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In the French deep geological disposal for radioactive wastes, compacted bentonite/claystone mixtures have been considered as possible sealing materials. After emplacement in place, such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete. In this study, the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites (MX80 Na-bentonite and Sardinia Ca-bentonite) were investigated by carrying out a series of swelling pressure, hydraulic conductivity and mercury intrusion porosimetry (MIP) tests. It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution, the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges. For the Sardinia bentonite/claystone mixture, the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions, suggesting insignificant cation exchanges. Additionally, the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures. The large-pore volume increased consequently and enhanced water flow. In the cement solution, the hydroxide could also dissolve the montmorillonite, reducing the swelling pressure, and increase the large-pore volume, facilitating the water flow. Furthermore, the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

Swelling soil leads to many types of constructional damages, deformations, and failures in the constructions’ roads, shoulders, and foundations. Depending on the amount of swell, they can be insignificant, moderate, or massive. This paper presents a method for swelling soil stabilization by adding rice husk powder (RHP) in variable percentages of 0, 5, 10, 15, 20, and 25 by weight of dry soil. The properties of swelling soil stabilization were investigated by various lab tests such as consistency limits (plastic limit, liquid limit, and plasticity index), swelling potential, swelling pressure, free swelling, and free swell index. The swelling soil was also mineralogically examined using X‐ray diffraction of clay mineralogy. This stabilization reduced the plasticity from 56% (extremely high plasticity) to 4.5% (low plasticity). Swelling potential (S) and swelling pressure (SP) decreased by 48% to 45.5, 44.7, and 34.6%, from 1003 kN/m2 to 800, 653, and 489 kN/m2 for the partial replacement of the soil by 5%, 10%, and 15% RHP, respectively. The results show that the present approach is very efficient for improving the swelling soil properties and that the optimal amount of added RHP of the swelling soil is 15%. It will also be a database aimed at reducing construction risks in the future. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

In the French deep geological disposal for radioactive wastes, compacted bentonite/claystone mixtures have been considered as possible sealing materials. After emplacement in place, such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete. In this study, the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites (MX80 Na-bentonite and Sardinia Ca-bentonite) were investigated by carrying out a series of swelling pressure, hydraulic conductivity and mercury intrusion porosimetry (MIP) tests. It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution, the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges. For the Sardinia bentonite/claystone mixture, the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions, suggesting insignificant cation exchanges. Additionally, the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures. The large-pore volume increased consequently and enhanced water flow. In the cement solution, the hydroxide could also dissolve the montmorillonite, reducing the swelling pressure, and increase the large-pore volume, facilitating the water flow. Furthermore, the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

Compacted bentonite/sand mixtures are often considered as sealing/backfilling materials in deep geological disposal for radioactive waste. This study investigates the swelling pressure of compacted bentonite/sand mixtures with different bentonite fractions and dry densities upon hydration under constant-volume conditions. It was found that the swelling pressure of bentonite/sand mixtures is strongly dependent on their bentonite fraction and final montmorillonite dry density. For the samples with a bentonite fraction larger than a critical value, there is a linear relationship between the swelling pressure and final montmorillonite dry density. By contrast, for the samples with a bentonite fraction lower than the critical value, the sand particles will be skeletonized after strong compaction and lead to a heterogeneous distribution of montmorillonite, resulting in a larger swelling pressure compared to the samples with higher bentonite fractions. The maximum sand skeleton void ratio, corresponding to that at which the sand skeleton is just formed, is used to estimate the critical montmorillonite dry density and the critical bentonite fraction. Comparison between the test data and the estimated results shows good agreement, indicating the relevance of the identified swelling mechanism for compacted bentonite/sand mixtures.

The reactive transport framework ORCHESTRA was used to implement a dual porosity reactive transport system that accounts for mechanical processes relevant for confined swelling clays at full saturation. The new implementations are based on water retention data generated by molecular dynamics simulations, and on fundamental mechanical formulations. The code predicts and fully couples porewater chemistry, exchanger population, diffusive transport, mineral reactions, volume fractions of the free and Donnan porosity domains, and swelling pressure. The chemomechanical predictions were compared with experimental measurements of swelling pressure and d-value of the clay in different chemical environments. A simulation of bentonite in contact with a constant concentration reservoir demonstrates the performance of the new model approach. It can be used to model interactions of bentonite with different groundwaters or cement and steel.

Compacted bentonite/sand mixtures are often considered as sealing/backfilling materials in deep geological disposal for radioactive waste. This study investigates the swelling pressure of compacted bentonite/sand mixtures with different bentonite fractions and dry densities upon hydration under constant-volume conditions. It was found that the swelling pressure of bentonite/sand mixtures is strongly dependent on their bentonite fraction and final montmorillonite dry density. For the samples with a bentonite fraction larger than a critical value, there is a linear relationship between the swelling pressure and final montmorillonite dry density. By contrast, for the samples with a bentonite fraction lower than the critical value, the sand particles will be skeletonized after strong compaction and lead to a heterogeneous distribution of montmorillonite, resulting in a larger swelling pressure compared to the samples with higher bentonite fractions. The maximum sand skeleton void ratio, corresponding to that at which the sand skeleton is just formed, is used to estimate the critical montmorillonite dry density and the critical bentonite fraction. Comparison between the test data and the estimated results shows good agreement, indicating the relevance of the identified swelling mechanism for compacted bentonite/sand mixtures.

