- Challenges: Hard Norwegian rock and water pressure. Fernando Vara, global business development director for ACCIONA’s railways and tunnels specialised business unit, explained the main difficulties that the company has faced on one of Norway’s most ambitious infrastructure projects.
On Thursday 15 July, ACCIONA took part in a conference organised by the Tunnelling and Underground Construction Society of Singapore (TUCSS), which was held online due to health restrictions.
Fernando Vara, global business development director for ACCIONA’s railways and tunnels specialised business unit, shared with around 500 members of the TUCSS the main challenges that the company has faced during construction of the 40 km of tunnels for the Follo Line project, primarily related to the complex local geological conditions. The characteristics highlighted during the presentation included the type of rock in Norway (one of the hardest in the world) and the presence of fractured rock zones along the entire length of the route combined with high ground water pressure, which required the tunnel to be kept watertight at all times while preventing the level of the water table from falling.
Vara also explained during his talk how ACCIONA was able to solve these issues thanks to the pre-grouting technique used by the tunnel boring machines (TBMs), good planning and excellent maintenance of the cutter heads (the cutting tools used by the TBMs), managing to complete the drilling of the tunnels ahead of time and without any major unforeseen events.