Being able to extrapolate interaction values from a database of pullout resistance testing results may possibly help with narrowing down the most suitable reinforcement/fill material combinations for a Mechanically Stabilized Earth wall, thereby reducing the number of tests needed for a design and maximizing the efficiency of the system. The objectives of this thesis include the following: collect and organize a broad collection of data in a way that can assist in preliminary selection of interaction properties for uniaxial geogrids; analyze the collection of data for trends related to geogrid polymer type; analyze the collection of data for trends related to the presence of fines in the fill material; compare the collected data to previous studies on the effects of geogrid specimen length on pullout performance; and compare the collected data to previous studies on the effect of geogrid rib thickness to mean particle size ratio on normalized bearing stress and CI values. The data from 101 pullout tests are presented in tabular and graphic form so that the coefficient of interaction may be interpolated for many geogrid/fill material combinations. The effect of polymer type (PET vs HDPE) was shown to have little effect on how a geogrid performs in a fill material. In one case, the two polymer types exhibit differing trends within the same fill material. The presence of fines (>12% by weight) in the fill material results in a significant decrease in the coefficient of interaction when compared to clean granular fills. The effects of geogrid embedment length have significant effects on the results of geogrid pullout tests. Samples with shorter lengths were shown to carry a greater load per unit area than longer samples. Normalized bearing stress is shown to be heavily influenced by the geogrid transverse rib thickness to mean particle size ratio (B/D50). For a particular fill material, normalized bearing stress decreases linearly with increasing B/D50. For a particular geogrid, normalized bearing stress is shown to have a bi-linear behavior with increasing B/D50. Initially, normalized bearing stress increases with increasing B/D50. After reaching a peak, normalized bearing stress begins to decrease with increasing B/D50. / text

Geogrids have been used for decades as reinforcement for mechanically stabilized earth retaining walls and base layers of pavements. However, literature on these applications is contradictory regarding the displacement and strain levels at which the bearing mechanism of interaction between soil and geogrid is developed along the transverse ribs of geogrids. No data are available on the deflections and displacement profiles of transverse ribs during loading of geogrids. Field and laboratory data on strain distributions along geogrids are limited. Accordingly, the objective of this study is to better understand the mechanisms of soil-geogrid interaction that develop at different stages of pullout tests, especially at small displacements and strains. Moreover, the behavior of transverse ribs throughout pullout testing is evaluated. Pullout loads were obtained from a load cell synchronized with two 5 MP cameras. Images of the geogrid were analyzed using the Particle Image Velocimetry (PIV) technique to obtain displacement profiles along the entire geogrid specimen throughout the duration of the test. Five transparent pullout tests were conducted using a confining pressure of 35 kPa (5 psi) on polypropylene geogrids with different configurations. Displacements along the polypropylene geogrid used in this study are well represented by an exponential equation. The bearing mechanism along transverse ribs was observed to develop at small viii displacements. The contribution of the bearing mechanism was first observed at 25 % of the maximum pullout force. Interference between transverse ribs was first observed at approximately 60 % of the maximum pullout force. High interference between transverse ribs was observed when the ratio of spacing between transverse ribs (S) over the thickness of the transverse ribs (B) was equal to 24. Negligible interference was observed when S/B was equal to 57. Displacements of soil particles were observed when the ratio distance from the soil-geogrid interface (d) over the D₅₀ of the soil was equal to 3, but they were orders of magnitude smaller than the displacements of the geogrid specimens. The observed boundary of the zone of influence of geogrids was for values of 3 < d/D₅₀ < 7 for the transparent soil used in this study. / text

