Geogrid reinforcement can improve the performance of pavements by stiffening the aggregate base material and decreasing pavement deformations. Understanding the effects of cyclic loading on the modulus of geogrid-reinforced base materials would help engineers better anticipate actual increases in the modulus of aggregate base materials under given traffic loads. The objective of this laboratory research was to investigate the effects of cyclic loading on the resilient modulus, the modulus to peak axial stress, the elastic modulus, and the modulus at 2 percent strain of geogrid-reinforced aggregate base materials. The scope of the research included two aggregate base materials (Wells Draw and Springville) having different particle-size distributions and particle angularity. Geogrid-reinforced and unreinforced specimens were subjected to conditioning periods consisting of cyclic loading ranging from 10 to 10,000 cycles. Immediately following cyclic loading, all specimens were tested using the quick shear portion of the American Association of State Highway and Transportation Officials T 307 (Determining the Resilient Modulus of Soils and Aggregate Materials). Specimen preparation involved material weigh-outs, compaction, and membrane applications. Specimen testing in the loading machine consisted of two testing portions, including cyclic loading and quick shear testing. The cyclic loading data were used to calculate the resilient modulus on 200-cycle intervals throughout the duration of the conditioning period. The quick shear data were used to calculate the peak axial stress, the modulus to peak axial stress, the elastic modulus and the modulus at 2 percent strain. For the Wells Draw material, the resilient modulus increases by 11 percent for the specimens with geogrid and increases by 8 percent for the specimens without geogrid as the number of load cycles increases from 1,000 to 10,000. For the Springville material, the resilient modulus increases by 2 percent for the specimens with geogrid and increases by 3 percent for the specimens without geogrid as the number of load cycles increases from 1,000 to 10,000. As with other studies, the results do not show a consistent or significant effect of geogrid reinforcement on the resilient modulus of the tested materials. The modulus at 2 percent strain has the most potential for consistently showing improvements to aggregate base materials due to both cyclic loading and geogrid reinforcement. For the Wells Draw and Springville materials, the modulus at 2 percent strain increases by 31 and 9 percent, respectively, as the number of load cycles increases from 10 to 10,000. Additionally, for the Wells Draw and Springville materials, the modulus at 2 percent strain of the specimens with geogrid is 23 and 46 percent, respectively, greater than that of the specimens without geogrid. The results show a consistent and significant positive effect of geogrid reinforcement on modulus at 2 percent strain of the tested materials. According to the modulus at 2 percent strain results, a sufficient conditioning period appears to occur at 5,000 cycles for the Wells Draw material and 10,000 cycles for the Springville material.

The objective of this research was to apply a previously recommended laboratory testing protocol to specific aggregate base materials that are also the subject of ongoing full-scale field testing. The scope of this research involved three aggregate base materials selected from three sites where full-scale field testing programs have been established. The first and second field sites included five different geogrid types, categorized as either biaxial or triaxial, in a singlelayer configuration, while the third site included only the triaxial geogrid type in either a singleor double-layer configuration. Geogrid-stabilized and unstabilized control specimens were evaluated using the American Association of State Highway and Transportation Officials T 307 quick shear testing protocol. Measurements of load and axial displacement were recorded and used to develop a stress-strain plot for each specimen tested. The peak axial stress, the modulus to the peak axial stress, the modulus of the elastic portion of the curve, and the modulus at 2 percent strain were then calculated. Statistical analyses were performed to investigate differences between geogridstabilized specimens and unstabilized control specimens and to investigate differences between individual geogrid products or geogrid configurations. Depending on the method of data analysis, the quick shear test results indicate that geogrid stabilization, with the effect of geogrid stabilization averaged across all of the geogrid products evaluated in this study, may or may not improve the structural quality of the aggregate base materials evaluated in this study. The results also indicate that, regardless of the method of analysis, one geogrid product or configuration may be more effective than another at improving the structural quality of a given aggregate base material as measured using the quick shear test. All results from this research are limited in their application to the aggregate base material types, geogrid products, and geogrid configurations associated with this study. Additional research is needed to compare the results of the laboratory quick shear testing obtained for this study with the structural capacity of the geogrid-stabilized and unstabilized control sections that have been constructed at corresponding full-scale field testing sites. Specifically, further research is needed to determine which method of laboratory data analysis yields the best comparisons with field test results. Finally, correlations between the results of quick shear testing and resilient modulus need to be investigated in order to incorporate the findings of the quick shear test on geogrid-stabilized base materials into mechanistic-empirical pavement design.

