ISO 18674-4:2020

Overview

ISO 18674-4:2020 - "Geotechnical investigation and testing - Geotechnical monitoring by field instrumentation - Part 4: Measurement of pore water pressure: Piezometers" defines how to measure pore water pressure and piezometric levels in saturated ground using piezometers installed for geotechnical monitoring. The standard covers instrument types, installation and maintenance practices, measurement procedures, data processing and reporting - all focused on obtaining reliable pore pressure data for assessing ground behaviour and structural performance.

Key topics and technical requirements

• Scope and applicability: Measurement of pore water pressures in saturated ground for monitoring geotechnical structures, consolidation, stability and Observational Design checks. (Pore pressure measurements during CPT are covered in ISO 22476-1.)
• Instrumentation: Detailed coverage of open and closed piezometer systems, including:
  • Open systems (standpipes) and closed systems (fully sealed with diaphragm sensors).
  • Measuring devices: water level meters (manual), electric piezometers (strain‑gauge, vibrating‑wire, capacitive), fibre‑optic and pneumatic types.
  • Filters and filter tips: definitions and use of high air entry (HAE) and low air entry (LAE) filters and filter packs to control fluid/air exchange and protect sensors.
• Installation and measuring procedures: Requirements for borehole sealing, intake zone definition, checks before/during/after installation, and maintenance to ensure representative pore pressure measurements.
• Measurement quality: Guidance on measuring range, accuracy, absolute vs relative measurements, atmospheric compensation and intake factor concepts.
• Data handling and reporting: Procedures for data processing, evaluation and minimum contents for installation and monitoring reports.
• Annexes: Normative and informative guidance on measuring procedures, fully‑grouted installations, negative pore water pressure (suction), response time and protection of piezometers at ground level.

Practical applications and who uses ISO 18674-4

ISO 18674-4 is essential for geotechnical and civil engineering professionals who need reliable pore pressure data:

• Geotechnical engineers and consultants performing site monitoring for dams, embankments, slopes, tunnels, quay walls, dikes, excavation walls and foundations.
• Construction and monitoring teams conducting consolidation monitoring, settlement prediction and verification of design assumptions via the Observational Design approach.
• Instrumentation specialists and contractors specifying and installing piezometers, filters and data acquisition systems.
• Researchers and asset managers assessing long‑term stability, serviceability and groundwater–structure interactions.

Related standards (select)

• ISO 18674-1: General rules for geotechnical monitoring by field instrumentation
• ISO 18674-5: Determination of effective stresses (works with Part 4)
• ISO 22476-1: Cone penetration testing (includes pore pressure in CPT)
• ISO 22475-1: Sampling and groundwater measurement principles

Using ISO 18674-4 helps ensure standardized, repeatable pore water pressure measurements that improve the reliability of geotechnical monitoring programs and support safer, data‑driven decisions.