SURVEYING | TECHNICAL
“A significant advantage with Amberg Tunnel is all of
the construction guidance is based on parameters and reference points that we set and import into Navigator,” says Poloni. “We can define where a profile should be measured, how many points should be measured, at what interval, and at what accuracy. And we can completely lock it down so the production team just has to hit buttons as the software guides them. They can’t change the workflow or move forward if there’s an error or they haven’t done one step or measurement. “It gives surveyors tremendous freedom to manage
our tasks with the confidence that production will be done accurately and efficiently.” One primary job they perform is creating tunnel
profiles of the excavated surface and tunnel face after each blast––a routine they complete four times a day after every 5m (16.4ft) blast. Using guided workflows in the Navigator software,
they perform a resection with the total station to position the drill rig to drill blast holes along the tunnel face. Once each blast is complete, and it’s safe to approach the blast zone, they use the total station to measure a grid of points on the tunnel face. They then position the laser scanner by automatically measuring three mounted prisms, giving it absolute coordinates and tying it to the project’s coordinate system. The scanner captures a 3D view of the tunnel face
and excavated surface and immediately compares the point cloud measurements to the design on the tablet. That enables them to identify any overbreaks or underbreaks based on a pre-set, color-coded heat map. “Amberg Tunnel lets us set excavation design criteria
and color-coded deviations like red indicates -5 centimetres,” says Poloni. “With each scan, the software automatically calculates any design deviations from any point in the point cloud and produces a colored map. “So if they see any red on the map, they can use
Navigator to aim the total station’s laser to that exact point relative to chainage and design position and see the corresponding overbreak or underbreak. If they need to scale the wall to fix an underbreak, they can see their progress in real-time until they’re aligned with the design. It’s incredibly helpful and keeps them moving.” A scan also needs to be captured after each shotcrete
layer is applied. Similar to blasting, the production team uses project
control to position the shotcrete machine and directs it to spray shotcrete based on the current theoretical design and designated rock class. Once the lining has been applied they georeference the scanner and capture the section to produce a colorized 3D view. Using buttons on the tablet screen, they can select any
point in the point cloud, calculate it and see the layer thickness in real time. The software will compare the previous excavation scan to produce a heat map. If there are any deviations from the design, they can select that AOI, use the total station’s laser to point to the specific area and either reduce the shotcrete or apply more. They can then continue to scan and check until the lining meets the design.
Top: Tunnel profile corresponding point - Crews can immediately check shotcrete layer thickness by clicking on any point on the theoretical design profile on the tablet PHOTO CREDIT: AMBERG TECHNOLOGIES
Centre: After blast. The production team performs four blasts a day PHOTO CREDIT: MAXIME BOCRIE, EIFFAGE
Above: View of blast scanning data in Amberg Tunnel, with light green (left) corresponding to the excavation surface of a blast and darker green is the shotcreted surface SOURCE: AMBERG TECHNOLOGIES
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