The modulus of aggregate base layers in pavement structures can potentially be increased through the use of geogrid. However, methods for determining how much structural benefit can be expected from a given geogrid product have not been standardized. A laboratory testing protocol is therefore needed to enable evaluation, in terms of modulus or California bearing ratio (CBR), for example, of the degree of improvement that may be achieved by a given geogrid. Consequently, the objective of this research was to identify a laboratory test method that can be used to quantify improvements in structural capacity of aggregate base materials reinforced with geogrid. For this research, National Cooperative Highway Research Program Report 598 repeated load triaxial, American Association of State Highway and Transportation Officials (AASHTO) T 307 quick shear, and CBR testing protocols were used to test unreinforced and geogrid-reinforced aggregate base materials from northern Utah. Biaxial and triaxial geogrid were investigated in multiple reinforcement configurations. Several statistical analyses were performed on the results of each test method to identify the test that is most likely to consistently show an improvement in the structural capacity of aggregate base materials reinforced with geogrid. The results of this research indicate that, for the methods and materials evaluated in this study, calculation of the modulus at 2 percent strain from the AASHTO T 307 quick shear data is the test method most likely to consistently show an improvement in structural capacity associated with geogrid reinforcement. Of the three configurations investigated as part of this research, placing the geogrid at an upper position within a specimen is preferred. Given that the end goal of the use of geogrid reinforcement is to improve pavement performance, additional research is needed to compare the results of the AASHTO T 307 quick shear test obtained in the laboratory with the structural capacity of geogrid-reinforced aggregate base materials measured in the field. In addition, correlations between the results of the AASHTO T 307 quick shear test and resilient modulus need to be investigated in order to incorporate the findings of the AASHTO T 307 quick shear test on reinforced base materials into mechanistic-empirical pavement design.

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.

Due to the findings of extensive damage on geogrids used in a road embankment in northern Sweden, the Swedish Transport Administration (TRV) started to investigate the reason of these damages. Since the geogrids were installed at low temperature, below 0°C, it was suspected that the damages were connected the low temperature. To analyse whether low temperatures have an influence on the extent of installation damages, both a half-scale setup and temperature controlled tensile tests have been carried out on geogrids. In total five different types of geogrids have been tested; 3 extruded polypropylene geogrids, 1 woven PET geogrid, and 1 welded PET geogrid. All geogrids had an aperture size of approximately 35 mm and specified tensile strength of approximately 40 kN/m. The Half-scale tests was conducted by building a small road embankment inside a freeze container, at the Luleå University of Technology (LTU). The embankment contained crushed aggregate, type 0-70 mm, and geogrids. The purpose of the half-scale test was to simulate installation of geogrids at different temperatures and thereby investigate whether low temperatures have an influence on the rate of installation damages. The half-scale test was done for each type of geogrid at the temperatures: +20°C, -20°C and -30°C. First, the geogrid was covered by 150 mm of crushed aggregate. Then a vibratory plate (160 kg) was used to compact the crushed aggregate. After each installation, the crushed aggregate was removed carefully by vacuum suction. The geogrid was removed and then analysed by visual control and tensile tests conducted according to ISO 10319:2008 (wide width tensile test). Results from the half-scale tests indicate that 2 out of 5 of the tested geogrids were affected by the testing procedure. The results indicate that: -        one of the geogrids of polyprophylene (here referred to as G2) was more damaged at lower temperatures compared to installation at +20° C. -        the geogrid of woven PET (here referred to as G5) was less damaged at lower temperatures compared to installation at +20° C. Results for the other geogrids are either inconsistent or shows no significant variation of the measured parameters as function of temperature. Hence, these results cannot be interpreted as damage during installation. Temperature controlled tensile tests were done by tensile testing single strands from the geogrids to failure, inside a temperature controlled chamber. The purpose of these tests was to investigate how the strength properties of the geogrids are affected by low temperature. The test was repeated 5 times for each geogrid and temperature (+20°C, 0°C, -10°C and -20°C). Force and strain was measured during the tests. The results from the temperature controlled tensile tests show that the maximum strain decreases with lower temperature for all tested geogrids. The maximum strain decreased by 16% - 