Este trabalho trata do desenvolvimento, montagem e teste de equipamentos para ensaios de materiais de baixa condutividade hidráulica, o qual inclui sistemas de controle hidráulico de volume constante, permeâmetros do tipo parede flexível e interfaces água-percolante. A vantagem desse arranjo está no maior controle dos ensaios e, notadamente, na redução do tempo de ensaio com emprego do sistema hidráulico de volume constante (sistema fechado), quando comparado aos ensaios que empregam o sistema aberto de controle hidráulico. Para testar o equipamento, foram ensaiados geocompostos bentoníticos (geosynthetic clay liners - GCLs) de fabricação nacional, em corpos de prova moldados com diâmetro de 100 mm e também, em uma mistura de solo com bentonita. Os resultados da condutividade hidráulica obtidos para os geocompostos bentoníticos se situaram na ordem de \'10 POT.-9\' e \'10 POT.-10\' cm/s, compatíveis com os publicados na literatura sobre o material, e os ensaios na mistura solo-bentonita produziu resultados na ordem de \'10 POT.-8\' cm/s, e foram conseguidos com cerca de 3 horas de ensaio. Aborda-se ainda a aplicabilidade da lei de Darcy aos materiais ensaiados. / This work describes the development, construction, calibration and test of equipment for testing low hydraulic conductivity materials, which includes constant volume hydraulic control system, flexible wall permeameters and permeating water interfaces. The advantage of this kind of apparatus is the greater test control, notably, the reduction of test duration due to the use of a constant volume hydraulic system (closed system), when compared to the opened system hydraulic control test. In order to test the equipment, geosynthetic clay liners (GCLs) manufactured in Brazil was used as test specimens of 100 mm diameter and also, a mixture of soil and bentonite. The results of hydraulic conductivity obtained for the GCL were in the range of \'10 POT.-9\' to \'10 POT.-10\' cm/s, comparable to what has been published by the specialized literature on this material, and the tests with the soil-bentonite mixture resulted in a conductivity about \'10 POT.-8\' cm/s, after 3 hours running the test. The applicability of Darcy´s law to the tested materials is also referred to.

Geosynthetic reinforced soil (GRS) is a soil improvement technology in which closely spaced horizontal layers of geosynthetic are embedded in a soil mass to provide lateral support and increase strength. GRS is popular due to a relatively new application for bridge support, as well as long-standing application in mechanically stabilized earth walls. Several different GRS design methods have been used, and some are application-specific and not based on fundamental principles of mechanics. Because consensus regarding fundamental behavior of GRS is lacking, numerical and mathematical analyses were performed for laboratory tests obtained from the published literature of GRS under triaxial compression in consolidated-drained conditions. A three-dimensional numerical model was developed using FLAC3D. An existing constitutive model for the soil component was modified to incorporate confining pressure dependency of friction angle and dilation parameters, while retaining the constitutive model's ability to represent nonlinear stress-strain response and plastic yield. Procedures to obtain the parameter values from drained triaxial compression tests on soil specimens were developed. A method to estimate the parameter values from particle size distribution and relative compaction was also developed. The geosynthetic reinforcement was represented by two-dimensional orthotropic elements with soil-geosynthetic interfaces on each side. Comparisons between the numerical analyses and laboratory tests exhibited good agreement for strains from zero to 3% for tests with 1 to 3 layers of reinforcement. As failure is approached at larger strains, agreement was good for specimens that had 1 or 2 layers of reinforcement and soil friction angle less than 40 degrees. For other conditions, the numerical model experienced convergence problems that could not be overcome by mesh refinement or reducing the applied loading rate; however, it appears that, if convergence problems can be solved, the numerical model may provide a mechanics-based representation of GRS behavior, at least for triaxial test conditions. Three mathematical theories of GRS failure available in published literature were applied to the laboratory triaxial tests. Comparisons between the theories and the tests results demonstrated that all three theories have important limitations. These numerical and mathematical evaluations of laboratory GRS tests provided a basis for recommending further research. / Ph. D.

