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Boring unit breaks through solid marble

A contractor has used a Robbins boring machine to construct three tunnels through tough marble in Vermont, US.

Engineers Construction used a 60 inch (1,524 mm) diameter Robbins small boring unit to install three tunnels through marble with 20,000 psi.

The boring forms part of the Vermont Agency of Transportation’s (VTrans) project to replace two nearly 100-year-old rail bridges in the centre of Middlebury, Vermont with a tunnel.

VTrans bridge inspection reports documented the ongoing deterioration of both bridges and, in 2017, after determining an unplanned emergency could cause closure for several months, decided to remove the bridges in favour of a 110 m tunnel.

The two bridges are about 91 m apart, with one located on Main Street/VT 30 and the other on Merchants Row.

Before the Robbins machine was entered into the ground, microtunnelling and utility relocation took place.

The three 46 m long tunnels were completed on line, on grade and on time without any cutter changes.

For more information visit the VTrans website.

If you have a project you would like featured in Trenchless International contact Assistant Editor Chloe Jenkins at cjenkins@gs-press.com.au

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