The methodologies and workflows driving the design and construction of tunnels have changed considerably over the years. The rise of digital standards, 3D/4D/5D design models, reality capture and other technology advances are coming together to create more seamless workflows, timely insights and smart monitoring. They are improving accuracy, speed and flexibility, and adding automation.

A task that used to require days or sometimes months of in-field data gathering, and considerably more time in the office analyzing, evaluating convergence or moving data between solutions, is now remarkably streamlined. Technology enables project teams to handle and analyze mass amounts of data with speed. Further, scan data and design-based BIM (building information modeling) models can be linked and utilized with other resources from design simulations to real-time earthwork activities.

Following are three areas topping the list of technology trends foundational to tunnel survey construction, maintenance and monitoring: sensor fusion, artificial intelligence (AI) and deep learning, and common data environments (CDE).

Melding Data

A significant evolution in tunnel construction and, in fact, across the construction industry, has been the move from singular-point solutions that perform one activity to single devices that fuse multiple sensors. For example, LiDAR, inertial measurement units (IMUs) and imaging cameras are commonly "fused" to operate in one usable device.

Leveraging new technologies that combine 3D laser scanning, high-resolution imagery and video drive productivity. As well, high accuracy optical measurements with infield computing devices provide real-time construction quality control and guidance for drill and blast or shotcrete operations. With these combined sensors, surveyors can increase productivity by up to 70%, while reducing rework and waste and construction down time all with greater accuracy during tunnel surveying.

For example, conventional practice might call for a total station to measure vertical and horizontal angles and distances, a laser scanner to capture tunnel surfaces and a high-resolution camera to provide high quality digital images. Today, those sensors are combined into one system for a much more complete and integrated data gathering experience across the lifecycle of a project. A total station/laser scanner solution supports underground construction surveys along with tunnel boring machine (TBM) guidance, but also helps stake out key features such as rock bolts, anchors, blast holes, guide-road headers, drilling jumbos and other construction equipment.

It’s already being put to use on New Zealand’s $4.4 billion NZD ($3.2 billion USD) City Rail Link (CRL), which will build a 3.45-kilometer twin-tunnel underground rail link below the city center. In this case, surveyors are using the Trimble SX12 for set outs, volume calculations and as-builts. All data is gathered in one set up, boosting efficiency, precision and speed.

Sensor fusion also provides operational and business advantages. Three separate systems require additional investment, maintenance (calibration) and, perhaps more challenging in today’s environment, more complex data management. It’s time consuming and can be complicated to combine the data from multiple systems into an easy to visualize and comprehensible report.

With sensor fusion, not only are contractors changing the way in-field operations are performed but also how project teams utilize data and designs to communicate and connect stakeholders for greater transparency.

AI and Automation

Whether a survey and construction team is using multiple point solutions or one system to do several tasks, data management likely remains a challenge.

That’s where AI comes into play, facilitating site optimization, task sequencing, material logistics, data processing, etc. Already, field-to-finish survey and construction management software incorporates deep learning capabilities that support automated point cloud classifications and higher accuracy feature extraction.

With AI capabilities, tunnel features such as shotcrete versus rock surface, duct work, people and machinery can be segmented automatically to a high degree of accuracy and reliability.

While working on the Maursund and Kågen undersea road tunnels in Norway, Sylvia De Vuyst, a professional surveyor with Mesta AS, relies on the AI functionality to automatically clean and process the data to create a tunnel shape. It’s a process that takes three minutes per scan. She said, “Without the automatic classification tool in TBC, I'd have to manually select each bit of noise and delete it. That feature, along with the automatically georeferenced scans, saves me hours of processing time. And because I know I can eliminate noise automatically, I don't worry about passing traffic or objects in the way.”

Across the Lifecycle

It’s not enough to capture data in today’s environment; project teams need to communicate it in a way all stakeholders can understand to confidently make better informed decisions.

Too often, data from a construction project is gathered for a particular purpose, say to verify the construction meets a project specification, but then it's not used again. There’s considerable value of data gathered during construction that could support operations and maintenance. A common data environment (CDE) helps ensure data doesn’t go to waste.

These repositories centralize project data storage and access, typically related to a construction project, often with a BIM or intelligent 3D model foundation. It also includes documents such as contracts, material specifications, and other information relevant to a project’s design and construction processes.

Many CDE that exist today allow multi-disciplinary project stakeholders to access the platform anytime and anywhere using a computer, mobile phone, tablet or machines in the field. Essentially, the data has a platform to live through the lifecycle of an asset, including maintenance and operations.

On the Bergünerstein Tunnel project in Switzerland, Donatsch + Partner AG relied on a CDE to enable the seamless transmission of data and provide easy access to the most current design. With participation from all parties, the centralized data approach resulted in the efficient management of design updates, expedited volume calculations and comparisons of as-builts to design, smooth communication between stakeholders and the establishment of a faster, more transparent decision-making process.

For example, Donatsch was responsible for calculating excavation and shotcrete volumes. The team used laser-scan data to create profiles for over/under excavation analysis that were compared to the 3D model to identify areas that required rework. The cloud process allowed Donatsch workers to track progress, identify gaps and connect design revisions and changes to all stakeholders seamlessly and uniformly.

Aligned for Opportunity

Technology is advancing at a rapid pace in the construction space. Along with that progression, the barrier to entry is reduced. Today, it is common practice to leverage payloads and sensors to autonomously capture tunnel conditions on a scheduled basis.

It’s important that tunnel construction firms of all sizes talk with their technology partners about current capabilities and what’s on the horizon. Ask about sensor fusion and how to embed AI into current software features and functionality. And lastly, take a step back and look at how data on projects is managed. Look for ways to leverage sensor fusion, AI and deep learning, and a CDE to facilitate tasks with ease and streamline communication with all stakeholders.

Tunnel surveying and construction is a complex business—and no amount of technology is going to change that fact. However, today’s advancements can offer more seamless workflows, real-time insights, better accuracy, greater visibility and flexibility—all critical elements of any successful tunnel construction or monitoring project.