Construction of Second Tunnel Ends on Line 1 of Seville MetroThe construction of the twin bored tunnel on Line 1 of the Seville metro, which runs from Parque de los Príncipes to San Bernardo, ended on 21st April, 2008 when a Lovat TBM holed through the wall of the reception pit at 11:15 o'clock, at a depth of 18.5 metres (level of the invert). Visit www.lovat.comThe second tunnel, 2,216 metres in length, took seven and a half months to complete. This is a third of the time required to complete the first parallel tunnel. Tunnelling commenced on 4th September, 2007 when the machine started digging in the launch pit in Parque de los Príncipes, at the intersection of Avenida de República Argentina and Virgen de África Street. The EPB TBM, 6.1 m in diameter, placed 1,583 segmental rings between the Parque de los Príncipes pit and the reception pit, situated at the convergence of Avenida de la Buhaira, Doctor Ordóñez de la Barrera Street and San Bernardo Street. Each segmental ring is 1.4 m long.From Parque de los Príncipes station, the TBM crossed subsequently República Argentina station, then it crossed the Alfonso XIII canal of the Guadalquivir River, then arrived in Puerta de Jerez station, Prado de San Sebastián station and finally San Bernardo station.During tunnelling of the second, twin tunnel, crews achieved an average advance of ten metres per day. This output has enabled them to conclude the construction of the second tunnel in seven and a half months (229 days). This timeline includes also the technical stops programmed periodically along the tunnel path, checks and replacement, when necessary, of the cutting tools that equip the cutter head (picks and cutter discs). A first factor that contributed to improve the performance of the machine is the adaptation of the TBM to the peculiarities of Seville's subsoil as well as the experience gained by the tunnelling crews. A second factor is the fact that excavation of the second tunnel did not require previous ground treatment or protection of buildings along the path. Ground treatment for the second, right tunnel had actually been performed prior to the second drive since they were done concurrently with ground treatment for the first, left tunnel.The third and last factor has been the purchase of a second cutter head for the TBM to build the second tunnel. The new cutting wheel, better adapted to Seville's subsoil, has proved more efficient.The Metro de Sevilla joint venture, formed by Dragados, Sacyr and GEA 21, will start the dismantling and extraction of the TBM from the reception pit on 26th April. It is a 700-tonne, 105 m-long machine (ten metres for the cutter head and tail shield and 95 metres for the trailing gear). The cutter head parts and the back-up will be transported by large and long slow moving vehicles to a joint venture's yard. This will take place at night to avoid traffic disruption. Click here and es/82. Visit www.metrodesevilla.net and www.sevilla21.com/metro 18/08.