O módulo de resiliência é uma propriedade mecânica dos solos indispensável para análise estrutural de pavimentos em termos de tensão e deformação. O principal ensaio laboratorial para estimativa do módulo de resiliência dos solos é o ensaio triaxial cíclico no qual existe um maior controle das condições da amostra, dos carregamentos aplicados e dos deslocamentos medidos. A utilização de relações para obtenção do módulo de resiliência a partir de propriedades do solo obtidas de ensaios mais simples e rotineiros é permitida pelo procedimento NCHRP 1-37A (2004) e pode ser muito útil para fase de anteprojeto de implantação de rodovias, pois permite uma avaliação rápida do módulo de resiliência dos solos de jazidas e subleitos, localizados ao longo das diversas alternativas de traçados a serem analisadas. No entanto, as relações existentes ou são restritivas, por não considerarem os solos das regiões tropicais de comportamento laterítico e não laterítico da classificação MCT (Miniatura Compactado Tropical), ou são de baixa eficiência. Considerando-se o sucesso que as redes neurais artificiais (RNAs) têm apresentado no campo da engenharia em estabelecer relações entre variáveis explicativas e variáveis resposta, neste trabalho foram desenvolvidas RNAs para relacionar o módulo de resiliência com as propriedades do solo, tanto para solos grossos compactados na energia modificada como para solos compactados na energia normal. O banco de dados utilizado no trabalho baseou-se nos resultados de ensaios de setenta e seis amostras de solos coletadas no interior do Estado de São Paulo. Finalmente, verificou-se que as RNAs podem prever, com alta eficiência, o módulo de resiliência dos solos tropicais de comportamento laterítico e não laterítico a partir de propriedades do solo tais como: composição granulométrica, LL, IP, umidade ótima e resultados do ensaio de compressão simples. / The resilient modulus is an essential mechanical property for stress-strain analysis of pavements. The main test to evaluate resilient modulus of soils is cyclic triaxial test which there is a better control not only of samples but also of loads and displacements. Nowadays, the utilization of relationships to obtain resilient modulus from soils properties, from routine simple tests, is allowed by procedure NCHRP 1-37A, and that can be useful in initial design in construction of roads, as the resilient modulus of material pits and subgrades, places along several alternative traces of design, can be evaluated very fast by relationships. However, the existing relationships are restrictive, because they do not consider tropical soils of lateritic and non-lateritic behavior from MCT (Miniatura Compactado Tropical) classification and they have low performance. Artificial neural networks (ANNs) have shown high success to establish relationships from answering variables and explicative variables, so in this work was developed ANNs to establish relationships from resilient modulus and soil properties, not only for sandy soils in Proctor\'s modified compaction energy but also for soils in Proctor\'s standard compaction energy. The data base used in this work was laboratory test results from seventy-six soils which were collected in interior of Sao Paulo state. Finally, for tropical soils of lateritic and non-lateritic behavior, it was verified that ANNs can forecast, with high performance, resilient modulus from soil properties just as: grain size composition, liquid limit (LL), plasticity index (PI), optimum moisture content and results of simple strength compressive test.

Made available in DSpace on 2015-03-26T13:28:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3121914 bytes, checksum: 0c62051de638282573a48ac248e569a2 (MD5) Previous issue date: 2006-08-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work was intended to verify the behavior of a silt sandy tailings sample subjected to dynamic loadings. Shear stress cycles are applied during cyclic triaxial tests over a soil specimen which leads to liquefaction by the increase of generated porepressure. The studies to determine the liquefaction potential of a tailings sample from a typical mining plant was carried out by a series of undrained isotropically consolidated triaxial tests (CKU), of common use for liquefaction potential evaluation of silts and sands, as well as cyclic triaxial tests, which have not yet much used in Brazil although they are recognized around the world by geotechnical community for such liquefaction potential study. Test results obtained from performed tests with static and dynamic loading have shown that the presence of silt somehow inhibited the liquefaction of tested tailings sample. Taking into account the complexity of performing cyclic triaxial tests, the cyclic triaxial device of Civil Engineering Laboratory (LEC/UFV) has proved to be very efficient for tests under dynamic loading, nevertheless test techniques needs some improvements and adaptations concerning testing device and specially regarding specimen preparation. / Este trabalho tem por objetivo analisar o comportamento de um material silto-arenoso quando submetido a carregamentos dinâmicos. Durante o ensaio triaxial cíclico são aplicados ciclos de tensões cisalhantes em uma amostra que elevam os níveis da poro pressão e induz o solo a se liquefazer. Os estudos para determinar o potencial de liquefação de uma mistura de rejeitos de mineração foram realizados ensaios triaxiais do tipo consolidados anisotropicamente não-drenados (CKU), ensaios estes já consagrados no estudo do potencial de liquefação de areias e siltes, e também ensaios triaxiais cíclicos, que apesar de ainda não serem difundidos no Brasil, já tiveram sua eficácia comprovada através de diversos estudos realizados por todo o mundo. Os resulttados obtidos dos ensaios realizados com carregamentos estáticos e cíclicos mostraram que a presença de silte inibiu a liquefação dos rejeitos ensaiados. Considerando a complexidade envolvendo a realização de ensaios triaxiais cíclicos, o equipamento triaxial cíclico do Laboratório de Engenharia Civil (LEC/UFV) mostrou-se eficaz para a realização de ensaios com carregamentos dinâmicos, no entanto a técnica de ensaio necessita certos ajustes tanto no que concerne ao equipamento quanto às técnicas de moldagem de amostras.

