Benedito de Souza Bueno

Failure Mechanisms in Sand over a Deep Active Trapdoor

An experimental testing program was undertaken to investigate failure mechanisms induced by the active movement of a deep rectangular trapdoor underlying a granular soil. Reduced-scale models were tested under normal gravity as well as under an increased gravitational field using a centrifuge facility. Some models were used to evaluate the performance of both flexible and rigid pipes undergoing a localized loss of support. Failure mechanisms in the longitudinal direction of the models were characterized by a single, well-defined failure surface that developed within the limits of the trapdoor. However, failure mechanisms in the transverse direction of the models were characterized by multiple failure surfaces extending outside the limits of the trapdoor. Significant dilation of the soil located immediately above the trapdoor was identified in the failure of the models. The pattern of the failure mechanisms was found to be affected by the stress level and backfill density. Higher stress levels were found to lead to well-developed failure zones. The influence of backfill density was found to be more relevant in models involving flexible pipes. Pipes embedded within loose backfill were severely damaged after loss of support, while pipes embedded in dense backfill experienced negligible deformations. These results indicate that damage to pipelines caused by ground loss of support can be significantly minimized by controlling the compaction of the fill.

Estudos laboratoriais do comportamento de um soloresidual arenoso reforçado com fibras de polipropileno, visando à aplicação em Estradas Florestais

Este trabalho teve como objetivo analisar o comportamento mecânico da mistura de um solo residual jovem de textura predominantemente arenosa reforcado com fibras de polipropileno, com vistas a aplicacao em estradas florestais. Como ponto de partida, determinou-se, mediante os resultados de ensaios de compressao nao-confinada, realizados em corpos-de-prova compactados na energia do ensaio Proctor Normal, que o quantitativo de 0,75% de fibras com 20 mm de comprimento foi a combinacao responsavel pelo maior ganho de resistencia. Com a mistura solo-fibra composta por essa combinacao, foram realizados ensaios triaxiais do tipo CID/Sat em corpos-de-prova compactados na energia anteriormente referida. Atraves desta pesquisa, foi possivel avaliar: (i) a influencia da variacao da umidade nos parâmetros de resistencia mecânica do solo e das misturas solo-fibra e (ii) a influencia das fibras nos parâmetros de resistencia ao cisalhamento do solo em estudo. Analisando os resultados, pode-se concluir que o uso de fibras de polipropileno promoveu um ganho da ordem de 110% na resistencia a compressao nao-confinada e de 560% na coesao de intercepto do solo estudado.

A Novel Construction Method for Buried Pipes using Geosynthetics

This paper describes preliminary results of a novel construction method developed to reduce the vertical stresses on buried pipes. The method, named Geovala ( vala means trench in Portuguese), involves the use of geosynthetic reinforcement layers placed within the soil mass, above the crown of the buried pipe. The main objective is to redistribute the vertical stresses acting on top of the pipe to the lateral surrounding soil. The construction methodology involves not only trench installation but also of construction of protecting structures. An experimental testing program was conducted to evaluate this system. The results obtained from tests conducted in both small- and large-scale facilities show that vertical stresses acting on top of the pipe can be significantly reduced by using geosynthetic reinforcement. The variables governing the design include the layout of the geosynthetics (length and position of the reinforcement in relation to the top of the structure), the soil type, the soil density, and the stiffness of the geosynthetic inclusion. It is expected that implementation of this construction technique will allow the use of more flexible pipes as well as their placement at more shallow depths. This can lead to significant cost savings in projects involving pipes in civil and environmental applications.

Wood cross-arms coated with polyurethane resin - tests and numerical simulations

Brazils electric power utilities have commonly employed native timbers as the main material for manufacturing cross-arms for distribution lines. However, the increasingly high costs of these timbers and Brazils new environmental laws have contributed to change this situation, spurring research on new materials for application in transmission and distribution systems. This paper discusses two reforested wood species, Pinus elliottii and Eucalyptus citriodora, coated with castor oil-based polyurethane resins, as an alternative material for distribution line cross-arms, from the standpoint of their mechanical and electrical properties and their low cost. Numerical simulations and a complete description of the entire coating process are also part of this work.

USO DA CROMATOGRAFIA GASOSA PARA AVALIAÇÃO DA DIFUSÃO EM MEMBRANA DE POLIETILENO DE ALTA DENSIDADE (PEAD) EM CONTATO COM HIDROCARBONETO

Os constantes vazamentos de combustiveis derivados do petroleo nos postos de abastecimento tem gerado grande preocupacao em diversos paises do mundo. Tais combustiveis apresentam, em sua composicao, compostos orgânicos, entre eles os hidrocarbonetos poliaromaticos (HPA) nocivos a saude humana. Este trabalho avaliou o estudo da eficiencia de uma camada de impermeabilizacao constituida por uma geomembrana de Polietileno de Alta Densidade (PEAD) de 2,5 mm de espessura. O estudo baseou-se em analises do processo difusivo na geomembrana intacta por meio de um permeâmetro desenvolvido para tal finalidade. A membrana foi colocada no meio do sistema para separar duas fases, a saber: solo local impregnado com oleo diesel em uma face e agua pura na face oposta. A tecnica de cromatografia foi utilizada para avaliar a contaminacao na agua pura. As analises foram realizadas mensalmente num periodo total de 6 meses de pesquisa. Os resultados mostraram que a membrana apresentou desempenho menos satisfatorio para os compostos antraceno e naftaleno. Apesar disso, os resultados mostraram que a membrana de PEAD e uma boa alternativa para prevencao da contaminacao da agua e do solo pelos compostos estudados pelo periodo aproximado de um ano tendo-se em vista o desempenho no periodo estudado. Palavras-chave: hidrocarbonetos, difusao, cromatografia gasosa. ABSTRACT The constant petrol fuel leak in gas stations has caused concern in many countries around the world. Those fuels have toxic organic compounds in their composition, like Polycyclic Aromatic Hydrocarbons (PAH), which are harmful to the human health. In this work the efficiency of the protection layer with a High Density Polyethylene (HDPE) membrane of 2.5 mm thickness was evaluated. The study was based in the diffusive process in the intact membrane by a permeameter developed to evaluate the diffusive process. The membrane was putted in the middle of the system to separate two sides: a local soil impregnated with diesel oil (in one side) and pure water (in the other side). The chromatography technique was conducted to evaluate the contamination in the pure water. The analyses were made monthly in a total period of 6 months of research. The results tests show that the membrane was less effective to antracene and naphthalene compounds. Despite that, the results showed that the HDPE membrane is a good alternative to prevent contamination of water and soil by the compounds under study up to one year, based on the performance in the time of study. Keywords: hydrocarbons, diffusion; gas chromatography.

