Overcoming Multiple Caverns: Successful TBM Tunneling
in Karstic Geology at Galerie des Janots

1 The excavation of the Galerie des Janots Tunnel in France took two years to complete due to challenges including two uncharted caverns – the largest of which measured a staggering 8 000 m³ in size Credit/Quelle: Robbins
1 The excavation of the Galerie des Janots Tunnel in France took two years to complete due to challenges including two uncharted caverns – the largest of which measured a staggering 8 000 m³ in size
Credit/Quelle: Robbins
2 The small jobsite for the Galerie des Janots, a 2.8 km long tunnel to improve water supply in the French communities of Cassis, Roquefort-la-Bédoule, La Ciotat and Ceyreste Credit/Quelle: Robbins
2 The small jobsite for the Galerie des Janots, a 2.8 km long tunnel to improve water supply in the French communities of Cassis, Roquefort-la-Bédoule, La Ciotat and Ceyreste
Credit/Quelle: Robbins
3 The weak rock and clay conditions necessitated ground support including resin-anchored bolts and rings in bad ground Credit/Quelle: Robbins
3 The weak rock and clay conditions necessitated ground support including resin-anchored bolts and rings in bad ground
Credit/Quelle: Robbins
4 Filled karst cavities with water and mud were also encountered in the first 1000 m of boring, and these often needed to be drained and then filled with foam Credit/Quelle: Robbins
4 Filled karst cavities with water and mud were also encountered in the first 1000 m of boring, and these often needed to be drained and then filled with foam
Credit/Quelle: Robbins
5 Crews erected a 4 m high wall of concrete so the TBM would have something to grip against, allowing them to pass by the cavern in about eight TBM strokes Credit/Quelle: Robbins
5 Crews erected a 4 m high wall of concrete so the TBM would have something to grip against, allowing them to pass by the cavern in about eight TBM strokes
Credit/Quelle: Robbins
6 At the 2157 m mark, the machine grazed the top of an unknown cavity. A Speleologist roped off and descended to map the extent of its size. The new cavern was estimated at about 22 m long, 15 m wide, and 14 m deep, or about 4500 m³ of open space Credit/Quelle: Robbins
6 At the 2157 m mark, the machine grazed the top of an unknown cavity. A Speleologist roped off and descended to map the extent of its size. The new cavern was estimated at about 22 m long, 15 m wide, and 14 m deep, or about 4500 m³ of open space
Credit/Quelle: Robbins

In April 2019, a 3.5 m diameter open-type Main Beam TBM and its crew broke through at the Galerie des Janots Tunnel in La Ciotat, France. The 2.8 km long tunnel, excavated in limestone known to have groundwater, karstic features, and voids, took two years to complete due to challenges including two uncharted caverns – the largest of which measured a staggering 8000 m³ in size (Fig 1).


Upgrading the Water Supply

Galerie des Janots is one of the 14 operations designed to save water and protect resources, which are being carried out by the Aix-Marseille-Provence metropolis, water agency Rhône Mediterranean Corsica, and the French State Government. The Janots gallery will improve access to water in the communities east of the Aix-Marseille-Provence metropolis (Cassis, Roquefort-la-Bédoule, La Ciotat and Ceyreste). The future pipeline will replace existing pipelines, currently located in a railway tunnel, that have significant safety and vulnerability deficiencies with...

Find out more in

tunnel 04/2019

Find out more in

tunnel 04/2019

Ressort:  Hauptbeiträge | Main Articles
subscription Content

DESIREE WILLIS, Technical Writer/Technische Redakteurin, The Robbins Company, Kent, WA/USA


Related articles:

Overcoming Multiple Caverns: Successful TBM Tunneling in Karstic Geology at Galerie des Janots

Upgrading the Water Supply Galerie des Janots is one of the 14 operations designed to save water and protect resources, which are being carried out by the Aix-Marseille-Provence metropolis, water...

more
Issue 03/2019 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...

more
Issue 08/2010

Access Adit I for Kraftwerke Linth-Limmern

Lot A1 is a component of the Linthal 2015 project for Kraftwerke Linth-Limmern AG (KLL), which will include comprehensive expansion of KLL‘s facilities. An additional balancing reservoir is to be...

more
Issue 03/2017

Tunnelling in Malaysia

In Malaysia, tunnelling took on an important change in 2003 when there was an acute need to address major flooding issues in the city of Kuala Lumpur. With the city densely built up to the brims, the...

more
Issue 04/2015

Albabstieg Tunnel: Karst Probing and Treatment Measures

The article includes selected investigation results and the corresponding treatment measures. The decision, whether and what treatment measures are necessary, is made on the basis of general...

more