The first of two TBMs boring towards each other on the first tube of the US$342M, 5.95km long twin-tube Caracas Metro Line 3 in Venezuela has broken through. Contractor, Odebrecht celebrated on 21 July as its 5.88m diameter dual mode Herrenknecht machine entered Line 3’s central reception shaft at Coche having bored the 2,523m stretch from the south westerly La Rinconada Station in one year.

The other TBM, a 5.83m diameter Lovat, driven by Odebrecht’s sub contractor Ghella, is 551m into its 2,339m drive from El Valle Station (to the north east), and is expected at Coche in December 2005 where it will complete Phase 1 of Line 3.

The north-eastern section of the alignment, being bored by the Lovat, runs mostly through the fluvial and alluvial soils of the El Valle River. Towards the south west though, the geology is more mixed and the Herrenknecht has dealt with schist and weathered rock frequently appearing in the face.

The tunnel lining comprises a 5.16m (Herrenknecht drive) – 5.2m (Lovat drive) i.d. pre-cast concrete ring consisting of 6 x 1.4m long segments and a key, with all segments provided from a dedicated plant supplied by Swiss specialist Ceresola.

The project has been split into two phases, the first phase being the forementioned single tube currently under construction. Completion is scheduled for October 2006 after which it will be put into operation.

Phase 2, will consist of the boring of the 4,695m second tube and the construction of the three intermediate stations – Los Jardines, Coche and Mercado. Also included is 426m of NATM tunnel construction.

As the Phase 1 tube will be in operation during Phase 2, the stations will be constructed from the top down. When half of each station platform is completed, the Phase 2 tunnel will be equipped and put into operation whilst the Phase 1 tunnel is demolished to allow completion of the second half of the station platform. Phase 2 is scheduled for completion in July 2008.

Odebrecht was awarded the US$323M contract for Line 3 in September 2002, the cost of tunnelling is estimated to be US$120M. The project is being built for client, C.A. Metro de Caracas, and funded by Brazil’s BNDES bank (US$78M), the French bank Societe Generale (US$37.5M), and Venezuela (US$207.5M).