Doctor of Philosophy / Department of Civil Engineering / Mustaque Hossain / Geotextiles have been widely promoted for pavement structure over the past 30 years. However, there is a lack of well-instrumented, full-scale experiments to investigate the effect of geotextile reinforcement on the pavement design. In this study, full–scale accelerated tests were conducted on eight lanes of pavement test sections. Six out of these eight sections had granular bases reinforced with different types of woven geotextiles. The reinforced base sections and the control sections (with unreinforced base) were paved with Superpave hot-mix asphalt. Base and subgrade materials were the same for all sections while the test sections had different asphalt and base layer thicknesses. Each section was instrumented with two pressure cells on top of the subgrade, six strain gages on the geotextile body, six H-bar strain gages at the bottom of the asphalt layer, two thermocouples and one Time Domain Reflectometer (TDR) sensor. The sections were loaded to 250,000 to 500,000 repetitions of an 80-kN single axle load of the accelerated pavement testing machine. The mechanistic response of each section was monitored and analyzed at selected number of wheel passes. Results indicate that properly selected and designed geotextile-reinforced bases improve pavement performance in term of rutting and reduced pressure at the top of the subgrade. Finite element (FE) models were developed and verified using results from the full-scale accelerated pavement tests. The calibrated model was used to investigate the effects of geotextile properties on the pavement responses. FE analysis shows that benefits of reinforcement are more evident when stiffer geotextile is used.

The use of geosynthetics as reinforcement for the base layer of flexible pavement systems has grown steadily over the past thirty years. In spite of the evidence that geosynthetic reinforcements can lead to improved pavement performance, the specific conditions or mechanisms that enable and govern the reinforcement are unclear, largely remaining unidentified and unmeasured. The appropriate selection of design parameters for geosynthetics is complicated by the difficulty in associating their relevant properties to the improved pavement performance. In addition, pavement structures deteriorate under the combined effects of traffic loading and environmental conditions, such as moisture changes. However, these factors have not been studied together in the evaluation of the overall performance of pavement systems. Consequently, this research focused on the assessment of the effect of geosynthetics on the pavement structural section's ability to support traffic loads and to resist environmental changes. Accordingly, the primary objectives of this research were: (i) to determine the governing mechanisms and relevant properties of geosynthetics that contribute to the enhanced performance of pavement systems; (ii) to develop appropriate analytical, laboratory and field methods that are capable of quantifying the above properties for geosynthetics; and (iii) to enable the prediction of pavement performance depending on the various types of geosynthetics used. To fulfill these three objectives, an evaluative, laboratory and field study was performed. The improved performance of pavements due to addition of geosynthetics was attributed to the ability of geosynthetics to laterally restrain the base course material, thereby providing a confinement effect to the pavement. A parameter to quantify the soil-geosynthetic interaction at low displacement magnitudes based on the solution of an analytical model for geosynthetics confined in pullout box was proposed. The pullout tests were then conducted on various geosynthetics to obtain the proposed parameter for various geosynthetics. The quantitative magnitude of the parameter value from the laboratory tests was compared with the qualitative performance observed in the field test sections. Overall, a good agreement was obtained between the laboratory and field results, thereby providing confidence in the ability of the proposed analytical model to predict the governing mechanism for geosynthetic reinforced pavements. / text

Reinforcement of soil enables a soil slope or wall to be retained at angles steeper than the soil material’s angle of repose. Geosynthetic Reinforced Soil (GRS) systems enable shortened construction time, lower cost, increased seismic performance and potentially improve aesthetic benefits over their conventional retaining wall counterparts such as gravity and cantilever type retaining walls. Experience in previous earthquakes such as Northridge (1994), Kobe (1995), and Ji-Ji (1999) indicate good performance of reinforced soil retaining walls under high seismic loads. However, this good performance is not necessarily due to advanced understanding of their behaviour, rather this highlights the inherent stability of reinforced soil against high seismic loads and conservatism in static design practices. This is an experimental study on a series of seven reduced-scale GRS model walls with FHR facing under seismic excitation conducted using a shake-table. The models were 900 mm high, reinforced by five layers of stiff Microgrid reinforcement, and were founded on a rigid foundation. The soil deposit backfill was constructed of dry dense Albany sand, compacted by vibration (average Dr = 90%). The influence of the L/H ratio and wall inclination on seismic performance was investigated by varying these important design parameters throughout the testing programme. The L/H ratio ranged from 0.6 – 0.9, and the walls were primarily vertical except for one test inclined at 70o to the horizontal. During testing, facing displacements and accelerations within the backfill were recorded at varying levels of shaking intensity. Mechanisms of deformation, in particular, were of interest in this study. Global and local deformations within the backfill were investigated using two methods. The first utilised coloured horizontal and vertical sand markers placed within the backfill. The second utilised high-speed camera imaging for subsequent analysis using Geotechnical Particle Image Velocimetry (GeoPIV) software. GeoPIV enabled shear strains to be identified within the soil at far smaller strain levels than that rendered visible by eye using the coloured sand markers. The complementary methods allowed the complete spatial and temporal development of deformation within the backfill to be visualised. Failure was predominantly by overturning, with some small sliding component. All models displayed a characteristic bi-linear displacement-acceleration curve, with the existence of a critical acceleration, below which deformations were minor, and above which ultimate failure occurs. During failure, the rate of sliding increased significantly. An increase in the L/H ratio from 0.6 to 0.9 caused the displacement-acceleration curve to be shallower, and hence the wall to deform less at low levels of acceleration. Accelerations at failure also increased, from 0.5g to 0.7g, respectively. A similar trend of increased seismic performance was observed for the wall inclined at 70o to the horizontal, when compared to the other vertical walls. Overturning was accompanied by the progressive development of multiple inclined shear surfaces from the wall crest to the back of the reinforced soil block. Failure of the models occurred when an inclined failure surface developed from the lowest layer of reinforcement to the wall crest. Deformations largely confirmed the two-wedge failure mechanism proposed by Horii et al. (2004). For all tests, the reinforced soil block was observed to demonstrate non-rigid behaviour, with simple shearing along horizontal planes as well as strain localisations at the reinforcement or within the back of the reinforced soil block. This observation is contrary to design, which assumes the reinforced soil block to behave rigidly.

