References

The western part is the missing link of the A86 motorway around Paris (80 km). Expected for tens of years, the completion of the A86 is one the largest underground road project built in Europe recently.
With a length of 10 km, the East tunnel linking Rueil-Malmaison to Versailles crosses the entire geological series of the Paris basin, from the Montian chalk to the Fontainebleau sands. The soil conditions are highly variable (fine sands, marl, plastic clay, rocky limestone) and required the use of a TBM able to work either with slurry shield or earth pressure.

Authorized only to light vehicles with a maximum height of 2 meters, the tunnel has a ceiling height of 2.55 meters only along the traffic lanes.

The safety niches, every 200m (transfer stairs or smoke extraction shelter) have led to choose multiple excavation techniques suited to the soil conditions (soil treatment, freezing, shaft excavated from the surface).

Complex calculation models for an ambitious project
The importance and complexity of the niches structures required the construction of several finite element calculation models. These models include the construction phases of the tunnel and niche.

Terrasol’s achievements:

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• Expertise of the niches feasibility file (analysis of the different construction solutions)
• 3D FEM calculations for two niches
• External checking of all detailed studies for the niches (support and lining design reports, drawings)