THE FUTURE high-speed rail ‘Mediterranean Corridor’ will be a line that will run for a total length of 3,000km across several EU nations. The line is listed among the 10 top priority projects of the great Trans-European Network (TEN) for the period 2014- 2020. The corridor starts from Algeciras in Spain and runs to Budapest in Hungary. This line includes the Spanish Algeciras-Madrid-Tarragona and Seville-Valencia-Tarragona stretches, before crossing Barcelona, where there is also a railport- interconnection.
After this it runs through France from Perpignan, and through the Lyon-Turin route into Italy, where it should then join up with the Milan-Venice route and Trieste before connecting with Ljubljana in Slovenia and then Budapest.
THE LYON – TURIN TRACK
The first Italian stretch of the Mediterranean Corridor is the Turin-Lyon connection. The new line project will constitute a total 256km of railway (for both freight and passenger traffic) between France and Italy.
The job includes two new high-speed stations in Saint Jean de Maurienne (on the French side) and Susa (the Italian side), which will be linked through a twin tube base tunnel, running 57km underneath the Alps.
Once completed the tunnel will be one of the longest underground connections in the world. Considering the permanent increase of the exchanges in Europe and in particular through the Alpine arc, this new railway will allow the transfer of a large portion of freight and passengers onto the rail network, substantially reducing pollution in the Alpine environment.
Moreover in the future it will be easier to travel around the main EU cities.
A trip from Turin to Lyon will take around 100 minutes instead of more than four hours, and from Milan to Paris will take four hours instead of the current seven hours.
Management divisions
The future connection between Turin and Lyon will be managed by Réseau Ferrè de France (RFF) from Lyon up to Saint Jean de Maurienne, and by Rete Italiana Ferroviaria (RFI) from Susa/Bussoleno up to Turin. The cross-border section between Saint Jean de Maurienne and Susa/Bussoleno will be managed by Lyon Turin Ferroviaire (LTF) which is a private company owned in equal parts by RFI and RFF. LTF’s head office is in Chambery, France.
FEASIBILITY STUDY AND EXPLORATORY WORKS
LTF is responsible for building the Franco Italian section of the Lyon-Turin rail connection and is tasked with carrying out the pre-project studies and surveys in order to present the final details of the civil engineering work required, their location, cost and conditions for construction to the French and Italian governments.
To investigate the geological structure of the future base tunnel between Saint Jean de Maurienne and Susa, client LTF, during last 12 years, has commissioned four sets of site investigation along the line. Indeed on the French side, preliminary works for the construction of the base tunnel are now complete, with the excavation of three access tunnels in the Maurienne Valley:
- The 4,000m access gallery of Villarodin-Bourget/Modane, ended in November 2007
- The 2,480m of La Praz, ended in January 2009
- The 2,400m of Saint Martin La Porte, ended in July 2010.
All these access galleries allowed a better understanding of the geological structures, to better evaluate the technical difficulties and thus the construction methods and costs. In the Italian territory, the exploratory tunnel of La Maddalena is under progress. The data records will allow an assessment of the most suitable construction methodology, technical and safety aspects and cost valuation for the future base tunnel. During the construction phases, they will be used to gain entry to the various underground works.
When in service, the access tunnel will provide ventilation, access for maintenance teams and, if necessary, emergency crews.
La MaddaLena expLoratory tunnel
The works for the Italian exploratory tunnel started in April 2012 and will terminate in the spring of 2017. The job site is near Chiomonte, a small town in the Clarea river valley. The total length of the tunnel will be 5,765m plus 1,776m as an optional extra length, which will, if opted for, be approved by the client this year.
The first 198m were bored by the ‘traditional method’ (NATM) using of drillers, as at this stage the use of the explosives had been forbidden for security reasons (further details below).
Traditional tunnelling was stopped in August 2013 when a formation of mica schist was encountered.
The rest of the length will be bored by the use of an open mode TBM supplied by Robbins, called GEA, meaning ‘Earth’ in Italian.
Track and geology
The tunnel will cross through different geological scenario belong to Ambin formation, constituted by gneiss with presence of quartz and mica schist which represent more of 95 per cent of the total length.
The maximum cover will reach 2,000m near to the end of the tunnel. The maximum slope is 1.10 per cent uphill and 3.94 per cent downhill. The track presents two bends with a radius larger than 1,000m.
