Avaliação dos fatores que influenciam a hidratação de GCLs em subleitos lateríticos

Abstract

Currently, the biggest concern in the performance of geosynthetic clay liners (GCLs) applied in municipal solid waste landfills is in the hydration behavior of this material. Recent studies have shown that the GCLs hydration process from subgrade is influenced by several variables, such as the characteristics of the GCLs, the subgrade initial moisture content, and the dynamics of hydration and rehydration of the liner due to exposure field conditions. As a consequence of insufficient hydration, the GCL may present inferior behavior as barrier. These aspects, however, have not yet been evaluated in tropical climate conditions, as in Brazil, where lateritic soils tend to have higher levels of optimum moisture content than those observed in countries with temperate climates, different mineralogy, and a large portion of fine particles. The present research evaluated the influence of two different lateritic subgrades in the hydration process of GCLs in isothermal (hydration columns) and thermal conditions (physical model). Results showed that the subgrade moisture content significantly impacted the GCL hydration in the two analyzed conditions. The exposure to thermal cycles drastically reduced the ability of the lateritic subgrades to hydrate the GCLs. The shrinkage of the GCL panels was related to the GCL moisture content and the number of thermal cycles applied. In general, the lateritic subgrades showed a limited capacity to hydrate the GCLs, with saturation values lower than expected for the correct performance of these materials. The understanding the GCL hydration behavior requires unsaturated analysis of the subgrade and GCLs and the magnitude of the differential suction between these materials. The characterization of the GCLs after hydration tests showed that the parameters of CEC, SI, and hydraulic conductivity suffered slight variation, with a trend of decrease. The research showed the importance of investigating GCLs under practical installation conditions and the influence of important variables present in this application.