Avaliação do desempenho de sistemas drenantes em condições de laboratório.

Abstract

The present research evaluated the performance of different draining systems on a podzolic haliod sandy soil with duripan, under controlled laboratory conditions, using a sand tank horizontal model. The following materials composed the draining systems: perforated smooth, PVC tube, KANAFLEX corrugated flexible tube, ceramic tube, and two envelopes types: sand and XT4 synthetic polyester mantle. The treatments consisted of combinations of each draining tube with a kind of envelope and, also, with the abscence of it. In regards to the entrance hydraulic heads, the draining systems composed of ceramic tube and coarse sand envelope, ceramic tube and synthetic mantle, and smooth PVC tube and coarse sand envelope showed very good performance, the smooth PVC tube with no envelope smooth PVC tube with synthetic mantle, while the flexible tube without envelope, the flexible tube with coarse sand envelope, and the flexible tube with synthetic envelope presented a good performance. A moderate performance was displayed by the ceramic tube without envelope. Concerning the ratio between entrance and total hidraulic heads, the ceramic tube with coarse sand envelope presented the best performance, while the plastic tube with coarse sand envelope, the ceramic tube with synthetic envelope, the corrugated tube without envelope, and the corrugated tube with coarse sand envelope showed regular performance. The other systems showed a very bad performance. According to the entrance resistance, the draining systems tested presented a regular to very good performance, except for the flexible tube without envelope which had a high entrance resistance value. The effective radius obteneid for smooth PVC and ceramic tubes demonstrated that the increase in envelope thickness, when coarse sand was used, incresed the effective radius on the order of 30%. When quantifying sediments in the draining systems, the ceramic tube without envelope and the ceramic tube with coarse sand envelope presented the highest amount of sediments. On the other hand, the synthetic mantle envelope when used on the draining tubes, markedly reduced the quantify of sediments. The entrance resistance effect on draining spacing, showed that under steady state conditions, the simulated draining spacing, for the field conditions, Whereas, under unsteady state regime, when high entrance resistance values were adopted, the draining spacing decreased, resultinj considerable density increase.