Development of new jet grouting equipment is helping to keep construction of the Koralm Tunnel in Austria on target, Keller has said.
Challenging ground conditions on the new rail route led to innovations for the rigs, pumps, monitors and nozzles to allow for faster jet grouting that uses less cement which will benefit future projects.
Keller is working on two tunnels on the Koralm rail line which will reduce travel time between the cities of Graz and Klagenfurt from three hours to less than one when it opens in 2023.
Construction on the cut and cover tunnel has been completed but bored piling and soilcrete columns for the Untersammelsdorf tunnel presented a number of engineering challenges.
“Not only is this a very large project, but it’s also unique because of the difficult soil conditions,” said Keller project manager Christoph Deporta. “In many areas there are silty still-water sediments – lacustrine clays – making the ground inconsistent, and ranging from soft to semi-solid. The conditions were not ideal so first we had to execute three trial fields in different areas of the site and soil conditions to show the client we could guarantee the diameter and strength of the soilcrete columns.”
Rigs have also been fitted with GPS technology, which Keller reports has doubled the speed of relocation and construction.