Pre-compacted blocks of MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture are chosen as sealing/backfilling materials in the French concept of deep geological disposal for radioactive waste. Creating technological voids is normally unavoidable during installation in the disposal galleries, in the form of axial voids between compacted blocks and radial voids between the compacted blocks and the host rock. In this work, the aeolotropic swelling behaviour of compacted mixture with axial/radial technological voids was experimentally investigated. Results showed that the aeolotropy coefficient (ratio of radial to axial pressures) of samples without voids increased from 0.46 to 0.88 with the increasing dry density from 1.6 to 2.0 Mg/m3 due to the relatively concentrated macro-pores which defined a relatively lower local dry density in the side part. For the samples with axial/radial voids, their final axial swelling pressures were in agreement with the unique correlation with final dry density, regardless of the soil density heterogeneity. Samples with axial voids had a larger aeolotropy coefficient than samples without voids, due to the reduction of the orientation of clay particles upon hydration, while samples with radial voids had a smaller aeolotropy coefficient, due to the relatively lower dry density near the cell wall. © 2020 Elsevier B.V.

© 2020 Pavement structures constructed on the expansive soil subgrade experience a higher upward pressure compared to any other subgrade material. The upward pressure is caused due to high swelling and shrinkage characteristics of expansive clay soil. The present study has investigated and identified the mechanisms by which a remolded expansive soil can be modified to reduce the upward pressure and swelling (heave). To achieve this, a lightweight, environmentally friendly, and high pressure resistive expanded polystyrene (EPS) granules have been used with expansive soil s from three different locations of Madhya Pradesh state, India. The study has been performed to understand the swelling and strength characteristics of soil with and without the use of EPS (density = 21.6 kg/m3) as per ASTM specifications. The chemical and microstructural components of the expansive soil were investigated using autotuned total reflectance Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Several laboratory experiments, including optimum moisture content, maximum dry unit weight, grain-size distribution, liquid limit, plastic limit, shrinkage limit, free swell index, unconfined compressive strength, and pressure swelling tests were carried out on the statically compacted expansive clay soil specimen with and without EPS (0.25%, 0.50%, 1.00%). The maximum addition of EPS was considered as 1% as the very high expansion was observed, and beyond this, further addition of EPS was not feasible. The results show that the swelling pressure, expansion percentage, and time rate of swell decrease, whereas the unconfined compressive strength (UCS) increases with the addition of EPS. The inclusion of EPS in expansive clay soil exponentially reduced the heave and the upward pressure, whereas the maximum UCS was observed at 0.5%.

© 2020 Pavement structures constructed on the expansive soil subgrade experience a higher upward pressure compared to any other subgrade material. The upward pressure is caused due to high swelling and shrinkage characteristics of expansive clay soil. The present study has investigated and identified the mechanisms by which a remolded expansive soil can be modified to reduce the upward pressure and swelling (heave). To achieve this, a lightweight, environmentally friendly, and high pressure resistive expanded polystyrene (EPS) granules have been used with expansive soil s from three different locations of Madhya Pradesh state, India. The study has been performed to understand the swelling and strength characteristics of soil with and without the use of EPS (density = 21.6 kg/m3) as per ASTM specifications. The chemical and microstructural components of the expansive soil were investigated using autotuned total reflectance Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Several laboratory experiments, including optimum moisture content, maximum dry unit weight, grain-size distribution, liquid limit, plastic limit, shrinkage limit, free swell index, unconfined compressive strength, and pressure swelling tests were carried out on the statically compacted expansive clay soil specimen with and without EPS (0.25%, 0.50%, 1.00%). The maximum addition of EPS was considered as 1% as the very high expansion was observed, and beyond this, further addition of EPS was not feasible. The results show that the swelling pressure, expansion percentage, and time rate of swell decrease, whereas the unconfined compressive strength (UCS) increases with the addition of EPS. The inclusion of EPS in expansive clay soil exponentially reduced the heave and the upward pressure, whereas the maximum UCS was observed at 0.5%.

Pre-compacted blocks of MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture are chosen as sealing/backfilling materials in the French concept of deep geological disposal for radioactive waste. Creating technological voids is normally unavoidable during installation in the disposal galleries, in the form of axial voids between compacted blocks and radial voids between the compacted blocks and the host rock. In this work, the aeolotropic swelling behaviour of compacted mixture with axial/radial technological voids was experimentally investigated. Results showed that the aeolotropy coefficient (ratio of radial to axial pressures) of samples without voids increased from 0.46 to 0.88 with the increasing dry density from 1.6 to 2.0 Mg/m3 due to the relatively concentrated macro-pores which defined a relatively lower local dry density in the side part. For the samples with axial/radial voids, their final axial swelling pressures were in agreement with the unique correlation with final dry density, regardless of the soil density heterogeneity. Samples with axial voids had a larger aeolotropy coefficient than samples without voids, due to the reduction of the orientation of clay particles upon hydration, while samples with radial voids had a smaller aeolotropy coefficient, due to the relatively lower dry density near the cell wall. © 2020 Elsevier B.V.

Clay minerals consist of clay platelets, which are anisotropic in both size and charge, and these can form a lamellar structure depending on the size, making it a seemingly perfect model system for an electrical double layer. The situation is however, from a structural point, slightly less ideal. Clay is a challenging system since it has a polydisperse distribution of anisotropic clay platelets and it is normally not a homogeneous lamellar material, it is rather described as a disordered structure of stacks of platelets, also denoted tactoids. The stability in saline solution depends strongly on the surface charge density of the platelets, and on the counterion valency. By altering the physiochemical properties, tactoid formation can be promoted, where a transition from a repulsive to an attractive system is obtained. In addition, the overcharging effect may result in tactoidal dissolution, where the tactoids dissolve into smaller sized tactoids. The aim of this thesis has been to get a better understanding of the electrostatically driven structure formation in clay dispersions and to gain a deeper molecular knowledge of the interactions between the clay platelets, as well as the interactions of the clay platelets in the presence of other macromolecules. The research has focused on extensive studies of the tactoid formation and the tactoidal behaviour of the natural clay mineral montmorillonite and the synthetic clay mineral Laponite® by varying the valency of the counterions, the temperature, and the solvent properties, as well as with addition of multivalent salt and positively charged peptides and polyelectrolytes. It was found that it is possible to capture the behaviour of tactoid formation, tactoidal growth, and tactoidal dissolution for clay systems where the interactions are dominated by electrostatics by utilising coarse-grained molecular dynamics simulations based on the continuum model in combination with a number of different experimental techniques.

