Correct understanding of passive force behavior is particularly key to lateral evaluations of bridges because plastic deformation of soil backfill is vital to dissipation of earthquake energy and thermally-induced stresses in abutments. Only recently have studies investigated the effects of skew on passive force. Numerical modeling and a handful of skewed abutment tests performed in sand backfill have found reduced passive force with increasing skew, but previous to this study no skewed tests had been performed in gravel or Geosynthetic Reinforced Soil (GRS) backfills. The goal of this study was to better understand passive force behavior in non-skewed and skewed abutments with gravel and GRS backfills. Prior to this study, passive pressures in a GRS integrated approach had not been investigated. Gravel backfills also lack extensive passive force tests.Large-scale testing was performed with non-skewed and 30° skewed abutment configurations. Two tests were performed at each skew angle, one with unconfined gravel backfill and one with GRS backfill, for a total of four tests. The test abutment backwall was 11 ft (3.35 m) wide, non-skewed, and 5.5 ft (1.68 m) high and loaded laterally into the backfill. However, due to actuator loading constraints, all tests except the non-skewed unconfined gravel test were performed to a backfill height of 3.5 ft (1.07 m). The passive force results for the unconfined gravel test was scaled to a 3.5 ft (1.07 m) height for comparison.Test results in both sets of backfills confirmed previous findings that there is significant reduction in passive force with skewed abutment configurations. The reduction factor was 0.58 for the gravel backfill and 0.63 for the GRS backfill, compared to the predicted reduction factor of 0.53 for a 30° skew. These results are within the scatter of previous skewed testing, but could indicate that slightly higher reduction factors may be applicable for gravel backfills. Both backfills exhibited greater passive strength than sand backfills due to increased internal friction angle and unit weight. The GRS backfill had reduced initial stiffness and only reached 79% to 87% of the passive force developed by the unreinforced gravel backfill. This reduction was considered to be a result of reduced interface friction due to the geotextile. Additionally, the GRS behaved more linearly than unreinforced soil. This backfill elasticity is favorable in the GRS-Integrated Bridge System (GRS-IBS) abutment configuration because it allows thermal movement without developing excessive induced stresses in the bridge superstructure.

Yes / Because of the recent worldwide construction expansion, new roads and buildings may be constructed over already existing buried infrastructures e.g. buried utility pipes, leading to excessive loads threatening their stability and longevity. Limited research studies are available to assess the effect of geogrid reinforcing layers inclusion on mitigating the additional stresses on buried structures due to cyclic loadings. In this research, large-scale fully instrumented laboratory tests were conducted to investigate the behaviour of flexible High-Density Polyethylene pipes (HDPE), in unreinforced and geogrid-reinforced sand, subjected to incrementally increasing cyclic loading, e.g. due to different vehicles capacities or load increase with passing time. Results illustrated that deformation rate in pipe and footing, strain generation rate in pipe and reinforcing layers are rapidly increased in the initial loading cycles, in particular during the first 300 cycles, and then the rate of change decreases significantly, as more cycles are applied. In the unreinforced case, increasing the pipe burial depth significantly reduced the generated deformation and strain in the pipe; however, it has a situational effect on the footing settlement, where it increased after pipe burial depth to its diameter ratio (H/D) of 2.5. In reinforced cases, deformation and strain significantly reduced with the increase in pipe burial depth and number of reinforcing layers. Measurement of strain illustrated that strain generated in the lower reinforcing layer is always higher than that recorded in the upper one, regardless pipe burial depth and value of applied load.

Yes / Reinforced piled embankment technique is becoming increasingly utilised for the construction over soft grounds due to its efficiency on reducing potential settlement, speed of construction and associated cost. Most of previous studies focused on developing understanding for the behaviour of thick embankments that are loaded with a static surcharge load. Data for the behaviour of shallow piled embankments under cyclic loadings are scarce. In this study, an experimental programme was undertaken using a fully instrumented testing rig to generate data and improve our understanding for the behaviour of unreinforced and reinforced shallow piled embankments subject to monotonic and cyclic loadings that were applied over a predetermined area of the embankment. The experimental results showed that collapse of soil arching is imminent and occurs during the first few cycles of load. However, regain of strength and recovery of the arching effect was observable during further stages of cyclic loadings due to densification of the embankment material and deformation of the soft subsoil. Inclusion of reinforcement layers was found to enhance the performance of load transfer mechanisms by concentrating stresses on pile caps. The results clearly showed a significant reduction in surface settlement, soft subsoil settlement and heaving with increasing the number of reinforcement layers.

