December 2025 Brings a New Standard for Geotechnical Strain Measurement in Civil Engineering

In December 2025, the field of civil engineering saw a significant advancement with the publication of EN ISO 18674-7:2025, focusing on geotechnical investigation and testing using strain gauges. This single but pivotal standard provides a comprehensive framework for the precise measurement of strains in structural members—critical for ensuring ground stability, robust construction practices, and safer infrastructure. Whether you are an engineer, quality manager, or compliance professional, understanding this new specification is vital for staying aligned with global best practices and maintaining competitive, compliant projects.

Overview / Introduction

Civil engineering is the backbone of safe, reliable, and sustainable infrastructure—from highways and dams to tunnels and retaining structures. At the heart of every successful project lies rigorous geotechnical investigation and testing, which provides essential data for design verification, safety assessment, construction quality, and post-construction monitoring.

Standards in civil engineering establish a uniform set of requirements, methods, and guidelines that professionals rely on for consistent and reliable project outcomes worldwide. The release of EN ISO 18674-7:2025 marks a significant update to the toolbox of geotechnical monitoring, zeroing in on the measurement of strain—a crucial parameter influencing design safety, structural integrity, and regulatory compliance.

In this article, you'll gain a clear understanding of:

• What this new standard covers and why it matters
• Key requirements and technical details
• Practical and strategic implications for industry players
• Compliance, implementation, and certification best practices

Detailed Standards Coverage

EN ISO 18674-7:2025 - Measurement of Strains: Strain Gauges

Geotechnical investigation and testing – Geotechnical monitoring by field instrumentation – Part 7: Measurement of strains: Strain gauges (ISO 18674-7:2025)

EN ISO 18674-7:2025 provides detailed procedures and technical requirements for measuring strain in geotechnical works using strain gauges and strainmeters. It outlines:

• The selection and installation of strain measuring instruments for different applications (surface-mounted, embedded, or instrumented reinforcement bars)
• Performance monitoring for a variety of structural members—including:
  • 1-D (piles, struts, anchor tendons)
  • 2-D (foundation plates, diaphragm walls, tunnel linings)
  • 3-D (dams, embankments, reinforced soil structures)
• Guidelines for converting measured strain into stress values for structural assessment

Scope and Applicability

This standard applies to all phases of geotechnical performance monitoring, from design validation and construction adjustment to ongoing safety evaluation. It's intended for:

• Design and build contractors
• Geotechnical engineers and consultants
• Monitoring and instrumentation specialists
• Compliance and quality managers in infrastructure projects

Key Requirements and Specifications

• Instrument Selection: Differentiates between strain gauges and strainmeters, with further classification for surface-mounted vs. embedded applications. Guidelines are given for gauge length, material compatibility, measurement range, placement, and installation procedures.
• Sign Conventions and Units: Brings consistency by prescribing geotechnical engineering sign conventions for strain, and requires clear documentation.
• Temperature Compensation: Mandates monitoring of temperature at measurement points and provides techniques for compensating for temperature-induced errors.
• Calibration and Reporting: Outlines procedures for instrument calibration, data validation, systematic reporting of installation and monitoring results.
• Design Integration: Supports observational design by enabling real-time feedback for design adjustments as ground or structural behavior changes.

Practical Implications

Organizations implementing this standard will benefit from:

• Enhanced ability to monitor ground movement, detect stress concentrations, and identify potential structural issues
• A foundation for data-driven decision-making on construction adjustments and safety interventions
• Alignment with global best practices and compliance benchmarks

Notable Changes from Previous Editions

• Expanded guidance for a wider range of instrument types, including fibre optic strain sensing (DSS and FBG)
• Improved installation and calibration procedures for real-world construction environments
• Greater emphasis on temperature effects and compensation methods

Key highlights:

• Applies to a broad range of structural members and monitoring scenarios
• Includes detailed requirements for instrument selection and placement
• Integrates temperature and calibration guidance for accurate strain measurement

Access the full standard: View EN ISO 18674-7:2025 on iTeh Standards

Industry Impact & Compliance

Adopting EN ISO 18674-7:2025 will have reverberating effects across the civil engineering industry, particularly in:

• Project Safety & Risk Management: Standardized strain measurement improves early detection of instability or overloading, enabling proactive risk mitigation.
• Regulatory Compliance: Incorporates international requirements that many governments and funding agencies now mandate.
• Quality Assurance: Consistent monitoring protocols reduce the risk of measurement errors, leading to better quality control.
• Project Costs and Scheduling: Real-time data enables quicker design and construction adjustments, potentially lowering unexpected remediation costs or delays.

Compliance Considerations

• Transition Timeline: Organizations should plan for adequate training and phasing in of new procedures, especially for ongoing or long-term infrastructure projects.
• Procurement: Specify compliance with EN ISO 18674-7:2025 in RFPs and supplier contracts for new instrumentation.
• Documentation: Maintain thorough records of calibration, temperature compensation, data processing, and reporting as specified by the standard.

Benefits of Adoption:

• Improved safety and reliability of earthworks and structures
• Demonstrable due diligence in risk assessments
• Smoother alignment with international partners on multinational projects
• Reduced legal and financial exposure related to monitoring shortfalls

Risks of Non-Compliance:

• Increased probability of undetected ground movement or structural failure
• Legal liability and regulatory sanctions
• Loss of market access for international infrastructure consortia

Technical Insights

Common Technical Requirements

The standard establishes key technical requirements for all geotechnical strain measurement:

• Instruments must not alter the stiffness of the monitored structure
• Gauge length should exceed the size of aggregates in the medium, maintaining a ratio > 5 or 6
• Strain gauges should be placed away from joints and ends—minimum three times the member width or diameter
• Integrated temperature monitoring is a must due to thermal effects

Installation Best Practices

• Surface Preparation: Critical to obtain clean and flat surfaces for accurate sensor mounting (grinding, sandpaper, etc.)
• Mounting Methods: Recommend spot-welding (for steel), adhesive bonding (for composite/FBG), and proper use of mounting blocks
• Protection: Safeguard sensors and cables from mechanical damage, weather, and corrosion (wraps, housing, protective tapes)

Testing & Certification

• Calibration: Pre-installation checks, post-installation validation, and regular recalibration are emphasized
• Temperature Calibration: Use of strain gauges compensated for specific materials (e.g., steel, aluminium) to minimize correction needs
• Reporting: Structured installation and monitoring reports are required, with clear documentation of all test and calibration steps

Conclusion / Next Steps

The introduction of EN ISO 18674-7:2025 is a major milestone for civil engineering professionals involved in geotechnical investigation, testing, and structural health monitoring. This standard equips the industry with more reliable, precise, and actionable data—empowering safer, more efficient infrastructure development worldwide.

Key takeaways:

• Enhanced clarity and consistency for strain measurement methods
• Expanded coverage of instrument types and temperature considerations
• Stronger alignment with global best practices and regulatory demands

Recommendations:

1. Assess your organization's current geotechnical monitoring procedures against the new standard
2. Update procurement, installation, and reporting protocols as necessary
3. Train teams on the latest instrumentation, calibration, and data evaluation requirements
4. Leverage the improved guidance for observational design and performance-based construction

Stay ahead: Explore the full standard, plan for implementation, and connect with the iTeh Standards platform for ongoing updates and additional technical resources.

Access the full standard: View EN ISO 18674-7:2025 on iTeh Standards