RESUMO Esta pesquisa teve por objetivo principal avaliar a influência do tipo de geotêxtil de reforço, solo, posição de inserção do reforço geossintético e energia de compactação no comportamento mecânico de solos reforçados com geotêxtil. Esta avaliação foi baseada nos resultados dos ensaios de Resistência à Compressão Não Confinada (RCNC) e de Resistência ao Cisalhamento Direto (τpico). Para a avaliação da influência desses fatores no comportamento mecânico, utilizaram-se testes não-paramétricos, conforme o número de amostras de cada fator. Foram aplicados os testes de Kruskal-Wallis para os fatores “solo” e “tipo de geotêxtil” e de Mann-Whitney para os fatores “posição de inserção do geotêxtil” e “energia de compactação”. De um modo geral, os resultados não mostraram diferenças significativas de RCNC dos solos reforçados comparativamente aos não reforçados. Para o cenário que envolveu a avaliação do comportamento de diferentes solos reforçados, a diferença entre os resultados foi dependente da mobilização do reforço. Em relação aos distintos geotêxteis aplicados e às diferentes posições de localização destes elementos, notou-se que tais fatores não exerceram efeitos estatisticamente significantes sobre o parâmetro RCNC. Quando analisadas as diferentes energias de compactação, observou-se que o aumento dessa energia levou ao incremento do contato do geossintético com o solo, aumentando as forças de atrito de interface e gerando maiores acréscimos de RCNC. Quando analisados os resultados referentes aos ensaios de resistência ao cisalhamento direto, percebeu-se que as mudanças de energia de compactação, solo e tipo de geotêxtil não apresentaram diferença estatisticamente significante sobre o parâmetro τpico e que a inserção de diferentes geotêxteis nos distintos solos estudados não promoveu completa interação entre os materiais, proporcionando a deficiência do atrito de interface.

ABSTRACT The main objective of this research was to evaluate the influence of the type of reinforcement geotextile, soil, geosynthetic reinforcement insertion position and compaction energy on the mechanical behavior of geotextile-reinforced soils. This evaluation was based on the results of the Unconfined Compressive Strength (UCS) and Direct Shear tests. In order to evaluate the influence of these factors on the mechanical behavior, non-parametric tests were used, according to the number of samples of each factor. The Kruskal-Wallis tests were applied for the factors “soil” and “type of geotextile” and the Mann-Whitney tests for the factors “position of insertion of the geotextile” and “compaction energy”. In general, the results did not show significant differences in UCS of reinforced soils compared to unreinforced ones. For the behavior of different reinforced soils, the difference between the results was dependent on the reinforcement mobilization. Regarding the different geotextiles applied and the different location positions of these elements, it was noted that such factors did not exert statistically significant effects on the UCS parameter. When the different compaction energies were analyzed, it was observed that the increase in this energy led to an increase in the contact of the geosynthetic with the soil, increasing the interface friction forces and generating greater increases in UCS. When analyzing the results referring to the direct shear strength tests, it was noticed that the changes in compaction energy, soil and type of geotextile did not present a statistically significant difference on the parameter and that the insertion of different geotextiles in the different soils studied did not promote complete interaction between the materials, providing the deficiency of interface friction.

Abstract This paper presents a numerical evaluation, using PLAXIS 2D finite element software, of the effects of varying the distance of the heavy compaction from the face in a geosynthetic reinforced soil wall (GRSW). The main effects studied were the tensions in the reinforcements and the horizontal deformations of the face, including the influence of the type of shear strength envelope (total stresses or effective stresses) of the soil. In this study, a young gneiss residual soil (silty sand) was studied to obtain the grain size distribution, index properties and parameters of strength and deformability. This soil was considered for backfill in hypothetical sections of GRSW. The numerical results contributed to a better understanding of the GRSW behaviour, with evaluations closer to real field conditions. In the analyses carried out, when increasing the heavy compaction distance from the face, there are tendencies pointing to the reduction of the tensions in the reinforcements, displacement toward the interior of the soil mass of the points at which the maximum reinforcement tension occurs and reduction of the horizontal deformations of the face.

