Excavation of the 2.1km Kaiserstuhl Tunnel in Switzerland has been completed.<\/p>\n
Frutiger AG began building the tunnel \u2013 the centrepiece of the expansion of the A8 between Lungern and Giswil in the Canton of Obwalden \u2013 in July 2024.<\/p>\n
The tunnel is built as a helical\/curved structure, overcoming a 135m elevation change with a 6.5% longitudinal gradient and an 80km\/h design speed. It also includes parallel safety and escape tubes.<\/p>\n
The steep gradient and narrow lines meant using a TBM was impossible. Tunnelling was carried out from the north and south, with drill-and-blast methods used to excavate 1.56km, while 313m was constructed using cut and cover, and 215m by soft tunnelling.<\/p>\n
From the north, miners advanced the tunnel using drill-and-blast, with round lengths of up to 4m. Rock conditions were favourable for about two-thirds of the route, allowing for a consistent weekly advance rate of around 30m. Excavation proved more challenging during the final third as the layering siliceous limestone and water ingress slowed progress.<\/p>\n
To optimise the construction programme, the final 35m were excavated from the southern heading using machine-assisted excavation in rock, bringing the two tunnel sections together and enabling the breakthrough.<\/p>\n
From the south, approximately 200m had to be excavated through loose rock. Insights gained from a previously constructed exploratory adit led to an adjustment of the excavation method. Jet grout columns were used to stabilise the rock before excavation.<\/p>\n
The tunnel, which is designed to improve road safety and protect motorists from rockfalls, avalanches and floods, is scheduled to be commissioned in late 2029.<\/p>\n","protected":false},"excerpt":{"rendered":"
Excavation of the 2.1km Kaiserstuhl Tunnel in Switzerland has been completed. Frutiger AG began building the tunnel \u2013 the centrepiece of the expansion of the A8 between Lungern and Giswil in the Canton of Obwalden \u2013 in July 2024. The tunnel is built as a helical\/curved structure, overcoming a 135m elevation change with a 6.5% longitudinal gradient and an 80km\/h design speed. It also includes parallel safety and escape tubes. The steep gradient and narrow lines meant using a TBM was impossible. Tunnelling was carried out from the north and south, with drill-and-blast methods used to excavate 1.56km, while 313m […]<\/p>\n","protected":false},"author":5,"featured_media":20609,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4001],"tags":[5612,346],"class_list":["post-20608","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-contract-projects","tag-kaiserstuhl-tunnel-excavation","tag-switzerland","post--single"],"yoast_head":"\n