Overview
ISO 10773:2011 specifies a laboratory test method for measuring gas permeability of clay geosynthetic barriers (bentonitic geosynthetics). The standard focuses on steady-state gas flow - important for long-term containment of gases - and defines apparatus, specimen preparation, test conditions and reporting requirements to determine a gas flow index (GFI) for clay geosynthetic barriers.
Key topics and requirements
- Scope & purpose: Measurement of gas flow through clay geosynthetic barriers under conditions representative of long-term containment (steady-state gas permeability).
- Test gas: Nitrogen is used as the reference gas (properties noted in the standard); alternative gases may be reported with dynamic viscosity.
- Loading and pressures:
- Normal stress on specimen: 20 kPa (±5%).
- Differential gas pressure across specimen: 15 kPa.
- Additional 15 kPa normal stress recommended when applying differential pressure to prevent piston rise.
- Specimen and conditioning:
- Specimen diameter (flow cross-section) ≥ 150 mm to be representative of needle-punched or stitched products.
- Bentonite water content range: 90% to 130%; three target hydration states typically around 100%, 110% and 120%.
- Pre-hydration and conditioning according to ISO 554; immersion in deionized water and one-week loading at 20 kPa are specified.
- Apparatus & setup:
- Two-chamber test cell with glass-bead support/containment, piston and displacement gauge to monitor thickness reduction and stabilization.
- Lateral sealing using bentonite paste; leak checks recommended.
- Gas flow meter capable of measuring 0.1 ml/min to 5 l/min.
- Calculation:
- Steady-state outlet volumetric flow converted to gas flux (q) and plotted vs. bentonite water content.
- Gas Flow Index (GFI) is defined as the gas flux at 110% water content (index at 110% and ∆p = 15 kPa).
- Test report: Identification of product, sample details, mass per unit area, initial/final water contents, test deviations and procedural details.
Applications and users
ISO 10773:2011 is relevant to:
- Manufacturers of clay geosynthetic barriers (bentonite liners) for quality control and product specification.
- Independent testing laboratories performing gas permeability testing and material certification.
- Environmental, geotechnical and landfill engineers assessing long-term containment of landfill gas, biogas, landfill capping, and engineered barrier systems.
- Regulatory bodies and specifiers requiring standardized performance data for barrier design and safety assessments.
Related standards
- ISO 9863-1 / ISO 9863-2 - Thickness determination at specified pressures
- ISO 11465 - Determination of dry matter and water content (gravimetric)
- EN 14196 - Mass per unit area test methods for clay geosynthetic barriers
Keywords: ISO 10773:2011, clay geosynthetic barriers, permeability to gases, gas flow index, GFI, gas permeability testing, bentonite, geosynthetics.