The World’s Largest Sub-Sea Road Tunnel.

In Norway’s fourth largest city Stavanger the site for the world’s longest sub-sea road tunnel is situated, named the Ryfast tunnel project. The project consists of three tunnels and aims to establish a permanent road link between Ryfylke and Jaeren and hopes also to tackle the traffic problems through the northern parts of the city centre.

The Solbakk tunnel is the main tunnel being constructed with a total length of 14km and construction began in August 2013. The two headings being excavated by drill and blast will reach a maximum depth of 290m below sea level (Statens Vegvesen, 2013).

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Documentation and Surveying of the Project.

The heading surveying tasks are being conducted by Marti AV Solbakk DA, and Sandvik drill rigs with automated drilling are in use for the blast headings. After each advance the tunnel crew has to check the blast independently.

As-built Analysis.

For the Ryfast project, both traditional total stations and 3D laser scanning technology were chosen. Total stations are being used for positioning the drill and to profile, while 3D laser scanning technology is in use for detailed as-built analysis.

The use of 3D laser scanning technology allows for routine surveying tasks to be carried out in a simple, efficient and independent manner. In addition, the laser scans give the tunnel crew 3D measurements immediately and unlike previously, whereby surveyors carried out the surveying, the task can now be undertaken by the tunnel crew in order to maximize the tunnel heading process and minimize deviation from the task on the construction site.

The total cost for the project is estimated to be around US$1 Billion and when finished, the tunnel will surpass the Shin-Kanmon tunnel in Japan as the longest underwater road tunnel in the world.

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