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26 results on '"Valentin, Clever Aparecido"'

7. Service Life of Some Hdpe Geomembranes

Author

Lavoie, Fernando Luiz, primary, Kobelnik, Marcelo, additional, Valentin, Clever Aparecido, additional, Lopes, Maria de Lurdes, additional, Palmeira, Ennio Marques, additional, and Lins da Silva, Jefferson, additional

Published
2023
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8. Mechanical and Thermoanalytical Study of Polypropylene Geomats Exposed in the Field and the Laboratory.

Author

Lins da Silva, Jefferson, Valentin, Clever Aparecido, Kobelnik, Marcelo, Pedroso, Gabriel Orquizas Mattielo, Aparício-Ardila, Maria Alejandra, Araújo Júnior, Luiz Paulo Vieira de, and Luz, Marta Pereira da

Subjects
*TENSILE tests, *DIFFERENTIAL scanning calorimetry, *POLYPROPYLENE, *HYDROELECTRIC power plants, *SOIL erosion, *TENSILE strength
Abstract

A Hydroelectric Power Plant (HPP) presents erosion problems on reservoir slopes and margins. Geomats are a biotechnical composite technology increasingly used to protect soils against erosion. Survivability or durability of geomats is essential for successful application. This work analyses the degradation of geomats exposed in the field for more than six years. These geomats were used as erosion-control treatment in a slope at HPP Simplício in Brazil. The degradation of the geomats in the laboratory was also analysed through exposure in a UV ageing chamber for 500 h and 1000 h. Degradation was quantitatively evaluated by testing the tensile strength of the geomat wires and thermal tests such as thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed that the geomat wires exposed in the field had a greater decrease in resistance compared to the samples exposed in the laboratory. In the samples collected in the field, it could be observed that the degradation of the virgin sample occurred earlier than in the exposed samples, contrary to what was observed in the TG tests carried out with the samples exposed in the laboratory. The DSC analysis showed that the samples had similar behaviours for the melting peaks. This evaluation of the wires of the geomats was presented as an alternative to analysing the tensile strengths of discontinuous geosynthetic materials such as the geomats. [ABSTRACT FROM AUTHOR]

Published
2023
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23. A New Small-Scale Test Apparatus for Modeling Buried Pipes under Axial or Lateral Soil Loading

Author

Franco, Yara Barbosa, Silva, Jefferson Lins da, and Valentin, Clever Aparecido

Abstract

This article describes a new small-scale test apparatus (2.10 m long, 0.50 m wide, and 0.50 m high) to study the behavior of small-diameter buried pipes subjected to both axial and lateral soil loading. The developed equipment innovates by not requiring a pullout system or additional objects inside the soil to apply the soil load on the pipe. Instead, soil loading is achieved by a simple mechanism of tilting the test box using an inexpensive manually controlled uplift system. The proposed apparatus aims to investigate the influence of different surcharge loads, soil cover ratios, soil densities, and pipe diameters. Besides, a camera support bolted to the apparatus structure enables image acquisition during testing with negligible relative movement between the digital camera and the apparatus. The applicability of this new facility is demonstrated through two model tests carried out to study the influence of soil density in soil/pipe response for a pipe subjected to lateral soil loading and with a soil cover ratio of 3.55. Results are presented in terms of pipe strains and soil displacements, which were measured using the digital image correlation technique.

Published
2020
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26. Chemical characterization of polyethylene geomembranes by chromatography coupled to mass spectrometry using multivariate tools

Author

Valentin, Leonardo Antonio, Valentin, Clever Aparecido, Kobelnik, Marcelo, and Lins da Silva, Jefferson

Abstract

Geomembrane is a type of material used in civil engineering and environmental engineering works for the protection and recovery of the environment. Five geomembranes commercially obtained from three Brazilian companies were chemically characterized. The Gas Chromatography-Mass Spectrometry (GC-MS) technique was used to determine and identify the compounds Semivolatile Organic Compounds (SVOCs) and Volatile Organic Compounds (VOCs) based on their mass and spectrum (fragmentation) in order to characterize the materials and multivariate analysis tools were applied. Moreover, 211 compounds were selected for SVOCs and 59 compounds for VOCs. Considering the 211 compounds, 159 met the p-value criterion <0.05. For the 159 compounds, 130 met the cut-off criterion of 2.0 for the fold change analysis and were considered in the study. Regarding VOC compounds, from the 59 compounds considered, 25 met the p-value criteria <0.05 and 15 for the cut-off 2.0 criteria for fold change analysis. The combination of chromatographic determination with multivariate analysis was applied and showed to be an excellent tool for chemical characterization and the differentiation between the five groups can be observed. This information can be useful for these techniques in routines for material quality control and for geosynthetics databases.

Published
2021
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