[pt] O presente estudo experimental apresenta o comportamento mecânico e a durabilidade de compósitos de solo arenoso reforçado com fibras de polipropileno e de fibras vegetais de coco, sisal e curauá, aleatoriamente distribuídas, submetidos ao envelhecimento natural, com o objetivo de estudar a sua aplicação em obras geotécnicas. O programa experimental consistiu na execução de ensaios triaxiais drenados nas amostras de areia pura, areia-fibra no tempo zero (amostras de controle) e nos compósitos expostos por um período máximo de 8 meses, com o objetivo de avaliar a durabilidade dos compósitos. Foram realizados ensaios de tração direta nas fibras vegetais sem degradação e nas fibras utilizadas como reforço em compósitos expostos ao ambiente externo e ao tempo, localizadas nas profundidades de 75 e 125 cm. Para um melhor entendimento da variação dos resultados obtidos, os ensaios triaxiais e de tração foram executados nos intervalos de tempo: 0, 60, 120 e 240 dias. Foi possível observar que todos os compósitos expostos apresentaram queda na resistência de cisalhamento, em relação às amostras de controle, inclusive os reforçados com fibra de polipropileno. Os compósitos reforçados com fibra de coco apresentaram baixa degradação, se comparados com as amostras reforçadas com outras fibras vegetais. Quanto aos ensaios de tração, a fibra de curauá apresentou as maiores resistências à tração inicial e final, após os 8 meses, porém foi a fibra que mais sofreu degradação durante o período em exposição, sofrendo grandes per-das de resistência. Todas as fibras analisadas apresentaram degradação maior na profundidade de 75 cm. / [en] The present experimental study presents the mechanical behavior and the du-rability of composites of sandy soil reinforced with polypropylene fibers and vegetal fibers of coconut, sisal and curauá, randomly distributed, submitted to the natural aging, with the objective of studying their application in earthworks. The experimental program consisted in the execution of triaxial tests in the sand, sand-fiber samples at zero time (control samples) and in the exposed composites for up to 8 months, in order to evaluate the durability of the composites. Direct tensile tests were done on the non-degraded natural fibers and on the fibers used as reinforcement in samples exposed to the external environment and to the time, located at depths of 75 and 125 cm. For a better understanding of the variation of the obtained results, the triaxial and tensile tests were performed in the time intervals: 0, 60, 120 and 240 days. It was possible to observe that all exposed composites presented a drop in shear strength, in relation to the control samples, inclusive those reinforced with polypropylene fiber. The composites reinforced with coconut fiber presented low degradation when compared with the samples forced with other vegetable fibers. Regarding the tensile tests, the curaua fiber showed the greatest resistance to the initial and final traction, after 8 months, but it was the fiber that suffered the most degradation during the exposure period, suffering great losses of resistance. All the analyzed fibers presented degradation greater in the depth of 75 cm.

This study presents the climatic effects (rainfall and evaporation) on the stability of reinforced soil walls constructed with nonwoven geotextiles reinforcements using numerical modeling. The evaluation of the climatic effects was organized in two steps: (1) numerical modeling of the infiltration compared to a laboratory full-scale model of a nonwoven reinforced soil wall and; (2) a numerical investigation of a hypothetical geosynthetic-reinforced soil wall subjected to climatic changes including precipitation and evaporation, for a period of 2 years. The numerical modeling of infiltration into the full-scale model was conducted using two representative hydraulic parameters of backfill soil (suction and volumetric moisture content). The infiltration modeling of the laboratory reinforced structure was conducted to provide better understanding around the hydraulic behavior and water path into regions not measured by instrumentation during laboratory tests. Numerical calibration was conducted in order to capture the capillary break developed at soil-geotextile interfaces, including the anchorage of the reinforcements in the wrap-around facing. As a second step of this study, a hypothetical reinforced soil wall constructed with nonwoven geotextile was modeled using the same hydraulic properties of soil and geotextile used in the previously described