Boring resumed last month with the 9.46m diameter EPBM on the running tunnels of São Paulo metro’s Line 4 when it was re-launched from Oscar Freire following a lengthy stop due to works at the station.

The Seli crew driving the shield rapidly got back to achieving the best daily advance rates of 19 rings (28.5m), which has been achieved a few times. Average daily progress in the sandy clay has been 10 rings (15m). Tunnel lining is segmental (7+1) concrete of 8.43 i.d., each ring being 350mm thick and 1.5m long.

So far on the single bore tunnelling project, the best weekly advance has been 90 rings (135m) achieved last September on the drive from Fradique Coutinho to Oscar Freire, which it reached in November 2007.

The Herrenknecht TBM is due to reach the next station, Paulista, by early June. At the station the shield will be dragged through to drive to further stations on the new metro line – Higienópolis-Mackenzie, República and Luz. The shield has less than 4km to bore before terminating at the ventilation shaft at Joao Teodoro, near Luz station, around the middle of next year.

The hole through at Fradique Coutinho was the first for the TBM, which was launched on the 6.4km long tunnel from a box at Faria Lima in February last year. The shield is excavating much of the eastern stretch of the metro line (T&TI, August 2007, p8).

Seli is undertaking the TBM drive on behalf of the Odebrecht-led joint venture contractor Consórcio Via Amarela (CVA). It received the order almost three years ago as a contract package of US$410M (2005 prices).

Geology along the alignment comprises Tertiary silts and sands along with gneiss of the São Paulo and Resende basins.

The World Bank has approved a US$95M loan to São Paulo for the Line 4 expansion project. The loan has a term of 25 years following a five-year Grace period.

TBM at Oscar Freire station on Line 4 of Sao Paulo metro before relaunch TBM at Oscar Freire station on Line 4 of Sao Paulo metro before relaunch