In 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.

Les Installations de Stockage de Déchets actuelles sont munies de barrieres de confinement composites géosynthétiques et minerales. En couverture, les interfaces entre composants de ces systèmes installés sur forte pente peuvent constituer des surfaces de glissement préférentiel. L'étude de ces interfaces est donc cruciale pour l'évaluation de la stabilité des barrières de ces installations. Le comportement de ces interfaces, en particuliers des interfaces géosynthétique - géosynthétique se révèle complexe: il va dépendre de la nature des polymères, de l'endommagement , de la vitesse de glissement relatif, de la température. Les conditions de chargement sont aussi primordiales, statiques ou dynamiques (cas de seisme). L'originalité du travail effectué dans le cadre de la présente étude tient d'abord aux dispositifs expérimentaux utilisés en parallèle, un Plan incliné et une Table Vibrante, les deux permettant de simuler les conditions réelles sur site, sous faible contrainte normale, en conditions d'une part statiques, d'autre part dynamiques. Des procédures d'essai nouvelles ont permis une interprétation fine des résultats d'essais. En particulier la variation du frottement en fonction de la cinétique d'essai est clairement démontrée, et le couplage des résultats obtenus dans les deux configurations d'essai permet de montrer que leur interprétation est complexe et ne peut se limiter à celle proposée par la norme européenne. En particulier, le niveau du déplacement relatif et la vitesse de déplacement influent significativement sur les résultats. Une étude spécifique de l'endommagement est aussi présentée. / Modern landfills are equipped with multi-layered liners, including geosynthetic-geosynthetic and soil-geosynthetic interfaces. The interfaces represent weakness surfaces where the shear strength is a crucial aspect for the landfill stability. The behaviour of each interface can be different depending on the interactions of the materials in contact under the different load conditions (i.e. static and seismic loading). Nevertheless, the assessment of the geosynthetic interface shear strength can be difficult depending on different factors such as mechanical damage, time-dependent processes (ageing), stress dependent processes (such as repeated loading), coupled effects of both time and stress-strain dependent processes (creep or relaxation). In the present work, the static and the dynamic behaviour of typical geosynthetic - geosynthetic interfaces is investigated by means of the Inclined Plane and the Shaking Table tests since both devices permit to simulate experimental conditions close to them expected in landfill cover systems (low normal stress, small and large deformations). Two new test procedures are proposed and applied in order to assess the interface friction at both devices during all the phases of the tests. Taking advantage of the complementarity of both facilities, an innovative interpretation of test results considering the evolution of the shear strength parameters, passing from the static to the dynamic loading conditions, from small to large displacements is carried out. Furthermore, the dependence of the interface friction on different parameters such as the kinematic conditions, the normal stress and the mechanical damage is also investigated. In light of test results, it has been demonstrated that the variation of the interface friction could be significant, depending on the loading conditions (static or dynamic), on the actual kinematic conditions and on the level of deformation at which the interface is subjected.

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.

<p>There are significant problems during construction to establish an adequate foundation for fills and/or subgrade for pavements when the natural ground has low-bearing soils. Geosynthetics such as geogrids, geotextiles and/or geocells could provide an alternative, less costly in time and money, to establish an adequate foundation for the fill and/or subgrade. There is extensive evidence in the literature and on DOTs practices about the suitability of using geotextiles in pavements as separators. Previous studies have also shown that the use of geogrids in flexible pavements as a reinforcing mechanism could decrease the thickness of the base layer and/or increase the life of the pavement. In this study, analyses of selected pavement designs using Pavement ME, while considering geogrid-enhanced base or subgrade resilient modulus values, showed that geogrid-reinforcement, when placed at the interface between subgrade and base, did not produce significant benefits, as only a modest increase in pavement life was predicted. In addition, parametric finite element analyses were carried out to investigate the potential benefits of placing a geogrid at the base of a fill over a localized weak foundation zone. The analyses showed that the use of geogrids is beneficial only when: (a) the stiffness of the weak foundation soil is about an order of magnitude smaller than the rest of the foundation soil; and (b) the horizontal extent of the weak foundation soil is at least 30% of the base of the embankment foundation. The largest decrease in differential settlements at the surface of the fill, resulting from geogrid-reinforcement, was less than 20% and, therefore, it is unlikely that the sole use of geogrids would be sufficient to mitigate differential settlements. Based on previous studies, a geocell mattress, which is a three-dimensional geosynthetic filled with different types of materials, could act as a stiff platform at the base of an embankment and bridge over weak zones in the foundation. However, given the limited experience on the use of geocells, further research is required to demonstrate that geocells can be effectively used instead of other reinforcement methods.</p>

