Pianoro Tunnel Breakthrough on Bologna-Florence High Speed LineOn 15th June, 2005 at kilometre point 7+372 and a distance of 2,266 m from the north entrance, the Pianoro tunnel broke through. The 10,710 m tunnel is the Emilian entrance to the new high speed link across the Apennines between Bologna and Florence, awarded by RFI-TAV to the consortium CAVET (Consorzio Alta Velocita Emilia-Toscana) with FIAT as general contractor. The line will reduce journey times and increase the volume of passengers and goods transported on track on the north-south main line. The other members of CAVET are CRPL (Consorzio Ravennate di Produzione e Lavoro), Maire Engineering, Impregilo and CMC. CAVET subcontracted the construction of the Pianoro tunnel to the SECO-DGC-CO.E.STRA JV for EUR25 million. The tunnel is a twin-track infrastructure, featuring a cross section of 150 sq m. Visit www.impregilo.itThe tunnel project, like all the underground structures built for the high speed and high capacity rail link between Bologna and Florence, has been based on the Analysis of DEformations COntrolled in Rocks and Soils (A.DE.CO.RS) commissioned to Milan-based Rocksoil S.p.A. Visit www.rocksoil.com. In close connection with the Pianoro tunnel is the construction, either completed or under way, of other major and challenging underground works required for the high speed and high capacity line between Bologna and Florence. Not only the Pianoro tunnel has been dug from the north and south but also from four other drives opened from two intermediate access adits. These adits, which feature a 80 sq m section and respective lengths of 207 m and 297 m, will be entirely lined and subsequently used as service accesses and escape exits in case of emergency during the operation of the railway. In addition, there are two connecting tunnels, which alignments roughly run parallel to the right and left sides of the main tunnel. These are single-track tunnels, approximately 90 sq m in section, with respective lengths once completed of 4,505 m (uneven interconnection track) and 4,585 m (even interconnection track). The ongoing excavation of each of these connecting tunnels is proceeding from three drives.To ensure the proper ventilation at the tunnel faces from the intermediate adits, as the tunnel is excavated, it has been necessary to sink a 4.09 m-diameter 37.05 m-deep temporary ventilation shaft connected to the Pianoro tunnel and built by raise borer. Finally, for the junction between the connecting tunnels and the Pianoro tunnel, two chambers have been designed and are currently under construction. Their section is expanded compared with that of the main tunnel.The Pianoro tunnel has been excavated from six faces and tunnelling took place simultaneously for a significant amount of time (about 15 months). From the geological point of view, the Pianoro tunnel runs through formations belonging to the Epiligurian Emilian and Ligurian succession. From the north entrance, the route crosses successively Schlier facies marls, consisting of marls and Havana grey silty marls; the so-called chaotic complex, made up of flaky argillites with frequent calcareous and sandy blocks and breccia lenses in clayey matrix; the lower Appennine Pliocene, mixing silty marls and sandy silts in massive homogenous structure, locally stratified or laminated, at variable cementation degrees; the upper Appennine Pliocene, made up of silts with slightly cemented sands and slightly cemented sands alternating with sands, in stratified, but not always recognisable, structural order. The same tunnelling method has been employed at the six faces: pre-support of the face by means of insertion of structural grouted fibreglass bolts; excavation with an excavator equipped with a hydraulic hammer; muck haulage by means of a wheel loader or excavator with bucket and dumper truck; first phase lining, or support, with steel arches and welded mesh covered with shotcrete.Since the excavated material was generally of very poor quality, the pre-support of the face has been necessary most of the time. To do so, 40 x 6 mm structural three-angle fibreglass bolts have been used, characterised by a maximum traction resistance of about 70 x 10 cu kg. To install such elements, a Soilmec SM605 DT two-boom drill rig has been used to drill 102 mm-diameter 24 m-long holes. Once introduced in the holes, the fibreglass