O módulo de resiliência é uma propriedade mecânica dos solos indispensável para análise estrutural de pavimentos em termos de tensão e deformação. O principal ensaio laboratorial para estimativa do módulo de resiliência dos solos é o ensaio triaxial cíclico no qual existe um maior controle das condições da amostra, dos carregamentos aplicados e dos deslocamentos medidos. A utilização de relações para obtenção do módulo de resiliência a partir de propriedades do solo obtidas de ensaios mais simples e rotineiros é permitida pelo procedimento NCHRP 1-37A (2004) e pode ser muito útil para fase de anteprojeto de implantação de rodovias, pois permite uma avaliação rápida do módulo de resiliência dos solos de jazidas e subleitos, localizados ao longo das diversas alternativas de traçados a serem analisadas. No entanto, as relações existentes ou são restritivas, por não considerarem os solos das regiões tropicais de comportamento laterítico e não laterítico da classificação MCT (Miniatura Compactado Tropical), ou são de baixa eficiência. Considerando-se o sucesso que as redes neurais artificiais (RNAs) têm apresentado no campo da engenharia em estabelecer relações entre variáveis explicativas e variáveis resposta, neste trabalho foram desenvolvidas RNAs para relacionar o módulo de resiliência com as propriedades do solo, tanto para solos grossos compactados na energia modificada como para solos compactados na energia normal. O banco de dados utilizado no trabalho baseou-se nos resultados de ensaios de setenta e seis amostras de solos coletadas no interior do Estado de São Paulo. Finalmente, verificou-se que as RNAs podem prever, com alta eficiência, o módulo de resiliência dos solos tropicais de comportamento laterítico e não laterítico a partir de propriedades do solo tais como: composição granulométrica, LL, IP, umidade ótima e resultados do ensaio de compressão simples. / The resilient modulus is an essential mechanical property for stress-strain analysis of pavements. The main test to evaluate resilient modulus of soils is cyclic triaxial test which there is a better control not only of samples but also of loads and displacements. Nowadays, the utilization of relationships to obtain resilient modulus from soils properties, from routine simple tests, is allowed by procedure NCHRP 1-37A, and that can be useful in initial design in construction of roads, as the resilient modulus of material pits and subgrades, places along several alternative traces of design, can be evaluated very fast by relationships. However, the existing relationships are restrictive, because they do not consider tropical soils of lateritic and non-lateritic behavior from MCT (Miniatura Compactado Tropical) classification and they have low performance. Artificial neural networks (ANNs) have shown high success to establish relationships from answering variables and explicative variables, so in this work was developed ANNs to establish relationships from resilient modulus and soil properties, not only for sandy soils in Proctor\'s modified compaction energy but also for soils in Proctor\'s standard compaction energy. The data base used in this work was laboratory test results from seventy-six soils which were collected in interior of Sao Paulo state. Finally, for tropical soils of lateritic and non-lateritic behavior, it was verified that ANNs can forecast, with high performance, resilient modulus from soil properties just as: grain size composition, liquid limit (LL), plasticity index (PI), optimum moisture content and results of simple strength compressive test.

