EN ISO 22476-11:2017 PDF

Overview

EN ISO 22476-11:2017 - Geotechnical investigation and testing - Part 11: Flat dilatometer test (DMT) - provides standardized guidelines for equipment, execution and reporting of the flat dilatometer test. This ISO-adopted CEN standard describes the DMT procedure used in in situ geotechnical investigation and fulfils requirements of EN 1997‑1 and EN 1997‑2 for site investigation.

The flat dilatometer test uses a blade-shaped steel probe with a thin circular steel membrane mounted flush on one face. Two key pressure readings are obtained at selected depth intervals: the contact pressure when the membrane is flush and the pressure when the membrane centre reaches 1.10 mm deflection (with an initial signal at 0.05 mm). DMT results inform soil stratigraphy, in situ stress state, deformation properties and shear strength, and can detect slip surfaces in clays. It is most applicable to clays, silts and fine sands.

Key Topics and Requirements

• Equipment: Requirements for the dilatometer blade, membrane, pneumatic-electric cable, control and calibration unit, insertion apparatus and pressure source.
• Switch mechanism & signals: Internal blade switch that signals membrane deflections at 0.05 mm (A-pressure) and 1.10 mm (B-pressure).
• Measured pressures: Definitions and use of A-pressure, B-pressure and C-pressure (pressure when membrane returns towards A-position).
• Membrane calibration: Procedures to calibrate A and B membrane responses (air calibration pressures ΔA and ΔB) and gauge zero checks.
• Test procedure: Guidance on maintenance, insertion, sounding increments (commonly 100–300 mm), basic test sequence, dissipation tests (DMTA and DMTA‑s), and safety.
• Reporting: Required test documentation, site and equipment details, raw and corrected pressure data, interpretation notes and presentation of results.
• Informative annexes: Example interpretation formulae and references to other parts of the ISO 22476 series.

Applications and Users

Who uses EN ISO 22476-11:2017:

• Geotechnical and geotechnical site investigation engineers
• Engineering geologists and consultants
• Construction contractors and piling/subsurface works teams
• Testing laboratories and QA/QC personnel
• Regulators and authors of ground investigation specifications

Practical applications:

• Characterising soil stratigraphy and layering
• Estimating in situ stress, stiffness and deformation properties
• Assessing shear strength and detection of potential slip surfaces in clayey ground
• Complementing CPT, SPT and laboratory testing in foundation and earthworks design

Related Standards

• EN 1997‑1 / EN 1997‑2 (geotechnical design & investigations) - DMT fulfils their field-testing requirements
• Other parts of ISO 22476 (field testing series) for complementary in situ tests

Keywords: EN ISO 22476-11:2017, flat dilatometer test, DMT, geotechnical investigation, in situ testing, A-pressure, B-pressure, C-pressure, membrane calibration, dilatometer blade, soil stratigraphy.