New Section Andora-San Lorenzo al Mare on Genoa-Ventimiglia LineThe Andora-San Lorenzo al Mare section on the Genoa-Ventimiglia railroad in Liguria, Italy will be built in the hills and moved away from the seaside. The project has been awarded by Italferr to a JV between Spain's Ferrovial Agroman and Cossi Costruzioni. The EUR319.1 million project spans 18.8 km and includes 15.6 km of tunnels. The new line will be completed in 2009. The areas cleared of any track will become cycling lanes and walkways. Visit www.italferr.itThe project necessitates the construction of nine tunnels: Collecervo (3,115 m), San Simone (133 m), Caighei (2,618 m), Castello (485 m), Gorleri (3,093 m), Bardellini (2,920 m), Caramagnetta (197 m), Terra Bianca (466 m) and Poggi (2,080 m). All are single-tube tunnels for double track (crown radius of 525 cm). The Poggi and Terra Bianca tunnels are two different tunnels but in fact, when construction ends, a 60 m cut-and-cover tunnel will be built in the short portion separating them so that they will make a unique piece. Undergrounding the stretch in the valley between the two tunnels has been imposed to mitigate the impact on the environment and avoid a too close chain of portals and the propagation of noise in a valley highly valued for its landscape. Even the Collecervo and San Simone tunnels will be united into one unique tunnel at the end of tunnelling thanks to the construction of a cut-and-cover stretch, approximately 145 m in length, in the valley that today separates them.To complete the review of the underground works within the section, it must be mentioned that the project also includes two single-track tunnels near Imperia station. The project design of the station actually foresees that trains on the two priority tracks on Ventimiglia side travel through single-track tunnels before connecting, through two switches, with the Bardellini tunnel on the main line. This is how there will be two tunnels, one for the south track, approx. 250 m in length, named Porto Maurizio and another for the north track, of around 150 m, named Castelvecchio. At the connection point between the priority tracks and the main line, the connecting section enters two special boxes of around 60 metres, similarly designed, positioned diagonally 100 m apart to contain the transversal dimension of the section. With such solution, every box, which features a maximum width of around 20 m, accomodates three tracks. Alternatively, if the tracks had been designed side by side, it would have been necessary to plan a single box, with big dimensions, to house four side-by-side tracks.The tunnel excavation diameter is approx. 13 m considering that the finished diameter after lining must not be less than 10.5 m, with a lining thickness at the crown comprised between 90 and 100 cm and a pre-lining with steel arches and shotcrete of 25-30 cm. A unique crown and bench radius is required, at 525 cm. The excavated section corresponds to 125 sq m approx., whereof 100 sq m for the crown and benches and 25 sq m for the invert. The excavation diameter of the TBM-driven tunnels is 11.84 m, which is a finished inner diameter of 10.7 m, with 40 cm-thick precast segments. The inner diameter has been purposely oversized compared with the tunnels that will be dug by traditional means to get a tunnelling tolerance of around 10 cm in all directions. The single-track tunnels feature an excavated section of around 65 sq m, the maximum width being of approx. 6.5 sq m and height of around 8 m.No other underground works are planned. The tunnels are dual-track tunnels and therefore there are no cross passages or access adits or intermediate shafts. The only underground works are the tunnels and the two boxes connecting the priority tracks and the main line at Imperia station.The geological pattern is characterised, along all the section, by Sanremo flysh, arenaceous and marly flysh with spacing of the joints ranging from a few decimetres in the most weathered areas to 1-1.5 m in more consistent areas. The quality of the massif generally worsens from Andora to San Lorenzo al Mare so that the best conditions will be encountered in the Collecervo tunnel and the worst in the Terra Bianca tunnel. The only exception to this geological pattern is the Castello tunnel which crosses at straight angle a crest entirely formed by Pliocene clay intercalated with sands.From the tunnelling methodology point of view, the tunnels on the section can be divided into two categories: those to be bored with mechanised means by a Herrenknecht TBM (in the