numerical modeling. The climatic changes were simulated considering the water balance at ground surface. The climatic effects on the reinforced soil wall were assessed by the use of soil suction changes and consequent influences on the factors of safety over 2 years of operation. Results from numerical simulation of infiltration into the laboratory model indicated that water breakthrough did not occur uniformly along the length of the geotextile. In addition, numerical infiltration into the laboratory model showed that the water path into the reinforced zone is influenced by the anchorage of the reinforcement in the wrap-around facing. The results of the climatic variations in the hypothetical structure showed that approximately 50% of potential evaporation and total rainfall effectively evaporates and infiltrates. Also, the results revealed that the capillary barrier did not generate significant surface runoff and did not reduce the effective infiltration in the reinforced zone. On the other hand, water was observed to advance faster outside of the reinforced zone than inside of the reinforced zone because of the capillary barrier. Additionally, simulations showed that soil inside of the reinforced zone never recovered its initial suction value after first wetting because the capillary barrier restricted evaporation. Results also revealed that increases in global factor of safety, after first wetting of the geotextile reinforced soil wall, occurred because of the increases in soil suction of the first reinforced layer. Lastly, cumulative precipitation during successive days of rainfall showed some correlation to changes in global factor of safety. / Este estudo apresenta os efeitos das variações climáticas (chuva e evaporação) em muros de solo reforçado com geotêxtil não tecido através de analises numéricas. A avaliação dos efeitos climáticos foi dividida em duas fases: (1) calibração numérica da infiltração em um protótipo de laboratório de muro reforçado com geotêxtil não tecido e; (2) extrapolação dos resultados de infiltração para uma estrutura hipotética incluindo as variações climáticas de chuva e evaporação por um período de 2 anos. A calibração numérica foi realizada por meio de duas variáveis (sucção e umidade volumétrica) medidas durante a infiltração no protótipo. Estudos numéricos do processo de infiltração foram conduzidos para melhor entender o comportamento hidráulico da infiltração em regiões que não foram monitoradas durante a infiltração no protótipo. A calibração numérica foi conduzida com o objetivo de capturar o efeito da barreira capilar na interface solo-geotêxtil não tecido, incluindo a ancoragem do reforço próximo a face envelopada. A partir dos resultados da calibração, um muro hipotético reforçado com geotêxtil não tecido foi modelado sob condições climáticas reais (chuva e evaporação), e seu desempenho foi avaliado através das variações de sucção e do fator de segurança ao longo de 2 anos. As variações climáticas foram modeladas considerando o balanço de hídrico na superfície do solo. Os resultados da calibração numérica do modelo de laboratório indicaram que a barreira capilar na interface solo-reforço rompeu de forma não uniforme ao longo do geotêxtil não tecido. Além disso, a avaliação da infiltração mostrou que o fluxo de água tem sua direção afetada pela ancoragem do reforço próximo a face. Os resultados das variações climáticas na estrutura hipotética mostraram que aproximadamente 50% da evaporação potencial e da chuva total efetivamente evapora e infiltra. Além disso, os resultados revelaram que a formação de barreira capilar, e consequente retardo na infiltração, não gerou escoamento superficial significativo e não reduziu o volume de água efetivamente infiltrado na zona reforçada. Ademais, as variações de sucção observadas na zona reforçada se mostraram diretamente ligadas aos dias consecutivos de chuva. Por outro lado, observou-se que a frente de umedecimento avançou mais rápido fora da zona reforçada do que dentro da zona reforçada devido à barreira capilar. As simulações mostraram que o solo dentro da zona reforçada nunca recuperou seu valor inicial de sucção após o primeiro umedecimento porque a barreira capilar restringiu a evaporação. Os resultados também revelaram que o aumento no fator global de segurança, após o primeiro umedecimento do muro reforçado com geotêxtil, ocorreu devido ao aumento da sucção do solo da primeira camada reforçada. Por fim, a precipitação acumulada durante dias consecutivos de chuva mostrou correlação com as mudanças no fator de segurança.

