On the compatibility and theoretical equations for mixtures of tropical soils and bentonite for barrier purposes.
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2018
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Resumo
Vast regions of the globe are covered by tropical soils, increasing the perspective of using them for barrier
design at solid/liquid disposal facilities. They comprise diverse pedological taxonomies, but have common features,
specially the dominant mineral composition of quartz, kaolinite clay and Fe-Al-Mn oxides/hydroxides. Despite the vast
occurrence, sometimes tropical soil samples may not be suitable for barrier purposes, which can be overcome using
bentonite as additive, provide that technical evaluations are adopted. An important technical issue to be addressed is the
compatibility between the barrier materials and the liquids to be disposed. Compatibility studies usually involve laboratory
testing using direct and indirect methods, which were involved in this research. The indirect studies involved modified
Atterberg limits and the direct approach was developed using direct permeation. The tropical soil samples were selected to
be in different weathering stages, considering the laterization degree. The chosen bentonite content to compose the
mixtures was 3, 6, 9 and 12% on a dry weight basis. The elected chemical solutions for these studies were: calcium chloride
(CaCl2), nitric acid (HNO3), sodium hydroxide (NaOH), ethanol (C2
H5OH) and tap water. As a summary, the main research
objectives were: (1) comparison between direct and indirect methods for compatibility evaluation; (2) assessment of the
influence of the bentonite content on the compatibility of tropical soil samples; (3) investigation of the influence of the
laterization degree on compatibility and (4) evaluation of theoretical equations to predict the compatibility of these samples
through back analysis. The results indicate that: indirect and direct methods are similar from a qualitative point of view;
bentonite is more sensitive to chemicals than the natural soil components; the laterization degree is not so influent on the
compatibility and good compatibility predictions were obtained with the proposed theoretical equations.
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Clayey barriers, Compatibility predictions, Modified Atterberg limits
Citação
MORANDINI,T. L. C.; LEITE, A. do L. On the compatibility and theoretical equations for mixtures of tropical soils and bentonite for barrier purposes. Soils and Rocks, São Paulo, v. 41, n. 3, p. 345-357, set./dez. 2018. Disponível em: <http://www.soilsandrocks.com.br/soils-androcks/SR41-3_345-357.pdf>. Acesso em: 10 mar. 2020.