O objetivo deste trabalho é avaliar a influência da variação do teor de umidade no valor do módulo de resiliência (MR) de um solo argiloso de subleito, tendo em vista que este parâmetro é muito susceptível à variações climáticas ambientais. Foram realizados ensaios triaxiais cíclicos para se estimar o módulo de resiliência de corpos de prova ensaiados em diversas condições de umidade. Verificou-se que o MR é influenciado pela tensão desvio, de forma que aquele aumenta com o acréscimo desta. Constatou-se que os corpos de prova moldados na Wot e submetidos a trajetórias de secagem e umedecimento alcançaram valores de MR superiores e inferiores, respectivamente, ao se comparar com o MR de corpos de prova ensaiados na Wot. Este fato foi também observado para os corpos de prova moldados com massa específica seca máxima, em teores de umidade abaixo e acima do teor ótimo. Determinou-se, ainda, a sucção no solo através do método do papel filtro e levantou-se a sua curva característica. Verificou-se que à medida que a umidade aumenta, a sucção diminui. Observou-se que o valor do MR aumenta com o aumento da sucção no solo. Este crescimento é tanto maior quanto maior seja a tensão desvio aplicada. Foi possível determinar a relação entre o MR, a tensão desvio e o módulo tangente inicial (Eo), proveniente dos ensaios de compressão simples. Relacionou-se, também, o Eo e a sucção no solo. / The aim of this work is to evaluate the influence of moisture content variation in resilient modulus value (MR) of a subgrade clayey soil, considering that this parameter is very susceptible to environmental climatic variations. Cyclic triaxial tests were performed to acess resilient modulus of specimens tested in several moisture conditions. lt has been verified that MR is influenced by deviator stress, so that the former increases with the latter increases. lt has been confirmed that specimens molded in Wot and submited to a drying and moistening route reached MR values higher and lower, respectively, to compare with MR of specimens tested in Wot. This fact was also observed for the specimens molded with dry density, in moisture contents below and above of optimum moisture content. lt has been also determined the soil suction using filter paper method and it has been built its characteristic curve. lt has been verified that when moisture increases, the suction decreases. lt has been observed that MR value increases with the soil suction increase. This increase is as bigger as bigger the applied deviator stress be. lt was possible to determine the relationship between MR, deviator stress and parameters from compressive strength tests. lt has been related parameters from compressive strength tests and soil suction.

Na construção de rodovias, as condições de umidade e densidade observadas na compactação são, geralmente, próximas daquelas correspondentes ao pico da curva de compactação obtida no ensaio Proctor. É sabido que variações ambientais no decorrer da vida do pavimento podem alterar, de maneira significativa, a umidade do subleito e dos seus componentes e assim, as suas propriedades resilientes. O objetivo principal desta pesquisa é avaliar a influência da variação da umidade pós-compactação no módulo de resiliência de solos de rodovias do interior paulista a partir de resultados de ensaios de laboratório. Foram coletados e caracterizados setenta e três solos, e, dentre estes, selecionados trinta para a etapa de estudo da variação da umidade pós-compactação, após a realização de ensaios MCT, difração de raios-x, microscopia eletrônica de varredura e azul de metileno para determinação da gênese. Os solos selecionados apresentam características distintas quanto à gênese, sendo metade laterítico e metade não-laterítico. Os corpos-de-prova foram compactados na umidade ótima e submetidos a processos de secagem e umedecimento e, posteriormente, realizados ensaios triaxiais cíclicos. Os resultados permitiram a modelagem do 'M IND.R' em função do estado de tensão para diferentes umidades e a avaliação da competência de alguns modelos matemáticos nesta representação. Estudou-se a influência da gênese e da granulometria sobre o valor do 'M IND.R' e avaliou-se a conseqüência da variação da umidade sobre este para solos lateríticos e não-lateríticos. Determinou-se uma expressão para estimar a variação do 'M IND.R' com a variação da umidade a partir do parâmetro k1, independentemente do estado de tensão. Pesquisou-se a existência de relações entre os parâmetros de regressão do modelo composto e os resultados dos ensaios de compressão simples e as propriedades físicas dos solos, de forma a permitir a estimativa do módulo de resiliência a partir do resultado de ensaios mais simples. Investigou-se a possibilidade de se utilizar as relações entre a variação do módulo tangente inicial com a variação da umidade para estimar os efeitos sobre o 'M IND.R'. / On road construction, the field compaction conditions are usually close to those determined from Proctor tests. Environmental variations may lead to changes in the pavement moisture and also changing its resilient properties. The main objective of this research is to study the influence of post-compaction moisture content variation on the resilient modulus of soils from São Paulo state pavements, using laboratory tests. To accomplish this objective, seventy three soils samples were collected and characterized. Among them, thirty samples were selected, after four different tests were carried out to determine the soils genesis, to study the post-compaction moisture content variation. Half of these selected soils are lateritic ones, and the other half are non-lateritic soils. The specimens were compacted at optimum moisture content and submitted to drying and moistening processes prior cyclic triaxial test to be carried out. The results allowed the resilient modulus modeling as a function at the stress state and the performance evaluation of five different models. The genesis and grain size distribution influence on the resilient modulus values were studied. The effects of moisture content variations on lateritic and non-lateritic soils were investigated. An expression to estimate the resilient modulus variations with the moisture variations was determined, independently of the stress state. The existence of relations of the compound model regression parameters with the results of unconfined compressive strength and soil properties were studied. The possibility of using the initial tangent modulus variations with the moisture variations to estimate the effects on the resilient modulus were also investigated.

