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Final breakthrough in Ski achieved

26 Feb 2019

Another important milestone was reached when the tunnel boring machines (TBMs) Anna and Magda appeared in Ski this afternoon after nine kilometers of hard rock drilling.

The hard-working ladies started their journey from Åsland in the fall of 2016, and after just over two years of continuous production, they have reached their goals in Kvakestad just beside Ski Center. About 350 invited guests witnessed a spectacular double breakthrough when the last two TBMs completed their missions.

The TBMs have excavated rock using cutter disks in the cutter head at the front of the machine. The rotation of the cutter head combined with the trust from the forward movement of the front shield causes the cutter disks to penetrate the rock in front of the machine. The excavated rock slides down inside the cutter head on to a conveyor which transports the spoil from the tunnel worksite through an underground conveyor belt. As the cutter head excavates the rock in front of the machine, the rear section of the TBM installs the concrete segments creating the reinforced tunnel wall. Seven concrete segments is needed in order to assemble one complete tunnel ring. From the construction area in Åsland, an internal concrete element factory with three production lines continuously supplied the TBMs with elements to the tunnel. In total, 20,000 complete rings, or 140,000 concrete elements, have been produced.

In total, approximately 18,000 working hours have been spent on each TBM, divided into four shifts a day. Together on the two TBMs, 112 employees have been involved in production, while 24 have worked on maintenance. Each employee has worked an average of 33.5 hours per week. Production has been going on every day since the start, with the exception of Sunday.

Now dismantling TBMs and shipping back to Germany remains.

- Thanks to the strong emphasis on quality, safety, innovation and expertise, Acciona Ghella Joint Venture has delivered an effort we are proud of. We have produced more than 18 kilometers high quality tunnel, we deliver on schedule and we keep what we have promised. There have been challenges with the ground conditions in the direction of Ski, and the journey has not been easy. We have now got useful experience from challenging Norwegian ground conditions and we are pleased to manage such a huge and demanding TBM-project. Now we are moving into a new phase, and we are confident that we will do a good job also in the remaining work with rail technology, says project director Fernando Vara in AGJV.

The next phase in tunnel production is the installation of railway technology, which is also part of AGJV's mission. Planning these operations has already started. The further assignment will consist of concrete works, preparation of tunnel walls and catenaries, walkways and technical rooms. Telecommunications, railway tracks, power supply and ventilation are also elements in this process. This work is expected to be completed in about two years.