RESUMO São vários os fatores (geométricos, mecânicos e de carregamento) que podem influenciar no dimensionamento do pavimento flexível e no seu desempenho quanto ao aparecimento de fissuras por fadiga. Por isso, os métodos mecanístico-empíricos para o dimensionamento são amplamente aceitos e utilizados no âmbito da engenharia de pavimentação. Entretanto, para a análise mecanística existe uma gama de modelos de fadiga que podem proporcionar diferentes dimensionamentos do pavimento. Este estudo visou analisar a sensibilidade do desempenho à fadiga do revestimento asfáltico de acordo com dados derivados de um dimensionamento mecanístico-empírico do pavimento e levando em consideração diferentes modelos de fadiga. As seguintes variáveis foram consideradas nos modelos de fadiga: as propriedades mecânicas dos materiais estruturais, as espessuras das camadas estruturais e a carga aplicada à estrutura. As misturas asfálticas de projeto contempladas na pesquisa foram definidas de acordo com o método de projeto de mistura Marshall, enquadradas em duas distintas faixas granulométricas aplicáveis ao concreto asfáltico com ligante polimérico. O protocolo mecanístico-empírico envolveu o pré-projeto das estruturas do pavimento utilizando o método empírico do Departamento Nacional de Infraestrutura de Transportes (DNIT) e sua análise mecanística utilizando o programa de computador Elsym5, o qual considera que as camadas horizontais são formadas por materiais elástico-lineares e isotrópicos. Os resultados mostraram que o desempenho à fadiga e o dimensionamento da camada de revestimento asfáltico variaram conforme os modelos de fadiga aplicados nos diferentes cenários. Porém, a sensibilidade do desempenho à fadiga do revestimento asfáltico determinado por esses modelos, diante das variações dos fatores estudados, foi aproximadamente a mesma. Assim, concluiu-se que a fadiga dos revestimentos asfálticos foi mais sensível à variação da espessura da camada de revestimento asfáltico do que à variação do valor de carga aplicada, seguidas do módulo de resiliência do solo do subleito.

ABSTRACT In the new Brazilian mechanistic-empirical design method of asphalt pavements, MeDiNa, the characterization of permanent deformation (PD) for the selection of soils and gravel is based on tests performed with at least 150,000 loading cycles for each of the nine specimens indicated in the DNIT standard. Despite providing information about the material behavior under a wide range of testing conditions, the experimental program related to these PD characterizations is time consuming and it is believed that it can be optimized. This paper evaluates the influence of the number of loading cycle applications on the characterization of the materials. For this purpose, seven materials were analyzed at their optimum moisture content (OMC) and one of them was also compacted in a condition above the OMC, in a total of eight data sets. Statistical regression analyzes were performed to identify the parameters of the predictive model for different numbers of cycles and the PD predictions for the different materials were compared. From these results, simulations were performed in the MeDiNa software to predict the performance of the materials. Four different N values were evaluated, considering 150,000 cycles as reference: discarding the 500 first cycles, but considering the PD accumulated in that interval; discarding the 500 first cycles and considering the PD accumulated in that interval; final N of 80,000; and final N of 100,000. For the analyzed materials, no significant differences were observed in the PD prediction, even considering tests with 50,000 or 70,000 cycles less than the 150,000 cycles required in the standard. This indicates that, although characterization is recommended following standardized procedures, the experimental program of the current PD standard can possibly be significantly optimized by reducing the number of cycles applied to materials in laboratory tests. This possibility must be analyzed for each material.

Resumen Este trabajo tuvo como objetivo el análisis de la influencia de diferentes metodologías para la determinación de la gravedad específica máxima del método de dosificación SUPERPAVE de mezclas asfálticas en caliente.El análisis comparativo incidió sobre los parámetros volumétricos, en la elección de la granulometría del proyecto, y por consiguiente, sobre los respectivos contenidos de ligante asfaltico del proyecto de las mezclas asfálticas estudiadas.Para las especificaciones de la investigación no hubo diferencias significativas en los contenidos de ligante del proyecto obtenidos por medio de las dos metodologías de determinación de la gravedad específica máxima, con respecto a los diferentes valores de gravedad específica máxima determinadas según cada uno de los diferentes métodos utilizados. Desde un punto de vista práctico, la adopción de cualquiera de los métodos interfirió poco en la dosificación del método Superpave para la mezcla asfáltica proyectada, lo que pude corresponder a una ventaja del método trabajado en investigaciones similares basadas en el método de dosificación Marshall, donde se evidencia la sensibilidad del procedimiento para la determinación del contenido del ligante asfaltico del proyecto al tipo de gravedad específico máximo utilizado.