Pile-supported geogrid-reinforced embankments are an exciting new foundation system that is utilized when sites are limited by a soft soil or clay. In this system, an embankment is supported by a bridging layer, consisting of granular fill and one or multiple layers of geogrid reinforcement. The bridging layer transfers the load to piles that have been driven into the soft soil or clay. The load from the embankment induces large deformations in the geogrid reinforcement, causing tensile forces in the ribs of the geogrid. Many of the current methods used to design geogrid reinforcement for this system simplify the approach by assuming that the reinforcement has a parabolic deformed shape. The purpose of this thesis is to thoroughly examine the behavior of the geogrid in a pile-supported embankment system, in an effort to determine the accuracy of the parabolic deformed shape, and identify the most important parameters that affect reinforcement design. The geogrid was analyzed using a three-dimensional model that included a cable net to represent the geogrid and linear springs to represent the soil underneath the geogrid. A larger pressure was applied to the geogrid regions that are directly above the pile caps so that arching effects could be considered, and the stiffness of the springs on top of the pile were stiffer to account for the thin layer of soil between the geogrid and the pile cap. A Mathematica algorithm was used to solve this model using the minimization of energy method. The results were compared to another model of this system that used a membrane to represent the geosynthetic reinforcement. Additionally, the maximum strain was compared to the strain obtained from a geosynthetic reinforcement design formula. A parametric study was performed using the Mathematica algorithm by varying the pile width, embankment pressure applied to the soil, embankment pressure applied to the pile, stiffness of the soil, stiffness of the soil on top of the pile, stiffness of the geogrid, geogrid orientation, rotational stiffness of the geogrid, and the layers of geogrid reinforcement. / Master of Science

O comportamento de solos reforçados depende amplamente da interação entre o solo e o reforço, baseado nas solicitações que o conjunto experimentará ao longo da sua vida útil. Tal interação é comumente caracterizada através de ensaios normatizados como o de arrancamento, que buscam simular as solicitações a que o conjunto estará sujeito. Porém, algumas estruturas reforçadas experimentam ações cíclicas de cargas móveis consideráveis, que dificilmente tem seu comportamento representado nestes ensaios comuns. Diante disso, esta pesquisa buscou aperfeiçoar o equipamento de ensaios cíclicos da Escola de Engenharia de São Carlos EESC-USP, a fim de realizar ensaios cíclicos em diferentes tipos de solos (uma areia, um silte argiloso e uma brita graduada simples), reforçados com uma geogrelha de poliéster comumente utilizada para reforço de base de pavimentos. Após esta etapa se iniciaram os ensaios de arrancamento nos solos, fornecendo parâmetros para a realização dos ensaios cíclicos. No arrancamento a areia apresentou ganho de resistência com o aumento da tensão confinante, e os maiores deslocamentos, já o silte e a brita não sofreram influência deste aumento. O comportamento cíclico causou desconfinamento da areia e degradação do reforço na brita, apresentando o comportamento mais estável no silte. Durante os ensaios o reforço apresentou grandes deformações conforme solicitado, o que contribuiu para os valores de módulos de resiliência abaixo dos descritos na literatura, que utiliza corpos de prova curtos e diferentes níveis de tensões. Nos ensaios cíclicos a areia variou seu módulo relativamente pouco com as variações de tensão confinante e cisalhante, o silte foi mais sensível à variação da cisalhante e a brita variou igualmente com as duas. / The behavior of reinforced soils depends largely on the interaction between soil and reinforcement, based on requests that the group will experience throughout its service life. Such interaction is commonly characterized by standardized tests such as the pullout, which seek to simulate the stresses to which the group is subject. However, some reinforced structures experience cyclic loads by considerable moving loads, that their behavior is hardly represented in these common tests. Thus, this research sought to improve the equipment of cyclic tests of the School of Engineering of São Carlos EESC-USP, in order to perform cyclic tests on different types of soil (one sand, clayey silt and a simple graded gravel), reinforced with one polyester geogrid commonly used for reinforcing pavements base. After this step began the pullout tests on soils, providing parameters for the realization of the cyclic tests. In the pullout tests, the sand had resistance gain with confining tension increasing and greater displacements, already silt and gravel not affected by this increase. The cyclical behavior caused deconfinement of sand, and the gravel causes degradation of reinforcement, with the more stable behavior on silt. During the test, the reinforce presented large deformations as requested, which contributed to the values of resilience modules below in the literature, which uses specimens shorter and different tension levels. In the cyclic tests the sand modulus varied relatively little with confining pressure and shear variations, the silt was more sensitive to the variation of shear and gravel also varied with both.