bolts have been filled with grout injected through the PVC pipes. Visit www.soilmec.itFor tunnelling, two FIAT-Hitachi FH450 track-mounted excavators have been used, one for tunnelling and the second in standby in case of breakdown of the first. Each excavator was equipped with a Rammit hydraulic hammer, model Rammer G100 City. A Paurat T3.20 rotary cutting head supplied by the Wirth Group has been used to cross a densely populated area with shallow cover. The usage of this rotary cutting head was necessary to comply with the requirement of reducing to the minimum nuisances to residents by limiting vibrations and noise. As it could not cover the full face, tunnelling took place in a top heading / bench sequence. Visit www.fiatkobelco.com, www.rammit.com and www.wirth-europe.de/roadheaders/paurat.htmFor muck haulage, four dump trucks were used on average among those available at the jobsite (eight Astra dumpers, models HD6, HD7 and RD25A), loaded by a FIAT-Hitachi FR220 wheel loader. The mucking-out was concurrent with the excavation only under particular conditions, because the relative vicinity of the final lining at the invert and benches made impossible to get the loader to stand sideways to the excavator. For the mucking-out of the invert, a FIAT-Hitachi EX255 ELT. 3 wheel excavator, equipped with bucket, was used. Visit www.astraspa.itThe pre-lining, or support, of the tunnel combines 2IPN180 steel arches placed each 1.4 m when the excavated material had good geomechanical characteristics, and HEB240 steel arches installed each 0.8 m in ground with poor geomechanical condition. 24 mm sheet plates installed between one steel arch and the next have been covered with wire mesh and a reinforced shotcrete layer. A Cavattoni CAV3A erector has been used to install the steel arches while a CIFA PAS 307 D/E6 concrete pump has been used for shotcreting. Visit www.cifa.comTunnelling at Pianoro commenced in July 1998. The employment of highly professional technical crews and the continuous support of the tunnel faces allowed to keep an average progress of about 1.5 m of finished tunnel per day, with peaks at 2 m. The excavated material represents 1,600,000 cu m. The job required 280,000 cu m of shotcrete, 23,560,000 kg of steel arches, 485,000 cu m of concrete and 3,650,000 kg of steel for concrete. The new Bologna-Florence high speed line spans 78.5 km, whereof 73.2 km (93.4%) runs in tunnels (these figures do not include the underground crossings in Bologna and Florence). The remaining 6.6% is bridges and viaducts (1,110 m) or at grade sections (4,056 m). In early June 2005, progress on the comprehensive line had reached about 80%, which represents a cost of EUR2,805 million. Tunnelling along the line is 98% complete, that is some 69 km of tunnel. The achievement is marked by considerable difficulties due to the crossing of geologically complex topographies and the characteristics of the Apennine territory. Approximately 1,830 people work at 22 worksites. The construction, awarded to CAVET, began in June 1996. From north to south, there are nine tunnels: Pianoro (10,841 m), Sadurano (3,855 m), Monte Bibele (9,243 m), Raticosa (10,450 m), where the line reaches its highest point at 413 m above sea level, Scheggianico (3,558 m), Firenzuola (15,285 m), which was holed through last December (subscribe to E-News Weekly 8/2005), Borgo Rinzelli (717 m), Morticine (654 m) and Vaglia (which, with 18.6 km, will be the longest tunnel entirely located on the Italian territory). Once the project is completed, trips by train from Rome to Milan will take less than 3 hours. In Bologna, the urban section of the new line in the city spans 17.8 km, whereof more than half will be underground. The project encompasses the construction of a new underground station in the area of the central station. Two connections are also planned with the Padova-Venice line and with the line to Verona. Tunnelling is under way to excavate the tunnel from San Ruffillo to the central station, the tunnel from the central station to the rolling stock depot, the Beverara and San Ruffillo electric substations, as well as the high speed underground station. In Florence, the urban section of the high speed line spans 9 km (whereof 7 km is underground) until Campo di Marte station. A new underground station will also be built in Belfiore. Click it/22. Visit www.tav.it 27/05.