Groundforce has supplied complex propping solutions to work package T02 -the extension of line 14 of the Paris metro.
The northern extension of line 14 of the Paris metro for the RATP/STIF (the Paris and Greater Paris transport operators), which is being project managed by SYSTRA. (global leader in mass transit and rail engineering), is being extended to reduce traffic on line 13 of the Paris metro, which has already reached its maximum operating capacity. The next phase of the project will consist of connecting line 14 to line 15 at a newly created Saint-Denis Pleyel station, as part of the Greater Paris project.
Work package T02, which covers part of this northern extension, was awarded to a consortium of companies including Bouygues TP / Soletanche Bachy France / CSM Bessac / Soletanche Bachy Tunnels, and is due to be completed in five years.
The project consists of building the Mairie de Saint-Ouen station, creating new connections with the existing station on line 13. Two shafts, Pleyel and Pierre, which also provide exits for the tunnel boring machine, strengthening of the RER line C tunnel for the passage of the tunnel boring machine, plus 2.2 km of tunnel, in 3 sections bored by an earth pressure tunnel boring machine, and the central Glarner shaft, where all three tunnel operations will start from.
Groundforce supplied 10, MP500 hydraulic props for work on this structure located in the district Saint-Ouen. This shaft provides the starting point for all 3 tunnels with a total length of 2,219m and will be in the long term an access for the emergency services, and will house a pumping station, a ventilation shaft and a transformer/rectifier for the electrical supply..
Once the peripheral diaphragm walls were in place, this phase of the works on the so-called Glarner shaft consisted of open shaft as far as the underside of the base slab at a depth of 27 m and the construction of the 2m thick base slab.
The props were installed in parallel with and following the groundwork operations.
The three levels of props were installed as follows:-
- Level 24.50 NGF (French National Levelling Network), installation of metal struts and braces
- Level 18.00 NGF, construction of reinforced concrete struts and braces
- Level 11.00 NGF (at a depth of 20 metres): installation of metal struts (with a partial hydraulic strut solution) that will be removed once the base slab has been completed.
Groundforce's hydraulic props were installed at the third level of bracing
Groundforce’s hydraulic props were specified for this project because they offer a number of advantages: they are quick to install and remove, are highly versatile, suited to a range of shapes and sizes of excavations, and offer a very high load capacity.
In view of the complexity of the trapezoid-shaped Glarner shaft, which is 50 m long and between 12 m and 25 m wide, and the high structural tonnage stresses, Groundforce's MP500 props offered a very good solution, as they can support loads of up to 5000 kN.
One of the advantages of Groundforce props is that they comprise different sized modules with standard lengths between 1 m and 12 m.
"This offers greater flexibility for assembly and dismantling onsite, because the workshop does not intervene and no special parts need to be made"
explains Franck Vacheron, Civil Engineering Manager for work package T02 of the extension of line 14 from Bouygues Travaux Publics.
"Another is that their dimensions are not fixed, meaning that they can be adjusted in 20 or 50 cm intervals in relation to the actual configuration of the diaphragm walls using the hydraulic system.”
Also, they are relatively easy to install. Weighing between 8 and 12 tonnes, they can be installed by a 100-tonne mobile crane and two to three site workers, and deployed rapidly.
"We saved installation time thanks to this technology. We were able to install three props per day, while only two per day can be installed with a traditional solution", adds the civil engineering manager.
Actually on this shaft only the Groundforce props were removed after 3 months. They were delivered by truck in mid-July from the UK and returned at the end of August after completion of the concrete base slab. The remaining levels of propping will remain in place until the completion of the shaft in approximately 18 months.
Already used by Bouygues Construction on the Batignolles project in Paris Groundforce can now add another project in Paris to its growing list in mainland Europe.