Geogrid reinforced structures have been successfully used for over 25 years. However their design procedures have remained largely focused on ultimate failure mechanisms, originally developed for steel reinforcements. These are widely considered over conservative in determining realistic reinforcement and lateral earth stresses. The poor understanding of deformation performance led many design codes to restrict acceptable soils to selected sand and gravel fills, where deformation is not as concerning. Within UK construction there is a drive to reduce wastage, improve efficiency and reduce associated greenhouse gas emissions. For geogrid reinforced structures this could mean increasing reinforcement spacing and reusing weaker locally sourced soils. Both of these strategies increase deformation, raising concern about the lack of understanding and reliable guidance. As a result they fail to fulfil their efficiency potential. This Engineering Doctorate improved the understanding of horizontal deformation by analysing performance using laboratory testing, laser scanning industry structures and numerical modelling. Full-scale models were used to demonstrate a reduction in deformation by decreasing reinforcement spacing. Their results were combined with primary and secondary case studies to create a diverse database. This was used to validate a finite element model, differentiating between two often used construction methods. Its systematic analysis was extended to consider the deformation consequences of using low shear strength granular fills. The observations offered intend to reduce uncertainty and mitigate excessive deformations, which facilitates the further optimisation of designs.

Current design guidelines for reinforced soil walls and slopes recommend the use of granular soils such as gravels and sands as select fills. Cost savings could potentially be realized by using on-site clays and silts. Some clays are swelling and silts are frost susceptible. When considering the use of swelling clays and frost susceptible silts as fills, environmental loading due to swelling-shrinkage and freeze-thaw effects from environmental changes could become a design issue. To examine the hypothesis that consideration of environmental loading during design will produce improvements in the performance of geosynthetic-reinforced soil structures that use clays or silts as fill materials, experimental and numerical studies were undertaken. Geosynthetic-reinforced clay specimens were subjected to wetting and drying in a model test apparatus developed and commissioned for this study. In separate test set-up, reinforced silt specimens were subjected to freezing and thawing. Tests on unreinforced specimens were also performed in otherwise identical conditions for comparison purposes. Movements of the specimens, soil strains, reinforcement strains, soil suctions and soil temperatures were monitored during the application of environmental loading in addition to mechanical loading from external stresses. The results of the laboratory model tests showed that reinforcements reduced horizontal displacements of the clay specimens during wetting and drying. The same is true for the case of silt during freezing and thawing. The environmental loading induced strains, and therefore stresses in the reinforcements. The measured geogrid strain during the wetting-drying of reinforced clay specimen was up to 0.75%. Similarly, the measured geogrid strain in the reinforced silt specimen during freezing-thawing cycles was up to 0.57%. The strains were greater than the strains generated by mechanical loading for the range of applied stresses used in this study. Numerical models were developed to simulate wetting only induced swelling of reinforced clays and freezing only induced expansion of reinforced silts specimens. They were used to simulate the results of laboratory model tests. The performance of geosynthetic-reinforced soil slopes with swelling clay fills and frost susceptible silt fills was evaluated. Parametric studies were performed to determine important parameters affecting the performance of reinforced clay and silt slopes.

Current design guidelines for reinforced soil walls and slopes recommend the use of granular soils such as gravels and sands as select fills. Cost savings could potentially be realized by using on-site clays and silts. Some clays are swelling and silts are frost susceptible. When considering the use of swelling clays and frost susceptible silts as fills, environmental loading due to swelling-shrinkage and freeze-thaw effects from environmental changes could become a design issue. To examine the hypothesis that consideration of environmental loading during design will produce improvements in the performance of geosynthetic-reinforced soil structures that use clays or silts as fill materials, experimental and numerical studies were undertaken. Geosynthetic-reinforced clay specimens were subjected to wetting and drying in a model test apparatus developed and commissioned for this study. In separate test set-up, reinforced silt specimens were subjected to freezing and thawing. Tests on unreinforced specimens were also performed in otherwise identical conditions for comparison purposes. Movements of the specimens, soil strains, reinforcement strains, soil suctions and soil temperatures were monitored during the application of environmental loading in addition to mechanical loading from external stresses. The results of the laboratory model tests showed that reinforcements reduced horizontal displacements of the clay specimens during wetting and drying. The same is true for the case of silt during freezing and thawing. The environmental loading induced strains, and therefore stresses in the reinforcements. The measured geogrid strain during the wetting-drying of reinforced clay specimen was up to 0.75%. Similarly, the measured geogrid strain in the reinforced silt specimen during freezing-thawing cycles was up to 0.57%. The strains were greater than the strains generated by mechanical loading for the range of applied stresses used in this study. Numerical models were developed to simulate wetting only induced swelling of reinforced clays and freezing only induced expansion of reinforced silts specimens. They were used to simulate the results of laboratory model tests. The performance of geosynthetic-reinforced soil slopes with swelling clay fills and frost susceptible silt fills was evaluated. Parametric studies were performed to determine important parameters affecting the performance of reinforced clay and silt slopes.

