Overview
ISO 10776:2012 - "Geotextiles and geotextile-related products - Determination of water permeability characteristics normal to the plane, under load" specifies a laboratory method to measure the water permeability (flow velocity) normal to the plane of geotextiles and related products when subjected to defined normal compressive stresses. The test is performed at compressive stresses of 2, 20 and 200 kPa, with a 50 mm head across the specimen, and yields an index characteristic useful for material comparison and quality control (not a direct measure of in-service performance).
Key topics and technical requirements
- Test principle: Measure steady-state water flow perpendicular to the geotextile plane under constant normal compressive loads and constant head conditions.
- Specimen preparation: Cut specimens per ISO 9862; handle flat and avoid folding; typically five specimens are tested (or more if statistical confidence requires).
- Apparatus: Cylindrical cell with internal diameter ≈ 95 mm (± tolerances), upper and lower porous metal plates with defined perforation pattern, sealing to prevent edge flow and a loading mechanism able to apply 2, 20 and 200 kPa ±5 %.
- Hydraulics & water quality: Water temperature 18–22 °C; water must be deaerated or supplied from a stilling tank to avoid entrapped air; dissolved oxygen ≤ 10 mg/kg; filter if visible solids accumulate.
- Procedure essentials: Saturate specimens for ≥ 12 h using a wetting agent, align plate perforations, apply seating stress, establish 50 mm head, collect flow over fixed intervals (minimum 1 L and ≥ 30 s), take at least three consecutive readings and report mean flow velocity vN50/σ (m/s).
- Calculations & reporting: Flow velocity calculated from collected volume, area exposed and time; plot mean velocity versus compressive stress on a logarithmic scale. Note that plate permittivity must be at least twice that of the specimen or results are invalid.
Applications and users
ISO 10776:2012 is primarily used for:
- Manufacturers for product development and quality control of geotextiles and geotextile-related products.
- Independent testing laboratories performing standardized permeability/permivity testing.
- Geotechnical and civil engineers who need comparative index data for design selection (filtering, drainage, separation).
- Specifiers and procurement teams requiring reproducible laboratory data for tendering and compliance.
Because the test provides an index under controlled loads, it supports material selection, comparative performance assessment, and QC, but should be complemented by project-specific performance evaluations for in-service conditions.
Related standards
- ISO 9862 - Sampling and preparation of test specimens
- ISO 10318 - Geosynthetics - Terms and definitions
- ISO 2854, ISO 5813, ISO 10320 - referenced for statistics, water quality measurement, and site identification respectively
Keywords: ISO 10776:2012, geotextiles, water permeability, permittivity, flow velocity, compressive stress, geosynthetics, laboratory test.
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