49% when the temperature dropped from +20°C to -20°C. The results show that the tensile strength increases with lower temperature for all tested geogrids except for the welded PET geogrid (here referred to as G1). For G1 the tensile strength decreased by approximately 7% at a temperature drop from +20°C to -20°C. For the woven PET geogrid (G5) and the polypropylene geogrids (G2-G3) the tensile strength increased between 13%-45% at a temperature drop from +20°C to -20°C. The E-modulus increased at lower temperature for all tested geogrids. The secant E-modulus at 2% strain increased by 13%-71% at a temperature drop from +20°C to -20°C. Summarized conclusions from the tests: Strength properties changed for all tested geogrids as the temperature decreased. All tested geogrids got stiffer at lower temperatures. The magnitude of the effects is different for different geogrids. The tensile strength increased with lower temperature for all tested geogrids except for the welded PET geogrid, which got lower tensile strength at lower temperature. The half-scale test indicates that the amount of installation damages at geogrids can be dependent of the temperature at installation. However, these indications can only be seen at two out of five tested geogrids. The effect cannot be connected to a specific step in the installation procedure and cannot be explained by the results from the temperature controlled tensile tests. The results from the half-scale test have a statistically low reliability since only one installation for each temperature and geogrid type was done. The compaction equipment used during the test was small, and had low compaction energy compared to a vibratory roller compactor commonly used in construction work. With respect to the discussion above, further studies should be focusing on developing the half-scale test. It is suggested that the test is scaled up to a full-scale test in order to simulate a real installation as close as possible. The test should also be conducted several times for each geogrid at each temperature in order to enable statistical analyses.

[pt] A busca por soluções geotécnicas que aumentem a vida útil das estruturas e também possam economizar material natural levou ao desenvolvimento de produtos conhecidos como geossintéticos. Dentre as várias famílias de geossintéticos, foram criados elementos que funcionassem como reforço de base-subleito em pavimentos na condição de subleito muito deformável, denominadas geogrelhas. O presente trabalho teve o objetivo de analisar o comportamento mecânico de uma estrutura de pavimento reforçado com geogrelha, submetida à aplicação de carregamento cíclico e à variação de umidade do material do subleito. Foi utilizado para o desenvolvimento dos ensaios um modelo físico de verdadeira grandeza no qual foi construída a estrutura do pavimento composta de um subleito de 100 cm de espessura e uma camada de base de brita de 20 cm de espessura. Nesta estrutura analisou-se o efeito da inserção do geossintético como reforço de camada de base e a variação da umidade do subleito. As medidas fornecidas pelos transdutores de deslocamentos (LVDTs) foram os parâmetros de comparação entre a estrutura de pavimento com e sem reforço no decorrer dos ensaios. Os refletômetros no domínio do tempo (TDRs) monitoraram a variação da umidade do subleito. A comparação entre os deslocamentos da estrutura reforçada e não reforçada permitiu determinar a influência do reforço mostrando-se eficiente na redução dos deslocamentos superficiais verticais. A utilização de equipamentos portáteis para avaliar o comportamento mecânico do pavimento in situ mostraram ser uma ferramenta recomendável para estudos defletométricos de forma pontual no pavimento. / [en] The search for geotechnical solutions that increase the life time of structures and can also reduce the use of natural materials carried out to the development of products known as geosynthetic. Among the various families of geosynthetics, have been created elements which function as reinforcement of base-subgrade of pavements when the condition of the subgrade is very deformable, called geogrids. This study had the objective to analyze the mechanical behavior of a structure of geogrid reinforced pavement, submitted to the application of cyclic loading and variation in subgrade layer moisture. It was used for the development of tests a true scale physical model, in which was built a structure of pavement composed of a subgrade with 100 cm of thickness and a gravel layer of 20 cm of thickness. In this structure has been analyzed the effect of insertion of geogrid like base layer reinforcement and a variation in subgrade layer moisture. The measures provided by the displacement transducers (LVDTs) were the parameters of comparison between a structure of pavement with and without reinforcement during the tests. The Time Domain Reflectometry (TDR) monitored the variation of moisture from the subgrade. The comparison between the displacements of reinforced and unreinforced structure allowed determine the influence of reinforcement showing to be efficient to reduce superficial vertical displacements. The use of mobile devices to evaluate the mechanical behavior of the pavement in situ proved to be a tool recommended for punctual studies on pavements.

