Overview
ISO 22476-9:2020 - "Geotechnical investigation and testing - Field testing - Part 9: Field vane test (FVT and FVT-F)" specifies how to perform and report field vane tests used to determine vane shear strength in fine‑grained soils. The standard covers equipment requirements, test configurations, execution, measurement (torque and rotation), derivation of peak and remoulded shear strength, evaluation of soil sensitivity and optional assessment of post‑peak behaviour. It applies to onshore and nearshore investigations and identifies sources of uncertainty (Annex D). ISO 22476-9:2020 also fulfils requirements for field vane testing under EN 1997‑1 and EN 1997‑2 (Eurocode 7).
Key technical topics and requirements
- Test types: Ordinary Field Vane Test (FVT) and Fast Field Vane Test (FVT‑F).
- Equipment and components: vane and vane shaft, extension rods (cased/uncased), protective casing and shoe, friction reducer, slip coupling, rotation unit, torque/rotation measurement and data acquisition systems.
- Configurations: above‑ground (using extension rods) or downhole (direct measurement near the vane).
- Measurement controls: procedures for internal and external friction torque readings, calibration and maintenance (Annex C), and accounting for rod/soil friction.
- Test procedure: pre‑checks, position and inclination control, methods for insertion (pushing or in boreholes/trial pits), rotation rate control, time‑to‑failure and torque/rotation recording.
- Data interpretation: limit equilibrium analysis to derive peak and remoulded strength, sensitivity calculation, and guidance for tapered/rectangular vanes with non‑standard H/D ratios (Annex E–F).
- Reporting & uncertainty: standardized reporting elements (location, equipment, procedure, results) and uncertainty estimation (Annex D). Depth correction for inclination is covered (Annex G); post‑peak estimation methods are given (Annex H).
Practical applications and users
- Applications: site investigation for foundations, slope stability, embankments, coastal/nearshore projects, quick assessments of undrained shear strength, and sensitivity checks for liquefaction or remoulding susceptibility.
- Who uses it: geotechnical engineers, site investigation teams, contractors, consultants, testing laboratories and regulators who require consistent, traceable field vane testing and reporting aligned with ISO and Eurocode requirements.
Related standards
- EN 1997‑1 and EN 1997‑2 (Eurocode 7) - geotechnical design/investigation requirements (ISO 22476‑9 fulfils field vane test aspects).
- ISO 10012 - measurement management systems (referenced for measurement quality).
Keywords: ISO 22476-9:2020, field vane test, FVT, FVT-F, vane shear strength, remoulded strength, soil sensitivity, geotechnical testing, onshore, nearshore.