Última alteração: 2021-02-25
Resumo
Em situações de campo, há muitos relatos de retração significativa de geocompostos bentoníticos (GCLs) em liners de aterros sanitários. Estudos indicam que ciclos de umedecimento e secagem causados pela exposição à variação de temperatura são uma das causas potenciais para a retração dos GCLs com relatos de distanciamento de até 1,2 m entre emendas de sobreposições de GCLs. O objetivo deste trabalho é identificar os efeitos de retração de GCL, sob efeitos de ciclos de umedecimento e secagem, em relação à magnitude das deformações, e a relação com o teor de umidade inicial do GCL. Os corpos de prova de GCL foram cortadas com 700 mm (direção longitudinal) por 350 mm de largura, sendo que as extremidades da largura foram ancoradas, de modo a representar a situação de ancoragem em campo. Foi estabelecido um ciclo de umedecimento (nos teores de umidade pré-estabelecidos) por 8 horas e secagem em estufa com circulação de ar até completar 24 horas. O GCL analisado nessa pesquisa é composto por suporte em geotêxtil não tecido com núcleo em bentonita cálcica (ativada com carbonato de sódio) e geotêxtil tecido de cobertura, fixados por processo de agulhamento. Neste trabalho avaliou-se o efeito de diferentes teores de umidade de hidratação inicial (25, 50 e 100%) nos valores de retração de um GCL produzido com bentonitas cálcicas. Os resultados mostraram que houve um efeito significativo de retração de até 35%, correlacionado aos valores iniciais de teor de umidade do GCL. Os ensaios realizados até 20 ciclos de hidratação-secagem mostraram que o limite de retração não foi atingido.
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