Bracons Tunnel Breaks Through in SpainThe construction of the second section of the Vic-Olot road axis C-37 in Catalonia is under way between Torelló, in the province of Barcelona, and Sant Esteve d'en Bas, in the province of Girona. This 19.2 km section, which represents an overall investment of EUR250 million, is scheduled to open at the end of this year. Out of the 19.2 kilometres, 10.6 km is located in the region of Osona, some 4.3 km is the Bracons tunnel and the remaining 4.3 kilometres run in La Garrotxa area. Since most of the section has gradients ranging from 5 to 6.5%, eight kilometres will feature an additional lane for the overtaking of heavy vehicles. The first section from Vic to Torelló is already constructed.The Bracons tunnel includes a 4,338 m bidirectional single bore and its parallel safety gallery. The 13.7 m-wide 5 m-high traffic tunnel carries two lanes in Torelló direction and one lane in the opposite direction to Sant Esteve d'en Bas. Each lane is 3.5 m wide and the two directions are separated by a 1 m-wide centre line. There is also a pavement of slightly more than one metre on each external roadway edge. The rest of the roadway between Torelló and Sant Esteve d'en Bas will accomodate two lanes and an additional lane at some spots.FCC and Agrupación Guinovart & Obras y Servicios Hispania celebrated the breakthrough of the tunnel on 7th December, 2007. The tunnel is a key element on the Vic-Olot road axis. Crews will now concentrate on the concreting works and the construction of the false ceiling, road surfacing and pavements, drainage, installation of the lighting and ventilation, and security and control systems. Ultimately, the road signs will be installed and the drilling and fit-out of the safety tunnel will be finalised. Visit www.fcc.es and see a video at www.3cat24.cat/video/137629/altres/Bracons-tunel-perforat History of the projectThe construction of the road between Vic and Olot began in 2003 on the section from Torelló to the south mouth of the tunnel, but the Catalan government's department of land planning and public works made changes and re-tendered the 4.1 km section between the north mouth and road C-63 after Catalonia's change of government in December 2003 from the long time ruling conservative nationalist party to a socialist/republican/green left-wing three-party coalition. Environmental groups and citizens fiercely criticized the decision to build the controversial tunnel through an area of outstanding natural beauty. The tunnel caused the first major crisis among the members of the coalition in early 2004. The section from the north mouth of the tunnel to Sant Esteve d'en Bas was segregated and the section from the north mouth of the Bracons tunnel to Sant Esteve d'en Bas is another contract awarded to Sacyr, Cavosa, Scrinser and CRC Obras y Servicios for EUR54.8 million. Work commenced at the north portal in December 2005 and in the remaining segregated section in March 2007. Apart from the Bracons tunnel, the sections are at different stages of advance. For example, the section between Torelló and the south mouth of the Bracons tunnel is rather well advanced. The structures, which include six tunnels nearing end and three viaducts, have already been built and eight kilometres of the new road has been asphalted. What still needs to be done is the drainage and road surfacing along with installing all the tunnel equipment and road signs.The six tunnels are La Cavorca (180 m), Els Corbs (106 m), Les Salines (160 m), La Sala (460 m, finished in January 2006), Sant Andreu de la Vola (145 m, concluded in March 2007) and La Rierola (55 m, completed in June 2007). With the exception of the La Cavorca and Els Corbs tunnels, both cut-and-cover constructions, they are all mined tunnels built adopting the NATM, either to the full section or in some areas in a top heading / bench sequence.The stretch from the north mouth of the Bracons tunnel to Sant Esteve d'en Bas is less advanced. It involves the construction of the La Carrera and La Famada cut-and-cover tunnels, respectively 122 m and 94 m long, the 1,470 m Els Maials mined tunnel under La Codina and three viaducts to mitigate the impact on the environment. To date, approx. 