensity of coals may cause operational problems such as channelling and excessive pressure build-up in combustion, gasification and specifically in fluidised-bed and fixed-bed operations. As a result, the swelling and caking characteristics of certain coals make them less suitable for use as feedstock in applications where swelling and/or caking is undesired. Therefore, various studies have focused on the manipulation of the swelling and/or caking propensity of coals, and have proven the viability of using additives to reduce the swelling and caking of powdered coal (<500 μm). However, there is still a lack of research specifically focused on large coal particle devolatilisation behaviour, particularly swelling and caking, and the reduction thereof using additives. A comprehensive study was therefore proposed to investigate the swelling and caking behaviour of large coal particles (5, 10, and 20 mm) of typical South African coals, and the influence of the selected additive (potassium carbonate) thereon. Three different South African coals were selected based on their Free Swelling Index (FSI): coal TSH is a high swelling coal (FSI 9) from the Limpopo province, GG is a medium swelling coal (FSI 5.5-6.5) from the Waterberg region, and TWD is a non-swelling coal (FSI 0) from the Highveld region. Image analysis was used to semi-quantitatively describe the transient swelling and shrinkage behaviour of large coal particles (-20+16 mm) during lowtemperature devolatilisation (700 °C, N2 atmosphere, 7 K/min). X-ray computed tomography and mercury submersion were used to quantify the degree of swelling of large particles, and were compared to conventional swelling characteristics of powdered coals. The average swelling ratios obtained for TWD, GG, and TSH were respectively 1.9, 2.1 and 2.5 from image analysis and 1.8, 2.2 and 2.5 from mercury submersion. The results showed that coal swelling measurements such as FSI, and other conventional techniques used to describe the plastic behaviour of powdered coal, can in general not be used for the prediction of large coal particle swelling. The large coal particles were impregnated for 24 hours, using an excess 5.0 M K2CO3 impregnation solution. The influence of K2CO3-addition on the swelling behaviour of different coal particle sizes was compared, and results showed that the addition of K2CO3 resulted in a reduction in swelling for powdered coal (-212 μm), as well as large coal particles (5, 10, and 20 mm). For powdered coal, the addition of 10 wt.% K2CO3 decreased the free swelling index of GG and TSH coals from 6.5 to 0 and from 9.0 to 4.5, respectively. The volumetric swelling ratios (SRV) of the 20 mm particles were reduced from 3.0 to 1.8 for the GG coal, and from 5.7 to 1.4 for TSH. In contrast to the non-swelling (FSI 0) behaviour of the TWD powders, the large particles exhibited average SRV values of 1.7, and was found not be influenced by K2CO3-impregnation. It was found that the maximum swelling coefficient, kA, was reduced from 0.025 to 0.015 oC-1 for GG, and from 0.045 to 0.027 oC-1 for TSH, as a results of impregnation. From the results it was concluded that K2CO3-impregnation reduces the extent of swelling of coals such as GG (medium-swelling) and TSH (high-swelling), which exhibit significant plastic deformation. Results obtained from the caking experiments indicated that K2CO3-impregnation influenced the physical behaviour of the GG coal particles (5, 10, and 20 mm) the most. The extent of caking of GG was largely reduced due to impregnation, while the wall thickness and porosity also decreased. The coke from the impregnated GG samples had a less fluid-like appearance compared to coke from the raw coal. Bridging neck size measurements were performed, which quantitatively showed a 25-50% decrease in the caking propensity of GG particles. Coal TWD did not exhibit any caking behaviour. The K2CO3-impregnation did not influence the surface texture or porosity of the TWD char, but increased the overall brittleness of the devolatilised samples. Both the extent of caking and porosity of TSH coke were not influenced by impregnation. However, impregnation resulted in significantly less and smaller opened pores on the surface of the devolatilised samples, and also reduced the average wall thickness of the TSH coke. The overall conclusion made from this investigation is that K2CO3 (using solution impregnation) can be used to significantly reduce the caking and swelling tendency of large coal particles which exhibits a moderate degree of fluidity, such as GG (Waterberg region). The results obtained during this investigation show the viability of using additive addition to reduce the caking and swelling tendency of large coal particles. Together with further development, this may be a suitable method for modifying the swelling and caking behaviour of specific coals for use in fixed-bed and fluidised-bed gasification operations. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