One of the most important characteristics of mudstones is their susceptibility to swelling upon absorption of water, which is influenced by climatic processes. This study investigated the swelling pressure and strain of the Yanji mudstone subjected to wetting–drying (W–D), freezing–thawing (F–T) and wetting–drying–freezing–thawing (W–D–F–T) cycles. The swelling curves were analysed using a simulation of the logistic function, and the coefficient of initial swelling (Cis), coefficient of primary swelling (Cps), coefficient of secondary swelling (Css), and ultimate swell were derived from the mathematical simulation. The results show that the cyclic treatments can significantly influence the swelling kinetics and ultimate swell. As the number of treatment cycles increases, Cis increases and then decreases due to the competition between the increasing permeability and the decreasing swelling potential induced by the propagation of cracks and large voids, while Cps and Css decrease because of the compaction and contraction of the aggregates after cyclic treatments. The ultimate swelling pressure and ultimate swelling strain decrease with increasing treatment cycles and the relationships among these parameters were also established, allowing the ultimate swelling pressure and strain of the Yanji mudstone under the full range of seasonal variation to be predicted. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been proposed as a sealing/backfilling material in a deep geological repository of radioactive waste in France. A good understanding of the swelling behaviour of this mixture is essential when evaluating the long-term performance of the repository. In this work, the swelling pressure of MX80 bentonite/COx claystone mixture was investigated by the constant-volume method for a full range of bentonite fraction. Results show that the swelling of claystone in the mixture can be inhibited by bentonite and its contribution to the global swelling pressure depends on the bentonite fraction. For the mixture with >70% bentonite, claystone behaves as an inert material, and its contribution to the global swelling pressure can be ignored. However, for the mixture with less bentonite, the swelling of claystone will significantly contribute to the global swelling pressure. A method was proposed allowing the swelling pressure of bentonite/claystone mixture to be predicted in the full range of bentonite fraction.

Articular cartilage is a complex, anisotropic, stratified tissue with remarkable resilience and mechanical properties. It has been subject to extensive modelling as a multiphase medium, with many recent studies examining the impact of increasing detail in the representation of this tissue’s fine scale structure. However, further investigation of simple models with minimal constitutive relations can nonetheless inform our understanding at the foundations of soft tissue simulation. Here, we focus on the impact of heterogeneity with regard to the volume fractions of solid and fluid within the cartilage. Once swelling pressure due to cartilage fixed charge is also present, we demonstrate that the multiphase modelling framework is substantially more complicated, and thus investigate this complexity, especially in the simple setting of a confined compression experiment. Our findings highlight the importance of locally, and thus heterogeneously, approaching pore compaction for load bearing in cartilage models, while emphasising that such effects can be represented by simple constitutive relations. In addition, simulation predictions are observed for the sensitivity of stress and displacement in the cartilage to variations in the initial state of the cartilage and thus the details of experimental protocol, once the tissue is heterogeneous. These findings are for the simplest models given only heterogeneity in volume fractions and swelling pressure, further emphasising that the complex behaviours associated with the interaction of volume fraction heterogeneity and swelling pressure are likely to persist for simulations of cartilage representations with more fine-grained structural detail of the tissue.

MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been proposed as a sealing/backfilling material in a deep geological repository of radioactive waste in France. A good understanding of the swelling behaviour of this mixture is essential when evaluating the long-term performance of the repository. In this work, the swelling pressure of MX80 bentonite/COx claystone mixture was investigated by the constant-volume method for a full range of bentonite fraction. Results show that the swelling of claystone in the mixture can be inhibited by bentonite and its contribution to the global swelling pressure depends on the bentonite fraction. For the mixture with >70% bentonite, claystone behaves as an inert material, and its contribution to the global swelling pressure can be ignored. However, for the mixture with less bentonite, the swelling of claystone will significantly contribute to the global swelling pressure. A method was proposed allowing the swelling pressure of bentonite/claystone mixture to be predicted in the full range of bentonite fraction.

One of the most important characteristics of mudstones is their susceptibility to swelling upon absorption of water, which is influenced by climatic processes. This study investigated the swelling pressure and strain of the Yanji mudstone subjected to wetting–drying (W–D), freezing–thawing (F–T) and wetting–drying–freezing–thawing (W–D–F–T) cycles. The swelling curves were analysed using a simulation of the logistic function, and the coefficient of initial swelling (Cis), coefficient of primary swelling (Cps), coefficient of secondary swelling (Css), and ultimate swell were derived from the mathematical simulation. The results show that the cyclic treatments can significantly influence the swelling kinetics and ultimate swell. As the number of treatment cycles increases, Cis increases and then decreases due to the competition between the increasing permeability and the decreasing swelling potential induced by the propagation of cracks and large voids, while Cps and Css decrease because of the compaction and contraction of the aggregates after cyclic treatments. The ultimate swelling pressure and ultimate swelling strain decrease with increasing treatment cycles and the relationships among these parameters were also established, allowing the ultimate swelling pressure and strain of the Yanji mudstone under the full range of seasonal variation to be predicted. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Clay minerals consist of anisotropic nanoplatelets where the majority of the clay minerals are highly charged, and thus, swell in aqueous solution. The structure and swelling depend on the type of clay mineral, and also on the ionic composition, and temperature. The natural clay mineral montmorillonite have been studied both theoretically and experimentally. Theoretically, coarse-grained models have been used to represent the clay platelets where Monte Carlo (MC), and molecular dynamics (MD) simulations have been utilized to study the electrostatic interactions between the platelets. Experimentally, the structure has been studied with small angle X-ray scattering (SAXS), and the swelling has been studied by swelling pressure measurements in a test cell.The research in this thesis has been focused on the tactoid formation, i.e. platelets aggregating in a face-to-face configuration with an equidistant separation, as a function of the divalent counterion charge ratio, and as an effect of the relative permittivity of the solvent. It was found that it was possible to tune the electrostatic interactions to obtain a transition from a repulsive to an attractive system when increasing the divalent counterion charge ratio or by decreasing the relative permittivity of the solvent. Moreover, the temperature response was investigated, where it was found that the electrostatic interactions alone can give a positive, negative, or constant osmotic pressure response with temperature.

