Evaluation of Three Geocomposite Envelope-Drains in an Experimental Model

Recently، use of synthetic materials has increased in irrigation and drainage projects due to their environmental advantages. Also، use of geotextile and PLM has been considered in drainage projects instead of granular envelopes. This study was conducted to evaluate the efficiency of geocomposite envelope-drain to reduce water-table levels. To simulate natural conditions of a drained land in the laboratory، a soil and sand tank was used that simulated part of a drainage trench in addition to adjusting the height of water table. Three envelope-drains with different geotextile envelope and drainage pipes with granular and PLM (PP450 type) envelopes were tested. In this study، the perimeter of drainage pipe and envelope-drains was equal. The results of this study showed that the performance of envelope-drain in draining excess soil water and lowering water table was similar to the drainage pipe with granular envelope. Under hydraulic head of 110 cm، in the center of the drain، drop in the water surface profile of geocomposite envelope-drain was 14. 3% lower than the drainage pipe with granular envelope. By increasing the horizontal distance to the drains، drop in the water table profile of geocomposite envelope-drain was 9. 8% lower than the drainage pipe with granular envelope.