Danish civil engineering monitoring specialist Worldsensing has launched an innovation that will allow monitors to be installed and activated as the tunnel lining is installed, improving safety and efficiency.

Currently, the tunnel excavation process has to be paused at intervals to allow monitors to be installed into the lining’s inner surface. This can take hours, is costly and involves engineers entering tunnels that do not yet have monitors in place, which means the security of the structure is not assured and risk is higher.

These issues are eliminated by Worldsensing’s innovation, which embeds the sensor equipment within the concrete segments before they are installed by the tunnel boring machine (TBM).

The sensors are housed within a rugged polymer casing that can be embedded directly into the concrete segments, with the casing sitting flush with the inner surface of the tunnel lining. All electronic components are protected with insulating resin. The only part that remains open us the USB port, which could be needed for configuration purposes.

The embedded sensors allow engineers to receive data about the tunnel lining’s stability as soon as the segments are installed. The sensors can immediately send data up to 100m away to a gateway installed in the head of the TBM, giving engineers almost instantaneous information. Once the TBM has moved far enough away that it stops interfering with the data transmission, the communications can be sent to other gateways up to 3km away in a straight line or 800m around curves.

The monitoring units include Worldsensing’s five-channel data logger that transmits data throughout the lifespan of the lining and is compatible with any industry-standard visualisation software. They are powered by batteries that can last up to 10 years.

Worldsensing estimates that this could reduce the time and effort involved in tunnel construction by up to 25%. It is also expecting to see the innovation used on other types of construction, including shafts, bridge pillars, diaphragm wells, precast foundations and more.

Worldsensing director of global sales Matthieu Laville said: “This innovation represents a major step forward in tunnel boring safety and efficiency. We can now drastically reduce the delays involved in installing and configuring tunnel monitoring systems, saving time and costs. Because the technology is completely based on wireless there is no need for costly and time-consuming cabling and splicing work once the TBM has moved on.

“Embedding monitoring equipment directly into the concrete lining in tunnels is a simple yet highly innovative idea that simplifies logistics during tunnel construction by minimizing the need for later installation work.”

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