Clay-mineral type and content, bulk mineralogical composition and alteration of bentonite are very important factors for the ultra-long-term stabilization of barriers and backfills in radioactive waste disposal. This study investigates the effects of clay-mineral type and content on the swelling characteristics and permeability of bentonite–sand mixtures with clay minerals using one-dimensional swelling-pressure and constant-pressure permeability tests. The hydraulic conductivity of bentonite–sand–clay mineral mixtures increased with increasing content of non-swelling alteration products of montmorillonite. Furthermore, hydraulic conductivity was comparable to that determined with the Kozeny–Carman equation for a specific surface area, suggesting that hydraulic conductivity may be estimated based on the abundance of expected alteration products of montmorillonite. This study provides a basis for evaluation of the hydraulic conductivity of bentonite–sand mixtures with known quantities of expected alteration products of montmorillonite.

El túnel de Lilla sufrió importantes deformaciones de expansión y presiones de hinchamiento desde su construcción debido a la precipitación de cristales de yeso en discontinuidades del macizo rocoso. Las expansiones afectaron gravemente el túnel y condujeron a construir una sección circular con un revestimiento de hormigón de alta resistencia altamente armado. En la tesina se analizará el comportamiento del revestimiento definitivo del túnel de Lilla.

An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) for size-asymmetric electrolytes presented in part I is applied to calculate the forces and the ion exchange for Ca- and Na-montmorillonite systems in equilibrium with salt solutions. Our modeling shows that the DFT calculations are in excellent agreement with Monte Carlo simulations and experimental results. The results indicate that the ion size plays an important role in force-distance relation. Due to the excluded volume effect, the osmotic pressure curve predicted by DFT is shifted towards larger separation distances with increasing the diameter of counterions. Additionally, the interaction can be switched from attraction to repulsion with increasing diameter of counterions from standard to hydrated ionic size. Furthermore, the quantitative characterization of the exchange of calcium for sodium at room temperature on Wyoming bentonite is investigated with the DFT modeling in aqueous solutions at pH 7.0. It is found that a significant variation of the selectivity coefficient could be observed with the surface charge density, ionic diameter and interlayer separations. This implies that ion selectivity in compacted bentonite differs from that in dilute smectite dispersions., QC 20161129

Expansive soils are common in arid and semi-arid climate regions of the world and cause severe problems on civil engineering structures. The Swelling potential of the expansive soil mainly depends upon the properties of soil and environmental factors,and stress conditions. Swelling pressure is a key parameter used in designing structures in and on expansive soil. The swelling pressure of soil is measured in the laboratory using a representative soil samples. The size and the surface friction of the sample ring used in the swelling pressure test have effects on the measured swelling pressure and they have not properly been investigated. In this study, a series of constant volume swelling tests were conducted using an automated consolidation-swell apparatus to evaluate the effect of sample ring size, ring friction, initial dry density, and initial moisture content (IMC). Test results indicate an exponential growing trend of swelling pressure when the dry density is increased. Similarly, high swell pressures are achieved when the IMC is increased for the same dry density. A higher swelling pressure was measured when the friction of the specimen ring was reduced. The measured swelling pressure increases with increasing the height of the sampling ring and it decreases when the ring diameter is increased. Therefore, it is recommended to use a standard sample ring reducing inside wall friction using lubricants when measuring the swelling pressure in the laboratory. Further, the sample ring size, initial density and initial moisture content of soil should be given when reporting swelling pressure of soil.

The Danish Tertiary Holmehus clay belongs to the series of illite-smectite mixed-layer clays in northern Europe and has a potential to serve as an effective engineered barrier for isolating hazardous waste. Mineralogical specification was made of the components illite/smectite mixed-layer and dioctahedral vermiculite/smectite mixed-layer structures. The lower content of expandable phase than of smectite- rich clays like MX-80 gives somewhat higher hydraulic conductivity and somewhat lower swelling pressure but both are deemed suitable for isolating canisters with high-level radioactive waste in deeprepositories for densities at water saturation of at least 1900 kg/m3. The lower swelling pressure, the potential of being chemically more stable, and the high buffer capacity by providing dissolved Si makes Holmehus clay a candidate for use in both deep and near-surface repositories., Validerad; 2015; Nivå 2; 20140310 (svek)

The Danish Tertiary Holmehus clay belongs to the series of illite-smectite mixed-layer clays in northern Europe and has a potential to serve as an effective engineered barrier for isolating hazardous waste. Mineralogical specification was made of the components illite/smectite mixed-layer and dioctahedral vermiculite/smectite mixed-layer structures. The lower content of expandable phase than of smectite- rich clays like MX-80 gives somewhat higher hydraulic conductivity and somewhat lower swelling pressure but both are deemed suitable for isolating canisters with high-level radioactive waste in deeprepositories for densities at water saturation of at least 1900 kg/m3. The lower swelling pressure, the potential of being chemically more stable, and the high buffer capacity by providing dissolved Si makes Holmehus clay a candidate for use in both deep and near-surface repositories., Validerad; 2015; Nivå 2; 20140310 (svek)

The Incidence and Associated Geotechnical Issues of Swelling Clay in Stockholm Viktoria Clarin & 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 & 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.