[pt] A utilização de materiais geossintéticos como reforço em obras geotécnicas vem crescendo bastante nas últimas décadas. A geogrelha, cuja função primária é o reforço de solos, é um entre os diversos tipos de geossintéticos, que vêm sendo utilizados. Diversas são as formas de interação da geogrelha com o solo em um maciço reforçado e o entendimento dos mecanismos que se desenvolvem nestas interações é essencial, pois só a partir daí pode-se obter parâmetros confiáveis para projeto. Pesquisas vêm sendo realizadas por diversos autores, mas muitos aspectos ainda devem ser estudados para que se tenha uma melhor compreensão do comportamento de solos reforçados com geogrelhas. A utilização de uma ferramenta numérica pode ser uma alternativa para que consigamos dar um passo adiante no entendimento da técnica de solo reforçado. Então, modelagens numéricas de ensaios triaxiais e de cisalhamento direto em solos reforçados e não reforçados foram realizadas com a utilização do programa Plaxis. Foram analisadas a influência do reforço no aumento da rigidez e resistência do solo e a resistência de interface solo-reforço. Para calibrar o programa e validar as análises numéricas, foram realizadas retro-análises dos ensaios realizados por Sieira (2003), onde se definiram aspectos importantes para modelar os ensaios, tal como, a melhor forma de impor as condições de contorno. Os resultados obtidos nas análises numéricas dos ensaios triaxiais sugerem que o programa Plaxis permite de forma razoável a reprodução dos ensaios reforçados, sendo possível prever o ganho de resistência do solo com a inclusão do reforço. Uma análise alternativa, onde se aplica um incremento de tensão confinante representativo da influência do reforço, foi também realizada. As análises numéricas dos ensaios de cisalhamento direto em solo arenoso não reforçado permitiram verificar a rotação do eixo das direções das tensões principais quando é aplicado carregamento cisalhante e a presença de uma zona central de cisalhamento (zona de cisalhamento). A resistência de interface sologeogrelha não foi bem reproduzida, indicando que o Plaxis não permite este tipo de avaliação. Quando os reforços encontravam-se inclinados, verificou-se a maior eficiência do reforço rígido e fazendo ângulo de 60º com a superfície de ruptura. / [en] The use of geosynthetic materials as reinforcement in geotechnical engineering works is significantly increasing over the past decades. Geogrid, whose primary functions is reinforcing the soil mass, is one of the geosynthetics that has been used. In a reinforced soil structure, there are different types of interaction between soil and geogrid. To be possible to obtain reliable design parameters is essential to know the mobilized mechanisms in the interaction. This situation has been investigated by many researchers, but there are still many aspects to be better understood about geogrid reinforced soil behavior. In this research, numerical tools have been used to improve our knowledge about reinforced soil techniques. Numerical modeling of triaxial and direct shear tests on reinforced and non reinforced soils were carried out using software Plaxis. It was verified the resistance and stiffness increase of the soil due to geogrid inclusion and the interface soil-reinforcement resistance parameters. To calibrate the software and to validate the numerical analyses, back-analyses of the tests carried out by Sieira (2003) were done. These results helped to define important aspects to the tests modeling such as geometry and tests boundary conditions. The numerical analyses of the triaxial tests suggest that the software Plaxis reasonably allow an adequate reproduction of the reinforced soil tests. It was possible to foresee the increase of soil resistance because of reinforcement inclusion. In addition, an alternative analysis, where one applies a confining stress that reproduces the reinforcement influence, it was done. Numerical analyses of non reinforced direct shear tests had numerically evidenced the rotation of the axis of the principal stresses directions and the presence of a central zone of shear (shear zone). The soil- geogrid interface resistance was not well reproduced, indicating that Plaxis does not allow this type of evaluation. To inclined reinforcement relative to failure plane, it was verified the maximum gain of resistance is achieved with inclined reinforcement at 60º and when rigid geogrids are used.

