ISO 11058:2019

Overview

ISO 11058:2019 - "Geotextiles and geotextile-related products - Determination of water permeability characteristics normal to the plane, without load" specifies two laboratory test methods to measure water permeability through a single layer of geotextile normal to the plane. The standard defines the constant head method and the falling head method, procedures for specimen preparation and handling, measurement and calculation conventions (including temperature correction to 20 °C), and reporting requirements. This is the third edition (2019), replacing ISO 11058:2010.

Key topics and technical requirements

• Test methods
  • Constant head: steady unidirectional flow with several constant heads (including a maximum head ≈ 70 mm).
  • Falling head: unidirectional flow under a falling head (apparatus capable of at least 250 mm head).
• Specimens
  • Samples handled flat, not folded; cut per ISO 9862.
  • Typical test set uses five specimens of suitable dimension for the apparatus.
• Apparatus and measurement
  • Apparatus must allow visual observation of bubbles and have a minimum exposed diameter (≥ 50 mm) with internal diameter accuracy to 0.1 mm.
  • Support grid may be used to avoid deformation; head loss of apparatus alone (with grid) must be < 1 mm.
  • Water supply quality: temperature normally 18–22 °C (temperature corrections to 20 °C via Annex A); recommended de-aired or stilling-tank feed; dissolved oxygen ≤ 10 mg/kg; filter if visible solids accumulate.
• Calculations and indices
  • Flow velocity is corrected to 20 °C using a correction factor (Annex A).
  • Plot head loss against velocity and select best-fit curve through the origin (Annex B).
  • Velocity index (v-index): velocity corresponding to 50 mm head loss (expressed to ±1 mm/s).
• Procedure details
  • Specimens saturated with 0.1% non-ionic surfactant for ≥ 12 h.
  • Repeated measurements across head levels and reporting of temperature, apparatus details and results.

Applications

• Quality control and specification verification for geotextiles used in:
  • Drainage and filtration systems
  • Landfill liners and drainage layers
  • Road, railway and civil engineering drainage applications
• Material selection, R&D and performance comparison where through-thickness permeability (normal to the plane) is critical.

Who uses ISO 11058:2019

• Geosynthetics manufacturers and product developers
• Independent testing laboratories and quality assurance teams
• Geotechnical, civil and environmental engineers specifying or verifying filter/drainage performance
• Procurement and compliance officers assessing product conformity

Related standards

• ISO 9862 - Sampling and preparation of test specimens (cited)
• ISO 2854 - Statistical interpretation of data (cited)
• ISO 5813 - Determination of dissolved oxygen (cited)
• ISO 10320 - Geosynthetics identification on site (cited)

Keywords: ISO 11058:2019, geotextiles, water permeability, constant head, falling head, velocity index, geosynthetics testing.