The Incidence and Associated Geotechnical Issues of Swelling Clay in Stockholm Viktoria Clarin & 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 & 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.

A mechanistic model is developed to predict the swelling pressure of fully saturated, bentonite-based materials in distilled water or dilute saline solutions over a large range of final dry densities of bentonite. It applies a thermodynamic relationship between swelling pressure and suction to describe the contribution of crystalline swelling, while using a diffuse double-layer model to explain the behavior of osmotic swelling. In addition, it accounts for the demixing of exchangeable cations and the disintegration of the montmorillonite particles into small stacks of unit layers upon water uptake.Comparison of the model predictions with a great number of experimental results of swelling pressures of different types of bentonites and bentonite-aggregate mixtures in both distilled water and saline solutions suggests that the model works excellently in the cases tested. It is found that the water chemistry, the montmorillonite content, the type and amount of exchangeable cations in the interlayers are important in determining the extent to which the montmorillonite particles are delaminated and hence the swelling behavior of saturated, bentonite-based materials.On the other hand, the applicability of the model in predicting the water retention curves of unsaturated bentonites is also tested. The results show that the predicted curves are in good agreement with the measured data and that the montmorillonite particles are more difficult to disintegrate into small pieces in the case of unsaturated bentonites than would otherwise be possible., QC 20130819

The combination of the fundamental measure theory (FMT) and the weighted correlation approach (WCA) within the framework of the density functional theory, i.e., the FMT/ WCA approach, is applied to study the swelling pressure of Nabentonite at different salt conditions. Good agreement between the FMT/WCA simulations and the results from both experiments and a Donnan-equilibrium-based DLVO model suggests that the hydration repulsion between charged surfaces can be well accounted by the ionion correlations effect., QC 20121212

The project aims at investigating how effectively the groundwater can be isolated from diesel oil that has leaked from a failed tank by covering the ground surface in a few hundred square meters large area confined by soil dikes. The scenario to be considered is a sudden outflow of oil over the ground followed by removal of the oil after a period of time taken here to be 2 weeks. The depth of the oil fill in this period is assumed to be 0.5 m, which will cause oil to penetrate and migrate into the membrane built on the ground surface. The problem to be solved is to predict to what depth the membrane will be contaminated by oil, i.e. how much of it that has to be removed and replaced after the two weeks. The ground surface is assumed to be perfectly horizontal. The project comprised oedometer testing of the artificially prepared membrane clay, which contains a small amount (11 % by weight) and which is a candidate material for isolation of the ground from oil that can leak out from failing tanks or valves. The oedometer tests were made for determining the (fluid) conductivity and swelling pressure of the membrane material for water and for diesel oil and they were complemented by column tests for simulating of the function when oil is let into air-dry membrane material, and into water saturated material, respectively. The aim was to find out if and how oil molecules move in the membrane., Validerat; 20120918 (anonymous)

Solid high level radioactive waste (HLW) and spent nuclear fuel are isolated from the environment by being stored in underground repositories. Boreholes from the ground surface into the host rock need to be sealed by installing clay/concrete plugs for preventing quick migration of possibly released radionuclides from the repository. Clay seals are installed where the rock is poor in fractures and has a low hydraulic conductivity, while concrete will be cast where the boreholes are intersected by fracture zones. The risk of unstable conditions in the early stage of their maturation should be taken into consideration. For the concrete seals, erosion before stiffening, and dissolution and loss of the cement component at later stages can weaken them. For the clay, dispersion and channeling of the early formed clay seals are the greatest risks. The thesis deals with evolution of clay seals in deep boreholes, focusing first on the determination of the rate of homogenization of clay plugs of standard type, i.e. with the clay blocks prepared by compaction of air-dry clay granules as well as granules pre-saturated to about 100 %. A second aim was to investigate the risk of piping of the clay formed between the perforated tube and the borehole walls by hydraulic gradients in the vertical direction of the borehole through flow tests for identifying critical states for piping and erosion. A third issue was to investigate the chemical interaction of clay seals and concrete cast on them in simulated boreholes.A fourth issue was to develop conceptual models for the maturation of clay seals and to make an attempt to work out theoretical physical models of the maturation process. The study demonstrated, in conclusion, that the maturation rate of the prewetted compacted clay was slower than the initially compacted air-dry sample and also that for clay gel with initial density of saturation 1050kg/m3 the critical hydraulic conductivity that causes erosion/piping is below 10 m/m (meter, Validerat; 20120613 (anonymous)

The combination of the fundamental measure theory (FMT) and the weighted correlation approach (WCA) within the framework of the density functional theory, i.e., the FMT/ WCA approach, is applied to study the swelling pressure of Nabentonite at different salt conditions. Good agreement between the FMT/WCA simulations and the results from both experiments and a Donnan-equilibrium-based DLVO model suggests that the hydration repulsion between charged surfaces can be well accounted by the ionion correlations effect.

A water-swelling material is one of the rubbery impermeable materials which mixed synthetic resin elastomers as a base material, high absorbency polymers, filler and solvents. In this study, swelling characteristics of the water-swelling material on the water polluted with COD and BOD, as an impermeable material at coastal landfill sites, are examined by laboratory swelling ratio test. Furthermore, the factor in which it influences the swelling pressure of water-swelling material is clarified by measuring the swelling pressure. As the results, the COD nor the BOD concentrations in the soaked water influence the swelling ratio of the water-swelling material. When the thicknesses of water-swelling material are 2 mm and 3 mm, the maximum swelling pressure of 0.5 MPa or more that corresponds to hydraulic pressure by depth of 50 m is possessed.

