"Société de Construction de l’Autoroute de la Traversée de l’Ouest Parisien" - that is the fully spelled out name of the joint venture that took up the challenge of an outstanding tunnel project east of Paris. Its abridgment SOCATOP became a prominent entry in the history book of mechanized tunnelling.
East of Paris, the highway A86, a 100-kilometer-long ring road around the French capital, is chronically congested. The plan was to build as a lasting relief a tunnel where, for the very first time, the car traffic runs on two levels on top of each other. This makes an inner diameter of 10.4 meters neccessary. The two tunnel sections run on a total lenght of almost ten kilometers through heterogenous ground with gradients of up to 4.5 percent and varying overburdens of sometimes only ten meters and up to 100 meters.
The solution of the Herrenknecht engineers for this highly complex project was to design a Mixshield with the capability of being converted inside the tunnel. Depending on the geology encountered, the Mixshield was re-tooled to slurry or EPB mode, and was also capable of being operated in open or semi-open mode. The first tunnel was successfully completed in October 2003. 26 months after starting boring the second tunnel in June 2005, the Mixshield broke through into the target shaft in August 2008.