Abstract This study aimed to analyze the influence of different methodologies to determine the maximum specific gravity on the Superpave mix design method. The comparative analysis focused on the volumetric parameters, on the choice of the design particle size and, consequently, on the respective design asphalt binder contents of the studied asphalt mixtures. Regarding the particularities of the research, there were no significant differences in the design binder contents obtained using the two adopted methodologies for determining the maximum specific gravity. From a practical point of view, the adoption of any of the methods interfered little with the results of the application of the Superpave mix design method. This fact demonstrates a quality of this method since similar researches based on the Marshall design method evidences the sensitivity of the protocol for determining the asphalt binder content in relation to the used type of maximum specific gravity.

Abstract This article addresses an analysis of the Load Equivalency Factor (LEF) for off-road trucks. A new LEF curve for single axles with dual wheels covering trucks from 6.0 to 151.42 tons per axle is proposed, converting various magnitudes of damage from wheel loads to damage caused by the standard axle load of 8.2 tons. Then, this damage ratio was raised to the exponent proposed by Pereira (1992), and LEF for the considered loads was obtained. In the determination of LEF from the structural response of the subgrade, it was confirmed that LEF values did not suffer significant variations with the various parameters adopted, encompassing variations in the axle loads between 6 and 151.42 tons, tire pressures of 80.0, 100.0 and 120.0 psi, as well as five different pavement structures. In the study, LEF remained stable even in pavement structures with low and high axle capacities. In order to validate the results, the resulting factors were then compared with those proposed by DNIT (2006), displaying a coefficient of determination of 0.99. The conclusion is that pavements for off-roads trucks can be designed using the procedure recommended by DNIT (2006) for flexible pavement, without extrapolation of the respective LEF curve.

Abstract This article proposes a testing device to quickly and reliably estimate the gas permeability of bentonite-based clay barriers used in landfill cover systems. The testing methodology is based on a transient gas flow regime that passes through the barrier, therefore not requiring the use of sophisticated equipment that aim to maintain constant differential pressure and measure the gas flow, common requirements for testing methods under a permanent flow regime. To confirm the feasibility of the proposed technique, tests were performed on a pure hydrated bentonite layer, which subsequently encompassed samples of geosynthetic clay liner (GCL) at different moisture contents. Geosynthetic clay liners are often selected as a part of the barrier layer for cover systems in solid waste landfills to prevent infiltration of rainfall and migration of biogas into the atmosphere. The results confirmed the equipment reliability and differentiate the different responses of the gas flow barriers studied, considering their different compositions and different moistures.

RESUMO Este trabalho visou avaliar o potencial de aplicação técnica de um estabilizante resultante da mistura íntima de pó de escória oxidante de aciaria elétrica moída e cinza volante, visando à melhoria das propriedades de engenharia de solos para fins de aplicação em estradas florestais. Essa avaliação foi empreendida por meio de um programa experimental de ensaios laboratoriais destinados a classificar os solos e as misturas destes com o estabilizante proposto segundo a metodologia MCT (Miniatura, Compactado, Tropical). As proporções das misturas dos resíduos foram de 10% e 20% da massa seca total das combinações solo-resíduos, e as porcentagens de escória de aciaria moída foram de 75%, 87,5% e 100% em relação à massa seca total das misturas dos resíduos. Para as particularidades da pesquisa e por meio da classificação MCT, foi possível demonstrar o potencial de viabilizar tecnicamente o aproveitamento de resíduos siderúrgicos na composição das vias de tráfego florestais, realçando a relevância da proposta no atendimento à necessidade de empresas siderúrgicas de conferirem uma destinação sustentável de seus resíduos e à necessidade das empresas florestais de suprirem, com materiais de baixo custo, as significativas demandas de sua malha viária não pavimentada.