Since the last three decades, several studies have been conducted related to improvement in bearing capacity of pavements, embankments, and shallow foundations resting on geosynthetic reinforced soil. Most of the work has been carried out on single layer soil e.g., sand or clay layer only. Very few studies are available on a double layer soil system; but no study is available on the local soil of Carbondale, Illinois. The present study investigates the physical and engineering properties of a local soil and commonly available sand and improvement in the bearing capacity of a local soil for a rectangular footing by replacing top of the local soil with sand layer and placing geogrids at different depths. Seven tests on the model footing were performed to establish the load versus settlement curves of unreinforced and reinforced soil supporting a rectangular foundation. The improvement in bearing capacity is compared with the bearing capacity of the local soil and double layer unreinforced soil system. The test results focus on the improvement in bearing capacity of local soil and double layer unreinforced soil system in non-dimensional form i.e., BCR (Bearing Capacity Ratio). The results obtained from the present study show that bearing capacity increases significantly with the increasing number of geogrid layers. The bearing capacity for double layer soil increases, by placing three inch sand layer at the top of local soil, was not significant. The bearing capacity of the local soil increased at an average of 7% with three inches sand layer. The bearing capacity for the double layer soil increases with an average of 16.67% using one geogrid layer at interface of soils (i.e., local soil and sand) with u/B equal to 0.67. The bearing capacity for the double layer soil increases with an average of 33.33% while using one geogrid in middle of sand layer having u/B equal to 0.33. The improvement in bearing capacity for double layer soil maintaining u/B equal to 0.33 and h/B equal to 0.33; for two, three and four number geogrid layer were 44.44%, 61.11%, 72.22%, respectively. The results obtained from this research work may be useful for the specific condition or similar type of soil available anywhere to improve the bearing capacity of soil for foundation and pavement design.

O comportamento de solos reforçados depende amplamente da interação entre o solo e o reforço, baseado nas solicitações que o conjunto experimentará ao longo da sua vida útil. Tal interação é comumente caracterizada através de ensaios normatizados como o de arrancamento, que buscam simular as solicitações a que o conjunto estará sujeito. Porém, algumas estruturas reforçadas experimentam ações cíclicas de cargas móveis consideráveis, que dificilmente tem seu comportamento representado nestes ensaios comuns. Diante disso, esta pesquisa buscou aperfeiçoar o equipamento de ensaios cíclicos da Escola de Engenharia de São Carlos EESC-USP, a fim de realizar ensaios cíclicos em diferentes tipos de solos (uma areia, um silte argiloso e uma brita graduada simples), reforçados com uma geogrelha de poliéster comumente utilizada para reforço de base de pavimentos. Após esta etapa se iniciaram os ensaios de arrancamento nos solos, fornecendo parâmetros para a realização dos ensaios cíclicos. No arrancamento a areia apresentou ganho de resistência com o aumento da tensão confinante, e os maiores deslocamentos, já o silte e a brita não sofreram influência deste aumento. O comportamento cíclico causou desconfinamento da areia e degradação do reforço na brita, apresentando o comportamento mais estável no silte. Durante os ensaios o reforço apresentou grandes deformações conforme solicitado, o que contribuiu para os valores de módulos de resiliência abaixo dos descritos na literatura, que utiliza corpos de prova curtos e diferentes níveis de tensões. Nos ensaios cíclicos a areia variou seu módulo relativamente pouco com as variações de tensão confinante e cisalhante, o silte foi mais sensível à variação da cisalhante e a brita variou igualmente com as duas. / The behavior of reinforced soils depends largely on the interaction between soil and reinforcement, based on requests that the group will experience throughout its service life. Such interaction is commonly characterized by standardized tests such as the pullout, which seek to simulate the stresses to which the group is subject. However, some reinforced structures experience cyclic loads by considerable moving loads, that their behavior is hardly represented in these common tests. Thus, this research sought to improve the equipment of cyclic tests of the School of Engineering of São Carlos EESC-USP, in order to perform cyclic tests on different types of soil (one sand, clayey silt and a simple graded gravel), reinforced with one polyester geogrid commonly used for reinforcing pavements base. After this step began the pullout tests on soils, providing parameters for the realization of the cyclic tests. In the pullout tests, the sand had resistance gain with confining tension increasing and greater displacements, already silt and gravel not affected by this increase. The cyclical behavior caused deconfinement of sand, and the gravel causes degradation of reinforcement, with the more stable behavior on silt. During the test, the reinforce presented large deformations as requested, which contributed to the values of resilience modules below in the literature, which uses specimens shorter and different tension levels. In the cyclic tests the sand modulus varied relatively little with confining pressure and shear variations, the silt was more sensitive to the variation of shear and gravel also varied with both.