350 metres of this last tunnel has been executed. Aerial view of the north portal of the Bracons tunnel Geology and hydrogeologyThe section runs through the folded foreland of the eastern Pyrenees (Ebro river basin). The sedimentary materials that fill the basin are of Eocene age, precisely they correspond to soils dating back to the Lower Lutecian-Bartonian. The section starts in the Vic plain to reach subsequently the south edge of the Pyrenean mountain range, in its southernmost pattern, the Bellmunt anticline.This geological structure produced the Llancers and Currull mountains, crossed by the Bracons tunnel. Therefore, the tunnel path travels successively through older medium to upper formations, Mount Puigsacal, Bellmunt, Bracons, until crossing the lower formation of Banyoles, that shapes the anticline axis, next to the northeastern mouth of the tunnel.The regional watershed line follows the afore-mentioned mountain ranges so that the alignment south of the Bracons tunnel is situated in the hydrographic basin of the Ter river, crossing the Fornés river, one of its affluents. The northern half of the tunnel is in the hydrographic basin of the Fluvià. The end of the alignment runs through the tectonic trough of the Vall d'en Bas, partitioned by normal faults with a N-S orientation. Drill and blastThere have been two drives, but not simultaneous. Tunnelling works from the south mouth ended in end-July 2006. During this first phase of the tunnel construction, 2,995 metres of the total length was dug. The decision to end excavation at this point at that time was purely technical to reduce the distance that dump trucks had to run to haul the rock and sands outside. The works from the north mouth began in December 2005.The excavated cross-section is 120 square metres. On both drives, the drill and blast method of excavation according to NATM to the full cross-section of the tunnel was used. Crews achieved variable advances ranging from 1.5 to 4 metres. The underground drill rigs employed at the site included an Atlas Copco XL3 C, an Atlas Copco WL3 C and an Atlas Copco 282 for the emergency exits. The blast holes were drilled by tools supplied by Secoroc. The explosives were Goma 2-ECO of Maxam. Visit www.atlascopco.com, www.cmt.atlascopco.com/secoroc and www.maxam-corp.com To support the tunnel, the builders employed 3.6 m-long Swellex Mn 24 bolts (5 m at the lay-bys), shotcrete with a 35 MPa compressive strength and 700 J flexural strength (adding 35 kg of Trefilarbed FE 65/35 steel fibres), BASF's Delvocrete Activator S-52 accelerator, Meyco MS 685 silica admixture and Glenium T802 hyperplasticiser. For shotcreting, two Putzmeister WKM 103 robots and one Sika PM-500 were used. In addition, TH-29 steel arches were installed along with HEB-160 sometimes. Visit www.swellex.com, www.arcelormittal.com, www.basf.com, www.putzmeister.com and www.sika.com/stm.htmThe blasts were loaded by a CAT 966 to a fleet of six Volvos A-25 dump trucks (in each of the two drives). Rock se realizó con by a Volvo EC-250 excavator equipped with a hydraulic breaker. Visit www.cat.com and www.volvo.com/constructionequipmentDuring construction, the tunnel is ventilated, from the south drive, by a 200 kW Zitron ventilation fan ZVN1-18-200/4, featuring a 2,500 mm diameter, and at the north drive by two 90 kW Zitron fans ZVN1-14-90/4, 2,000 mm in diameter. Visit www.zitron.comThe concrete batching plant is a Teka THZ-1500 with a production of 50 cu m/h, provision of aggregates by means of a star-bin-design and dragline, 1 cu m mixer and water heating. Visit www.teka.deEscape galleryThe scheme also involves a parallel safety gallery, approx. 4,400 metres in length, currently under construction. This safety tunnel is being bored from the north end by Marti Ibérica using a 4.4 m-diameter Robbins TBM 1218-304 equipped with 30 17" disc cutters. The cutter head is capable of a thrust power of 750 kW. For rock handling, a 600 mm-wide Marti Technik conveyor belt has been installed. Visit www.marti-iberica.es, www.martitechnick.ch and www.therobbinscompany.comEvery 400 metres, 11 cross passages communicate with the main tunnel, three of which for emergency vehicles and eight for pedestrians. To date, 3,300 metres have been excavated. Breakthrough is expected for April 2008, depending of the geology that crews will encounter. The advancement achieved by the TBM so far is in line with the planning, which depends on the class of support that is implemented. And the supports that have been implemented so far are much heavier than what was originally thought, with more than two-thirds of the tunnel in class 3 and class 4. Nevertheless, the crews have optimised the TBM advancement in a rather fractured ground which required the massive use of steel arches and thick shotcreting.Crews use BASF's alcali-free accelerator Meyco SA-167. The TBM ventilation system consists of two 45 kW, 1,000 mm-diameter Korfmann fans. Visit www.korfmann.comWhen it opens to traffic, the tunnel will only be used by cars, vans and vehicles not exceeding a specific weight. Heavy trucks will not be allowed. The reason for this traffic limitation is because the Les Preses and Olot bypass roads have yet to be constructed. They will absorb the traffic from Bracons, which the existing roadways are not capable of doing. The Olot bypass road will be put out to tender at the end of this year and will take to years to construct. No date has been decided for the Les Preses bypass road. The Bracons tunnel will be the third longest in Catalonia when it opens, behind the Vielha tunnel (5,230 m) and Cadí tunnel (5,026 m). Click es/90. Read E-News Weekly 3/2004 & 46/2003. 05/08.