The collagen fibril network is an important factor for the depth-dependent mechanical behaviour of adult articular cartilage (AC). Recent studies show that collagen orientation is parallel to the articular surface throughout the tissue depth in perinatal animals, and that the collagen orientations transform to a depth-dependent arcade-like structure in adult animals. Current understanding on the mechanobiology of postnatal AC development is incomplete. In the current paper, we investigate the contribution of collagen fibril orientation changes to the depth-dependent mechanical properties of AC. We use a composition-based finite element model to simulate in a 1-D confined compression geometry the effects of ten different collagen orientation patterns that were measured in developing sheep. In initial postnatal life, AC is mostly subject to growth and we observe only small changes in depth-dependent mechanical behaviour. Functional adaptation of depth-dependent mechanical behaviour of AC takes place in the second half of life before puberty. Changes in fibril orientation alone increase cartilage stiffness during development through the modulation of swelling strains and osmotic pressures. Changes in stiffness are most pronounced for small stresses and for cartilage adjacent to the bone. We hypothesize that postnatal changes in collagen fibril orientation induce mechanical effects that in turn promote these changes. We further hypothesize that a part of the depth-dependent postnatal increase in collagen content in literature is initiated by the depth-dependent postnatal increase in fibril strain due to collagen fibril reorientation

Complex landslides in clay-bearing sediments are investigated in two moderate-relief regions of Southeast Spain. Both regions, more than 100 km apart show landslides affecting the same Flysch formation, which outcrops widely in the central and western Betic Cordillera along the contact between the External (South Iberian Domain) and Internal (Alborán Domain) zones. Intense rainfall episodes can be considered as the main triggering factor for slope failures in these two areas. We have chosen two landslides (Diezma and Riogordo landslides), one from each area of study, to investigate their morphological and geotechnical features in order to establish the relative importance of the different controlling factors. From a kinematic point of view, the two features studied in detail can be referred as to rotational failures, evolving downhill to slow earthflows. The movement was concentrated on several surfaces developed on a clay-rich layer mostly constituted by smectite. This clay mineral is of critical relevance to the mechanical behaviour of soils and Flysch-like formations, being very consistent at dry conditions, but rapidly losing its strength at wet conditions. Thus, softened smectite-rich clay layers with high water contents can approach the properties of a lubricant, which, in turn, can be critical for slope stability. In addition to their high plasticity, these clays have a high swelling potential, which can induce significant vertical overpressure, thus reducing even more the strength properties of the Flysch formation. In Southeast Spain, a region with a Mediterranean rainfall regime, slope stability can be seriously influenced by the presence of these smectite-rich clay layers in a formation of regional extent, as is the case of the Flysch formation. Therefore, this lithologically-controlled factor should be taken into account when evaluating landslide hazard in the Betic Cordillera., Consejería de Obras Públicas de la Junta de Andalucía, Spanish Ministry of Science and Innovation, TOPO-IBERIA CONSOLIDER-INGENIO, Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

Complex landslides in clay-bearing sediments are investigated in two moderate-relief regions of Southeast Spain. Both regions, more than 100 km apart show landslides affecting the same Flysch formation, which outcrops widely in the central and western Betic Cordillera along the contact between the External (South Iberian Domain) and Internal (Alborán Domain) zones. Intense rainfall episodes can be considered as the main triggering factor for slope failures in these two areas. We have chosen two landslides (Diezma and Riogordo landslides), one from each area of study, to investigate their morphological and geotechnical features in order to establish the relative importance of the different controlling factors. From a kinematic point of view, the two features studied in detail can be referred as to rotational failures, evolving downhill to slow earthflows. The movement was concentrated on several surfaces developed on a clay-rich layer mostly constituted by smectite. This clay mineral is of critical relevance to the mechanical behaviour of soils and Flysch-like formations, being very consistent at dry conditions, but rapidly losing its strength at wet conditions. Thus, softened smectite-rich clay layers with high water contents can approach the properties of a lubricant, which, in turn, can be critical for slope stability. In addition to their high plasticity, these clays have a high swelling potential, which can induce significant vertical overpressure, thus reducing even more the strength properties of the Flysch formation. In Southeast Spain, a region with a Mediterranean rainfall regime, slope stability can be seriously influenced by the presence of these smectite-rich clay layers in a formation of regional extent, as is the case of the Flysch formation. Therefore, this lithologically-controlled factor should be taken into account when evaluating landslide hazard in the Betic Cordillera.

The mechanical behavior of the entire anulus fibrosus is determined essentially by the tensile properties of its lamellae, their fiber orientations, and the regional variation of these quantities. Corresponding data are rare in the literature. The paper deals with an in vitro study of single lamellar anulus lamellae and aims to determine (i) their tensile response and regional variation, and (ii) the orientation of lamellar collagen fibers and their regional variation. Fresh human body-discbody units (L1-L2, n=11) from cadavers were cut midsagittally producing two hemidisc units. One hemidisc was used for the preparation of single lamellar anulus specimens for tensile testing, while the other one was used for the investigation of the lamellar fiber orientation. Single lamellar anulus specimens with adjacent bone fragments were isolated from four anatomical regions: superficial and deep lamellae (3.9 +/- 0.21 mm, mean SD, apart from the outer boundary surface of the anulus fibrosus) at ventro-lateral and dorsal positions. The specimens underwent cyclic uniaxial tensile tests at three different strain rates in 0.15 mol/l NaCl solution at 37 degrees C, whereby the lamellar fiber direction was aligned with the load axis. For the characterization of the tensile behavior three moduli were calculated: E-low (0-0.1 MPa), E-medium (0.1-0.5 MPa) and E-high (0.5-1 MPa). Additionally, specimens were tested withthe load axis transverse to the fiber direction. From the second hemidise fiber angles with respect to the horizontal plane were determined photogrammetrically from images taken at six circumferential positions from ventral to dorsal and at three depth levels. Tensile moduli along the fiber direction were in the range of 28-78 MPa (regional mean values). Superficial lamellae have larger E-medium (p=0.017) and E-high (p=0.012) than internal lamellae, and the mean value of superficial lamellae is about three times higher than that of deep lamellae. Tensile moduli of ventro, QC 20100525

Tiwari, N., Satyam, N., & Shukla, S. K. (2020). An experimental study on micro-structural and geotechnical characteristics of expansive clay mixed with EPS granules. Soils and Foundations, 60(3), 705 - 713). https://doi.org/10.1016/j.sandf.2020.03.012

Tahasildar, J., Rao, B. H., & Shukla, S. K. (2017). Mineralogical Compositions of Some Indian Expansive Soils and Their Influence on Swelling Properties. International Journal of Geosynthetics and Ground Engineering, 3(1), 5. Available here.

