Smart tunnelling

Tunnel construction is risky, with hazards such as flooding and cave-ins threatening not only workers and infrastructure involved in a project but also nearby buildings. Because of this, it is important to monitor the tunnel environment carefully—and as soon as possible. In an audience poll for Worldsensing, 63% of respondents said they would like to monitor pre-cast tunnel segments before installation, during the prefabrication stage. Yet this simply has not been possible until now.

Things have changed, however, with a smart tunnel innovation from Worldsensing. In Worldsensing’s smart tunnel solution, sensor equipment connected to the new vibrating wire RCR are embedded within the concrete segments installed right after a tunnel boring machine (TBM) passes, thereby avoiding costly delays in equipment installation and de-installation.

The vibrating wire RCR starts delivering data directly once embedded, allowing geotechnical teams to assess the integrity of tunnel lining segments even before they are used in the project. “The device can be configured and readings could be taken during the concrete curing process, installation and the lifetime operation of the tunnel,” explained Sam Buckley, Technical Sales Specialist at Worldsensing, in a recent webinar.

Smart tunnel solution innovations

The smart tunnel solution features several innovations, such as the use of ruggedized polymer casings and insulating resin to protect electronic components. The data logger’s antenna is positioned lengthwise inside the casing, so it does not protrude into the tunnel.

“A common question we get is, ‘How can we access the data logger once it’s been set in concrete?’,” said Buckley in the webinar. “It’s a very simple answer: the logger is placed very near the surface of the segment. It’s possible to chip away at this thin layer of concrete, exposing the logger lid to make any changes.”

When a TBM is in operation, interference from the machine will limit to the communications range between a data logger and a gateway to about 100m, said Buckley. Because of this, Worldsensing recommends placing a gateway at the head of the TBM to maximize data transmission. Once the TBM has moved on the effective transmission range is extended up to 3 km in a straight line or 800m around curves.

Reducing risks and costs

The VW RCR works with both edge and cloud gateways,” Buckley says. “Through the connectivity management tool, it’s possible to change the sampling rate, add corrections [and] calibrations, download the raw data, or forward it to third-party software.”

These innovations and more make it easier to reduce risks, simplify logistics and do away with cables, he said. “This is a wireless solution,” he commented. “The only cables are going to be connecting a sensor with a logger, so externally, out of the tunnel, there’s no cable.”

Worldsensing estimates the tunnel monitoring solution could result in a 25% reduction in time and effort dedicated to manual and dangerous activities such as equipment installation, minimizing the capital and operational costs associated with tunneling projects. One important area of saving is that since the monitoring equipment is embedded in the tunnel segments there is no need to stop tunneling while sensors are installed.

Construction