Overview
EN ISO 11058:2019 (ISO 11058:2019) specifies laboratory test methods to determine the water permeability characteristics of a single layer of geotextile or geotextile-related product normal to the plane, without load. The standard describes two complementary procedures - the constant head method and the falling head method - and defines reporting and calculation conventions (including the velocity index).
Key topics and technical requirements
- Test methods
- Constant head method: unidirectional flow under a maintained head; suitable apparatus must observe air bubbles and maintain heads up to at least 70 mm.
- Falling head method: transient head decay measurement (details, apparatus and calculation procedures provided).
- Specimen handling and sampling
- Specimens must be taken and prepared in accordance with ISO 9862; avoid folding and disturbance; typically five specimens are tested unless statistical requirements demand more (ISO 2854).
- Apparatus and measurement
- Apparatus internal diameter minimum 50 mm; exposed specimen diameter must match apparatus; supporting grids allowed to avoid deformation.
- Water quality/condition: temperature 18–22 °C (temperature correction given in Annex A), dissolved oxygen ≤ 10 mg/kg, de-aired or from a stilling tank recommended to prevent entrapped air. Filtration if visible suspended solids occur.
- Measurement instruments: thermometer, stopwatch, measuring vessel or flow gauge; accuracy requirements are specified.
- Parameters and reporting
- Velocity index (v‑index): velocity corresponding to a 50 mm head loss, expressed to nearest ±1 mm/s.
- Annexes cover temperature correction, the relationship between head loss and flow velocity, reference velocity index values, and worked examples.
Applications
EN ISO 11058:2019 is used to characterize the through-thickness hydraulic behavior of geotextiles and related products for:
- Drainage and filtration layer design in roadworks, rail, and retaining structures
- Landfill drainage and leachate collection systems
- Erosion control and hydraulic structures where normal-to-plane permeability affects performance
- Quality control during manufacture and verification testing for construction specifications
Who uses this standard
- Geosynthetics and geotextile manufacturers for product development and QC
- Independent testing laboratories performing permeability/permeation tests
- Geotechnical and civil engineers specifying materials for drainage and filtration
- Contractors and asset owners verifying compliance with project specifications
Related standards
- ISO 9862 - Sampling and preparation of geosynthetic test specimens
- ISO 2854 - Statistical interpretation of data (means and variances)
- ISO 5813 - Measurement of dissolved oxygen (referred for water quality)
Keywords: EN ISO 11058:2019, ISO 11058:2019, geotextile permeability, water permeability normal to plane, constant head, falling head, velocity index, geosynthetics testing.