Em geral, as recomendações normativas sugerem a utilização de materiais granulares para a construção de estruturas em solo reforçado, principalmente devido à sua elevada resistência ao cisalhamento e boa capacidade de drenagem. No entanto, nem sempre há disponibilidade deste tipo de material no entorno das obras, tornando o uso dos solos finos imperativo para a viabilização desta solução. No Brasil, solos residuais finos são encontrados em abundância e, muitas vezes, apresentam excelentes parâmetros de resistência ao cisalhamento e baixa compressibilidade. Contudo, o seu uso pode induzir poro-pressões indesejáveis durante a construção ou cisalhamento do aterro reforçado. Por outro lado, as elevadas sucções matriciais que podem persistir em seu interior geram um aumento na estabilidade dos maciços reforçados. Neste contexto, este trabalho apresenta os resultados experimentais e discute o efeito da variação climática (umedecimento e secagem) na resistência de interface solo coesivo-fita polimérica de uma estrutura de contenção em solo reforçado. Os ensaios foram realizados com amostras compactadas de um solo residual de gnaisse típico da cidade de São Paulo e uma fita polimérica de alta aderência. Os corpos de prova foram submetidos a ensaios de cisalhamento direto e de arrancamento sob três diferentes níveis de tensão normal e de sucção, além da condição inundada. Ensaios triaxiais saturados (CU) e não saturados (CW) foram realizados para a determinação da envoltória de resistência tridimensional do solo, avaliação da eficiência da interação solo-reforço e para a verificação do comportamento da água intersticial durante o cisalhamento. Os resultados indicam que o solo coesivo em questão apresenta excelentes parâmetros de resistência ao cisalhamento, elevada capacidade de se manter sob pressões negativas da água intersticial e uma eficiente interação com as fitas poliméricas, o que possibilitaria a execução de estruturas estáveis quanto ao arrancamento dos reforços. Além disso, sugerem um crescimento não linear da máxima resistência de interface com o aumento da sucção matricial do solo e uma tendência de redução dos coeficientes de atrito aparente solo-reforço (f*) com o umedecimento das amostras. Porém, mostraram que a sucção matricial exerce pouca influência na resistência residual da interface solo reforço. / Current specifications for reinforced soil structures generally require the use of granular backfill due to their high strength, well drainage capacity and low volume change potential. However, in cases where granular fills are not easily and readily available, poorly draining soils should be used to enable the implementation of a mechanically stabilized earth wall (MSEW). In Brazil, the fine-grained residual soils that cover large areas of its territory frequently present high shear strengths and low compressibility. However, the use of cohesive soils can cause unwanted effects in structure stability due to the water content variations of the backfill soil, and the potential development of pore-water pressures or loss of strength. On the other hand, matric suctions may increase the soil-geosynthetic interface shear strength. In this context, this study presents the experimental results and discusses the effects of seasonal climatic variations (wetting and drying) on shear strength of soil-geosynthetic straps interfaces under unsaturated conditions. For the laboratory investigation, a compacted residual soil of gneiss composed of 80% silty sand passed through a 0.075mm sieve, sourced from São Paulo city, and a high-tenacity polyester strap were used. Direct shear and pullout tests were conducted with three different net normal stresses and levels of matric suction, besides the inundated condition. Triaxial tests under saturated (CU) and unsaturated (CW) conditions with suction measurement using a high capacity tensiometer were performed in order to evaluate the shear strength parameters of the unsaturated soil, the interface efficiency of the soil-geosynthetic strap and the pore water pressure variations during shear. The results indicate that the cohesive soil used in this study has excellent shear strength parameters, a high capacity to maintain negative pore water pressures and presents an efficient interaction with the geosynthetics straps, which would allow the implementation of a stable MSEW for failure by pullout. Furthermore they reveal that the peak shear strength of the soil-geosynthetic strap interface increases nonlinearly with the soil suction, while the apparent friction factor (f*) decreases with the increase in molding moisture contents. On the other hand, the effect of suction on the post-peak shear strength of the interface was negligible.