The final project was envisioned by LTF (with the help of preliminary investigation). During tunnel construction geotechnical investigation from the TBM will be carried out by JV Contractors leaded by CMC Ravenna (Italy).
No TAV Movement and TBM transport
NO TAV ("No to the High-Speed Train") is a movement based in the Susa Valley that opposes the construction of the new high-speed railway line between Turin and Lyon.
The entire area of the jobsite has been transformed into an area of ‘strategic interest for the country’, and is regularly patrolled by hundreds of policemen and soldiers. These measures began in June 2011.
Due to the opposition movement’s activities against the job, it was necessary to precisely organise and to manage all TBM and equipment transport from the supplier to the jobsite. Thanks to detailed planning relating to the real needs of the contractor’s schedule and delivery requirements, and the cooperation between security force, client and contractor, it was possible to manage the supply of the equipment into the jobsite without public nuisance, or inconvenience to work or schedule. The whole TBM, including back up, was transported by means of 10 exceptional and 90 ordinary transports, during the month of August 2013.
GEA
In order to match the geological investigation needs, and the time schedule required, an open mode TBM was chosen.
The Robbins Main Beam TBM, called GEA, allows quick access directly behind the cutterhead for the installation of rock support (rock bolts, steel mesh, ring beams, and shotcrete) by means of two specifically designed working areas, L1 and L2.
The first one, the L1, is located at 6m from the excavation face. The second one, L2, at work some 41m behind the face.
From L1 workers will carry out 36m-long probe drilling operations to investigate the rock before boring it. Taking into account the 7m of overlap between two consecutive probes, no section of tunnel will be excavated before thoroughly understanding its features.
All data will be recorded and filed to build an accurate geological picture.
SECTIONS
During the excavation, different support sections depending on the rock quality encountered will be installed.
The tunnel as designed takes 12 different section types into consideration, from F1 up to F5c. The first, F1 section, adopts Swellex bolts long 3m installed from the L1 working area.
This configuration will be applied across good rock with RMR > 81 and coverage between 100m and 600m. The gradual deterioration of the rock will require stronger support systems, realised as a greater number of bolts, steel mesh, and increased water drainage. If rock presents fault zones, high coverage, and an RMR lower than 40, the final classification; F5c will be the required application.
A proper consolidation around the excavation pro_ le should be carried out from L1, then from L2 TBM working area steel reinforcement panels and sprayed concrete will be installed.
SPOIL MANAGEMENT
During the first phase of NATM excavation, dumpers were employed to load and move excavated material. At the portal area, three ‘pools’ to house 5,000 cubic metres of material each were built.
When a pool is full (or when the rock encountered during the excavation changes geological characteristics) an authorised laboratory carries out analysis required under Italian Legal Decree 152/86. Depending on the results, the material will be stored in a proper area inside the jobsite by a different contractor.
If the soil extracted and analysed does not present the right features to be stored onsite, it will be classified and transported to an approved storage location.
The spoil mined by the TBM will run along the tunnel by the means of a belt conveyor system.
At the portal area a secondary belt conveyor will convey all materials in correspondence to the pools where it will be analysed.
ANCILLARY WORKS IN THE TUNNEL
Some ancillary works such as monitoring rooms and water tanks will be realised along the 7.5km of tunnel. The four monitoring rooms have been designed in order to allow monitoring system installation and data recording. The four water tanks are designed to manage the water in flow during excavation.
Along the whole tunnel it has been estimated that systems will need to manage 285 litres/sec.
Water will be divided and collected in four different types: cold potable, cold not potable, hot dirty and hot clean. At the tunnel’s lowest point (pk 4+090) two water tanks will be built able to manage approximately 300 litres/ sec. Two other tanks will be installed towards the tunnel exit (pk 2+805), which will store the water and will pump it outside.
At the portal area a water treatment plant will receive four different pipes (one for each kind of water collected) and after cleaning processes, will convey all water into the Clarea River.
SCHEDULE OF WORKS
Traditional excavation of 198 mt started in January 2013 and terminated in July 2013.
TBM assembly started in the middle of August 2013. At this stage the working schedule of La Maddalena jobsite is nine months in advance compared to contractual schedule. The average production prediction for the TBM is 12m per day, in order to finish the first 5,765m at the latest in 18 months and the entire (including optional extra length) drive of 7,541m in less than 24 months. TBM dismantling will then last four months.
In the final project visualisation, it is expected that La Maddalena could serve as a safety access tunnel for the main tunnel.
