Madrid's Second Railway Connection to Open in June 2006The new railway connection for suburban lines C-3 and C-4 between Atocha and Chamartin railway stations in Madrid is mainly a 7,425 m tunnel, the second underground link between the two stations. Section Atocha-Nuevos Ministerios (4,870 m) includes the Sol-Gran Via and Alonso Martinez stations. Section Nuevos Ministerios-Chamartin spans 3,384 m and includes the Nuevos Ministerios station. The tunnel will carry two tracks.Section Atocha-Nuevos Ministerios is under build by a JV between ACS Dragados and Tecsa for EUR77 million, by means of a NFM Technologies EPB shield previously used on the Madrid metro. The machine was launched on 2nd July. Visit www.nfm-technologies.com. Section Nuevos Ministerios-Chamartin has been awarded to Ferrovial-Agroman.The outer diameter is 9.38 m and the inner diameter 8.43 m for a final section of 44 sq m. The geology is composed of sedimentary Miocene materials characterised by a high compactness, belonging to the Madrid formation, consisting of stratified series of sands and clay, the proportion between the two being variable. In the south zone, clay predominates with lenticular sand contents. As work progresses to the north, sand contents will gradually grow until they predominate, with intercalated lenticular clay. Hydrogeologically, the route is above the water table and under several suspended water levels spread out irregularly and discontinuously. Structurally, the soil has an horizontal layout.The three stations within the project will be 240 m in length, with variable width in each station i.e. 20.36 m (constant) at Sol-Gran Via and 18.35 m (minimum) and 36.36 m (ticket hall) at Nuevos Ministerios. The headroom varies in each station. The Sol-Gran Via cavern will be 13 m high and the mezzanine will be at 5 m while at Nuevos Ministerios, the station will be 8.5 m high between the tracks and the first deck (various decks). The Alonso Martinez station project is under design.Section Atocha-Nuevos Ministerios also includes 9 ventilation shafts, 8 emergency exits, 6 crossings with metro lines, 3 ground treatment shafts. The Sol-Gran Via station requires 3 ventilation shafts, 1 emergency exit and 2 ground treatment shafts. Section Nuevos Ministerios-Chamartin includes 5 ventilation shafts, 4 emergency exits, 3 crossings with metro lines and 4 ground treatment shafts. The dimensions of the ventilation and emergency structures is approximately 42 + 42 sq m (generally in the same place). The emergency exits connect to the main tunnel.The dimensions are as follows: 6.1 m wide x 6.25 m high for the ventilation and emergency galleries, 2 m wide x 3 m high for the emergency galleries, 5.25 m wide x 5.63 m high for the transformer centre galleries and 2 m wide x 3.5 m high for the access galleries to the transformer centres. The concourse tunnels to the new and existing stations have variable dimensions. Two identical TBMs (inner and outer diameters, lining thickness, tunnelling systems, mucking-out, support, etc.) will drive the two sections using earth pressure balance and foam to support the face. The thrust totals 10,000 t. The cutter head of the NFM TBM excavating the Atocha-Nuevos Ministerios stretch is characterised by a 20,230 kN torque, a start-up torque of 24,000 kN and is equipped with 17 hydraulic engines with reduction gear. The diameter of the main bearing is 5.000 mm. The cutter heads has 21 disc cutters and the installed power is 4,100 kW.It is planned to build the Sol-Gran Via station using the German method (manual excavation) from three drives. All the galleries will be excavated manually. It has not been decided if part of the benches will be excavated with machinery and, if so, what type. Access is made through shafts and mucking-out is vertical. The excavation method of Alonso Martinez station is still under design. However, the predictable method would be a combination of the German method and diaphragm walls. At Nuevos Ministerios and Chamartin, the cut-and-cover method will be used using wheel excavators and trucks entering and leaving the site by a ramp. The tunnel is lined with 32 cm-thick precast concrete segments. Local connections to the main tunnel and galleries are executed using the Belgian method (also known as Madrid traditional method). The support consists of timber (boards and struts), TH16.5 steel arches and concrete lining. At Sol-Gran Via, during the multiple phases of construction, the galleries and arches will be reinforced with timber (boards and struts), TH58-21 and TH58-36 steel arches with subsequent backfill of concrete. For Alonso Martinez station, the support and lining techniques are still under study. At Nuevos Ministerios, construction will proceed building diaphragm walls, installing beams and a top deck prior to excavation while also installing struts and intermediate decks.The spoil will be removed using a conveyor belt in the TBM, muck cars in the tunnel and trucks will transport it to dump sites. For the shafts, the debris will be evacuated by cranes or bridge cranes and containers in the shafts, and then transferred by trucks to the dump areas. At Sol-Gran Via station, the mucking-out is done by conveyor belts and containers, locally by excavators and loaders onto trucks. At Nuevos Ministerios, mucking-out is done by loaders and excavators loading onto trucks accessing to the site by a ramp.The tunnel will open to traffic before completion of all the stations. It will decongest Atocha station allowing commuters from Parla, Aranjuez and Fuenlabrada-Mostoles to travel to La Castellana without shifting trains. 250,000 commuters transit through Atocha every day. Click es/68. Visit www.rafcercamadrid.com 45/04. NFM Technologies' TBM at the start box in Atocha.