Overview
ISO 12957-2:2024 - Geosynthetics - Determination of friction characteristics - Part 2: Inclined plane test specifies a laboratory method to measure the friction characteristics of geosynthetics (geotextiles, geotextile-related products and geosynthetic barriers) in contact with soils or other geosynthetics at low normal stress. The method uses an inclining plane apparatus to determine the angle at which a soil‑filled box slides over a fixed geosynthetic, producing metrics such as the angle of friction (φ) and angle of slipping (β). The test is intended as a performance test with site‑specific soils and can also be run as an index test with standard sand. Creep (time‑dependent displacement) can be measured without necessarily reaching slip failure.
Key topics and technical requirements
- Test principle: Gradually incline a rigid plate at a controlled rate and record the angle when the upper soil box displaces 50 mm (angle of slipping β).
- Apparatus types: Two main arrangements - a rigid base (geosynthetic fixed to a smooth plate) and a soil‑filled base (geosynthetic supported by soil in the lower box). Upper box may be roller supported or not.
- Specimens & sampling: Specimen sampling and preparation per ISO 9862; test three specimens per direction or face to represent variability.
- Conditioning: Perform tests in the standard atmosphere per ISO 554 (20 ±2 °C, 65 ±2 % RH) until mass stability is achieved.
- Loads & measurements: Normal force and normal stress are defined; equipment must allow controlled incline rate (standard 3 ±0.5°/min) and angle measurement precision (±0.5°). A trip switch stops the test at the specified displacement (50 mm).
- Data & calculations: Determine angle of friction φ, normal stress σn, shear stress τ, and account for restraining forces (fr(β)) where rollers are used. Tests can also capture interface creep.
- Limitations: Results for geogrids on rigid supports may not be representative of field behavior because friction depends on the support.
Applications and users
ISO 12957-2:2024 is used where interface friction influences design or performance:
- Geotechnical and civil engineers assessing stability of reinforced slopes, retaining walls, landfill liners, or embankments.
- Manufacturers and QA labs verifying friction properties of geosynthetic products and demonstrating performance to clients.
- Construction contractors and consultants selecting appropriate geosynthetics for site‑specific soils.
- Researchers studying interface behavior, creep, or comparative performance under low normal stress.
Keywords: ISO 12957-2:2024, geosynthetics, inclined plane test, friction characteristics, geotextiles, geogrids, angle of friction, interface creep.
Related standards
- ISO 9862 - Sampling and preparation of test specimens
- ISO 554 - Standard atmospheres for conditioning/testing
- ISO 10318-1 - Geosynthetics - Terms and definitions
- ISO 6344-2 - Abrasive grain sizes (for rigid support tests)
- Other parts of the ISO 12957 series (see ISO catalogue)
Open preview (PDF)Geosynthetics — Determination of friction characteristics — Part 2: Inclined plane test