No description available.

[pt] No presente trabalho foi estudado o comportamento de um muro de solo reforçado com 5m de altura e 1700m de extensão, construído como parte do dique que compõe o Depósito de Resíduos de Bauxita 7 da ALCOA Alumínio S.A. em Poços de Caldas, MG. Neste muro foram empregados um solo residual siltoargiloso obtido no local e geogrelhas. O muro foi instrumentado para medição de deslocamentos horizontais e verticais durante a construção. Na mesma área, também foi construído um aterro experimental de 2,6m de altura que permitiu a realização de 16 ensaios de arrancamento de grandes dimensões. Foram realizados ensaios de laboratório para definir os parâmetros de resistência e deformabilidade do solo. Os parâmetros obtidos foram empregados em simulações numéricas da construção do muro e dos ensaios de arrancamento pelo Método dos Elementos Finitos, utilizando-se o programa PLAXIS 2D v.8. Os resultados obtidos demonstraram que os deslocamentos ocorridos durante a construção do muro são comparáveis a valores reportados por outros autores. As previsões numéricas da construção do muro e dos ensaios de arrancamento apresentaram boa concordância com os resultados medido em campo. Constatou- se que a resistência ao arrancamento obtida foi superior às previsões baseadas em formulações tradicionais da literatura. / [en] The behavior of a 5m high and 1700m long reinforced soil wall was studied in this work. The wall constitutes the upper part of a dike constructed in Poços de Caldas-MG, Brazil, by Alcoa Aluminum S.A. to contain Bauxite residues. The wall was constructed using geogrids and a residual silty-clay. Two wall sections were instrumented. Horizontal and vertical displacements were monitored during construction. An 2.6m high experimental fill was constructed to conduct 16 large-scale pullout tests. Soil laboratory tests were conducted to define the strength and deformability parameters. The construction of the wall and the pullout tests were simulated using the PLAXIS 2D v.8 Finite Element Method code. The numeric predictions agree well with the field results. The measured horizontal displacements show good agreement with results reported by other authors and the pullout resistance was found to be greater than the values estimated by traditional methods.

A numerical investigation was conducted to evaluate the geotechnical safety and slope stability of Municipal Solid Waste (MSW) landfills, considering the effects of geosynthetic reinforcements, biodegradation of the waste, and associated changes in material properties, and extreme wind force simulating hurricane conditions. Three different landfill slopes, 1:1, 1:2, and 1:3 having the height of 122m and width of 2134m, were analyzed using Limit Equilibrium Method (SLOPE/W) and Finite Element Modeling (ANSYS). Techniques developed in this study were used to analyze a case history involving a geogrid reinforced mixed landfill expansion located in Austria. It was found that few years after construction of the landfill, there is a significant decrease in the FS due to biodegradation. Extreme wind loading was also found to cause a substantial loss in the FS. The geosynthetic reinforcement increased the slope stability and approximately compensated for the damaging effects of biodegradation and wind loading. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Improvements in quality of life, population growth, and environmental restrictions associated with the burning of fossil fuels will accentuate the need for renewable energy and energy geo-storage. A salient characteristic of these systems is that they impose numerous cycles of effective stress, temperature, and humidity on the surrounding geomaterials. This thesis quantifies future energy consumption based on realizable scenarios and explores the behavior of geomaterials subjected to mechanical and thermal cycles in view of energy-related applications. The long-term behavior of geotechnical systems subjected to a large number of mechanical load cycles is studied with a new numerical scheme based on a hybrid finite element formulation. The numerical scheme satisfies initial conditions as well as fundamental characteristics of soil behavior, such as threshold strain, terminal density, and long-term ratcheting. Numerical results show that shallow foundations subjected to repetitive loading experience strain accumulation and stress redistribution. On the other hand, the long-term behavior of energy piles, exposed geomembranes on slopes, and jointed rock masses subjected to cyclic thermal changes is studied using a combination of numerical, analytical, and experimental methods. Results show that thermal cycles lead to the gradual accumulation of plastic displacements, which may be amplified by thermally-induced wedging in jointed rock masses. In general, cumulative effects caused by repetitive loads increase with the number of cycles, the static factor of safety, the amplitude of the cyclic excitation, and the magnitude of the cyclically-induced displacement with respect to the critical elastic displacement.

