Overview
EN ISO 22476-7:2012 - Geotechnical investigation and testing - Field testing - Part 7: Borehole jack test (ISO 22476-7:2012) specifies equipment requirements, execution and reporting for the borehole jack test. The standard covers in-situ testing where two diametral cylindrical steel loading plates are placed in a drilled pocket and hydraulically opened to measure pressure versus plate opening. Measured pressure and displacement produce a stress–displacement relationship used for ground deformation and foundation design. The procedure applies to tests on land or offshore at depths up to 100 m in ground stiff enough not to be adversely affected by drilling.
Key Topics
- Scope and applicability: test depths ≤ 100 m, land and offshore use, ground stiffness criteria.
- Equipment requirements: borehole jack device, hydraulic pump, measuring unit, cables and transducers.
- Test execution: pocket drilling and device placement, loading programme (loading/unloading cycles), constant-load tests, back-filling and safety procedures.
- Calibration and corrections: device calibration, correction factors and uncertainty assessment (references include ISO 10012 and ISO/IEC Guide 98-3).
- Data and reporting: recording pressure and expansion vs time, basic equations for analysis, presentation of stress–displacement curves and recommended report content.
- Annexes: device dimensions, calibration details, field report example, placement guidance, and uncertainty/resolution guidance.
Applications
- Foundation design: deriving in-situ stiffness and modulus for shallow and deep foundations where applied stresses match design ranges.
- Ground deformation analysis: input for settlement and lateral deformation calculations for embankments, retaining structures and foundations.
- Offshore geotechnics: characterizing seabed and sub-seabed stiffness for jacket or piled structures (within the ≤ 100 m depth range).
- Site investigation programmes: complementing sampling and classification (ISO 22475-1, ISO 14688-1, ISO 14689-1) to provide in-situ mechanical behaviour data.
Typical users: geotechnical engineers, site investigation teams, drilling contractors, offshore engineers, and geotechnical testing laboratories.
Related Standards
EN ISO 22476-7:2012 is essential when you need standardized, repeatable borehole jack testing procedures and reliable stress–displacement data to support geotechnical design and risk assessment.
