Projects: Underground engineering
Road link between Catania and Siracusa
- 5 natural tunnels;
- 4 artificial tunnels;
- 20 major works;
- 40 minor works.
Completion of the motorway-like stretch
The project involved completing the motorway-like stretch of road between Catania and Siracusa between Passo Martino, on the city service artery, and km 130.4 on the SS 114 main national road.
In particular, the operations carried out regarded the geological and geotechnical assessment and geotechnical design along a 25 km section, and drawing up construction documents for 5 natural twin-bore motorway tunnels (about 11 km), 4 artificial tunnels, 20 major structures, a further 40 minor structures (manholes, watercourse crossings and underpasses with openings of up to 16 m), embankments (up to 10.5m in height) and entrenchments (up to 30 m in depth).
The section includes the following tunnels (from north to south): S. Demetrio (L=2800 m), Filippella (L=1000 m), Agnone I (L=200 m), Agnone II (L=150 m) and Serena (L=1050 m). The excavation work involved rocks both of sedimentary (Monte Carruba calcarenites, Pleistocene calcarenites and the respective base conglomerate) and volcanic (Pliocene volcanic rocks) origin. Lastly the heterogeneity of the rocks comprising the Carlentini formation (Upper Miocene) should be mentioned. For long sections of boring, this entailed passing through fronts of 'mixed lithotypes', characterized by contact between rocks with different geomechanical characteristics.
A full-section excavation method was constantly used (average cross-sectional area of 160 m2), mainly utilizing mechanical means. After every breakthrough, preliminary stage linings were applied (shotcrete and nails in the crown or shotcrete, steel ribs and nails in the side walls). The geomechanics of the rocks made excavation consolidation with GFRP-RC beams necessary along isolated stretches only. Excavation started at the north mouth of the S. Demetrio tunnel in Spring 2005. The two bores of the S. Demetrio tunnel were the only ones excavated by working on two opposite fronts; the other tunnels were almost entirely excavated by working in parallel along both bores in the same direction. The last wall of rock (north bore of the Filippella tunnel) came down on 24 May 2007.