References

Bourg - Bellegarde line - Contract 1

FRANCE, 2008

Upgrade of tunnels, creation of an underpass, construction of a bridge and other civil engineering works to modernize a railway.

As part of the modernization of the Bourg en Bresse / Bellegarde railway line, Soletanche Bachy was awarded contract no.1 works.




This involved a 25 km section, with three major elements of work :

Racouze tunnel
The existing tunnel was 1,700m long and about 4.7m wide and needed to be modernized for the TGV high-speed train line. Work was scheduled as follows:

Phase 1 – Tunnel arch and piers:
- Construction of emergency recesses (refuges) for employees every 50m, by saw cutting at regular intervals and demolition by layer removal using a Brokk machine. Expanding mortar was required for the residual angles.
- The arch was sealed using strip drains and watertight sealers.
- Bringing the arch up to TGV standard by cutting: saw-cutting every 7 cm, demolition of layers of 10 to 50 cm using a hydraulic rock breaker.
- Construction of recesses in the arch to accommodate the catenary suspension system by saw cutting, demolition using a hydraulic rock breaker and then shotcreting.
- Nails fitted every 2m to anchor the piers before the track was lowered.

Phase 2 - Lowering the track:
- Ballast removal
- Lowering the track in the limestone, using a planing machine
- Installation of precast reinforced concrete channels (acting as struts)
- A reinforced concrete slab was laid in the clay areas to withstand the uplift caused by swelling clay.

Rail underpass
An underpass (460lm, 3 to 11m deep and 6 to 7m wide) was built under the RD1075 to enable the removal of the PN5 level crossing (work carried out in phases so as not to disrupt traffic flow). A temporary retaining wall solution using sheet piles and reinforced-concrete U-shaped units was chosen. The 1000m of sheet piles were installed using high frequency variable vibro-drivers.

Reyssouze bridge
The old stone bridge was not suitable for TGV traffic and was demolished and then rebuilt as a cased composite beam bridge founded on 28 Starsol piles.

Contract no.1 also comprised a number of other items, including the renovation of the Sénissiat tunnel, soil- nailed walls, frame bridges, watertightness, acoustic screens, excavations, etc.

A538.pdf


Techniques

Civil engineering

Regardless of site size, and providing it involves a significant proportion of works in the ground, Soletanche Bachy will handle the complete project, and all aspects of the works, including site supervision, excavations, foundations, civil engineering and all construction operations.

Piles and micropiles

A pile is a structural element driven into the soil for transferring loads and prevent deformation. Its slenderness ratio is not limited.
Pile shafts can be uniform and rectilinear, telescopic and belled out.
Piles can be installed either separately or in groups. They can also form a retaining wall, a mixed curtain wall, contiguous piles, secant piles and composite curtain walls, such as Berlin walls and similar. Piles are also used as precast beams to be placed in the structure of the building they support.

Retaining structures

A retaining shell is a slim shell structure used during vertical excavations. Unlike retaining walls, the weight of a retaining shell has little effect on its capacity to balance the pressures.

Tunnel boring

In the tunnelling field, Soletanche Bachy’s subsidiaries Soletanche Bachy Tunnels and CSM Bessac specialise in management of tunnel sites and also, for the latter, the design and construction of tunnel boring machines.

Ouvrages

Railway works

Soletanche Bachy has developed a number of techniques for use in railway works; cut and cover tunnels, highways, underground stations, viaduct etc.

Tunnels

In the tunnelling field, Soletanche Bachy’s subsidiaries Soletanche Bachy Tunnels and CSM Bessac specialise in management of tunnel sites and also, for the latter, the design and construction of tunnel boring machines.


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