Geonet for Retaining Wall Drainage: Types and Selection Guide

1. Collects Seepage Water

Geonet installed behind a retaining wall provides a continuous path for water moving through the backfill. Instead of allowing water to accumulate against the wall, the drainage layer guides it toward the bottom of the structure.

2. Reduces Water Pressure

The main purpose of the drainage system is to prevent water from remaining trapped behind the wall. By providing a path for water to leave the backfill, the system reduces pore water pressure and the resulting hydrostatic pressure acting on the wall. However, geonet is a drainage material, not a structural reinforcement product. It does not replace structural retaining wall design.

3. Filters Soil Particles

When a geocomposite drainage product is used, the nonwoven geotextile acts as a filter layer. It allows water to pass into the drainage core while preventing fine soil particles from entering and clogging the geonet.

4. Provides Drainage Where Space Is Limited

Traditional retaining wall drainage may require a relatively thick layer of gravel or other drainage aggregate. A geocomposite drainage layer provides a continuous drainage path with a much smaller thickness, which can be useful for underground structures and projects where available space is limited.

Approximately 4,200 m² of Tri-planar geocomposite drainage material, with a thickness of about 7.6 mm, was used in the project. The material consisted of a Tri-planar geonet drainage core and nonwoven geotextiles. The geotextile provided filtration, while the geonet collected and conveyed water within the plane. Installed between the structure and backfill soil and connected to the bottom drainage system, it created a continuous drainage pathway.

Frist of all, the thickness of a conventional aggregate drainage layer would typically require about 460 mm, while the geocomposite drainage material was approximately 7.6 mm thick. This significantly reduced the space required for the drainage layer and reduced the amount of aggregate transportation and installation work. For retaining walls and underground structures, this type of thin drainage system is particularly suitable where construction space is limited and reduces drainage risks associated with long-term water accumulation.