Overview
ISO/TR 18228-3:2021 - "Design using geosynthetics - Part 3: Filtration" is a technical report from ISO that provides guidance for the design and specification of geotextile filters used in geotechnical and civil engineering. The document explains key failure mechanisms (e.g., internal erosion, blinding and clogging), describes the filtration function of geotextiles, and proposes approaches to select relevant engineering properties for reliable filter performance over the design life.
Keywords: ISO/TR 18228-3:2021, geosynthetics, geotextile filtration, filter design, soil filtration, slurry filtration
Key Topics
- Filtration fundamentals - role of geotextiles in stabilizing the soil skeleton while allowing water and fines in suspension to pass.
- Failure mechanisms - internal erosion (piping), blinding (surface cake), clogging (pore blockage), chemical and biological precipitation, and effects of trapped air or abrasion.
- Filter selection fundamentals - criteria to balance particle retention and hydraulic flow capacity.
- Materials and properties - guidance on geotextile materials and the functional properties relevant to design, such as:
- Characteristic opening size (COS)
- Permittivity (ψ) / permeability and velocity index
- Percent open area (POA) and number of constrictions
- Resistance to water penetration
- Design principles - procedures for designing filters for soil filtration and for slurry / suspended solids filtration, including retention, non‑retention and permeability criteria.
- Testing and compatibility - recommended laboratory tests and performance checks, e.g. gradient ratio, hydraulic conductivity ratio, retention under turbulent flow, biological/chemical clogging potential, and abrasion impact.
- Practical guidance - examples of material specifications and design guidance tailored to common field applications.
Applications
ISO/TR 18228-3 is used by:
- Geotechnical and civil engineers designing drainage, embankments, levees, retaining structures, coastal and bank protection where geotextiles act as filters.
- Specification writers and procurement teams preparing material specs for geotextile filters.
- Contractors and installation supervisors assessing suitability and installation risks.
- Testing laboratories evaluating soil/geotextile compatibility and long‑term filter performance.
Practical applications include soil-to-drain interfaces, silt fences, filter layers behind rip-rap or gabions, drainage around PVDs and protection of drainage pipes.
Related Standards
- ISO/TR 18228-1 (general guidance in the series)
- ISO 10318-1 (geosynthetics - terms and definitions)
- Relevant test methods cited (for example ASTM D5101 for hydraulic gradient measurement)
ISO/TR 18228-3:2021 helps engineers and specifiers make informed, durable filter-design choices using geosynthetics by combining performance criteria, testing guidance and practical specification examples for reliable soil filtration and slurry control.
