Issue link: https://geospatial.trimble.com/en/resources/i/1480692
To address congestion in densely populated cities, transportation engineers and city planners are increasingly turning to tunnels. The Rotterdamsebaan tunnel currently under construction beneath The Hague exemplifies the new era in urban tunnel construction. It is efficiently built, environmentally friendly and designed to mitigate any impact on urban centers. The approach includes extensive monitoring to detect any surface motion resulting from the tunneling process. overview Location NETHERLANDS TRANSFORMING THE WAY THE WORLD WORKS TRANSFORMING THE WAY THE WORLD WORKS While modern tunnel boring machines (TBMs) are designed to minimize ground movements caused by the tunneling process, there will always be some ground reaction. Monitoring the Rotterdamsebaan construction put a premium on the instrumentation and skill of the monitoring teams. The Hague city council contracted Fugro to oversee the monitoring process. An international leader in geospatial measurements, Fugro would monitor the impact of the project on infrastructure along the tunneling corridor. BEST PRACTICES FOR MONITORING To monitor large projects, Fugro utilizes multiple robotic total stations such as the Trimble® S9 arranged in networks in and around features to be monitored. On a project of this magnitude, forty or more total stations may be in use at any given time. The total stations are situated to have clear views of all building and surface features monitored for deflection. Typically each total station is mounted on a small platform bolted to the sides of buildings or poles where they can capture a panoramic view from above the site. When the mounts are close to businesses or residences, noise generated by frequent rotations of the total stations may be irritating to the occupants. This isn't a problem with the Trimble S9 though, which uses MagDrive™ technology to provide silent operation. To connect the total stations into the reference networks, Fugro placed target prisms on buildings and chimneys that can be seen by at least two total stations. "We form networks that can be constantly measured and checked with the least squares adjustments," said Richard Bun, Fugro project manager and geodetic engineer.