This thesis deals with compares the procedures carried out in the cyclical load triaxial testing device according to CSN EN 13286-7, and the procedures performed in the United States of America. In the practical part elasticity moduls of mixed recycled material are experimentally compared with mixed recycled material containing binder(connective material) and with fine-grained soil in the cyclical load triaxial testing device. Further the thesis assesses the use of mixed recycled material in the construction of a third class low-load pavement.

This thesis presents the results of a series of undrained cyclic triaxial tests carried out on four lime-cement stabilized specimens and clay specimen. The shear resistance degradation rate of lime-cement column subjected to cyclic loading simulated from heavy truck was investigated based on stress-controlled test. The influence of lime and cement on the degradation rate was investigated by comparing the behavior of stabilized kaolin and unstabilized kaolin with similar initial condition. The results indicate an increase in degree of degradation as the number of loading cycles and cyclic strain increase. It is observed that the degradation index has approximately a parabolic relationship with the number of cycles. Generally adding lime and cement to the clay will increase the degradation index which means lower degree of degradation. The degradation parameter, t has a hyperbolic relationship with shear strain, but it loses its hyperbolic shape as the soil getting stronger. On the other hand, for unstabilized clay an approximate linear relationship between degradation index and number of cycles was observed and the degradation parameter has a hyperbolic shape with the increase number of cycles. It was also observed that the stronger the material was, the lesser pore pressure developed in the lime-cement stabilized clay.

O avanço das técnicas de melhoramento de solos vem permitindo o aproveitamento de locais nos quais, até pouco tempo atrás, era considerada a construção de muitas estruturas como inviáveis, seja técnica, financeira ou ambientalmente. Uma das técnicas que tem conseguido demostrar bons resultados é o reforço com fibras de diferentes origens, com ou sem presença de algum agente cimentante. A maioria dos estudos conduzidos sobre este tipo de materiais se têm centrado na caracterização dos materiais sob cargas estáticas, e outros estudos se limitam a avaliar o comportamento sob cargas cíclicas destes materiais para densidades relativas baixas, nas quais o fenômeno de liquefação governa o mecanismo de ruptura. O presente estudo tenta aprofundar no conhecimento sobre materiais compactos quando submetidos a carregamentos cíclicos, de maneira a fornecer insumos para o estudo deste campo. O estudo, de caráter experimental, foi feito através da caracterização de corpos de prova de areia e areia com 0,5% de fibras, além da consideração de dois índices de vazios: o primeiro de 0,63 (correspondente a uma densidade relativa de 90%), e o segundo com um índice de vazios igual a 0,75 (correspondente a uma densidade relativa de 50%) Foram executados 29 ensaios triaxiais, além da adoção dos valores de outros 15 feitos por outro autor, totalizando 44 ensaios. A totalidade dos ensaios divide-se assim: 12 ensaios monotônicos CID, 12 ensaios monotônicos CIU, e 20 ensaios cíclicos CIU sob tensão controlada. Nos ensaios monotônicos obtiveram-se incrementos no ângulo de atrito do material composto, sendo mais evidente para as amostras compactas. Em relação aos ensaios cíclicos, obteve-se incrementos nas resistência do material até atingir sua condição de ruptura, seja por liquefação em amostras pouco compactas (Dr= 50%), ou por mobilidade cíclica no caso de amostras compactas (Dr= 90%). A normalização dos resultados permitiu observar que, embora as fibras melhorem o desempenho das misturas quando submetidas a carregamentos cíclicos, não alteraram a estrutura do material em sua resposta em termos de módulo de elasticidade, pelo menos no que respeita a níveis de deformações medianos a grandes. Para pequenas deformações, evidenciou-se uma diminuição na rigidez das amostras, ocasionando assim maiores acréscimos de poropressão nos estágios iniciais dos ensaios, mais nas em areias com fibras do que sem elas. / The development of ground improvement techniques has allowed the use of certain places, which was in the past considered as