The present thesis proposes model for the analyses of stress-strain response of fiber reinforced soil and municipal solid waste (MSW). The concept of reinforcing soils by introducing tension resisting elements such as fibers is becoming widely accepted. Fiber inclusions are found to improve the post-peak behavior of the soil. Evaluation of the stress-strain response of the fiber-reinforced soil indicates that mobilization of the fiber tension generally requires a strain level higher than that corresponding to the peak strength of unreinforced soil. Further, geotechnical engineering properties of MSW such as compressibility, shear strength and stiffness are of prime importance in design and maintenance of landfills. It is also referred in literature that MSW tends to behave as fiber-reinforced soil due to the presence of various types of wastes in its matrix. However, it is not well understood how the stress-strain and strength characteristics vary with time as the biodegradation of waste continues in the landfill. Based on the experimental observations, in this thesis, an attempt is made for developing generalized constitutive models based on the critical state soil mechanics frame work for fiber reinforced soils and municipal solid waste. The proposed models consider the fiber effect in fiber reinforced soil and, time dependent mechanical and biodegradation effects in case of municipal solid waste, respectively. The proposed models are able to capture the stress-strain and pore water pressure response in both the cases. For better understanding, the present thesis is divided into following seven chapters. Chapter 1 is an introductory chapter, in which the need for use of the constitutive models is presented. Further, the organization of thesis is also presented. Chapter 2 presents a brief description of the available studies in the literature on fiber-reinforced soils and municipal solid waste. Various studies on fiber-reinforced soil included experimental results (both laboratory and field) and modeling methods. Experiments on fiber-reinforced soils were mainly carried out with triaxial compression tests, unconfined compression tests, direct shear tests, one dimensional consolidation tests, etc. Force equilibrium model, limit equilibrium model, statistical theory, regression based models are some of the models available in the literature for quantifying the strength of the fiber-reinforced soil. Further, various studies with regard to the engineering properties of municipal solid waste and their characteristic properties available in the literature are presented. They include different models proposed by various researchers for the prediction of stress-strain response, time dependent behavior and load settlement analysis of the municipal solid waste. Finally, based on the literature review, the scope and objectives of the thesis are presented at the end. Chapter 3 describes various types of soils, properties of soils and fibers used in the present study. A detailed description of the sample preparation and methods adopted in the experimental program are presented in this chapter. Chapter 4 presents the experimental results of triaxial compression tests and one dimensional consolidation test carried out on fiber-reinforced soils. Based on the experimental observations, a constitutive model for fiber-reinforced soil in the frame work of modified cam clay model is proposed. Further, the detailed derivation of proposed model and the discussion on evaluation of the input model parameters from triaxial and consolidation tests are presented. The predictions from the proposed models are validated with the experimental data. From the comparison of the results from the proposed model and experiments, it is evident that the proposed model is able to capture stress-strain behavior of fiber-reinforced soils. Chapter 5 presents the experimental studies on the behavior of municipal solid waste based on the triaxial compression and consolidation tests. Based on the experimental observations, a constitutive model for municipal solid waste in the frame work of modified cam clay model is proposed which considers the mechanisms such as mechanical creep and biodegradation. It also provides detailed description of the selection of the input parameters required for the proposed model. The experimental results in the form of stress-strain and pore water pressure response are compared with