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 5-m 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 centimeters,” 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. Without the processing automation of the software, teams would have to manually verify the shotcrete by drilling holes in the lining in a grid pattern and measuring its depth. That’s not only laborious, it would require more personnel and would be more susceptible to errors. Along with all the blasting and shotcreting has been positioning and installing varied bolts such as rock bolts––a task the tunneling team can do autonomously with a dedicated workflow in Navigator. Performing a resection with the total station, they establish the rig’s position and import the coordinates into the rig’s cab. The operator then follows a predefined bolt plan to install the georeferenced bolts. “Giving them the independence to blast, shotcrete, install bolts, and compare and calculate on the fly makes us so much more efficient,” says Poloni. “They don’t need to wait for us to advance, which greatly
A production team member monitors the application of shotcrete. Image credit: Eiffage Norway.
Production crew personnel prepare for the next blast by loading blast holes. Image credit: Maxime Bocrie, Eiffage.
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csengineermag.com
Summer 2024
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