non-viable for the construction of many types of structures. Fiber reinforced soils have shown good results, with or without presence of any cementitious agent. The focus of most studies performed on this type of materials, is the characterization under static loading, and other studies are limited to evaluating its behavior on cyclic loading at low level of relative density, in which cases the liquefaction phenomenon governs the mechanism of rupture. This study aims to improve the knowledge of cyclic loading effects in dense materials. Was carried out an experimental program by characterizing specimens of sand with 0% and 0.5% of randomly distributed fiber, considering two void ratios: 0.63 (dense sand, Dr = 90%) and 0.75 (moderately loose sand, Dr = 50%). In total, were performed 29 triaxial tests, in addition of another 15 executed by another author, totaling 44 The test were divided as follows: 12 monotonic CIU test, 12 monotonic CID test, and 20 CIU loading controlled cyclic test. In monotonic conditions, fibers addition increases the friction angle, mostly on dense samples (Dr = 90%) than on loose specimens (Dr = 50%). For cyclic tests, in both materials, fiber additions causes improvement on cyclic behavior, but with different failure mechanism, liquefaction for loose, and cyclic mobility for dense sands, regardless of the presence of fibers. The transformation of the number of cycles axis, or normalization of another cyclic results allowed observing that, despite the fiber addition can cause improvement of materials subjected to cyclic loading, the structure of the material did not change in elasticity modulus response, at least for medium to large strains levels. For small strains, occur a decrease in the stiffness of samples, causing greater increases of pore pressure in the initial stages of tests, more in reinforced sand than for none reinforced condition. / El avance de las técnicas para mejoramiento de suelos ha permitido el aprovechamiento de sitios en los cuales, hasta hace poco tiempo, se consideraba como no viable la construcción de muchas estructuras, sea por cuestiones técnicas, financieras o ambientales. Una técnica que ha demostrado buenos resultados es la incorporación de refuerzos con fibras de diferente origen, considerando o no la presencia de algún agente cementante. La mayoría de los estudios realizados a este tipo de materiales se han centrado en la caracterización bajo la acción de cargas estáticas, e otros se han limitado a evaluar el comportamiento bajo la acción de cargas cíclicas considerando únicamente densidades relativas bajas, para las cuales la ruptura está controlada por el fenómeno de licuación. El presente estudio busca ahondar en el conocimiento sobre el comportamiento bajo acción de cargas cíclicas de materiales compactos, buscando con ello ampliar la base experimental sobre este campo. El estudio, de carácter experimental, fue realizado a partir de la caracterización de especímenes de arena sin fibras y con 0,5% de fibras, además de la consideración de dos relaciones de vacíos: 0.63 (correspondiente a una densidad relativa de 90%), y 0,75 (correspondiente a una densidad relativa de 50%) Fueron realizados 29 ensayos triaxiales, además de haber adoptado los resultados de otros 15 realizados por otro autor, totalizando 44 ensayos. Los ensayos fueron divididos así: 12 ensayos monotónicos CID, 12 ensayos monotónicos CIU, y 20 ensayos triaxiales cíclicos CID con control de esfuerzos. En los ensayos monotónicos fueron obtenidos incrementos en el ángulo de fricción del material compuesto, siendo esta situación más evidente en muestras compactas. Con relación a los ensayos cíclicos, se obtuvo incremento en la resistencia de las muestras hasta alcanzar su condición de ruptura, bien sea por licuación (materiales relativamente sueltos, Dr = 50%), o por movilidad cíclica (materiales compactos, Dr = 90%). La normalización de los resultados permitió observar que, aunque las fibras mejoran el desempeño bajo cargas cíclicas de los materiales, no alteraron la estructura del material en términos de módulo de elasticidad, por lo menos para niveles medios y altos de deformación. Para pequeñas deformaciones, se evidenció una disminución en la rigidez de las muestras, lo que produjo mayores incrementos en las presiones de poros durante las fases iniciales de los ensayos, con mayor visibilidad en las arenas con fibras que cuando no hubo adición.

