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Intelligent Tunnel Segments

A patented solution for monitoring the stress state of concrete tunnel segments

Sixense, in collaboration with World Sensing, has developed an intelligent tunnel segment datalogging solution that fundamentally changes how tunnel linings are monitored throughout their lifecycle.

Instead of installing instrumentation after construction, the system embeds sensors and autonomous data loggers directly within the precast concrete segments during their manufacture.

These “intelligent segments” are therefore capable of recording structural behaviour from the earliest stages – starting with concrete curing, through to transportation to site and subsequent installation, and continuing throughout the operational life of the tunnel.
 


 

At the core of the solution is a robust, multi-channel datalogger connected to sensors such as vibrating wire strain gauges or pressure cells. These components are encased in a protective housing and cast directly into the segment, allowing them to withstand harsh construction conditions while remaining fully operational.

Once installed in the tunnel lining, the datalogger continuously collects measurements related to stress, strain, and overall structural performance. Data is transmitted wirelessly to nearby gateways—initially located on the tunnel boring machine (TBM), and later along the tunnel itself—providing engineers with near real-time insight into the stability of the lining without interrupting construction activities.


 

The applications of this intelligent datalogging solution are extensive and highly impactful. During construction, it enables continuous verification that tunnel segments are not subjected to excessive loads from handling, assembly, or ground conditions, significantly improving worker safety and reducing the need for risky manual installations.

In the long term, it supports structural health monitoring by tracking how stresses evolve due to environmental changes, ageing, or operational loads. This continuous data stream allows asset owners to adopt a data-driven maintenance strategy, anticipate potential issues before they become critical, and extend the service life of the infrastructure.

By combining embedded sensing with wireless data transmission, Sixense and World Sensing provide a scalable, low-maintenance monitoring system that enhances both efficiency and safety across modern tunnelling projects.

Follow stress state of segments in the long term

The challenges related to prefabricated elements

Understanding the stresses in prefabricated segments is critical both during the construction phase of the structure (tunnel or viaduct) and for monitoring its health throughout its lifecycle.

During construction, it’s essential to monitor the stresses endured by the segments to ensure they do not exceed permissible limits. These forces arise from transport and handling, placement, assembly, and the construction sequencing of the subsequent structure.

In the final phase, monitoring the stresses in the segment helps to ensure it is not subject to new stresses due to environmental changes. The stress state also serves as a good indicator of the element’s aging condition.

Our Solution

  • Measures micro deformation using vibrating wire strain gauges
  • Stress calculation by Hooke’s law: σ = E x ε
  • Strain gauges connected to a small, wireless, autonomous logger integrated into the segment
  • Continuous recording
  • Data retrieval using an IoT communication gateway via long-range radio
  • The option to adjust the measurement frequency depending on the construction and monitoring phase
  • Use of long-life batteries (lifetime > 10 years for an acquisition every 6 hours).
    Access to the logger for battery replacement is available.

Applications

  • Tunnel segments
  • Bridge & Viaduct Segments
  • Any other structural concrete element (prefabricated or cast in place).

The benefits of our patented solution

Long-term solution

Known stress state from the initial casting of the tunnel segment throughout its lifecycle.

Automatic device

Automatic and continuous measurements, with possible alarms.

Solution for observational method

Knowledge of the stresses in the element allows for back-analysis and optimisation of future structures. It’s an essential measure for implementing an effective observational method.

Long-term monitoring

 Intelligent segments facilitate long-term monitoring of the structures they comprise.

Solution for innovative materials

They are indispensable tools for monitoring structures made with innovative materials (low carbon, ultra-low carbon materials, and others).