the prediction from the proposed model. In addition, the applicability of the proposed model is illustrated using detailed parametric studies of parameters of the model for various ranges. Chapter 6 presents a brief study of load settlement response on municipal solid waste using a case example. The constitutive model for municipal solid waste proposed in chapter 5 is used to study the time-settlement response of municipal solid waste and to compare the results with available published models considering different mechanisms. The major conclusions from the study are presented at the end. Chapter 7 presents a brief summary and conclusions from the various studies reported in the present thesis. vi

Η ΒΥΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της. / Εκτελώντας δυναμικές αναλύσεις με χρήση πεπερασμένων στοιχείων, αναλύεται η σεισμική απόκριση τεσσάρων τοίχων αντιστήριξης οπλισμένου εδάφους στην Ταϊβάν με στοιχεία πρόσοψης κυβόλιθους. Οι τοίχοι, των οποίων τα ύψη κυμαίνονται από 3.20 m έως 5.60 m και έχουν ως οπλισμούς στρώσεις γεωπλέγματος, υποβλήθηκαν στο σεισμό Chi-Chi (1999) και η συμπεριφορά τους κρίθηκε από επιτυχής έως ανεπιτυχής: δύο από αυτούς κατέρρευσαν, ένας υπέστη μόνο ελαφρές βλάβες, ενώ ο τέταρτος τοίχος παρέμεινε πρακτικά ανέπαφος. Η μη-γραμμική ανάλυση βασίσθηκε στα γνωστά γεωμετρικά και μηχανικά χαρακτηριστικά του κάθε τοίχου, του γεωπλέγματος, των γεωτεχνικών συνθηκών σε κάθε θέση, του είδους και των ιδιοτήτων του υλικού επίχωσης. Η συμπεριφορά του εδαφικού υλικού προσομοιώθηκε κάνοντας χρήση του κριτηρίου Mohr-Coulomb, ενώ ως διέγερση βάσης στις δυναμικές αναλύσεις πεπερασμένων στοιχείων χρησιμοποιήθηκαν τα καταγεγραμμένα επιταχυνσιογραφήματα κοντά στις θέσεις των τοίχων. Τα αποτελέσματα των αναλύσεων (και ειδικά η εκτιμώμενη παραμορφωμένη μορφή των τοίχων) επαλήθευσαν την παρατηρούμενη συμπεριφορά των τοίχων. Βασιζόμενοι στα αποτελέσματα, βρέθηκαν οι λόγοι της ανεπιτυχούς συμπεριφοράς των δύο τοίχων που κατέρρευσαν, ενώ εξηγήθηκε η διαφοροποίηση της συμπεριφοράς των δύο τοίχων που δεν υπέστησαν βλάβες. Επιπροσθέτως, πραγματοποιήθηκαν παραμετρικές αναλύσεις για να ευρεθεί η επίδραση σημαντικών παραμέτρων σχεδιασμού, όπως το βάθος θεμελίωσης του τοίχου, η απόσταση και το μήκος των οπλισμών, η συνεισφορά των ράβδων σύνδεσης στην ευστάθεια των στοιχείων πρόσοψης και η συνεισφορά της ανώτατης στρώσης οπλισμού στην ευστάθεια του τοίχου. Επίσης αναλύθηκε η ευστάθεια των τοίχων χρησιμοποιώντας ένα εμπορικά διαθέσιμο λογισμικό οριακής ισορροπίας, το οποίο βρέθηκε ικανό να προβλέψει την παρατηρούμενη επιτυχή και ανεπιτυχή συμπεριφορά των τεσσάρων τοίχων. / The seismic response of four reinforced soil segmental retaining walls in Taiwan, is analyzed using the dynamic finite element method. The walls – whose heights ranging from 3.20 m to 5.60 m and layers of geogrid reinforcement – were subjected to the Chi-Chi earthquake (1999) and their performance ranged from successful to unsuccessful: two of them were collapsed, one suffered only minor damage whereas the fourth wall remained practically intact. The non-linear analyses were based on the known geometrical and mechanical characteristics of each wall and of the geogrid reinforcement, the geotechnical conditions at each site and the type and properties of backfill material. The soil material behavior was modeled by using the Mohr-Coulomb failure criterion whereas recorded accelerograms in the vicinity of the sites of the walls were used as base excitation in the dynamic finite analyses. The results of the analyses (and especially the estimated deformed shape of the walls) showed a remarkable agreement with the observed performance of the walls. Based on these results the reasons for the unsuccessful performance of the two failed walls were identified whereas the differentiation of the behavior of the two undamaged walls was explained. Furthermore, parametric analyses were conducted to identify the effects of such important design parameters as the depth of the foundation of the wall, the spacing and length of reinforcement, the contribution of connecting pins to the stability of the facing elements as well as the contribution of the top layer of reinforcement to the stability of the wall. The stability of the walls were also analyzed by using a commercially available limit equilibrium software which was found to be able to predict the observed successful and unsuccessful performance of the four walls.

