Two Hitachi ZX350LC-7 excavators equipped with clamshell telescopic arms (CTA) are being utilised on an important infrastructure project in the centre of Vienna. The special application machines, which can remove soil from several metres below ground level, were selected by the U2 17-21 consortium to work on the city’s metro expansion project. The aim is to extend the U2 line between Matzleinsdorfer Platz and Neubaugasse, which started in February 2021 and is due to be completed in 2028.

The subway is continually expanding in line with the city’s growth and this project is an important step towards reducing CO₂ emissions from Vienna’s transportation network and enhancing mobility for residents and visitors. The U2 17-21 consortium, made up of companies Strabag and PORR, won the contract to build four new stations and three emergency exits on the U2 line for around €480 million. Additional work worth about €49 million was added later.

The project involves moving millions of cubic metres of soil from depths of 30 metres, bringing it up to five metres above ground level. The Hitachi ZX350-7 CTA was selected thanks to its precision and quick cycle time, which is estimated to be 45 seconds. This is significantly faster than the cycle time of a rope or crane excavator.

“The achievable depth of 32 metres [including a two-metre local extension] was essential to our decision when selecting the ZX350-7 CTA excavators,” says Project Manager Michael Stoifl. “The 1.5m³ ISO clamshell bucket size was also an important factor. In my opinion, it is a reliable and efficient machine.”

In addition, special measures are required to prevent surface movements during the excavation. The enhanced hydraulics of the ZX350LC-7 CTA, combined with the arm’s high-speed extension and retraction, and the powerful pull-up force results in smooth and efficient operation.

“Hitachi is the only manufacturer to design and build excavators with deep-digging  telescopic arms in-house,” says Burkhard Janssen, HCME European Department Head of Special Application Machines & New Technologies. “The Zaxis-7 models share the same industry-leading technology as standard Hitachi excavators, and are the optimum solution for complex below-ground construction projects. They offer high levels of productivity, a powerful performance and exceptional versatility.”

* Published with permission from ‘Arge U2 17-21’ and Strabag/PORR