Drill and blast excavation is advancing through very different geology at each end of the second road tube at Tauern, Austria, being drive by local contractor Porr Tunnelbau.

Work started on site last September and Porr has 26 months to excavate the 6.5km long tunnel through mainly phyllite with a zone of sand and gravel, from weathering and landslides, being cut through at present at the north end.

On the north face, the contractor has designed its own device to adapt an Atlas Copco Rocket Boomer L2C to install liner plates, 220mm wide and 2.5m-3m long, over the crown of the top heading. Up to 70 may be installed.

Depending on the quality of ground the excavation of the heading is proceeding to the basic design of five steps up to 15 in poor conditions. For additional support of the top heading against running ground, Porr is using the boomer to install self-drilling, grouted spiles and anchors 4m long, 32mm diameter.

The north excavation is supported by two layers of shotcrete and mesh, totalling 300mm. Porr has driven more than 400m, advancing the face at just over 2m per 24 hours, but is due to meet rock soon.

That rock is being cut through on the south side by an Atlas Copco Rocket boomer E2, the first of its kind in the Alps. The rig is drilling 120No 49mm diameter holes for blasting, each round advancing the face by 1.7m and there being up to six rounds per 24 hours.

The top heading is 50m2 with a 4m bench 400m behind the face, the invert excavation is farther back again. Immediate face support includes 150mm of shotcrete with a layer of mesh, and other excavation support involves 49mm diameter drill holes to install 4m long cement-grouted rebar anchors/bolts.

Porr has advanced the south face 700m, and breakthrough is anticipated after mid-2008.

The second tube is being built in a US$143M contract after new safety regulations were introduced following a fatal fire in the original, single tube in 1999. The tunnel is to open to traffic in July 2010. Afterwards, the client Austrian road authority ASFINAG will upgrade the original tube.