Este trabalho apresenta resultados de ensaios de arrancamento de geogrelha, obtidos com a utilização de equipamento de dimensões reduzidas. A força de arrancamento foi aplicada por uma máquina universal com capacidade máxima de 30kN, dotada de instrumentação que permitiu registrar a força de arrancamento e o deslocamento da geogrelha em relação ao solo envolvente. Além disto, o ensaio foi instrumentado com uma célula de tensão total instalada no nível da inclusão. A grande vantagem deste equipamento é o pequeno volume de solo utilizado, resultando em um ensaio mais rápido e econômico, proporcionando um controle maior do teor de umidade e do grau de compactação do solo. Considerando que uma grande parte do estado de São Paulo é coberto por solos de granulometria fina, esse equipamento passa a ser uma excelente alternativa para obtenção dos parâmetros de ensaios de arrancamento necessários ao desenvolvimento de projetos em solo reforçado. Para averiguar a possibilidade de uso do ensaio de pequeno porte, nestas condições, para substituir uso das caixas de grandes dimensões foram inicialmente realizadas comparações, através do coeficiente de interação, entre os resultados obtidos através desses dois tipos de ensaios. Os resultados obtidos mostraram que, para as condições de ensaio empregadas utilizando solos com 100% passando na peneira de abertura 2mm e geogrelhas de abertura de malha aproximadamente de 20mm, a resposta do equipamento, se comparada à de ensaios de grandes dimensões, foi excelente. Isto permitiu que se procedesse a uma ampla análise paramétrica, de cunho experimental, em que se variou a velocidade de ensaio, a tensão confinante, as dimensões das amostras de geogrelha, o tipo de solo e a geogrelha, com o intuído de cobrir diferentes situações possíveis de se encontrar nos projetos de engenharia. O trabalho apresenta os principais resultados desta análise / This work presents results of geogrid pullout tests conducted using small scale equipment. The pullout load was applied using a universal load frame, with a maximum capacity of 30kN, capable of recording the pullout load and front displacement. In addition, the test was instrumented with an earth pressure cell installed at the level of the geogrid inclusion. The primary advantage of this equipment is the small volume of soil used in test preparation, resulting in reduced testing time, greater control of the water content and degree of compaction, and significant reduction in overall testing costs. Furthermore, a significant area of the state of Sao Paulo in Brazil is covered by fine grained soils which could be tested according to its pullout behavior using the proposed equipment. To investigate the feasibility of the small scale test facility, comparisons were made between the coefficient of interaction obtained from tests of small and large dimensions. The results show that for the tested materials there were no differences between pull out parameters from both equipment. Additionally it was investigated the effects of testing speed, confining pressure, sample dimensions, and soil and geogrid materials. Results of these tests are presented and discussed

O intenso crescimento populacional traz consigo uma preocupação ambiental, já que, diante da necessidade de exploração dos recursos naturais, a adoção de políticas de reciclagem faz-se fundamental para alcançar o desenvolvimento sustentável. Neste cenário, apesar dos resíduos de construção e demolição (RCD) possuírem alto potencial de reciclagem, a estes sempre foi dispensado o tratamento de lixo. Além disso, os estudos realizados visando à reciclagem dos RCD mostram-se bastante concentrados na produção de agregados para a fabricação de concreto e para a aplicação em pavimentação. Diante disso, neste trabalho procurou-se definir uma nova aplicação para os resíduos de construção e demolição reciclados (RCD-R), buscando caracterizar suas propriedades geotécnicas como material de construção e verificando o seu desempenho como material de preenchimento de estruturas de solo reforçado. Ensaios de caracterização, de resistência ao cisalhamento e ensaios de arrancamento de geogrelha revelaram que o RCD-R apresentou baixos coeficientes de variação nas suas propriedades e excelente comportamento mecânico, o que justifica a sua utilização na aplicação proposta. / The intense population growth brings some environmental concerns due to the need of exploitation of natural resources, and the adoption of recycling policies is basic principle to reach sustainable development. In this scenario, however, the high potential of recycling the construction and demolition wastes (CDW) has been ignored. Moreover, studies focus mainly on the recycling of CDW for the production of aggregates for use in pavements and concrete. The present study deals with a new application of the recycled construction and demolition waste (RCDW) as backfill of reinforced soil structures. Characterization, direct shear and pullout tests on geogrids has depicted that RCDW shows low coefficients of variation of its properties and excellent mechanical behavior that justify its use for proposed application.