Submitted by Geyciane Santos (geyciane_thamires@hotmail.com) on 2015-09-30T14:50:43Z No. of bitstreams: 1 Dissertação - Evailton Arantes de Oliveira.pdf: 7555305 bytes, checksum: 2c240f5c22ffe712c469fdbb9709b393 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-09T13:28:31Z (GMT) No. of bitstreams: 1 Dissertação - Evailton Arantes de Oliveira.pdf: 7555305 bytes, checksum: 2c240f5c22ffe712c469fdbb9709b393 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-09T13:37:06Z (GMT) No. of bitstreams: 1 Dissertação - Evailton Arantes de Oliveira.pdf: 7555305 bytes, checksum: 2c240f5c22ffe712c469fdbb9709b393 (MD5) / Made available in DSpace on 2015-10-09T13:37:06Z (GMT). No. of bitstreams: 1 Dissertação - Evailton Arantes de Oliveira.pdf: 7555305 bytes, checksum: 2c240f5c22ffe712c469fdbb9709b393 (MD5) Previous issue date: 2014-05-02 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work aims at the realization of geogrid pullout tests in a typical soil of the city of Manaus, using a small laboratory equipment. The soil in natura used in the tests was collected within an Area of Permanent Protection (APP) at the Federal University of Amazonas campus, representing a wide area of topsoil from the city of Manaus, the clayeysilty- sandy composition. From the original sample mixture with the addition of 20%, 40% and 60% sand deposit by mass were prepared. The soil samples and mixtures were characterized by the writings of Grit, Real Density, Liquid Limit, Limit Plasticity, Compression (Standard Proctor), California Support Index (CSI) and Triaxial Compression. Subsequently, tensile testing of Tensar geogrids in pullout of small laboratory equipment, experimental in nature, in which they varied the type of soil were performed, aiming a comparison with the manufacturer's specifications, and the test speed and type geogrid. During the research, a computer program was developed to facilitate statistical analysis of the results of pullout tests and enable the design of reinforced embankments with geogrids. Those tests proved that the insertion of the geogrid coupled to sanding, the original soil increments the geotechnical performance of the assembly, opposite the pullout requests, in which the mixture of 60% sand that best represents the quality of the strength parameters for reinforced embankments. / Este trabalho visa à realização de ensaios de arrancamento de geogrelha em um solo típico da cidade de Manaus, utilizando um equipamento reduzido de laboratório. O solo in natura utilizado nos ensaios foi coletado dentro de uma Área de Proteção Permanente (APP), no campus da Universidade Federal do Amazonas, representando um solo superficial de vasta área da cidade de Manaus, de composição argilo-silto-arenosa. A partir da amostra original, foram confeccionadas misturas com a adição de 20%, 40% e 60% de areia de jazida, em massa. As amostras de solo e misturas foram caracterizadas através dos ensaios de Granulometria, Densidade Real, Limite de Liquidez, Limite de Plasticidade, Compactação (Proctor Normal), Índice de Suporte Califórnia (ISC) e Compressão Triaxial. Posteriormente, foram realizados ensaios de tração das geogrelhas, visando um comparativo com as especificações do fabricante, e ensaios de arrancamento das geogrelhas em um equipamento reduzido de laboratório, de cunho experimental, em que se variou o tipo de solo, a velocidade do ensaio e o tipo de geogrelha. Durante a pesquisa, um programa computacional foi desenvolvido, para facilitar a análise estatística dos resultados dos ensaios de arrancamento e possibilitar o dimensionamento de taludes reforçados com geogrelhas. Esses ensaios comprovaram que a inserção da geogrelha, aliada à aplicação de areia, ao solo original, incrementa o desempenho geotécnico do conjunto, frente às solicitações de arrancamento, sendo a mistura com 60% de areia a que melhor representa a qualidade dos parâmetros de resistência, para os taludes reforçados.