Main Tunnels 

Within the framework of the Messina-Palermo motorway several tunnels, some highly complex, were envisaged in the design in order to overcome the difficult morphological and geological pattern of the area. Already in the first phase of the motorway construction, between 1967 and 1975, during which the sections Messina-Rocca di Caprileone (96.6 km.) and Buonfornello-Cefalu' (17.8 km.) were built, the design developed by TECHNITAL included a number of important double-barrel tunnels such as: the Telegrafo (1580 m), Tindari (2143 m), Capo Calavŕ (3178 m), Petrara (3372 m), Cipolla (1475 m), and Capo d’Orlando (2000 m) tunnels, which have all been realized.                

Since the resumption of the construction works in 1984 for the completion of the central section of the motorway, between Cefalů and Rocca di Caprileone (66 km) TECHNITAL has been responsible for the final design and works supervision of more tunnels of considerable importance which have required complex and sophisticated design and construction methodologies. Moreover, the design has included ventilation, lighting, safety and remote-controlled tolling systems.

The construction proceeded in both directions: today the Cefalů-Castelbuono section of 9 km (in the direction of Messina) is almost terminated, whilst the Rocca di Caprileone-Torrente Furiano section of about 16 km is already operating, and more lots have been contracted out.

In the area of Cefalů alone, the 13.4 km of dual-carriageway tunnels posed numerous problems.  The rugged nature of the terrain in the Cefalů-Castelbuono section necessitated the alternation of tunnels and viaducts. Of the 9,100 m completed so far, 6,680 m are tunnels. All together tunnels constitute 73% of the alignment.

The principal problems encountered, due to the particular geological-lithological nature of the region, have necessitated the adoption of complex and sophisticated construction methods.    

In the Cefalu-Castelbuono section the terrain is so rugged that the motorway required a succession of tunnels and viaducts. Tunnels constitute 73% of the entire alignment and total 13.4 km. The tunnels in this region, all double tube, are the following

• S. Elia (1,100 m)

• Carbonara (2,800 m)

• Langenia (1,000 m)

• S. Ambrogio (1,780 m). 

The S. Elia tunnel crosses Flysch di Reitano (alternations of sandstones and clayey marls), and the other three numidic flysch (shales and  quartz-arenites).                                                      

The general tunnel characteristics are the following:

• double tube, one for each direction;

• roadway, for each tunnel, consisting of two 3.75 m lanes with two sidewalks o.94 m wide;

• maximum height of the tunnel roof above the roadway: 7.3 m

• internal curve radium of the tunnel roof 5 m and 8.073 m for the reverse arch;

• net inside section 66 m˛;

• average excavation section 110 m˛;

• 1st phase support with double NP 180 or NP 200 arches joined with net and shotcrete, final thickness of 25-30 cm;

• reverse arch of 100 cm;

• final lining from 60 to 120 cm.

General geological context

The main geological formation in the area is known as numidic flysch, one of the sedimentary rocks also known as “turbidite formations”.

The turbidites are formed with the depositing in subsidence basins of turbid currents carrying from the submarine channels and valleys erosion material from the continental platform of an alpine chain in rapid orogeny.

From the lithological point of view the numidic flysch includes pelitic arenaceous sediments of the miocenic era. It is possible to distinguish a notably lithic facies

from a series of powerful quartz-arenite banks, and a predominately shaley facies consisting of thin shaley layers alternated with occasional thicker quartz-silty layers. Associations and alternations of the two main lithological types are present in various percentages.

The turbidite formations have lithological and physical-mechanical properties that depend directly not only on the size of the basin, the duration and the velocity of the sedimentation, but especially on the tectonic deformations to which they have been subjected following their sedimentation and on the partial diagenesis which has occurred in the meantime.

Thus besides the usual structures of a sedimentation of politic soils, such as slumping and undersea slips (olistostromes), there real breccias and chaotic masses.

For these reasons the tubidite formations are also defined “structurally complex formations”.

From the tectonic point of view the numidic flysch has formed through the slipping of nappes or tectonic scaglias by means of successive thrusts in a largely horizontal direction  which have dismantled the original rock structure.  Moreover, a recent subvertical nappe tectonics has occurred, affecting all the formations, and this has happened during the recent relieving phases following the orogenic phenomenon and is still going on with a slow and steady raising of the land.

At the western end of the alignment section, there is another formation called Flysch di Reitano which is very similar t o numidic flysch from th point of view of its lithological and physical-mechanical properties, but is a much less complex soil because of the inferior quantities of sub-horizontal bands of breccias and chaotic masses.

The problems encountered in the tunnels

The lithiological distribution in the tunnels in question is summarised as follows:

• S.Elia: Flysch di Reitano;

• Carbonara: 40% argilliti disgregate, 30% argilliti integre, 30% quarzoareniti;

• Langenia: 50% argilliti semiintegre e caoticizzate e 50% argilliti integre;

• S.Ambrogio: 30% argilliti integre, 30% argilliti disgregate e caotiche, 40% quarzoareniti (valori stimati).

The tunnel covering varies from a maximum of 200 m for the Carbonara and S.Ambrogio tunnels , to 60 m for the Langenia tunnel and 150 m for the S.Elia tunnel.

Such a broad distribution of shaley rocks with poor physical-mechanical properties posed considerable difficulties for tunnel construction. From the excavation phase through to the laying of the final lining. This was an important factor considering that, apart from the 5 m diameter railway tunnels built around 1900, these were the first large-scale tunnels excavated using modern tunnelling techniques. There was, therefore, no direct experience regarding the behaviour of these rocks during excavation, an experience which could be only partly compensated by geotechnical investigations in the design phase, not least because these investigations were circumscribed by the considerable cover and the inaccessibility of the locations.

In relating the problems encountered durino the tunnel construction, particular reference is made to the tunnels excavated in numidic flysch formations, since the flysch di Reitano formation, while similar, has a somewhat better behaviour pattern owing to its lower quantities of brecciated and chaotic facies. In fact, the problems with the S. Elia tunnel are related essentially to the relationships between the detritic layers and the substratum at the tunnel mouths.   

Read more about the Messina - Palermo Motorway : 
·        Background     ·        First Construction period     ·        Second Construction period     ·       Main Viaducts