Overview
EN ISO 12958-2:2020 (ISO 12958-2:2020) defines a laboratory performance test for measuring the constant‑head in‑plane water flow capacity of geotextiles and geotextile‑related products. The standard specifies test apparatus, specimen preparation, boundary materials and a series of standard test conditions that reflect realistic project situations - including soil confinement, low hydraulic gradients, varied normal loads and seating times - so that transmissivity (flow per unit width) can be determined under service‑relevant conditions.
Key topics and requirements
- Scope: Determines constant‑head, in‑plane flow capacity using boundary materials and conditions of interest; proposes a set of standard test conditions.
- Test principle: Measures volumetric flow rate per unit width under a defined normal compressive stress (σ), hydraulic gradient (i), seating time (t) and boundary conditions (b).
- Specimen handling and selection: Requirements for number, dimensions and conditioning of specimens; guidance on granular boundary materials and soil confinement.
- Apparatus & procedure: Details on test equipment, seating and loading procedures, low‑gradient constant‑head setup, and measurement practice.
- Calculations & reporting: Methods to express performance in‑plane water flow capacity (q_perf), correction factors (e.g., temperature conversion), and required test report content.
- Special considerations:
- Geotextile intrusion into drainage cores and its effect on transmissivity.
- Directional testing for products with discrete draining elements (flow may be direction‑dependent).
- Limitations regarding long‑term creep, chemical/biological clogging and durability - these require additional standards or assessment.
Applications and practical value
- Provides a realistic laboratory method to evaluate in‑plane transmissivity of drainage geotextiles and geocomposites under project‑specific conditions.
- Useful for:
- Product development and quality control by manufacturers.
- Specification and acceptance testing by owners, consultants and test laboratories.
- Design verification where soil confinement, low hydraulic gradients and service loading influence drainage performance (e.g., landfills, retaining structures, pavements, subsurface drainage systems).
- Helps assess the impact of soil‑geotextile interaction and seating/creep on short‑ to mid‑term in‑plane flow capacity.
Who should use this standard
- Geotechnical and civil engineers, geosynthetic manufacturers, independent testing laboratories, specification writers and researchers involved in drainage design and performance assessment of geotextiles and geocomposites.
Related standards
Keywords: geotextiles, in‑plane water flow capacity, transmissivity, EN ISO 12958-2:2020, geotextile performance test, hydraulic gradient, soil confinement, seating time.