Die Arbeit beschäftigt sich mit der Bestimmung der Zwangsbeanspruchungen und mit den daraus resultierenden Verformungen auf geotechnische Bauwerke infolge Quellen von teilgesättigten, bindigen Böden. Zur Ermittlung eines Quellgesetzes zur Beschreibung dieses Volumenänderungsverhaltens wurden zwei spezielle Oedometergeräte entwickelt. Mittels eines modifizierten Oedometers können radiale und axiale Quelldrücke getrennt voneinander gemessen sowie axiale Dehnungen zugelassen werden. Die axialen Spannungen werden über eine Kraftmessdose ermittelt während die radialen über Dehnungsmessstreifen, die an der Außenfläche des Oedometerringes befestigt sind, bestimmt werden. Mit Hilfe dieser Dehnungsmessstreifen wird die Radialverformung des Ringes gemessen. Daraus wird die Ringkraft und somit der Radialdruck, der auf der Probe wirkt, ermittelt. Ein anderes Oedometergerät, welches bis auf den Oedometerring baugleich zu dem bereits erwähnten ist, wurde speziell für die vorliegende Problematik entwickelt. In der Innenseite des Oedometerringes ist eine Membran angebracht, über die kontrolliert Radialdrücke erzeugt und gemessen werden können. Der Raum zwischen dem Ring und der Membran ist mit einem Fluid gefüllt. Durch Regulierung des im Reservoir befindlichen Fluidvolumens kann die Radialdehnung gesteuert werden. Somit ist dieses modifizierte Oedometergerät mit einem triaxialen Apparat vergleichbar. Es wurden umfangreiche Untersuchungen in den o. g. Geräten an einem quellfähigen Boden durchgeführt. Dabei wurden der Anfangs- und der Endsättigungsgrad sowie die Porenzahl variiert. Aus den Versuchen ergab sich, dass das Quellverhalten als nichtlinear elastisch angesehen werden kann. Anhand dieser Ergebnisse sind Approximationen für das eindimensionale sowie das dreidimensionale Quellverhalten aufgestellt und in den FEM - Code ABAQUS mittels einer Subroutine implementiert worden. In der numerischen Simulation werden die elastischen Quelldeformationen mit den mechanischen Deformatione, This thesis deals with the determination of the constraints and the resulting deformations on geotechnical structures caused by swelling of unsaturated cohesive soils. To determine the swelling relationship that describes this volume change behaviour two oedometer devices have been developed. By means of a modified oedometer apparatus it is possible to measure the swelling pressure both in the radial and the axial direction. The axial pressure is measured by a load cell while the radial pressure is obtained via strain gauges mounted on the outer surface of the oedometer ring. By means of these strain gauges the radial deformation of the ring is measured, from which the radial force and the radial pressure exerted on the sample is determined. Another oedometer apparatus, that is similar to the one mentioned before, has been developed especially for the present study. The oedometer ring is fitted inside with a membrane through which radial pressure is exerted under controlled conditions. The space between the ring and the membrane is filled with a fluid. The adjustment of the fluid volume in the reservoir allows the control of the radial strain. Thus, this oedometer device is comparable to a triaxial apparatus. Detailed investigations have been carried out using this equipment on soils with swelling potential. The initial and the final degree of saturation as well as the void ratio have been varied. From the results it has been identified that the swelling behaviour may be regarded as nonlinear elastic. Based on these experimental results approximate expressions have been derived for the one-dimensional and the three-dimensional swelling behaviour. They have been subsequently implemented in the FEM code ABAQUS via a subroutine interface. In the numerical simulation the elastic swelling deformations are superimposed to the mechanical deformations due to external loads and self-weight. For the mechanical deformations a linear elastic – ideal plastic stress-strain relati

