Di, Okt 17th 2023
Work on the second tube of the Gotthard road tunnel has not damaged the existing tunnel. The driving work, which was interrupted on September 10, will therefore be resumed. In future, however, blasting will be carried out more gently.
The Federal Roads Office (Astra) announced on Tuesday that all construction work would resume on Wednesday. This means that driving will also be resumed in the vicinity of the incident site.
On September 10, concrete parts had fallen from the ceiling of the Gotthard road tunnel onto the roadway in the area of the north portal. The 17-kilometer tunnel between Göschenen UR and Airolo TI was subsequently closed for five days.
The damaged intermediate ceiling had a 25-meter-long crack. Astra assumes that it was caused by movements in the rock mass. Work on the second tunnel tube was suspected as a possible cause of the movement. In the area where the tunnel ceiling was damaged, driving was stopped because of this.
In this regard, Astra gave the all-clear. The exact causes, which had led to the stress redistributions, are not yet finally clarified, the federal office communicated. However, an earthquake or a direct connection with blasting can be excluded. The last blasting had taken place more than 50 hours before the event that damaged the tunnel ceiling.
However, Astra decided “as a purely precautionary measure” to adjust the tunnelling. Blasting will be done “even more gently than before,” it said. Only one meter of rock will be cut off per blasting and no longer two meters. This would reduce vibrations. Because of the hardness of the rock, however, blasting cannot be dispensed with.
Adjustments were also made to the intermediate ceiling in the area of the north portal. The ceiling elements have been additionally fixed, Astra said. They also have more leeway to compensate for vibrations.
Astra stressed that the rock excavation was “strictly monitored” and that there were limits for vibrations. So far, these have not been exceeded. If they were exceeded, the work would be stopped immediately. In addition, there are also visual checks, he said.
The costs for the repair and safety work amounted to two million francs, Astra said. The incident has no influence on the commissioning of the second tunnel tube in 2029.
©Keystone/SDA
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