France | Frankreich
Galerie des Janots: TBM hits two uncharted Caverns
In April 2019, a Robbins 3.5 m diameter Main Beam TBM broke through into open space, completing the 2.8 km long tunnel Galerie des Janots in France. It was not the first time the machine had encountered open space: twice during tunneling, the machine hit uncharted caverns, the largest of which measured a staggering 8000 m³ in size.
The water tunnel is located below the community of Cassis – an area of limestone known for its groundwater, karstic cavities, and voids. The limestone, combined with powdery clays, made for difficult excavation after the machine’s March 2017 launch. At the 1035 m...
