Vedeggio-Cassarate Tunnel under Construction in Lugano, SwitzerlandThe Vedeggio-Cassarate tunnel in Lugano, Switzerland is the first piece within Lugano’s transport plan. This big scheme is a list of complex projects being an absolute priority for the regeneration of infrastructure in the Lugano area. It has been studied to ensure the attractiveness, also from the economic point of view, of what is a strategic region for the Ticino canton. Studies for the Vedeggio-Cassarate tunnel were launched in 1995 and the project was approved by the land expropriation court in 2004. The overall cost amounts to CHF355 million and includes land acquisition. The Swiss confederation contributes CHF205 million to the project.TheVedeggio-Cassarate tunnel project comprises of three elements: the redevelopment of North Lugano interchange in Vedeggio to connect to highway A2; the tunnel itself, from portal to portal; and works in Cassarate, to connect to the local road system, an interchange car park and public transport means. The objective of the tunnel, together with all the other structures within Lugano’s transport plan, is to develop the Vedeggio and Cassarate plains. The project is oriented towards two directions: redefining the traffic flows, in view of the substantial traffic increase predicted in the next years, and reorganizing the urban planning.The tunnel is 2,630 metres long. It is a single-tube bidirectional tunnel, with a safety tunnel to its southside. The typical cross-section is characterised by twin 3.75 m-wide lanes and two shoulders, at least 1.20 m wide. The bored cross-section is approx. 85 square metres for the main tunnel and 16 square metres for the safety bore. The main tunnel will generate a volume of rock and soil of 265,000 cubic metres whereas the safety tunnel will produce 45,000 square metres. The spoil will totally be stored and reused at the portal area. TheVedeggio portal is situated at the North Lugano interchange and the Cassarate portal under Trevano Hill, nearby the Carrefour supermarket. Safety tunnelThe safety tunnel features a bored diameter of 4.40 metres, a headroom of 2.80 metres and a width of 2.50 metres. This enables rescue vehicles like ambulances to travel through. The longitudinal profile features maximum and minimum gradients of around 1.6% and 1.1%. The route and longitudinal profile take into account the future construction of the Monte Ceneri base tunnel, in particular the Vezia connection and the central corridors planned by AlpTransit to extend the routes to south. Traffic volume is forecast at around 25,000 cars/day. The safety tunnel spans 2,630 metres, 2,370 metres of which has been bored in rock using a 4 m-diameter Herrenknecht TBM, and 260 metres in soft terrain. Visit www.herrenknecht.comThe CHF17.3 million contract to construct the safety tunnel in rock has been awarded in July 2005 to Muttoni (leader) and Hochtief Construction. Preliminary work to prepare and install the construction sites commenced on 5th September, 2005. For technical reasons, the first 60 metres were drilled and blasted. This begun on 16th November, 2005 in Vezia and was completed in end January 2006. At the beginning of 2006, a Herrenknecht TBM was assembled. It entered into action on 6th March, 2006. TBM excavation ended on 27th July, 2006. In total, approx. 40,000 cubic metres of rock has been extracted, which will be completely stored and reused at the portal area. Visit www.muttoni-sa.ch and www.hochtief-construction.comThe safety tunnel in rock, excavated from the Vedeggio portal nearby the North Lugano highway interchange, was the first newly achieved major underground structure. Its goal is to meet all the requirements in terms of users’ safety when the main tunnel opens. Digging of the safety tunnel also represented a valuable source of information on the rock mass geology and hydrology, prior to excavating the main tunnel. Main tunnelConstruction of the main tunnel commenced on 16th November, 2006. This involves an investment of some CHF110 million. Excavation - 2,370 metres of which in rock and 260 metres in loose ground -actually began in January 2007 and will carry on until around mid 2009. Full completion of the project is expected in end 2010.The contract for the rock section has been awarded to a Marti consortium, whose