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Oporto tunnel work set to restart following ground collapse


TUNNELLING WORK on the Oporto metro is due to restart within weeks having been halted in January following a ground collapse in which a woman died.

Since the collapse engineers from Reading-based Jacobs Gibb has been drafted in to act as consultant to client Metro do Oporto.

The project was originally due for completion in 2004.

The collapse of the two storey house between the Campanha and Heroismo districts occurred weeks after the tunnel boring machine (TBM) had passed under the dwelling. There was no structural damage in the completed tunnel bore.

Work stopped with only around 300m of 5.7km bore driven on the £534M design build and operate scheme.

Contractor is the Normetro consortium including Soares de Costa, Adtranz, ABB, SAE, Somague, Impregilo, Transdev and Semaly. Austrian consultant Geoconsult is acting as a subconsultant to the consortium.

Findings from a number of inquiries including a government investigation have not yet been released.

Ground conditions are difficult. Soil is granitic, but ranges from solid granite rock to loose and soft material, with granite content ranging between 50% and 90%.

'There are lots of problems in tunnelling with this type of soil, which can differ greatly over very short distances, ' said Metro do Oporto spokesman Nuno Ortego.

The contractor is using an 8.71m diameter Herrenknecht earth pressure balance TBM.

A new management structure has been imposed before work starts again, bringing closer involvement of the client with the supervision of the work.

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