A laboratory test program was conducted to determine the moisture-suction relationships of geosynthetic clay liners (GCLs). Moisture-suction relationships were determined by combining suction data from pressure plate tests, contact filter paper tests, and relative humidity tests, then fitting water retention curves (WRCs) to the data. WRCs were determined for wetting processes and drying processes in terms of gravimetric moisture content and volumetric moisture content. The effects of GCL type, hydration solution, wet-dry cycles, and temperature on the moisture-suction relationships were analyzed. The three GCLs of the test program consisted of configurations of woven and nonwoven geotextiles reinforced with needlepunched fibers. A geofilm was adhesively bonded to the nonwoven side of one of the GCL products. The hydration solution tests involved hydrating GCLs with deionized water, tap water, 0.1 M CaCl2, or soil water from a landfill cover test plot for a 30-day conditioning period prior to testing. Cyclic wet-dry tests were conducted on the GCL specimens subjected to 20 wet-dry cycles from 50% to 0% gravimetric moisture content prior to testing. Temperature tests were conducted at 2°C, 20°C, and 40°C. GCL type affected moisture-suction relationships. The GCLs with an adhesively-bonded geofilm exhibited lower air-entry suction and higher residual suction than GCLs without a geofilm. The degree of needlepunched fiber pullout during hydration contributed to hysteresis between wetting WRCs and drying WRCs. Hysteresis was high for suction values below air-entry suction and was low for suction values greater than air-entry suction. Cation exchange reduced the water retention capacity for all three GCL types. The saturated gravimetric moisture contents were reduced from approximately 140% to 70% for wetting WRCs and 210% to 90% for drying WRCs for GCLs hydrated in deionized water compared to CaCl2 solution. Hysteresis of the nonwoven product decreased from 71%, to 62%, to 28% with respect to deionized water, tap water, and CaCl2 solution. Hysteresis of the woven product exposed to soil water was 24% and 0%, in terms of saturated gravimetric moisture content and saturated volumetric moisture content, respectively. The swell index, Atterberg Limits, mole fraction of bound sodium, and scanning electron microscopy images that were determined of bentonite from the conditioned GCLs indicated that changes in water retention capacity corresponded with cation exchange. Wet-dry cycles and temperature affected the moisture-suction behavior for GCLs. Wet-dry cycles reduced hysteresis and increased the swelling capacity of GCL specimens. Microscopy images indicated that wet-dry cycles caused weak orientation of the clay particles. Increasing temperature resulted in a small decrease in water retention capacity. Results of the test program provided a means for predicting unsaturated behavior for GCLs.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第18435号 / 地環博第117号 / 新制||地環||23(附属図書館) / 31293 / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 高岡 昌輝, 准教授 乾 徹 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

A laboratory test program was conducted to investigate the effects of temperature, solution strength, and applied stress over increasing conditioning durations on cation exchange processes in sodium bentonite (Na-B) geosynthetic clay liners (GCLs). The test program was intended to determine if the variables of temperature, solution strength, and applied stress had beneficial or detrimental effects on the engineering behavior of Na-B GCLs in municipal solid waste (MSW) landfills and laboratory testing applications. Needlepunched-reinforced, double non-woven Na-B GCL specimens were conditioned in fluids of increasing ionic strength (DI water, 2 mM CaCl2, 50 mM CaCl2, and 200 mM CaCl2 representing control, pore water, mild MSW leachate, and harsh MSW leachate, respectively), temperatures of 5 degrees C, 20 degrees C, 40 degrees C, and 60 degrees C, and overburden stresses (30 kPa and 500 kPa representing stresses experienced by cover and bottom liner systems, respectively) which are all representative of geoenvironmental conditions observed in MSW landfill barrier systems. Cation exchange in the bentonite component of all conditioned Na-B GCL specimens was quantified by measuring the bound cation (BC) complexes and cation exchange capacities (CEC) of the specimens using inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis and by conducting index tests to determine the dimensional characteristics, swell index, and gravimetric moisture content of the specimens. For zero stress conditions, periodic measurements of electrical conductivity, total dissolved solids, sodium and calcium cation concentration, and temperature of the conditioning fluids were recorded to supplement bound cation complex data. For applied stress conditions, electrical conductivity, total dissolved solids, and temperature of the conditioning fluid were recorded. For zero stress conditions, 152 mm x 152 mm Na-B GCL specimens were conditioned in all conditioning fluids and temperatures over increasing time durations ranging from 4 hours to 32 days. For applied stress conditions, 60-mm-diameter Na-B GCL specimens were conditioned in 50 mM CaCl2 conditioning fluid at all temperatures for 4 to 16 days under the applied overburden stresses of 30 kPa and 500 kPa. Temperature, solution strength, and applied stress were all observed to affect cation exchange in the bentonite component of Na-B GCLs. Cation exchange processes were observed to increase with increasing temperature, increasing solution strength, and decreasing applied overburden stress. The majority of cation exchange processes were observed to occur within 8 to 10 days for specimens conditioned under zero stress. Cation exchange processes were observed to have a higher sensitivity to changes in solution strength (up to 625% increase in the change of Na+ BC from DI water to 200 mM CaCl2) compared to changes in temperature (up to 52% increase in the change of Na+ BC from 5 degrees C to 60 degrees C) in zero stress conditions. Changes in the bound cations of the Na-B GCL specimens over time were not reflected in the periodic electrical conductivity measurements taken of the high strength conditioning fluids. The results of this study can be used for quality assurance evaluations of in-service GCLs using thresholds developed for index properties. From the numerical thresholds determined in this study, hydrated Na-B GCL specimens sampled from the field conditioned under zero stress that exhibit swell indices greater than or equal to approximately 70% of the swell index reported by the manufacturer and gravimetric moisture contents of greater than or equal to approximately 200% will likely exhibit adequate hydraulic barrier performance. Hydrated Na-B GCL specimens sampled from the field conditioned under zero stress that exhibit swell indices of less than or equal to approximately 20% of the swell index reported by the manufacturer and gravimetric moisture contents of less than or equal to approximately 100% will likely exhibit inadequate hydraulic barrier performance. The Na-B GCL component of cover liner systems may be susceptible to high rates of cation exchange due to experiencing low overburden stress and elevated temperatures compared to typical earth temperatures. The Na-B GCL component of bottom liner systems may exhibit low rates of cation exchange due to experiencing high overburden stress and cooler temperatures.