O avanço das técnicas de melhoramento de solos vem permitindo o aproveitamento de locais nos quais, até pouco tempo atrás, era considerada a construção de muitas estruturas como inviáveis, seja técnica, financeira ou ambientalmente. Uma das técnicas que tem conseguido demostrar bons resultados é o reforço com fibras de diferentes origens, com ou sem presença de algum agente cimentante. A maioria dos estudos conduzidos sobre este tipo de materiais se têm centrado na caracterização dos materiais sob cargas estáticas, e outros estudos se limitam a avaliar o comportamento sob cargas cíclicas destes materiais para densidades relativas baixas, nas quais o fenômeno de liquefação governa o mecanismo de ruptura. O presente estudo tenta aprofundar no conhecimento sobre materiais compactos quando submetidos a carregamentos cíclicos, de maneira a fornecer insumos para o estudo deste campo. O estudo, de caráter experimental, foi feito através da caracterização de corpos de prova de areia e areia com 0,5% de fibras, além da consideração de dois índices de vazios: o primeiro de 0,63 (correspondente a uma densidade relativa de 90%), e o segundo com um índice de vazios igual a 0,75 (correspondente a uma densidade relativa de 50%) Foram executados 29 ensaios triaxiais, além da adoção dos valores de outros 15 feitos por outro autor, totalizando 44 ensaios. A totalidade dos ensaios divide-se assim: 12 ensaios monotônicos CID, 12 ensaios monotônicos CIU, e 20 ensaios cíclicos CIU sob tensão controlada. Nos ensaios monotônicos obtiveram-se incrementos no ângulo de atrito do material composto, sendo mais evidente para as amostras compactas. Em relação aos ensaios cíclicos, obteve-se incrementos nas resistência do material até atingir sua condição de ruptura, seja por liquefação em amostras pouco compactas (Dr= 50%), ou por mobilidade cíclica no caso de amostras compactas (Dr= 90%). A normalização dos resultados permitiu observar que, embora as fibras melhorem o desempenho das misturas quando submetidas a carregamentos cíclicos, não alteraram a estrutura do material em sua resposta em termos de módulo de elasticidade, pelo menos no que respeita a níveis de deformações medianos a grandes. Para pequenas deformações, evidenciou-se uma diminuição na rigidez das amostras, ocasionando assim maiores acréscimos de poropressão nos estágios iniciais dos ensaios, mais nas em areias com fibras do que sem elas. / The development of ground improvement techniques has allowed the use of certain places, which was in the past considered as non-viable for the construction of many types of structures. Fiber reinforced soils have shown good results, with or without presence of any cementitious agent. The focus of most studies performed on this type of materials, is the characterization under static loading, and other studies are limited to evaluating its behavior on cyclic loading at low level of relative density, in which cases the liquefaction phenomenon governs the mechanism of rupture. This study aims to improve the knowledge of cyclic loading effects in dense materials. Was carried out an experimental program by characterizing specimens of sand with 0% and 0.5% of randomly distributed fiber, considering two void ratios: 0.63 (dense sand, Dr = 90%) and 0.75 (moderately loose sand, Dr = 50%). In total, were performed 29 triaxial tests, in addition of another 15 executed by another author, totaling 44 The test were divided as follows: 12 monotonic CIU test, 12 monotonic CID test, and 20 CIU loading controlled cyclic test. In monotonic conditions, fibers addition increases the friction angle, mostly on dense samples (Dr = 90%) than on loose specimens (Dr = 50%). For cyclic tests, in both materials, fiber additions causes improvement on cyclic behavior, but with different failure mechanism, liquefaction for loose, and cyclic mobility for dense sands, regardless of the presence of fibers. The transformation of the number of cycles axis, or normalization of another cyclic results allowed observing that, despite the fiber addition can cause improvement of materials subjected to cyclic loading, the structure of the material did not change in elasticity modulus response, at least for medium to large strains levels. For small strains, occur a decrease in the stiffness of samples, causing greater increases of pore pressure in the initial stages of tests, more in reinforced sand than for none reinforced condition. / El avance de las técnicas para mejoramiento de suelos ha permitido el aprovechamiento de sitios en los cuales, hasta hace poco tiempo, se consideraba como no viable la construcción de muchas estructuras, sea por cuestiones técnicas, financieras o ambientales. Una técnica que ha demostrado buenos resultados es la incorporación de refuerzos con fibras de diferente origen, considerando o no la presencia de algún agente cementante. La mayoría de los estudios realizados a este tipo de materiales se han centrado en la caracterización bajo la acción de cargas estáticas, e otros se han limitado a evaluar el comportamiento bajo la acción de cargas cíclicas considerando únicamente densidades relativas bajas, para las cuales la ruptura está controlada por el fenómeno de licuación. El presente estudio busca ahondar en el conocimiento sobre el comportamiento bajo acción de cargas cíclicas de materiales compactos, buscando con ello ampliar la base experimental sobre este campo. El estudio, de carácter experimental, fue realizado a partir de la caracterización de especímenes de arena sin fibras y con 0,5% de fibras, además de la consideración de dos relaciones de vacíos: 0.63 (correspondiente a una densidad relativa de 90%), y 0,75 (correspondiente a una densidad relativa de 50%) Fueron realizados 29 ensayos triaxiales, además de haber adoptado los resultados de otros 15 realizados por otro autor, totalizando 44 ensayos. Los ensayos fueron divididos así: 12 ensayos monotónicos CID, 12 ensayos monotónicos CIU, y 20 ensayos triaxiales cíclicos CID con control de esfuerzos. En los ensayos monotónicos fueron obtenidos incrementos en el ángulo de fricción del material compuesto, siendo esta situación más evidente en muestras compactas. Con relación a los ensayos cíclicos, se obtuvo incremento en la resistencia de las muestras hasta alcanzar su condición de ruptura, bien sea por licuación (materiales relativamente sueltos, Dr = 50%), o por movilidad cíclica (materiales compactos, Dr = 90%). La normalización de los resultados permitió observar que, aunque las fibras mejoran el desempeño bajo cargas cíclicas de los materiales, no alteraron la estructura del material en términos de módulo de elasticidad, por lo menos para niveles medios y altos de deformación. Para pequeñas deformaciones, se evidenció una disminución en la rigidez de las muestras, lo que produjo mayores incrementos en las presiones de poros durante las fases iniciales de los ensayos, con mayor visibilidad en las arenas con fibras que cuando no hubo adición.