partners are Mancini & Marti and Marti Tunnelbau. The Jetting Lugano consortium including Pizzarotti, Cossi, Rodio and Bauer bagged the contract for the soft soil segment. Both contracts amount to slightly less than CHF110 million. Visit www.martiag.ch/tunnel, www.martiag.ch/mancini, www.pizzarotti.ch, www.cossi.com, www.rodio.ch and www.bauer-schweiz.chThe safety equipment will consist of two electric control installations at the portals, an intermediate ventilation station, cross-passages and escape exits to the safety bore every 300 metres (four of which are pedestrian and four vehicular), five lay-bys, 21 SOS niches, 18 hydrants and a semi-transversal ventilation system with top section sealed with a concrete ceiling slab to form a ventilation duct that evacuates the fumes in case of fire through computer-controlled vents.Section in rockExcavation is performed from the Vezia portal, the geology is rather good and consists of Stabiello gneiss, seritic, quartzitic schists and amphibolitic lenses. Little water is present throughout excavation. For excavation of the main tunnel, sequential drilling and blasting will be used in the first 600 metres prior to shifting to full-face excavation in the subsequent 1,750 metres. The machinery includes an Atlas Copco three-boom Rocket Boomer 353ES, a CAT 966H wheel loader, five CWS-Belloli dumpers and a CAT 325 EN excavator for rock scaling. Liquid explosives are supplied by Explotec and the detonators by Nonel. Visit www.atlascopco.com, www.cat.com, www.explotec.ch and www.dynonobel.comA peculiar difficulty within the project is the crossing of the Gotthard railway operated by the Swiss railway company SBB/CFF/FFS, with only seven metres of cover and the crossing of Vezia village with just 15-35 metres of cover. To optimize the blasts, an hydrid priming system is employed, based on Nonel MS + LP + SL detonators. The blasts are controlled by a vibration measurement system implemented by Muttoni & Beffa. Visit www.mebsa.chAdvance of the main tunnel in rock has reached 260 metres at the top heading and 220 metres at the benches. The rock is secured thanks to bolting (16,000 Bellex bolts provided by Belloli), Bekaert fibre-reinforced shotcrete sprayed by a Meyco Potenza shotcreting robot and steel arches if needed. Visit www.bekaert.com, www.belloli-italia.com and www.meyco.basf.com/Meyco/ENThe concrete is produced directly at the construction site by an Amman Baumix concrete plant and trucked to the tunnel by an Euro 5 Mercedes Actros concrete mixer equipped with particle filter. Special attention is being paid to the environmental issues and the air quality underground. All the machinery is equipped with particle filters. View pictures here. Visit www.ammann-group.ch and www.mercedes-benz.chTunnelling is scheduled to be completed in end 2009 and final concrete lining is planned to start in early 2009 for end expected in 2010. Opening of the tunnel is planned in 2011. The inner concrete lining will be 30 cm thick. The headroom is 4.50 m plus 70 centimetres for the road signs. A waterproofing lining will be installed between the primary concrete layer and the final lining.Ducts will be inserted at the base of the lining to drain clean groundwater ingress from the rock mass and a culvert will evacuate dirty waters from the carriageway, for example waters to clean the tunnel or extinguish a fire. Tunnelling in soft groundFor part of the 260 m-long soft ground section at the eastern portal of the tunnel, a 70 m-long and 28 m-wide excavation pit had to be constructed from which the tunnel could be advanced by conventional mining techniques. Bauer Spezialtiefbau Schweiz has used Bauer BG 40 and BG 28 rotary drilling rigs to construct secant bored pile retaining walls for an excavation pit near the tunnel. A total of 362 piles of 1,000 mm diameter were drilled to depths of up to 31 metres. The walls were anchored back with up to four levels of anchors. The work was carried out in the period January to May 2007.During the construction works, considerable difficulties were caused by two artesian groundwater horizons resulting in significant artesian pressures. In addition, boulders up to 4 m in diameter had to be drilled through at depths between 20 and 28 metres. Visit www.lombardi.ch/publications/pdfviewer.php?ID=328 27-28/07.