Major Road Works in TriesteThe so-called second stretch of the third lot on Trieste's road network, northeast Italy is a new 5.5 km road alignment that connects the section of Trieste's major roadway already built by the City of Trieste in Cattinara municipality with the highway constructed by ANAS in Padriciano. The contract has been awarded in 2002 to the Collini-Rabbiosi-Cossi Costruzioni JV. The contract has a duration of 1,570 days, so that the entire section should be finished within the first months of 2007. The design was carried out by a JV comprising of Autovie Servizi SpA (Trieste), Geoconsult (Austria), IN.CO. SpA (Milan) and SO.TR.ECO. Srl (Genoa). The construction management is ensured by the city's technical department with the contribution of specialised external consultancies. The project is financed on the state budget and regional funds. The main works included in the new artery are the Carso tunnel, the Cattinara tunnel, the Cattinara viaduct (330 m) and the Castelliere and Padriciano interchanges. The Carso tunnel consists of two tubes. The north tube is 2,848.74 m long, of which 175 m in cut-and-cover at the north portal, 2,648.35 metres bored and 25.39 m of cut-and-cover at the south portal. The south tunnel is 2,819.40 m long, of which 135 m in cut-and-cover at the north portal, 2,661.78 m bored and 22.62 m in cut-and-cover at the south portal. The distance between both tubes is about 28 m. The Cattinara twin bored tunnel is 293.95 m long. It includes 45.26 m of cut-and-cover tunnel at the east portal, 216.99 m mined and 31.70 m of cut-and-cover tunnel at the west portal. Due to the closeness of the two bores, it is planned to use a special technique to create a central reinforced concrete wall built prior to the excavation of the two bores, which will be excavated at a distance of 12.2 m from one another. Both tunnels are about 12.2 m distant. The comprehensive excavation area (east and west tunnels plus central wall) is 192 sq m. Both tunnels carry two lanes each as well as a shoulder for emergency stops. The Carso tunnel has an excavation section of 130 sq m and the Cattinara tunnel a 130-140 sq m section. Eight crosscuts (excavated section of 68 sq m) will connect the Carso tunnels.The geological context of the Carso tunnel is generally characterised by a sequence to Tertiary limestone and partly by marly limestone. The zone is also characterised, with a certain frequency, by karstic voids and dolines together with really and truly deep karstic cavities. These karstic voids may be filled with rock blocks within a sandy, silty and clayey matrix, without water. Some fault zones, with intensely fractured limestone, are also expected along the tunnel alignment. The layer thickness of the superficial alterations is usually limited to few metres from the surface. The presence of karstic voids determines the high permeability of the rock mass. Therefore, the water table lies at a greater depth than the tunnel alignment.The geology of the Cattinara tunnel is generally characterised by the presence of a flysch formation composed of alternated marls and sandstone. The rock mass strength depends either on the distribution of the marls and sandstone or the general degree of alteration of the rock mass. In general, the depth of the surface layer altered by rock boulders of poor quality is limited to some metres from the surface. Anyway, it is expected to encounter along the route at least a fault zone oriented NW-SE, with a thickness of some metres, which determines areas with the presence of very fractured marls and clayey soil. Even though the Cattinara tunnel generally traverses weakly permeable grounds, water ingress is expected along the route. The comprehensive water quantities will reach some litres per minute. There are two drives on each tube of the Carso tunnel while there is only one at each tube of the Cattinara tunnel. The Carso tunnel is drilled and blasted and supported using NATM with employment of explosives except in the start zones, which have been tunnelled using hydraulic hammers, due to the presence of several interferences. The machinery employed is two Atlas Copco WL3 C drill rigs and four excavators equipped with hammers. The Cattinara tunnel is built using the NATM to bore a pilot tunnel with a TMI 815 hammer prior to enlargement to the final section with a roadheader and a CAT 330 excavator. Visit www.boomer-rig.com and www.cat.comThe support consists of steel ribs, Swellex bolts and fibre-reinforced shotcrete sprayed with three CIFA spritz-system CSS2 pumps. The rock is hauled by trucks. Visit www.swellex.com and www.cifa.comThe final lining will be simple concrete in the Carso tunnel (except the cut-and-cover pieces which will be covered with reinforced concrete) while the lining and invert in the Cattinara tunnel will be in reinforced concrete.Tunnelling is under way in the Carso tunnel, both in the Trieste-bound and Venice-bound tubes. As of 21st September, progress had reached 1,732 m from the south entrance and 27 m from the north entrance in the Trieste-bound tunnel and 1,832 m on the south drive and 45 m on the north drive in the tunnel to Venice. The final portion of the cut-and-cover tunnels to Padriciano is under way. The retaining walls are almost completed and the production of the reinforced and precompressed prefab concrete slabs is proceeding. On the roadway to Venice, jet-grouting ground consolidation is in course.To date, the Venice-bound pilot tunnel of the Cattinara tunnel is completed and concrete grout is injected to reinforce the ground that will be excavated. The enlargement to the final section of the Trieste-bound pilot bore has commenced. Progress has reached 51 m. Click it/69. Visit www.grandeviabilitatrieste.it 44/05. Click to enlarge