L’aménagement progressif du territoire conduit à l’exploitation de nouvelles zones, actuellement délaissées, car présentant des risques pour la sécurité des usagers. C’est notamment le cas des zones d’effondrements potentiels qui sont liées à la présence de cavités souterraines. Parmi les nombreuses solutions préventives, le renforcement géosynthétique permet de prévenir les risques d’effondrement localisés. Cette solution de renforcement est largement utilisée à la fois pour ses avantages économiques et environnementaux, que pour sa facilité et rapidité de mise en œuvre. Néanmoins, les méthodes de conception existantes des plateformes granulaires renforcées par géosynthétiques sont fondées sur diverses hypothèses simplificatrice et ne prennent pas en compte toute la complexité du problème. En effet, ces méthodes ne considèrent pas par exemple l’influence du mode d’ouverture de la cavité, le foisonnement du sol granulaire au droit de la cavité ou encore la distribution de charge sur le géosynthétique après ouverture de la cavité.La présente étude tente d’améliorer les méthodes de dimensionnement en analysant les mécanismes développés dans la plateforme granulaire renforcée sur la base d’une campagne expérimentale couplée à des modélisations numériques.Un dispositif expérimental a été développé pour simuler l’ouverture d’une cavité sous une plateforme renforcée par géosynthétique. Ce dispositif permet de simuler deux modes d’ouverture : une trappe qui s’abaisse ou une ouverture concentrique, pour différentes hauteurs de plateformes. Les mécanismes de renforcement sont étudiés en mesurant la déflexion du géosynthétique, le tassement en surface et la distribution de contrainte verticale qui s’applique du le géosynthétique. Un modèle numérique par éléments finis a été calibré sur les résultats expérimentaux puis utilisé pour analyser finement les mécanismes pour de nombreuses configurations.Cette étude expérimentale et numérique a permis d’améliorer la compréhension des mécanismes de transfert de charge et de foisonnement dans la zone effondrée et de valider expérimentalement l’influence du mode d’ouverture sur les mécanismes. Sur la base de ces résultats, des propositions sont formulées pour améliorer le dimensionnement des plateformes renforcées par géosynthétiques soumises à des effondrements localisés. / The progressive development of the territory leads to the exploitation of new areas, which are currently being abandoned because they come up risks to the safety of users. This is particularly the case for areas of potential collapse that are related to the presence of underground cavities. Among the many preventative solutions, geosynthetic reinforcement prevents localized collapse. This solution is widely used for both its economic and environmental benefits, as well as for its ease and speed of setting up. However, the existing design methods for granular platforms reinforced by geosynthetic are based on various simplifying assumptions and do not take the complexity of the problem into account. These methods do not consider, for example, the influence of how the cavity is opened, the expansion of granular soil above the cavity, or the stress distribution on the geosynthetic after opening the cavity.The present study tries to improve the design methods by analyzing mechanisms developed inside the reinforced granular platform on the basis of an experimental study coupled with numerical simulations.An experimental device was developed to simulate the opening of a cavity under a platform reinforced by geosynthetic. This device allows simulating two types of opening: a trapdoor or a concentric opening, for various heights of platforms. The mechanisms are studied by measuring the deflection of the geosynthetic, the settlement at the surface and the stress distribution applied of the geosynthetic. A finite element model was calibrated on the experimental results then used to analyze mechanisms finely for many configurations.This experimental and numerical study allows improving the understanding of the stress distribution, the soil expansion above the cavity and experimentally validated the influence of the opening mode on the mechanisms. Based on these results, proposals are formulated to improve the design of geosynthetic-reinforced platforms subject to localized collapse.

