Performance of geocomposite and granular drains under irrigation canal linings

ABSTRACT: In many irrigation projects, where the groundwater table is high, part of the canal may be located below the water table. In such cases the groundwater would apply uplift pressure to the bottom and side panels of the lining. This phenomenon may cause deformation, displacement or rupture of the concrete panels, or other damage, which would cause high maintenance costs for the project. The most effective way to control the uplift pressure is to provide a filter drainage system under the canal lining. At present, granular filters are the most common material in use. However, the application of granular materials is not an easy task in some cases, owing to the high costs involved, and the environmental impacts. Therefore, in recent years, geosynthetic materials (geocomposites) have been employed as a replacement for granular filters. In the present study, the behaviour of geocomposite material as a filter drainage layer under canal lining has been investigated, using a physical laboratory model. The results of the experiments show that a geocomposite layer with adequate thickness can fully relieve the uplift pressure and discharge the drained water effectively. The efficiencies of the filter drainage under the bottom concrete panels, as well as under the bottom and side concrete panels, were studied. The results show that providing a filter under the side panels has no significant effect on the drainage capacity of the system.