The aim of the research was to evaluate the performance of eight types of envelopes installed around tubular drains in a horizontal tank model, with the treatments bidim OP-20, bidim OP-30, XT-2 and XT-4, 0.15, 0.10 and 0.05 m thick gravel and the treatment drain without a wrapper. The response-variables for the treatments used consisted of the depth of water drained in thirty minutes, the mass of sediment transported by the water during this same time interval and the hydraulic performance of the drains based on the entrance resistance of the flow and relation between the flowrate and the hydraulic head at 0.55 m drain-soil. The depth of water drained did not show significant difference at 5% probability level; however, the geotextile bidim OP-20 and XT-4 showed the best performance taking into account costs and instalation suitability. In relation to the sediment mass transported, the influence of the wrapper thickness using gravel was observed besides the option of geotextile as excelent filter. The importance of using drain wrappers was demonstrated by comparing the entrance resistance data for the treatments without wrapper (r ent = 0.0102 d m-1) and the 0.15 m gravel treatment (r ent = 0.0032 d m-1), allowing a 68.7% reduction.
drainage; performance; envelope