Em geral, as recomendações normativas sugerem a utilização de materiais granulares para a construção de estruturas em solo reforçado, principalmente devido à sua elevada resistência ao cisalhamento e boa capacidade de drenagem. No entanto, nem sempre há disponibilidade deste tipo de material no entorno das obras, tornando o uso dos solos finos imperativo para a viabilização desta solução. No Brasil, solos residuais finos são encontrados em abundância e, muitas vezes, apresentam excelentes parâmetros de resistência ao cisalhamento e baixa compressibilidade. Contudo, o seu uso pode induzir poro-pressões indesejáveis durante a construção ou cisalhamento do aterro reforçado. Por outro lado, as elevadas sucções matriciais que podem persistir em seu interior geram um aumento na estabilidade dos maciços reforçados. Neste contexto, este trabalho apresenta os resultados experimentais e discute o efeito da variação climática (umedecimento e secagem) na resistência de interface solo coesivo-fita polimérica de uma estrutura de contenção em solo reforçado. Os ensaios foram realizados com amostras compactadas de um solo residual de gnaisse típico da cidade de São Paulo e uma fita polimérica de alta aderência. Os corpos de prova foram submetidos a ensaios de cisalhamento direto e de arrancamento sob três diferentes níveis de tensão normal e de sucção, além da condição inundada. Ensaios triaxiais saturados (CU) e não saturados (CW) foram realizados para a determinação da envoltória de resistência tridimensional do solo, avaliação da eficiência da interação solo-reforço e para a verificação do comportamento da água intersticial durante o cisalhamento. Os resultados indicam que o solo coesivo em questão apresenta excelentes parâmetros de resistência ao cisalhamento, elevada capacidade de se manter sob pressões negativas da água intersticial e uma eficiente interação com as fitas poliméricas, o que possibilitaria a execução de estruturas estáveis quanto ao arrancamento dos reforços. Além disso, sugerem um crescimento não linear da máxima resistência de interface com o aumento da sucção matricial do solo e uma tendência de redução dos coeficientes de atrito aparente solo-reforço (f*) com o umedecimento das amostras. Porém, mostraram que a sucção matricial exerce pouca influência na resistência residual da interface solo reforço. / Current specifications for reinforced soil structures generally require the use of granular backfill due to their high strength, well drainage capacity and low volume change potential. However, in cases where granular fills are not easily and readily available, poorly draining soils should be used to enable the implementation of a mechanically stabilized earth wall (MSEW). In Brazil, the fine-grained residual soils that cover large areas of its territory frequently present high shear strengths and low compressibility. However, the use of cohesive soils can cause unwanted effects in structure stability due to the water content variations of the backfill soil, and the potential development of pore-water pressures or loss of strength. On the other hand, matric suctions may increase the soil-geosynthetic interface shear strength. In this context, this study presents the experimental results and discusses the effects of seasonal climatic variations (wetting and drying) on shear strength of soil-geosynthetic straps interfaces under unsaturated conditions. For the laboratory investigation, a compacted residual soil of gneiss composed of 80% silty sand passed through a 0.075mm sieve, sourced from São Paulo city, and a high-tenacity polyester strap were used. Direct shear and pullout tests were conducted with three different net normal stresses and levels of matric suction, besides the inundated condition. Triaxial tests under saturated (CU) and unsaturated (CW) conditions with suction measurement using a high capacity tensiometer were performed in order to evaluate the shear strength parameters of the unsaturated soil, the interface efficiency of the soil-geosynthetic strap and the pore water pressure variations during shear. The results indicate that the cohesive soil used in this study has excellent shear strength parameters, a high capacity to maintain negative pore water pressures and presents an efficient interaction with the geosynthetics straps, which would allow the implementation of a stable MSEW for failure by pullout. Furthermore they reveal that the peak shear strength of the soil-geosynthetic strap interface increases nonlinearly with the soil suction, while the apparent friction factor (f*) decreases with the increase in molding moisture contents. On the other hand, the effect of suction on the post-peak shear strength of the interface was negligible.