O bom desempenho de uma estrutura de solo reforçado depende fundamentalmente da interação entre o solo de aterro e o elemento de reforço. A utilização de solos coesivos pode causar efeitos negativos à estabilidade da estrutura. Um elevado percentual de partículas finas na composição do solo pode favorecer ao desenvolvimento de pressões da água intersticial, devido à diminuição da sua capacidade de drenagem. Um efeito indesejado do desenvolvimento de pressão positiva é a diminuição da força necessária, para promover o arrancamento do reforço inserido na zona resistente do maciço de solo reforçado. Os ensaios de arrancamento são considerados os mais adequados para a quantificação da força de arrancamento aplicada às geogrelhas. Neste trabalho são apresentados e discutidos os resultados de ensaios de arrancamento realizados em laboratório com uma caixa de ensaios de pequenas dimensões. O solo utilizado nos ensaios trata-se de uma areia argilosa de baixa plasticidade, onde mais de 35% de suas partículas possuem diâmetro inferior a 0,075 mm. O elemento de reforço ensaiado é uma geogrelha uniaxial, com resistência longitudinal à tração de 110 kN/m. Foram aplicados três níveis de tensão normal na interface solo-geogrelha: 25, 50 e 100 kPa. Os teores de umidade adotados foram 12,6%, 14,6% (wot) e 16,6%. Os resultados dos ensaios comprovaram a influência que a variação das condições de umidade exerce sobre a resistência ao arrancamento de geogrelha. Verificou-se que maiores níveis de sucção matricial resultam em maiores forças de arrancamento. Dentre os trinta ensaios realizados, em apenas três foram registradas pressões positivas da água intersticial, embora não tenha influenciado nos valores de resistência ao arrancamento. / The behavior of soil reinforcement structure depends on backfill soil and reinforcement interaction. The use of cohesive soils can cause negatives effects in structure stability. High quantities of fine particles in composition of soils can induce the pore water pressure development due to draining capacity reduction. Therefore, a negative effect of positive pore water pressure development is the reduction of reinforcement pullout forces embedded in resistant zone of soil reinforcement backfill. For designers, the better determinations of geogrids pullout forces are by pullout tests. This paper presented and describes the evaluation of small box pullout tests results conducted in lab. Low plasticity sand clayed was used in tests, which is composed by 35% of clay and silt particles. The reinforcement tested was a high strength uniaxial geogrid, with resistance of 110 kN/m. The tests are conducted with three different level normal stresses (25, 50 and 100 kPa), and samples compacted with 12,6%, 14,6% e 16,6% to moisture contents of Proctor tests. Pullout tests results showed the influence of moisture conditions in the geogrid pullout resistance. It was found that the highest matritial suction values resulted in the highest ultimate pullout resistance. Positive pore water pressure was obtained in three pullout tests though it did not influence in pullout strength results.