ABSTRACT This work aimed to evaluate the potential application of a stabilizer derived from the intimate mixture of powder electric arc furnace oxidizing slag and fly ash, aiming at the improvement of soil engineering properties for enforcement purposes on forest roads. This evaluation was undertaken by means of an experimental program of laboratory tests to classify soils and mixtures of these with the proposed stabilizer according to the MCT (Miniature, Compacted, Tropical) methodology. The proportions of waste mixtures were 10% and 20% of the total dry mass of soil-waste combinations and percentages of ground steel slag were 75%, 87.5% and 100% relative to total dry mass of waste mixtures. It was shown the potential to technically enable the use of steel waste in the composition of forest roads, emphasizing the relevance of the proposal in meeting the need of steel companies to confer a sustainable destination for the waste and the need of forest companies to meet, with low-cost materials, the significant demands of their unpaved road network.

RESUMOEsta pesquisa apresenta uma contribuição à modelagem de um aplicativo computacional empregando um método de desempenho de serventia a estradas não pavimentadas, visando ao gerenciamento de atividades de manutenção/restauração de camada de revestimento primário. A metodologia proposta consistiu em inspeções de campo, nos períodos seco (abril a setembro) e chuvoso (outubro a março), em que foram realizadas avaliações objetivas, visando ao inventário de defeitos e respectivas densidades e níveis de severidade. Para auxiliar a classificação funcional dos trechos viários analisados e a determinação do defeito com maior influência sobre a condição de serventia dessas vias, foi implementado, na linguagem Visual Basic for Applications (VBA) no software Microsoft Excel, o método de desempenho de serventia proposto por Silva (2009). Com o emprego do aplicativo computacional proposto, foi possível identificar entre os defeitos analisados em campo, através do índice de serventia da unidade amostral por tipo de defeito (ISUdef), qual foi o que teve maior influência sobre a determinação do índice de serventia relativo por trecho viário (IST). Os resultados possibilitam a conclusão de que o aplicativo computacional Road obteve resultados satisfatórios, visto que o critério de avaliação objetiva aplicado aos trechos viários inspecionados denota coerência quanto às condições de suas serventias.

ABSTRACTThis study presents a contribution to the modeling of a computer application employing a method of serviceability performance for unpaved roads, aiming the management of maintenance/restoration activities of the primary surface layer. The proposed methodology consisted of field inspections during dry (April to September) and rainy (October to March) periods, during which objective evaluations were performed to survey of defects and their densities and degrees of severity. To aid the functional classification of analyzed road sections and the determination of the defect with major influence on the serviceability of these roads, the method of serviceability performance proposed by Silva (2009)was implemented in the Visual Basic for Applications (VBA) language in Microsoft Excel software. With the use of the computer application proposed it was possible to identify among the defects analyzed in field, through the index of serviceability of the sampling unit per defect type (ISUdef), which one had the greatest influence on determining the relative serviceability index per road section (IST). The results allow us to conclude that the computer application Road achieved satisfactory results, since the objective evaluation criteria applied to road sections denotes consistency regarding their serviceability.

Esse artigo apresenta os resultados de um estudo experimental que visa a avaliar o efeito do desgaste superficial sobre as propriedades de atrito de interfaces geossintéticas constituídas por geomembranas. Os ensaios foram realizados em equipamento de plano inclinado e os resultados demonstram as diferentes sensibilidades das interfaces, testadas ao processo de desgaste. Para os tipos particulares de interfaces consideradas no programa experimental, constatou-se que o desgaste superficial pode aumentar, diminuir ou manter as propriedades originais de atrito da interface geossintética, repercutindo, diretamente, sobre a estabilidade desta sob condição de serviço.

This article presents the results of an experimental study which aimed to evaluate the effect of surface wear on the friction properties of geosynthetic interfaces constituted of geomembranes and geospacers. The tests were performed in ramp test device, and the results showed the different sensitivities of the interfaces to the wear process. For the particular types of interfaces considered in the experiment, the surface wear can increase, decrease or maintain the original friction properties of the geosynthetic interface, with direct effects on the stability under service condition.