ISO 18674-2:2016

Overview

ISO 18674-2:2016 - "Geotechnical investigation and testing - Geotechnical monitoring by field instrumentation - Part 2: Measurement of displacements along a line: Extensometers" specifies methods for measuring linear displacements in the ground and structures using extensometers. It defines instrument types, installation and measuring procedures, data processing, evaluation and reporting to ensure reliable geotechnical monitoring. The standard is part of the ISO 18674 series and is intended to be used with ISO 18674‑1 (general rules) and, where directional components are needed, ISO 18674‑3.

Key technical topics and requirements

• Extensometer types: in-place extensometers (rod, wire, single- and multiple-point, chain), probe extensometers (single-point/magnetic and double‑point/incremental), and tape (convergence) extensometers.
• Components and instrumentation: anchors, connecting elements, measuring heads/read‑out devices, guide tubes, probes and convergence bolts.
• Installation procedures: requirements for surface components, installation in boreholes and fills, and specific guidance for in‑place, probe and tape extensometers.
• Measurement procedures: reference and follow‑up measurements, calibration, instrumentation checks, temperature corrections and assignment of sign convention (extension positive).
• Performance requirements: measuring range, accuracy, reproducible pulling force for tape extensometers, and verification of reference points (absolute vs relative measurement).
• Data processing & evaluation: methods to derive displacements along a measuring line and to compute relative/absolute movements (see normative Annex A for procedures).
• Reporting: standard content for installation reports and monitoring reports, including instrument calibration and measurement records.
• Definitions & symbols: consistent terminology (extensometer, gauge length, measuring point, etc.) for interoperability and quality assurance.

Practical applications and users

ISO 18674-2 is applicable to:

• Monitoring behaviour of soils, fills and rocks
• Stability assessment of slopes, embankments, excavation walls, foundations, dams, refuse dumps, tunnels
• Validation of geotechnical designs via the Observational Design procedure
• Deriving geotechnical parameters from pile load tests or trial tunnelling

Typical users:

• Geotechnical engineers and consultants
• Instrumentation and monitoring specialists
• Civil/structural contractors and site supervisors
• Tunnel, dam and earthwork project managers
• Regulators and asset owners requiring standardized monitoring records

Related standards

• ISO 18674-1:2015 - General rules for geotechnical monitoring by field instrumentation
• ISO 18674-3 - For determination of displacements acting in any direction (complements Part 2)

Keywords: ISO 18674-2, extensometers, geotechnical monitoring, displacement measurement, in-place extensometer, probe extensometer, convergence tape, borehole monitoring, observational design.