Os aterros reforçados sobre solo mole de resistência crescente com a profundidade, podem apresentar problemas durante o processo construtivo com respeito às rupturas e aos recalques inesperados. O presente trabalho visa avaliar o comportamento dos aterros reforçados a través de um estudo numérico, levando aos aterros até a ruptura sob condição não-drenada devido ao carregamento rápido, com o objetivo de estimar a influência da rigidez do reforço nas deformações, além disso, estudar o mecanismo da interação solo-reforço para um aterro reforçado. Foi utilizada a metodologia apresentada por Hinchberger & Rowe (2003), que leva em conta os recalques imediatos durante e após a construção. As análises numéricas de tensão-deformação foram realizadas pelo software PHASE 2, a calibração do programa foi feita com a literatura de aterros reforçados. Pretendeu-se mostrar a influência de uma camada superficial de areia sobre a argila mole na altura de ruptura e na deformação do reforço. Pelo método de elementos finitos foi definida uma metodologia para calcular as deformações do reforço para uma altura determinada e avaliar a estabilidade mediante o método de equilíbrio limite. Além disso, essa metodologia pode ser empregada para dimensionar o reforço requerido para um determinado fator de segurança. / Reinforced embankments on soft clayey soil where the strength increases with depth may present problems during construction process relative to failure and unexpected settlements. This study aims to evaluate the embankments behavior with a numerical study; the embankments were taken to failure in the undrained shear strength condition due to rapid upload to study the effect of reinforcement tensile stiffness on the reinforcement strains. Besides, it aimed to study the mechanism of soil-reinforcement interaction for a reinforced embankment. The method of Hinchberger & Rowe (2003) was used, which considers the displacements before and post construction. The numeric analysis of stress-strain was performed by the software PHASE 2; the calibration of the software was made according to published reinforced embankment literature. The study intends to show the influence of a sand layer above the clayey soil, on the failure height and reinforcement strains. Based on finite elements methods, a methodology was defined to estimate the reinforcement strains for a required design height and to study the stability by performing limit equilibrium analysis. Furthermore, this methodology could be used to specify the required reinforcement stiffness for a specific factor of safety.

Numerical analyses of two different geotechnical problems, namely a bridge abutment and a geosynthetic reinforced embankment are presented in this thesis. Settlement, bearing capacity and slope stability are the major factors that need to be considered in the design of a foundation near a sloped fill. In this thesis, the behaviour of a small scale model footing located near the shoulder of a sloped fill was investigated numerically. Single and multiple layers of geogrid were used to reinforce the sloped fill, and their effects on the load-deformation behaviour and bearing capacity of the footing were explored. The analyses showed 80%, 168%, 295% and 375% maximum improvement in the ultimate bearing capacity with 1, 2, 3 and 4 reinforcement layers respectively. This maximum improvement depends on the embedment depths of the reinforcement layers below the foundation and the suggested optimal depths are discussed. Typically, greatest improvement in ultimate bearing capacity with a single layer of reinforcement was obtained when the reinforcement was at a depth between 0.50 and 0.75 times the foundation width. Similarly, highest ultimate bearing capacity with 2 reinforcement layers was predicted when the spacing between them was 1.0 times the width of the foundation. However, higher settlement was estimated at failure for the reinforced sloped fill than the unreinforced one. The second problem investigated was the three-dimensional (3D) analysis of Sackville embankment, a geosynthetic reinforced embankment on soft soil. Previous analyses using two-dimensional (2D) numerical modelling of Sackville embankment indicated potential 3D effects affecting the performance of this embankment. Therefore, 3D analysis incorporating geometric variations of Sackville embankment foundation soil, anisotropic model for fluid flow, mobilization of geotextile stresses in minor direction and the boundary effects (lateral directions) were taken into account in this analysis. The predicted performance of Sackville embankment were compared with the field data and the previously reported 2D analysis results in terms of vertical and horizontal displacements and excess pore pressures in the foundation soil, and geotextile stresses, strains and displacements. Better overall predictions of the Sackville embankment performance was obtained from this 3D analysis than the previous analysis reported in the literature.

