"After a year and a half of hard work and many challenges, we were finally able to celebrate the breakthrough of the Exploratory Tunnel Kaiserstuhl on July 14, 2022. We are very pleased that we were able to complete this stage successfully and without serious accidents, and we are particularly grateful for the joint efforts and the cooperation of everyone involved"," says our on-site site manager @Carolina Camus.
An important milestone was reached with the breakthrough of the exploratory tunnel in the major A8 project from Lungern North to Giswil South. The approximately 1'750-meter-long exploratory tunnel provides important information for the construction of the main tunnel and will be used as a safety and escape tunnel in the final phase.
With the sharpening on January 25, 2021, the excavation of the exploratory tunnel started. On July 14, 2022 - around one and a half years later - building director Josef Hess was able to detonate the last blast.
The approximately 1'750-meter-long drive was characterized by demanding geological conditions. While particularly hard rock made work difficult for the miners in the north, exactly the opposite was the case in the south. Loose rock together with water ingress made driving from the south more difficult. This section with a length of 190 meters was executed as a machine-supported loose rock drive with a tubular umbrella.
The first 100 meters of the main drive from the north had to be excavated in very hard rock in painstaking detail work until after crossing under the EWO pressure line to the Unteraa power plant. The subsequent 1460 meters were excavated using blasting. With two to four blasts per day, the miners achieved an average rate of advance of 10 meters per day.
The excavation of the exploratory tunnel provided important information for the construction of the main tunnel. The geological conditions are now known and this knowledge will now flow into the tender for the main tunnel. Construction of the main tunnel is planned to start in 2024 and is expected to take five years.
Congratulations also go to our site manager Carolina Camus for the work she has done, who, along with site management experience in tunnel construction, has gained an excellent reputation in the canton of Obwalden.