Key factors that influence the design of paved and unpaved roads are the strength and stiffness of the pavement layers. Among other factors, the strength of pavements depends on the thickness and quality of the aggregates used in the pavement base layer. In India and many other countries, there is a high demand for good quality aggregates and the availability of aggregate resources is limited. There is a need for the development of sustainable construction methods which can handle aggregate requirements with least available resources and provide good performance. Hence it is imperative to strive for alternatives to achieve improved quality of pavements using supplementary potential materials and methods. The strength of pavement increases with increase in the thickness of the base which has a direct implication on construction cost whereas decreasing the thickness of the base makes it weak which results in low load bearing capacity especially for unpaved roads. The use of different types of geosynthetics like geocell and geogrid are a potential and reliable solution for the lack of availability of aggregates and studies are conducted in this direction. To better understand the performance of any geosynthetically reinforced base layers, it is essential to characterize the pavement material by studying the behavior of these materials under static as well as repeated loading. For unpaved roads, the base layer, made of granular aggregates plays a crucial role in the reduction of permanent deformation of the pavements. The resilient modulus (Mr) of these materials is a key parameter for predicting the structural response of pavements and for characterizing materials in pavement design and evaluation. Usually, during the design of flexible pavements, pavement materials are treated as homogeneous and isotropic. The use of rollers in the field during pavement construction leads to a higher compaction of material in the vertical direction which introduces stress-induced anisotropy in the base material. The effect of stress-induced anisotropy on the properties of the granular material is studied and discussed in the first part of the research by conducting repeated load triaxial tests. Isotropic consolidated and anisotropically consolidated samples were prepared to investigate the behavior of base materials under stress induced anisotropic conditions. An additional axial load was applied on the isotropically consolidated sample to create anisotropically consolidated sample. The axial loading was provided such that the stress ratio (σ1/σ3), during anisotropic consolidation was kept constant for all the tests at different confining pressures. The effect of repeated loading on the permanent deformation and the resilient modulus for both isotropically and anisotropically consolidated samples, at different confining pressure and loading conditions, are discussed. The behavior of both anisotropically and isotropically consolidated samples has been explained using the record of the excess pore pressures generated during the experiments. The experimental studies show that the permanent strains measured in the vertical direction of the anisotropically consolidated samples are less compared to the results obtained for isotropically consolidated samples. The resilient moduli of the anisotropically consolidated samples were also observed to be higher than that of the isotropically consolidated sample. The study conducted on the pore pressure of both the samples explains better performance of the anisotropically consolidated samples. The studies showed that the isotropically consolidated samples showed higher pore pressures compared to the anisotropically consolidated specimens. Another factor which influences the resilient modulus of the pavement materials is the geosynthetic reinforcement. Geocell and geogrid reinforced triaxial samples were prepared to study the effect of reinforcement in the resilient modulus of the base materials. From the literature, it can be seen that most of the research in the triaxial testing equipment were carried out in the non-destructive range of confining pressure and deviatoric stress. Several studies have been conducted by the researchers to visualize the pavement response in the elastic range. However, the studies in the plastic creep range and incremental collapse range were highly limited. In the current study, testing is carried out on the triaxial samples for two different stress ranges. In the first sections, loading was applied in the elastic and elastic shakedown range as per AASTHO T-307. For various loading sequences, a comparative analysis has been done for the resilient modulus of the geogrid and geocell. In the next section, the loading was applied on the sample in the plastic shakedown range and incremental collapse range. The results of the permanent strains and resilient modulus of the sections are compared with the corresponding results of the unreinforced section. In the plastic shakedown and incremental collapse range also the permanent strains of reinforced samples were less than those observed in the unreinforced section. The performance of geosynthetically reinforced pavement layers can be better understood by studying the samples prepared under realistic field conditions. In the case of triaxial experiments the sample size is very less compared to the field conditions and the effect of other pavement layers on the performance of the base layers cannot be studied on triaxial samples. Samples were prepared in the laboratory by modeling the pavement sections in a cuboidal tank, in which different pavement layers are laid one over the other, and a static loading or repeated loading is applied to overcome the bottleneck of small sample size in the triaxial setup. The experiments were conducted on the unreinforced section; geocell reinforced section and geogrid reinforced section placed above strong and weak subgrade. The results of the study are examined regarding the resilient