C+S March 2021 Vol. 7 Issue 3 (web)

Grand Paris Express Project, L15B Tunnel. Monitoring systems provide insight to stakeholders throughout the construction project by automating the collection of 3D data which is used for real-time movement detection.

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 construc- tion by translating the 3D design into the real world. Robotic total sta- tions 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 tun- nel 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 resolu- tion of point cloud data available today supports more accurate volume and surface analysis during construction, in addition to painting a de- tailed 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 con- struction 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 tun- neling, 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 ana- lyze 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 comprehen- sive 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.



march 2021

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