The FS, Italian railway society, has started a large series of interventions for the modernisation of the railway network in the Palermo area. The jobs include, in particular, the addition of a second track. The job site project covers over 30 Km of railway extension, 20 Km crossing the urban area, with the construction of 17 stations and 22 stops. Furthermore, in order to smooth Palermo chaotic traffic and secure direct connection to the airport, there is 7 km of track to be moved from the city surface to an underground tunnel.
Contractors jobsite spreads from the east outskirts of Palermo, Brancaccio zone, crossing the city to
the extreme west and completing the connection to the Falcone-Borsellino airport. In total
23,0000 m of secant piles have to be carried out across the site. It was necessary to perform the
job without any interruption to train schedules and at the same time limiting pollution and noise.
The jobsite conditions were solved by using the CAP/CSP pile application.
|Soilmec Piling Rigs|
The CAP/CSP method consists of pile augering with casing protection, it has been chosen as it
eliminates vibrations and disturbance to adjacent structures, reduces noise emissions and avoids
the use of bentonite mud for drilling. With the CAP/CSP method it is possible to execute piles in contact with existing foundations, avoiding decompression of the surrounding soil and ensuring the accurate and precise positioning of the pile. In addition, the use of protection casing secures vertical drilling, with less than 0.7% deviation.
|CAP / CSP Method|
In CAP/CSP method, piles are augered simultaneously with the driving of the protection casing into
the soil (when necessary augering may be carried on below the depth of the casing). Concreting is made through the auger shaft during auger extraction.Then, the reinforcement cage is driven into the fresh concrete, after which the temporary casing is removed. To construct secant pile diaphragms, the wall continuity is secured by secant primary and secondary piles overlapping. In this case, the guiding wall will secure the alignment of the diaphragm and guide the casing from the top. For the execution of CAP/CSP piles, Trevi chose the multifunctional Soilmec rigs: the R-825 and the SR-90 . Rigs have reached 25 m depth with a diameter of 920 mm. The primary and secondary piles were overlapping by 80mm. The different phases in the construction of tunnels and underground road passages have been designed in order to secure permanent railway and urban traffic.
For example, the WBS GA17 tunnel, where both original and new tracks have been installed, the
soils are mainly composed of soft and dense calcarenites up to 10 m depth approximately, followed
by clay and silts, the construction phases have been as follows:
• Construction of CSP piles side wall, without interruption of the railway existing track.
• Execution of intermediate wall with micro piles to reinforce the structure.
• Construction of the half coverage slab on the tunnel.
• Excavation of the first-half gallery (pict.2).
• Traffic diverted on the temporary track inside the half gallery or above the half coverage.
• Execution of second side wall with CSP piles.
• Completion of the tunnel coverage.
• Construction of the two definitive railway tracks inside the artificial gallery.
|Tunnel WBS GA17 during the development of the first half gallery|
Contractors has undertaken numerous underground passages as showed in the following pictures:
|Road Job Marking|
|Construction of the underground passage, during the job the traffic was diverted around the tunnel.|
|Passage complete: The traffic starts to flow. CSP piles at sight|
|Underground passage and round about with the piles CSP at sight|
In the light of the production figures, the choice of CAP/CSP method, executed with powerful
Soilmec rigs R-825 and SR-90 created excellent results. In fact, despite the necessity of frequent
moves in the city –in two years the rigs have traveled around 30 km!- a daily pile production of
65 m per rig has been reached.