Pilot Tunnel is More than 50% Completed at La Linea in ColombiaThe La Linea tunnel project, or Segundo Centenario tunnel, crosses the central mountain range and forms part of the Bogota-Buenaventura corridor, which is one of the priority road links for the development of the country and its competitiveness. It is part of the road that leads, from the centre of the country, to the southwest Pacific coast. The 8,571 m-long La Linea tunnel will be the longest road tunnel of Colombia and South America and one of the highest, at 2,422 metres above sea level. The Conlinea consortium, formed by Conconcreto and Carlos Solarte, is building for Invias, the national highway institute, the pilot bore. The final tunnel will be constructed in a second stage. The total length of the pilot tunnel is 8,542 metres. The site is situated between the departments of Tolima and Quindio, about 300 km southwest of Bogota. The pilot tunnel is built from two attacks at each end. A crew progresses in the La Linea tunnel from Cajamarca (Tolima) while another tunnelling team advances in the opposite direction from Calarca (Quindio). On 13th December, 2006 work advance in the La Linea pilot tunnel reached 50%. Crews had drilled 2,827 metres from Tolima and 1,458.4 metres from Quindio. The advance to date at each drive is 3,082 m in Tolima and 1,600 m in Quindio. The cross section is 19 sq m. The other subterranean works under way in the bowels of the mountain include 18 cross-connecting galleries to the future main tunnel, each one spanning 40 metres and with the same cross section as the pilot tunnel. It is predicted that the two attacks will meet in 12 months. The pilot tunnel will be useful to measure the geological risks. Visit www.invias.gov.co and www.conconcreto.comThe geology encountered in the excavated sections is as follows: type I (5.44%), type IIA (32.81%), type IIB (29.25%), type III (16.74%), type IV (10.84%) and type V (4.92%). The geology ahead of the faces could be similar to the conditions already found, except at La Soledad fault, an unknown area. It is expected to reach the fault in the next six to eight months.The project has created more than 500 direct jobs but there are less than a hundred miners working inside the tunnel. The tunnelling method used by the contractors consists of drilling jumbos and explosives. An Atlas Copco two-boom H252 drill rig is used at each face, backed up by another jumbo on standby. The supplier of the drill bits is Sandvik. Visit www.atlascopco.com y www.sandvik.comThe workers drill 66 blast holes, up to three metres of length, in which the explosives are subsequently charged. The type of explosive is blasting emulsions and in some cases hydrogel cartridges. The supplier is Indumil of Bogota. Between the moment when the explosives are charged and the firing, there are only six minutes. The workers have to step back to at least 300 metres. The wave shakes them and the explosion can be heard at some 3,050 metres away. Then the ventilation system is activated to extract the dense cloud of gas and dust. The ventilation system is composed of fans supplied by SMJ of the United States and ventilation ducts of ABC, Canada. Visit www.indumil.gov.co, www.smjfans.com and www.abccanada.caThe rock is supported preferably with resin bolts. In very bad ground, the miners employ fibre-glass bolts of Sireg on the face, TH-21 steel beams, steel fibre-reinforced shotcrete and Sika admixture. Visit www.sireg.it and www.sika.ch/en/stm.htm The incessant water ingress complicates the rock haulage, done by a muck train moving on tracks. At the Quindio drive for example, the water that gushes from the tunnel roof forms a sort of geyser with flows at 100 litres per second. There are four BEV and two Valente locomotives and two Häggloaders 8HR2 and 8HR2-B of GIA Industri. Visit www.valente.it and www.gia.se/eng/prod_hagg_rail.htmCrews are ahead of schedule and the tunnel will be built under budget, thanks to the good rock quality. The rock encountered so far allows to calculate that the whole project (the final tunnel) will have a cost of USD220 million, almost USD60 million cheaper than the initial budget. The ground is better than thought and no methane gas nor thermal water has been found, despite the proximity of the Machin volcano. No precious metal has been discovered either. The pilot tunnel, which in the future will serve as rescue tunnel in case of some emergency in the main tunnel, should be ready in a year. In the first week of January, associated works commenced at the Quindio portal access, which consist of three tunnels of 316, 488 and 596 metres, totalling a length of 1,400 metres, a viaduct and seven short bridges, as well as open air roads of 1.1 km, for a total of 2.8 kilometres. From Chile, two Tamrock Axera three-boom drill rigs were imported, for faster drilling. They will be used initially in the tunnels at the Quindio access. This machinery can drill blast holes of up to three metres. Two Atlas Copco drill rigs (one H110 and one H170) will also be used. 60% of freight transportation by road has to pass necessarily through La Linea Pass, a mountain culminating at 3,300 metres in the central mountain range. The benefits for hauliers will be greater if distances are shorter and speed higher. The financial gain would be approximately USD40 million (some COP89 billion). The Bogota-Buenaventura corridor project is divided into four sections: Bogota-Ibagué, Ibagué-Armenia-La Paila (where the La Linea tunnel is located), La Paila-Buga (under concession) and Buga-Buenaventura. The four-lane corridor will reduce the distance from 512 km to 503 km. The Calarcá-Cajamarca area, which includes the La Linea tunnel and its associated works, is 45 km long but will be shortened to 36 km when the tunnel is completed. Nowadays, the average velocity at La Linea is 18.2 km per hour. With the new tunnel, it is expected speed will jump to 60 km per hour while the accident rate will be reduced.The government of Colombia announced on 27th January, 2007 that an international prequalification process calling for proponents will be issued in June for construction and on-site supervision of the main tunnel and the dual carriageway between Cajamarca and Calarcá. These works will have an estimated cost of COP550 billion. The main tunnel will have the same length as the pilot tunnel, i.e. nearly 8.6 kilometres, and a height of 10 metres with two traffic lanes. The final tunnel will carry a 9 m-wide roadway. Its construction would begin in February 2008 to end in March 2010, after two years of work. Both tunnels will be cross connected at 17 locations, every 450 metres. Doors will hermetically close once road users are evacuated, to avoid the propagation of smoke, gases or flames. Also, the project includes two vertical ventilation pits, of 8 metres in diameter. Each one is divided by the middle to provide a gas extraction duct and a fresh air supply. Click co/15. View pictures here. Visit www.calarca.net/tuneldelalinea.html 07/07.