Tunnels built too close to each other?

What remains the cause of the crack in the ceiling is stress redistribution in the mountain. According to the “Sonntagszeitung”, they could come from excavation work in the mountain. What may be crucial is that the tunnels were built too close to each other at the damage site. In addition, the second tube will be connected to the existing A2, which requires a certain proximity of the two tunnel tubes in the portal area.

Too little space in Göschenen and Airolo

Normally the safety distance is more than three times the diameter of the excavated tunnel. The tunnel diameter is 14 meters. A distance of 70 meters is therefore planned. At the point of damage, however, the distance is significantly smaller, says Rohrbach. The space conditions in neither Göschenen nor Airolo allow a large distance between the portal.
Changes to the construction process possible

It is expected that the cause of the crack in the ceiling will be clarified in the next few days. Apparently they don't want to change the route in order to reach the 70 meter distance earlier. However, tunnel construction expert Hansruedi Kreusen warns: “As long as the cause of the ceiling collapse is not clarified, the possible further risks for the road tunnel cannot be assessed. However, if the investigations show that stress shifts are the cause, further such events would have to be expected. A careful assessment of the risks is therefore necessary - changes to the construction process may be necessary.