Also in early April, a 9.5m diameter Lovat EPB machine broke through on the final section of stage 1 of the Metro de Valencia in Venezuela.
Contractor Ghella Sogene broke the TBM, named Beatriz, through to the station on 1 April. The scope of Stage 1 of Line 1 is a 6.2km long single tube, twin track tunnel and seven stations. Beatriz excavated all the bored tunnel sections, totalling 3.8km. There was also 1.6km of cut and cover tunnel; a 0.9km long feeder to the depot and the 0.7km long first commercial leg between stations. Diaphragm walling totalling 0.8km incorporated all the stations that are nominally 120m long and 24m wide to a depth of 20m and contain three levels. The April breakthrough was on a final 640m long section of bored tunnel that had been suspended for nearly two years for “political reasons” when the mayor stopped all contractor activities.
The geology consisted of lake and river sediments, mainly composed of clay and sand layers saturated with water. A source told T&TI that an EPB machine was chosen when problems were encountered excavating the first leg as a cut and cover operation, mainly due to the groundwater table falling within the tunnel section. Other problems that influenced the change in methodology were the lack of information about the position and number of services close to the surface that the TBM could drive below and tall buildings in poor condition within the city centre that the EPB machine was felt to be better able to control settlement for given that cover was only about 10m.
The lining consisted of 1.5m wide, 0.4m thick precast concrete segments. These were installed in rings of seven segments. A daily advance of 10.5m in a single shift was achieved.
Electrowatt Infra oversaw the works for client C.A. Metro de Valencia S.A., with financing provided by the Venezuelan government and Corporación Andina de Fomento. Ghella Sogene’s contract for stage 1 including the stations was roughly US$240M. Of this, US$61M was for the 3.8km of bored tunnel and US$12M for the 0.7km of cut and cover used between the first two stations.
Electrical and mechanical fitting out is ongoing to meet the planned operation date of October 2006. The same TBM is intended to be used for the planned, but not yet financed, stage 2 of Line 1 that is 4km long and includes five stations. The final stage for Line 1, plus Lines 2, 3 and 4 are all in the concept stage.
