Zillastro Tunnel on Ionian Tyrrhenian Cross-Country Road Also Called Bagnara-BovalinoThe Zillastro tunnel is the major structure on the Ionian Tyrrhenian cross-country road, called Bagnara-Bovalino, about 39 km long, which is extending in the west-east direction, linking up the Tyrrhenian basin to the Ionian one. The Bagnara-Bovalino section connects the SS 106 Jonica road between Ardore and Marina di Gioiosa Jonica. The final project of this cross-country road envisages a subdivision into five lots: lot A (from Bagnara to Sitiziano), lot B (from Sitiziano to Santa Cristina d'Aspromonte), lot C (from Santa Cristina d'Aspromonte to Platì), lot D (from Plati to Natile Nuovo) and lot E (from Natile Nuovo to Bovalino). The Zillastro tunnel belongs to lot C and consists of a twin bored tunnel, with one bore per direction: the Madonna della Montagna tube, 5,980 m long, from the Tyrrhenian Sea to the Ionian Sea (between chainages 16+750 and 22+730) and the Crocefisso dello Zillastro tube, 6,0480.5 m long, in opposite direction (between chainages 16+741.50 and 22+790). Cut-and-cover extremities at the portals of the two tubes are 15 and 33 m long for the right tube, 20 and 83 m long for the left tube, respectively for Bagnara (west) and Bovalino (east) sides. The maximum gradient is 2.91% from +515 m asl (Santa Cristina di Aspromonte access) to +372 m asl (Plati access).The maximum cover above the tunnel is 679 m for the left bore and 680.7 m for the right one. On average, for a path of over 4 km, the cover is never below 260 m and immediately reaches considerable heights due to high inclines of the Ionian and Tyrrhenian slopes. The length of both tubes is such that they rank tenth and eleventh respectively among all bored tunnels currently achieved or planned in Italy.In accordance with the preliminary project, the choice for a twin-tube tunnel and therefore dualling the infrastructure roadway emerged from a series of considerations mainly related to the necessity of reaching a high security level in the tunnel, even if this implies an increase in final costs.Each tube has been designed for a roadway width including a 3.75 m lane (with an additional 0.5 m shoulder on the left) plus a 3 m emergency lane, in addition to clearances on each side for new jersey barriers, spaces for some equipment and their inspection and maintenance.This means obviously that, during exceptional events such as ordinary and/or extraordinary maintenance, incidents, etc., traffic can temporarily and exceptionally be redirected at low speed to a single tube by modifying the horizontal signs and opening the tunnel to bidirectional traffic, with one 3.25 m lane per direction and one 37.5 cm shoulder at each side. Even in such configuration, the security equipment in the tunnels have been dimensioned so that a sufficient ventilation and safety is guaranteed, even during periods of exceptional use. Both tubes are fitted with cross passages suited to motor vehicles and pedestrians every 300 m, instead of 900 m. Finally, specific attention has been paid to fire resistance of the structural condition of both tubes, fitting the vault and walls not protected by new jersey barriers with a specific protection treatment.This is a protective coating installed in the bored and/or false tunnels, obtained by spraying evenly on reinforced concrete supporting structures a relevant plaster coat, resistent to high temperatures in accordance with RWS specification. The plaster coat layer is afterwards reinforced to guarantee stability and perfect condition all over the years, by incorporating a relevant 50 x 50 mm hot zinc plated wire mesh. The minimum plaster coat material width is planned to be of about 38.5 mm, depending on the project's insulation grade (fire fighting legislation REI 120) and therefore depending on the minimum temperature to be met for concrete reinforced structural supports (to be incorporated in reinforced concrete at least at a 25 mm thickness as per RWS specification), and also on the type and typology of the structural cement to be protected. Thickness assessments have been made so as to guarantee, after 120 minutes and as per the RWS curve, a "concrete/protective plaster coat" interface temperature of less than 335°C (less than the max. RWS value of 380°C) and a max. 210°C temperature for concrete reinforcements incorporated at a 25 mm thickness from the "concrete/protective plaster coat" interface (therefore lower, even in this case, than the max. 250°C RWS value). Close to the Zillastro tunnel, at the Tyrrhenian and Ionian entrances, two safety and emergency centres will be built to guarantee a high level of preventive safety, but also, in emergency events, repressive safety.The excavation area for each tube is 93.75 sq m. For more details (in Italian) on the typical section, click here.As to geology, lithologic units along the territory crossed by the alignment are represented by metamorphic rock formations of both sea and continental origin. The metamorphic rocks consist of biotitic schists with amphibolites, locally with biotitic gneiss strips, and quartzitic biotitic garnetiferous gneiss. The metamorphic complex makes up the whole Zillastro massif and represents the unit of main geologic, technical significance, as it emerges in the major and longest section of territory of the tunnel alignment.The final project has been achieved and handed over by STI, a partnership of Procopio, Fedele, Polifroni, Corona, Stone, Musinet, Sina, Italtec, Bosco and Colaci. Visit www.progineer.itGeostructural measurements have helped identify a typical excavation cross section according to the strength and deformability features of the rock mass and to the lithostatic loads in the cover above the tunnel. The rock mass behaviour resulting from the tunnel excavation has been classified in Type A (stable face), Type B (stable face at short term) and Type C (unstable face). Depending on the geometric features of the tunnel and the geotechnical conditions of the formation to be driven, the method will consist of full-section excavation, crown and face pre-reinforcement using a two-boom rig (Odex system), advance in pre-reinforced formations using a rotary head or hydraulic hammer, advance in rock formation using explosives, and travelling tunnel formwork units for final lining. There will be four drives. For further details on support and cladding techniques or mucking-out, click here. Piacente Costruzioni started work on the first section of lot E. The total cost of the Zillastro tunnel, the most expensive structure on the cross-country road, is estimated at about EUR263 million, wherefo EUR214 million for the bored and cut-and-cover tunnel, portals and road superstructure; EUR26 million for lighting, ventilation, radio, luminous signs and electric cabins; and EUR23 million for SOS equipment, fire fighting, water mist, cross passages, etc. Opening to traffic of the entire infrastructure is expected by 2014-2015. Visit www.provincia.reggio-calabria.it/binary/provincia_rc/s_apq/presentazione12052005.1116946063.pdf 39/06.