[pt] Em obras ambientais, onde geossintéticos são utilizados como sistema de proteção e de cobertura de taludes, é de extrema importância o conhecimento do mecanismo de interação solo-geossintético, através da obtenção dos parâmetros de resistência da interface (adesão e ângulo de atrito da interface). O ensaio de laboratório mais adequado para a obtenção desses parâmetros, nestas condições, é o de cisalhamento em plano inclinado ou ensaio de rampa, pois permite simular a condição de campo onde o cisalhamento ocorre em um plano inclinado sob baixas tensões. Assim, este trabalho apresenta um estudo sobre a interação sologeossintético através de ensaios de rampa, executados em um equipamento de grandes dimensões, visando analisar a influência de alguns fatores, tais como, tipo de geossintético, tipo de solo, densidade relativa do solo e tensão confinante. Foram utilizados dois tipos de geossintéticos, uma geomembrana de PVC e uma geogrelha uniaxial e dois tipos de solo, areia e pedregulho (brita). A análise da influência da densidade relativa do solo foi realizada através de ensaios na interface areia-geossintético em duas densidades relativas diferentes (35 e 100%). A influência da tensão confinante foi estudada através de ensaios com três tensões confinantes distintas (2,1; 3,2 e 5,1 kPa). Os resultados mostram que a influência de fatores como densidade relativa do solo, tensão confinante e tipo de solo, dependem do tipo do geossintético. O aumento da densidade relativa do solo promove um acréscimo de resistência na interface para a geogrelha e uma redução para a geomembrana. O aumento da tensão confinante reduz o ângulo de rampa na ruptura, sendo este efeito mais pronunciado na interface areia-geogrelha. Em relação ao tipo de material, a interface brita-geogrelha é a que apresenta maior resistência. / [en] In environmental works, where geosynthetics are used as protection system and of slope covering, it is of extreme importance the knowledge of the interaction mechanism soil-geosynthetic, through the obtaining of the parameters of resistance of the interface (adhesion and interface friction angle). The laboratory test more appropriate for the obtaining of those parameters, in these conditions, is it the inclined plane test or ramp test, because it allows to simulate the field condition where the shearing happens in inclined plane under low tensions. Like this, this work presents a study about the interaction soilgeosynthetic through ramp tests, executed in an equipment of great dimensions seeking to analyze the influence of some factors, such as, geosynthetic type, soil type, relative density of the soil and confinement pressure. Two geosynthetics types, a PVC geomembrane and a uniaxial geogrid, two soil types, it sand and gravel (break). The analysis of the influence of the relative density of the soil was accomplished through tests in the interface sand- geosynthetic in two different relative densities (35 and 100%). The influence of the confinement pressure was studied through tests with three different confinement pressures (2,1; 3,2 and 5,1 kPa). The results show that the influence of factors as relative density of the soil, pressure confinement and soil type, they depend on the type of the geosynthetic. The increase of the relative density of the soil promotes an increment in the interface resistance for the geogrid and a reduction for the geomembrana. The increase of the confinement pressure reduces the ramp angle in the rupture, being this more pronounced effect in the interface sand-geogrid. In relation to the material type, the interface gravel-geogrid presents larger resistance.

The study presented in this thesis discusses the topic of ASRs through the use of a specific case study constructed at Boscombe, UK. With the main aim to provide an impartial and independent study into the environmental, social and economic impacts of an ASR. The research presented is therefore multidisciplinary in nature, the separate components utilise key techniques from the geophysical, numerical modelling and socio-economic disciplines are combined to present a significant contribution to the knowledge and understanding of ASRs. Whilst previous studies have focused on one of these disciplines, there are no independent detailed studies of a constructed ASR utilising an multidisciplinary approach. The ASR concept and structures are still in their development infancy, the subject has received cursory independent review in the literature. There have been few successful projects, those that have survived structurally in the ocean are not being used primarily for surfing. The Boscombe ASR is an example of high overspend, poor management and construction, loss of geotextile SFC and users deem the project a failure. The consequences of not correctly planning, managing and overseeing the construction has resulted in a poorly viewed project of limited success. All stages of this project could have benefited from thoughtful planning, thereby avoiding this outcome. If lessons are to be learnt from this project then the planning and management are key areas of the process that need addressing. Ensuring that any future ASR projects are securely integrated with the coastal zone management plan will provide sustainability and success. The DPSIR framework approach can be used to highlight and address the causes of problems in the project. This framework enables the various disciplines to be discussed in relation to each other; links can be identified between the environmental, social and economic impacts of the ASR construction. Strict protocols will increase the success of any ASR project. The final crest height of the Boscombe ASR was 0.5 m higher than the final design height, this is a fundamental design flaw that should not be occurring in modern coastal engineering practice. It is suggested that guidelines are written based on this research for the design and construction process of an ASR. The recommendations and guidelines for ASR monitoring are provided by this research. The emphasis for future projects should lie in the final design and in monitoring, baseline field data should be collected to understand the environmental state change and socio-economic impacts. Planning and government proposals should be accompanied by extensive stakeholder engagement ensuring transparency for the project and ownership within the coastal community. The exclusion of stakeholders at key decision points created distrust and misunderstanding towards the Boscombe ASR project. Avoiding unrealistic expectations within the surfing community and wider coastal community was discussed throughout this research, and by others in the literature. This research agrees with these statements, the issue of poor surfability would be improved by a greater area to manipulate the bathymetry. However this would come at a greatly increased cost in geotextile SFCs, which the current construction method is certainly not capable of delivering successfully. It would be recommended in this case that an alternative construction material was used that is resilient to the marine environment and readily adaptable given poor performance. Further testing of materials, both geotextile SFCs and alternatives, are required for the successful advancement of ASR technology.