The different material layers as part of a road construction fill all a function so theroad becomes durable, safe, comfortable and aesthetically pleasing. Recently, anew group of construction materials started to play an important role in roadconstruction – geosynthetics. This thesis addresses the two most common types ofgeosynthetics used in modern road construction, namely geogrids and geotextiles.The most common use of geogrids is reinforcement of poor subgrade by usinggeogrid soil reinforcement, which occurs when road material particles wedge inthe geogrid’s mesh. Geotextiles act partly as a barrier that prevents the finermaterial in the below ground from being mixed with coarser upper material andalso act as a load spreader.Road contractors often face a choice of whether geogrids and/or geotextiles areappropriate in a particular road project and also how much profit the choice mightbring. This phase in the tender calculation process is the intended scope of thisthesis. The thesis deals with both the "hard" cost-function aspects and the "softer" values e.g. ecology and social aspects. To facilitate the comparison, a comparative modelwas developed. The comparison is done for two different cases: Case A – roadconstruction on the bank and Case B – road construction in hill cutting. In Case A “with geogrid”, the amount of trenching becomes smaller due to saving ofreinforcement layer thickness.The completed cost comparison indicates an opportunity for significant savings forroad contractors that choose to strengthen the road’s superstructure with geogrid. In Case A “with geotextile”, no trenching saving is likely, but instead, bearingcapacity improvement is a long term financial gain. An estimated cost for Case B “hill cutting road”, is approximately SEK 600 000 which is less than the cheapestcase i.e. Case A “with geogrid”. After the use of geogrids, the function changes are as following: Traffic load distribution on the terrace has increased and lateral landmovements have reduced Filling material density has increased due to geogrid wedging mechanism Frictional resistance has increased due to the fact that pavement materialparticles have been extended due to geogrid’s wedging mechanism Superstructure’s total thickness has been reduced due reinforcement layerthickness’s reduction After the use of geogrids, the function changes are as following: The composition and function of the road pavement and terrace materialremains intact. (The words "remains intact" run true to the concept of"functional change" but in this case, it is meant that the materialcomposition and function could have been worse if not properly chosengeotextile was added to the design). The scenario "gritty mud" is avoided if the geotextile has been enteredcorrectly with the right overlap. Results concerning the ecological aspects show that the trenching reduction due touse of geogrids leads to fewer ground motion, lesser soil degradation and fewerenvironmental harmful emissions because the use of road construction equipmentdeclines. Reduced distribution excavation thanks to geotextiles leads to both thesame advantages as in the sentence above and partly to the fact that the amount ofmaterials that need become deposited decreases. In addition, the risk ofgroundwater lowering due to artificial drainage ditch is minimized. The road'stotal life cycle is extended, which contributes to reducing the environmentalimpacts arising from road repair and construction of a new road if the old onestops fulfilling its function. Degradation of geogrids and geotextiles is notenvironmentally harmful, but takes a long time in natural conditions, which meansthat in practice, the use must be documented and taken care of (regarding finalcombustion in a prudent manner).Regarding social sustainability, the following conclusion could be drawn: a roadthat has a higher carrying capacity leads to higher traffic safety due to minimalsubsidence, track formation and cracking. Road safety is seen by citizens not onlyas something that the private motorists are responsible for but also something thatroad authorities should consider when planning for a socially sustainable society.Another conclusion is road maintenance frequency and hereby the taxpayers' longtermeconomic gain. The road extended total life cycle contributes to the reductionof road repairs and new construction of roads. In other words, it is not just “oneroad construction company” that wins economically by minimizing their warrantywork. The discussion concerns the cases where geosynthetics are not economicallyoptimal bearing capacity choice, such as solid rock cutting or a stretch of roadwhich has weaker parties but for which, a filling material yet compensates for theexcavated. The report concludes with a special discussion of the Swedishgeosynthetics research. The geosynthetics industry is controlled by private actors(developers, manufacturers and others) and contractors who do not like releasinginformation that might reduce their competitiveness. Therefore, the independentresearcher’s role has been quite weak and mostly reduced to “play ‘catch-up’insofar as investigating the nuances of how geosynthetics work "(Koerner, 2005). Another reason for the lack of reports on geosynthetics benefit is the long term asa sharp research project takes to plan, implement, control and evaluate. WhilstTrafikverket’s and local municipalities’ play the leading role in the Swedish roadconstruction industries, it should be in their interest to start taking geosyntheticsmore seriously by implementing credible tests and full scale trials and publishpractically applicable documents based on objective tests of structures containing geosynthetics.

The dissertation are analyzing the main characteristics of asphalt concrete influencing shear deformation, appearance and increase of rutting connected with them, analyze the influence of geosynthetic material characteristics onto asphalt concrete functioning.