deformation, permanent deformation, pressure distribution and strain measurements for different thicknesses of base layers under repeated loading. The initial parts of the study present the results of experiments and analysis of the results to understand the behavior of geocell reinforced granular base during repeated loading. In this study, an attempt is made to understand the various factors which influence the behavior of geocell reinforced granular base under repeated loading by conducting plate load tests. The loads applied on the pavements are much higher than the standard axle loading used for the design of pavements. High pressure was applied on all the test sections to simulate these higher loading conditions in the field. The optimum width and height of the geocell to be provided, to get maximum reduction in permanent deformation is studied in detail. The effect of resilient deformation of reinforced and unreinforced base layers is quantified by calculating the resilient modulus of these layers. The studies showed that the geocell reinforcement was effective in reducing the permanent and resilient deformations of base layer when compared to the unreinforced samples. The resilient modulus calculated was higher for the reinforced sample with half of the thickness of the unreinforced sample. The effect of reinforcement in the stress distribution within the base layer is also studied by measuring the pressures at different depths of the base layer. The results showed that the pressure getting transferred to the subgrade level was much lower in the case of geocell reinforced base layer. The ultimate aim of any pavement design method is to reduce the distress in the subgrade level and thus leading to increased life of pavements. Pressures at the subgrade level for reinforced and unreinforced sections are studied in detail, the main parameter under study being the stress distribution angle, to investigate the distress in the subgrade level. It was observed that the geocell reinforced sample showed higher stress distribution angle when compared to its unreinforced counterpart. Another important factor that has to be studied is the strains at the subgrade level since it is the governing factor of causing rutting in the pavements. From the experiments conducted in the study, it was shown that the reinforcement is very effective in reducing the strains at the top of subgrades. The implications of the current study are brought out in terms of improved pavement performance as the carbon emission reductions. It is important to analyze the performance of reinforced section under realistic field conditions. To do that experiment were conducted on reinforced and unreinforced base layers placed on top of weak subgrade material. The study showed that the reinforcements are effective in reducing the deformations under weak subgrade conditions also but not as effective as it was under strong subgrade case. The experimental results were then validated with the two-dimensional mechanistic-empirical model for geocell reinforced unpaved roads for predicting the performance of pavements under a significant number of cycles. The modified permanent deformation model which incorporates the triaxial test results and strains measured directly from the base sections were used to model and validate. Plate load experiments were also conducted on base layers reinforced with geogrid to understand the behavior of these reinforced samples under repeated loading. Several factors like the width of the geogrid to be provided and the depth of placing the geogrid in the base layer were studied in detail to achieve maximum reduction in deformations. Permanent and resilient deformation studies were carried out for both reinforced and unreinforced sections of varying thicknesses, and a comparison was made to understand the effect of reinforcement. The geogrid reinforcement could effectively reduce the permanent and resilient deformations when compared to the unreinforced sections. A study was also carried out on the resilient modulus, which explained the better performance of the geogrid reinforced samples by showing higher resilient modulus for reinforced samples than the unreinforced specimens. The performance of the geogrid reinforced base layers was further verified by studying the pressure distribution at the subgrade level and by calculating the stress distribution angle corresponding to the reinforced and unreinforced samples. The strains at the subgrade level were also studied and compared with the unreinforced sample which showed a better performance of geogrid reinforced samples. The results from the strain gauges fixed in the geogrid were further used to model and validate the permanent deformation model. Experiments were conducted on geogrid-reinforced base layer placed above weak subgrade conditions. The results showed that the reinforcement was effective in reducing the deformations under weak subgrade conditions also. Apart from conducting the laboratory studies, experimental results were numerically modeled to accurately back-calculate the resilient moduli of the layers used in the study. 3D numerical modeling of the unreinforced and honeycomb shaped geocell reinforced layers were carried out using finite element package of ANSYS. The subgrade layer, geocell material, and infill material were modeled with different material models to match the real case scenario. The modeling was done for both static and repeated load conditions. The material properties were changed in a systematic fashion until the vertical deformations of the loading plate matched with the corresponding values measured during the experiment. The experimental study indicates that the geocell reinforcement distributes the load in the lateral direction to a relatively shallow depth when compared to the unreinforced section. Numerical modeling further strengthened the results of the experimental studies since the modeling results were in sync with the experimental data.