Uso de argilas montmoriloníticas para impermeabilização de canais de irrigação.

Abstract

The present work analyzes the behavior of a montmorillonite clay for waterproofing irrigation channels, aiming at minimizing water losses by infiltration. Compaction and permeability tests were carried out in order to determine the optimal percentage of montmorillonite clay to be added to the soil to obtain the maximum impermeability. He settled in the trials of permeability, that the percentage of 5.0% of montmorillonite clay added to the natural soil, classified as silty sand, is sufficient for a suitable waterproofing, thus obtaining a permeability coefficient K = 2.1 x 10-7 The percentage of montmorillonite clay added to the soil for the field tests was 7.0%, in order to compensate for the losses of montmorillonite clay caused during the process of homogenization of the mixture (soil - clay) in the concrete mixer Infiltration tests were performed through the four channels, without water flow (static channels), coated with compacted natural soil (control), with (evaporation), with single-montmorillonite clay, applying the continuous membrane technique and finally with bricks of the soil-montmorillonite clay mixture, applying the discontinuous apparent membrane technique. The test period was 80 days with the channels being subjected to drying-wetting cycles, which practically no significant influence had on the infiltration. During the 57 days, in which the channels remained with water, an accumulated infiltration of 42, 150 and 1,104 cm of water was observed for the channels coated with mixtures soil - montmorillonite clay, soil bricks - montmorillonite clay and compacted natural soil, respectively. The results obtained in the infiltration tests showed clearly that the channel coated with the mixture soil - montmorillonite clay (applying the technique of the continuous apparent membrane) presented smaller infiltration than allows to indicate this material as the best alternative to channel coatings. It was also possible to evaluate the erosions, obtained with different flows and declivities, using channels with water flow (dynamic channels) coated with the mixture soil - montmorillonite clay, applying the continuous apparent membrane technique.