[pt] O presente trabalho permite avaliar o comportamento de um solo reforçado e não reforçado com fibras de polipropileno (teor de 0.5 por cento em relação ao peso seco do solo) submetido a ensaios triaxiais de extensão, bem como a influência da adição de fibras na resistência e nos mecanismos de ruptura do solo reforçado. Para tanto, desenvolveu-se um programa experimental compreendendo a etapa final de um equipamento triaxial do tipo Bishop e Wesley de grandes dimensões e a execução de ensaios triaxiais drenados de extensão. Os ensaios triaxiais realizados permitiram a determinação dos parâmetros de resistência do solo e da mistura solo–fibra. Os resultados obtidos propiciaram a um melhor entendimento das alterações geradas pela inclusão aleatória de fibras de polipropileno à matriz da areia estudada. O desempenho das fibras no interior da massa de solo indica que estas sofreram deformações plásticas de tração, alongando-se, porém este alongamento é atribuído à fase de adensamento e não à fase de cisalhamento dos ensaios triaxiais de extensão realizados, já que foi possível observar que a adição das fibras não incrementa a resistência à tração do solo, quando este estiver submetido a esforços de extensão. / [en] The present study allows evaluating the behavior of a reinforced and unreinforced soil with fibers of polypropylene (0.5 per cent content of dry weight of soil) subjected to triaxial extension tests, as the influence of adding fibers in the resistance and the rupture mechanisms of reinforced soil. Therefore, it was developed an experimental program comprising the development of a Bishop and Wesley’s triaxial-type equipment which has a larger size than conventional triaxial equipment and an execution of drained triaxial extension tests. The present study submits triaxial tests results aiming the determination of strength parameters of soil and soil – fiber mixture. The obtained results led a better understanding of the alterations generated by the random inclusion of polypropylene fibers to the pattern sand studied. The accomplishment of fiber performance within soil mass indicates that they undergo tensile plastic deformation, elongating, but this elongating is attributed to shear stage in the triaxial extension tests realized, as was conferred that the addition of fiber does not increase the tensile strength of soil.

This thesis deals with numerical 3D modeling of reinforced earth block under concentrated wheel load. This is a parametric study, which varies entering face and load position and even his own task. And either by simplification of the CSN 73 0037 or directly. At the beginning briefly describes the construction of reinforced soil in terms of history, application, construction, and properties of materials from which the structure is formed. Attention is also paid to static action and methods of spreading of a concentrated load to earth block. structural design using analytical methods is also part of the thesis

Recent developments in constructions have heightened the need for protecting existing buried infrastructure. 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. Additionally applied loads over water mains led to catastrophic damage, which result in severe damage to the infrastructure surrounding these mains. Therefore, providing protection to these existing buried infrastructure against increased loads due to new constructions is important and necessary. In this research, a solution was proposed and assessed, where the protection concept would be achieved through the inclusion process of geogrid-reinforcing layers in the soil cover above the buried infrastructure. The controlling parameters for the inclusion of geogrid-reinforcing layers was assessed experimentally and numerically. Twenty-three laboratory tests were conducted on buried flexible and rigid pipes under unreinforced and geogrid-reinforced sand beds. All the investigated systems were subjected to incrementally increasing cyclic loading, where the contribution of varying the burial depth of the pipe and the number of the geogrid-reinforcing layers on the overall behaviour of the systems was investigated. To further investigate the contribution of the controlling parameters in the pipe-soil systems performance, thirty-five numerical models were performed using Abaqus software. The contribution of increasing the amplitude of the applied cyclic loading, the number of the geogrid-reinforcing layers, the burial depth of the pipe and the unit-weight of the backfill soil was investigated numerically. The inclusion of the geogrid-reinforcing layers in the investigated pipe-soil systems had a significant influence on decreasing the transferred pressure to the crown of the pipe, generated strains along its crown, invert and spring-line, and its deformation, where reinforcing-layers sustained tensile strains. Concerning rigid pipes, the inclusion of the reinforcing-layers controlled the rebound that occurred in their invert deformation. With respect to the numerical investigation, increasing the number of the reinforcing-layers, the burial depth of the pipe and the unit-weight of the backfill soil had positive effect in decreasing the generated deformations, stresses and strains in the system, until reaching an optimum value for each parameter. Increasing the amplitude of the applied loading profile resulted in remarkable increase in the deformations, stresses and strains generated in the system. Moreover, the location of the maximum tensile strain generated in the soil was varied, as well as the reinforcing-layer, which suffered the maximum tensile strain. / Government of Egypt