order, Collecervo + San Simone, Caighei, Gorleri and Bardellini) and those to be dug by traditional means (Castello, Caramagnetta, Poggi + Terra Bianca and the two single-track tunnels, Porto Maurizio and Castelvecchio). Mechanised tunnelling will be achieved by a 11.84 m-diameter open shield equipped with rock cutters and also prepared for possible foam injections on the tunnel face. This Herrenknecht TBM, which was previously used in Dublin to excavate the port tunnel (two road tunnels of 4 km in all), should commence excavating the first tunnel (Collecervo) during the current month of October. The other tunnels to be driven with traditional means will be excavated with a hydraulic hammer except the Castello tunnel which, because it crosses entirely a clayish massif, will be dug with a ripper mounted on an excavator to get a better profile of the tunnel contour. To date, none of these tunnels is under construction, except the portals. Visit www.herrenknecht.comFull-face excavation (top heading and benches) will be employed for the tunnels to be built with conventional means, followed at some distance from the face by the excavation and concreting of the invert. The face will be supported applying pre-reinforcement treatment with fibre-glass bolts to inject grout ahead of the face. In the sections next to the portals corresponding to areas particularly weathered and faults, systematic forepoling is planned with conical canopies of steel pipes above the vault profile, prior to excavation. In all cases, a first lining is planned, consisting of steel arches, shotcrete reinforced with welded mesh or alternatively with Dramix or other type of steel fibres.There will be one single drive in each tunnel. Not only this applies, of course, to the five TBM-driven tunnels which will be bored one after the other but also to each tunnel built by conventional method, since their length is rather short. To date, there is no tunnelling under way in any of the tunnels except the preliminary works to build the portals (retaining walls or rock drilling with bolt and shotcrete reinforcement), all of them well advanced. The first tunnel to commence in October will be the Collecervo tunnel in Andora, using the Herrenknecht TBM.The muck haulage in the TBM-built tunnels will be achieved by conveyor belt to carry the rock intermittently from the face to the portal of each tunnel. For the tunnels constructed with the traditional method, wheel vehicles will be used.Although the concrete segments have been designed to handle a water table of at least 60 metres above the crown, core drills have detected the presence of water only above some tunnels. This water can be explained by temporary and/or seasonal circulation rather than a stable and sustained layer through time. Therefore, the lining gaskets have been designed to resist a 60 m water height above the crown with the aim to avoid systematic drainage in sections where the presence of a true and real water table could be encountered.Because of a zone of contact between the flysh and an underlying chaotic substratum in a stretch of approx. 300 m in the Bardellini tunnel, unstable excavation conditions and ground instability are expected so that reinforcement actions may be required immediately after the passage of the TBM with a view of improving the ground. The Castello tunnel, which will be dug with traditional means entirely in a clayey massif with a maximum coverage of 70-80 m and the presence of private residence buildings above the alignment, also represents a particular challenge. The tunnel will only be bored in reasonable safety conditions if extensive pre-consolidation measures ahead of the face are implemented as well as the constant monitoring of the radial deformations and extrusion of the face.For work in the open air or at the tunnel portals, a Soilmec R-312/200 drilling rig has been employed for the execution of the micropiles and ties of the retaining walls of the portals, a CIFA CSS-2 shotcrete machine has been employed for the shotcreting of the retaining walls and the attacks of the tunnels in rock, CAT 938G loaders have been used for earthworks at the portals, a Komatsu PC210 excavator equipped with hydraulic hammer has demolished a series of private and industrial buildings which existed along the alignment of the railway and a Volvo excavator has been used for soil excavation at the portals. Click it/86. Read E-News Weekly 8/2003. Visit www.rfi.it/files/varie/Andora-SanLorenzo_8.pdf and www.trail.liguria.it/Interventi/Raddoppio_GE-XXmiglia/prima.html 42/05.