Die Arbeit beschäftigt sich mit der Bestimmung der Zwangsbeanspruchungen und mit den daraus resultierenden Verformungen auf geotechnische Bauwerke infolge Quellen von teilgesättigten, bindigen Böden. Zur Ermittlung eines Quellgesetzes zur Beschreibung dieses Volumenänderungsverhaltens wurden zwei spezielle Oedometergeräte entwickelt. Mittels eines modifizierten Oedometers können radiale und axiale Quelldrücke getrennt voneinander gemessen sowie axiale Dehnungen zugelassen werden. Die axialen Spannungen werden über eine Kraftmessdose ermittelt während die radialen über Dehnungsmessstreifen, die an der Außenfläche des Oedometerringes befestigt sind, bestimmt werden. Mit Hilfe dieser Dehnungsmessstreifen wird die Radialverformung des Ringes gemessen. Daraus wird die Ringkraft und somit der Radialdruck, der auf der Probe wirkt, ermittelt. Ein anderes Oedometergerät, welches bis auf den Oedometerring baugleich zu dem bereits erwähnten ist, wurde speziell für die vorliegende Problematik entwickelt. In der Innenseite des Oedometerringes ist eine Membran angebracht, über die kontrolliert Radialdrücke erzeugt und gemessen werden können. Der Raum zwischen dem Ring und der Membran ist mit einem Fluid gefüllt. Durch Regulierung des im Reservoir befindlichen Fluidvolumens kann die Radialdehnung gesteuert werden. Somit ist dieses modifizierte Oedometergerät mit einem triaxialen Apparat vergleichbar. Es wurden umfangreiche Untersuchungen in den o. g. Geräten an einem quellfähigen Boden durchgeführt. Dabei wurden der Anfangs- und der Endsättigungsgrad sowie die Porenzahl variiert. Aus den Versuchen ergab sich, dass das Quellverhalten als nichtlinear elastisch angesehen werden kann. Anhand dieser Ergebnisse sind Approximationen für das eindimensionale sowie das dreidimensionale Quellverhalten aufgestellt und in den FEM - Code ABAQUS mittels einer Subroutine implementiert worden. In der numerischen Simulation werden die elastischen Quelldeformationen mit den mechanischen Deformatione, This thesis deals with the determination of the constraints and the resulting deformations on geotechnical structures caused by swelling of unsaturated cohesive soils. To determine the swelling relationship that describes this volume change behaviour two oedometer devices have been developed. By means of a modified oedometer apparatus it is possible to measure the swelling pressure both in the radial and the axial direction. The axial pressure is measured by a load cell while the radial pressure is obtained via strain gauges mounted on the outer surface of the oedometer ring. By means of these strain gauges the radial deformation of the ring is measured, from which the radial force and the radial pressure exerted on the sample is determined. Another oedometer apparatus, that is similar to the one mentioned before, has been developed especially for the present study. The oedometer ring is fitted inside with a membrane through which radial pressure is exerted under controlled conditions. The space between the ring and the membrane is filled with a fluid. The adjustment of the fluid volume in the reservoir allows the control of the radial strain. Thus, this oedometer device is comparable to a triaxial apparatus. Detailed investigations have been carried out using this equipment on soils with swelling potential. The initial and the final degree of saturation as well as the void ratio have been varied. From the results it has been identified that the swelling behaviour may be regarded as nonlinear elastic. Based on these experimental results approximate expressions have been derived for the one-dimensional and the three-dimensional swelling behaviour. They have been subsequently implemented in the FEM code ABAQUS via a subroutine interface. In the numerical simulation the elastic swelling deformations are superimposed to the mechanical deformations due to external loads and self-weight. For the mechanical deformations a linear elastic – ideal plastic stress-strain relati

Die Arbeit beschäftigt sich mit der Bestimmung der Zwangsbeanspruchungen und mit den daraus resultierenden Verformungen auf geotechnische Bauwerke infolge Quellen von teilgesättigten, bindigen Böden. Zur Ermittlung eines Quellgesetzes zur Beschreibung dieses Volumenänderungsverhaltens wurden zwei spezielle Oedometergeräte entwickelt. Mittels eines modifizierten Oedometers können radiale und axiale Quelldrücke getrennt voneinander gemessen sowie axiale Dehnungen zugelassen werden. Die axialen Spannungen werden über eine Kraftmessdose ermittelt während die radialen über Dehnungsmessstreifen, die an der Außenfläche des Oedometerringes befestigt sind, bestimmt werden. Mit Hilfe dieser Dehnungsmessstreifen wird die Radialverformung des Ringes gemessen. Daraus wird die Ringkraft und somit der Radialdruck, der auf der Probe wirkt, ermittelt. Ein anderes Oedometergerät, welches bis auf den Oedometerring baugleich zu dem bereits erwähnten ist, wurde speziell für die vorliegende Problematik entwickelt. In der Innenseite des Oedometerringes ist eine Membran angebracht, über die kontrolliert Radialdrücke erzeugt und gemessen werden können. Der Raum zwischen dem Ring und der Membran ist mit einem Fluid gefüllt. Durch Regulierung des im Reservoir befindlichen Fluidvolumens kann die Radialdehnung gesteuert werden. Somit ist dieses modifizierte Oedometergerät mit einem triaxialen Apparat vergleichbar. Es wurden umfangreiche Untersuchungen in den o. g. Geräten an einem quellfähigen Boden durchgeführt. Dabei wurden der Anfangs- und der Endsättigungsgrad sowie die Porenzahl variiert. Aus den Versuchen ergab sich, dass das Quellverhalten als nichtlinear elastisch angesehen werden kann. Anhand dieser Ergebnisse sind Approximationen für das eindimensionale sowie das dreidimensionale Quellverhalten aufgestellt und in den FEM - Code ABAQUS mittels einer Subroutine implementiert worden. In der numerischen Simulation werden die elastischen Quelldeformationen mit den mechanischen Deformatione, This thesis deals with the determination of the constraints and the resulting deformations on geotechnical structures caused by swelling of unsaturated cohesive soils. To determine the swelling relationship that describes this volume change behaviour two oedometer devices have been developed. By means of a modified oedometer apparatus it is possible to measure the swelling pressure both in the radial and the axial direction. The axial pressure is measured by a load cell while the radial pressure is obtained via strain gauges mounted on the outer surface of the oedometer ring. By means of these strain gauges the radial deformation of the ring is measured, from which the radial force and the radial pressure exerted on the sample is determined. Another oedometer apparatus, that is similar to the one mentioned before, has been developed especially for the present study. The oedometer ring is fitted inside with a membrane through which radial pressure is exerted under controlled conditions. The space between the ring and the membrane is filled with a fluid. The adjustment of the fluid volume in the reservoir allows the control of the radial strain. Thus, this oedometer device is comparable to a triaxial apparatus. Detailed investigations have been carried out using this equipment on soils with swelling potential. The initial and the final degree of saturation as well as the void ratio have been varied. From the results it has been identified that the swelling behaviour may be regarded as nonlinear elastic. Based on these experimental results approximate expressions have been derived for the one-dimensional and the three-dimensional swelling behaviour. They have been subsequently implemented in the FEM code ABAQUS via a subroutine interface. In the numerical simulation the elastic swelling deformations are superimposed to the mechanical deformations due to external loads and self-weight. For the mechanical deformations a linear elastic – ideal plastic stress-strain relati