[pt] O presente estudo teve como principal objetivo demonstrar que fibras derivadas da reciclagem de garrafas PET (Polietileno Tereftalato), confeccionadas com 100 porcento do resíduo, pela indústria têxtil, podem ser uma boa alternativa se utilizadas como reforço de solos, quando submetidos a diferentes níveis de cargas. Buscando uma melhor aplicabilidade para este material, foram executados ensaios de compressão triaxial drenados em laboratório, bem como ensaios de prova de carga em placa e também com simulação de um talude em modelo físico reduzido, para a determinação do comportamento mecânico de uma areia e do compósito areia-fibras PET. Para os ensaios triaxiais drenados, foram utilizadas fibras PET com dois títulos (correspondente ao diâmetro das fibras) e comprimentos distintos (1,4 dtex com 38 mm e 3,3 dtex com 56 mm), inseridas aleatoriamente na massa de solo, onde foi utilizado o teor de 0,5 porcento de fibras, em relação ao peso seco do solo, teor de umidade de 10 porcento e densidade relativa de 50 porcento. Os resultados mostraram que o comportamento da areia pura é influenciado pela adição de fibras PET, melhorando os parâmetros de resistência, como o intercepto coesivo e o ângulo de atrito, definidos pelo critério de Mohr-Coulomb. O compósito reforçado com as fibras PET de menor título e menor comprimento apresentou um maior ganho na resistência ao cisalhamento, mas ambos os compósitos, em comparação ao solo não reforçado, apresentaram uma maior resistência. Para os ensaios de prova de carga em placa e para a simulação do talude, ambos realizados em modelo físico reduzido, foram utilizadas as fibras de menor título e menor comprimento como elemento de reforço. Observa-se que a inserção das fibras PET melhora o comportamento carga-recalque da areia pura, onde o compósito reforçado apresenta uma maior capacidade de suporte e a redução dos recalques, bem como uma mudança na propagação e formação das fissuras ao redor da placa. Na simulação do talude, a inserção das fibras PET promove uma alteração completa no mecanismo de ruptura ocorrido no compósito, quando comparado à ruptura da areia pura. Ressalta-se o emprego positivo das fibras PET para aplicação como reforço de solos em obras geotécnicas (como por exemplo, em camadas de aterros sanitários, aterros sobre solos moles, reforço de taludes, base de fundações superficiais e controle de erosão), além de eliminar problemas atuais de disposição de resíduos, dando um fim mais nobre a este material, com benefícios ambientais, sociais e econômicos. / [en] The main objective of this study was to demonstrate that fibers derived from the recycling of PET (Polyethylene Terephthalate) bottle, 100 percent made from the residue by the textile industry, can be a good alternative if used as reinforcement of soil, when submitted to different load levels. Looking for a better applicability for this material, were executed drained triaxial compression tests in laboratory, as well as plate load tests, also with slope simulation in a reduced physic model, to evaluate the mechanical behavior of a sand and a composite sand-PET fibers. For the drained triaxial tests, were used PET fibers with two different titles (corresponding to the fiber diameters) and lenghts (1,4 dtex com 38 mm e 3,3 dtex com 56 mm), distributed randomly in the soil mass, where was used a fiber contente of 0,5 percent by relation to the soil s dry weight, moisture content of 10 percent and relative density of 50 percent. The results showed that the pure sand behavior was influenced by the addition of PET fibers, improving the strenght parameters as the cohesion intercept and the friction angle, defined by the Mohr-Coulomb criteria. The composite reinforced with PET fibers with minor title and lenght presented a better improvement in the shear strenght, but both composites, compared to the non reinforced soil, showed greater resistence. For the plate load tests and for the slope simulation, both performed in a reduced physic model, it was used the fiber with minor title and lenght as reinforcement element. The addiction of PET fibers improve the load-settlement behavior of the sand, where the reinforced composite shows a greater bearing capacity, a reduction of the settlements and a change in the propagation and formation of fissures around the plate. In the slope simulation, the addiction of PET fibers promove a complete alteration in the rupture mechanism that occurred in the composite, when compared to the rupture of the pure sand. It is highlighted the positive use of PET fibers for application as soil reinforcement in geotechnical works (as an example, in landfill layers, embankment on soft soil, slope reinforcement, base of shallow foundations and erosion control), eliminating current problems of waste disposal, giving a noble end to this material, with environmental, social and economical benefits.