The Incidence and Associated Geotechnical Issues of Swelling Clay in Stockholm  Viktoria Clarin &amp; Anna Clark  Previous tunnel failures have shown that inadequate reinforcement in tunnels can lead to cave-ins, whereby swelling clay is one of several factors that can result in these damages. Swelling clay minerals possess the ability to absorb water molecules and cations leading to an increase in volume. Instability in tunnels is a consequence of the mobilised swelling pressure caused by lack of room to accommodate for the change in volume. Several tunnels are projected throughout central Stockholm in the near future, whereby numerous drill cores have been logged. This bachelor thesis will therefore focus on the swelling potential and swelling pressure of clay samples selected from a drill core traversing the Söderström fault system. The samples selected for further analysis were collected from a drill core from Slussen, Stockholm, with the aim of determining the reinforcement requirements for future tunnelling projects.  Several samples from the drill core were selected for analysis, whereby free swelling test was conducted to determine the swelling potential for each sample. One sample displayed more than 100% volume increase and was further tested to determine swelling pressure. Tests were performed using an oedometer, resulting in a measured swelling pressure of approximately 155kPa. To identify the clay type several X-ray diffraction tests were performed on the sample.  Similar swelling pressures have been measured in tunnels affected by cave-ins in Norway. Due to these previous events, the swelling pressure is of imminent importance when constructing new tunnels. Based on the obtained results, an adequate reinforcement can be estimated and used as a foundation for future tunnel constructions within the area. The tests show that the Söderström fault contains swelling clay and precautions will have to be taken when tunnels are constructed. / Förekomsten och geotekniska konsekvenser av svällande lera i Stockholm  Viktoria Clarin &amp; Anna Clark Tidigare fall har visat att otillräcklig förstärkning i tunnlar kan leda till ras där svällande lera är en av ett antal faktorer som kan resultera i sådana skador. Svällande lermineral innehar egenskapen att absorbera vatten och katjoner som resulterar i en volymökning. Instabilitet i tunnelkonstruktioner är en konsekvens av det mobiliserande svälltrycket som uppstår då utrymme inte finns tillgängligt för denna volymändring. Ett antal tunnlar är planerade genom centrala Stockholm inom en nära framtid varför flertalet borrkärnor har karterats. Denna kandidatuppsats fokuserar därför på svällningspotential och svälltryck hos prov från en borrkärna som korsar Söderströmförkastningen. Proven som valts ut för vidare analys har sitt ursprung från en borrkärna tagen vid Slussen, Stockholm. Analyserna i denna studie har i syfte att möjliggöra en estimering av förstärkning vid framtida projekt som involverar tunnelkonstruktion.  Ett antal prov valdes ut för analys varpå fria svällningsförsök utfördes för att bestämma svällningspotential hos respektive prov. Ett av proven uppvisade en volymökning över 100% varför ytterligare försök utfördes för att fastställa provets svälltryck. Försöken genomfördes med hjälp av en ödometer vilket resulterade i ett svälltryck på ca 155kPa. För identifiering av leran utfördes ett antal analyser med röntgendiffraktion.  Likvärdiga svälltryck har uppmätts i tunnlar som drabbats av ras i Norge. Det är därför viktigt att ta hänsyn till detta då de nya tunnelprojekten ska påbörjas. Baserat på resultaten denna rapport redovisar kan godtycklig förstärkning estimeras och användas som grund för framtida tunnlar som byggs i området. Resultaten i denna studie visar att Söderströmsförkastningen innehåller svällande lera vilket kommer måste tas hänsyn till då tunnlar konstrueras.