Geotextiles for Drainage Function
topic
Drainage geotextiles transmit water within their plane (in-plane flow) to collection points, functioning as drainage blankets behind retaining walls, beneath embankments, and in landfill leachate collection layers. Thick needle-punched nonwoven PET geotextiles (400–1,200 g/m², thickness 4–12 mm under 2 kPa, transmissivity θ > 10⁻⁴ m²/s per ISO 12958) provide planar drainage capacity. Geocomposite drainage products combine geonet core (HDPE extruded net, transmissivity 5×10⁻⁴ to 5×10⁻³ m²/s at 20 kPa) with bonded nonwoven filter geotextile on one or both faces, providing drainage capacity 5–10× greater than equivalent nonwoven alone at 30–50% reduced thickness. Prefabricated vertical drains (PVD, band drains, width 100 mm, thickness 4 mm, filter jacket O₉₀ 0.08–0.15 mm) are installed at 1.0–2.0 m grid spacing to 10–30 m depth in soft marine clay to accelerate primary consolidation from 10–30 years (natural drainage) to 6–18 months, enabling rapid embankment construction for highways and ports. Landfill leachate collection layers require transmissivity > 3×10⁻⁵ m²/s under 300 kPa overburden (US EPA RCRA Subtitle D). Global drainage geotextile and geocomposite market exceeds $2.1 billion.
Role
Drainage geotextiles accelerate pore water pressure dissipation in soft soils and maintain hydraulic gradients in retaining structures and landfills, enabling construction of infrastructure on weak ground that would otherwise require expensive ground improvement or deep foundation solutions.