Overview
EN ISO 22476-14:2020 - "Geotechnical investigation and testing - Field testing - Part 14: Borehole dynamic probing" is a CEN/ISO standard that specifies equipment requirements, execution procedures and reporting for borehole dynamic probing. The standard defines how to perform dynamic probing from a borehole base to reliably assess subsoil conditions, limit result scatter caused by equipment or implementation, and support geotechnical design in accordance with EN 1997‑1 and EN 1997‑2.
Key topics & technical requirements
- Scope and purpose: Standardizes borehole dynamic probing to prevent incorrect appraisals of subsoil and to enable reproducible results.
- Equipment requirements: Specifies probe and device geometry and materials (e.g., cone tip dimensions and steel quality S235JR), hammer mass and fall height, watertight hollow cylinder for the hammer, and use of additional weights when probing more than 20 m below water.
- Test geometry and limits: Typical test range and probe length, device mass and nominal tip area are covered; the device can be used to explore soils to depths of ≈60 m depending on borehole and drilling method.
- Procedure: Requirements for borehole preparation (borehole diameter ≤ 250 mm, casing not extending below the base), cleaning the borehole base, maintenance of water levels, and avoidance of negative pressure during cleaning.
- Measurement metric: The standard defines penetration resistance by the number of blows N30 - the blows required for 30 cm penetration (measured between 15–45 cm depths). It also records sub-ranges (0–15, 15–30, 30–45 cm) to aid interpretation.
- Calibration, checks & reporting: Equipment checks, calibration, field records and standardized reporting (including a header sheet and measuring record) are required to reduce scatter and allow consistent interpretation.
- Data interpretation: Guidance on qualitative evaluation and derivation of geotechnical parameters; Annex B provides example relations for groundwater effects and for correlating results from different probes.
Applications
- Preliminary and detailed site investigations for foundations, earthworks, underground works and slope/stability assessments.
- Mapping subsoil stratigraphy and assessing relative density and bearing resistance where dynamic probing data (N30) inform design.
- Supplementing other in-situ tests (SPT/CPT) and laboratory tests for geotechnical characterization and ground improvement planning.
Who uses this standard
- Geotechnical engineers and consultants
- Site investigation contractors and drill rig operators
- Testing laboratories and quality control teams
- Structural and foundation designers, and regulatory bodies enforcing EN 1997 design practice
Related standards
- EN 1997‑1 / EN 1997‑2 (geotechnical design and investigations)
- ISO 22475‑1 (sampling methods and groundwater measurements)
- ISO 14688‑1 (soil identification and description)
- EN 10025‑2 (material specification for structural steel S235JR)
By following EN ISO 22476‑14:2020, practitioners ensure consistent, traceable borehole dynamic probing results that are suitable for integration into geotechnical design and reporting workflows.