Geosynthetics are used in conjunction with soil/particulate materials to serve various functions like reinforcement, drainage, filtration and containment. The shear behavior of soil-geosynthetic interfaces hugely depends upon on the morphological properties of particulate materials and surface characteristics of geosynthetics. However, many researchers have ignored the effects of morphology, owing to the difficulty in finding the morphological characteristics of sand particles. Few of them used visual, manual and imaged based quantifications, which are not very effective. Also, the effects of particle size and morphology are often combined and the individual effect of these parameters cannot be easily separated. In addition to this, there are very few studies which have given importance to quantitative understanding of surface features/roughness of geosynthetics and almost all of them are limited to 2D surface measurements. The objective of this thesis is to understand the interface shear mechanisms of sand-geosynthetic systems through modified large interface direct shear tests coupled with morphological characterization of sands using advanced image based and optical techniques and surface topographical analysis of geosynthetics using 3D interferometry. The individual effects of particle size and morphology on interface shear mechanism are investigated by carefully selecting the sands having specific size fractions and different morphological characteristics. A new computational method based on image analysis is proposed in this study to quantify the morphology of sands (roundness, sphericity and roughness) more accurately by writing several algorithms and implementing them in MATLAB. The roundness and sphericity of sand particles in this method are quantified as per Wadell (1932) and Krumbein and Sloss (1963) respectively and the root mean square roughness is used as a measure of surface roughness. Out of total four sands, namely coarse sand (CS), medium sand (MS), fine sand (FS) and angular coarse sand (ACS) used in this study, CS, MS and FS have similar morphology and different particle sizes, whereas CS and ACS have same size and dissimilar morphology. The effects of size and morphology of sand particles on the interface shear behavior are examined through direct shear tests on dilative and non-dilative interfaces. After examining the boundary effects on deformation patterns analyzed using shear bands in conventional, fixed box and symmetric interface direct shear tests, symmetric interface direct shear test is observed to show uniformity in stresses and deformations across the shear box and hence the same is adopted in this thesis. Test results revealed that the peak interface friction and dilation angles in case of dilative interfaces are hugely dependent upon the interlocking between the sand particles and the asperities of geosynthetic material, which in turn depend on the relative size of sand particles and asperities. Highest interface shear strength is observed when the asperity size of the geosynthetic material matches with the mean particle size of sand, which is also manifested in terms of highest shear band thickness. Direct shear tests on non-dilative interfaces (sand-smooth geomembrane) revealed that interface friction angle depends on the number of effective contacts rather than the particle size. Morphology of sands is found to have major influence on the interface shear strength among all the parameters investigated. Results from interface shear tests are examined in the light of topographical analysis of sand particles and shear induced surface changes in geomembrane. Possible shearing mechanisms at the interface and the influence of particle size, morphology and normal stress on sliding or plowing are brought out from 3D surface roughness measurements using 3D optical profilometer. The stress-shear displacement response of sand-geomembrane interfaces are correlated to the surface changes on sheared geomembranes through visual observations and roughness quantifications. Medium sand used in this study could make more number of effective contacts with deeper grooves, resulting in highest interface friction. The number of grooves are less in case of coarse sand and the depth of grooves is less in case of fine sand, resulting in lesser interface friction for these two sands compared to medium sand, supporting the results of interface shear tests.