Behavior of Impregnated Paving Geotextiles: Study of Optimum Tack Coat Rate

AbstractPaving geotextiles are becoming increasingly used in highway construction overlays in order to recover cracked asphalt pavements. In antireflective cracking systems, the geosynthetic should have the ability to absorb and retain the asphalt tack coat to effectively bond the system to the existing pavement and overlay. However, the type and rate of tack coat impregnation can significantly influence the reinforcement mechanism, potentially leading to early overlay failure. Stiffness has been identified as the governing property to quantify the potential contribution of the interlayer to the asphalt overlay strength. In addition, the overall behavior of reinforced asphalt pavements may also be incorporated with an increased tensile strength of the geosynthetic. With the purpose of quantifying the often significant changes in the mechanical behavior of paving geosynthetics that occur after bitumen impregnation, a series of tensile strength tests were conducted in this study using nonwoven geotextiles w...

Field Performance of a Full-Scale Retaining Wall Reinforced with Nonwoven Geotextiles

Retaining walls in Brazil have often been reinforced using nonwoven geotextiles instead of other reinforcement inclusions such as geogrids, woven geotextiles, and metallic reinforcements. This approach has several advantages such as ease of construction, expediency, and significant cost reduction. However, current lack of field data on the field performance of nonwoven geotextile-reinforced structures, mainly regarding displacements, has prevented their utilization in critical structures. Observation of the behavior of full-scale structures and a further characterization of the materials are needed to gain understanding of the behavior of nonwoven geotextile-reinforced soil structures. Accordingly, a series of nonwoven geotextile-reinforced soil structures was built and instrumented to analyze their behavior. This paper presents the results of a full-scale field monitoring program and associated finite element analyses conducted for a nonwoven geotextile-reinforced soil wall. The results show that current design methods provide conservative evaluation of the overall stability of the structure. The results of the numerical simulation indicate that FEM is a useful tool to predict the response of structures reinforced with geosynthetics. Monitoring results were found to be in agreement with those obtained in the numerical simulation.

Avaliação de recomendações normativas sobre o uso de ensaios no controle de qualidade de fabricação de geossintéticos

A utilizacao de materiais polimericos designados por geossinteticos tem aumentando significativamente nos ultimos anos na Engenharia Civil. Para desempenhar adequadamente a funcao para a qual foram projetados, os geossinteticos devem ser submetidos a um rigoroso processo de controle de qualidade durante a fabricacao. Discussoes sobre a frequencia e os principais tipos de ensaios de laboratorio utilizados nesse processo de controle para dois tipos de geossinteticos, os geotexteis e as geomembranas, os materiais mais utilizados da famila dos geossinteticos, sao abordados no presente trabalho. As analises efetuadas com base em normas disponiveis no Brasil, nos EUA e na Europa mostram que no cenario nacional nao ha recomendacoes normativas sobre o controle de qualidade para a maioria das aplicacoes de geotexteis e geomembranas, sendo o assunto pouco discutido na literatura tecnica. No cenario internacional, as normas Europeias se destacam como o conjunto de praticas mais completo para ensaios de controle de qualidade de fabricacao, considerando os diversos tipos de aplicacao dos geossinteticos na Engenharia Civil.

The effects of weathering exposure on the physical, mechanical, and thermal properties of high-density polyethylene and poly (vinyl chloride)

This paper presents results describing the physical, mechanical, and thermal properties (melt flow index - MFI and oxidative induction time - OIT) of high density polyethylene and poly (vinyl chloride) after weathering exposure (6, 12, 18, and 30 months). The materials exposed were geomembranes of two thicknesses: 1.0 and 2.0 mm (PVC) and 0.8 and 2.5 mm (HDPE). The climate parameters (average) obtained were 25 °C (temperature), 93 mm (precipitation), 66% (relative humidity), and 19 MJ/m

Latossolo vermelho-amarelo reforçado com fibras de polipropileno de distribuição aleatória: estudo realizado com amostras de grandes dimensões

This study was directed to the geotechnical characterization of the material called fibersoil for civil engineering purposes. One soil was used throughout the study, encompassing a clayey soil, and can be evaluate, experimentally, from resulted of tests accomplished in samples of great dimensions, the mechanical behavior of the soil and fibersoil. For these materials, the following tests had been accomplished: (i) tests with Marchetti dilatometer, and (ii) tests with external loads evenly distributed, applied to the surface of the flat land. From the experimental testing program data it was possible to evaluate the influence of the fibers in the load capacity of the soil studied.