Drain Envelopes for Problematic Calcareous Soils of Irrigated Agricultural Lands in Egypt

Envelope materials are used for surrounding subsurface drain pipes commonly installed to reclaim waterlogged and salt-affected lands to prevent entry of soil particles into drains and to constitute a medium of good permeability around the pipe and therefore reduce entrance resistance. In calcareous soils prone to the reduction of drainage capacity as a result of high clogging, determining adequate envelope materials is a crucial issue under Egyptian conditions. The study was conducted on a calcareous soil with a high risk of calcium carbonate precipitation. Four drain-envelope combinations of subsurface drainage systems were tested in an experimental field. It came out that granular and pre-wrapped drain envelopes, with a normal grade of 10cm/100m, were the best material regarding their hydraulic and mechanical performance for sub-surface drainage in calcareous soils.