By Gabriel Neves
Keeping up with innovation and increasing productivity in the wake of increasing costs, tight deadlines, and sustainability issues means the infrastructure industry must embrace digitization. Construction and engineering teams are increasingly pressured to implement modern technology, digital workflows, and connected construction practices. Together, these elements facilitate better communication and smoother hand-offs and, in turn, enable earlier problem detection and resolution, streamlined operations, and faster project delivery.
Tunnel projects stand to greatly benefit from a connected construction approach that relies on a current, central source of truth about a project in which the digital world of modeling, imagery, measurement, and data is connected with the physical world of contractors, work crews, equipment, and the jobsite, at each phase of construction.
Starting with pre-construction planning and continuing through maintenance and operation, connected construction provides every stakeholder with the data needed to make well-informed decisions. From surveying and scanning to modeling and monitoring, technology is making this possible.
Constructible BIM with Parametric Modeling
Despite the vast efficiencies that come from digital modeling, tunnel design, and construction largely rely on 2D drawings and workflows. Given their geological complexities, the design, analysis, and construction of tunnels demand very careful coordination across many disciplines, including civil, geotechnical, structural, MEP, and drainage, which is a challenge with traditional 2D methods.
For complex tunneling projects, constructible BIM provides an accurate, dynamic, and data-rich 3D environment that can be shared across disciplines including architects, contractors, structural engineers, steel detailers, and fabricators, as well as concrete detailers and manufacturers. A constructible model can combine digital terrain and survey data to quickly and efficiently develop complete tunnel designs and, with a solution that utilizes parametric 3D modeling, accelerates design, and decreases the potential for errors.
With advanced BIM solutions that allow for parametric modeling, parameters are defined for the modeled objects, determining how those objects interact. This builds intelligence and eliminates the need for multiple inputs of the same data. A parametric model is automatically updated with any revision. Based on defined parameters, the effects of any change to a design are automatically populated throughout the model. This eliminates the need to manually apply changes across the model and allows engineers to quickly generate and visualize multiple iterations of complex designs in 3D by simply adjusting the parameters.
As work progresses, a constructible model can be continually updated at every step. By providing a single source of truth for everyone involved, the model gives work teams access to the always-current information they need to accurately track costs, identify and resolve issues, and stay on time and budget. At the same time, it helps facilitate communication and manage expectations with owners and other stakeholders.
Automated Surveying and Monitoring
Surveying technology plays an important role in connected construction by translating the 3D design into the real world. Robotic total stations and 3D laser scanning are two common methods for collecting 3D geospatial data on tunnel projects.
Robotic total stations utilize 3D designs for multiple tasks including set out of key features, machine positioning to construct the tunnel profile, as-built collection to verify construction activities, monitoring the tunnel structure and more. Robotic total stations provide the high-precision measurements needed for tunnel construction and quality control.
With advances in 3D laser scanning technology, the increased resolution of point cloud data available today supports more accurate volume and surface analysis during construction, in addition to painting a detailed picture of the constructed tunnel and assets. This data is used to verify and update the 3D model on the final position and characteristics of the tunnel.
Additionally, real-time monitoring software allows stakeholders to monitor critical infrastructure, such as buildings surrounding the tunnel construction site and inside the tunnel. Incorporated into a constructible 3D model, movement data can help engineers and other stakeholders mitigate risks to the public and construction workers from tunnel construction activities. Automated surveying and monitoring in tunneling can reduce the total time spent surveying and quickly identify issues, as well as provide measurements and data useful for stakeholders.
Automation in Action: The Grand Paris Express
Automated monitoring and surveying can be especially useful in tunneling, as was the case when building a new L15B tunnel as part of the Grand Paris Express, the largest subway and urban rail expansion in the western hemisphere. With houses, businesses and utilities nearby, engineering and construction companies, Eiffage GC and Razel-Bec, used the Trimble 4D Control monitoring platform to collect and analyze data from 25 Trimble S7 robotic total stations, and the Settop M1 wireless communication hub that allowed teams to operate the total stations and access cameras remotely, in real-time. This comprehensive monitoring system was used to check for movement related to trenches being dug during and after construction.
The teams also performed as-built surveys to check the fidelity of the bored and lined tunnel rings as compared to the constructible model and provide construction crews with precise measurements. Underbreak/overbreak analysis routines in Trimble Access survey field software helped ensure proper placement of the arched tunnel lining, comparing measured data to the designs and providing results to workers on-site, in real-time.
The Trimble SX10 scanning total station combines the robotic total station and 3D laser scanning abilities into one instrument. This provided construction surveyors with the ability to collect automatically georeferenced point cloud data of the tunnel lining to verify the construction process vastly reducing processing time in the office. Combined with Trimble Business Center office software, surveyors were able to automatically remove noise from the collected point cloud and generate detailed as-built reports.
A New Way of Working
More efficient tunnel design and construction require collaboration, automation and data sharing, all made possible by advances in technology. Harnessing the technologies available today can bring long-overdue productivity improvements to tunnel design, construction, and maintenance. With connected construction, siloed workflows and teams become a thing of the past.
In addition to reducing the risk of human error and enabling faster, more efficient workflows, technology fills the gaps that historically exist in tunnel construction, linking teams across disciplines and locations—from the office to the jobsite to the fabrication shop—in ways that simply aren’t possible with traditional, typically manual tools and methods.
Gabriel Neves is Bridges Technical Manager at Trimble, Structures Division and Ministry of Bridges YouTube channel Content Creator.