Two Mixed Ground Tunnels
completed in San Francisco

A specialized EPB broke through on June 11, 2014, marking the completion of twin tunnels at San Francisco’s Central Subway in California, USA. The first of the two machines holed through on June 2. Both Robbins machines achieved swift advance rates of up to 513 m (1683 ft) in one month. The Central Subway is the second phase of the San Francisco Municipal Transportation Agency’s (SFMTA) Third Street Light Rail Transit Project.

Two 2.5 km (1.5 mi) long tunnels were excavated through ground ranging from soft soils to thinly bedded siltstone, shale and sandstone bedrock, as well as concrete...

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