Underground Mining Traffic tunnel construction
a twin-tube road tunnel with branching structures
The Eyholz main tunnel is a multi-lane motorway tunnel with two tubes, which was built in the context of the overall project known as “A9 section Gampel - Brig - Glis (Visp West - Visp East)”. The two main tubes are 4,250 m long and have an excavation cross section of 100 m². The tunnel tubes are situated partly in blasting rock and partly in soft ground. The excavation work for the two tubes was demanding, the geology difficult. It was a matter of building not just the two main tubes but also two complex branching structures with excavation cross-sections of up to 300 m², 16 cross-connections and 523 m of access and exit tunnels. The tunnelling in soft ground was carried out with the protection of jetting screens, the rock excavation was conducted by blasting according to NATM. Up to the completion of the excavation work in October 2012, 1.3 million m³ of rock and loose material was excavated for the creation of the entire tunnel system. Interior work began at the same time as the excavations in 2010. With 6 arched formwork carriages, 3 base formwork carriages and 3 intermediate ceiling formworks, the volume of concrete installed per day amounted to up to 1,061 m³. By the end of 2014 a total 480,000 m³ of lining concrete had been used. On 21 November 2014, the southern tube was completed and handed over; the handover of the northern tube took place in 2015.