Overview
ISO/TR 18228-4:2022 - "Design using geosynthetics - Part 4: Drainage" is a technical report that provides guidance for designing drainage functions using geosynthetics (including geotextiles and geocomposites). The document defines criteria for evaluating the required and available flow rate of geosynthetics, summarizes relevant laboratory testing, and lists safety factors and reduction factors to apply in design of geosynthetic drainage systems.
This part of the ISO 18228 series is written in a limit-state format and complements general guidance in ISO/TR 18228-1. It covers concepts, material components, hydraulic properties, and design procedures specific to drainage.
Key topics and requirements
- Flow-rate evaluation: Procedures to calculate the design (input) flow rate from rainfall, surficial flow and filtrated flows, and to determine available in-plane flow capacity of geosynthetics.
- Hydraulic fundamentals: Use of Darcy’s law, hydraulic gradient, transmissivity (ϑ), permittivity (ψ) and related hydraulic parameters.
- Geocomposite components: Guidance on filter components, drainage cores, and definitions for draining geocomposites (GCD).
- Geotextile filter performance: Filter criteria, clogging mechanisms (chemical, biological, intrusion) and corresponding reduction factors.
- Factors affecting performance: Effects of compressive loads, applied pressure, temperature (viscosity), boundary materials, long‑term creep and ageing on available flow rate.
- Laboratory testing: Summary of lab tests for water flow capacity, test boundary conditions, and how short‑term test results are converted to long‑term design values using reduction and safety factors.
- Equivalency with granular drainage: Methodology to compare geosynthetic drains with granular layers (slope and vertical flow equivalence).
- Informative annexes: Movement of water in ground and recommended reduction factors to cover uncertainties.
Practical applications
ISO/TR 18228-4 is intended for design and specification of geosynthetic drainage elements used in:
- Subsurface and slope drainage
- Retaining structures and basement waterproofing
- Road and pavement subbase drainage
- Landfill leachate collection and containment systems
- Tunnel and underground structure drainage
The guidance helps ensure adequate drainage capacity, prevent clogging, and provide robust long‑term performance.
Who should use it
- Geotechnical and civil engineers designing drainage systems
- Specifiers and consultants preparing performance criteria
- Manufacturers of geotextiles and geocomposites
- Contractors and testing laboratories performing hydraulic tests
- Regulators and asset owners seeking harmonized design practice
Related standards
- ISO/TR 18228-1 (general guidance for design using geosynthetics)
- ISO 10318-1 (terms and definitions for geosynthetics) - referenced normative document
For project-level application, consult the full ISO/TR 18228-4:2022 text and your national standards body for adoption and national annexes.
