Overview
ISO 22476-14:2020 specifies requirements for borehole dynamic probing as part of geotechnical investigation and field testing. The standard defines equipment, execution, calibration and reporting procedures to ensure consistent, reliable probing results and to reduce scatter caused by equipment or implementation. It explicitly supports use of borehole dynamic probing in accordance with foundation design requirements in EN 1997‑1 and EN 1997‑2.
Key topics and technical requirements
- Scope and purpose: Defines how to perform dynamic probing from the borehole base to obtain penetration resistance and derive geotechnical parameters.
- Equipment specification: Detailed probe and device characteristics (cone dimensions, tip diameter, hammer mass, fall height), watertight hollow cylinder for the hammer, and use of additional weights for deep water applications.
- Probe geometry & limits: Typical probe tip diameter and cone dimensions; device can explore to depths of approximately 60 m (depending on borehole and boring method).
- Test parameters: Definition of the key index N30 - number of blows required for 30 cm penetration measured between 15 cm and 45 cm - and procedures for soils with very low or very high penetration rates.
- Borehole requirements: Borehole diameter should not exceed 250 mm; casing must not extend below the borehole base; borehole base must be cleaned and stable.
- Water and buoyancy handling: Maintain borehole water level above groundwater; add specified additional weights when water depths exceed ~20 m to counteract buoyancy.
- Checks, calibration and maintenance: Verticality, height of fall and automatic release device checks; watertightness monitored after each test; device functionality verified after damage/repair and at least every six months.
- Field records and reporting: Use of a header/measuring record, bar‑diagram representation of N30 adjacent to bore profile, and comprehensive test reporting (company, test ID, depth, deviations, signatures).
Applications and who uses it
ISO 22476-14 is used by:
- Geotechnical engineers and site investigation consultants for soil profiling and deriving parameters for foundation and slope design.
- Drilling and testing contractors to standardize field execution and equipment checks.
- Testing laboratories and quality assurance teams to ensure traceability and repeatability of field tests.
Practical applications include reconnaissance in urban and infrastructure projects, preliminary and detailed subsoil investigations, and correlation of dynamic probe results to engineering soil properties.
Related standards (applicable)
- ISO 22476 series (field testing)
- ISO 14688‑1 (soil identification and description)
- ISO 22475‑1 (sampling methods and groundwater measurements)
- EN 1997‑1 and EN 1997‑2 (geotechnical design - Eurocode 7)
Keywords: ISO 22476-14, borehole dynamic probing, geotechnical investigation, field testing, N30, probe equipment, borehole testing, EN 1997.