A large amount of research has been conducted to investigate the influence of incorporating geosynthetics in highway pavements in laboratory-scale and full-scale experiments, and performance improvement has been well documented. In most cases, geosynthetics have been found to improve rutting resistance or reduce vertical pressure on the subgrade. Airfield pavements are typically thicker than highway pavements and are subjected to higher wheel loads and tire pressures. Thus, the benefit of geosynthetics within airfield pavements may not be as pronounced as that observed in relatively thin highway pavements. Prior to the writing of this dissertation, few documented studies focused on the performance of geosynthetic inclusion in airfield pavements and existing Department of Defense (DOD) guidance for geosynthetic inclusion had not been updated for several decades. The primary objectives of this dissertation were to update the DOD geosynthetic design methodology, to interpret results of laboratory-scale and full-scale experiments conducted specifically to evaluate geosynthetic performance in airfield pavements, and to determine if a competitive market exists for geosynthetic inclusion in airfield pavements. The main body of this dissertation is a compilation of four complementary articles that build upon the primary components of the main objectives. Chapter 1 and Chapter 2 present an introduction and a literature review, respectively. Updates to the DOD design methodology are presented in Chapter 3, results of laboratory-scale and full-scale evaluations are presented in Chapter 4 and Chapter 5, respectively, and potential implications of geosynthetic inclusion in airfield pavements are presented in Chapter 6. Chapter 7 presents overall conclusions and recommendations. Overall, it was found that, while some geosynthetics can be beneficial in airfield pavements, more rutting than would typically be allowed on an operational airfield was required to realize a meaningful performance benefit. In cases where geosynthetics were included in an airfield pavement, it was found that an extension of service life rather than a reduction in aggregate thickness was more optimal in assigning a geosynthetic value. Finally, the results of this dissertation indicated that geosynthetic inclusion in airfield pavements did not yield the same benefit level as that documented in the literature for highway pavements.

No description available.

When an embankment is to be constructed over ground that is too soft or compressible to adequately support the embankment, columns of strong material can be placed in the soft ground to provide the necessary support by transferring the embankment load to a firm stratum. This technology is known as column-supported embankments (CSEs). A geosynthetic-reinforced load transfer platform (LTP) or bridging layer may be constructed immediately above the columns to help transfer the load from the embankment to the columns. There are two principal reasons to use CSEs: 1) accelerated construction compared to more conventional construction methods such as prefabricated vertical drains (PVDs) or staged construction, and 2) protection of adjacent facilities from distress, such as settlement of existing pavements when a roadway is being widened. One of the most significant obstacles limiting the use of CSEs is the lack of a standard design procedure which has been properly validated. This report and the testing described herein were undertaken to help resolve some of the uncertainty regarding CSE design procedures in light of the advantages of the CSE technology and potential for significant contributions to the Strategic Highway Research Program, which include accelerated construction and long-lived facilities. Twelve design/analysis procedures are described in this report, and ratings are assigned based on information available in the literature. A test facility was constructed and the facility, instrumentation, materials, equipment, and test procedures are described. A total of 5 CSE tests were conducted with 2 ft diameter columns in a square array. The first test had a column center-to-center spacing of 10 ft and the remaining four tests had center-to-center spacings of 6 ft. The Adapted Terzaghi Method of determining the vertical stress on the geosynthetic reinforcement and the Parabolic Method of determining the tension in the geosynthetic reinforcement provide the best agreement with the test results. The tests also illustrate the importance of soft soil support in CSE performance and behavior. A generalized formulation of the Adapted Terzaghi Method for any column/unit cell geometry and two layers of embankment fill is presented, and two new formulations of the Parabolic Method for triangular arrangements is described. A recommended design procedure is presented which includes use of the GeogridBridge Excel workbook described by Filz and Smith (2006, 2007), which was adapted for both square and triangular column arrangements. GeogridBridge uses the Adapted Terzaghi Method and the Parabolic Method in a load-displacement compatibility design approach. For completeness, recommended quality control and quality assurance procedures are also provided, and a new guide specification is presented. / Ph. D.